Herboxidiene antibody-drug conjugates and methods of use

Abstract

Linker-drug compounds and antibody-drug conjugates that bind to human oncology targets are disclosed. The linker-drug compounds and antibody-drug conjugates comprise a herboxidiene splicing modulator drug moiety. The disclosure further relates to methods and compositions for use in the treatment of neoplastic disorders by administering the antibody-drug conjugates provided herein.

Description

HERBOXIDIENE SPLICING MODULATOR ANTIBODY-DRUGCONJUGATES AND METHODS OF USE

[0001] The present disclosure claims the benefit of priority to U.S. Provisional PatentApplication No. 62 / 779,400, filed December 13, 2018; U.S. Provisional ApplicationNo. 62 / 779,406, filed December 13, 2018; and U.S. Provisional Application No. 62 / 941 ,220, filed November 27, 2019. All of the aforementioned applications are incorporated herein by reference in their entirety.

[0002] The present disclosure relates to antibody-drug conjugates (ADCs) comprising a herboxidiene splicing modulator and an antibody or antigen binding fragment thereof, e.g., one that binds a human oncology antigen target. The disclosure further relates to methods and compositions useful in the treatment or diagnosis of cancers that express a target antigen and / or are amenable to treatment by disruption of RNA splicing, as well as methods of making those compositions.

[0003] The majority of protein-coding genes in the human genome are composed of multiple exons (coding regions) that are separated by introns (non-coding regions). Gene expression results in a single precursor messenger RNA (pre-mRNA). The intron sequences are subsequently removed from the pre-mRNA by a process called splicing, which results in the mature messenger RNA (mRNA). By including different combinations of exons, alternative splicing gives rise to mRNAs encoding distinct protein isoforms.

[0004] RNA splicing is catalyzed by the spliceosome, a dynamic multiprotein-RNA complex composed of five small nuclear RNAs (snRNAs U1 , U2, U4, U5, and U6) and associated proteins. The spliceosome assembles on pre-mRNAs to establish a dynamic cascade of multiple RNA and protein interactions that catalyze excision of the introns and ligation of exons (Matera and Wang (2014) Nat Rev Mol Cell Biol. 15(2): 108-21). Accumulating evidence has linked human diseases to dysregulation in RNA splicing that impact many genes (Scotti and Swanson (2016) Nat Rev Genet. 17(1 ): 19-32).

[0005] The spliceosome is an important target in cancer biology. Several studies have now documented significant alterations in the splicing profile of cancer cells, as well as in the splicing factors themselves (Agrawal et al. (2018) Curr Opin Genet Dev. 48:67-74). Alternative splicing can lead to differential exon inclusion / exclusion, intron retention, or usage of cryptic splice sites (Seiler et al. (2018) Cell Rep. 23(1):282-296). Altogether, these events account for functional changes that may contribute to tumorigenesis or resistance to therapy (Siegfried and Kami (2018) Curr Opin Genet Dev. 48:16-21).

[0006] Certain natural products can bind the SF3b spliceosome complex. These small molecules modulate splicing by promoting intron retention and / or exon skipping (Teng et al. (2017) Nat Commun. 8:15522). For example, herboxidiene, a naturally occurring polyketide isolated from Streptomyces sp. A7847 (Isaac et al. (1992) J. Org. Chem. 57:7220-26) andderivatives of the same have been shown to modulate splicing. See, e.g., Imaizumi et al.(2017) J. Antibiot. 70:675-79. A significant portion of the resulting transcripts contain premature stop codons triggering nonsense mediated mRNA decay (NMD). Furthermore, because canonical splicing is impaired, canonical transcripts are considerably reduced, which can negatively impact cell function and viability. For this reason, splicing modulators have become a promising class of drugs for the treatment of cancer (Puthenveetil et al. (2016) Bioconjugate Chem. 27:1880-8).

[0007] The proto-oncogene human epidermal growth factor receptor 2 ( HER2 ) encodes a transmembrane tyrosine kinase receptor that belongs to the human epidermal growth factor receptor (EGFR) family (King et al. (1985) Science 229:974-6). Overexpression of HER2 enables constitutive activation of growth factor signaling pathways, such as the PI3K-AKT- mTOR pathway, and thereby serves as an oncogenic driver in several types of cancers, including approximately 20% of invasive breast carcinomas (Slamon et al. (1989) Science 244:707-12; Gajria and Chandarlapaty (2011) Expert Rev Anticancer Ther. 11 :263-75). Given that HER2 amplification mediates the transformed phenotype, and because HER2 expression is largely restricted to malignant cells, HER2 is a promising antigen for targeting certain cancers and / or delivering novel cancer treatments (Parakh et al. (2017) Cancer Treat Rev. 59:1-21). Additional antigens for targeted delivery of cancer therapies include, but are not limited to, CD138 (also referred to as syndecan-1) and ephrin type-A receptor 2 (EPHA2).

[0008] CD138 is a cell surface heparan sulfate proteoglycan that is essential for maintaining cell morphology and interaction with the surrounding microenvironment (Akl et al. (2015) Oncotarget 6(30):28693-715; Szatmari et al. (2015) Dis Markers 2015:796052). In general, the loss of CD138 expression in carcinoma cells reduces cell adhesion to the extracellular matrix and enhances cell motility and invasion (Teng et al. (2012) Matrix Biol. 31 :3-16). Increased stromal CD138 expression also alters fibronectin production and extracellular matrix organization (Yang et al. (2011) Am J Pathol. 178:325-35). Additionally, increased expression of CD138 in stromal fibroblasts is associated with angiogenesis and cancer progression (Maeda et al. (2006) Oncogene 25:1408-12). CD138 expression increases during B cell development and its presence is a hallmark of plasma cells (Ribatti (2017) Immunol Lett. 188:64-7). CD138 expression is maintained in multiple myeloma, a malignancy of plasma cells. CD138 is therefore an attractive antigen for the targeted treatment of several cancers and other hematological malignancies (Sherbenou et al. (2015) Blood Rev. 29(2):81-91 ; Wijdenes et al. (1996) Br J Haematol. 94(2):318-23).

[0009] EPHA2 is a transmembrane glycoprotein that is abundantly overexpressed in several malignant cancer-derived cell lines and in advanced forms of cancer (Wykosky and Debinski (2008) Mol Cancer Ref. 6(12):1795-1806). For instance, EPHA2 is strongly overexpressed in approximately 61 % of GBM patient tumors (Wykosky et al. (2008) Clin Cancer Res. 14:199-208), 76% of ovarian cancers (Thaker et al. (2004) Clin Cancer Res. 10:5145-50), and 85% ofprostate adenocarcinomas (Zeng et al. (2003) Am J Pathol. 163:2271-6). The EPHA2 protein is highly overexpressed with regard to percentage of patient tumors and percentage of cells within a tumor, and is a plasma membrane-localized receptor that can internalize on ligand binding (Walker-Daniels et al. (2002) Mol Cancer Res. 1 :79-87). Moreover, expression of EPHA2 is associated with poor prognosis, increased metastasis, and decreased survival. Thus, due to its expression pattern, localization, and functional importance in the outcome of cancer patients, EPHA2 is another attractive antigen for the targeted delivery of novel anti-cancer therapies.

[0010] In various embodiments, the present disclosure provides, in part, novel herboxidiene splicing modulators with biological activity against neoplastic cells. The herboxidiene splicing modulators may be used alone or as part of ADCs to slow, inhibit, and / or reverse tumor growth in mammals, and may be useful for treating human cancer patients. In various embodiments, the disclosure provides novel antibody-drug conjugates employing the herboxidiene splicing modulators

[0011] The present disclosure more specifically relates, in various embodiments, to antibody- drug conjugate (ADC) compounds that are capable of binding and killing neoplastic cells. In various embodiments, the ADC compounds disclosed herein comprise a linker that attaches a herboxidiene splicing modulator to a full-length antibody or an antigen binding fragment. In various embodiments, the ADC compounds are also capable of internalizing into a target cell after binding.

[0012] In some embodiments, the antibody-drug conjugate is an antibody-drug conjugate of Formula (I): Ab-(L-H)p, wherein Ab is an antibody or antigen binding fragment which targets a neoplastic cell; H is a herboxidiene splicing modulator; L is a linker which covalently attaches Ab to H; and p is an integer from 1 to 15.

[0013] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formulapharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:Y is chosen from O, S, NR6, and CR6R7;R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R4is chosen from hydrogen, C1-C6 alkyl groups, -C(=0)-(Ci-C6alkyl) groups, -C(=0)- (C3-C8 carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, and -C(=0)-NR6R7;R5is chosen from hydrogen, hydroxyl, -CH2-OH, -CO2H, -C(=0)-0-(Ci-C6alkyl) groups, -C(=0)-NR6R7, -NR6-C(=0)-R8, -0-C(=0)-NR6R7, -NR6-C(=0)-R8, and -NR6-C(=0)-NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)- O-R8; andR8is chosen from C1-C6alkyl groups, C3-C8carbocyclyl groups, and C3-C8heterocyclyl groups,wherein R1, R2, R3, R4, R5, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6alkyl groups, -0-(Ci-C6alkyl) groups, -C02H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6alkylalkoxy groups, benzyl groups, and C3-C8heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1-C3alkyl groups, C1-C3 alkoxy groups, C1-C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl), andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0014] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (la):pharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:R9is chosen from C3-C8heterocyclyl groups;R10is chosen from H and C1-C6alkyl groups,wherein R9and R10are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C3alkyl groups, C1-C3alkoxy groups, -NH2, -NH-(CI-C3alkyl), and -N-(CI-C3alkyl)2, andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0015] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formulapharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:R11is chosen fromwherein denotes the point of connectivity of R11to the remainder of the compound;R12and R13are each independently chosen from H and methyl; andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0016] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (II):(II), or a pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:X is hydroxyl or NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, -C(=0)-0-R8, -(CrCe alkyl)-0-C(=0)-R8, and -(Ci-C6alkyl)-NH-C(=0)-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, CrCe alkyl groups, -0-(CrCe alkyl) groups, - CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(CrCe alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, C1-C6 alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3alkyl), and -NH-C(=0)-0-(CrC3alkyl), andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0017] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (I la):la), or apharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:Z is chosen from NR9and O;R9is chosen from hydrogen and C1-C6 alkyl groups;R10and R11are each independently chosen from hydrogen, halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-Ce alkyl) groups, -CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, C3-C8 carbocyclyl groups, C1-C6 alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups;R12is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, C3-C8 heterocyclyl groups,wherein R9, R10, R11, and R12are each independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, and C1 -C3 haloalkyl groups;t is an integer chosen from 1 , 2, 3, 4, 5, and 6; andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0018] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (lib):(lib), or a pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:point of connectivity of R13to the remainder of the compound;R14and R15are each independently chosen from hydrogen and methyl; andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0019] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formulapharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)-O-R8;R8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups; andwherein R1, R2, R3, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl),wherein the valency of the atom that is covalently attached to L is not exceeded; and wherein * denotes the point of connectivity of R9to the remainder of the compound.

[0020] In some embodiments, the linker comprises a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety is cleavable by an enzyme. In some embodiments,the cleavable peptide moiety or linker comprises an amino acid unit. In some embodiments, the amino acid unit comprises valine-citrulline (“Val-Cit” or“VC”). In some other embodiments, the amino acid unit comprises valine-alanine (“Val-Ala” or“VA”). In some other embodiments, the amino acid unit comprises glutamic acid-valine-citrulline (“Glu-Val-Cit” or“EVC”). In some other embodiments, the amino acid unit comprises alanine-alanine-asparagine (“Ala-Ala-Asn” or “AAN”).

[0021] In some embodiments, the linker comprises a cleavable glucuronide moiety. In some embodiments, the cleavable glucuronide moiety is cleavable by an enzyme. In some embodiments, the cleavable glucuronide moiety is cleavable by a glucuronidase. In some embodiments, the cleavable glucuronide moiety is cleavable by b-glucuronidase.

[0022] In some embodiments, the linker comprises at least one spacer unit. In some embodiments, the spacer unit or linker comprises a polyethylene glycol (PEG) moiety. In some embodiments, the PEG moiety comprises -(PEG)m- and m is an integer from 1 to 10. In some embodiments, m is 2. In some other embodiments, the spacer unit or linker comprises an alkyl moiety. In some embodiments, the alkyl moiety comprises -(CH2) / r and n is an integer from 1 to 10. In some embodiments, n is 2. In some embodiments, n is 5. In some embodiments, n is 6.

[0023] In some embodiments, the spacer unit attaches to the antibody or antigen binding fragment via a maleimide (Mai) moiety (“Mal-spacer unit”). In some embodiments, the Mal- spacer unit is reactive with a cysteine residue on the antibody or antigen binding fragment. In some embodiments, the Mal-spacer unit is joined to the antibody or antigen binding fragment via a cysteine residue on the antibody or antigen binding fragment.

[0024] In some embodiments, the linker comprises the Mal-spacer unit and a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the cleavable peptide moiety or amino acid unit comprises Val-Cit. In some embodiments, the cleavable peptide moiety or amino acid unit comprises Val-Ala. In some embodiments, the cleavable peptide moiety or amino acid unit comprises Glu-Val-Cit. In some embodiments, the cleavable peptide moiety or amino acid unit comprises Ala-Ala-Asn. In some embodiments, the Mal-spacer unit comprises an alkyl moiety. In some embodiments, the Mal-spacer unit comprises a PEG moiety. In some embodiments, the Mal-spacer unit comprises a maleimidocaproyl (MC).

[0025] In some embodiments, the Mal-spacer unit attaches the antibody or antigen binding fragment to the cleavable moiety in the linker. In some embodiments, the cleavable moiety in the linker comprises a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn. In some embodiments, the linker comprises MC-Val-Cit. In some embodiments, the linker comprises MC-Val-Ala. In some embodiments, the linker comprises MC-Glu-Val-Cit. In some embodiments, the linker comprises MC-Ala-Ala-Asn. In some embodiments, the Mal-spacer unit comprises an alkylmoiety. In some embodiments, the Mal-spacer unit comprises a PEG moiety. In some embodiments, the Mal-spacer unit comprises a maleimidocaproyl (MC).

[0026] In some embodiments, the cleavable moiety in the linker is directly joined to the herboxidiene splicing modulator, or a spacer unit attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, cleavage of the conjugate releases the herboxidiene splicing modulator from the antibody or antigen binding fragment and linker. In some embodiments, the spacer unit attaching the cleavable moiety in the linker to the herboxidiene splicing modulator is self-immolative.

[0027] In some embodiments, the spacer unit attaching the cleavable moiety in the linker to the herboxidiene splicing modulator comprises a p-aminobenzyloxycarbonyl (pABC). In some embodiments, the pABC attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, the cleavable moiety in the linker comprises a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn. In some embodiments, the linker comprises Val-Cit-pABC. In some other embodiments, the linker comprises Val-Ala-pABC. In some embodiments, the linker comprises Glu-Val-Cit-pABC. In some embodiments, the linker comprises Ala-Ala-Asn- pABC.

[0028] In some embodiments, the spacer unit attaching the cleavable moiety in the linker to the herboxidiene splicing modulator comprises a p-aminobenzyl (pAB). In some embodiments, the pAB attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, the cleavable moiety in the linker comprises a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In someembodiments, the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu- Val-Cit, or Ala-Ala-Asn. In some embodiments, the linker comprises Val-Cit-pAB. In some other embodiments, the linker comprises Val-Ala-pAB. In some other embodiments, the linker comprises Glu-Val-Cit-pAB. In some other embodiments, the linker comprises Ala-Ala-Asn- pAB.

[0029] In various embodiments, the linker is a non-cleavable linker. In some embodiments, the herboxidiene splicing modulator of the ADC is released by degradation of the antibody or antigen binding fragment. In some embodiments, the linker remains covalently associated with at least one amino acid of the antibody and drug upon internalization by and degradation within the target cell.

[0030] In some embodiments, the linker is a non-cleavable linker comprising at least one spacer unit. In some embodiments, the spacer unit or linker comprises a polyethylene glycol (PEG) moiety. In some embodiments, the PEG moiety comprises -(PEG)m- and m is an integer from 1 to 10. In some embodiments, m is 2. In some other embodiments, the spacer unit or linker comprises an alkyl moiety. In some embodiments, the alkyl moiety comprises -(Chhjn- or-(CH2)n-0-(CH2)nand n is an integer from 1 to 10. In some embodiments, n is 2. In some embodiments, n is 5. In some embodiments, n is 6.

[0031] In some embodiments, the spacer unit in a non-cleavable linker attaches to the antibody or antigen binding fragment via a maleimide (Mai) moiety (“Mal-spacer unit”). In some embodiments, the Mal-spacer unit is reactive with a cysteine residue on the antibody or antigen binding fragment. In some embodiments, the Mal-spacer unit is joined to the antibody or antigen binding fragment via a cysteine residue on the antibody or antigen binding fragment. In some embodiments, the Mal-spacer unit comprises an alkyl moiety. In some embodiments, the Mal-spacer unit comprises a PEG moiety. In some embodiments, the linker or Mal-spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker or Mal-spacer unit comprises a maleimidocaproyl (MC) and at least one additional spacer unit. In some embodiments, the linker or Mal-spacer unit comprises MC-(PEG)2. In some embodiments, the linker or Mal-spacer unit comprises MC-(PEG)2and at least one additional spacer unit. In some embodiments, the linker or Mal-spacer unit comprises Mai-Hex. In some embodiments, the linker or Mal-spacer unit comprises Mai-Hex and at least one additional spacer unit. In some embodiments, the linker or Mal-spacer unit comprises Mal-Et. In some embodiments, the linker or Mal-spacer unit comprises Mal-Et and at least one additional spacer unit. In some embodiments, the linker or Mal-spacer unit comprises Mal-Et-O-Et. In some embodiments, the linker or Mal-spacer unit comprises Mal-Et-O-Et and at least one additional spacer unit. In some embodiments, the Mal-spacer unit attaches the antibody or antigen binding fragment to the herboxidiene splicing modulator.

[0032] In some embodiments, Ab is selected from any of the antibody or binding domain sequences disclosed herein. In some embodiments, Ab is an antibody or binding domain sequence which targets HER2 and / or a HER2-expressing neoplastic cell. In someembodiments, Ab is an antibody or binding domain sequence which targets CD138 and / or a CD138-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets EPHA2 and / or an EPHA2-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets MSLN and / or a MSLN-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets FOLH1 and / or a FOLH1 -expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets CDH6 and / or a CDH6-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets CEACAM5 and / or a CEACAM5-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets CFC1 B and / or a CFC1 B-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets ENPP3 and / or an ENPP3-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets FOLR1 and / or aFOLR1 -expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domainsequence which targets HAVCR1 and / or a HAVCR1 -expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets KIT and / or a KIT- expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets MET and / or a MET-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets MUC16 and / or a MUC16- expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets SLC39A6 and / or a SLC39A6-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets SLC44A4 and / or a SLC44A4-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets STEAP1 and / or a STEAPI-expressing neoplastic cell. In some embodiments, Ab is an antibody or binding domain sequence which targets another cancer antigen.

[0033] In some embodiments, L is selected from any of the linkers disclosed herein, or any combination of linker components disclosed herein. In some embodiments, L is a linker comprising MC-Val-Cit-pABC, Mal-(PEG)2-CO, MC-Val-Ala-pAB, MC-Val-Ala-pABC, MC-Val- Cit-pAB, Mai-Hex, Mal-Et, or Mal-Et-O-Et. In some embodiments, the linker may also comprise one or more additional spacer units. In some embodiments, L is an ADL1 , ADL2, ADL5, ADL6, ADL7, ADL10, ADL12, ADL13, ADL14, ADL15, ADL21 , ADL22, or ADL23 linker. In some embodiments, L is an ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15,ADL21 , or ADL23 linker. In some embodiments, L is an ADL12, ADL14, or ADL15 linker. In some embodiments, the ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker may also comprise one or more additional spacer units. In some embodiments, L is an ADL1 linker and may optionally comprise one or more additional spacer units. In some embodiments, L is an ADL2 linker and may optionally comprise one or more additional spacer units. In some embodiments, L is an ADL5 linker and may optionally comprise one or more additional spacer units. In some embodiments, L is an ADL6 linker and may optionally comprise one or more additional spacer units. In some embodiments, L is an ADL7 linker and may optionally comprise one or more additional spacer units. In some embodiments, L is an ADL12 linker and may optionally comprise one or more additional spacer units. In some embodiments, L is an ADL14 linker and may optionally comprise one or more additional spacer units. In some embodiments, L is an ADL15 linker and may optionally comprise one or more additional spacer units. In various embodiments of the ADCs described herein, p is from 1 to 10. In various embodiments, p is from 2 to 8. In various embodiments, p is from 4 to 8. In some embodiments, p is 4. In some embodiments, p is 8.

[0034] In some embodiments, a pool of ADCs is provided whereby random conjugation occurs, and the average p in the pool is between about 2 and about 8. In some embodiments, a pool of ADCs is provided whereby random conjugation occurs, and the average p in the pool is between about 4 and about 8. In some embodiments, a pool of ADCs is provided wherebyrandom conjugation occurs, and the average p in the pool is about 4. In some embodiments, a pool of ADCs is provided whereby random conjugation occurs, and the average p in the pool is about 8. Compositions (e.g., pharmaceutical compositions) comprising multiple copies of any of the described ADCs, wherein the average drug loading (average p) of the ADCs in the composition is from about 3.5 to about 5.5 (e.g., about 4), or from about 7 to about 9 (e.g., about 8) are provided herein.

[0035] In some embodiments, the antibody or antigen binding fragment (Ab) of the ADC targets a neoplastic cell derived from a hematological malignancy or a solid tumor. In someembodiments, the antibody or antigen binding fragment targets a neoplastic cell derived from a hematological malignancy. In some embodiments, the hematological malignancy is selected from a B-cell malignancy, a leukemia (e.g., acute myeloid leukemia), a lymphoma, and a myeloma (e.g., multiple myeloma). In some embodiments, the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma. In some embodiments, the antibody or antigen binding fragment targets a neoplastic cell derived from a solid tumor. In some embodiments, the solid tumor is selected from breast cancer (e.g., HER2-positive breast cancer), gastric cancer (e.g., gastric adenocarcinoma), prostate cancer, ovarian cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer. In some embodiments, the solid tumor is selected from HER2-positive breast cancer, gastric adenocarcinoma, prostate cancer, and osteosarcoma.

[0036] In various embodiments, the antibody or antigen binding fragment (Ab) of the ADC is an anti-HER2 antibody or an antigen binding fragment thereof. In some embodiments, the antibody or antigen binding fragment binds to HER2 and targets HER2-expressing neoplastic cells (i.e. , the ADC targets HER2-expressing neoplastic cells). In some embodiments, the antibody or antigen binding fragment of the ADC is an internalizing anti-HER2 antibody or internalizing antigen binding fragment thereof.

[0037] In some embodiments, the anti-HER2 antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO:2 (HCDR2), and SEQ ID NO:3 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO:4 (LCDR1), SEQ ID NO:5 (LCDR2), and SEQ ID NO:6 (LCDR3). In some embodiments, the anti-HER2 antibody or antigen binding fragment is an internalizing antibody or internalizing antigen binding fragment.In some embodiments, the anti-HER2 antibody or antigen binding fragment comprises human framework sequences. In some embodiments, the anti-HER2 antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQID NO: 19, and a light chain variable region comprising an amino acid sequence of SEQ IDNO:20. In some embodiments, the anti-HER2 antibody or antigen binding fragment comprises a human IgG heavy chain constant region. In some embodiments, the anti-HER2 antibody or antigen binding fragment comprises a human lgG1 heavy chain constant region. In some embodiments, the anti-HER2 antibody or antigen binding fragment comprises a human Ig kappa or lambda light chain constant region. In some embodiments, the anti-HER2 antibody or antigen binding competes for binding and / or binds the same epitope as an antibody comprising a heavy chain variable domain of SEQ ID NO: 19 and a light chain variable domain of SEQ ID NO:20.

[0038] In various embodiments, the antibody or antigen binding fragment (Ab) of the ADC is an anti-CD138 antibody or an antigen binding fragment thereof. In some embodiments, the antibody or antigen binding fragment binds to CD138 and targets CD138-expressing neoplastic cells (i.e. , the ADC targets CD138-expressing neoplastic cells). In some embodiments, the antibody or antigen binding fragment of the ADC is an internalizing anti-CD138 antibody or internalizing antigen binding fragment thereof.

[0039] In some embodiments, the anti-CD138 antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEC ID NO:7 (HCDR1), SEC ID NO:8 (HCDR2), and SEC ID NO:9 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEC ID NO:10 (LCDR1), SEC ID NO: 11 (LCDR2), and SEC ID NO:12 (LCDR3). In some embodiments, the anti-CD138 antibody or antigen binding fragment is an internalizing antibody or internalizing antigen binding fragment. In some embodiments, the anti-CD138 antibody or antigen binding fragment comprises human framework sequences. In some embodiments, the anti-CD138 antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEC ID NO:21 , and a light chain variable region comprising an amino acid sequence of SEC ID NO:22. In some embodiments, the anti-CD138 antibody or antigen binding fragment comprises a murine lgG2a heavy chain constant region. In someembodiments, the anti-CD138 antibody or antigen binding fragment comprises a murine Ig kappa light chain constant region. In some embodiments, the anti-CD138 antibody or antigen binding fragment comprises a human IgG heavy chain constant region. In some embodiments, the anti-CD138 antibody or antigen binding fragment comprises a human lgG2a heavy chain constant region. In some embodiments, the anti-CD138 antibody or antigen binding fragment comprises a human Ig kappa or lambda light chain constant region. In some embodiments, the anti-CD138 antibody or antigen binding competes for binding and / or binds the same epitope as an antibody comprising a heavy chain variable domain of SEQ ID NO:21 and a light chain variable domain of SEQ ID NO:22.

[0040] In various embodiments, the antibody or antigen binding fragment (Ab) of the ADC is an anti-EPHA2 antibody or an antigen binding fragment thereof. In some embodiments, theantibody or antigen binding fragment binds to EPHA2 and targets EPHA2-expressing neoplastic cells (i.e., the ADC targets EPHA2-expressing neoplastic cells). In some embodiments, the antibody or antigen binding fragment of the ADC is an internalizing anti-EPHA2 antibody or internalizing antigen binding fragment thereof.

[0041] In some embodiments, the anti-EPHA2 antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO:13 (HCDR1), SEQ ID NO:14 (HCDR2), and SEQ ID NO: 15 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO:16 (LCDR1), SEQ ID NO: 17 (LCDR2), and SEQ ID NO:18 (LCDR3). In some embodiments, the anti-EPHA2 antibody or antigen binding fragment is an internalizing antibody or internalizing antigen binding fragment. In some embodiments, the anti-EPHA2 antibody or antigen binding fragment comprises human framework sequences. In some embodiments, the anti-EPHA2 antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:23, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:24. In some embodiments, the anti-EPHA2 antibody or antigen binding fragment comprises a human IgG heavy chain constant region. In some embodiments, the anti-EPHA2 antibody or antigen binding fragment comprises a human lgG1 heavy chain constant region. In some embodiments, the anti-EPHA2 antibody or antigen binding fragment comprises a human Ig kappa or lambda light chain constant region. In some embodiments, the anti-EPHA2 antibody or antigen binding competes for binding and / or binds the same epitope as an antibody comprising a heavy chain variable domain of SEQ ID NO:23 and a light chain variable domain of SEQ ID NO:24.

[0042] In some embodiments, disclosed herein, are compounds of Formula (I):pharmaceutically acceptable salt thereof, wherein:Y is chosen from O, S, NR6, and CR6R7;R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R4is chosen from hydrogen, C1-C6 alkyl groups, -C(=0)-(Ci-C6alkyl) groups, -C(=0)- (C3-C8 carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, and -C(=0)-NR6R7;R5is chosen from hydrogen, hydroxyl, -CH2-OH, -CO2H, -C(=0)-0-(Ci-C6alkyl) groups, -C(=0)-NR6R7, -NR6-C(=0)-R8, -0-C(=0)-NR6R7, -NR6-C(=0)-R8, and -NR6-C(=0)-NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)- O-R8; andR8is chosen from C1-C6alkyl groups, C3-C8carbocyclyl groups, and C3-C8heterocyclyl groups,wherein R1, R2, R3, R4, R5, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6alkyl groups, -0-(Ci-C6alkyl) groups, -C02H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6alkylalkoxy groups, benzyl groups, and C3-C8heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1-C3alkyl groups, C1-C3 alkoxy groups, C1-C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl).

[0043] In some embodiments, provided herein are compounds of Formula (la):pharmaceutically acceptable salt thereof, wherein:R9is chosen from C3-C8heterocyclyl groups; andR10is chosen from H and C1-C6alkyl groups,wherein R9and R10are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C3alkyl groups, C1-C3alkoxy groups, -NH2, -NH-(CI-C3alkyl), and -N-(CI-C3alkyl)2.

[0044] In some embodiments, provided herein are compounds of Formula (lb):pharmaceutically acceptable salt thereof, wherein:R11is chosen fromwherein denotes the point of connectivity of R11to the remainder of the compound; andR12and R13are each independently chosen from H and methyl.

[0045] In some embodiments, provided herein are compounds of Formula (II):(II), or a pharmaceutically acceptable salt thereof, wherein:X is NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, -C(=0)-0-R8, -(Ci-C6alkyl)-0-C(=0)-R8, and -(Ci-C6alkyl)-NH-C(=0)-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R6, R7, and R8are each independently substituted with 0 to 3 groupsindependently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl).

[0046] In some embodiments, provided herein are compounds of Formula (I la):I la), or a pharmaceutically acceptable salt thereof, wherein:Z is chosen from NR9and O;R9is chosen from hydrogen and C1-C6 alkyl groups;R10and R11are each independently chosen from hydrogen, halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-Ce alkyl) groups, -CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups;R12is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, C3-C8 heterocyclyl groups,wherein R9, R10, R11, and R12are each independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, and C1 -C3 haloalkyl groups; andt is an integer chosen from 1 , 2, 3, 4, 5, and 6.

[0047] In some embodiments, provided herein are compounds of Formula (lib):(lib), or a pharmaceutically acceptable salt thereof, wherein:wherein * denotes the point of connectivity of R13to the remainder of the compound; andR14and R15are each independently chosen from hydrogen and methyl.

[0048] In some embodiments, provided herein are compounds of Formula (III):pharmaceutically acceptable salt thereof, wherein:R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-Ce alkyl) groups, -0-C(=0)-(Ci-C6 alkyl) groups, -C(=0)-0-(Ci-C6 alkyl) groups, and CrCe alkyl groups;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)-O-R8;R8is chosen from CrCe alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups; andwherein R1, R2, R3, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl); andwherein * denotes the point of connectivity of R9to the remainder of the compound.

[0049] In some embodiments, provided herein is a compound chosen from:and pharmaceutically acceptable salts thereof,wherein L is a linker which covalently attaches to an antibody.

[0050] Also, in various embodiments, provided herein are therapeutic uses for the described ADC compounds, herboxidiene compounds, and compositions, e.g., in treating a neoplastic disorder, e.g., a cancer. In certain aspects, the present disclosure provides methods of treating a neoplastic disorder, e.g., a cancer that expresses an antigen targeted by the antibody or antigen binding fragment of the ADC, such as HER2, CD138, EPHA2, MSLN, FOLH1 , CDH6, CEACAM5, CFC1 B, ENPP3, FOLR1 , HAVCR1 , KIT, MET, MUC16, SLC39A6, SLC44A4, or STEAP1.

[0051] In certain aspects, the present disclosure provides methods of treating a subject having or suspected of having a neoplastic disorder by administering to the subject a therapeutically effective amount and / or regimen of any one of the described ADCs or compositions. In some embodiments, the neoplastic disorder is a hematological malignancy or a solid tumor. In some embodiments, the neoplastic disorder is a hematological malignancy. In some embodiments,the hematological malignancy is selected from a B-cell malignancy, a leukemia, a lymphoma, and a myeloma. In some embodiments, the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma. In some embodiments, the neoplastic disorder is a solid tumor. In some embodiments, the solid tumor is selected from breast cancer (e.g., HER2- positive breast cancer), gastric cancer (e.g., gastric adenocarcinoma), prostate cancer, ovarian cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer. In some embodiments, the solid tumor is selected from HER2-positive breast cancer, gastricadenocarcinoma, prostate cancer, and osteosarcoma.

[0052] In some embodiments, treatment with the antibody-drug conjugate or composition induces bystander killing of neoplastic cells which do not express a target antigen but are adjacent to neoplastic cells which express a target antigen. In some embodiments, the subject has one or more neoplastic cells which express a target antigen.

[0053] In some embodiments, the target antigen is HER2. In some embodiments, the one or more neoplastic cells are in a HER2-expressing breast cancer, ovarian cancer, gastric cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), osteosarcoma, or salivary duct carcinoma. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-HER2 antibody when administered alone and / or (b) a herboxidiene splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a herboxidiene splicing modulator when administered alone.

[0054] In some embodiments, the target antigen is CD138. In some embodiments, the one or more neoplastic cells are in a CD138-expressing multiple myeloma. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-CD138 antibody when administered alone and / or (b) a herboxidiene splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a herboxidiene splicing modulator when administered alone.

[0055] In some embodiments, the target antigen is EPHA2. In some embodiments, the one or more neoplastic cells are in an EPHA2-expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-EPHA2 antibody when administered alone and / or (b) a herboxidiene splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a herboxidiene splicing modulator when administered alone.

[0056] In some embodiments, the target antigen is MSLN. In some embodiments, the one or more neoplastic cells are in a MSLN-expressing ovarian cancer, cervical cancer, pancreatic cancer, or lung cancer (e.g., lung adenocarcinoma). In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-MSLN antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0057] In some embodiments, the target antigen is FOLH1. In some embodiments, the one or more neoplastic cells are in a FOLH1-expressing prostate cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-FOLH1 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0058] In some embodiments, the target antigen is CDH6. In some embodiments, the one or more neoplastic cells are in a CDH6-expressing kidney cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-CDH6 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0059] In some embodiments, the target antigen is CEACAM5. In some embodiments, the one or more neoplastic cells are in a CEACAM5-expressing colorectal cancer. In someembodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti- CEACAM5 antibody when administered alone and / or (b) a splicing modulator whenadministered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0060] In some embodiments, the target antigen is CFC1 B. In some embodiments, the one or more neoplastic cells are in a CFC1 B-expressing pancreatic cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-CFC1 B antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0061] In some embodiments, the target antigen is ENPP3. In some embodiments, the one or more neoplastic cells are in an ENPP3-expressing kidney cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-ENPP3 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0062] In some embodiments, the target antigen is FOLR1. In some embodiments, the one or more neoplastic cells are in a FOLR1-expressing ovarian cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-FOLR1 antibody when administered alone and / or (b) a splicing modulator when administered alone. In someembodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0063] In some embodiments, the target antigen is HAVCR1. In some embodiments, the one or more neoplastic cells are in a HAVCRI-expressing kidney cancer or esophageal cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-HAVCR1 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0064] In some embodiments, the target antigen is KIT. In some embodiments, the one or more neoplastic cells are in a KIT-expressing kidney cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-KIT antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0065] In some embodiments, the target antigen is MET. In some embodiments, the one or more neoplastic cells are in a MET-expressing kidney cancer or esophageal cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti- MET antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0066] In some embodiments, the target antigen is MUC16. In some embodiments, the one or more neoplastic cells are in a MUC16-expressing ovarian cancer, cervical cancer, or breast cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-MUC16 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0067] In some embodiments, the target antigen is SLC39A6. In some embodiments, the one or more neoplastic cells are in a SLC39A6-expressing breast cancer or prostate cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-SLC39A6 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0068] In some embodiments, the target antigen is SLC44A4. In some embodiments, the one or more neoplastic cells are in a SLC44A4-expressing prostate cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-SLC44A4 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0069] In some embodiments, the target antigen is STEAP1. In some embodiments, the one or more neoplastic cells are in a STEAPI-expressing prostate cancer. In some embodiments, the subject is non-responsive or poorly responsive to treatment with (a) an anti-STEAP1 antibody when administered alone and / or (b) a splicing modulator when administered alone. In some embodiments, the subject is intolerant, non-responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

[0070] In certain other aspects, the present disclosure provides methods of reducing or inhibiting growth of a tumor in a subject having or suspected of having a neoplastic disorder by administering to the subject a therapeutically effective amount and / or regimen of any one of the described ADCs or compositions.

[0071] In some embodiments, treatment with the antibody-drug conjugate or composition induces bystander killing of neoplastic tumor cells which do not express a target antigen but are adjacent to neoplastic tumor cells which express a target antigen. In some embodiments, the tumor comprises one or more neoplastic cells which express a target antigen.

[0072] In some embodiments, the target antigen is HER2. In some embodiments, the one or more neoplastic cells are derived from a HER2-expressing breast cancer, ovarian cancer, gastric cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), osteosarcoma, or salivary duct carcinoma. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-HER2 antibody when administered alone and / or (b) a herboxidiene splicing modulator when administered alone.

[0073] In some embodiments, the target antigen is CD138. In some embodiments, the one or more neoplastic cells are derived from a CD138-expressing multiple myeloma. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-CD138 antibody when administered alone and / or (b) a herboxidiene splicing modulator when administered alone.

[0074] In some embodiments, the target antigen is EPHA2. In some embodiments, the one or more neoplastic cells are derived from an EPHA2-expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-EPHA2 antibody when administered alone and / or (b) a herboxidiene splicing modulator when administered alone.

[0075] In some embodiments, the target antigen is MSLN. In some embodiments, the one or more neoplastic cells are derived from a MSLN-expressing ovarian cancer, cervical cancer, pancreatic cancer, or lung cancer (e.g., lung adenocarcinoma). In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-MSLN antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0076] In some embodiments, the target antigen is FOLH1. In some embodiments, the one or more neoplastic cells are derived from a FOLH1 -expressing prostate cancer. In someembodiments, the tumor is resistant or refractory to treatment with (a) an anti-FOLH1 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0077] In some embodiments, the target antigen is CDH6. In some embodiments, the one or more neoplastic cells are derived from a CDH6-expressing kidney cancer. In someembodiments, the tumor is resistant or refractory to treatment with (a) an anti-CDH6 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0078] In some embodiments, the target antigen is CEACAM5. In some embodiments, the one or more neoplastic cells are derived from a CEACAM5-expressing colorectal cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-CEACAM5 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0079] In some embodiments, the target antigen is CFC1 B. In some embodiments, the one or more neoplastic cells are derived from a CFC1 B-expressing pancreatic cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-CFC1 B antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0080] In some embodiments, the target antigen is ENPP3. In some embodiments, the one or more neoplastic cells are derived from an ENPP3-expressing kidney cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-ENPP3 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0081] In some embodiments, the target antigen is FOLR1. In some embodiments, the one or more neoplastic cells are derived from a FOLR1-expressing ovarian cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-FOLR1 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0082] In some embodiments, the target antigen is HAVCR1. In some embodiments, the one or more neoplastic cells are derived from a HAVCRI-expressing kidney cancer or esophageal cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti- HAVCR1 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0083] In some embodiments, the target antigen is KIT. In some embodiments, the one or more neoplastic cells are derived from a KIT-expressing kidney cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-KIT antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0084] In some embodiments, the target antigen is MET. In some embodiments, the one or more neoplastic cells are derived from a MET-expressing kidney cancer or esophageal cancer.In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-MET antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0085] In some embodiments, the target antigen is MUC16. In some embodiments, the one or more neoplastic cells are derived from a MUC16-expressing ovarian cancer, cervical cancer, or breast cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a)an anti-MUC16 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0086] In some embodiments, the target antigen is SLC39A6. In some embodiments, the one or more neoplastic cells are derived from a SLC39A6-expressing breast cancer or prostate cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti- SLC39A6 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0087] In some embodiments, the target antigen is SLC44A4. In some embodiments, the one or more neoplastic cells are derived from a SLC44A4-expressing prostate cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-SLC44A4 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0088] In some embodiments, the target antigen is STEAP1. In some embodiments, the one or more neoplastic cells are derived from a STEAPI-expressing prostate cancer. In some embodiments, the tumor is resistant or refractory to treatment with (a) an anti-STEAP1 antibody when administered alone and / or (b) a splicing modulator when administered alone.

[0089] In still other aspects, the present disclosure provides methods of determining whether a subject having or suspected of having a neoplastic disorder will be responsive to treatment with any one of the described ADCs or compositions by providing a biological sample from the subject and contacting the biological sample with the ADC or composition. In someembodiments, the biological sample is a tumor sample. In some embodiments, the tumor sample is a tumor biopsy or blood sample. In some embodiments, the blood sample is selected from blood, a blood fraction, or a cell obtained from the blood or blood fraction. In some embodiments, the subject has one or more neoplastic cells which express a target antigen. In some embodiments, the target antigen is HER2. In some embodiments, the one or more neoplastic cells are derived from a HER2-expressing breast cancer, ovarian cancer, gastric cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), osteosarcoma, or salivary duct carcinoma. In some embodiments, the target antigen is CD138. In some embodiments, the one or more neoplastic cells are derived from a CD138-expressing multiple myeloma. In some embodiments, the target antigen is EPHA2. In some embodiments, the one or more neoplastic cells are derived from an EPHA2- expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer. In some embodiments, the target antigen is MSLN. In some embodiments, the one or more neoplastic cells are derived from a MSLN-expressing ovarian cancer, cervical cancer, pancreatic cancer, or lung cancer (e.g., lung adenocarcinoma). In some embodiments, the target antigen is FOLH1. In some embodiments, the one or more neoplastic cells are derived from a FOLH1 -expressing prostate cancer. In some embodiments, the target antigen is CDH6. In some embodiments, the one or more neoplastic cells are derived from a CDH6-expressing kidney cancer. In some embodiments, the target antigen isCEACAM5. In some embodiments, the one or more neoplastic cells are derived from aCEACAM5-expressing colorectal cancer. In some embodiments, the target antigen is CFC1 B.In some embodiments, the one or more neoplastic cells are derived from a CFC1 B-expressing pancreatic cancer. In some embodiments, the target antigen is ENPP3. In some embodiments, the one or more neoplastic cells are derived from an ENPP3-expressing kidney cancer. In some embodiments, the target antigen is FOLR1. In some embodiments, the one or more neoplastic cells are derived from a FOLR1 -expressing ovarian cancer. In some embodiments, the target antigen is HAVCR1. In some embodiments, the one or more neoplastic cells are derived from a HAVCR1 -expressing kidney cancer or esophageal cancer. In someembodiments, the target antigen is KIT. In some embodiments, the one or more neoplastic cells are derived from a KIT-expressing kidney cancer. In some embodiments, the target antigen is MET. In some embodiments, the one or more neoplastic cells are derived from a MET- expressing kidney cancer or esophageal cancer. In some embodiments, the target antigen is MUC16. In some embodiments, the one or more neoplastic cells are derived from a MUC16- expressing ovarian cancer, cervical cancer, or breast cancer. In some embodiments, the target antigen is SLC39A6. In some embodiments, the one or more neoplastic cells are derived from a SLC39A6-expressing breast cancer or prostate cancer. In some embodiments, the target antigen is SLC44A4. In some embodiments, the one or more neoplastic cells are derived from a SLC44A4-expressing prostate cancer. In some embodiments, the target antigen is STEAP1.In some embodiments, the one or more neoplastic cells are derived from a STEAP1 -expressing prostate cancer.

[0090] Further provided herein, in various embodiments, are pharmaceutical compositions comprising an ADC and a pharmaceutically acceptable diluent, carrier, and / or excipient.Methods of producing the described ADC compounds and compositions are also disclosed.BRIEF DESCRIPTION OF THE DRAWINGS

[0091] FIG. 1 A-1 D show viability dose responses of exemplary payload compounds in HER2- amplified breast cancer cells (HCC1954) and gastric cancer cells (NCI-N87). Cells were incubated with compound for 72 hours (3 days) or 144 hours (6 days) and viability was read in CellTiter-Glo® 2.0 reagent. FIG. 1A shows the viability dose response in HCC1954 cells following a 72-hour incubation. FIG. 1 B shows the viability dose response in NCI-N87 cells following a 72-hour incubation. FIG. 1C shows the viability dose response in HCC1954 cells following a 144-hour incubation. FIG. 1D shows the viability dose response in NCI-N87 cells following a 144-hour incubation. Data are represented as mean ± SD.

[0092] FIG. 2A and FIG. 2B show the results of a SLC25A19 splicing assay in HER2-amplified breast cancer cells (HCC1954) (FIG. 2A) and gastric cancer cells (NCI-N87) (FIG. 2B). Cells were incubated with compounds for 6 hours and splicing of SLC25A19 transcript was measuredin a real time qPCR reaction with a specific Taqman primer-probe set. The y-axis represents the percent (%) response relative to a DMSO control (0.1%). Data are represented as mean ± SD.DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0093] The disclosed compositions and methods may be understood more readily by reference to the following detailed description.

[0094] Throughout this text, the descriptions refer to compositions and methods of using the compositions. Where the disclosure describes or claims a feature or embodiment associated with a composition, such a feature or embodiment is equally applicable to the methods of using the composition. Likewise, where the disclosure describes or claims a feature or embodiment associated with a method of using a composition, such a feature or embodiment is equally applicable to the composition.

[0095] When a range of values is expressed, it includes embodiments using any particular value within the range. Further, reference to values stated in ranges includes each and every value within that range. All ranges are inclusive of their endpoints and combinable. When values are expressed as approximations, by use of the antecedent“about,” it will be understood that the particular value forms another embodiment. Reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. The use of “or” will mean“and / or” unless the specific context of its use dictates otherwise.

[0096] It is to be appreciated that certain features of the disclosed compositions and methods, which are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosed compositions and methods that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.

[0097] All references cited herein are incorporated by reference for any purpose. Where a reference and the specification conflict, the specification will control.Definitions

[0098] Various terms relating to aspects of the description are used throughout the specification and claims. Such terms are to be given their ordinary meaning in the art unless otherwise indicated. Other specifically defined terms are to be construed in a manner consistent with the definitions provided herein.

[0099] As used herein, the singular forms“a,”“an,” and“the” include plural forms unless the context clearly dictates otherwise.

[0100] The terms "about" or "approximately" in the context of numerical values and ranges refers to values or ranges that approximate or are close to the recited values or ranges such that the embodiment may perform as intended, such as having a desired amount of nucleicacids or polypeptides in a reaction mixture, as is apparent to the skilled person from the teachings contained herein. In some embodiments, about means plus or minus 10% of a numerical amount.

[0101] The terms“antibody-drug conjugate,”“antibody conjugate,”“conjugate,”“immunoconjugate,” and“ADC” are used interchangeably, and refer to one or more therapeutic compounds (e.g., a herboxidiene splicing modulator) that is linked to one or more antibodies or antigen binding fragments and is defined by the generic formula: Ab-(L-H)p(Formula I), wherein Ab = an antibody or antigen binding fragment, L = a linker moiety, H = a herboxidiene splicing modulator (e.g., herboxidiene or derivative thereof), and p = the number of drug moieties per antibody or antigen binding fragment. An ADC comprising a herboxidiene splicing modulator may also be referred to herein more specifically as a“herboxidiene splicing modulator-loaded antibody” or a“SMLA.” In ADCs comprising a herboxidiene splicing modulator,“p” refers to the number of herboxidiene splicing modulators linked to the antibody or antigen binding fragment. In some embodiments, the linker L can include a cleavable moiety between the antibody or antigen binding fragment and the herboxidiene splicing modulator. In some embodiments, the linker L can include a cleavable moiety that can be attached to either or both the antibody or antigen binding fragment and herboxidiene splicing modulator by spacer unit(s). In some embodiments, when a spacer unit attaches the cleavable moiety to the herboxidiene splicing modulator, it is a self-immolative spacer unit. In other embodiments, the linker L does not include a cleavable moiety, and is a non-cleavable linker. In some embodiments, the linker L can include at least one spacer unit that can directly attach to the antibody or antigen binding fragment and to the herboxidiene splicing modulator. Exemplary cleavable and non-cleavable linkers are described and exemplified herein.

[0102] The term "antibody" is used in the broadest sense to refer to an immunoglobulin molecule that recognizes and specifically binds to a target, such as a protein, polypeptide, carbohydrate, polynucleotide, lipid, or combinations of the foregoing through at least one antigen recognition site within the variable region of the immunoglobulin molecule. The heavy chain of an antibody is composed of a heavy chain variable domain (VH) and a heavy chain constant region (CH). The light chain is composed of a light chain variable domain (VL) and a light chain constant domain (CL). For the purposes of this application, the mature heavy chain and light chain variable domains each comprise three complementarity determining regions (CDR1 , CDR2 and CDR3) within four framework regions (FR1 , FR2, FR3, and FR4) arranged from N-terminus to C-terminus: FR1 , CDR1 , FR2, CDR2, FR3, CDR3, and FR4. An "antibody" can be naturally occurring or man-made, such as monoclonal antibodies produced by conventional hybridoma technology. The term“antibody” includes full-length monoclonal antibodies and full-length polyclonal antibodies, as well as antibody fragments such as Fab, Fab’, F(ab’)2, Fv, and single chain antibodies. An antibody can be any one of the five major classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM, or subclasses thereof (e.g., isotypeslgG1 , lgG2, lgG3, lgG4). The term further encompasses human antibodies, chimeric antibodies, humanized antibodies and any modified immunoglobulin molecule containing an antigen recognition site, so long as it demonstrates the desired biological activity (e.g., binds the target antigen, internalizes within a target-antigen expressing cell).

[0103] The term "monoclonal antibody," as used herein, refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e. , the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic epitope. In contrast, conventional (polyclonal) antibody preparations typically include a multitude of antibodies directed against (or specific for) different epitopes. The modifier "monoclonal" indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present disclosure may be made by the hybridoma method first described by Kohler et al. (1975) Nature 256:495, or may be made by recombinant DNA methods (see, e.g., U.S. Pat. No. 4,816,567). Monoclonal antibodies may also be isolated from phage antibody libraries using the techniques described in Clackson et al. (1991) Nature 352:624-8, and Marks et al. (1991) J Mol Biol. 222:581-97, for example.

[0104] The monoclonal antibodies described herein specifically include "chimeric" antibodies, in which a portion of the heavy and / or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they specifically bind the target antigen and / or exhibit the desired biological activity.

[0105] The term“human antibody,” as used herein, refers an antibody produced by a human or an antibody having an amino acid sequence of an antibody produced by a human.

[0106] The term“chimeric antibody,” as used herein, refers to antibodies wherein the amino acid sequence of the immunoglobulin molecule is derived from two or more species. In some instances, the variable regions of both heavy and light chains correspond to the variable regions of antibodies derived from one species with the desired specificity, affinity, and activity while the constant regions are homologous to antibodies derived from another species (e.g., human) to minimize an immune response in the latter species.

[0107] As used herein, the term "humanized antibody" refers to forms of antibodies that contain sequences from non-human (e.g., murine) antibodies as well as human antibodies. Such antibodies are chimeric antibodies which contain minimal sequence derived from non-human immunoglobulin. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the hypervariableloops correspond to those of a non-human immunoglobulin and all or substantially all of the framework (FR) regions are those of a human immunoglobulin sequence. The humanized antibody optionally also will comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin. The humanized antibody can be further modified by the substitution of residues, either in the Fv framework region and / or within the replaced non-human residues to refine and optimize antibody specificity, affinity, and / or activity.

[0108] The term "antigen binding fragment" or "antigen binding portion" of an antibody, as used herein, refers to one or more fragments of an antibody or protein that retain the ability to specifically bind to an antigen (e.g., HER2, CD138, EPHA2, MSLN, FOLH1 , CDH6, CEACAM5, CFC1 B, ENPP3, FOLR1 , HAVCR1 , KIT, MET, MUC16, SLC39A6, SLC44A4, or STEAPI). Antigen binding fragments may also retain the ability to internalize into an antigen-expressing cell. In some embodiments, antigen binding fragments also retain immune effector activity. It has been shown that fragments of a full-length antibody can perform the antigen binding function of a full-length antibody. Examples of binding fragments encompassed within the term "antigen binding fragment" or "antigen binding portion" of an antibody include (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL, and Cm domains; (ii) a F(ab')2fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting of the VHand Cm domains; (iv) a Fv fragment consisting of the VLand VHdomains of a single arm of an antibody; (v) a dAb fragment, which comprises a single variable domain, e.g., a VHdomain (see, e.g., Ward et al. (1989) Nature 341 :544-6; and Inti.Pub. No. WO 1990 / 005144); and (vi) an isolated complementarity determining region (CDR). Furthermore, although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VLand VHregions pair to form monovalent molecules (known as single chain Fv (scFv)). See, e.g., Bird et al. (1988) Science 242:423-6; and Huston et al. (1988) Proc Natl Acad Sci. USA 85:5879-83. Such single chain antibodies are also intended to be encompassed within the term "antigen binding fragment" or "antigen binding portion" of an antibody, and are known in the art as an exemplary type of binding fragment that can internalize into cells upon binding (see, e.g., Zhu et al. (2010) 9:2131- 41 ; He et al. (2010) J Nucl Med. 51:427-32; and Fitting et al. (2015) MAbs 7:390-402). In certain embodiments, scFv molecules may be incorporated into a fusion protein. Other forms of single chain antibodies, such as diabodies are also encompassed. Diabodies are bivalent, bispecific antibodies in which VHand VLdomains are expressed on a single polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with complementary domains of another chain and creating two antigen binding sites (see e.g., Holliger et al. (1993) Proc Natl Acad Sci. USA 90:6444-8; and Poljak et al. (1994) Structure 2:1121-3). Antigen binding fragments are obtained using conventional techniques known to those of skill in the art, and the bindingfragments are screened for utility (e.g., binding affinity, internalization) in the same manner as are intact antibodies. Antigen binding fragments may be prepared by cleavage of the intact protein, e.g., by protease or chemical cleavage.

[0109] “Internalizing” as used herein in reference to an antibody or antigen binding fragment refers to an antibody or antigen binding fragment that is capable of being taken through the cell’s lipid bilayer membrane to an internal compartment (i.e. ,“internalized”) upon binding to the cell, preferably into a degradative compartment in the cell. For example, an internalizing anti-IH ER2 antibody is one that is capable of being taken into the cell after binding to FIER2 on the cell membrane. In some embodiments, the antibody or antigen binding fragment used in the ADCs disclosed herein targets a cell surface antigen (e.g., FIER2) and is an internalizing antibody or internalizing antigen binding fragment (i.e., the ADC transfers through the cellular membrane after antigen binding). In some embodiments, the internalizing antibody or antigen binding fragment binds a receptor on the cell surface. An internalizing antibody or internalizing antigen binding fragment that targets a receptor on the cell membrane may induce receptor- mediated endocytosis. In some embodiments, the internalizing antibody or internalizing antigen binding fragment is taken into the cell via receptor-mediated endocytosis.

[0110] “Non-internalizing” as used herein in reference to an antibody or antigen binding fragment refers to an antibody or antigen binding fragment that remains at the cell surface upon binding to the cell. In some embodiments, the antibody or antigen binding fragment used in the ADCs disclosed herein targets a cell surface antigen and is a non-internalizing antibody or non internalizing antigen binding fragment (i.e., the ADC remains at the cell surface and does not transfer through the cellular membrane after antigen binding). In some embodiments, the non internalizing antibody or antigen binding fragment binds a non-internalizing receptor or other cell surface antigen. Exemplary non-internalizing cell surface antigens include but are not limited to CA125 and CEA, and antibodies that bind to non-internalizing antigen targets are also known in the art (see, e.g., Bast et al. (1981) J Clin Invest. 68(5): 1331— 7; Scholler and Urban (2007) Biomark Med. 1 (4):513—23; and Boudousq et al. (2013) PLoS One 8(7):e69613).

[0111] The term“human epidermal growth factor receptor 2,”“FIER2,” or“FIER2 / NEU,” as used herein, refers to any native form of human FIER2. The term encompasses full-length FIER2 (e.g., UniProt Reference Sequence: P04626; SEQ ID NO:31), as well as any form of human FIER2 that may result from cellular processing. The term also encompasses functional variants or fragments of human FIER2, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human FIER2 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). FIER2 can be isolated from human, or may be produced recombinantly or by synthetic methods.

[0112] The term“anti-FIER2 antibody” or“antibody that binds to FIER2” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to FIER2, and encompassesmonoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to HER2. U.S. Pat. No. 5,821 ,337 provides and is incorporated herein by reference for exemplary HER2- binding sequences, including exemplary anti-HER2 antibody sequences. In someembodiments, the anti-HER2 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment. Trastuzumab (U.S. Pat. No. 5,821 ,337; Molina et al. (2001) Cancer Res. 61 (12):4744-9) is an exemplary anti-human HER2 antibody.

[0113] The term“syndecan-1 ,”“SDC1 ,” or“CD138,” as used herein, refers to any native form of human CD138. The term encompasses full-length CD138 (e.g., UniProt Reference Sequence: P18827; SEQ ID NO:32), as well as any form of human CD138 that may result from cellular processing. The term also encompasses functional variants or fragments of human CD138, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human CD138 (i.e. , variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). CD138 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0114] The term "anti-CD138 antibody" or“antibody that binds to CD138” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to CD138, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to CD138. In some embodiments, the anti-CD138 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment. B-B4 (Tassone et al. (2004) Blood 104:3688-96) is an exemplary anti-human CD138 antibody.

[0115] The term“ephrin type-A receptor 2” or“EPHA2,” as used herein, refers to any native form of human EPHA2. The term encompasses full-length EPHA2 (e.g., UniProt Reference Sequence: P29317; SEQ ID NO:33), as well as any form of human EPHA2 that may result from cellular processing. The term also encompasses functional variants or fragments of human EPHA2, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human EPHA2 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). EPHA2 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0116] The term "anti-EPHA2 antibody" or“antibody that binds to EPHA2” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to EPHA2, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to EPHA2. WO 2007 / 030642 provides and is incorporated herein by reference for exemplary EPHA2- binding sequences, including exemplary anti-EPHA2 antibody sequences. In someembodiments, the anti-EPHA2 antibody used in the ADCs disclosed herein is an internalizingantibody or internalizing antibody fragment. 1C1 (WO 2007 / 030642; Jackson et al. (2008) Cancer Res. 68(22): 9367-74) is an exemplary anti-human EPHA2 antibody.

[0117] The term“mesothelin” or“MSLN,” as used herein, refers to any native form of human MSLN. The term encompasses full-length MSLN (e.g., UniProt Reference Sequence: Q13421 ; SEQ ID NO:94), as well as any form of human MSLN that may result from cellular processing. The term also encompasses functional variants or fragments of human MSLN, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human MSLN (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). MSLN can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0118] The term "anti-MSLN antibody" or“antibody that binds to MSLN” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to MSLN, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to MSLN. WO 2011 / 074621 provides and is incorporated herein by reference for exemplary MSLN- binding sequences, including exemplary anti-MSLN antibody sequences. In someembodiments, the anti-MSLN antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment. 11-25, IC14-30, IC7-4, IC17-35 and 2-9 are exemplary anti-human MSLN antibodies.

[0119] The term“glutamate carboxypeptidase 2” or“FOLH1 ,” as used herein, refers to any native form of human FOLH1. The term encompasses full-length FOLH1 (e.g., UniProtReference Sequence: Q04609; SEQ ID NO:95), as well as any form of human FOLH1 that may result from cellular processing. The term also encompasses functional variants or fragments of human FOLH1 , including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human FOLH1 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). FOLH1 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0120] The term "anti-FOLH1 antibody" or“antibody that binds to FOLH1” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to FOLH1 , and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to FOLH1. WO 2019 / 012260 and WO 2017 / 212250 provide and are incorporated herein by reference for exemplary FOLFU-binding sequences, including exemplary anti-FOLH1 antibody sequences. In some embodiments, the anti-FOLH1 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment. J591 (deimmunized) is an exemplary anti-human FOLH1 antibody.

[0121] The term“cadherin-6” or“CDH6,” as used herein, refers to any native form of human CDH6. The term encompasses full-length CDH6 (e.g., UniProt Reference Sequence: P55285; SEQ ID NO:96), as well as any form of human CDH6 that may result from cellular processing. The term also encompasses functional variants or fragments of human CDH6, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human CDH6 (i.e. , variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). CDH6 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0122] The term "anti-CDH6 antibody" or“antibody that binds to CDH6” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to CDH6, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to CDH6. WO 2018 / 185618 provides and is incorporated herein by reference for exemplary CDH6-binding sequences, including exemplary anti-CDH6 antibody sequences. In some embodiments, the anti-CDH6 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0123] The term“carcinoembryonic antigen-related cell adhesion molecule 5” or“CEACAM5,” as used herein, refers to any native form of human CEACAM5. The term encompasses full- length CEACAM5 (e.g., UniProt Reference Sequence: P06731 ; SEQ ID NO:97), as well as any form of human CEACAM5 that may result from cellular processing. The term alsoencompasses functional variants or fragments of human CEACAM5, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human CEACAM5 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). CEACAM5 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0124] The term "anti-CEACAM5 antibody" or“antibody that binds to CEACAM5” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to CEACAM5, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to CEACAM5. US 2015 / 0125386 provides and is incorporated herein by reference for exemplary CEACAM5-binding sequences, including exemplary anti-CEACAM5 antibody sequences. In some embodiments, the anti-CEACAM5 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment. hMN14 is an exemplary anti-human CEACAM5 antibody.

[0125] The term“cryptic family protein 1 B” or“CFC1 B,” as used herein, refers to any native form of human CFC1 B. The term encompasses full-length CFC1 B (e.g., UniProt Reference Sequence: P0CG36; SEQ ID NO:98), as well as any form of human CFC1 B that may result from cellular processing. The term also encompasses functional variants or fragments ofhuman CFC1 B, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human CFC1 B (i.e. , variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). CFC1 B can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0126] The term "anti-CFC1 B antibody" or“antibody that binds to CFC1 B” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to CFC1 B, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to CFC1 B. WO 2002 / 088170 provides and is incorporated herein by reference for exemplary CFC1 B- binding sequences, including exemplary anti-CFC1 B antibody sequences. In someembodiments, the anti-CFC1 B antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0127] The term“ectonucleotide pyrophosphatase / phosphodiesterase family member 3” or “ENPP3,” as used herein, refers to any native form of human ENPP3. The term encompasses full-length ENPP3 (e.g., UniProt Reference Sequence: 014638; SEQ ID NO:99), as well as any form of human ENPP3 that may result from cellular processing. The term also encompasses functional variants or fragments of human ENPP3, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human ENPP3(i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). ENPP3 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0128] The term "anti-ENPP3 antibody" or“antibody that binds to ENPP3” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to ENPP3, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to ENPP3. Donate et al. ((2016) Clin Cancer Res. 22(8): 1989-99) provides and is incorporated herein by reference for exemplary ENPP3-binding sequences, including exemplary anti-ENPP3 antibody sequences. In some embodiments, the anti-ENPP3 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0129] The term“folate receptor alpha” or“FOLR1 ,” as used herein, refers to any native form of human FOLR1. The term encompasses full-length FOLR1 (e.g., UniProt Reference Sequence: P15328; SEQ ID NO:100), as well as any form of human FOLR1 that may result from cellular processing. The term also encompasses functional variants or fragments of human FOLR1 , including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human FOLR1 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). FOLR1 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0130] The term "anti-FOLR1 antibody" or“antibody that binds to FOLR1” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to FOLR1 , and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to FOLR1. WO 2005 / 080431 and Coney et al. ((1991) Cancer Res. 51(22):6125-32) provide and are incorporated herein by reference for exemplary FOLR1 -binding sequences, including exemplary anti-FOLR1 antibody sequences. In some embodiments, the anti-FOLR1 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.Farletuzumab and MOv19 are exemplary anti-human FOLR1 antibodies.

[0131] The term“hepatitis A virus cellular receptor 1” or“HAVCR1 ,” as used herein, refers to any native form of human HAVCR1. The term encompasses full-length HAVCR1 (e.g., UniProt Reference Sequence: G96D42; SEC ID NO: 101), as well as any form of human HAVCR1 that may result from cellular processing. The term also encompasses functional variants or fragments of human HAVCR1 , including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human HAVCR1 (i.e. , variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). HAVCR1 can be isolated from a human, or may be producedrecombinantly or by synthetic methods.

[0132] The term "anti-HAVCR1 antibody" or“antibody that binds to HAVCR1” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to HAVCR1 , andencompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to HAVCR1. Thomas et al. ((2016) Mol Cancer Ther. 15(12):2946-54) provides and is incorporated herein by reference for exemplary HAVCR1 -binding sequences, including exemplary anti-HAVCR1 antibody sequences. In some embodiments, the anti-HAVCR1 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0133] The term“mast / stem cell growth factor receptor Kit” or“KIT,” as used herein, refers to any native form of human KIT. The term encompasses full-length KIT (e.g., UniProt Reference Sequence: P10721 ; SEC ID NO:102), as well as any form of human KIT that may result from cellular processing. The term also encompasses functional variants or fragments of human KIT, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human KIT (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). KIT can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0134] The term "anti-KIT antibody" or“antibody that binds to KIT” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to KIT, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, andbiologically functional antibody fragments so long as they bind, e.g., specifically bind, to KIT.Shi et al. ((2016) Proc Natl Acad Sci USA 113(33):E4784-93) and Abrams et al. ((2018) Clin Cancer Res. 24(17):4297-308) provide and are incorporated herein by reference for exemplary KIT-binding sequences, including exemplary anti-KIT antibody sequences. In someembodiments, the anti-KIT antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0135] The term“hepatocyte growth factor receptor” or“MET,” as used herein, refers to any native form of human MET. The term encompasses full-length MET (e.g., UniProt Reference Sequence: P08581 ; SEQ ID NO: 103), as well as any form of human MET that may result from cellular processing. The term also encompasses functional variants or fragments of human MET, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human MET (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). MET can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0136] The term "anti-MET antibody" or“antibody that binds to MET” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to MET, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to MET. Yang et al. ((2019) Acta Pharmacol Sin.) provides and is incorporated herein by reference for exemplary MET-binding sequences, including exemplary anti-MET antibody sequences. In some embodiments, the anti-MET antibody used in the ADCs disclosed herein is aninternalizing antibody or internalizing antibody fragment.

[0137] The term“mucin-16” or“MUC16,” as used herein, refers to any native form of human MUC16. The term encompasses full-length MUC16 (e.g., UniProt Reference Sequence:Q8WXI7; SEQ ID NO:104), as well as any form of human MUC16 that may result from cellular processing. The term also encompasses functional variants or fragments of human MUC16, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human MUC16 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). MUC16 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0138] The term "anti-MUC16 antibody" or“antibody that binds to MUC16” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to MUC16, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to MUC16. Liu et al. ((2016) Ann Oncol. 27(11):2124-30) provides and is incorporated herein by reference for exemplary MUC16-binding sequences, including exemplary anti-MUC16 antibody sequences. In some embodiments, the anti-MUC16 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0139] The term“zinc transporter ZIP6” or“SLC39A6,” as used herein, refers to any native form of human SLC39A6. The term encompasses full-length SLC39A6 (e.g., UniProt Reference Sequence:Q13433; SEQ ID NO:105), as well as any form of human SLC39A6 that may result from cellular processing. The term also encompasses functional variants or fragments of human SLC39A6, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human SLC39A6 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). SLC39A6 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0140] The term "anti-SLC39A6 antibody" or“antibody that binds to SLC39A6” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to SLC39A6, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to SLC39A6. Sussman et al. ((2014) Mol Cancer Ther. 13(12):2991-3000) provides and is incorporated herein by reference for exemplary SLC39A6-binding sequences, including exemplary anti-SLC39A6 antibody sequences. In some embodiments, the anti-SLC39A6 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0141] The term“choline transporter-like protein 4” or“SLC44A4,” as used herein, refers to any native form of human SLC44A4. The term encompasses full-length SLC44A4 (e.g., UniProt Reference Sequence: Q53GD3; SEQ ID NO: 106), as well as any form of human SLC44A4 that may result from cellular processing. The term also encompasses functional variants or fragments of human SLC44A4, including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human SLC44A4 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). SLC44A4 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0142] The term "anti-SLC44A4 antibody" or“antibody that binds to SLC44A4” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to SLC44A4, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to SLC44A4. Mattie et al. ((2016) Mol Cancer Ther. 15(11):2679-87) provides and is incorporated herein by reference for exemplary SLC44A4-binding sequences, including exemplary anti-SLC44A4 antibody sequences. In some embodiments, the anti-SLC44A4 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0143] The term“metalloreductase STEAP1” or“STEAP1 ,” as used herein, refers to any native form of human STEAP1. The term encompasses full-length STEAP1 (e.g., UniProt ReferenceSequence: Q9UHE8; SEQ ID NO: 107), as well as any form of human STEAP1 that may result from cellular processing. The term also encompasses functional variants or fragments of human STEAP1 , including but not limited to splice variants, allelic variants, and isoforms that retain one or more biologic functions of human STEAP1 (i.e., variants and fragments are encompassed unless the context indicates that the term is used to refer to the wild-type protein only). STEAP1 can be isolated from a human, or may be produced recombinantly or by synthetic methods.

[0144] The term "anti-STEAP1 antibody" or“antibody that binds to STEAP1” refers to any form of antibody or fragment thereof that binds, e.g., specifically binds, to STEAP1 , andencompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they bind, e.g., specifically bind, to STEAP1. WO 2008 / 052187 provides and is incorporated herein by reference for exemplary STEAP1 -binding sequences, including exemplary anti-STEAP1 antibody sequences. In some embodiments, the anti-STEAP1 antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.

[0145] As used herein, the term "specific," "specifically binds," and "binds specifically" refers to a binding reaction between an antibody or antigen binding fragment (e.g., an anti-HER2 antibody) and a target antigen (e.g., HER2) in a heterogeneous population of proteins and other biologies. Antibodies can be tested for specificity of binding by comparing binding to an appropriate antigen to binding to an irrelevant antigen or antigen mixture under a given set of conditions. If the antibody binds to the appropriate antigen with at least 2, 5, 7, and preferably 10 or more times more affinity than to the irrelevant antigen or antigen mixture, then it is considered to be specific. A“specific antibody” or a“target-specific antibody” is one that only binds the target antigen (e.g., HER2), but does not bind (or exhibits minimal binding) to other antigens. In certain embodiments, an antibody or antigen binding fragment that specifically binds a target antigen (e.g., HER2) has a KD of less than 1x10-6M, less than 1x107M, less than 1x108M, less than 1x10-9M, less than 1x1010M, less than 1x10-11M, less than 1x10-12M, or less than 1x10-13M. In certain embodiments, the KD is 1 pM to 500 pM. In some embodiments, the KDis between 500 pM to 1 mM, 1 mM to 100 nM, or 100 mM to 10 nM.

[0146] The term“epitope” refers to the portion of an antigen capable of being recognized and specifically bound by an antibody. When the antigen is a polypeptide, epitopes can be formed from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of the polypeptide. The epitope bound by an antibody may be identified using any epitope mapping technique known in the art, including X-ray crystallography for epitope identification by direct visualization of the antigen-antibody complex, as well as monitoring the binding of the antibody to fragments or mutated variations of the antigen, or monitoring solvent accessibility of different parts of the antibody and the antigen. Exemplary strategies used to map antibody epitopes include, but are not limited to, array-based oligo-peptide scanning, limited proteolysis, site-directed mutagenesis, high-throughput mutagenesis mapping, hydrogen-deuterium exchange, and mass spectrometry (see, e.g., Gershoni et al. (2007) 21 : 145-56; and Hager-Braun and Tomer (2005) Expert Rev Proteomics 2:745-56).

[0147] Competitive binding and epitope binning can also be used to determine antibodies sharing identical or overlapping epitopes. Competitive binding can be evaluated using a cross blocking assay, such as the assay described in“Antibodies, A Laboratory Manual,” Cold Spring Harbor Laboratory, Harlow and Lane (1stedition 1988, 2ndedition 2014). In some embodiments, competitive binding is identified when a test antibody or binding protein reduces binding of a reference antibody or binding protein to a target antigen such as HER2 (e.g., a binding protein comprising CDRs and / or variable domains selected from those identified in Tables 2-4), by at least about 50% in the cross-blocking assay (e.g., 50%, 60%, 70%, 80%, 90%, 95%, 99%, 99.5%, or more, or any percentage in between), and / or vice versa. In some embodiments, competitive binding can be due to shared or similar (e.g., partially overlapping) epitopes, or due to steric hindrance where antibodies or binding proteins bind at nearby epitopes (see, e.g., Tzartos, Methods in Molecular Biology (Morris, ed. (1998) vol. 66, pp. 55-66)). In some embodiments, competitive binding can be used to sort groups of binding proteins that share similar epitopes. For example, binding proteins that compete for binding can be“binned” as a group of binding proteins that have overlapping or nearby epitopes, while those that do not compete are placed in a separate group of binding proteins that do not have overlapping or nearby epitopes.

[0148] The term "kon" or "ka" refers to the on-rate constant for association of an antibody to the antigen to form the antibody / antigen complex. The rate can be determined using standard assays, such as a surface plasmon resonance, biolayer inferometry, or ELISA assay.

[0149] The term "k0ff" or "kd" refers to the off-rate constant for dissociation of an antibody from the antibody / antigen complex. The rate can be determined using standard assays, such as a surface plasmon resonance, biolayer inferometry, or ELISA assay.

[0150] The term "KD" refers to the equilibrium dissociation constant of a particular antibody- antigen interaction. KD is calculated by ka / kd. The rate can be determined using standard assays, such as a surface plasmon resonance, biolayer inferometry, or ELISA assay.

[0151] The term“p” or“herboxidiene splicing modulator loading” or“herboxidiene splicing modulatorantibody ratio” or“herboxidiene splicing modulator-to-antibody ratio” or“HAR” refers to the number of herboxidiene splicing modulators per antibody or antigen binding fragment, i.e. , herboxidiene splicing modulator loading, or the number of -L-H moieties per antibody or antigen binding fragment (Ab) in ADCs disclosed herein. In ADCs comprising a herboxidiene splicing modulator,“p” refers to the number of herboxidiene splicing modulators linked to the antibody or antigen binding fragment. For example, if two herboxidiene splicing modulator (e.g., two compounds each having the structure of H3) are linked to an antibody or antigen binding fragment, p = 2. In compositions comprising multiple copies of ADCs as described herein,“average p” refers to the average number of -L-H moieties per antibody or antigen binding fragment, also referred to as“average herboxidiene splicing modulator loading.”

[0152] A“linker” or“linker moiety” is used herein to refer to any chemical moiety that is capable of covalently joining a compound, usually a drug moiety such as a herboxidiene splicing modulator drug moiety, to another moiety such as an antibody or antigen binding fragment. Linkers can be susceptible to or substantially resistant to acid-induced cleavage, peptidase- induced cleavage, light-based cleavage, esterase-induced cleavage, and / or disulfide bond cleavage, at conditions under which the compound or the antibody remains active.

[0153] The term“agent” is used herein to refer to a chemical compound, a mixture of chemical compounds, a biological macromolecule, or an extract made from biological materials. The term“therapeutic agent” or“drug” refers to an agent that is capable of modulating a biological process and / or has biological activity. The herboxidiene splicing modulator described herein are exemplary therapeutic agents.

[0154] The term "chemotherapeutic agent" or“anti-cancer agent” is used herein to refer to all agents that are effective in treating cancer regardless of mechanism of action. Inhibition of metastasis or angiogenesis is frequently a property of a chemotherapeutic agent.Chemotherapeutic agents include antibodies, biological molecules, and small molecules, and encompass the herboxidiene splicing modulator compounds described herein. Achemotherapeutic agent may be a cytotoxic or cytostatic agent. The term“cytostatic agent” refers to an agent that inhibits or suppresses cell growth and / or multiplication of cells. The term "cytotoxic agent" refers to a substance that causes cell death primarily by interfering with a cell’s expression activity and / or functioning.

[0155] As used herein, the terms“herboxidiene splicing modulator,”“herboxidiene spliceosome modulator,” or“herboxidiene splice modulator” refer to compounds that have anti-cancer activity by interacting with components of the spliceosome and structurally related to herboxidiene. In some embodiments, a herboxidiene splicing modulator alters the rate or form of splicing in a target cell. Herboxidiene splicing modulators that function as inhibitory agents, for example, are capable of decreasing uncontrolled cellular proliferation. In some embodiments, theherboxidiene splicing modulators may act by binding to the SF3b spliceosome complex. Such modulators may be naturally occurring or synthetic derivatives or analogs of herboxidiene. As used herein, the terms "derivative" and "analog" when referring to a herboxidiene splicing modulator, or the like, means any such compound that retains essentially the same, similar, or enhanced biological function or activity as herboxidiene but has an altered chemical or biological structure. In some embodiments, the herboxidiene splicing modulator is aherboxidiene derivative.

[0156] As used herein, a“herboxidiene splicing modulator drug moiety” refers to the component of an ADC or composition that provides the structure of a herboxidiene splicing modulatorcompound, e.g., the herboxidiene splicing modulator (H) component in an ADC of Formula (I), or in a composition comprising -L-H.

[0157] As used herein, a“spliceosome” refers to a ribonucleoprotein complex that removes introns from one or more RNA segments, such as pre-mRNA segments.

[0158] The term "homolog" refers to a molecule which exhibits homology to another molecule, by for example, having sequences of chemical residues that are the same or similar at corresponding positions.

[0159] The term "inhibit" or "inhibition of," as used herein, means to reduce by a measurable amount, and can include but does not require complete prevention or inhibition.

[0160] The term“target-negative,”“target antigen-negative,” or“antigen-negative” refers to the absence of target antigen expression by a cell or tissue. The term“target-positive,”“target antigen-positive,” or“antigen-positive” refers to the presence of target antigen expression. For example, a cell or a cell line that does not express a target antigen may be described as target negative, whereas a cell or cell line that expresses a target antigen may be described as target positive.

[0161] The term“bystander killing” or“bystander effect” refers to the killing of target-negative cells in the presence of target-positive cells, wherein killing of target- negative cells is not observed in the absence of target-positive cells. Cell-to-cell contact, or at least proximity between target-positive and target-negative cells, enables bystander killing. This type of killing is distinguishable from“off-target killing,” which refers to the indiscriminate killing of target negative cells. “Off-target killing” may be observed in the absence of target-positive cells.

[0162] The terms“neoplastic disorder” and“cancer” are used herein interchangeably to refer to the presence of cells possessing characteristics typical of cancer-causing cells, such as uncontrolled proliferation, immortality, metastatic potential, rapid growth and proliferation rate, and / or certain morphological features. Often, cancer cells can be in the form of a tumor or mass, but such cells may exist alone within a subject, or may circulate in the blood stream as independent cells, such as leukemic or lymphoma cells. The terms“neoplastic disorder” and "cancer" includes all types of cancers and cancer metastases, including hematological malignancy, solid tumors, sarcomas, carcinomas and other solid and non-solid tumor cancers. Hematological malignancies may include B-cell malignancies, cancers of the blood (leukemias), cancers of plasma cells (myelomas, e.g., multiple myeloma), or cancers of the lymph nodes (lymphomas). Exemplary B-cell malignancies include chronic lymphocytic leukemia (CLL), follicular lymphoma, mantle cell lymphoma, and diffuse large B-cell lymphoma. Leukemias may include acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), chronic lymphocytic leukemia (CLL), chronic myelogenous leukemia (CML), chronic myelomonocytic leukemia (CMML), acute monocytic leukemia (AMoL), etc. Lymphomas may include Hodgkin's lymphoma and non-Hodgkin's lymphoma. Other hematologic malignancies may include myelodysplasia syndrome (MDS). Solid tumors may include carcinomas such asadenocarcinoma, e.g., breast cancer, pancreatic cancer, prostate cancer, colon or colorectal cancer, lung cancer, gastric cancer, cervical cancer, endometrial cancer, ovarian cancer, cholangiocarcinoma, glioma, melanoma, etc.

[0163] The terms“tumor” and“neoplasm” refer to any mass of tissue that results from excessive cell growth or proliferation, either benign or malignant, including precancerous lesions.

[0164] The terms“tumor cell” and“neoplastic cell” are used interchangeably and refer to individual cells or the total population of cells derived from a tumor or neoplasm, including both non-tumorigenic cells and cancer stem cells. As used herein, the term“tumor cell” will be modified by the term“non-tumorigenic” when referring solely to those tumor cells lacking the capacity to renew and differentiate to distinguish those tumor cells from cancer stem cells.

[0165] The terms“subject” and“patient” are used interchangeably herein to refer to any animal, such as any mammal, including but not limited to, humans, non-human primates, rodents, and the like. In some embodiments, the mammal is a mouse. In some embodiments, the mammal is a human. In some embodiments, the subject is a mouse. In some embodiments, the subject is a human.

[0166] The term“co-administration” or administration“in combination with” one or more therapeutic agents includes concurrent administration and consecutive administration in any order.

[0167] A“pharmaceutical composition” refers to a preparation which is in such form as to permit administration and subsequently provide the intended biological activity of the activeingredient(s) and / or to achieve a therapeutic effect, and which contains no additional components which are unacceptably toxic to a subject to which the formulation would be administered. The pharmaceutical composition may be sterile.

[0168] A "pharmaceutical excipient" comprises a material such as an adjuvant, a carrier, pH- adjusting and buffering agents, tonicity adjusting agents, wetting agents, preservative, and the like.

[0169] "Pharmaceutically acceptable" means approved or approvable by a regulatory agency of the Federal or a state government, or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia, for use in animals, and more particularly in humans

[0170] A "pharmaceutically acceptable salt" is a salt that retains the desired biological activity of the parent compound and does not impart undesired toxicological effects. Examples of such salts are: (a) acid addition salts formed with inorganic acids, for example, hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid and the like; and salts formed with organic acids, for example, acetic acid, oxalic acid, tartaric acid, succinic acid, maleic acid, fumaric acid, gluconic acid, citric acid, malic acid, ascorbic acid, benzoic acid, tannic acid, palmitic acid, alginic acid, polyglutamic acid, naphthalenesulfonic acid, methanesulfonic acid, p- toluenesulfonic acid, naphthalenedisulfonic acid, polygalacturonic acid, and the like; and (b)salts formed from elemental anions such as chlorine, bromine, and iodine. See, e.g., Haynes et al. "Commentary: Occurrence of Pharmaceutically Acceptable Anions and Cations in the Cambridge Structural Database," J Pharmaceutical Sciences, vol. 94, no. 10 (2005), and Berge et al. "Pharmaceutical Salts," J Pharmaceutical Sciences, vol. 66, no. 1 (1977), which are incorporated by reference herein.

[0171] The term“effective amount,” as used herein, refers to the amount of a compound, ADC, or composition described herein (e.g., a herboxidiene splicing modulator or an ADC) that is sufficient to perform a specifically stated purpose, for example to produce a therapeutic effect after administration, such as a reduction in tumor growth rate or tumor volume, a reduction in a symptom of cancer, or some other indicia of treatment efficacy. An effective amount can be determined in a routine manner in relation to the stated purpose. The term“therapeutically effective amount” refers to an amount of a compound, an ADC, or composition described herein effective for detectable killing, reduction, and / or inhibition of the growth or spread of tumor cells, the size or number of tumors, and / or other measure of the level, stage, progression and / or severity of the cancer. The therapeutically effective amount can vary depending upon the intended application (in vitro or in vivo), or the subject and disease condition being treated, e.g., the weight and age of the subject, the severity of the disease condition, the manner of administration and the like, which can readily be determined by one of ordinary skill in the art. The term also applies to a dose that will induce a particular response in target cells, e.g., inhibition of cell growth. The specific dose may vary depending on, for example, the particular pharmaceutical composition, the subject and their age and existing health conditions or risk for health conditions, the dosing regimen to be followed, the severity of the disease, whether it is administered in combination with other agents, timing of administration, the tissue to which it is administered, and the physical delivery system in which it is carried. In the case of cancer, a therapeutically effective amount of ADC can reduce the number of cancer cells, reduce tumor size, inhibit (e.g., slow or stop) tumor metastasis, inhibit (e.g., slow or stop) tumor growth, and / or relieve one or more symptoms.

[0172] A "prophylactically effective amount" refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired prophylactic result. Typically, since a prophylactic dose is used in subjects prior to or at an earlier stage of disease, theprophylactically effective amount will be less than the therapeutically effective amount.

[0173] As used herein, "to treat" or "therapeutic" and grammatically related terms, refer to any improvement of any consequence of disease, such as prolonged survival, less morbidity, and / or a lessening of side effects which result from an alternative therapeutic modality. As is readily appreciated in the art, full eradication of disease is encompassed but not required for a treatment act. “Treatment” or“treat,” as used herein, refers to the administration of a described ADC or composition to a subject, e.g., a patient. The treatment can be to cure, heal, alleviate, relieve, alter, remedy, ameliorate, palliate, improve or affect the disorder, the symptoms of thedisorder or the predisposition toward the disorder, e.g., a cancer. In some embodiments, in addition to treating a subject with a condition, a composition disclosed herein can also be provided prophylactically to prevent or reduce the likelihood of developing that condition.

[0174] In some embodiments, a labeled ADC is used. Suitable "labels" include radionuclides, enzymes, substrates, cofactors, inhibitors, fluorescent moieties, chemiluminescent moieties, magnetic particles, and the like.

[0175] By "protein," as used herein, is meant at least two covalently attached amino acids. The term encompasses polypeptides, oligopeptides, and peptides. In some embodiments, the two or more covalently attached amino acids are attached by a peptide bond. The protein may be made up of naturally occurring amino acids and peptide bonds, for example when the protein is made recombinantly using expression systems and host cells. Alternatively, the protein may include synthetic amino acids (e.g., homophenylalanine, citrulline, ornithine, and norleucine), or peptidomimetic structures, i.e. , "peptide or protein analogs," such as peptoids. Peptoids are an exemplary class of peptidomimetics whose side chains are appended to the nitrogen atom of the peptide backbone, rather than to the a-carbons (as they are in amino acids), and have different hydrogen bonding and conformational characteristics in comparison to peptides (see, e.g., Simon et al. (1992) Proc Natl Acad Sci. USA 89:9367). As such, peptoids can be resistant to proteolysis or other physiological or storage conditions, and effective at permeating cell membranes. Such synthetic amino acids may be incorporated in particular when the antibody is synthesized in vitro by conventional methods well known in the art. In addition, any combination of peptidomimetic, synthetic and naturally occurring residues / structures can be used. "Amino acid" also includes imino acid residues, such as proline and hydroxyproline. The amino acid "R group" or "side chain" may be in either the (L)- or the (S)-configuration. In a specificembodiment, the amino acids are in the (L)- or (S)-configuration.

[0176] A "recombinant protein" is a protein made using recombinant techniques using any techniques and methods known in the art, i.e., through the expression of a recombinant nucleic acid. Methods and techniques for the production of recombinant proteins are well known in the art.

[0177] An "isolated" protein is unaccompanied by at least some of the material with which it is normally associated in its natural state, for example constituting at least about 5%, or at least about 50% by weight of the total protein in a given sample. It is understood that the isolated protein may constitute from 5% to 99.9% by weight of the total protein content depending on the circumstances. For example, the protein may be made at a significantly higher concentration through the use of an inducible promoter or high expression promoter, such that the protein is made at increased concentration levels. The definition includes the production of an antibody in a wide variety of organisms and / or host cells that are known in the art.

[0178] For amino acid sequences, sequence identity and / or similarity may be determined using standard techniques known in the art, including, but not limited to, the local sequence identityalgorithm of Smith and Waterman (1981) Adv Appl Math. 2:482, the sequence identity alignment algorithm of Needleman and Wunsch (1970) J Mol Biol. 48:443, the search for similarity method of Pearson and Lipman (1988) Proc Nat Acad Sci. USA 85:2444,computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Drive,Madison, Wis.), the Best Fit sequence program described by Devereux et al. (1984) Nucl Acid Res. 12:387-95, preferably using the default settings, or by inspection. Preferably, percent identity is calculated by FastDB based upon the following parameters: mismatch penalty of 1 ; gap penalty of 1 ; gap size penalty of 0.33; and joining penalty of 30 ("Current Methods in Sequence Comparison and Analysis," Macromolecule Sequencing and Synthesis, Selected Methods and Applications, pp. 127-149 (1988), Alan R. Liss, Inc).

[0179] An example of a useful algorithm is PILEUP. PILEUP creates a multiple sequence alignment from a group of related sequences using progressive, pairwise alignments. It can also plot a tree showing the clustering relationships used to create the alignment. PILEUP uses a simplification of the progressive alignment method of Feng & Doolittle (1987) J Mol Evol. 35:351-60; the method is similar to that described by Higgins and Sharp (1989) CABIOS 5:151- 3. Useful PILEUP parameters including a default gap weight of 3.00, a default gap length weight of 0.10, and weighted end gaps.

[0180] Another example of a useful algorithm is the BLAST algorithm, described in: Altschul et al. (1990) J Mol Biol. 215:403-10; Altschul et al. (1997) Nucl Acid Res. 25:3389-402; and Karin et al. (1993) Proc Natl Acad Sci. USA 90:5873-87. A particularly useful BLAST program is the WU-BLAST-2 program which was obtained from Altschul et al. (1996) Methods in Enzymology 266:460-80. WU-BLAST-2 uses several search parameters, most of which are set to the default values. The adjustable parameters are set with the following values: overlap span=l, overlap fraction=0.125, word threshold (T)=ll. The HSP S and HSP S2 parameters are dynamic values and are established by the program itself depending upon the composition of the particular sequence and composition of the particular database against which the sequence of interest is being searched; however, the values may be adjusted to increase sensitivity.

[0181] An additional useful algorithm is gapped BLAST as reported by Altschul et al. (1997)Nucl Acid Res. 25:3389-402. Gapped BLAST uses BLOSUM-62 substitution scores; threshold T parameter set to 9; the two-hit method to trigger ungapped extensions, charges gap lengths of k a cost of 10+k; Xu set to 16, and Xg set to 40 for database search stage and to 67 for the output stage of the algorithms. Gapped alignments are triggered by a score corresponding to about 22 bits.

[0182] Generally, the amino acid homology, similarity, or identity between proteins disclosed herein and variants thereof, including variants of target antigens (such as HER2, CD138, or EPHA2, MSLN, FOLH1 , CDH6, CEACAM5, CFC1 B, ENPP3, FOLR1 , HAVCR1 , KIT, MET,MUC16, SLC39A6, SLC44A4, or STEAP1) and variants of antibody variable domains (includingindividual variant CDRs), are at least 80% to the sequences depicted herein, e.g., homologies or identities of at least 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, almost 100%, or 100%.

[0183] In a similar manner, "percent (%) nucleic acid sequence identity" with respect to the nucleic acid sequence of the antibodies and other proteins identified herein is defined as the percentage of nucleotide residues in a candidate sequence that are identical with the nucleotide residues in the coding sequence of the antigen binding protein. A specific method utilizes the BLASTN module of WU-BLAST-2 set to the default parameters, with overlap span and overlap fraction set to 1 and 0.125, respectively.

[0184] While the site or region for introducing an amino acid sequence variation ispredetermined, the mutation per se need not be predetermined. For example, in order to optimize the performance of a mutation at a given site, random mutagenesis may be conducted at the target codon or region and the expressed antigen binding protein CDR variants screened for the optimal combination of desired activity. Techniques for making substitution mutations at predetermined sites in DNA having a known sequence are well known, for example, MI3 primer mutagenesis and PCR mutagenesis

[0185] "Alkyl" or "alkyl group," as used herein, means a straight-chain, branched, or cyclic hydrocarbon chain that is completely saturated. In certain embodiments, alkyl groups may contain 1-8 carbon atoms ("CrCsalkyl"). In certain embodiments, alkyl groups may contain 1-6 carbon atoms ("Ci-C6alkyl"). In certain embodiments, alkyl groups contain 1-3 carbon atoms.In still other embodiments, alkyl groups contain 2-3 carbon atoms, and in yet otherembodiments alkyl groups contain 1-2 carbon atoms.

[0186] “Alkylalkoxy," as used herein, means an alkyl group substituted with an alkoxy group.

[0187] "Alkoxy", as used herein, refers to an alkyl group, as previously defined, attached to the principal carbon chain through an oxygen ("alkoxy") atom.

[0188] "Alkylhydroxy," as used herein, means an alkyl group substituted with a hydroxyl group.

[0189] "Hydroxy" or "hydroxyl," as used herein, refers to -OH.

[0190] "Carbocycle" or "carbocyclyl" as used herein, includes both aromatic (e.g., aryl) and non aromatic (e.g., cycloalkyl) groups. In certain embodiments, carbocycle groups contain 3-10 carbon atoms (“3 to 10 membered carbocycle”). In certain embodiments, carbocycle groups contain 3-8 carbon atoms (“3 to 8 membered carbocycle”). In certain embodiments, carbocycle groups contain 3-6 carbon atoms (“3 to 6 membered carbocycle”). In certain embodiments, carbocycle groups contain 3-5 carbon atoms (“3 to 5 membered carbocycle”).

[0191] "Haloalkyl” as used herein, refers to an alkyl group substituted with one or more halogen atoms.

[0192] "Halogen" refers to a radical of any halogen, e.g., -F, -Cl, -Br, or -I.

[0193] The terms "heterocycle", "heterocyclyl", and "heterocyclic" as used herein, mean a monocyclic heterocycle, a bicyclic heterocycle, or a tricyclic heterocycle containing at least one heteroatom in the ring.

[0194] The monocyclic heterocycle is a 3-, 4-, 5-, 6-, 7, or 8-membered ring containing at least one heteroatom independently chosen from O, N, and S. In some embodiments, the heterocycle is a 3- or 4-membered ring containing one heteroatom chosen from O, N and S. In some embodiments, the heterocycle is a 5-membered ring containing zero or one double bond and one, two or three heteroatoms chosen from O, N and S. In some embodiments, the heterocycle is a 6-, 7-, or 8-membered ring containing zero, one or two double bonds and one, two or three heteroatoms chosen from O, N and S. Representative examples of monocyclic heterocycle include, but are not limited to, azetidinyl, azepanyl, aziridinyl, diazepanyl, 1 ,3- dioxanyl, 1 ,3-dioxolanyl, dihydropyranyl (including 3,4-dihydro-2H-pyran-6-yl), 1 ,3-dithiolanyl,1.3-dithianyl, imidazolinyl, imidazolidinyl, isothiazolinyl, isothiazolidinyl, isoxazolinyl,isoxazolidinyl, morpholinyl, oxadiazolinyl, oxadiazolidinyl, oxazolinyl, oxazolidinyl, piperazinyl, piperidinyl, pyranyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl, pyrrolidinyl, tetrahydrofuranyl, tetrahydropyranyl (including tetrahydro-2H-pyran-4-yl), tetrahydrothienyl, thiadiazolinyl, thiadiazolidinyl, thiazolinyl, thiazolidinyl, thiomorpholinyl, 1 ,1-dioxidothiomorpholinyl(thiomorpholine sulfone), thiopyranyl, and trithianyl.

[0195] The bicyclic heterocycles of the present disclosure may include a monocyclicheterocycle fused to an aryl group, or a monocyclic heterocycle fused to a monocyclic cycloalkyl, or a monocyclic heterocycle fused to a monocyclic cycloalkenyl, or a monocyclic heterocycle fused to a monocyclic heterocycle having a total of 5 to 12 ring atoms. Examples of bicyclic heterocycles include, but are not limited to, 3,4-dihydro-2H-pyranyl, 1 ,3-benzodioxolyl,1.3-benzodithiolyl, 2,3-dihydro-1 ,4-benzodioxinyl, 2,3-dihydro-1-benzofuranyl, 2,3-dihydro-1- benzothienyl, 2,3-dihydro-1 H-indolyl, and 1 ,2, 3, 4- tetrahydroquinolinyl.

[0196] The terms "heterocycle", "heterocyclyl", and "heterocyclic" encompass heteroaryls. "Heteroaryl" refers to a cyclic moiety having one or more closed rings, with one or more heteroatoms (oxygen, nitrogen or sulfur) in at least one of the rings, wherein at least one of the rings is aromatic, and wherein the ring or rings may independently be fused, and / or bridged. Examples include without limitation phenyl, thiophenyl, triazolyl, pyridinyl, pyrimidinyl, pyridazinyl, and pyrazinyl.

[0197] As described herein, compounds of the disclosure may contain“optionally substituted” moieties. In general, the term“substituted,” whether preceded by the term“optionally” or not, means that one or more hydrogens of the designated moiety are replaced with a suitable substituent. Unless otherwise indicated, an“optionally substituted” group may have a suitable substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent chosen from a specified group, the substituent may be either the same or different at each position. Combinations ofsubstituents envisioned under this disclosure are preferably those that result in the formation of stable or chemically feasible compounds.

[0198] One skilled in the art will be understand that“substitution” or“substituted with” or “absent” includes the implicit proviso that such substitution or absence is in accordance with permitted valence of the substituted atom and the substituent, and that the substitution or absence results in a stable compound, e.g., which does not spontaneously undergotransformation such as by rearrangement, cyclization, elimination, etc. For purposes of this disclosure, the heteroatoms such as nitrogen may have hydrogen substituents, and / or any permissible substituents of organic compounds described herein which satisfy the valences of the heteroatoms.

[0199] "Stable" refers to compounds that are not substantially altered chemically and / or physically when subjected to conditions to allow for their production, detection, and, in certain embodiments, their recovery, purification, and use for one or more of the purposes disclosed herein. In some embodiments, a stable compound or chemically feasible compound is one that is not substantially altered when kept at a temperature of 40 °C or less, in the absence of moisture or other chemically reactive conditions, for at least a week. In some embodiments, the compounds disclosed herein are stable.

[0200] Enantiomers taught herein may include "enantiomerically pure" isomers that comprise substantially a single enantiomer, for example, greater than or equal to 90%, 92%, 95%, 98%, or 99%, or equal to 100% of a single enantiomer, at a particular asymmetric center or centers. An "asymmetric center" or "chiral center" refers to a tetrahedral carbon atom that comprises four different substituents.

[0201] The compounds described herein may also contain unnatural proportions of atomic isotopes at one or more of the atoms that constitute such compounds. For example, the compounds may be radiolabeled with radioactive isotopes, such as, for example, deuterium (2H), tritium (3H), carbon-13 (13C), or carbon-14 (14C). All isotopic variations of the compounds disclosed herein, whether radioactive or not, are intended to be encompassed within the scope of the present disclosure. In addition, all tautomeric forms of the compounds described herein are intended to be within the scope of the claimed disclosure.Antibody-Drug Conjugates

[0202] The antibody-drug conjugate (ADC) compounds of the present disclosure include those with anti-cancer activity. In particular, the ADC compounds include an antibody or antigen binding fragment (including an antigen binding fragment thereof) conjugated (i.e. , covalently attached by a linker) to a herboxidiene splicing modulator, e.g., wherein the herboxidiene splicing modulator when not conjugated to an antibody or antigen binding fragment has a cytotoxic or cytostatic effect. In various embodiments, the herboxidiene splicing modulator when not conjugated to an antibody or antigen binding fragment is capable of binding to and / or interacting with the SF3b spliceosome complex. In various embodiments, the herboxidienesplicing modulator when not conjugated to an antibody or antigen binding fragment is capable of modulating in vitro and / or in vivo RNA splicing. By targeting RNA splicing, in variousembodiments, the herboxidiene splicing modulator and ADCs disclosed herein are potent antiproliferative agents. In various embodiments, the herboxidiene splicing modulator and ADCs disclosed herein can target both actively dividing and quiescent cells.

[0203] In various embodiments, the present disclosure is based, at least in part, on the discovery that certain biologically active herboxidiene splicing modulator may provide improved properties when used in ADCs. While a herboxidiene splicing modulator may show desirably improved features (e.g., robust SF3b spliceosome complex binding, potent modulation of RNA splicing) when used on its own, in various embodiments, the herboxidiene splicing modulator may exhibit fewer of the same desirably improved features when conjugated to an antibody or antigen binding fragment. Thus, the development and production of an ADC for use as a human therapeutic agent, e.g., as an oncologic agent, may require more than the identification of an antibody capable of binding to a desired target or targets and attaching to a drug used on its own to treat cancer. Linking the antibody to the herboxidiene splicing modulator may have significant effects on the activity of one or both of the antibody and the herboxidiene splicing modulator, effects which will vary depending on the type of linker and / or herboxidiene splicing modulator chosen. In some embodiments, therefore, the components of the ADC are selected to (i) retain one or more therapeutic properties exhibited by the antibody and herboxidiene splicing modulator moieties in isolation, (ii) maintain the specific binding properties of the antibody or antigen binding fragment; (iii) optimize herboxidiene splicing modulator loading and herboxidiene splicing modulator-to-antibody ratios; (iv) allow delivery, e.g., intracellular delivery, of the herboxidiene splicing modulator moiety via stable attachment to the antibody or antigen binding fragment; (v) retain ADC stability as an intact conjugate until transport or delivery to a target site; (vi) minimize aggregation of the ADC prior to or after administration; (vii) allow for the therapeutic effect, e.g., cytotoxic effect, of the herboxidiene splicing modulator moiety after cleavage or other release mechanism in the cellular environment; (viii) exhibit in vivo anti-cancer treatment efficacy comparable to or superior to that of the antibody and herboxidiene splicing modulator moieties in isolation; (ix) minimize off-target killing by the herboxidiene splicing modulator moiety; and / or (x) exhibit desirable pharmacokinetic and pharmacodynamics properties, formulatability, and toxicologic / immunologic profiles. Each of these properties may be needed to identify an improved ADC for therapeutic use (Ab et al. (2015) Mol Cancer Ther. 14:1605-13).

[0204] In various embodiments, the ADCs disclosed herein exhibit unexpectedly favorable properties in some or each of the categories listed above. For instance, in some embodiments, the ADC constructs disclosed herein exhibit surprisingly favorable herboxidiene splicing modulator loading, aggregation, and / or stability profiles, and / or preserve antibody binding function, drug activity, and / or improved bystander killing, while reducing off-target killing, ascompared to ADCs comprising an alternate linker and / or drug moiety (e.g., an alternate herboxidiene splicing modulator). In some embodiments, ADC constructs disclosed herein demonstrate superior stability, activity, potency, or other effect (measured in vivo or in vitro) as compared to ADCs using an alternate linker and / or herboxidiene splicing modulator moiety. In some embodiments, the ADC constructs disclosed herein exhibit in vivo treatment efficacy when administered as a single dose. In some embodiments, the ADC constructs disclosed herein are surprisingly stable as compared to ADCs using an alternate linker and / or herboxidiene splicing modulator moiety.

[0205] The ADC compounds of the present disclosure may selectively deliver an effective dose of a cytotoxic or cytostatic agent to cancer cells or to tumor tissue. It has been discovered that the disclosed ADCs have potent cytotoxic and / or cytostatic activity against cells expressing the respective target antigen (e.g., HER2, CD138, EPHA2, MSLN, FOLH1 , CDH6, CEACAM5, CFC1 B, ENPP3, FOLR1 , HAVCR1 , KIT, MET, MUC16, SLC39A6, SLC44A4, or STEAPI). In some embodiments, the cytotoxic and / or cytostatic activity of the ADC is dependent on target antigen expression in a cell. In some embodiments, the disclosed ADCs are particularly effective at killing cancer cells expressing a target antigen while minimizing off-target killing. In some embodiments, the disclosed ADCs do not exhibit a cytotoxic and / or cytostatic effect on cancer cells that do not express a target antigen.

[0206] Exemplary HER2-expressing cancers include but are not limited to breast cancer, gastric cancer, bladder cancer, urothelial cell carcinoma, esophageal cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), salivary duct carcinoma, cervical cancer, endometrial cancer, and ovarian cancer (English et al. (2013) Mol Diagn Ther. 17:85-99).

[0207] Exemplary CD138-expressing cancers include but are not limited to intrathoracic cancer (e.g., lung cancer, mesothelioma), skin cancer (e.g., basal cell carcinoma, squamous cell carcinoma), head and neck cancer (e.g., laryngeal, hypopharynx, nasopharyngeal), breast cancer, urogenital cancer (e.g., cervical cancer, ovarian cancer, endometrial cancer, prostate cancer, bladder cancer, urothelial cancer), hematological malignancies (e.g., myeloma such as multiple myeloma, B-cell malignancies, Hodgkin’s lymphoma), and thyroid cancer (Szatmari et al. (2015) Dis Markers 2015:796052).

[0208] Exemplary EPHA2-expressing cancers include breast cancer, brain cancer, ovarian cancer, bladder cancer, pancreatic cancer, esophageal cancer, lung cancer, prostate cancer, melanoma, esophageal cancer, and gastric cancer (Tandon et al. (2011) Expert Opin Ther Targets 15(1):31-51).

[0209] In some embodiments, cleavage of an ADC releases the herboxidiene splicing modulator from the antibody or antigen binding fragment and linker. In some embodiments, the linker and / or herboxidiene splicing modulator is designed to facilitate bystander killing (the killing of neighboring cells). In some embodiments, the linker and / or herboxidiene splicing modulatoris designed to facilitate bystander killing through cleavage after cellular internalization and diffusion of the linker-herboxidiene splicing modulator moiety and / or the herboxidiene splicing modulator moiety alone to neighboring cells. In some embodiments, the linker promotes cellular internalization. In some embodiments, the linker is designed to minimize cleavage in the extracellular environment and thereby reduce toxicity to off-target tissue (e.g., non-cancerous tissue), while preserving ADC binding to target tissue and bystander killing of cancerous tissue that does not express an antigen targeted by the antibody or antigen binding fragment of an ADC, but surrounds target cancer tissue expressing that antigen. In some embodiments, the herboxidiene splicing modulator moiety, or the catabolite of the herboxidiene splicing modulator moiety produced by cleavage of an ADC, is designed to facilitate uptake by target cells or by neighboring cells (i.e. , cell permeable). Such herboxidiene splicing modulator moieties and catabolites may be referred to herein as“bystander active,” whereas drug moieties or catabolites with reduced cell permeability may be referred to as“bystander inactive.”

[0210] In some embodiments, the disclosed ADCs also demonstrate bystander killing activity, but low off-target cytotoxicity. Without being bound by theory, the bystander killing activity of an ADC may be particularly beneficial where its penetration into a solid tumor is limited and / or target antigen expression among tumor cells is heterogeneous. In some embodiments, an ADC comprising a cleavable linker is particularly effective at bystander killing and / or demonstrates improved bystander killing activity, relative to comparable treatment with an ADC comprising a non-cleavable linker. In some embodiments, the ADCs disclosed herein exhibit improved solubility and target cell penetrance over the drug moieties on their own. In someembodiments, the ADCs disclosed herein exhibit improved cytotoxicity over that of the herboxidiene splicing modulator moiety on its own. In some embodiments, ADCs disclosed herein use drug moieties that exhibit lower cytotoxicity, when evaluated as a stand-alone herboxidiene splicing modulator, yet are surprisingly better than ADCs comprising other herboxidiene splicing modulator moieties which have higher cytotoxicity when evaluated as a stand-alone herboxidiene splicing modulator. In some embodiments, cleavage and release of the herboxidiene splicing modulator improves cytotoxicity of the ADC, relative to comparable treatment with an ADC comprising a non-cleavable linker. In other embodiments, cleavage and release of the herboxidiene splicing modulator is not required for an ADC to possess a desirable biological activity. In some embodiments, an ADC comprising a non-cleavable linker having increased spacer length (e.g., ADL12) provides the same or similar cytotoxicity relative to comparable treatment with an ADC comprising a cleavable linker (e.g., ADL1 , ADL5) and surprisingly superior cytotoxicity relative to comparable treatment with an ADC comprising a shorter non-cleavable linker. In some embodiments, an ADC comprising a non-cleavable linker having increased spacer length without a carbonyl group (e.g., ADL12) provides the same or similar cytotoxicity relative to comparable treatment with an ADC comprising a cleavable linker(e.g., ADL1 , ADL5) and surprisingly superior cytotoxicity relative to comparable treatment withan ADC comprising a non-cleavable linker having the same or similar spacer length with a carbonyl group (e.g., ADL10). In some embodiments, the removal of a carbonyl group from a non-cleavable MC linker (e.g., ADL12) can result in a greater than 50-fold, greater than 75-fold, greater than 100-fold, greater than 150-fold, or greater than 200-fold increase in cytotoxicity, relative to comparable treatment with an ADC comprising an unmodified non-cleavable MC linker (e.g., ADL10). In some embodiments, the removal of a carbonyl group from a non- cleavable MC linker (e.g., ADL12) and increased spacer length (e.g., the addition of at least one spacer unit) can result in a greater than 50-fold, greater than 75-fold, greater than 100-fold, greater than 150-fold, or greater than 200-fold increase in cytotoxicity, relative to comparable treatment with an ADC comprising an unmodified non-cleavable MC linker (e.g., ADL10).

[0211] Provided herein are ADC compounds comprising an antibody or antigen binding fragment thereof (Ab) which targets a tumor cell, a splicing modulator drug moiety (D), and a linker moiety (L) that covalently attaches Ab to D. In certain aspects, the antibody or antigen binding fragment is able to bind to a tumor-associated antigen (e.g., HER2, CD138, EPHA2, MSLN, FOLH1 , CDH6, CEACAM5, CFC1 B, ENPP3, FOLR1 , HAVCR1 , KIT, MET, MUC16, SLC39A6, SLC44A4, or STEAP1) with high specificity and high affinity. In certainembodiments, the antibody or antigen binding fragment is internalized into a target cell upon binding, e.g., into a degradative compartment in the cell. In various embodiments, ADCs that internalize upon binding to a target cell, undergo degradation, and release the herboxidiene splicing modulator moiety to kill cancer cells may be used. The herboxidiene splicing modulator moiety may be released from the antibody and / or the linker moiety of the ADC by enzymatic action, hydrolysis, oxidation, or any other mechanism.

[0212] An exemplary ADC has Formula (I):Ab-(L-H)p(I) wherein Ab = an antibody or antigen binding fragment, L = a linker moiety, H = a herboxidiene splicing modulator drug moiety, and p = the number of splicing modulator drug moieties per antibody or antigen binding fragment.

[0213] In certain embodiments, the herboxidiene splicing modulator-targeting moiety for use in the described ADCs and compositions is an antibody or antigen binding fragment. Other exemplary drug-targeting moieties for use in the described ADCs and compositions are also provided and described herein. In some embodiments, a herboxidiene splicing modulator targeting moiety can be any one of a variety of cell-binding agents and non-antibody scaffolds.In some embodiments, the herboxidiene splicing modulator-targeting moiety is a cell-binding agent. As used herein, the term“cell-binding agent” refers to any agent that is capable of binding to an animal (e.g., human) cell and delivering a herboxidiene splicing modulator moiety (e.g., a herboxidiene splicing modulator drug moiety as disclosed herein). The termencompasses the exemplary antibodies and antigen binding fragments disclosed herein (e.g., monoclonal antibodies and fragments thereof such as Fabs and scFVs). The term further encompasses exemplary cell-binding agents such as DARPins, duobodies, bicyclic peptides, nanobodies, centyrins, MSH (melanocyte-stimulating hormone), receptor-Fc fusion molecules, T-cell receptor structures, steroid hormones such as androgens and estrogens, growth factors, colony-stimulating factors such as EGF, and other non-antibody scaffolds. In various embodiments, non-antibody scaffolds can broadly fall into two structural classes, namely domain-sized compounds (approximately 6-20 kDa) and constrained peptides (approximately 2- 4 kDa). Exemplary domain-sized scaffolds include but are not limited to affibodies, affilins, anticalins, atrimers, DARPins, FN3 scaffolds (e.g., adnectins and centyrins), fynomers, Kunitz domains, pronectins, O-bodies, and receptor-Fc fusion proteins, whereas exemplaryconstrained peptides include avimers, bicyclic peptides, and Cys-knots. In some embodiments, the drug-targeting moiety used in the described ADCs and compositions is selected from an affibody, an affilin, an anticalin, an atrimer, a DARPin, a FN3 scaffold such as an adnectin or a centyrin, a fynomer, a Kunitz domain, a pronectin, an O-body, an avimer, a bicyclic peptide, and a Cys-knot. In some embodiments, the drug-targeting moiety used in the described ADCs and compositions is a receptor-Fc fusion protein, e.g., a HER2-Fc chimeric fusion protein. Non antibody scaffolds are reviewed, e.g., in Vazquez- Lombardi et al. (2015) Drug Dis Today 20(10): 1271 -83.Antibodies

[0214] The antibody or antigen binding fragment (Ab) of Formula (I) includes within its scope any antibody or antigen binding fragment that specifically binds to a target antigen on a cancer cell. The antibody or antigen binding fragment may bind to a target antigen with a dissociation constant (KD) of £1 mM, £100 nM or £10 nM, or any amount in between, as measured by, e.g., BIAcore®analysis. In certain embodiments, the KDis 1 pM to 500 pM. In some embodiments, the KD is between 500 pM to 1 mM, 1 pM to 100 nM, or 100 mM to 10 nM.

[0215] In some embodiments, the antibody or antigen binding fragment is a four-chain antibody (also referred to as an immunoglobulin or a full-length or intact antibody), comprising two heavy chains and two light chains. In some embodiments, the antibody or antigen binding fragment is a two-chain half body (one light chain and one heavy chain), or an antigen binding fragment of an immunoglobulin. In some embodiments, the antibody or antigen binding fragment is an antigen binding fragment of an immunoglobulin that retains the ability to bind a target cancer antigen and / or provide a function of an immunoglobulin.

[0216] In some embodiments, the antibody or antigen binding fragment is an antibody or antigen binding fragment thereof. In some embodiments, the antibody or antigen binding fragment is an internalizing antibody or internalizing antigen binding fragment thereof. In some embodiments, the internalizing antibody or internalizing antigen binding fragment thereof binds to a target cancer antigen expressed on the surface of a cell and enters the cell upon binding.In some embodiments, the herboxidiene splicing modulator drug moiety of the ADC is released from the antibody or antigen binding fragment of the ADC after the ADC enters and is present in a cell expressing the target cancer antigen (i.e., after the ADC has been internalized), e.g., by cleavage, by degradation of the antibody or antigen binding fragment, or by any other suitable release mechanism.

[0217] Amino acid sequences of exemplary antibodies of the present disclosure are set forth in Tables 2-4.Table 1. AntibodiesTable 2. Amino acid sequences of mAb variable regionsTable 3. Amino acid sequences of mAb CDRsTable 4. Amino acid sequences of full-length mAb Ig chainsTable 5. Exemplary target antigen amino acid sequences

[0218] In various embodiments, an ADC disclosed herein may comprise any set of heavy and light chain variable domains listed in the tables above, or the set of six CDR sequences from the heavy and light chain set, e.g., by transplanting the six CDRs into a chosen human donor antibody framework. In various embodiments, an ADC disclosed herein may comprise amino acid sequences that are homologous to the sequences listed in the tables above, so long as the ADC retains the ability to bind to its target cancer antigen (e.g., with a KDof less than 1x1 O8M) and retains one or more functional properties of the ADCs disclosed herein (e.g., ability to internalize, modulate RNA splicing, inhibit cell growth, etc.).

[0219] In some embodiments, the ADC further comprises human heavy and light chain constant domains or fragments thereof. For instance, the ADC may comprise a human IgG heavy chain constant domain (such as an lgG1) and a human kappa or lambda light chain constant domain. In various embodiments, the antibody or antigen binding fragment of the described ADCscomprises a human immunoglobulin G subtype 1 (lgG1) heavy chain constant domain with a human Ig kappa light chain constant domain.

[0220] In various other embodiments, the target cancer antigen for an ADC is human epidermal growth factor receptor 2 (HER2).

[0221] In various embodiments, the anti-HER2 antibody or antigen binding fragment thereof comprises three heavy chain CDRs and three light chain CDRs as follows: heavy chain CDR1 (HCDR1) consisting of SEQ ID NO: 1 , heavy chain CDR2 (HCDR2) consisting of SEQ ID NO:2, heavy chain CDR3 (HCDR3) consisting of SEQ ID NO:3; light chain CDR1 (LCDR1) consisting of SEQ ID NO:4, light chain CDR2 (LCDR2) consisting of SEQ ID NO:5, and light chain CDR3 (LCDR3) consisting of SEQ ID NO:6, as defined by the Kabat numbering system.

[0222] In various embodiments, the anti-HER2 antibody or antigen binding fragment thereof comprises a heavy chain variable region comprising the amino acid sequence of SEQ IDNO: 19, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:20. In some embodiments, the anti-HER2 antibody or antigen binding fragment thereof comprises the heavy chain variable region amino acid sequence of SEQ ID NO: 19 and the light chain variable region amino acid sequence of SEQ ID NO:20, or sequences that are at least 95% identical to the disclosed sequences. In some embodiments, the anti-HER2 antibody or antigen binding fragment thereof has a heavy chain variable region amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO: 19 and / or a light chain variable region amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:20.

[0223] In various embodiments, the anti-HER2 antibody or antigen binding fragment thereof is an internalizing antibody or internalizing antigen binding fragment. In various embodiments, the anti-HER2 antibody comprises a human lgG1 heavy chain constant domain and a human Ig kappa light chain constant domain.

[0224] In various embodiments, the anti-HER2 antibody comprises the heavy chain amino acid sequence of SEQ ID NO: 19 or a sequence that is at least 95% identical to SEQ ID NO: 19, and the light chain amino acid sequence of SEQ ID NO:20 or a sequence that is at least 95% identical to SEQ ID NO:20. In particular embodiments, the anti-HER2 antibody comprises the heavy chain amino acid sequence of SEQ ID NO: 19 and the light chain amino acid sequence of SEQ ID NO:20, or sequences that are at least 95% identical to the disclosed sequences. In some embodiments, the anti-HER2 antibody has a heavy chain amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO: 19 and a light chain amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:20. In various embodiments, the anti-HER2 antibody is trastuzumab, or an antigen binding fragment thereof.

[0225] In various embodiments, the anti-HER2 antibody or antigen binding fragment thereof comprises the three heavy chain CDRs and three light chain CDRs of trastuzumab or whereinthe CDRs include no more than one, two, three, four, five, or six amino acid additions, deletions or substitutions of HCDR1 (SEQ ID NO:1), HCDR2 (SEQ ID NO:2), HCDR3 (SEQ ID NO:3); LCDR1 (SEQ ID NO:4), LCDR2 (SEQ ID NO:5), and LCDR3 (SEQ ID NO:6).

[0226] In various other embodiments, the target cancer antigen for an ADC is human syndecan- 1 (CD138).

[0227] In various embodiments, the anti-CD138 antibody or antigen binding fragment thereof comprises three heavy chain CDRs and three light chain CDRs as follows: heavy chain CDR1 (HCDR1) consisting of SEQ ID NO:7, heavy chain CDR2 (HCDR2) consisting of SEQ ID NO:8, heavy chain CDR3 (HCDR3) consisting of SEQ ID NO:9; light chain CDR1 (LCDR1) consisting of SEQ ID NO:10, light chain CDR2 (LCDR2) consisting of SEQ ID NO:11 , and light chain CDR3 (LCDR3) consisting of SEQ ID NO:12, as defined by the Kabat numbering system.

[0228] In various embodiments, the anti-CD138 antibody or antigen binding fragment thereof comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:21 , and a light chain variable region comprising the amino acid sequence of SEQ ID NO:22. In some embodiments, the anti-CD138 antibody or antigen binding fragment thereof comprises the heavy chain variable region amino acid sequence of SEQ ID NO:21 and the light chain variable region amino acid sequence of SEQ ID NO:22, or sequences that are at least 95% identical to the disclosed sequences. In some embodiments, the anti-CD138 antibody or antigen binding fragment thereof has a heavy chain variable region amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:21 and / or a light chain variable region amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:22.

[0229] In various embodiments, the anti-CD138 antibody or antigen binding fragment thereof is an internalizing antibody or internalizing antigen binding fragment. In various embodiments, the anti-CD138 antibody comprises a murine lgG2a heavy chain constant domain and a murine Ig kappa light chain constant domain. In various embodiments, the anti-CD138 antibody comprises a human lgG2a heavy chain constant domain and a human Ig kappa light chain constant domain.

[0230] In various embodiments, the anti-CD138 antibody comprises the heavy chain amino acid sequence of SEQ ID NO:21 or a sequence that is at least 95% identical to SEQ ID NO:21 , and the light chain amino acid sequence of SEQ ID NO:22 or a sequence that is at least 95% identical to SEQ ID NO:22. In particular embodiments, the anti-CD138 antibody comprises the heavy chain amino acid sequence of SEQ ID NO:21 and the light chain amino acid sequence of SEQ ID NO:22, or sequences that are at least 95% identical to the disclosed sequences. In some embodiments, the anti-CD138 antibody has a heavy chain amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:21 and a light chain amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99%identical to SEQ ID NO:22. In various embodiments, the anti-CD138 antibody is B-B4, or an antigen binding fragment thereof.

[0231] In various embodiments, the anti-CD138 antibody or antigen binding fragment thereof comprises the three heavy chain CDRs and three light chain CDRs of B-B4 or wherein the CDRs include no more than one, two, three, four, five, or six amino acid additions, deletions or substitutions of HCDR1 (SEQ ID NO:7), HCDR2 (SEQ ID NO:8), HCDR3 (SEQ ID NO:9);LCDR1 (SEQ ID NO:10), LCDR2 (SEQ ID NO:11), and LCDR3 (SEQ ID NO:12).

[0232] In various other embodiments, the target cancer antigen for an ADC is human ephrin type-A receptor 2 (EPHA2).

[0233] In various embodiments, the anti-EPHA2 antibody or antigen binding fragment thereof comprises three heavy chain CDRs and three light chain CDRs as follows: heavy chain CDR1 (HCDR1) consisting of SEQ ID NO: 13, heavy chain CDR2 (HCDR2) consisting of SEQ ID NO:14, heavy chain CDR3 (HCDR3) consisting of SEQ ID NO:15; light chain CDR1 (LCDR1) consisting of SEQ ID NO: 16, light chain CDR2 (LCDR2) consisting of SEQ ID NO: 17, and light chain CDR3 (LCDR3) consisting of SEQ ID NO: 18, as defined by the Kabat numbering system.

[0234] In various embodiments, the anti-EPHA2 antibody or antigen binding fragment thereof comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:23, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:24. In some embodiments, the anti-EPHA2 antibody or antigen binding fragment thereof comprises the heavy chain variable region amino acid sequence of SEQ ID NO:23 and the light chain variable region amino acid sequence of SEQ ID NO:24, or sequences that are at least 95% identical to the disclosed sequences. In some embodiments, the anti-EPHA2 antibody or antigen binding fragment thereof has a heavy chain variable region amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:23 and / or a light chain variable region amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:24.

[0235] In various embodiments, the anti-EPHA2 antibody or antigen binding fragment thereof is an internalizing antibody or internalizing antigen binding fragment. In various embodiments, the anti-EPHA2 antibody comprises a human lgG1 heavy chain constant domain and a human Ig kappa light chain constant domain.

[0236] In various embodiments, the anti-EPHA2 antibody comprises the heavy chain amino acid sequence of SEQ ID NO:23 or a sequence that is at least 95% identical to SEQ ID NO:23, and the light chain amino acid sequence of SEQ ID NO:24 or a sequence that is at least 95% identical to SEQ ID NO:24. In particular embodiments, the anti-EPHA2 antibody comprises the heavy chain amino acid sequence of SEQ ID NO:23 and the light chain amino acid sequence of SEQ ID NO:24, or sequences that are at least 95% identical to the disclosed sequences. In some embodiments, the anti-EPHA2 antibody has a heavy chain amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:23 and a lightchain amino acid sequence that is at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:24. In some embodiments, the anti-EPHA2 antibody comprises a heavy chain encoded by the nucleotide sequence of SEQ ID NO:23; and a light chain encoded by the nucleotide sequence of SEQ ID NO:24. In various embodiments, the anti-EPHA2 antibody is 1C1 , or an antigen binding fragment thereof.

[0237] In various embodiments, the anti-EPHA2 antibody or antigen binding fragment thereof comprises the three heavy chain CDRs and three light chain CDRs of 1C1 or wherein the CDRs include no more than one, two, three, four, five, or six amino acid additions, deletions or substitutions of HCDR1 (SEQ ID NO:13), HCDR2 (SEQ ID NO:14), HCDR3 (SEQ ID NO:15); LCDR1 (SEQ ID NO:16), LCDR2 (SEQ ID NO:17), and LCDR3 (SEQ ID NO:18).

[0238] In various embodiments, amino acid substitutions are of single residues. Insertions usually will be on the order of from about 1 to about 20 amino acid residues, although considerably larger insertions may be tolerated as long as biological function is retained (e.g., binding to a target antigen). Deletions usually range from about 1 to about 20 amino acid residues, although in some cases deletions may be much larger. Substitutions, deletions, insertions, or any combination thereof may be used to arrive at a final derivative or variant. Generally, these changes are done on a few amino acids to minimize the alteration of the molecule, particularly the immunogenicity and specificity of the antigen binding protein.However, larger changes may be tolerated in certain circumstances. Conservative substitutions are generally made in accordance with the following chart depicted as Table 6.Table 6Original Residue Exemplary SubstitutionsAla SerArg LysAsn Gin, HisAsp GluCys SerGin AsnGlu AspGly ProHis Asn, Ginlie Leu, ValLeu lie, ValLys Arg, Gin, GluMet Leu, liePhe Met, Leu, TyrSer ThrThr SerTrp TyrTyr Trp, PheVal lie, Leu

[0239] Substantial changes in function or immunological identity are made by selecting substitutions that are less conservative than those shown in Table 6. For example, substitutions may be made which more significantly affect: the structure of the polypeptide backbone in the area of the alteration, for example the alpha-helical or beta-sheet structure; the charge or hydrophobicity of the molecule at the target site; or the bulk of the side chain. The substitutions which in general may produce the greatest changes in the polypeptide's properties are those in which (a) a hydrophilic residue, e.g., seryl or threonyl, is substituted for (or by) a hydrophobic residue, e.g., leucyl, isoleucyl, phenylalanyl, valyl or alanyl; (b) a cysteine or proline is substituted for (or by) any other residue; (c) a residue having an electropositive side chain, e.g., lysyl, arginyl, or histidyl, is substituted for (or by) an electronegative residue, e.g., glutamyl or aspartyl; or (d) a residue having a bulky side chain, e.g., phenylalanine, is substituted for (or by) one not having a side chain, e.g., glycine.

[0240] In various embodiments where variant antibody sequences are used in an ADC, the variants typically exhibit the same qualitative biological activity and will elicit the same immune response, although variants may also be selected to modify the characteristics of the antigen binding proteins as needed. Alternatively, the variant may be designed such that the biological activity of the antigen binding protein is altered. For example, glycosylation sites may be altered or removed.

[0241] Various antibodies may be used with the ADCs used herein to target cancer cells. As shown below, the linker-payloads in the ADCs disclosed herein are surprisingly effective with different tumor antigen-targeting antibodies. Suitable antigens expressed on tumor cells but not healthy cells, or expressed on tumor cells at a higher level than on healthy cells, are known in the art, as are antibodies directed against them. These antibodies may be used with the linkers and herboxidiene splicing modulator payloads disclosed herein. In some embodiments, the antibody or antigen binding fragment targets HER2, and the HER2-targeting antibody or antigen binding fragment is trastuzumab. In some embodiments, the antibody or antigen binding fragment targets CD138, and the CD138-targeting antibody or antigen binding fragment is B-B4. In some embodiments, the antibody or antigen binding fragment targets EPHA2, and the EPHA2-targeting antibody or antigen binding fragment is 1C1. In some embodiments, while the disclosed linkers and herboxidiene splicing modulator payloads are surprisingly effective with several different tumor-targeting antibodies, HER2-targeting antibodies such as trastuzumab, CD138-targeting antibodies such as B-B4, and EPHA2-targeting antibodies such as 1C1 provided particularly improved drug:antibody ratio, aggregation level, stability (i.e. , in vitro and invivo stability), tumor targeting (i.e. , cytotoxicity, potency), and / or treatment efficacy. Improved treatment efficacy can be measured in vitro or in vivo, and may include reduced tumor growth rate and / or reduced tumor volume.

[0242] In certain embodiments, alternate antibodies to the same targets or antibodies to different antigen targets are used and provide at least some of the favorable functional properties described above (e.g., improved stability, improved tumor targeting, improved treatment efficacy, etc.). In some embodiments, some or all of these favorable functional properties are observed when the disclosed linkers and herboxidiene splicing modulator payloads are conjugated to an alternate HER2-, CD138-, or EPHA2-targeting antibody or antigen binding fragment. In some other embodiments, some or all of these favorable functional properties are observed when the disclosed linkers and herboxidiene splicing modulator payloads are conjugated to a HER2-targeting antibody or antigen binding fragment. In some embodiments, the antibody or antigen binding fragment targets HER2. In some embodiments, the HER2-targeting antibody or antigen binding fragment is trastuzumab. In some other embodiments, some or all of these favorable functional properties are observed when the disclosed linkers and herboxidiene splicing modulator payloads are conjugated to a CD138- targeting antibody or antigen binding fragment. In some embodiments, the antibody or antigen binding fragment targets CD138. In some embodiments, the CD138-targeting antibody or antigen binding fragment is B-B4. In some other embodiments, some or all of these favorable functional properties are observed when the disclosed linkers and herboxidiene splicing modulator payloads are conjugated to an EPHA2-targeting antibody or antigen binding fragment. In some embodiments, the antibody or antigen binding fragment targets EPHA2. In some embodiments, the EPHA2-targeting antibody or antigen binding fragment is 1C1.Linkers

[0243] In various embodiments, the linker in an ADC is stable extracellularly in a sufficient manner to be therapeutically effective. In some embodiments, the linker is stable outside a cell, such that the ADC remains intact when present in extracellular conditions (e.g., prior to transport or delivery into a cell). The term“intact,” used in the context of an ADC, means that the antibody or antigen binding fragment remains attached to the drug moiety (e.g., the herboxidiene splicing modulator). As used herein,“stable,” in the context of a linker or ADC comprising a linker, means that no more than 20%, no more than about 15%, no more than about 10%, no more than about 5%, no more than about 3%, or no more than about 1 % of the linkers (or any percentage in between) in a sample of ADC are cleaved (or in the case of an overall ADC are otherwise not intact) when the ADC is present in extracellular conditions. In some embodiments, the linkers and / or ADCs disclosed herein are surprisingly stable compared to alternate linkers and / or ADCs with alternate linkers and / or herboxidiene splicing modulator payloads. In some embodiments, the ADCs disclosed herein can remain intact for more thanabout 48 hours, more than 60 hours, more than about 72 hours, more than about 84 hours, or more than about 96 hours.

[0244] Whether a linker is stable extracellularly can be determined, for example, by including an ADC in plasma for a predetermined time period (e.g., 2, 4, 6, 8, 16, 24, 48, or 72 hours) and then quantifying the amount of free drug moiety present in the plasma. Stability may allow the ADC time to localize to target tumor cells and prevent the premature release of the drug moiety, which could lower the therapeutic index of the ADC by indiscriminately damaging both normal and tumor tissues. In some embodiments, the linker is stable outside of a target cell and releases the drug moiety from the ADC once inside of the cell, such that the drug can bind to its target (e.g., to the SF3b spliceosome complex). Thus, an effective linker will: (i) maintain the specific binding properties of the antibody or antigen binding fragment; (ii) allow delivery, e.g., intracellular delivery, of the drug moiety via stable attachment to the antibody or antigen binding fragment; (iii) remain stable and intact until the ADC has been transported or delivered to its target site; and (iv) allow for the therapeutic effect, e.g., cytotoxic effect, of the drug moiety after cleavage or alternate release mechanism.

[0245] Linkers may impact the physico-chemical properties of an ADC. As many cytotoxic agents are hydrophobic in nature, linking them to the antibody with an additional hydrophobic moiety may lead to aggregation. ADC aggregates are insoluble and often limit achievable drug loading onto the antibody, which can negatively affect the potency of the ADC. Protein aggregates of biologies, in general, have also been linked to increased immunogenicity. As shown below, linkers disclosed herein result in ADCs with low aggregation levels and desirable levels of drug loading.

[0246] A linker may be "cleavable" or "non-cleavable" (Ducry and Stump (2010) Bioconjugate Chem. 21 :5-13). Cleavable linkers are designed to release the drug moiety (e.g., the herboxidiene splicing modulator) when subjected to certain environment factors, e.g., when internalized into the target cell, whereas non-cleavable linkers generally rely on the degradation of the antibody or antigen binding fragment itself.

[0247] In some embodiments, the linker is a non-cleavable linker. In some embodiments, the herboxidiene splicing modulator drug moiety of the ADC is released by degradation of the antibody or antigen binding fragment. Non-cleavable linkers tend to remain covalently associated with at least one amino acid of the antibody and the drug upon internalization by and degradation within the target cell. Numerous exemplary non-cleavable linkers are described herein, and others are known in the art. Exemplary non-cleavable linkers may comprise thioether, cyclohexyl, N-succinimidyl 4-(N-maleimidomethyl) cyclohexane-1 carboxylate(SMCC), or N-hydroxysuccinimide (NHS), one or more polyethylene glycol (PEG) moieties, e.g., 1 , 2, 3, 4, 5, or 6 PEG moieties, or one or more alkyl moieties.

[0248] In some embodiments, the linker is a cleavable linker. A cleavable linker refers to any linker that comprises a cleavable moiety. As used herein, the term“cleavable moiety” refers toany chemical bond that can be cleaved. Suitable cleavable chemical bonds are well known in the art and include, but are not limited to, acid labile bonds, protease / peptidase labile bonds, photolabile bonds, disulfide bonds, and esterase labile bonds. Linkers comprising a cleavable moiety can allow for the release of the herboxidiene splicing modulator drug moiety from the ADC via cleavage at a particular site in the linker.

[0249] In some embodiments, the linker is cleavable under intracellular conditions, such that cleavage of the linker sufficiently releases the herboxidiene splicing modulator drug moiety from the antibody or antigen binding fragment in the intracellular environment to activate the drug and / or render the drug therapeutically effective. In some embodiments, the herboxidiene splicing modulator drug moiety is not cleaved from the antibody or antigen binding fragment until the ADC enters a cell that expresses an antigen specific for the antibody or antigen binding fragment of the ADC, and the herboxidiene splicing modulator drug moiety is cleaved from the antibody or antigen binding fragment upon entering the cell. In some embodiments, the linker comprises a cleavable moiety that is positioned such that no part of the linker or the antibody or antigen binding fragment remains bound to the herboxidiene splicing modulator drug moiety upon cleavage. Exemplary cleavable linkers include acid labile linkers, protease / peptidase- sensitive linkers, photolabile linkers, dimethyl-, disulfide-, or sulfonamide-containing linkers.

[0250] In some embodiments, the linker is a pH-sensitive linker, and is sensitive to hydrolysis at certain pH values. Typically, the pH-sensitive linker is cleavable under acidic conditions. This cleavage strategy generally takes advantage of the lower pH in the endosomal (pH ~ 5-6) and lysosomal (pH ~ 4.8) intracellular compartments, as compared to the cytosol (pH ~ 7.4), to trigger hydrolysis of an acid labile group in the linker, such as a hydrazone (Jain et al. (2015) Pharm Res 32:3526-40). In some embodiments, the linker is an acid labile and / or hydrolyzable linker. For example, an acid labile linker that is hydrolyzable in the lysosome, and contains an acid labile group (e.g., a hydrazone, a semicarbazone, a thiosemicarbazone, a cis-aconitic amide, an orthoester, an acetal, a ketal, or the like) can be used. See, e.g., U.S. Pat. Nos. 5,122,368; 5,824,805; 5,622,929; Dubowchik and Walker (1999) Pharm Therapeutics 83:67- 123; Neville et al. (1989) Biol Chem. 264:14653-61. Such linkers are relatively stable under neutral pH conditions, such as those in the blood, but are unstable at below pH 5.5 or 5.0, the approximate pH of the lysosome. In certain embodiments, the hydrolyzable linker is a thioether linker (such as, e.g., a thioether attached to the therapeutic agent via an acylhydrazone bond) (see, e.g., U.S. Pat. No. 5,622,929).

[0251] In some embodiments, the linker is cleavable under reducing conditions. In some embodiments, the linker is cleavable in the presence of a reducing agent, such as glutathione or dithiothreitol. In some embodiments, the linker is a cleavable disulfide linker or a cleavable sulfonamide linker.

[0252] In some embodiments, the linker is a cleavable disulfide linker. A variety of disulfide linkers are known in the art, including, for example, those that can be formed using SATA (N-succinimidyl-5-acetylthioacetate), SPDP (N-succinimidyl-3-(2-pyridyldithio)propionate), SPDB (N-succinimidyl-3-(2-pyridyldithio)butyrate) and SMPT (N-succinimidyloxycarbonyl-alpha- methyl-alpha-(2-pyridyl-dithio)toluene), SPDB and SMPT. See, e.g., Thorpe et al. (1987)Cancer Res. 47:5924-31 ; Wawrzynczak et al., In Immunoconjugates: Antibody Conjugates in Radioimagery and Therapy of Cancer (C. W. Vogel ed., Oxford U. Press, 1987). See also U.S. Pat. No. 4,880,935. Disulfide linkers are typically used to exploit the abundance of intracellular thiols, which can facilitate the cleavage of their disulfide bonds. The intracellular concentrations of the most abundance intracellular thiol, reduced glutathione, are generally in the range of 1-10 nM, which is about 1 ,000-fold higher than that of the most abundant low-molecular thiol in the blood (i.e. , cysteine) at about 5 mM (Goldmacher et al., In Cancer Drug Discovery andDevelopment: Antibody-Drug Conjugates and Immunotoxins (G. L. Phillips ed., Springer,2013)). The intracellular enzymes of the protein disulfide isomerase family may also contribute to the intracellular cleavage of a disulfide linker. As used herein, a cleavable disulfide linker refers to any linker that comprises a cleavable disulfide moiety. The term“cleavable disulfide moiety” refers to a disulfide bond that can be cleaved and / or reduced, e.g., by a thiol or enzyme.

[0253] In some embodiments, the linker is a cleavable sulfonamide linker. As used herein, a cleavable sulfonamide linker refers to any linker that comprises a cleavable sulfonamide moiety. The term“cleavable sulfonamide moiety” refers to a sulfonamide group, i.e., sulfonyl group connected to an amine group, wherein the sulfur-nitrogen bond can be cleaved.

[0254] In some embodiments, the linker may be a dendritic type linker for covalent attachment of more than one drug moiety to an antibody or antigen binding fragment through a branching, multifunctional linker moiety. See, e.g., Sun et al. (2002) Bioorg Med Chem Lett. 12:2213-5;Sun et al. (2003) Bioorg Med Chem. 11 :1761-8. Dendritic linkers can increase the molar ratio of drug to antibody, i.e., drug loading, which is related to the potency of the ADC. Thus, where an antibody or antigen binding fragment bears only one reactive cysteine thiol group, for example, a multitude of herboxidiene splicing modulator drug moieties may be attached through a dendritic linker. In some embodiments, the linker moiety or linker-drug moiety may be attached to the antibody or antigen binding fragment via reduced disulfide bridging chemistry or limited lysine utilization technology. See, e.g., Inti. Publ. Nos. WO 2013 / 173391 and WO 2013 / 173393.

[0255] In some embodiments, the linker is cleavable by a cleaving agent, e.g., an enzyme, that is present in the intracellular environment (e.g., within a lysosome or endosome or caveola).The linker can be, e.g., a peptide linker that is cleaved by an intracellular peptidase or protease enzyme, including, but not limited to, a lysosomal or endosomal protease.

[0256] In some embodiments, the linker is a cleavable peptide linker. As used herein, a cleavable peptide linker refers to any linker that comprises a cleavable peptide moiety. The term“cleavable peptide moiety” refers to any chemical bond linking amino acids (natural or synthetic amino acid derivatives) that can be cleaved by an agent that is present in the intracellular environment. For instance, a linker may comprise a valine-alanine (Val-Ala)sequence, or a valine-citrulline (Val-Cit) sequence that is cleavable by a peptidase such as cathepsin, e.g., cathepsin B. In some embodiments, a linker may comprise a glutamic acid- valine-citrulline sequence (Glu-Val-Cit). In some embodiments, the linker is an enzyme- cleavable linker and a cleavable peptide moiety in the linker is cleavable by the enzyme. In some embodiments, the cleavable peptide moiety is cleavable by a lysosomal enzyme, e.g., cathepsin. In some embodiments, the linker is a cathepsin-cleavable linker. In someembodiments, the cleavable peptide moiety in the linker is cleavable by a lysosomal cysteine cathepsin, such as cathepsin B, C, F, H, K, L, O, S, V, X, or W. In some embodiments, the cleavable peptide moiety is cleavable by cathepsin B. An exemplary dipeptide that may be cleaved by cathepsin B is valine-citrulline (Val-Cit) (Dubowchik et al. (2002) Bioconjugate Chem. 13:855-69).

[0257] In some embodiments, the linker or the cleavable peptide moiety in the linker comprises an amino acid unit. In some embodiments, the amino acid unit allows for cleavage of the linker by a protease, thereby facilitating release of the herboxidiene splicing modulator drug moiety from the ADC upon exposure to one or more intracellular proteases, such as one or more lysosomal enzymes (Doronina et al. (2003) Nat Biotechnol. 21 :778-84; Dubowchik and Walker (1999) Pharm Therapeutics 83:67-123). Exemplary amino acid units include, but are not limited to, dipeptides, tripeptides, tetrapeptides, and pentapeptides. Exemplary dipeptides include, but are not limited to, valine-alanine (Val-Ala), valine-citrulline (Val-Cit), alanine-asparagine (Ala- Asn), alanine-phenylalanine (Ala-Phe), phenylalanine-lysine (Phe-Lys), alanine-lysine (Ala-Lys), alanine-valine (Ala-Val), valine-lysine (Val-Lys), lysine-lysine (Lys-Lys), phenylalanine-citrulline (Phe-Cit), leucine-citrulline (Leu-Cit), isoleucine-citrulline (lle-Cit), tryptophan-citrulline (Trp-Cit), and phenylalanine-alanine (Phe-Ala). Exemplary tripeptides include, but are not limited to, alanine-alanine-asparagine (Ala-Ala-Asn), glycine-valine-citrulline (Gly-Val-Cit), glycine-glycine- glycine (Gly-Gly-Gly), phenylalanine-phenylalanine-lysine (Phe-Phe-Lys), glutamic acid-valine- citrulline (Glu-Val-Cit) (see Anami et al. (2018) Nat. Comm. 9:2512) and glycine-phenylalanine- lysine (Gly-Phe-Lys). Other exemplary amino acid units include, but are not limited to, Gly-Phe- Gly-Gly (SEQ ID NO:34), Gly-Phe-Leu-Gly (SEQ ID NO:35), Ala-Leu-Ala-Leu (SEQ ID NO:36), Phe-N9-tosyl-Arg, and Phe-N9-Nitro-Arg, as described in, e.g., U.S. Pat. No. 6,214,345. In some embodiments, the amino acid unit in the linker comprises Val-Ala. In some embodiments, the amino acid unit in the linker comprises Val-Cit. In some embodiments, the amino acid unit in the linker comprises Glu-Val-Cit. An amino acid unit may comprise amino acid residues that occur naturally and / or minor amino acids and / or non-naturally occurring amino acid analogs, such as citrulline. Amino acid units can be designed and optimized for enzymatic cleavage by a particular enzyme, for example, a tumor-associated protease, a lysosomal protease such as cathepsin B, C, D, or S, or a plasmin protease.

[0258] In some embodiments, the linker is a cleavable b-glucuronide linker. As used herein, a cleavable b-glucuronide linker refers to any linker that comprises a cleavable b-glucuronide moiety. An exemplary cleavable b-glucuronide linker comprises the structure:

[0259] The term“cleavable b-glucuronide moiety” refers to a glycosidic bond that can be cleaved by an agent having b-glucuronidase activity. In some embodiments, the linker comprises a glycosidic bond that can be cleaved by a b-glucuronidase. A b-glucuronidase is a UDP-glucuronosyl transferase that catalyzes the hydrolysis of the glycosidic bond of glucuronides with b-configuration.

[0260] In some embodiments, an ADC disclosed herein comprises a cleavable b-glucuronide moiety in the linker that is cleavable by the enzyme. In some embodiments, the cleavable b- glucuronide moiety in the linker is cleavable by a lysosomal enzyme, e.g., a b-glucuronidase. In some embodiments, the linker is a b-glucuronidase-cleavable linker. In some embodiments, the cleavable b-glucuronide moiety in the linker allows for cleavage of the linker by a b- glucuronidase after internalization of the ADC, thereby facilitating release of the drug moiety from the ADC in the cellular environment.

[0261] In some embodiments, the linker in any of the ADCs disclosed herein may comprise at least one spacer unit joining the antibody or antigen binding fragment to the drug moiety (e.g., the herboxidiene splicing modulator drug moiety). In some embodiments, a spacer unit between the antibody or antigen binding fragment and cleavable moiety, when present, joins a cleavage site (e.g., a cleavable peptide moiety) in the linker to the antibody or antigen binding fragment. In some embodiments, a spacer unit between the drug moiety and cleavable moiety, when present, joins a cleavage site (e.g., a cleavable peptide moiety) in the linker to the drug moiety. In some embodiments, no cleavage site is present, and the spacer unit is used to link the antibody or antigen binding fragment to the drug moiety.

[0262] In some embodiments, the linker, and / or spacer unit in the linker, is substantially hydrophilic. A hydrophilic linker may be used to reduce the extent to which the drug may be pumped out of resistant cancer cells through multiple drug resistance (MDR) or functionally similar transporters. In some embodiments, a hydrophilic linker may include one or more polyethylene glycol (PEG) moieties, e.g., 1 , 2, 3, 4, 5, or 6 PEG moieties. In someembodiments, the linker comprises 2 PEG moieties.

[0263] In some embodiments, the spacer unit in the linker comprises one or more PEG moieties. In some embodiments, the spacer unit comprises one or more -(PEG)m-, and m is aninteger from 1 to 10 (i.e., m may be 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10). In some embodiments, m ranges from 1 to 10; from 2 to 8; from 2 to 6; from 2 to 5; from 2 to 4; or from 2 to 3. In some embodiments, m is 2. In some embodiments, the spacer unit comprises (PEG)2, (PEG)3,(PEG)4, (PEG)S, (PEG)e, (PEG) , (PEG)8, (PEG)e, or (PEG)10. In some embodiments, the spacer unit comprises (PEG)2.

[0264] In some embodiments, the spacer unit in the linker comprises an alkyl moiety. In some embodiments, the spacer unit comprises one or more -(CH2)n-, and n is an integer from 1 to 10 (i.e., n may be 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10). In some embodiments, n ranges from 1 to 10; from 2 to 8; from 2 to 6; from 2 to 5; from 2 to 4; or from 2 to 3. In some embodiments, n is 2. In some embodiments, n is 5. In some embodiments, n is 6. In some embodiments, the spacer unit comprises (CH2)2, (CH2)3, (CH2)4, (CH2)5, (CH2)6, (CH2)7, (CH2)8, (CH2)9, or (CH2)IO- In some embodiments, the spacer unit comprises (CH2)2 (“Et”). In some embodiments, the spacer unit comprises (CH2)6(“Hex”). In some embodiments, the spacer unit comprises (CH2)2-0-(CH2)2(“Et-O-Et”).

[0265] A spacer unit may be used, for example, to link the antibody or antigen binding fragment to the drug moiety, either directly or indirectly. In some embodiments, the spacer unit links the antibody or antigen binding fragment to the herboxidiene splicing modulator drug moiety directly. In some embodiments, the antibody or antigen binding fragment and the herboxidiene splicing modulator drug moiety are attached via a spacer unit comprising one or more PEG moieties (e.g., (PEG)2), or one or more alkyl moieties (e.g., (CH2)2, (CH2)6, or (CH2)2-0-(CH2)2).In some embodiments, the spacer unit links the antibody or antigen binding fragment to the herboxidiene splicing modulator drug moiety indirectly. In some embodiments, the spacer unit links the antibody or antigen binding fragment to the herboxidiene splicing modulator drug moiety indirectly through a cleavable moiety (e.g., a cleavable peptide or a cleavable b- glucuronide) and / or an attachment moiety to join the spacer unit to the antibody or antigen binding fragment, e.g., a maleimide moiety.

[0266] The spacer unit, in various embodiments, attaches to the antibody or antigen binding fragment (i.e., the antibody or antigen binding fragment) via a maleimide (Mai) moiety.

[0267] A spacer unit that attaches to the antibody or antigen binding fragment via a Mai is referred to herein as a“Mal-spacer unit.” The term“Mai” or“maleimide moiety,” as used herein, means a compound that contains a maleimide group and that is reactive with a sulfhydryl group, e.g., a sulfhydryl group of a cysteine residue on the antibody or antigen binding fragment. Other functional groups that are reactive with sulfhydryl groups (thiols) include, but are not limited to, iodoacetamide, bromoacetamide, vinyl pyridine, disulfide, pyridyl disulfide, isocyanate, and isothiocyanate. In some embodiments, the Mal-spacer unit is reactive with a cysteine residue on the antibody or antigen binding fragment. In some embodiments, the Mal-spacer unit is joined to the antibody or antigen binding fragment via the cysteine residue. In someembodiments, the Mal-spacer unit comprises a PEG moiety. In some embodiments, the Mal- spacer unit comprises an alkyl moiety.

[0268] In certain embodiments, the linker comprises the Mal-spacer unit and a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the amino acid unit comprises Val-Cit. In some embodiments, the amino acid unit comprises Val-Ala. In some embodiments, the amino acid unit comprises Glu- Val-Cit. In some embodiments, the linker comprises the Mal-spacer unit and Val-Cit. In some embodiments, the linker comprises the Mal-spacer unit and Val-Ala. In some embodiments, the linker comprises the Mal-spacer unit and Val-Cit, wherein the Mal-spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises the Mal-spacer unit and Val-Ala, wherein the Mal-spacer unit comprises a maleimidocaproyl (MC). In someembodiments, the linker comprises the Mal-spacer unit and a cleavable b-glucuronide moiety.

[0269] In some embodiments, the linker comprises the structure: Mal-spacer unit. In some embodiments, the Mal-spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises the structure: MC. In some embodiments, the linker comprises the structure: Mal-(CH2)2 (“Mal-Et”). In some embodiments, the linker comprises the structure: Mal- (CH2)6(“Mai-Hex”). In some embodiments, the linker comprises the structure: Mal-(CH2)2-0- (CH2)2(“Mal-Et-O-Et”). In some embodiments, the linker comprises the structure: Mal-(PEG)2.In some embodiments, the linker comprises the structure: Mal-(PEG)2-CO.

[0270] In various embodiments, the Mal-spacer unit attaches the antibody or antigen binding fragment to a cleavable peptide moiety. In some embodiments, the linker comprises Mal-spacer unit-peptide. In some embodiments, the linker comprises the structure: Mal-spacer unit-Val-Cit. In some embodiments, the Mal-spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises the structure: MC-Val-Cit.

[0271] In some embodiments, the linker comprises the structure: Mal-spacer unit-Val-Ala. In some embodiments, the Mal-spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises the structure: MC-Val-Ala.

[0272] In various embodiments, the Mal-spacer unit attaches the antibody or antigen binding fragment to a cleavable b-glucuronide moiety. In some embodiments, the linker comprises Mal- spacer unit^-glucuronide. In some embodiments, the linker comprises MC^-glucuronide.

[0273] In various embodiments, the cleavable moiety in the linker is joined directly to the herboxidiene splicing modulator drug moiety. In other embodiments, a spacer unit is used to attach the cleavable moiety in the linker to the herboxidiene splicing modulator drug moiety. In various embodiments, the herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a spacer unit.

[0274] A spacer unit may be "self-immolative" or "non-self-immolative." A "non-self-immolative" spacer unit is one in which part or all of the spacer unit remains bound to the herboxidiene splicing modulator drug moiety upon cleavage of the linker. Examples of non-self-immolativespacer units include, but are not limited to, a glycine spacer unit and a glycine-glycine spacer unit. Non-self-immolative spacer units may eventually degrade over time but do not readily release a linked native drug moiety entirely under cellular conditions. A "self-immolative" spacer unit allows for release of the native drug moiety under intracellular conditions. A“native drug” or “native drug moiety” is one where no part of the spacer unit or other chemical modification remains after cleavage / degradation of the spacer unit.

[0275] Self-immolation chemistry is known in the art and could be readily selected for the disclosed ADCs. In various embodiments, the spacer unit attaching the cleavable moiety in the linker to the herboxidiene splicing modulator drug moiety is self-immolative, and undergoes self- immolation concurrently with or shortly before / after cleavage of the cleavable moiety under intracellular conditions. In some embodiments, the herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a self-immolative spacer unit. In certain embodiments, the herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a self- immolative spacer unit, the cleavable moiety comprises Val-Cit, and a maleimidocaproyl (MC) joins the cleavable moiety to the antibody or antigen binding fragment. In certain embodiments, the herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a self- immolative spacer unit, the cleavable moiety comprises Val-Ala, and a maleimidocaproyl (MC) joins the cleavable moiety to the antibody or antigen binding fragment. In certain embodiments, the herboxidiene herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a self-immolative spacer unit, the cleavable moiety comprises Glu-Val-Cit, and a maleimidocaproyl (MC) joins the cleavable moiety to the antibody or antigen binding fragment.In certain embodiments, the herboxidiene splicing modulator is joined to the antibody or antigen binding fragment via a Mal-spacer unit (e.g., MC) in the linker joined to a Val-Cit cleavable moiety and a pABC or pAB self-immolative spacer unit. In certain other embodiments, the herboxidiene splicing modulator is joined to the antibody or antigen binding fragment via a Mal- spacer unit (e.g., MC) in the linker joined to a Val-Ala cleavable moiety and a pABC or pAB self- immolative spacer unit. In certain other embodiments, the herboxidiene splicing modulator is joined to the antibody or antigen binding fragment via a Mal-spacer unit (e.g., MC) in the linker joined to a Glu-Val-Cit cleavable moiety and a pABC or pAB self-immolative spacer unit.

[0276] In certain embodiments, the self-immolative spacer unit in the linker comprises a p- aminobenzyl unit. In some embodiments, a p-aminobenzyl alcohol (pABOH) is attached to an amino acid unit or other cleavable moiety in the linker via an amide bond, and a carbamate, methylcarbamate, or carbonate is made between the pABOH and the drug moiety (Hamann et al. (2005) Expert Opin Ther Patents 15:1087-103). In some embodiments, the self-immolative spacer unit is or comprises p-aminobenzyloxycarbonyl (pABC). Without being bound by theory, it is thought that the self-immolation of pABC involves a spontaneous 1 ,6-elimination reaction (Jain et al. (2015) Pharm Res. 32:3526-40).

[0277] In various embodiments, the structure of the p-aminobenzyloxycarbonyl (pABC) used in the disclosed ADCs is shown below:

[0278] In various embodiments, the self-immolative spacer unit attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, the self-immolative spacer unit is pABC. In some embodiments, the pABC attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, the pABC undergoes self- immolation upon cleavage of the cleavable moiety, and the herboxidiene splicing modulator is released from the ADC in its native, active form.

[0279] In some embodiments, an anti-HER2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Cit-pABC. In other embodiments, an anti-HER2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Ala-pABC.

[0280] In some embodiments, an anti-CD138 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Cit-pABC. In other embodiments, an anti-CD138 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Ala-pABC.

[0281] In some embodiments, an anti-EPHA2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Cit-pABC. In other embodiments, an anti-EPHA2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Ala-pABC.

[0282] In some embodiments, the pABC undergoes self-immolation upon cleavage of a cleavable peptide moiety in the linker. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the linker comprises amino acid unit- pABC. In some embodiments, the amino acid unit is Val-Cit. In some embodiments, the linker comprises Val-Cit-pABC. In some embodiments, the amino acid unit is Glu-Val-Cit. In some embodiments, the liker comprises Glu-Val-Cit-pABC. In some embodiments, the amino acid unit is Val-Ala. In some embodiments, the linker comprises Val-Ala-pABC. In someembodiments, the amino acid unit is Ala-Ala-Asn. In some embodiments, the linker comprises Ala-Ala-Asn-pABC.

[0283] In some embodiments, the pABC undergoes self-immolation upon cleavage of a cleavable b-glucuronide moiety in the linker. In some embodiments, the linker comprises b- glucuronide-pABC.

[0284] In certain embodiments, the self-immolative spacer unit in the linker comprises a p- aminobenzyl unit. In some embodiments, the self-immolative spacer unit in the linker comprisesa p-aminobenzyl (pAB). In some embodiments, the self-immolation of pAB involves a spontaneous 1 ,6-elimination reaction.

[0285] In various embodiments, the structure of the p-aminobenzyl (pAB) used in the disclosed ADCs is shown below:

[0286] In various embodiments, the self-immolative spacer unit attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, the self-immolative spacer unit is pAB. In some embodiments, the pAB attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, the pAB undergoes self- immolation upon cleavage of the cleavable moiety, and the herboxidiene splicing modulator is released from the ADC in its native, active form.

[0287] In some embodiments, an anti-HER2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Cit-pAB. In other embodiments, an anti-HER2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Ala-pAB.

[0288] In some embodiments, an anti-CD138 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Cit-pAB. In other embodiments, an anti-CD138 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Ala-pAB.

[0289] In some embodiments, an anti-EPHA2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Cit-pAB. In other embodiments, an anti-EPHA2 antibody or antigen binding fragment is joined to the herboxidiene splicing modulator by a linker comprising MC-Val-Ala-pAB.

[0290] In some embodiments, the pAB undergoes self-immolation upon cleavage of a cleavable peptide moiety in the linker. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the linker comprises amino acid unit-pAB. In some embodiments, the amino acid unit is Val-Cit. In some embodiments, the linker comprises Val- Cit-pAB. In some embodiments, the amino acid unit is Val-Ala. In some embodiments, the linker comprises Val-Ala-pAB. In some embodiments, the amino acid unit is Glu-Val-Cit. In some embodiments, the linker comprises Glu-Val-Cit-pAB. In some embodiments, the amino acid unit is Ala-Ala-Asn. In some embodiments, the linker comprises Ala-Ala-Asn-pAB.

[0291] In some embodiments, the pAB undergoes self-immolation upon cleavage of a cleavable b-glucuronide moiety in the linker. In some embodiments, the linker comprises b-glucuronide- pAB.

[0292] In some other embodiments, the herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a non-self-immolative spacer unit. In certain embodiments, the herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a non-self- immolative spacer unit, the cleavable moiety comprises Val-Cit, and a maleimidocaproyl (MC) joins the cleavable moiety to the antibody or antigen binding fragment. In certain embodiments, the herboxidiene splicing modulator is attached to the cleavable moiety in the linker by a non- self-immolative spacer unit, the cleavable moiety comprises Val-Ala, and a maleimidocaproyl (MC) joins the cleavable moiety to the antibody or antigen binding fragment.

[0293] In various aspects, the antibody or antigen binding fragment of the ADC is conjugated to the herboxidiene splicing modulator drug moiety via a linker, wherein the linker comprises a Mal-spacer unit (e.g., MC), a cleavable amino acid unit, and a pABC. In some embodiments, the spacer unit comprises an alkyl moiety. In some embodiments, the Mal-spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises Mal-spacer unit-amino acid unit-pABC. In some embodiments, the linker comprises MC-amino acid unit- pABC. In some embodiments, the linker comprises MC-Val-Cit-pABC. In some embodiments, the linker comprises MC-Val-Ala-pABC. In some embodiments, the linker comprises MC-Glu- Val-Cit-pABC. In some embodiments, the linker comprises MC-Ala-Ala-Asn-pABC.

[0294] In various other aspects, the antibody or antigen binding fragment of the ADC is conjugated to the herboxidiene splicing modulator drug moiety via a linker, wherein the linker comprises a Mal-spacer unit (e.g., MC), a cleavable amino acid unit, and a pAB. In some embodiments, the spacer unit comprises an alkyl moiety. In some embodiments, the Mal- spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises Mal-spacer unit-amino acid unit-pAB. In some embodiments, the linker comprises MC-amino acid unit-pAB. In some embodiments, the linker comprises MC-Val-Cit-pAB. In some embodiments, the linker comprises MC-Val-Ala-pAB. In some embodiments, the linker comprises MC-Glu-Val-Cit-pAB. In some embodiments, the linker comprises MC-Ala-Ala-Asn- pAB.

[0295] In various other aspects, the antibody or antigen binding fragment of the ADC is conjugated to the herboxidiene splicing modulator drug moiety via a linker, wherein the linker comprises a Mal-spacer unit (e.g., MC), a cleavable b-glucuronide, and a pABC. In some embodiments, the linker comprises Mal-spacer unit^-glucuronide-pABC. In someembodiments, the linker comprises MC^-glucuronide-pABC.

[0296] In still other aspects, the antibody or antigen binding fragment of the ADC is conjugated to the herboxidiene splicing modulator drug moiety via a linker, wherein the linker comprises a Mal-spacer unit (e.g., MC), a cleavable b-glucuronide, and a pAB. In some embodiments, the linker comprises Mal-spacer unit^-glucuronide-pAB. In some embodiments, the linker comprises MC^-glucuronide-pAB.

[0297] In various embodiments, the ADC compound has Formula (I):Ab-(L-H)p(I) wherein Ab is an antibody or antigen binding fragment which targets a neoplastic cell;H is a herboxidiene splicing modulator;L is a linker that covalently attaches Ab to D; andp is an integer from 1 to 15.

[0298] In some embodiments, the antibody or antigen binding fragment (Ab) of the ADC is conjugated to the herboxidiene splicing modulator drug moiety via a linker, wherein the linker is any of the linkers disclosed or incorporated by reference herein, or comprises one or more components of any of the linkers disclosed or incorporated by reference herein.

[0299] In some embodiments, the linker comprises a cleavable moiety that is positioned such that no part of the linker or the antibody or antigen binding fragment remains bound to the herboxidiene splicing modulator after cleavage. In some embodiments, the cleavable moiety is a cleavable peptide moiety, e.g., an amino acid unit such as Val-Cit or Val-Ala. In some embodiments, the amino acid unit or linker comprises Val-Cit. In some embodiments, the amino acid unit or linker comprises Val-Ala. In some embodiments, the amino acid unit or linker comprises Glu-Val-Cit.

[0300] In some embodiments, the linker comprises at least one spacer unit joining the antibody or antigen binding fragment to the cleavable moiety. In some embodiments, the linker comprises at least one spacer unit joining the antibody or antigen binding fragment to the drug moiety. In some embodiments, the spacer unit or linker comprises at least one alkyl moiety.

[0301] In some embodiments, a spacer unit in the linker attaches to the antibody or antigen binding fragment via a Mai moiety (“Mal-spacer unit”). In some embodiments, the Mal-spacer unit comprises at least one alkyl moiety. In some embodiments, the linker comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises Mal-(CH2)2 (“Mal-Et”). In some embodiments, the linker comprises Mal-(CH2)6 (“Mai-Hex”). In some embodiments, the linker comprises Mal-(CH2)2-0-(CH2)2(“Mal-Et-O-Et”). In some embodiments, the linker comprises Mal-(PEG)2-CO. In some embodiments, the Mal-spacer unit attaches the antibody or antigen binding fragment to the drug moiety.

[0302] In some embodiments, the Mal-spacer unit or linker comprises Mal-(PEG)2, Mal-(PEG)3, Mal-(PEG)4, Mal-(PEG)5, Mal-(PEG)6, Mal-(PEG)7, or Mal-(PEG)s. In some embodiments, the Mal-spacer unit or linker comprises Mal-(PEG)2. In some embodiments, the Mal-spacer unit or linker comprises Mal-(PEG)2-CO, Mal-(PEG)3-CO, Mal-(PEG)4-CO, Mal-(PEG)5-CO, Mal- (PEG)6-CO, Mal-(PEG)7-CO, or Mal-(PEG)8-CO. In some embodiments, the Mal-spacer unit or linker comprises Mal-(PEG)2-CO. In some embodiments, the Mal-spacer unit or linker comprises Mal-(PEG)2-CO and at least one additional spacer unit. In some embodiments, the Mal-(PEG)2-CO attaches the antibody or antigen binding fragment to the drug moiety. In someembodiments, linker comprises or consists of Mal-(PEG)2-CO. An example of a“Mal-(PEG)2- CO” linker is also referred to herein as“ADL2” or an“ADL2” linker.

[0303] In some embodiments, the Mal-spacer unit or linker comprises MC. In someembodiments, the Mal-spacer unit or linker comprises MC and at least one additional spacer unit. In some embodiments, the MC attaches the antibody or antigen binding fragment to the drug moiety. In some embodiments, the linker comprises or consists of MC. An example of an “MC” linker is also referred to herein as“ADL10” or an“ADL10” linker.

[0304] In some embodiments, the Mal-spacer unit or linker comprises Mal-(CH2)6 (“Mai-Hex”).In some embodiments, the Mal-spacer unit or linker comprises Mai-Hex and at least one additional spacer unit. In some embodiments, the Mai-Hex attaches the antibody or antigen binding fragment to the drug moiety. In some embodiments, the linker comprises Mai-Hex. An example of a“Mai-Hex” linker is also referred to herein as“ADL12” or an“ADL12” linker.

[0305] In some embodiments, the Mal-spacer unit or linker comprises Mal-(CH2)2 (“Mal-Et”). In some embodiments, the Mal-spacer unit or linker comprises Mal-Et and at least one additional spacer unit. In some embodiments, the Mal-Et attaches the antibody or antigen binding fragment to the drug moiety. In some embodiments, the linker comprises Mal-Et. An example of a“Mal-Et” linker is also referred to herein as“ADL14” or an“ADL14” linker.

[0306] In some embodiments, the Mal-spacer unit or linker comprises Mal-(CH2)2-0-(CH2)2(“Mal-Et-O-Et”). In some embodiments, the Mal-spacer unit or linker comprises Mal-Et-O-Et and at least one additional spacer unit. In some embodiments, the Mal-Et-O-Et attaches the antibody or antigen binding fragment to the drug moiety. In some embodiments, the linker comprises Mal-Et-O-Et. An example of a“Mal-Et-O-Et” linker is also referred to herein as “ADL15” or an“ADL15” linker.

[0307] In some other embodiments, the Mal-spacer unit attaches the antibody or antigen binding fragment to the cleavable moiety in the linker. In some embodiments, the cleavable moiety in the linker is a cleavable peptide moiety, e.g., an amino acid unit. In someembodiments, the cleavable peptide moiety is Val-Cit or Val-Ala. In some embodiments, the Mal-spacer unit or linker comprises MC. In some embodiments, the linker comprises MC-Val- Cit. In some embodiments, the linker comprises MC-Val-Ala. In some embodiments, the linker comprises MC-Glu-Val-Cit. In some embodiments, the linker comprises MC-Ala-Ala-Asn.

[0308] In some embodiments, a spacer unit attaches the cleavable moiety in the linker to the herboxidiene splicing modulator. In some embodiments, the spacer unit that attaches the cleavable moiety to the herboxidiene splicing modulator is self-immolative.

[0309] In some embodiments, the spacer unit comprises pABC. In some embodiments, the pABC attaches the cleavable moiety to the herboxidiene splicing modulator. In some embodiments, the cleavable moiety is a cleavable peptide moiety, e.g., an amino acid unit. In some embodiments, the linker comprises amino acid unit-pABC.

[0310] In some embodiments, the linker comprises Val-Cit-pABC. In some embodiments, the linker comprises Val-Cit-pABC and a MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC-Val-Cit-pABC. In some embodiments, the linker comprises MC-Val-Cit-pABC and at least one additional spacer unit. An example of an MC-Val-Cit-pABC linker is also referred to herein as“ADL1” or an “ADL1” linker.

[0311] In some embodiments, the linker comprises Val-Ala-pABC. In some embodiments, the linker comprises Val-Ala-pABC and a MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC-Val-Ala-pABC. In some embodiments, the linker comprises MC-Val-Ala-pABC and at least one additional spacer unit. An example of an MC-Val-Ala-pABC linker is also referred to herein as“ADL6” or an “ADL6” linker.

[0312] In some embodiments, the linker comprises Glu-Val-Cit-pABC. In some embodiments, the linker comprises Glu-Val-Cit-pABC and a MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC-Glu-Val- Cit-pABC. In some embodiments, the linker comprises MC-Glu-Val-Cit-pABC and at least one additional spacer unit. An example of an MC-Glu-Val-Cit-pABC linker is also referred to herein as“ADL23” or an“ADL23” linker.

[0313] In some embodiments, the linker comprises Ala-Ala-Asn-pABC. In some embodiments, the linker comprises Ala-Ala-Asn-pABC and a MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC-Ala-Ala- Asn-pABC. In some embodiments, the linker comprises MC-Ala-Ala-Asn-pABC and at least one additional spacer unit. An example of an MC-Ala-Ala-Asn-pABC linker is also referred to herein as“ADL21” or an“ADL21” linker.

[0314] In some other embodiments, the spacer unit comprises pAB. In some embodiments, the pAB attaches the cleavable moiety to the herboxidiene splicing modulator. In someembodiments, the cleavable moiety is a cleavable peptide moiety, e.g., an amino acid unit. In some embodiments, the linker comprises amino acid unit-pAB.

[0315] In some embodiments, the linker comprises Val-Ala-pAB. In some embodiments, the linker comprises Val-Ala-pAB and an MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC-Val-Ala-pAB. In some embodiments, the linker comprises MC-Val-Ala-pAB and at least one additional spacer unit. An example of an MC-Val-Ala-pAB linker is also referred to herein as“ADL5” or an“ADL5” linker.

[0316] In some embodiments, the linker comprises Val-Cit-pAB. In some embodiments, the linker comprises Val-Cit-pAB and an MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC-Val-Cit-pAB. In some embodiments, the linker comprises MC-Val-Cit-pAB and at least one additional spacerunit. An example of an MC-Val-Cit-pAB linker is also referred to herein as“ADL7” or an“ADL7” linker.

[0317] In some embodiments, the linker comprises b-glucuronide-pABC. In someembodiments, the linker comprises b-glucuronide-pABC and an MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC^-glucuronide-pABC. In some embodiments, the linker comprises MC^-glucuronide-pABC and at least one additional spacer unit. An example of an MC^-glucuronide-pABC is also referred to herein as“ADL13” or an“ADL13” linker.

[0318] In some embodiments, the linker comprises b-glucuronide-pAB. In some embodiments, the linker comprises b-glucuronide-pAB and an MC Mal-spacer unit joining the linker to the antibody or antigen binding fragment. In some embodiments, the linker comprises MC-b- glucuronide-pAB.

[0319] In some embodiments, the antibody or antigen binding fragment is conjugated to the herboxidiene splicing modulator drug moiety via an ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker. It has been discovered, in variousembodiments, that ADCs comprising an ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker and a herboxidiene splicing modulator drug moiety disclosed herein demonstrate desirable properties for a therapeutic ADC. In variousembodiments, these properties include, but are not limited to, effective levels of drug loading, low aggregation levels, stability under storage conditions or when in circulation in the body (e.g., serum stability), retained affinity for target-expressing cells comparable to unconjugated antibody, potent cytotoxicity against target-expressing cells, low levels of off-target cell killing, high levels of bystander killing, and / or effective in vivo anti-cancer activity, all as compared to ADCs using other linker-payloads. For instance, in various embodiments, ADCs comprising an ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker and a herboxidiene splicing modulator drug moiety disclosed herein exhibit an increased ability to inhibit growth and / or proliferation in target-expressing cells, as compared to ADCs using other linker-payloads (e.g., an ADL10 linker and a herboxidiene splicing modulator drug moiety). In various embodiments, ADCs comprising an ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker and a herboxidiene splicing modulator drug moiety disclosed herein exhibit surprisingly increased in vivo stability (e.g., plasma stability), as compared to other splicing modulator-based ADCs (e.g., a thailanstatin A-based ADC, for example, as reported in Puthenveetil et al. Bioconjugate Chem. (2016) 27:1880-8).

[0320] In some embodiments, the good or superior functional properties provided by the particular combination of an ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker and a herboxidiene splicing modulator drug moiety disclosed herein may be observed with the linker-payload conjugated to, e.g., an anti-HER2 antibody such as trastuzumab; an anti-CD138 antibody such as B-B4; or an anti-EPHA2 antibody such as 1C1.

[0321] In some embodiments, the ADC comprises ADL1-herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In someembodiments, the ADC comprises ADL2-herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In some embodiments, the ADC comprises ADL5-herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In some embodiments, the ADC comprises ADL6- herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In some embodiments, the ADC comprises ADL7-herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In some embodiments, the ADC comprises ADL12-herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In someembodiments, the ADC comprises ADL13-herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In some embodiments, the ADC comprises ADL14-herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell. In some embodiments, the ADC comprises ADL15- herboxidiene splicing modulator and an antibody or antigen binding fragment comprising an antibody or an antigen binding fragment thereof that retains the ability to target and internalize in a neoplastic cell.

[0322] In some embodiments, the ADC comprises ADL1-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL2-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL5-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL6-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL7-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL12-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In someembodiments, the ADC comprises ADL13-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL14-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL15-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell.

[0323] In some embodiments, the antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell is an internalizing antibody or internalizing antigen binding fragment. In some embodiments, the antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell comprises three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO:1 (HCDR1), SEQ ID NO:2 (HCDR2), and SEQ ID NO:3 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO:4 (LCDR1), SEQ ID NO:5 (LCDR2), and SEQ ID NO:6 (LCDR3).

[0324] In some embodiments, the ADC has Formula (I):Ab-(L-H)p(I) wherein:(i) Ab is an anti-HER2 antibody or antigen binding fragment thereof comprising three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO:1 (HCDR1), SEQ ID NO:2 (HCDR2), and SEQ ID NO:3 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO:4 (LCDR1), SEQ ID NO:5 (LCDR2), and SEQ ID NO:6 (LCDR3);(ii) H is a herboxidiene splicing modulator;(iii) L is a linker comprising ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23; and(iv) p is an integer from 1 to 15.

[0325] In some embodiments, the antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 19, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:20. In some embodiments, the antibody or antigen binding fragment thereof that targets a HER2-expressing neoplastic cell comprises a human lgG1 heavy chain constant domain and a human Ig kappa light chain constant domain. In some embodiments, the antibody is trastuzumab. In some embodiments, p is an integer from 1 to 10, from 2 to 8, or from 4 to 8. In some embodiments, p is 4. In some embodiments, p is 8.

[0326] In some embodiments, the ADC comprises ADL1-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplasticcell. In some embodiments, the ADC comprises ADL2-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.In some embodiments, the ADC comprises ADL5-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.In some embodiments, the ADC comprises ADL6-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.In some embodiments, the ADC comprises ADL7-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.In some embodiments, the ADC comprises ADL12-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.In some embodiments, the ADC comprises ADL13-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.In some embodiments, the ADC comprises ADL14-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.In some embodiments, the ADC comprises ADL15-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell.

[0327] In some embodiments, the antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell is an internalizing antibody or internalizing antigen binding fragment. In some embodiments, the antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell comprises three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO:7 (HCDR1), SEQ ID NO:8 (HCDR2), and SEQ ID NO:9 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 1 1 (LCDR2), and SEQ ID NO: 12 (LCDR3).

[0328] In some embodiments, the ADC has Formula (I):Ab-(L-H)p(I) wherein:(i) Ab is an anti-CD138 antibody or antigen binding fragment thereof comprising three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO:7 (HCDR1), SEQ ID NO:8 (HCDR2), and SEQ ID NO:9 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3);(ii) H is a herboxidiene splicing modulator;(iii) L is a linker comprising ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23; and(iv) p is an integer from 1 to 15.

[0329] In some embodiments, the antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:21 , and a light chain variable region comprising an amino acid sequence of SEQ ID NO:22. In some embodiments, the antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell comprises a murine lgG2a heavy chain constant domain and a murine Ig kappa light chain constant domain. In some embodiments, the antibody or antigen binding fragment thereof that targets a CD138-expressing neoplastic cell comprises a human lgG2a heavy chain constant domain and a human Ig kappa light chain constant domain. In some embodiments, the antibody is B-B4. In some embodiments, p is an integer from 1 to 10, from 2 to 8, or from 4 to 8. In some embodiments, p is 4. In some embodiments, p is 8.

[0330] In some embodiments, the ADC comprises ADL1-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL2-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL5-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL6-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL7-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL12-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL13-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL14-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell. In some embodiments, the ADC comprises ADL15-herboxidiene splicing modulator and an antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell.

[0331] In some embodiments, the antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell is an internalizing antibody or internalizing antigen binding fragment. In some embodiments, the antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell comprises three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO:13 (HCDR1), SEQ ID NO:14 (HCDR2), and SEQ ID NO:15 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO: 16 (LCDR1), SEQ ID NO:17 (LCDR2), and SEQ ID NO:18 (LCDR3).

[0332] In some embodiments, the ADC has Formula (I):Ab-(L-H)p(I) wherein:(i) Ab is an anti-EPHA2 antibody or antigen binding fragment thereof comprising three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO:13 (HCDR1), SEQ ID NO:14 (HCDR2), and SEQ ID NO:15 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO:16 (LCDR1), SEQ ID NO:17 (LCDR2), and SEQ ID NO:18 (LCDR3);(ii) H is a herboxidiene splicing modulator;(iii) L is a linker comprising ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13,ADL14, ADL15, ADL21 , or ADL23; and(iv) p is an integer from 1 to 15.

[0333] In some embodiments, the antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:23, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:24. In some embodiments, the antibody or antigen binding fragment thereof that targets an EPHA2-expressing neoplastic cell comprises a human lgG1 heavy chain constant domain and a human Ig kappa light chain constant domain. In some embodiments, the antibody is 1C1. In some embodiments, p is an integer from 1 to 10, from 2 to 8, or from 4 to 8. In some embodiments, p is 4. In some embodiments, p is 8.Herboxidiene Splicing Modulators

[0334] In some embodiments, the antibody-drug conjugate is an antibody-drug conjugate of Formula (I): Ab-(L-H)p, wherein Ab is an antibody or antigen binding fragment which targets a neoplastic cell; H is a herboxidiene splicing modulator; L is a linker which covalently attaches Ab to H; and p is an integer from 1 to 15.

[0335] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formulapharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:Y is chosen from O, S, NR6, and CR6R7;R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R4is chosen from hydrogen, C1-C6 alkyl groups, -C(=0)-(Ci-C6alkyl) groups, -C(=0)- (C3-C8 carbocyclyl) groups, -C(=0)-(C3-C8heterocyclyl) groups, and -C(=Q)-NR6R7;R5is chosen from hydrogen, hydroxyl, -CH2-OH, -CO2H, -C(=0)-0-(Ci-C6alkyl) groups, -C(=0)-NR6R7, -NR6-C(=0)-R8, -0-C(=0)-NR6R7, -NR6-C(=0)-R8, and -NR6-C(=0)-NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)- O-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R1, R2, R3, R4, R5, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, -CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, C1-C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl), andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0336] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (la):pharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:R9is chosen from C3-C8 heterocyclyl groups;R10is chosen from H and C1-C6 alkyl groups,wherein R9and R10are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, -IMH2, -NH-(CI-C3 alkyl), and -N-(CI-C3 alkyl)2, andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0337] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formulapharmaceutically

[0338] acceptable salt thereof, which covalently attaches to L through any atom, wherein:R11is chosen fromwherein * denotes the point of connectivity of R11to the remainder of the compound;R12and R13are each independently chosen from H and methyl; andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0339] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (II):(II), or a pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:X is hydroxyl or NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, -C(=0)-0-R8, -(Ci-C6alkyl)-0-C(=0)-R8, and -(Ci-C6alkyl)-NH-C(=0)-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, C1-C6 alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3alkyl), and -NH-C(=0)-0-(CI-C3alkyl), andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0340] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (I la):la), or apharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:Z is chosen from NR9and O;R9is chosen from hydrogen and C1-C6 alkyl groups;R10and R11are each independently chosen from hydrogen, halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-Ce alkyl) groups, -CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, C3-C8carbocyclyl groups, CrCe alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups;R12is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, C3-C8 heterocyclyl groups,wherein R9, R10, R11, and R12are each independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, and C1 -C3 haloalkyl groups;t is an integer chosen from 1 , 2, 3, 4, 5, and 6; andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0341] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formula (lib):(lib), or a pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:, wherein * denotes the point of connectivity of R13to the remainder of the compound;R14and R15are each independently chosen from hydrogen and methyl; andwherein the valency of the atom that is covalently attached to L is not exceeded.

[0342] In some embodiments, H, the herboxidiene splicing modulator, comprises a compoundof Formulapharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)-O-R8;R8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups; andwherein R1, R2, R3, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-C8 carbocyclyl) groups, -C(=0)-(C3-C8 heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl),wherein the valency of the atom that is covalently attached to L is not exceeded; and wherein * denotes the point of connectivity of R9to the remainder of the compound.

[0343] In some embodiments, the antibody or antigen binding fragment targets a cell expressing HER2, CD138, EPHA2, MSLN, FOLH1 , CDH6, CEACAM5, CFC1 B, ENPP3,FOLR1 , HAVCR1 , KIT, MET, MUC16, SLC39A6, SLC44A4, and / or STEAP1.

[0344] In some embodiments, the antibody or antigen binding fragment targets a HER2- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- HER2 antibody or antigen binding fragment. In some embodiments, the antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO:1 (HCDR1), SEQ ID NO:2 (HCDR2), and SEQ ID NO:3 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO:4 (LCDR1), SEQ ID NO:5 (LCDR2), and SEQ ID NO:6 (LCDR3). In some embodiments, the antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 19, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:20. In some embodiments, the antibody or antigen binding fragment comprises a human lgG1 heavy chain constant region. In some embodiments, the antibody or antigen binding fragment comprises a human Ig kappa light chain constant region.

[0345] In some other embodiments, the antibody or antigen binding fragment targets a CD138- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- CD138 antibody or antigen binding fragment. In some embodiments, the antibody or antigenbinding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO:7 (HCDR1), SEQ ID NO:8 (HCDR2), and SEQ ID NO:9 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO:11 (LCDR2), and SEQ ID NO:12 (LCDR3). In some embodiments, the antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:21 , and a light chain variable region comprising an amino acid sequence of SEQ ID NO:22. In some embodiments, the antibody or antigen binding fragment comprises a murine lgG2a heavy chain constant region. In some embodiments, the antibody or antigen binding fragment comprises a murine Ig kappa light chain constant region.In some embodiments, the antibody or antigen binding fragment comprises a human lgG2a heavy chain constant region. In some embodiments, the antibody or antigen binding fragment comprises a human Ig kappa light chain constant region.

[0346] In some other embodiments, the antibody or antigen binding fragment targets an EPHA2-expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-EPHA2 antibody or antigen binding fragment. In some embodiments, the antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO:13 (HCDR1), SEQ ID NO:14 (HCDR2), and SEQ ID NO:15 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO:16 (LCDR1), SEQ ID NO:17 (LCDR2), and SEQ ID NO:18 (LCDR3). In some embodiments, the antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:23, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:24. In some embodiments, the antibody or antigen binding fragment comprises a human lgG1 heavy chain constant region. In some embodiments, the antibody or antigen binding fragment comprises a human Ig kappa light chain constant region.

[0347] In some other embodiments, the antibody or antigen binding fragment targets a MSLN- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- MSLN antibody or antigen binding fragment.

[0348] In some other embodiments, the antibody or antigen binding fragment targets a FOLH1- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- FOLH1 antibody or antigen binding fragment.

[0349] In some other embodiments, the antibody or antigen binding fragment targets a CDH6- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- CDH6 antibody or antigen binding fragment.

[0350] In some other embodiments, the antibody or antigen binding fragment targets aCEACAM5-expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-CEACAM5 antibody or antigen binding fragment.

[0351] In some other embodiments, the antibody or antigen binding fragment targets a CFC1 B- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- CFC1 B antibody or antigen binding fragment.

[0352] In some other embodiments, the antibody or antigen binding fragment targets an ENPP3-expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-ENPP3 antibody or antigen binding fragment.

[0353] In some other embodiments, the antibody or antigen binding fragment targets a FOLR1- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- FOLR1 antibody or antigen binding fragment.

[0354] In some other embodiments, the antibody or antigen binding fragment targets aHAVCRI-expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-HAVCR1 antibody or antigen binding fragment.

[0355] In some other embodiments, the antibody or antigen binding fragment targets a KIT- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-KIT antibody or antigen binding fragment.

[0356] In some other embodiments, the antibody or antigen binding fragment targets a MET- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-MET antibody or antigen binding fragment.

[0357] In some other embodiments, the antibody or antigen binding fragment targets a MUC16- expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti- MUC16 antibody or antigen binding fragment.

[0358] In some other embodiments, the antibody or antigen binding fragment targets aSLC39A6-expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-SLC39A6 antibody or antigen binding fragment.

[0359] In some other embodiments, the antibody or antigen binding fragment targets aSLC44A4-expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-SLC44A4 antibody or antigen binding fragment.

[0360] In some other embodiments, the antibody or antigen binding fragment targets aSTEAPI-expressing cell. In some embodiments, the antibody or antigen binding fragment is an anti-STEAP1 antibody or antigen binding fragment.

[0361] In some embodiments, L is selected from any of the linkers disclosed herein, or any combination of linker components disclosed herein. In some embodiments, L is a linker comprising MC-Val-Cit-pABC, Mal-(PEG)2-CO, MC-Val-Ala-pAB, MC-Val-Ala-pABC, MC-Val- Cit-pAB, Mai-Hex, Mal-Et, or Mal-Et-O-Et. In some embodiments, the linker may also comprise one or more additional spacer units. In some embodiments, L is an ADL1 , ADL2, ADL5, ADL6,ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker. In some embodiments, L is an ADL12, ADL14, or ADL15 linker. In some embodiments, the ADL1 , ADL2, ADL5, ADL6, ADL7, ADL12, ADL13, ADL14, ADL15, ADL21 , or ADL23 linker may also comprise one or more additional spacer units.

[0362] In certain embodiments, an intermediate, which is the precursor of the linker moiety, is reacted with the herboxidiene splicing modulator moiety under appropriate conditions. In certain embodiments, reactive groups are used on the herboxidiene splicing modulator and / or the intermediate or linker. The product of the reaction between the herboxidiene splicing modulator and the intermediate, or the derivatized herboxidiene splicing modulator(herboxidiene splicing modulator plus linker), is subsequently reacted with the antibody or antigen binding fragment under appropriate conditions. Alternatively, the intermediate or linker may first be reacted with the antibody or antigen binding fragment, or a derivatized antibody or antigen binding fragment, and then reacted with the drug or derivatized drug.

[0363] A number of different reactions are available for covalent attachment of the herboxidiene splicing modulator moiety and / or linker moiety to the antibody or antigen binding fragment. This is often accomplished by reaction of one or more amino acid residues of the antibody or antigen binding fragment, including the amine groups of lysine, the free carboxylic acid groups of glutamic acid and aspartic acid, the sulfhydryl groups of cysteine, and the various moieties of the aromatic amino acids. For instance, non-specific covalent attachment may be undertaken using a carbodiimide reaction to link a carboxy (or amino) group on a herboxidiene splicing modulator moiety to an amino (or carboxy) group on an antibody or antigen binding fragment. Additionally, bifunctional agents such as dialdehydes or imidoesters may also be used to link the amino group on a herboxidiene splicing modulator moiety to an amino group on an antibody or antigen binding fragment. Also available for attachment of drugs (e.g., a herboxidiene splicing modulator) to binding agents is the Schiff base reaction. This method involves the periodate oxidation of a drug that contains glycol or hydroxy groups, thus forming an aldehyde which is then reacted with the binding agent. Attachment occurs via formation of a Schiff base with amino groups of the binding agent. Isothiocyanates may also be used as coupling agents for covalently attaching drugs to binding agents. Other techniques are known to the skilled artisan and within the scope of the present disclosure. Examples of drug moieties that can be generated and linked to an antibody or antigen binding fragment using various chemistries known to in the art include herboxidiene splicing modulators, e.g., the herboxidiene splicing modulators described and exemplified herein.Linker-Herboxidiene Splicing Modulator / Herboxidiene Splicing Modulator Compounds

[0364] Further disclosed herein are exemplary linker-herboxidiene splicing modulator (L-H) compounds, as well as compositions comprising multiple copies of such compounds. In various embodiments, the linker-herboxidiene splicing modulator compounds disclosed herein can be defined by the generic formula: L-H, wherein L= a linker moiety, and H = a herboxidiene splicingmodulator. In certain embodiments, the disclosed L-H compounds are suitable for use in the ADCs described herein.

[0365] In some embodiments, disclosed herein, are compounds of Formula (I):pharmaceutically acceptable salt thereof, wherein:Y is chosen from O, S, NR6, and CR6R7;R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R4is chosen from hydrogen, C1-C6 alkyl groups, -C(=0)-(Ci-C6alkyl) groups, -C(=0)- (C3-C8 carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, and -C(=0)-NR6R7;R5is chosen from hydrogen, hydroxyl, -CH2-OH, -CO2H, -C(=0)-0-(Ci-C6alkyl) groups, -C(=0)-NR6R7, -NR6-C(=0)-R8, -0-C(=0)-NR6R7, -NR6-C(=0)-R8, and -NR6-C(=0)-NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)- O-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R1, R2, R3, R4, R5, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, -CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, C1-C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl).

[0366] In some embodiments, provided herein are compounds of Formula (la):pharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:R9is chosen from C3-C8 heterocyclyl groups; andR10is chosen from H and C1-C6 alkyl groups,wherein R9and R10are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, -NH2, -NH-(CI-C3 alkyl), and -N-(CI-C3alkyl)2.

[0367] In some embodiments, provided herein are compounds of Formula (lb):R11is chosen fromwherein * denotes the point of connectivity of R11to the remainder of the compound;R12and R13are each independently chosen from H and methyl.

[0368] In some embodiments, provided herein are compounds of Formula (II):(II), or a pharmaceutically acceptable salt thereof, wherein:X is hydroxyl or NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, -C(=0)-0-R8, -(Ci-C6alkyl)-0-C(=0)-R8, and -(Ci-C6alkyl)-NH-C(=0)-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, CrCe alkyl groups, -0-(Ci-Ce alkyl) groups, - C02H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, C1-C6 alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, C1-C3 haloalkyl groups, -NH-C(=0)(CI-C3alkyl), and -NH-C(=0)-0-(CI-C3alkyl).

[0369] In some embodiments, provided herein are compounds of Formula (lla):(lla), or a pharmaceutically acceptable salt thereof, wherein:Z is chosen from NR9and O;R9is chosen from hydrogen and C1-C6 alkyl groups;R10and R11are each independently chosen from hydrogen, halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-Ce alkyl) groups, -CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups;R12is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, C3-C8 heterocyclyl groups,wherein R9, R10, R11, and R12are each independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, and C1 -C3 haloalkyl groups; andt is an integer chosen from 1 , 2, 3, 4, 5, and 6.

[0370] In some embodiments, provided herein are compounds of Formula (lib):(lib), or a pharmaceutically acceptable salt thereof, wherein:, wherein * denotes the point of connectivity of R13to the remainder of the compound; andR14and R15are each independently chosen from hydrogen and methyl.

[0371] In some embodiments, provided herein are compounds of Formula (III):pharmaceutically acceptable salt thereof, wherein:R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)-O-R8;R8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups; andwherein R1, R2, R3, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl); andwherein * denotes the point of connectivity of R9to the remainder of the compound.

[0372] In some embodiments, provided herein is the compound H1 , or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H4, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H5, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H6, or a pharmaceutically acceptable salt thereof. In someembodiments, provided herein is the compound H7, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H8, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H9, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H10, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H2, or a pharmaceutically acceptable salt thereof. In someembodiments, provided herein is the compound H3, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H12, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H13, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H14, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H15, or a pharmaceutically acceptable salt thereof. In someembodiments, provided herein is the compound H16, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H17, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H18, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H19, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H20, or a pharmaceutically acceptable salt thereof. In someembodiments, provided herein is the compound H21 , or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H22, or a pharmaceuticallyacceptable salt thereof. In some embodiments, provided herein is the compound H23, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H24, or a pharmaceutically acceptable salt thereof. In some embodiments, provided herein is the compound H25, or a pharmaceutically acceptable salt thereof.

[0373] In some embodiments, provided herein is a compound chosen from:thereof,wherein L is a linker which covalently attaches to an antibody.

[0374] In some embodiments, the linker comprises at least one cleavable peptide moiety. In some embodiments, the at least one cleavable peptide moiety is cleavable by an enzyme. In some embodiments, the linker or cleavable peptide moiety comprises at least one amino acid unit. In some embodiments, the at least one amino acid unit is chosen from arginine, histidine, lysine, aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, cysteine, selenocysteine, glycine, proline, alanine, valine, isoleucine, methionine, phenylalanine, tyrosine, tryptophan, and citrulline. In some embodiments, the at least one amino acid unit is chosenfrom alanine, citrulline, and valine. In some embodiments, the linker comprises citrulline and valine. In some embodiments, the linker comprises alanine and valine.

[0375] In some embodiments, the linker comprises a moiety chosen from a sulfonamide, a b- glucuronide, a disulfide, and a carbonyl. In some embodiments, the linker comprises a sulfonamide. In some embodiments, the linker comprises a b-glucuronide. In someembodiments, the linker comprises a disulfide. In some embodiments, the linker comprises a carbonyl.

[0376] In some embodiments, the linker comprises a spacer unit. In some embodiments, the spacer unit is chosen from alkyl groups and polyethylene glycol (PEG) moieties. In some embodiments, the alkyl group is a C1-C12 alkyl group. In some embodiments, the alkyl group is a C1-C6 alkyl group. In some embodiments, the alkyl group is methylene. In someembodiments, the alkyl group is ethylene. In some embodiments, the alkyl group is n- propylene. In some embodiments, the alkyl group is n-butylene. In some embodiments, the alkyl group is n-pentylene. In some embodiments, the alkyl group is n-hexylene. In some embodiments, the PEG moiety comprises -(PEG)m-, wherein m is an integer from 1 to 10. In some embodiments, m is 1. In some embodiments, m is 2. In some embodiments, m is 3. In some embodiments, m is 4. In some embodiments, m is 5. In some embodiments, m is 6.

[0377] In some embodiments, the linker comprises a maleimide (Mai) moiety (“Mal-spacer unit”). In some embodiments, the linker comprises a self-immolative spacer unit. In some embodiments, the self-immolative spacer unit is chosen from p-aminobenzyloxycarbonyl (pABC) and p-aminobenzyl (pAB).

[0378] In some embodiments, the linker comprises a Mal-spacer unit, an alkyl group, at least one amino acid unit, and a self-immolative spacer. In some embodiments, at least one amino acid unit is chosen from alanine, citrulline, and valine. In some embodiments, the at least one amino acid unit comprises alanine and valine. In some embodiments, the at least one amino acid unit comprises citrulline and valine. In some embodiments, the self-immolative spacer is chosen from pAB and pABC. In some embodiments, the self-immolative spacer comprises pAB. In some embodiments, the self-immolative spacer comprises pABC. In someembodiments, the alkyl group comprises a C1-C6 alkyl group.

[0379] In some embodiments, the linker comprises a Mal-spacer unit, PEG moiety, at least one amino acid unit, and a self-immolative spacer. In some embodiments, at least one amino acid unit is chosen from alanine, citrulline, and valine. In some embodiments, the at least one amino acid unit comprises alanine and valine. In some embodiments, the at least one amino acid unit comprises citrulline and valine. In some embodiments, the self-immolative spacer is chosen from pAB and pABC. In some embodiments, the self-immolative spacer comprises pAB. In some embodiments, the self-immolative spacer comprises pABC. In some embodiments, the PEG moiety comprises -(PEG)m-, wherein m is an integer from 1 to 6.Drug Loading

[0380] Drug loading is represented by p, and is also referred to herein as the herboxidiene splicing modulator-to-antibody ratio (HAR). Drug loading may range from 1 to 10 drug moieties per antibody or antigen binding fragment. In some embodiments, p is an integer from 1 to 10.In some embodiments, p is an integer from 1 to 10, 1 to 9, 1 to 8, 1 to 7, 1 to 6, 1 to 5, 1 to 4, 1 to 3, or 1 to 2. In some embodiments, p is an integer from 2 to 10, 2 to 9, 2 to 8, 2 to 7, 2 to 6, 2 to 5, 2 to 4, or 2 to 3. In some embodiments, p is an integer from 1 to 8. In some embodiments, p is an integer from 2 to 5. In some embodiments, p is an integer from 2 to 4. In some embodiments, p is an integer from 3 to 4. In other embodiments, p is an integer from 4 to 8. In other embodiments, p is 1 , 2, 3, 4, 5, 6, 7, or 8, preferably 4 or 8.

[0381] Drug loading may be limited by the number of attachment sites on the antibody or antigen binding fragment. In some embodiments, the linker moiety (L) of the ADC attaches to the antibody or antigen binding fragment through a chemically active group on one or more amino acid residues on the antibody or antigen binding fragment. For example, the linker may be attached to the antibody or antigen binding fragment via a free amino, imino, hydroxyl, thiol, or carboxyl group (e.g., to the N- or C-terminus, to the epsilon amino group of one or more lysine residues, to the free carboxylic acid group of one or more glutamic acid or aspartic acid residues, or to the sulfhydryl group of one or more cysteine residues). The site to which the linker is attached can be a natural residue in the amino acid sequence of the antibody or antigen binding fragment, or it can be introduced into the antibody or antigen binding fragment, e.g., by DNA recombinant technology (e.g., by introducing a cysteine residue into the amino acid sequence) or by protein biochemistry (e.g., by reduction, pH adjustment, or hydrolysis).

[0382] In some embodiments, the number of drug moieties that can be conjugated to an antibody or antigen binding fragment is limited by the number of free cysteine residues. For example, where the attachment is a cysteine thiol group, an antibody may have only one or a few cysteine thiol groups, or may have only one or a few sufficiently reactive thiol groups through which a linker may be attached. Generally, antibodies do not contain many free and reactive cysteine thiol groups that may be linked to a drug moiety. Indeed, most cysteine thiol residues in antibodies are involved in either interchain or intrachain disulfide bonds.Conjugation to cysteines can, in some embodiments, therefore require at least partial reduction of the antibody. Over-attachment of linker-toxin to an antibody may destabilize the antibody by reducing the cysteine residues available to form disulfide bonds. Therefore, an optimal drug:antibody ratio should increase potency of the ADC (by increasing the number of attached drug moieties per antibody) without destabilizing the antibody or antigen binding fragment. In some embodiments, an optimal ratio may be 2, 4, 6, or 8.

[0383] In some embodiments, an antibody or antigen binding fragment is exposed to reducing conditions prior to conjugation in order to generate one or more free cysteine residues. An antibody, in some embodiments, may be reduced with a reducing agent such as dithiothreitol(DTT) or tris(2-carboxyethyl)phosphine (TCEP), under partial or total reducing conditions, to generate reactive cysteine thiol groups. Unpaired cysteines may be generated through partial reduction with limited molar equivalents of TCEP, which can reduce the interchain disulfide bonds which link the light chain and heavy chain (one pair per H-L pairing) and the two heavy chains in the hinge region (two pairs per H-H pairing in the case of human lgG1) while leaving the intrachain disulfide bonds intact (Stefano et al. (2013) Methods Mol Biol. 1045:145-71). In embodiments, disulfide bonds within the antibodies are reduced electrochemically, e.g., by employing a working electrode that applies an alternating reducing and oxidizing voltage. This approach can allow for on-line coupling of disulfide bond reduction to an analytical device (e.g., an electrochemical detection device, an NMR spectrometer, or a mass spectrometer) or a chemical separation device (e.g., a liquid chromatograph (e.g., an HPLC) or an electrophoresis device (see, e.g., U.S. Publ. No. 20140069822)). In certain embodiments, an antibody is subjected to denaturing conditions to reveal reactive nucleophilic groups on amino acid residues, such as cysteine.

[0384] The drug loading of an ADC may be controlled in different ways, e.g., by: (i) limiting the molar excess of drug-linker intermediate or linker reagent relative to antibody; (ii) limiting the conjugation reaction time or temperature; (iii) partial or limiting reductive conditions for cysteine thiol modification; and / or (iv) engineering by recombinant techniques the amino acid sequence of the antibody such that the number and position of cysteine residues is modified for control of the number and / or position of linker-drug attachments.

[0385] In some embodiments, free cysteine residues are introduced into the amino acid sequence of the antibody or antigen binding fragment. For example, cysteine engineered antibodies can be prepared wherein one or more amino acids of a parent antibody are replaced with a cysteine amino acid. Any form of antibody may be so engineered, i.e. mutated. For example, a parent Fab antibody fragment may be engineered to form a cysteine engineered Fab referred to as a "ThioFab." Similarly, a parent monoclonal antibody may be engineered to form a "ThioMab." A single site mutation yields a single engineered cysteine residue in a ThioFab, whereas a single site mutation yields two engineered cysteine residues in a ThioMab, due to the dimeric nature of the IgG antibody. DNA encoding an amino acid sequence variant of the parent polypeptide can be prepared by a variety of methods known in the art (see, e.g., the methods described in Inti. Pub. No. WO 2006 / 034488). These methods include, but are not limited to, preparation by site-directed (or oligonucleotide-mediated) mutagenesis, PCR mutagenesis, and cassette mutagenesis of an earlier prepared DNA encoding the polypeptide. Variants of recombinant antibodies may also be constructed by restriction fragmentmanipulation or by overlap extension PCR with synthetic oligonucleotides. ADCs of Formula (I) include, but are not limited to, antibodies that have 1 , 2, 3, or 4 engineered cysteine amino acids (Lyon et al. (2012) Methods Enzymol. 502:123-38). In some embodiments, one or more free cysteine residues are already present in an antibody or antigen binding fragment, without theuse of engineering, in which case the existing free cysteine residues may be used to conjugate the antibody or antigen binding fragment to a drug moiety.

[0386] Where more than one nucleophilic group reacts with a drug-linker intermediate or a linker moiety reagent followed by drug moiety reagent, in a reaction mixture comprising multiple copies of the antibody or antigen binding fragment and linker moiety, then the resulting product can be a mixture of ADC compounds with a distribution of one or more drug moieties attached to each copy of the antibody or antigen binding fragment in the mixture. In some embodiments, the drug loading in a mixture of ADCs resulting from a conjugation reaction ranges from 1 to 10 drug moieties attached per antibody or antigen binding fragment. The average number of drug moieties per antibody or antigen binding fragment (i.e. , the average drug loading, or average p) may be calculated by any conventional method known in the art, e.g., by mass spectrometry (e.g., reverse-phase LC-MS), and / or high-performance liquid chromatography (e.g., HIC-HPLC). In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is determined by hydrophobic interaction chromatography-high performance liquid chromatography (HIC-HPLC). In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is determined by reverse-phase liquid chromatography- mass spectrometry (LC-MS). In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is from about 1.5 to about 3.5, about 2.5 to about 4.5, about 3.5 to about 5.5, about 4.5 to about 6.5, about 5.5 to about 7.5, about 6.5 to about 8.5, or about 7.5 to about 9.5. In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is from about 2 to about 4, about 3 to about 5, about 4 to about 6, about 5 to about 7, about 6 to about 8, about 7 to about 9, about 2 to about 8, or about 4 to about 8.

[0387] In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is about 2. In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2, about 2.1 , about 2.2, about 2.3, about 2.4, or about 2.5. In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is 2.

[0388] In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is about 4. In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is about 3.5, about 3.6, about 3.7, about 3.8, about 3.9, about 4, about 4.1 , about 4.2, about 4.3, about 4.4, or about 4.5. In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is 4.

[0389] In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is about 8. In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is about 7.5, about 7.6, about 7.7, about 7.8, about 7.9, about 8, about 8.1 , about 8.2, about 8.3, about 8.4, or about 8.5. In some embodiments, the average number of drug moieties per antibody or antigen binding fragment is 8.

[0390] In various embodiments, the term“about,” as used with respect to the average number of drug moieties per antibody or antigen binding fragment, means plus or minus 10%.

[0391] Individual ADC compounds, or“species,” may be identified in the mixture by mass spectroscopy and separated by UPLC or HPLC, e.g. hydrophobic interaction chromatography (HIC-HPLC). In certain embodiments, a homogeneous or nearly homogenous ADC product with a single loading value may be isolated from the conjugation mixture, e.g., byelectrophoresis or chromatography.

[0392] In some embodiments, higher drug loading (e.g., p > 8) may cause aggregation, insolubility, toxicity, or loss of cellular permeability of certain antibody-drug conjugates. Higher drug loading may also negatively affect the pharmacokinetics (e.g., clearance) of certain ADCs. In some embodiments, lower drug loading (e.g., p < 2) may reduce the potency of certain ADCs against target-expressing cells and / or bystander cells. In some embodiments, the drug loading for an ADC of the present disclosure ranges from about 2 to about 8; from about 2 to about 6; from about 2 to about 5; from about 3 to about 5; from about 2 to about 4; or from about 4 to about 8.

[0393] In some embodiments, a drug loading and / or an average drug loading of about 2 is achieved, e.g., using partial reduction of intrachain disulfides on the antibody or antigen binding fragment, and provides beneficial properties. In some embodiments, a drug loading and / or an average drug loading of about 4 is achieved, e.g., using partial reduction of intrachain disulfides on the antibody or antigen binding fragment, and provides beneficial properties. In some embodiments, a drug loading and / or an average drug loading of about 8 is achieved, e.g., using partial reduction of intrachain disulfides on the antibody or antigen binding fragment, and provides beneficial properties. In some embodiments, a drug loading and / or an average drug loading of less than about 2 may result in an unacceptably high level of unconjugated antibody species, which can compete with the ADC for binding to a target antigen and / or provide for reduced treatment efficacy. In some embodiments, a drug loading and / or average drug loading of more than about 8 may result in an unacceptably high level of product heterogeneity and / or ADC aggregation. A drug loading and / or an average drug loading of more than about 8 may also affect stability of the ADC, due to loss of one or more chemical bonds required to stabilize the antibody or antigen binding fragment.

[0394] The present disclosure includes methods of producing the described ADCs. Briefly, the ADCs comprise an antibody or antigen binding fragment as the antibody or antigen binding fragment, a drug moiety (e.g., a herboxidiene splicing modulator), and a linker that joins the drug moiety and the antibody or antigen binding fragment. In some embodiments, the ADCs can be prepared using a linker having reactive functionalities for covalently attaching to the drug moiety and to the antibody or antigen binding fragment. For example, in some embodiments, a cysteine thiol of an antibody or antigen binding fragment can form a bond with a reactive functional group of a linker or a drug-linker intermediate (e.g., a maleimide moiety) to make anADC. The generation of the ADCs can be accomplished by any technique known to the skilled artisan.

[0395] In some embodiments, an ADC is produced by contacting an antibody or antigen binding fragment with a linker and a drug moiety (e.g., a herboxidiene splicing modulator) in a sequential manner, such that the antibody or antigen binding fragment is covalently linked to the linker first, and then the pre-formed antibody-linker intermediate reacts with the drug moiety.The antibody-linker intermediate may or may not be subjected to a purification step prior to contacting the drug moiety. In other embodiments, an ADC is produced by contacting an antibody or antigen binding fragment with a linker-drug compound pre-formed by reacting a linker with a drug moiety. The pre-formed linker-drug compound may or may not be subjected to a purification step prior to contacting the antibody or antigen binding fragment. In other embodiments, the antibody or antigen binding fragment contacts the linker and the drug moiety in one reaction mixture, allowing simultaneous formation of the covalent bonds between the antibody or antigen binding fragment and the linker, and between the linker and the drug moiety. This method of producing ADCs may include a reaction, wherein the antibody or antigen binding fragment contacts the antibody or antigen binding fragment prior to the addition of the linker to the reaction mixture, and vice versa. In certain embodiments, an ADC is produced by reacting an antibody or antigen binding fragment with a linker joined to a drug moiety, such as ADL1 -herboxidiene splicing modulator (e.g., ADL1-79392) or ADL5- herboxidiene splicing modulator (e.g., ADL5-0349), under conditions that allow conjugation.

[0396] The ADCs prepared according to the methods described above may be subjected to a purification step. The purification step may involve any biochemical methods known in the art for purifying proteins, or any combination of methods thereof. These include, but are not limited to, tangential flow filtration (TFF), affinity chromatography, ion exchange chromatography, any charge or isoelectric point-based chromatography, mixed mode chromatography, e.g., CHT (ceramic hydroxyapatite), hydrophobic interaction chromatography, size exclusionchromatography, dialysis, filtration, selective precipitation, or any combination thereof.Therapeutic Uses and Compositions

[0397] Disclosed herein are methods of using the disclosed ADCs and compositions in treating a subject for a disorder, e.g., a neoplastic disorder. ADCs may be administered alone or in combination with a second therapeutic agent, and may be administered in any pharmaceutically acceptable formulation, dosage, and dosing regimen. ADC treatment efficacy may be evaluated for toxicity as well as indicators of efficacy and adjusted accordingly. Efficacy measures include, but are not limited to, a cytostatic and / or cytotoxic effect observed in vitro or in vivo, reduced tumor volume, tumor growth inhibition, and / or prolonged survival.

[0398] Methods of determining whether an ADC exerts a cytostatic and / or cytotoxic effect on a cell are known. For example, the cytotoxic or cytostatic activity of an ADC can be measured by: exposing mammalian cells expressing a target protein of the ADC in a cell culture medium;culturing the cells for a period from about 6 hours to about 6 days; and measuring cell viability. Cell-based in vitro assays may also be used to measure viability (proliferation), cytotoxicity, and induction of apoptosis (caspase activation) of the ADC.

[0399] For determining whether an ADC exerts a cytostatic effect, a thymidine incorporation assay may be used. For example, cancer cells expressing a target antigen at a density of 5,000 cells / well of a 96-well plated can be cultured for a 72-hour period and exposed to 0.5 pCi of3H- thymidine during the final 8 hours of the 72-hour period. The incorporation of3H-thymidine into cells of the culture is measured in the presence and absence of the ADC.

[0400] For determining cytotoxicity, necrosis or apoptosis (programmed cell death) may be measured. Necrosis is typically accompanied by increased permeability of the plasma membrane; swelling of the cell, and rupture of the plasma membrane. Apoptosis can be quantitated, for example, by measuring DNA fragmentation. Commercial photometric methods for the quantitative in vitro determination of DNA fragmentation are available. Examples of such assays, including TUN EL (which detects incorporation of labeled nucleotides in fragmented DNA) and ELISA-based assays, are described in Biochemica (1999) No. 2, pp. 34-37 (Roche Molecular Biochemicals).

[0401] Apoptosis may also be determined by measuring morphological changes in a cell. For example, as with necrosis, loss of plasma membrane integrity can be determined by measuring uptake of certain dyes (e.g., a fluorescent dye such as, for example, acridine orange or ethidium bromide). A method for measuring apoptotic cell number has been described by Duke and Cohen, Current Protocols in Immunology (Coligan et al., eds. (1992) pp. 3.17.1-3.17.16). Cells also can be labeled with a DNA dye (e.g., acridine orange, ethidium bromide, or propidium iodide) and the cells observed for chromatin condensation and margination along the inner nuclear membrane. Apoptosis may also be determined, in some embodiments, by screening for caspase activity. In some embodiments, a Caspase-Glo® Assay can be used to measure activity of caspase-3 and caspase-7. In some embodiments, the assay provides a luminogenic caspase-3 / 7 substrate in a reagent optimized for caspase activity, luciferase activity, and cell lysis. In some embodiments, adding Caspase-Glo® 3 / 7 Reagent in an“add-mix-measure” format may result in cell lysis, followed by caspase cleavage of the substrate and generation of a“glow-type” luminescent signal, produced by luciferase. In some embodiments, luminescence may be proportional to the amount of caspase activity present, and can serve as an indicator of apoptosis. Other morphological changes that can be measured to determine apoptosis include, e.g., cytoplasmic condensation, increased membrane blebbing, and cellular shrinkage.Determination of any of these effects on cancer cells indicates that an ADC is useful in the treatment of cancers.

[0402] Cell viability may be measured, e.g., by determining in a cell the uptake of a dye such as neutral red, trypan blue, Crystal Violet, or ALAMAR™ blue (see, e.g., Page et al. (1993) Inti JOncology 3:473-6). In such an assay, the cells are incubated in media containing the dye, thecells are washed, and the remaining dye, reflecting cellular uptake of the dye, is measured spectrophotometrically. Cell viability may also be measured, e.g., by quantifying ATP, an indicator of metabolically active cells. In certain embodiments, in vitro potency and / or cell viability of prepared ADCs or herboxidiene splicing modulator compounds may be assessed using a CellTiter-Glo® Luminescent Cell Viability Assay, as described in the examples provided herein. In this assay, in certain embodiments, the single reagent (CellTiter-Glo® Reagent) is added directly to cells cultured in serum-supplemented medium. The addition of reagent results in cell lysis and generation of a luminescent signal proportional to the amount of ATP present. The amount of ATP is directly proportional to the number of cells present in culture. The protein-binding dye sulforhodamine B (SRB) can also be used to measure cytotoxicity (Skehan et al. (1990) J Natl Cancer Inst. 82:1107-12).

[0403] The disclosed ADCs may also be evaluated for bystander killing activity. Bystander killing activity may be determined, e.g., by an assay employing two cell lines, one positive for a target antigen and one negative for a target antigen. In certain embodiments, the design of the assay allows tracking of only target negative cells. In certain embodiments, cells are plated under three conditions: (i) target negative cells alone (tagged or labeled); (ii) target positive cells alone; and (iii) co-culture of target negative cells and target positive cells. Cells are then treated with an ADC followed by monitoring of cytotoxicity. When plates are read with CellTiter-Glo® Reagent, viability of all cell populations can be monitored. When plates are read with OneGlo® Reagent, only the tagged or labeled target negative cells produce a signal. Killing of the target negative cells when mixed with target-positive cells is indicative of bystander killing, whereas killing of the target-negative cells in the absence of the target-positive cells is indicative of off- target killing.

[0404] In certain aspects, the present disclosure features a method of killing, inhibiting or modulating the growth of, or interfering with the metabolism of, a cancer cell or tissue by disrupting RNA splicing. The method may be used with any subject where disruption of RNA splicing provides a therapeutic benefit. Subjects that may benefit from disrupting RNA splicing include, but are not limited to, those having or at risk of having a neoplastic disorder such as a hematological malignancy or a solid tumor. In certain embodiments, the hematological malignancy is a B-cell malignancy, a cancer of the blood (leukemia), a cancer of plasma cells (myeloma, e.g., multiple myeloma), or a cancer of the lymph nodes (lymphoma). In certain embodiments, the hematological malignancy is acute myelogenous leukemia or multiple myeloma. In certain embodiments, the leukemia is acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), chronic lymphocytic leukemia (CLL), chronic myelogenous leukemia (CML), chronic myelomonocytic leukemia (CMML), or acute monocytic leukemia (AMoL). In certain embodiments, the lymphoma is Hodgkin's lymphoma or non-Hodgkin's lymphoma. In certain embodiments, the hematological malignancy is myelodysplasia syndrome(MDS). In certain embodiments, the solid tumor is a carcinoma such as breast cancer,pancreatic cancer, prostate cancer, colon or colorectal cancer, lung cancer, gastric cancer, cervical cancer, endometrial cancer, ovarian cancer, cholangiocarcinoma, glioma, or melanoma. In certain embodiments, the solid tumor is breast cancer, gastric cancer, prostate cancer, ovarian cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, or esophageal cancer. In certain embodiments, the lung cancer is lung adenocarcinoma. In certain embodiments, the uterine cancer is uterine serous endometrial carcinoma.

[0405] In various embodiments, the disclosed ADCs may be administered in any cell or tissue that expresses HER2, such as a HER2-expressing neoplastic cell or tissue. An exemplary embodiment includes a method of inhibiting HER2-mediated cell signaling or a method of killing a cell. The method may be used with any cell or tissue that expresses HER2, such as a cancerous cell or a metastatic lesion. Non-limiting examples of HER2-expressing cancers include breast cancer, gastric cancer, bladder cancer, urothelial cell carcinoma, esophageal cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), salivary duct carcinoma, cervical cancer, endometrial cancer, and ovarian cancer (English et al. (2013) Mol Diagn Ther. 17:85-99). Non-limiting examples of HER2-expressing cells include HCC1954 and SKBR3 human breast ductal carcinoma cells,N87 human gastric carcinoma cells, and cells comprising a recombinant nucleic acid encoding HER2 or a portion thereof.

[0406] In various embodiments, the disclosed ADCs may be administered in any cell or tissue that expresses CD138, such as a CD138-expressing neoplastic cell or tissue. An exemplary embodiment includes a method of inhibiting CD138-mediated cell signaling or a method of killing a cell. The method may be used with any cell or tissue that expresses CD138, such as a cancerous cell or a metastatic lesion. Non-limiting examples of CD138-expressing cancers include intrathoracic cancer (e.g., lung cancer, mesothelioma), skin cancer (e.g., basal cell carcinoma, squamous cell carcinoma), head and neck cancer (e.g., laryngeal, hypopharynx, nasopharyngeal), breast cancer, urogenital cancer (e.g., cervical cancer, ovarian cancer, endometrial cancer, prostate cancer, bladder cancer, urothelial cancer), hematological malignancies (e.g., myeloma such as multiple myeloma, Hodgkin’s lymphoma), and thyroid cancer (Szatmari et al. (2015) Dis Markers 2015:796052). Non-limiting examples of CD138- expressing cells include MOLP8 human multiple myeloma cells, and cells comprising a recombinant nucleic acid encoding CD138 or a portion thereof.

[0407] In various embodiments, the disclosed ADCs may be administered in any cell or tissue that expresses EPHA2, such as an EPHA2-expressing neoplastic cell or tissue. An exemplary embodiment includes a method of inhibiting EPHA2-mediated cell signaling or a method of killing a cell. The method may be used with any cell or tissue that expresses EPHA2, such as a cancerous cell or a metastatic lesion. Non-limiting examples of EPHA2-expressing cancersinclude breast cancer, brain cancer, ovarian cancer, bladder cancer, pancreatic cancer, esophageal cancer, lung cancer, prostate cancer, melanoma, esophageal cancer, and gastric cancer (Tandon et al. (2011) Expert Opin Ther Targets 15(1):31-51. Non-limiting examples of EPHA2-expressing cells include PC3 human prostate cancer cells, and cells comprising a recombinant nucleic acid encoding EPHA2 or a portion thereof.

[0408] Exemplary methods include the steps of contacting a cell with an ADC, as described herein, in an effective amount, i.e., amount sufficient to kill the cell. The method can be used on cells in culture, e.g. in vitro, in vivo, ex vivo, or in situ. For example, cells that express HER2 (e.g., cells collected by biopsy of a tumor or metastatic lesion; cells from an established cancer cell line; or recombinant cells), can be cultured in vitro in culture medium and the contacting step can be affected by adding the ADC to the culture medium. The method will result in killing of cells expressing HER2, including in particular tumor cells expressing HER2. Alternatively, the ADC can be administered to a subject by any suitable administration route (e.g., intravenous, subcutaneous, or direct contact with a tumor tissue) to have an effect in vivo. This approach can be used for antibodies targeting other cell surface antigens (e.g., CD138, EPHA2).

[0409] The in vivo effect of a disclosed ADC therapeutic composition can be evaluated in a suitable animal model. For example, xenogeneic cancer models can be used, wherein cancer explants or passaged xenograft tissues are introduced into immune compromised animals, such as nude or SCID mice (Klein et al. (1997) Nature Med. 3:402-8). Efficacy may be predicted using assays that measure inhibition of tumor formation, tumor regression or metastasis, and the like.

[0410] In vivo assays that evaluate the promotion of tumor death by mechanisms such as apoptosis may also be used. In one embodiment, xenografts from tumor bearing mice treated with the therapeutic composition can be examined for the presence of apoptotic foci and compared to untreated control xenograft-bearing mice. The extent to which apoptotic foci are found in the tumors of the treated mice provides an indication of the therapeutic efficacy of the composition.

[0411] Further provided herein are methods of treating a neoplastic disorder, e.g., a cancer.The ADCs disclosed herein can be administered to a non-human mammal or human subject for therapeutic purposes. The therapeutic methods entail administering to a subject having or suspected of having a neoplastic disorder a therapeutically effective amount of an ADC or composition comprising a herboxidiene splicing modulator linked to a targeting antibody that binds to an antigen expressed, is accessible to binding, or is localized on a cancer cell surface. In some embodiments, treatment with the antibody-drug conjugate or composition induces bystander killing of neoplastic cells which do not express a target antigen but are adjacent to neoplastic cells which express a target antigen.

[0412] An exemplary embodiment is a method of delivering a herboxidiene splicing modulator to a cell expressing HER2, comprising conjugating the herboxidiene splicing modulator to anantibody that immunospecifically binds to a HER2 epitope and exposing the cell to the ADC. Exemplary tumor cells that express HER2 for which the ADCs of the present disclosure are indicated include gastric carcinoma cells and breast ductal carcinoma cells.

[0413] Another exemplary embodiment is a method of delivering a herboxidiene splicing modulator to a cell expressing CD138, comprising conjugating the herboxidiene splicing modulator to an antibody that immunospecifically binds to a CD138 epitope and exposing the cell to the ADC. Exemplary tumor cells that express CD138 for which the ADCs of the present disclosure are indicated include multiple myeloma cells.

[0414] Another exemplary embodiment is a method of delivering a herboxidiene splicing modulator to a cell expressing EPHA2, comprising conjugating the herboxidiene splicing modulator to an antibody that immunospecifically binds to an EPHA2 epitope and exposing the cell to the ADC. Exemplary tumor cells that express EPHA2 for which the ADCs of the present disclosure are indicated include prostate cancer cells.

[0415] Another exemplary embodiment is a method of reducing or inhibiting growth of a tumor (e.g., a HER2-expressing tumor, a CD138-expressing tumor, an EPHA2-expressing tumor), comprising administering a therapeutically effective amount of an ADC or composition comprising an ADC. In some embodiments, the treatment is sufficient to reduce or inhibit the growth of the patient's tumor, reduce the number or size of metastatic lesions, reduce tumor load, reduce primary tumor load, reduce invasiveness, prolong survival time, and / or maintain or improve the quality of life. In some embodiments, the tumor is resistant or refractory to treatment with the antibody or antigen binding fragment of the ADC (e.g., an anti-HER2 antibody, an anti-CD138 antibody, an anti-EPHA2 antibody) when administered alone, and / or the tumor is resistant or refractory to treatment with the herboxidiene splicing modulator drug moiety when administered alone

[0416] In certain aspects, the present disclosure provides a method of reducing or inhibiting growth of a HER2-expressing tumor. In certain embodiments, treatment with the antibody-drug conjugate or composition induces bystander killing of tumor cells which do not express HER2 but that are adjacent to neoplastic tumor cells which do express HER2. Exemplary HER2- expressing tumor types include but are not limited to tumors derived from a HER2-expressing breast cancer, gastric cancer, bladder cancer, urothelial cell carcinoma, esophageal cancer, lung cancer (e.g., lung adenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), salivary duct carcinoma, cervical cancer, endometrial cancer, and ovarian cancer. In certain embodiments, the HER2-expressing tumor is a tumor derived from a HER2- expressing breast cancer, ovarian cancer, gastric cancer, lung cancer (e.g., lungadenocarcinoma), uterine cancer (e.g., uterine serous endometrial carcinoma), osteosarcoma, or salivary duct carcinoma. In certain embodiments, the HER2-expressing tumor is a lung adenocarcinoma or uterine serous endometrial carcinoma.

[0417] In certain aspects, the present disclosure provides a method of reducing or inhibiting growth of a CD138-expressing tumor. In certain embodiments, treatment with the antibody-drug conjugate or composition induces bystander killing of tumor cells which do not express CD138 but that are adjacent to neoplastic tumor cells which do express CD138. Exemplary CD138- expressing tumor types include but are not limited to tumors derived from a CD138-expressing intrathoracic cancer (e.g...

Claims

CLAIMS1. An antibody-drug conjugate of Formula (I):Ab-(L-H)p(I)wherein:Ab is an antibody or antigen binding fragment which targets a neoplastic cell;H is a herboxidiene splicing modulator;L is a linker which covalently attaches Ab to H; andp is an integer from 1 to 15.

2. The antibody-drug conjugate of claim 1 , wherein the herboxidiene splicing modulator comprises a compound of Formula (I):pharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:Y is chosen from O, S, NR6, and CR6R7;R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R4is chosen from hydrogen, C1-C6 alkyl groups, -C(=0)-(Ci-C6alkyl) groups, -C(=0)- (C3-C8 carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, and -C(=0)-NR6R7;R5is chosen from hydrogen, hydroxyl, -CH2-OH, -CO2H, -C(=0)-0-(Ci-C6alkyl) groups, -C(=0)-NR6R7, -NR6-C(=0)-R8, -0-C(=0)-NR6R7, -NR6-C(=0)-R8, and -NR6-C(=0)-NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)- O-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R1, R2, R3, R4, R5, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, -CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, C1-C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl), andwherein the valency of the atom that is covalently attached to L is not exceeded.

3. The antibody-drug conjugate of claim 1 or claim 2, wherein the herboxidiene splicing modulator comprises a compound of Formula (la):pharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:R9is chosen from C3-C8 heterocyclyl groups;R10is chosen from H and CrCe alkyl groups,wherein R9and R10are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, -IMH2, -NH-(CI-C3 alkyl), and -N-(CI-C3 alkyl)2, andwherein the valency of the atom that is covalently attached to L is not exceeded.

4. The antibody-drug conjugate of any one of claims 1 to 3, wherein the herboxidiene splicing modulator comprises a compound of Formula (lb):OO L Ri ipharmaceutically acceptable salt thereof, which covalently attaches to L through any atom, wherein:R11is chosen fromwherein * denotes the point of connectivity of R11to the remainder of the compound;R12and R13are each independently chosen from H and methyl; andwherein the valency of the atom that is covalently attached to L is not exceeded.

5. The antibody-drug conjugate of any one of claims 1 to 4,wherein the herboxidiene splicing modulator covalently attaches through any atom to L wherein the herboxidiene splicing modulator is chosen from H1 , H2, H3, and H12; and wherein the valency of the atom that is covalently attached to L is not exceeded.

6. The antibody-drug conjugate of claim 1 or claim 2, wherein L covalently attaches to the herboxidiene splicing modulator (“L-H”), and L-H has a structure chosen from the following structures:and a pharmaceutically acceptable salt thereof.

7. The antibody-drug conjugate of claim 1 , wherein the herboxidiene splicing modulator is a splicing modulator of Formula (II):(II), or a pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:X is hydroxyl or NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, -C(=0)-0-R8, -(Ci-C6alkyl)-0-C(=0)-R8, and -(Ci-C6alkyi)-NH-C(=0)-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, C1-C6 alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3alkyl), and -NH-C(=0)-0-(Ci-C3alkyl), andwherein the valency of the atom that is covalently attached to L is not exceeded.

8. The antibody-drug conjugate of claim 1 or claim 7, wherein the herboxidiene splicing modulator is a splicing modulator of Formula (I la):I la), or a pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:Z is chosen from NR9and O;R9is chosen from hydrogen and C1-C6 alkyl groups;R10and R11are each independently chosen from hydrogen, halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-Ce alkyl) groups, -CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups;R12is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, C3-C8 heterocyclyl groups,wherein R9, R10, R11, and R12are each independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, and C1 -C3 haloalkyl groups;t is an integer chosen from 1 , 2, 3, 4, 5, and 6; andwherein the valency of the atom that is covalently attached to L is not exceeded.

9. The antibody-drug conjugate of claim 1 , 7, or 8, wherein the herboxidiene splicingmodulator is a splicing modulator of Formula (lib):(lib), or a pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:wherein * denotes the point of connectivity of R13to the remainder of the compound;R14and R15are each independently chosen from hydrogen and methyl; andwherein the valency of the atom that is covalently attached to L is not exceeded.

10. The antibody-drug conjugate of claim 1 , 7, 8, or 9,wherein the herboxidiene splicing modulator covalently attaches through any atom to L;wherein the herboxidiene splicing modulator is chosen from H4, H13, H14, H15, H16, H17, H18, H19, H20, H21 , H23, and H24; andwherein the valency of the atom that is covalently attached to L is not exceeded.

11. The antibody-drug conjugate of claim 1 or claim 7, wherein L covalently attaches to the herboxidiene splicing modulator (“L-H”), and L-H has a structure chosen from the following structure:and a pharmaceutically acceptable salt thereof.

12. The antibody-drug conjugate of claim 1 , wherein the herboxidiene splicing modulator is a splicing modulator of Formula (III):pharmaceutically acceptable salt thereof, which covalently attaches through any atom to L, wherein:R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)-O-R8;R8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups; andwherein R1, R2, R3, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl),wherein the valency of the atom that is covalently attached to L is not exceeded; and wherein * denotes the point of connectivity of R9to the remainder of the compound.

13. The antibody-drug conjugate of claim 1 or claim 12,wherein the herboxidiene splicing modulator covalently attaches through any atom to L; wherein the herboxidiene splicing modulator is chosen from H5, H6, H7, H8, H9, H10,H 11 , H22, and H25; andwherein the valency of the atom that is covalently attached to L is not exceeded.

14. The antibody-drug conjugate of claim 1 or claim 12, wherein the linker covalently attaches to the herboxidiene splicing modulator (“L-H”), and L-H has a structure chosen from the following structures:

15. The antibody-drug conjugate of claim 1 ,wherein the herboxidiene splicing modulator covalently attaches through any atom to L; wherein the herboxidiene splicing modulator is chosen from H1 , H2, H3, H4, H5, H6, H7,H8, H9, H10, H 11 , H12, H13, H14, H15, H16, H17, H18, H19, H20, H21 , H22, H23, H24, andH25; andwherein the valency of the atom that is covalently attached to L is not exceeded.

16. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H1.

17. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H2.

18. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H3.

19. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H4.

20. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H5.

21. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H6.

22. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H7.

23. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H8.

24. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H9.

25. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H10.

26. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H11.

27. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H12.

28. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H13.

29. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H14.

30. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H15.

31. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H16.

32. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H17.

33. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H18.

34. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H19.

35. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H20.

36. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H21.

37. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H22.

38. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H23.

39. The antibody-drug conjugate of claim 15, wherein the herboxidiene splicing modulator is H24.

40. The antibody-drug conjugate of any one of claims 1 to 39, wherein the linker is a cleavable linker.

41. The antibody-drug conjugate of claim 40, wherein the linker comprises a cleavable peptide moiety.

42. The antibody-drug conjugate of claim 41 , wherein the cleavable peptide moiety is cleavable by an enzyme.

43. The antibody-drug conjugate of any one of claims 40 to 42, wherein the cleavable peptide moiety or linker comprises an amino acid unit.

44. The antibody-drug conjugate of claim 43, wherein the amino acid unit comprises valine- citrulline (Val-Cit).

45. The antibody-drug conjugate of claim 43, wherein the amino acid unit comprises valine- alanine (Val-Ala).

46. The antibody-drug conjugate of claim 43, wherein the amino acid unit comprises glutamine-valine-citrulline (Glu-Val-Cit).

47. The antibody-drug conjugate of claim 43, wherein the amino acid unit comprises alanine- alanine-asparagine (Ala-Ala-Asn).

48. The antibody-drug conjugate of claim 40, wherein the linker comprises a cleavable glucuronide moiety.

49. The antibody-drug conjugate of claim 48, wherein the cleavable glucuronide moiety is cleavable by an enzyme.

50. The antibody-drug conjugate of claim 48 or claim 49, wherein the cleavable glucuronide moiety is cleavable by a glucuronidase.

51. The antibody-drug conjugate of any one of claims 48 to 50, wherein the cleavable glucuronide moiety is cleavable by b-glucuronidase.

52. The antibody-drug conjugate of any one of claims 1 to 51 , wherein the linker comprises at least one spacer unit.

53. The antibody-drug conjugate of claim 52, wherein the spacer unit or linker comprises a polyethylene glycol (PEG) moiety.

54. The antibody-drug conjugate of claim 53, wherein the PEG moiety comprises -(PEG)m- and m is an integer from 1 to 10.

55. The antibody-drug conjugate of claim 54, wherein m is 2.

56. The antibody-drug conjugate of claim 52, wherein the spacer unit or linker comprises an alkyl moiety.

57. The antibody-drug conjugate of claim 56, wherein the alkyl moiety comprises-(CHz and n is an integer from 1 to 10.

58. The antibody-drug conjugate of claim 57, wherein n is 2.

59. The antibody-drug conjugate of claim 57, wherein n is 5.

60. The antibody-drug conjugate of claim 57, wherein n is 6.

61. The antibody-drug conjugate of any one of claims 52 to 60, wherein the spacer unit attaches to the antibody or antigen binding fragment via a maleimide (Mai) moiety (“Mal-spacer unit”).

62. The antibody-drug conjugate of claim 61 , wherein the Mal-spacer unit is reactive with a cysteine residue on the antibody or antigen binding fragment.

63. The antibody-drug conjugate of claim 61 or claim 62, wherein the Mal-spacer unit is joined to the antibody or antigen binding fragment via a cysteine residue on the antibody or antigen binding fragment.

64. The antibody-drug conjugate of any one of claims 61 to 63, wherein the linker comprises the Mal-spacer unit and a cleavable peptide moiety.

65. The antibody-drug conjugate of claim 64, wherein the cleavable peptide moiety comprises an amino acid unit.

66. The antibody-drug conjugate of claim 64 or claim 65, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit.

67. The antibody-drug conjugate of claim 64 or claim 65, wherein the cleavable peptide moiety or amino acid unit comprises Val-Ala.

68. The antibody-drug conjugate of claim 64 or claim 65, wherein the cleavable peptide moiety or amino acid unit comprises Glu-Val-Cit.

69. The antibody-drug conjugate of claim 64 or claim 65, wherein the cleavable peptide moiety or amino acid unit comprises Ala-Ala-Asn.

70. The antibody-drug conjugate of any one of claims 61 to 69, wherein the Mal-spacer unit comprises an alkyl moiety.

71. The antibody-drug conjugate of any one of claims 61 to 69, wherein the Mal-spacer unit comprises a PEG moiety.

72. The antibody-drug conjugate of any one of claims 61 to 71 , wherein the Mal-spacer unit comprises a maleimidocaproyl (MC).

73. The antibody-drug conjugate of any one of claims 61 to 72, wherein the Mal-spacer unit attaches the antibody or antigen binding fragment to the cleavable moiety in the linker.

74. The antibody-drug conjugate of claim 73, wherein the cleavable moiety in the linker comprises a cleavable peptide moiety.

75. The antibody-drug conjugate of claim 74, wherein the cleavable peptide moiety comprises an amino acid unit.

76. The antibody-drug conjugate of claim 74 or claim 75, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn.

77. The antibody-drug conjugate of any one of claims 73 to 76, wherein the linker comprises MC-Val-Cit.

78. The antibody-drug conjugate of any one of claims 73 to 76, wherein the linker comprises MC-Val-Ala.

79. The antibody-drug conjugate of any one of claims 73 to 76, wherein the linker comprises MC-Glu-Val-Cit.

80. The antibody-drug conjugate of any one of claims 73 to 76, wherein the linker comprises MC-Ala-Ala-Asn.

81. The antibody-drug conjugate of any one of claims 73 to 80, wherein the Mal-spacer unit comprises an alkyl moiety.

82. The antibody-drug conjugate of any one of claims 73 to 80, wherein the Mal-spacer unit comprises a PEG moiety.

83. The antibody-drug conjugate of any one of claims 73 to 82, wherein the Mal-spacer unit comprises a maleimidocaproyl (MC).

84. The antibody-drug conjugate of any one of claims 52 to 83, wherein the cleavable moiety in the linker is directly joined to the splicing modulator, or wherein a spacer unit attaches the cleavable moiety in the linker to the splicing modulator.

85. The antibody-drug conjugate of claim 84, wherein cleavage of the conjugate releases the splicing modulator from the antibody or antigen binding fragment and linker.

86. The antibody-drug conjugate of claim 84 or claim 85, wherein the spacer unit attaching the cleavable moiety in the linker to the splicing modulator is self-immolative.

87. The antibody-drug conjugate of any one of claims 84 to 86, wherein the spacer unit attaching the cleavable moiety in the linker to the splicing modulator comprises a p- aminobenzyloxycarbonyl (pABC).

88. The antibody-drug conjugate of claim 87, wherein the pABC attaches the cleavable moiety in the linker to the splicing modulator.

89. The antibody-drug conjugate of claim 87 or claim 88, wherein the cleavable moiety in the linker comprises a cleavable peptide moiety.

90. The antibody-drug conjugate of claim 89, wherein the cleavable peptide moiety comprises an amino acid unit.

91. The antibody-drug conjugate of claim 89 or claim 90, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn.

92. The antibody-drug conjugate of any one of claims 87 to 91 , wherein the linker comprises Val-Cit-pABC.

93. The antibody-drug conjugate of any one of claims 87 to 91 , wherein the linker comprises Val-Ala-pABC.

94. The antibody-drug conjugate of any one of claims 87 to 91 , wherein the linker comprises Glu-Val-Cit-pABC.

95. The antibody-drug conjugate of any one of claims 87 to 91 , wherein the linker comprises Ala-Ala-Asn-pABC.

96. The antibody-drug conjugate of any one of claims 84 to 86, wherein the spacer unit attaching the cleavable moiety in the linker to the splicing modulator comprises a p-aminobenzyl (PAB).

97. The antibody-drug conjugate of claim 96, wherein the pAB attaches the cleavable moiety in the linker to the splicing modulator.

98. The antibody-drug conjugate of claim 96 or claim 97, wherein the cleavable moiety in the linker comprises a cleavable peptide moiety.

99. The antibody-drug conjugate of claim 98, wherein the cleavable peptide moiety comprises an amino acid unit.

100. The antibody-drug conjugate of claim 98 or claim 99, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn.

101. The antibody-drug conjugate of any one of claims 96 to 100, wherein the linker comprises Val-Cit-pAB.

102. The antibody-drug conjugate of any one of claims 96 to 100, wherein the linker comprises Val-Ala-pAB.

103. The antibody-drug conjugate of any one of claims 96 to 100, wherein the linker comprises Glu-Val-Cit-pAB.

104. The antibody-drug conjugate of any one of claims 96 to 100, wherein the linker comprises Ala-Ala-Asn-pAB.

105. The antibody-drug conjugate of any one of claims 1 to 39, wherein the linker is a non- cleavable linker.

106. The antibody-drug conjugate of claim 105, wherein the linker comprises at least one spacer unit.

107. The antibody-drug conjugate of claim 105 or claim 106, wherein the spacer unit or linker comprises a polyethylene glycol (PEG) moiety.

108. The antibody-drug conjugate of claim 107, wherein the PEG moiety comprises -(PEG)m- and m is an integer from 1 to 10.

109. The antibody-drug conjugate of claim 108, wherein m is 2.

110. The antibody-drug conjugate of claim 105 or claim 106, wherein the spacer unit or linker comprises an alkyl moiety.

111. The antibody-drug conjugate of claim 110, wherein the alkyl moiety comprises -(Chhjn- and n is an integer from 1 to 10.

112. The antibody-drug conjugate of claim 111 , wherein n is 2.

113. The antibody-drug conjugate of claim 111 , wherein n is 5.

114. The antibody-drug conjugate of claim 111 , wherein n is 6.

115. The antibody-drug conjugate of any one of claims 106 to 114, wherein the spacer unit attaches to the antibody or antigen binding fragment via a maleimide (Mai) moiety (“Mal-spacer unit”).

116. The antibody-drug conjugate of claim 115, wherein the Mal-spacer unit is reactive with a cysteine residue on the antibody or antigen binding fragment.

117. The antibody-drug conjugate of claim 115 or claim 116, wherein the Mal-spacer unit is joined to the antibody or antigen binding fragment via a cysteine residue on the antibody or antigen binding fragment.

118. The antibody-drug conjugate of any one of claims 115 to 117, wherein the Mal-spacer unit comprises an alkyl moiety.

119. The antibody-drug conjugate of any one of claims 115 to 117, wherein the Mal-spacer unit comprises a PEG moiety.

120. The antibody-drug conjugate of any one of claims 115 to 119, wherein the linker or Mal- spacer unit comprises a maleimidocaproyl (MC).

121. The antibody-drug conjugate of claim 120, wherein the linker or Mal-spacer unit comprises a maleimidocaproyl (MC) and at least one additional spacer unit.

122. The antibody-drug conjugate of any one of claims 115 to 119, wherein the linker or Mal- spacer unit comprises MC-(PEG)2.

123. The antibody-drug conjugate of claim 122, wherein the linker or Mal-spacer unit comprises MC-(PEG)2 and at least one additional spacer unit.

124. The antibody-drug conjugate of any one of claims 115 to 119, wherein the linker or Mal- spacer unit comprises Mai-Hex.

125. The antibody-drug conjugate of claim 124, wherein the linker or Mal-spacer unit comprises Mai-Hex and at least one additional spacer unit.

126. The antibody-drug conjugate of any one of claims 115 to 119, wherein the linker or Mal- spacer unit comprises Mal-Et.

127. The antibody-drug conjugate of claim 126, wherein the linker or Mal-spacer unit comprises Mal-Et and at least one additional spacer unit.

128. The antibody-drug conjugate of any one of claims 115 to 119, wherein the linker or Mal- spacer unit comprises Mal-Et-O-Et.

129. The antibody-drug conjugate of claim 128, wherein the linker or Mal-spacer unit comprises Mal-Et-O-Et and at least one additional spacer unit.

130. The antibody-drug conjugate of any one of claims 115 to 129, wherein the Mal-spacer unit attaches the antibody or antigen binding fragment to the splicing modulator.

131. The antibody-drug conjugate of any one of claims 115 to 130, wherein the linker comprises MC-Val-Cit-pABC.

132. The antibody-drug conjugate of any one of claims 115 to 130, wherein the linker comprises MC-(PEG)2-CO.

133. The antibody-drug conjugate of any one of claims 1 to 132, wherein the antibody or antigen binding fragment targets a neoplastic cell derived from a hematological malignancy or a solid tumor.

134. The antibody-drug conjugate of any one of claims 1 to 133, wherein the antibody or antigen binding fragment targets a neoplastic cell derived from a hematological malignancy.

135. The antibody-drug conjugate of claim 133 or claim 134, wherein the hematological malignancy is selected from a B-cell malignancy, a leukemia, a lymphoma, and a myeloma.

136. The antibody-drug conjugate of any one of claims 133 to 135, wherein the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma.

137. The antibody-drug conjugate of any one of claims 1 to 133, wherein the antibody or antigen binding fragment targets a neoplastic cell derived from a solid tumor.

138. The antibody-drug conjugate of claim 133 or claim 137, wherein the solid tumor is selected from breast cancer, gastric cancer, prostate cancer, ovarian cancer, lung cancer, uterine cancer, salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer.

139. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a HER2-expressing cell.

140. The antibody-drug conjugate of claim 139, wherein the antibody or antigen binding fragment is an anti-HER2 antibody or antigen binding fragment.

141. The antibody-drug conjugate of claim 139 or claim 140, wherein the antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO:1 (HCDR1), SEQ ID NO:2 (HCDR2), and SEQ ID NO:3 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO:4 (LCDR1), SEQ ID NO:5 (LCDR2), and SEQ ID NO:6 (LCDR3).

142. The antibody-drug conjugate of any one of claims 139 to 141 , wherein the antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 19, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:20.

143. The antibody-drug conjugate of any one of claims 139 to 142, wherein the antibody or antigen binding fragment comprises a human lgG1 heavy chain constant region.

144. The antibody-drug conjugate of any one of claims 139 to 143, wherein the antibody or antigen binding fragment comprises a human Ig kappa light chain constant region.

145. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a CD138-expressing cell.

146. The antibody-drug conjugate of claim 145, wherein the antibody or antigen binding fragment is an anti-CD138 antibody or antigen binding fragment.

147. The antibody-drug conjugate of claim 145 or claim 146, wherein the antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO:7 (HCDR1), SEQ ID NO:8 (HCDR2), and SEQ ID NO:9 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO:11 (LCDR2), and SEQ ID NO:12 (LCDR3).

148. The antibody-drug conjugate of any one of claims 145 to 147, wherein the antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:21 , and a light chain variable region comprising an amino acid sequence of SEQ ID NO:22.

149. The antibody-drug conjugate of any one of claims 145 to 148, wherein the antibody or antigen binding fragment comprises a human lgG2a heavy chain constant region.

150. The antibody-drug conjugate of any one of claims 145 to 149, wherein the antibody or antigen binding fragment comprises a human Ig kappa light chain constant region.

151. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets an EPHA2-expressing cell.

152. The antibody-drug conjugate of claim 151 , wherein the antibody or antigen binding fragment is an anti-EPHA2 antibody or antigen binding fragment.

153. The antibody-drug conjugate of claim 151 or claim 152, wherein the antibody or antigen binding fragment comprises three heavy chain complementarity determining regions (HCDR1 , HCDR2, and HCDR3) comprising amino acid sequences of SEQ ID NO:13 (HCDR1), SEQ ID NO:14 (HCDR2), and SEQ ID NO:15 (HCDR3); and three light chain complementarity determining regions (LCDR1 , LCDR2, and LCDR3) comprising amino acid sequences of SEQ ID NO:16 (LCDR1), SEQ ID NO:17 (LCDR2), and SEQ ID NO:18 (LCDR3).

154. The antibody-drug conjugate of any one of claims 151 to 153, wherein the antibody or antigen binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:23, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:24.

155. The antibody-drug conjugate of any one of claims 151 to 154, wherein the antibody or antigen binding fragment comprises a human lgG1 heavy chain constant region.

156. The antibody-drug conjugate of any one of claims 151 to 155, wherein the antibody or antigen binding fragment comprises a human Ig kappa light chain constant region.

157. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a MSLN-expressing cell.

158. The antibody-drug conjugate of claim 157, wherein the antibody or antigen binding fragment is an anti-MSLN antibody or antigen binding fragment.

159. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a FOLH1-expressing cell.

160. The antibody-drug conjugate of claim 159, wherein the antibody or antigen binding fragment is an anti-FOLH1 antibody or antigen binding fragment.

161. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a CDH6-expressing cell.

162. The antibody-drug conjugate of claim 161 , wherein the antibody or antigen binding fragment is an anti-CDH6 antibody or antigen binding fragment.

163. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a CEACAM5-expressing cell.

164. The antibody-drug conjugate of claim 163, wherein the antibody or antigen binding fragment is an anti-CEACAM5 antibody or antigen binding fragment.

165. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a CFC1 B-expressing cell.

166. The antibody-drug conjugate of claim 165, wherein the antibody or antigen binding fragment is an anti-CFC1 B antibody or antigen binding fragment.

167. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets an ENPP3-expressing cell.

168. The antibody-drug conjugate of claim 167, wherein the antibody or antigen binding fragment is an anti-ENPP3 antibody or antigen binding fragment.

169. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a FOLR1-expressing cell.

170. The antibody-drug conjugate of claim 169, wherein the antibody or antigen binding fragment is an anti-FOLR1 antibody or antigen binding fragment.

171. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a HAVCRI-expressing cell.

172. The antibody-drug conjugate of claim 171 , wherein the antibody or antigen binding fragment is an anti-HAVCR1 antibody or antigen binding fragment.

173. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a KIT-expressing cell.

174. The antibody-drug conjugate of claim 173, wherein the antibody or antigen binding fragment is an anti-KIT antibody or antigen binding fragment.

175. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a MET-expressing cell.

176. The antibody-drug conjugate of claim 175, wherein the antibody or antigen binding fragment is an anti-MET antibody or antigen binding fragment.

177. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a MUC16-expressing cell.

178. The antibody-drug conjugate of claim 177, wherein the antibody or antigen binding fragment is an anti-MUC16 antibody or antigen binding fragment.

179. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a SLC39A6-expressing cell.

180. The antibody-drug conjugate of claim 179, wherein the antibody or antigen binding fragment is an anti-SLC39A6 antibody or antigen binding fragment.

181. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a SLC44A4-expressing cell.

182. The antibody-drug conjugate of claim 181 , wherein the antibody or antigen binding fragment is an anti-SLC44A4 antibody or antigen binding fragment.

183. The antibody-drug conjugate of any one of claims 1 to 138, wherein the antibody or antigen binding fragment targets a STEAP1 -expressing cell.

184. The antibody-drug conjugate of claim 183, wherein the antibody or antigen binding fragment is an anti-STEAP1 antibody or antigen binding fragment.

185. The antibody-drug conjugate of any one of claims 1 to 184, wherein p is from 1 to 10.

186. The antibody-drug conjugate of any one of claims 1 to 185, wherein p is from 2 to 8.

187. The antibody-drug conjugate of any one of claims 1 to 186, wherein p is from 4 to 8.

188. The antibody-drug conjugate of any one of claims 1 to 187, wherein p is 4.

189. The antibody-drug conjugate of any one of claims 1 to 187, wherein p is 8.

190. A compound of Formula (I):pharmaceutically acceptable salt thereof, wherein:Y is chosen from O, S, NR6, and CR6R7;R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R4is chosen from hydrogen, C1-C6 alkyl groups, -C(=0)-(Ci-C6alkyl) groups, -C(=0)- (C3-C8 carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, and -C(=0)-NR6R7;R5is chosen from hydrogen, hydroxyl, -CH2-OH, -CO2H, -C(=0)-0-(Ci-C6alkyl) groups, -C(=0)-NR6R7, -NR6-C(=0)-R8, -0-C(=0)-NR6R7, -NR6-C(=0)-R8, and -NR6-C(=0)-NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)- O-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R1, R2, R3, R4, R5, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, -C02H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, C1-C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl).

191. The compound of claim 190, wherein the compound is a compound of Formula (la):pharmaceutically acceptable salt thereof, wherein:R9is chosen from C3-C8 heterocyclyl groups; andR10is chosen from H and C1-C6 alkyl groups,wherein R9and R10are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C3 alkyl groups, C1-C3 alkoxy groups, -IMH2, -NH-(CI-C3 alkyl), and -N-(CI-C3 alkyl)2.

192. The compound of claim 190 or claim 191 , wherein the compound is a compound ofOO L Ri iFormulapharmaceutically acceptable salt thereof, wherein:R11is chosen fromwherein * denotes the point of connectivity of R11to the remainder of the compound; andR12and R13are each independently chosen from H and methyl.

193. The compound of claim 190, wherein the compound is H1 , or a pharmaceutically acceptable salt thereof.

194. The compound of claim 190, wherein the compound is H2, or a pharmaceutically acceptable salt thereof.

195. The compound of claim 190, wherein the compound is H3, or a pharmaceutically acceptable salt thereof.

196. The compound of claim 190, wherein the compound is H12, or a pharmaceutically acceptable salt thereof.

197. A compound of Formula (II):(II), or a pharmaceutically acceptable salt thereof, wherein:X is NR6R7;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, -C(=0)-0-R8, -(CrCe alkyl)-0-C(=0)-R8, and -(CrCe alkyl)-NH-C(=0)-R8; andR8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups,wherein R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, C1-C6 alkyl groups, -0-(Ci-C6alkyl) groups, - CO2H, -C(=0)-0-(Ci-Ce alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl)groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, C1-C6 alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CrC3alkyl), and -NH-C(=0)-0-(Ci-C3alkyl).

198. The compound of claim 197, wherein the compound is a compound of Formula (lla):(lla), or a pharmaceutically acceptable salt thereof, wherein:Z is chosen from NR9and O;R9is chosen from hydrogen and C1-C6 alkyl groups;R10and R11are each independently chosen from hydrogen, halogens, hydroxyl, C1-C6 alkyl groups, -0-(CrCe alkyl) groups, -CO2H, -C(=0)-0-(CrCe alkyl) groups, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, CrCe alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups;R12is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, C3-C8 heterocyclyl groups,wherein R9, R10, R11, and R12are each independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, and C1 -C3 haloalkyl groups; andt is an integer chosen from 1 , 2, 3, 4, 5, and 6.

199. The compound of claim 197 or claim 198, wherein the compound is a compound ofFormula (lib):(lib), or a pharmaceutically acceptable salt thereof, wherein:wherein * denotes the point of connectivity of R13to the remainder of the compound; andR14and R15are each independently chosen from hydrogen and methyl.

200. The compound of claim 197, wherein the compound is H4, or a pharmaceutically acceptable salt thereof.

201. The compound of claim 197, wherein the compound is H 13, or a pharmaceutically acceptable salt thereof.

202. The compound of claim 197, wherein the compound is H14, or a pharmaceutically acceptable salt thereof.

203. The compound of claim 197, wherein the compound is H 15, or a pharmaceutically acceptable salt thereof.

204. The compound of claim 197, wherein the compound is H16, or a pharmaceutically acceptable salt thereof.

205. The compound of claim 197, wherein the compound is H 17, or a pharmaceutically acceptable salt thereof.

206. The compound of claim 197, wherein the compound is H 18, or a pharmaceutically acceptable salt thereof.

207. The compound of claim 197, wherein the compound is H 19, or a pharmaceutically acceptable salt thereof.

208. The compound of claim 197, wherein the compound is H20, or a pharmaceutically acceptable salt thereof.

209. The compound of claim 197, wherein the compound is H21 , or a pharmaceutically acceptable salt thereof.

210. The compound of claim 197, wherein the compound is H23, or a pharmaceutically acceptable salt thereof.

211. The compound of claim 197, wherein the compound is H24, or a pharmaceutically acceptable salt thereof.

212. A compound of Formula (III):pharmaceutically acceptable salt thereof, wherein:R1, R2, and R3are each independently chosen from hydrogen, hydroxyl, -0-(Ci-C6alkyl) groups, -0-C(=0)-(Ci-C6alkyl) groups, -C(=0)-0-(Ci-C6alkyl) groups, and C1-C6 alkyl groups;R6and R7are each independently chosen from hydrogen, -R8, -C(=0)-R8, and -C(=0)-O-R8;R8is chosen from C1-C6 alkyl groups, C3-C8 carbocyclyl groups, and C3-C8 heterocyclyl groups; andwherein R1, R2, R3, R6, R7, and R8are each independently substituted with 0 to 3 groups independently chosen from halogens, hydroxyl, CrCe alkyl groups, -0-(Ci-Ce alkyl) groups, - C02H, -C(=0)-(Ci-Ce alkyl) groups, -C(=0)-(C3-Cs carbocyclyl) groups, -C(=0)-(C3-Cs heterocyclyl) groups, -NR6R7, C3-C8 carbocyclyl groups, CrCe alkylhydroxy groups, C1-C6 alkylalkoxy groups, benzyl groups, and C3-C8 heterocyclyl groups, each of which may be independently substituted with 0 or 1 group chosen from halogens, hydroxyl, C1 -C3 alkyl groups, C1 -C3 alkoxy groups, C1 -C3 haloalkyl groups, -NH-C(=0)(CI-C3 alkyl), and -NH-C(=0)-0-(CI-C3 alkyl); andwherein * denotes the point of connectivity of R9to the remainder of the compound.

213. The compound of claim 212, wherein the compound is H5, or a pharmaceutically acceptable salt thereof.

214. The compound of claim 212, wherein the compound is H6, or a pharmaceutically acceptable salt thereof.

215. The compound of claim 212, wherein the compound is H7, or a pharmaceutically acceptable salt thereof.

216. The compound of claim 212, wherein the compound is H8, or a pharmaceutically acceptable salt thereof.

217. The compound of claim 212, wherein the compound is H9, or a pharmaceutically acceptable salt thereof.

218. The compound of claim 212, wherein the compound is H 10, or a pharmaceutically acceptable salt thereof.

219. The compound of claim 212, wherein the compound is H22, or a pharmaceutically acceptable salt thereof.

220. A pharmaceutical composition comprising the compound of any one of claims 190 to 219, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

221. A composition comprising multiple copies of the antibody-drug conjugate of any one of claims 1 to 189, wherein the average p of the antibody-drug conjugates in the composition is from about 3.5 to about 5.5.

222. The composition of claim 221 , wherein the average p of the antibody-drug conjugates in the composition is about 4.

223. A composition comprising multiple copies of the antibody-drug conjugate of any one of claims 1 to 189, wherein the average p of the antibody-drug conjugates in the composition is from about 7 to about 9.

224. The composition of claim 223, wherein the average p of the antibody-drug conjugates in the composition is about 8.

225. A method of treating a subject having or suspected of having a neoplastic disorder, comprising administering to the subject a therapeutically effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224.

226. The method of claim 225, wherein the neoplastic disorder is a hematological malignancy or a solid tumor.

227. The method of claim 225 or claim 226, wherein the neoplastic disorder is ahematological malignancy.

228. The method of claim 227, wherein the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma.

229. The method of claim 225 or claim 226, wherein the neoplastic disorder is a solid tumor.

230. The method of claim 229, wherein the solid tumor is selected from breast cancer, gastric cancer, prostate cancer, ovarian cancer, lung cancer, uterine cancer, salivary duct carcinoma,melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer.

231. The method of any one of claims 225 to 230, wherein the subject has one or more neoplastic cells which express a target antigen.

232. The method of claim 231 , wherein the target antigen is HER2.

233. The method of claim 231 or claim 232, wherein the one or more neoplastic cells are derived from a HER2-expressing breast cancer, ovarian cancer, gastric cancer, lung cancer, uterine cancer, osteosarcoma, or salivary duct carcinoma.

234. The method of claim 233, wherein the lung cancer is lung adenocarcinoma and / or the uterine cancer is uterine serous endometrial carcinoma.

235. The method of any one of claims 232 to 234, wherein the subject is non-responsive or poorly responsive to treatment with (a) an anti-HER2 antibody when administered alone and / or (b) a splicing modulator when administered alone.

236. The method of any one of claims 232 to 235, wherein the subject is intolerant, non- responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

237. The method of claim 231 , wherein the target antigen is CD138.

238. The method of claim 231 or claim 237, wherein the one or more neoplastic cells are derived from a CD138-expressing multiple myeloma.

239. The method of claim 237 or claim 238, wherein the subject is non-responsive or poorly responsive to treatment with (a) an anti-CD138 antibody when administered alone and / or (b) a splicing modulator when administered alone.

240. The method of any one of claims 237 to 239, wherein the subject is intolerant, non- responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

241. The method of claim 231 , wherein the target antigen is EPHA2.

242. The method of claim 231 or claim 241 , wherein the one or more neoplastic cells are derived from an EPHA2-expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer.

243. The method of claim 241 or claim 242, wherein the subject is non-responsive or poorly responsive to treatment with (a) an anti-EPHA2 antibody when administered alone and / or (b) a splicing modulator when administered alone.

244. The method of any one of claims 241 to 243, wherein the subject is intolerant, non- responsive, or poorly responsive to treatment with a splicing modulator when administered alone.

245. A method of reducing or inhibiting growth of a tumor in a subject having or suspected of having a neoplastic disorder, comprising administering to the subject a therapeutically effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224.

246. The method of claim 245, wherein the tumor comprises one or more neoplastic cells which express a target antigen.

247. The method of claim 246, wherein the target antigen is HER2.

248. The method of claim 246 or claim 247, wherein the one or more neoplastic cells are derived from a HER2-expressing breast cancer, ovarian cancer, gastric cancer, lung cancer, uterine cancer, osteosarcoma, or salivary duct carcinoma.

249. The method of claim 248, wherein the lung cancer is lung adenocarcinoma and / or the uterine cancer is uterine serous endometrial carcinoma.

250. The method of any one of claims 247 to 249, wherein the tumor is resistant or refractory to treatment with (a) an anti-HER2 antibody when administered alone and / or (b) a splicing modulator when administered alone.

251. The method of claim 246, wherein the target antigen is CD138.

252. The method of claim 246 or claim 251 , wherein the one or more neoplastic cells are derived from a CD138-expressing multiple myeloma.

253. The method of claim 251 or claim 252, wherein the tumor is resistant or refractory to treatment with (a) an anti-CD138 antibody when administered alone and / or (b) a splicing modulator when administered alone.

254. The method of claim 246, wherein the target antigen is EPHA2.

255. The method of claim 246 or claim 254, wherein the one or more neoplastic cells are derived from an EPHA2-expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer.

256. The method of claim 254 or claim 255, wherein the tumor is resistant or refractory to treatment with (a) an anti-EPHA2 antibody when administered alone and / or (b) a splicing modulator when administered alone.

257. A method of determining whether a subject having or suspected of having a neoplastic disorder will be responsive to treatment with the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224, comprising providing a biological sample from the subject and contacting the biological sample with the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224.

258. The method of claim 257, wherein the biological sample is a tumor sample.

259. The method of claim 258, wherein the tumor sample is a tumor biopsy or blood sample.

260. The method of claim 259, wherein the blood sample is selected from blood, a blood fraction, or a cell obtained from the blood or blood fraction.

261. The method of any one of claims 257 to 260, wherein the subject has one or more neoplastic cells which express a target antigen.

262. The method of claim 261 , wherein the target antigen is HER2.

263. The method of claim 261 or claim 262, wherein the one or more neoplastic cells are derived from a HER2-expressing breast cancer, ovarian cancer, gastric cancer, lung cancer, uterine cancer, osteosarcoma, or salivary duct carcinoma.

264. The method of claim 263, wherein the lung cancer is lung adenocarcinoma and / or the uterine cancer is uterine serous endometrial carcinoma.

265. The method of claim 261 , wherein the target antigen is CD138.

266. The method of claim 261 or claim 265, wherein the one or more neoplastic cells are derived from a CD138-expressing multiple myeloma.

267. The method of claim 261 , wherein the target antigen is EPHA2.

268. The method of claim 261 or claim 267, wherein the one or more neoplastic cells are derived from an EPHA2-expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer.

269. An antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224 for use in the treatment of a neoplastic disorder.

270. The antibody-drug conjugate, compound, or composition for use of claim 269, wherein the neoplastic disorder is characterized by having one or more neoplastic cells which express a target antigen.

271. The antibody-drug conjugate, compound, or composition for use of claim 270, wherein the target antigen is HER2.

272. The antibody-drug conjugate, compound, or composition for use of claim 270 or claim 271 , wherein the neoplastic disorder is a HER2-expressing breast cancer, ovarian cancer, gastric cancer, lung cancer, uterine cancer, osteosarcoma, or salivary duct carcinoma.

273. The antibody-drug conjugate, compound, or composition of claim 272, wherein the lung cancer is lung adenocarcinoma and / or the uterine cancer is uterine serous endometrial carcinoma.

274. The antibody-drug conjugate, compound, or composition for use of claim 270, wherein the target antigen is CD138.

275. The antibody-drug conjugate, compound, or composition for use of claim 270 or claim274, wherein the neoplastic disorder is a CD138-expressing multiple myeloma.

276. The antibody-drug conjugate, compound, or composition for use of claim 270, wherein the target antigen is EPHA2.

277. The antibody-drug conjugate, compound, or composition for use of claim 270 or claim 276, wherein the neoplastic disorder is an EPHA2-expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer.

278. Use of an antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224 in the treatment of a neoplastic disorder.

279. The use of claim 278, wherein the neoplastic disorder is characterized by having one or more neoplastic cells which express a target antigen.

280. The use of claim 279, wherein the target antigen is HER2.

281. The use of claim 279 or claim 280, wherein the neoplastic disorder is a HER2- expressing breast cancer, ovarian cancer, gastric cancer, lung cancer, uterine cancer, osteosarcoma, or salivary duct carcinoma.

282. The use of claim 281 , wherein the lung cancer is lung adenocarcinoma and / or the uterine cancer is uterine serous endometrial carcinoma.

283. The use of claim 279, wherein the target antigen is CD138.

284. The use of claim 279 or claim 283, wherein the neoplastic disorder is a CD138- expressing multiple myeloma.

285. The use of claim 279, wherein the target antigen is EPHA2.

286. The use of claim 279 or claim 285, wherein the neoplastic disorder is an EPHA2- expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer.

287. Use of an antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224 in a method of manufacturing a medicament for the treatment of a neoplastic disorder.

288. The use of claim 287, wherein the neoplastic disorder is characterized by having one or more neoplastic cells which express a target antigen.

289. The use of claim 288, wherein the target antigen is HER2.

290. The use of claim 288 or claim 289, wherein the neoplastic disorder is a HER2- expressing breast cancer, ovarian cancer, gastric cancer, lung cancer, uterine cancer, osteosarcoma, or salivary duct carcinoma.

291. The use of claim 290, wherein the lung cancer is lung adenocarcinoma and / or the uterine cancer is uterine serous endometrial carcinoma.

292. The use of claim 288, wherein the target antigen is CD138.

293. The use of claim 288 or claim 292, wherein the neoplastic disorder is a CD138- expressing multiple myeloma.

294. The use of claim 288, wherein the target antigen is EPHA2.

295. The use of claim 288 or claim 294, wherein the neoplastic disorder is an EPHA2- expressing breast cancer, prostate cancer, ovarian cancer, lung cancer, melanoma, colon cancer, or esophageal cancer.

296. A method of producing the antibody-drug conjugate of any one of claims 1 to 189, comprising reacting an antibody or antigen binding fragment with a linker joined to a splicing modulator under conditions that allow conjugation.

297. A method of inducing at least one neoantigen, comprising contacting a neoplastic cell with an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224, thereby inducing production of at least one neoantigen.

298. The method of claim 297, wherein the neoplastic cell is present in an in vitro cell culture.

299. The method of claim 297 or claim 298, wherein the neoplastic cell is obtained from a subject.

300. The method of claim 297, wherein the neoplastic cell is present in a subject.

301. The method of any one of claims 297 to 300, wherein the neoplastic cell is derived from a hematological malignancy or a solid tumor.

302. The method of claim 301 , wherein the hematological malignancy is selected from a 13- cell malignancy, a leukemia, a lymphoma, and a myeloma.

303. The method of claim 301 or claim 302, wherein the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma.

304. The method of claim 301 , wherein the solid tumor is selected from breast cancer, gastric cancer, prostate cancer, ovarian cancer, lung cancer, uterine cancer, salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer.

305. A method of inducing at least one neoantigen and / or a T-cell response in a subject having or suspected of having a neoplastic disorder, comprising administering to the subject an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224.

306. A method of treating a subject having or suspected of having a neoplastic disorder, comprising administering to the subject an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224, wherein administration of the compound, antibody-drug conjugate, or composition induces at least one neoantigen and / or a T-cell response.

307. The method of claim 305 or claim 306, wherein the amount of the compound, antibody- drug conjugate, or composition administered is reduced due to induction of at least one neoantigen and / or a T-cell response, as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

308. The method of any one of claims 305 to 307, wherein the administered amount of the compound, antibody-drug conjugate, or composition is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

309. The method of any one of claims 305 to 308, wherein the compound, antibody-drug conjugate, or composition is administered at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90% less frequently, as compared to a standard dosing regimen of thecompound, antibody-drug conjugate, or composition.

310. The method of any one of claims 305 to 309, wherein the administered amount and / or dosage of the compound, antibody-drug conjugate, or composition results in lower systemic toxicity and / or improved tolerance.

311. The method of any one of claims 305 to 310, further comprising administering at least one additional therapy.

312. The method of claim 311 , wherein the amount of the compound, antibody-drug conjugate, composition, and / or the at least one additional therapy administered is reduced due to induction of at least one neoantigen and / or a T-cell response, as compared to a standard dosage of the compound, antibody-drug conjugate, composition, and / or the at least one additional therapy.

313. The method of claim 311 or claim 312, wherein the administered amount of the compound, antibody-drug conjugate, composition, and / or the at least one additional therapy is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the splicing modulator, antibody-drug conjugate, composition, and / or the at least one additional therapy.

314. The method of any one of claims 311 to 313, wherein the compound, antibody-drug conjugate, composition, and / or the at least one additional therapy is administered at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90% less frequently, as compared to a standard dosing regimen of the compound, antibody-drug conjugate, composition, and / or the at least one additional therapy.

315. The method of any one of claims 311 to 314, wherein the administered amount and / or dosage of the compound, antibody-drug conjugate, composition, and / or the at least one additional therapy results in lower systemic toxicity and / or improved tolerance.

316. The method of any one of claims 311 to 315, wherein administration of the compound, antibody-drug conjugate, or composition is initiated before administration of the at least one additional therapy.

317. The method of any one of claims 311 to 315, wherein administration of the compound, antibody-drug conjugate, or composition is initiated after administration of the at least one additional therapy.

318. The method of any one of claims 311 to 315, wherein administration of the compound, antibody-drug conjugate, or composition is initiated concurrently with administration of the at least one additional therapy.

319. The method of any one of claims 305 to 318, wherein administration of the compound, antibody-drug conjugate, or composition is repeated at least once after initial administration.

320. The method of claim 319, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced as compared to the amount used for initial administration.

321. The method of claim 319 or claim 320, wherein the amount of the compound, antibody- drug conjugate, or composition used for repeated administration is reduced as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

322. The method of any one of claims 319 to 321 , wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

323. The method of any one of claims 311 to 322, wherein administration of the at least one additional therapy is repeated at least once after initial administration.

324. The method of claim 323, wherein the amount of the at least one additional therapy used for repeated administration is reduced as compared to the amount used for initial administration.

325. The method of claim 323 or claim 324, wherein the amount of the at least one additional therapy used for repeated administration is reduced as compared to a standard dosage of the at least one additional therapy.

326. The method of any one of claims 323 to 325, wherein the amount of the at least one additional therapy used for repeated administration is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the at least one additional therapy.

327. The method of any one of claims 319 to 326, wherein repeated administration of the compound, antibody-drug conjugate, or composition is concurrent with repeated administration of the at least one additional therapy.

328. The method of any one of claims 319 to 326, wherein repeated administration of the compound, antibody-drug conjugate, or composition is sequential or staggered with repeated administration of the at least one additional therapy.

329. The method of any one of claims 311 to 328, wherein the at least one additional therapy comprises administering a checkpoint inhibitor.

330. The method of claim 329, wherein the subject is intolerant, non-responsive, or poorly responsive to the checkpoint inhibitor when administered alone.

331. The method of claim 329 or claim 330, wherein the checkpoint inhibitor targets CTLA4, PD1 , PDL1 , 0X40, CD40, GITR, LAG3, TIM3, and / or KIR.

332. The method of any one of claims 329 to 331 , wherein the checkpoint inhibitor targets CTLA4, 0X40, CD40, and / or GITR.

333. The method of any one of claims 329 to 332, wherein the checkpoint inhibitor comprises a cytotoxic T-lymphocyte-associated antigen 4 pathway (CTLA4) inhibitor.

334. The method of claim 333, wherein the CTLA4 inhibitor is an anti-CTLA4 antibody.

335. The method of claim 334, wherein the anti-CTLA4 antibody is ipilimumab.

336. The method of any one of claims 329 to 332, wherein the checkpoint inhibitor comprises a programmed death-1 pathway (PD1) inhibitor.

337. The method of claim 336, wherein the PD1 inhibitor is an anti-PD1 antibody.

338. The method of claim 337, wherein the anti-PD1 antibody is nivolumab.

339. The method of claim 336, wherein the PD1 inhibitor is an anti-PDL1 antibody.

340. The method of claim 339, wherein the anti-PDL1 antibody is atezolizumab.

341. The method of any one of claims 329 to 332, wherein the checkpoint inhibitor comprises a CTLA4 inhibitor and a PD1 inhibitor.

342. The method of claim 341 , wherein the CTLA4 inhibitor is an anti-CTLA4 antibody.

343. The method of claim 342, wherein the anti-CTLA4 antibody is ipilimumab.

344. The method of claim 341 , wherein the PD1 inhibitor is an anti-PD1 antibody.

345. The method of claim 344, wherein the anti-PD1 antibody is nivolumab.

346. The method of claim 341 , wherein the PD1 inhibitor is an anti-PDL1 antibody.

347. The method of claim 346, wherein the anti-PDL1 antibody is atezolizumab.

348. The method of any one of claims 311 to 328, wherein the at least one additional therapy comprises administering a neoantigen vaccine.

349. The method of claim 348, wherein the compound, antibody-drug conjugate, or composition is administered before administration of the neoantigen vaccine.

350. The method of claim 348, wherein the compound, antibody-drug conjugate, or composition is administered after administration of the neoantigen vaccine.

351. The method of claim 348, wherein the compound, antibody-drug conjugate, or composition is administered concurrently with administration of the neoantigen vaccine.

352. The method of any one of claims 348 to 351 , wherein administration of the compound, antibody-drug conjugate, or composition is repeated at least once after initial administration.

353. The method of claim 352, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced as compared to the amount used for initial administration.

354. The method of any one of claims 348 to 353, wherein the neoantigen vaccine comprises at least one neoantigen peptide.

355. The method of claim 354, wherein the at least one neoantigen peptide ranges from about 10 to about 35 amino acids in length.

356. The method of claim 354 or claim 355, wherein the at least one neoantigen peptide ranges from about 15 to about 25 amino acids in length.

357. The method of any one of claims 354 to 356, wherein the at least one neoantigen peptide comprises one or more than one neoantigen sequence.

358. The method of claim 357, wherein the neoantigen sequence is a neoantigen sequence specific to the subject.

359. The method of claim 357, wherein the neoantigen sequence is a universal neoantigen sequence.

360. The method of claim 358, wherein the neoantigen sequence is a personalized neoantigen vaccine for the subject.

361. The method of claim 360, wherein the neoantigen sequence has been identified by sequencing at least one neoantigen induced in the subject by administering an effective amount of the compound, antibody-drug conjugate, or composition.

362. The method of claim 360 or claim 361 , wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in the subject.

363. The method of claim 359, wherein the neoantigen sequence is a universal neoantigen vaccine.

364. The method of claim 363, wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, or at least 45% of subjects in a population of subjects suffering from the neoplastic disorder.

365. The method of claim 363 or claim 364, wherein the neoantigen sequence is capable of eliciting a T-cell response against a tumor present in at least 1%, at least 5%, or at least 10% of a population of subjects suffering from the neoplastic disorder.

366. The method of any one of claims 354 to 365, wherein the at least one neoantigen peptide comprises a neoantigen sequence induced by contacting a neoplastic cell with an effective amount of the splicing modulator, antibody-drug conjugate, or composition.

367. The method of claim 348, wherein the neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable carrier.

368. The method of claim 367, wherein the at least one neoantigen peptide is linked to the pharmaceutically acceptable carrier.

369. The method of claim 367 or claim 368, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

370. The method of any one of claims 367 to 369, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are covalently attached via a linker.

371. The method of any one of claims 367 to 369, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are expressed as a fusion protein.

372. The method of claim 348, wherein the neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable diluent.

373. The method of claim 348, wherein the neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable adjuvant.

374. The method of claim 366, wherein the neoplastic cell is present in an in vitro cell culture.

375. The method of claim 366 or claim 374, wherein the neoplastic cell is obtained from the subject.

376. The method of claim 366, wherein the neoplastic cell is present in the subject.

377. The method of any one of claims 348 to 353, wherein the neoantigen vaccine comprises at least one neoantigen mRNA.

378. The method of claim 377, wherein the at least one neoantigen mRNA encodes one or more than one neoantigen sequence.

379. The method of claim 378, wherein the neoantigen sequence is a neoantigen sequence specific to the subject.

380. The method of claim 378, wherein the neoantigen sequence is a universal neoantigen sequence.

381. The method of claim 379, wherein the neoantigen sequence is a personalized neoantigen vaccine for the subject.

382. The method of claim 381 , wherein the neoantigen sequence has been identified by sequencing at least one neoantigen induced in the subject by administering an effective amount of the compound, antibody-drug conjugate, or composition.

383. The method of claim 381 or claim 382, wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in the subject.

384. The method of claim 380, wherein the neoantigen sequence is a universal neoantigen vaccine.

385. The method of claim 384, wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, or at least 45% of subjects in a population of subjects suffering from the neoplastic disorder.

386. The method of claim 384 or claim 385, wherein the neoantigen sequence is capable of eliciting a T-cell response against a tumor present in at least 1%, at least 5%, or at least 10% of a population of subjects suffering from the neoplastic disorder.

387. The method of any one of claims 378 to 386, wherein the at least one neoantigen mRNA encodes a neoantigen sequence induced by contacting a neoplastic cell with an effective amount of the compound, antibody-drug conjugate, or composition.

388. The method of claim 377, wherein the neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable carrier.

389. The method of claim 388, wherein the at least one neoantigen mRNA is linked to the pharmaceutically acceptable carrier.

390. The method of claim 388 or claim 389, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

391. The method of claim 377, wherein the neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable diluent.

392. The method of claim 377, wherein the neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable adjuvant.

393. The method of any one of claims 377 to 392, wherein the neoantigen mRNA is encapsulated by an encapsulating agent.

394. The method of claim 393, wherein the encapsulating agent is a liposome.

395. The method of claim 393, wherein the encapsulating agent is a nanoparticle.

396. The method of claim 387, wherein the neoplastic cell is present in an in vitro cell culture.

397. The method of claim 387 or claim 396, wherein the neoplastic cell is obtained from the subject.

398. The method of claim 387, wherein the neoplastic cell is present in the subject.

399. The method of any one of claims 311 to 328, wherein the at least one additional therapy comprises administering a cytokine or cytokine analog.

400. The method of claim 399, wherein the subject is intolerant, non-responsive, or poorly responsive to the cytokine or cytokine analog when administered alone.

401. The method of claim 399 or claim 400, wherein the cytokine or cytokine analog comprises a T-cell enhancer.

402. The method of any one of claims 399 to 401 , wherein the cytokine or cytokine analog comprises IL-2, IL-10, IL-12, IL-15, IFNy, and / or TNFa.

403. The method of any one of claims 311 to 328, wherein the at least one additional therapy comprises administering engineered tumor-targeting T-cells.

404. The method of any one of claims 305 to 403, further comprising detecting one or more neoantigens and / or a T-cell response in the subject after administration of the compound, antibody-drug conjugate, or composition.

405. The method of claim 404, further comprising continuing administration of the compound, antibody-drug conjugate, or composition if one or more neoantigens and / or a T-cell response is detected.

406. The method of claim 404 or claim 405, further comprising continuing administration of the compound, antibody-drug conjugate, or composition less frequently and / or at a reduced dosage if one or more neoantigens and / or a T-cell response is detected.

407. The method of any one of claims 404 to 406, wherein detecting one or moreneoantigens and / or a T-cell response in the subject indicates efficacy of treatment with the compound, antibody-drug conjugate, or composition.

408. The method of any one of claims 305 to 407, wherein the subject has a non- synonymous mutational burden of about 150 mutations or less.

409. The method of any one of claims 305 to 408, wherein the subject has a non- synonymous mutational burden of about 100 mutations or less.

410. The method of any one of claims 305 to 409, wherein the subject has a non- synonymous mutational burden of about 50 mutations or less.

411. The method of any one of claims 305 to 410, wherein the neoplastic disorder is a hematological malignancy or a solid tumor.

412. The method of claim 411 , wherein the hematological malignancy is selected from a 13- cell malignancy, a leukemia, a lymphoma, and a myeloma.

413. The method of claim 411 or claim 412, wherein the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma.

414. The method of claim 411 , wherein the solid tumor is selected from breast cancer, gastric cancer, prostate cancer, ovarian cancer, lung cancer, uterine cancer, salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer.

415. A method of treating a subject having or suspected of having a neoplastic disorder, comprising:(a) administering to the subject an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or thecomposition of any one of claims 220 to 224, wherein administration of the compound, antibody- drug conjugate, or composition induces at least one neoantigen and / or a T-cell response;(b) detecting one or more neoantigens and / or a T-cell response in the subject after administration of the compound, antibody-drug conjugate, or composition; and(c) continuing administration of the compound, antibody-drug conjugate, or composition if one or more neoantigens and / or a T-cell response is detected.

416. The method of claim 415, wherein detecting one or more neoantigens and / or a T-cell response in the subject indicates efficacy of treatment with the compound, antibody-drug conjugate, or composition.

417. A method of treating a subject having or suspected of having a neoplastic disorder, comprising administering to the subject an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224; and at least one additional therapy.

418. The method of claim 417, wherein the at least one additional therapy comprises at least one, at least two, at least three, at least four, or at least five additional therapies.

419. The method of claim 417 or claim 418, wherein administration of the compound, antibody-drug conjugate, or composition induces at least one neoantigen and / or a T-cell response.

420. The method of any one of claims 417 to 419, wherein the administered amount of the compound, antibody-drug conjugate, or composition and / or the at least one additional therapy is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to astandard dosage of the compound, antibody-drug conjugate, or composition and / or the at least one additional therapy.

421. The method of any one of claims 417 to 420, wherein the compound, antibody-drug conjugate, or composition and / or the at least one additional therapy is administered at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90% less frequently, as compared to a standard dosing regimen of the compound, antibody-drug conjugate, or composition and / or the at least one additional therapy.

422. The method of any one of claims 417 to 421 , wherein the administered amount and / or dosage of the compound, antibody-drug conjugate, or composition and / or the at least one additional therapy results in lower systemic toxicity and / or improved tolerance.

423. The method of any one of claims 417 to 422, wherein administration of the compound, antibody-drug conjugate, or composition is initiated before administration of the at least one additional therapy.

424. The method of any one of claims 417 to 422, wherein administration of the compound, antibody-drug conjugate, or composition is initiated after administration of the at least one additional therapy.

425. The method of any one of claims 417 to 422, wherein administration of the compound, antibody-drug conjugate, or composition is initiated concurrently with administration of the at least one additional therapy.

426. The method of any one of claims 417 to 425, wherein administration of the compound, antibody-drug conjugate, or composition is repeated at least once after initial administration.

427. The method of claim 426, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced as compared to the amount used for initial administration.

428. The method of claim 426 or claim 427, wherein the amount of the compound, antibody- drug conjugate, or composition used for repeated administration is reduced as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

429. The method of any one of claims 426 to 428, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced by 10%,15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

430. The method of any one of claims 417 to 429, wherein administration of the at least one additional therapy is repeated at least once after initial administration.

431. The method of claim 430, wherein the amount of the at least one additional therapy used for repeated administration is reduced as compared to the amount used for initial administration.

432. The method of claim 430 or claim 431 , wherein the amount of the at least one additional therapy used for repeated administration is reduced as compared to a standard dosage of the at least one additional therapy.

433. The method of any one of claims 430 to 432, wherein the amount of the at least one additional therapy used for repeated administration is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the at least one additional therapy.

434. The method of any one of claims 426 to 433, wherein repeated administration of the compound, antibody-drug conjugate, or composition is concurrent with repeated administration of the at least one additional therapy.

435. The method of any one of claims 426 to 433, wherein repeated administration of the compound, antibody-drug conjugate, or composition is sequential or staggered with repeated administration of the at least one additional therapy.

436. The method of any one of claims 417 to 435, wherein the at least one additional therapy comprises administering a checkpoint inhibitor.

437. The method of claim 436, wherein the subject is intolerant, non-responsive, or poorly responsive to the checkpoint inhibitor when administered alone.

438. The method of claim 436 or claim 437, wherein the checkpoint inhibitor targets CTLA4, PD1 , PDL1 , 0X40, CD40, GITR, LAG 3, TIM3, and / or KIR.

439. The method of any one of claims 436 to 438, wherein the checkpoint inhibitor targets CTLA4, 0X40, CD40, and / or GITR.

440. The method of any one of claims 436 to 439, wherein the checkpoint inhibitor comprises a cytotoxic T-lymphocyte-associated antigen 4 pathway (CTLA4) inhibitor.

441. The method of claim 440, wherein the CTLA4 inhibitor is an anti-CTLA4 antibody.

442. The method of claim 441 , wherein the anti-CTLA4 antibody is ipilimumab.

443. The method of any one of claims 436 to 439, wherein the checkpoint inhibitor comprises a programmed death-1 pathway (PD1) inhibitor.

444. The method of claim 443, wherein the PD1 inhibitor is an anti-PD1 antibody.

445. The method of claim 444, wherein the anti-PD1 antibody is nivolumab.

446. The method of claim 443, wherein the PD1 inhibitor is an anti-PDL1 antibody.

447. The method of claim 446, wherein the anti-PDL1 antibody is atezolizumab.

448. The method of any one of claims 436 to 439, wherein the checkpoint inhibitor comprises a CTLA4 inhibitor and a PD1 inhibitor.

449. The method of claim 448, wherein the CTLA4 inhibitor is an anti-CTLA4 antibody.

450. The method of claim 449, wherein the anti-CTLA4 antibody is ipilimumab.

451. The method of claim 448, wherein the PD1 inhibitor is an anti-PD1 antibody.

452. The method of claim 451 , wherein the anti-PD1 antibody is nivolumab.

453. The method of claim 448, wherein the PD1 inhibitor is an anti-PDL1 antibody.

454. The method of claim 453, wherein the anti-PDL1 antibody is atezolizumab.

455. The method of any one of claims 417 to 435, wherein the at least one additional therapy comprises administering a neoantigen vaccine.

456. The method of claim 455, wherein the compound, antibody-drug conjugate, or composition is administered before administration of the neoantigen vaccine.

457. The method of claim 455, wherein the compound, antibody-drug conjugate, or composition is administered after administration of the neoantigen vaccine.

458. The method of claim 455, wherein the compound, antibody-drug conjugate, or composition is administered concurrently with administration of the neoantigen vaccine.

459. The method of any one of claims 455 to 458, wherein administration of the compound, antibody-drug conjugate, or composition is repeated at least once after initial administration.

460. The method of claim 459, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced as compared to the amount used for initial administration.

461. The method of any one of claims 455 to 460, wherein the neoantigen vaccine comprises at least one neoantigen peptide.

462. The method of claim 461 , wherein the at least one neoantigen peptide ranges from about 10 to about 35 amino acids in length.

463. The method of claim 461 or claim 462, wherein the at least one neoantigen peptide ranges from about 15 to about 25 amino acids in length.

464. The method of any one of claims 461 to 463, wherein the at least one neoantigen peptide comprises one or more than one neoantigen sequence.

465. The method of claim 464, wherein the neoantigen sequence is a neoantigen sequence specific to the subject.

466. The method of claim 464, wherein the neoantigen sequence is a universal neoantigen sequence.

467. The method of claim 465, wherein the neoantigen sequence is a personalized neoantigen vaccine for the subject.

468. The method of claim 467, wherein the neoantigen sequence has been identified by sequencing at least one neoantigen induced in the subject by administering an effective amount of the compound, antibody-drug conjugate, or composition.

469. The method of claim 467 or claim 468, wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in the subject.

470. The method of claim 466, wherein the neoantigen sequence is a universal neoantigen vaccine.

471. The method of claim 470, wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, or at least 45% of subjects in a population of subjects suffering from the neoplastic disorder.

472. The method of claim 470 or claim 471 , wherein the neoantigen sequence is capable of eliciting a T-cell response against a tumor present in at least 1%, at least 5%, or at least 10% of a population of subjects suffering from the neoplastic disorder.

473. The method of any one of claims 464 to 472, wherein the at least one neoantigen peptide comprises a neoantigen sequence induced by contacting a neoplastic cell with an effective amount of the compound, antibody-drug conjugate, or composition.

474. The method of claim 455, wherein the neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable carrier.

475. The method of claim 474, wherein the at least one neoantigen peptide is linked to the pharmaceutically acceptable carrier.

476. The method of claim 474 or claim 475, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

477. The method of any one of claims 474 to 476, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are covalently attached via a linker.

478. The method of any one of claims 474 to 476, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are expressed as a fusion protein.

479. The method of claim 455, wherein the neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable diluent.

480. The method of claim 455, wherein the neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable adjuvant.

481. The method of claim 473, wherein the neoplastic cell is present in an in vitro cell culture.

482. The method of claim 473 or claim 481 , wherein the neoplastic cell is obtained from the subject.

483. The method of claim 473, wherein the neoplastic cell is present in the subject.

484. The method of any one of claims 455 to 460, wherein the neoantigen vaccine comprises at least one neoantigen mRNA.

485. The method of claim 484, wherein the at least one neoantigen mRNA encodes one or more than one neoantigen sequence.

486. The method of claim 485, wherein the neoantigen sequence is a neoantigen sequence specific to the subject.

487. The method of claim 485, wherein the neoantigen sequence is a universal neoantigen sequence.

488. The method of claim 486, wherein the neoantigen sequence is a personalized neoantigen vaccine for the subject.

489. The method of claim 488, wherein the neoantigen sequence has been identified by sequencing at least one neoantigen induced in the subject by administering an effective amount of the compound, antibody-drug conjugate, or composition.

490. The method of claim 488 or claim 489, wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in the subject.

491. The method of claim 487, wherein the neoantigen sequence is a universal neoantigen vaccine.

492. The method of claim 491 , wherein the neoantigen sequence is capable of binding to at least one HLA allele expressed in at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, or at least 45% of subjects in a population of subjects suffering from the neoplastic disorder.

493. The method of claim 491 or claim 492, wherein the neoantigen sequence is capable of eliciting a T-cell response against a tumor present in at least 1%, at least 5%, or at least 10% of a population of subjects suffering from the neoplastic disorder.

494. The method of any one of claims 484 to 493, wherein the at least one neoantigen mRNA encodes a neoantigen sequence induced by contacting a neoplastic cell with an effective amount of the compound, antibody-drug conjugate, or composition.

495. The method of claim 484, wherein the neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable carrier.

496. The method of claim 495, wherein the at least one neoantigen mRNA is linked to the pharmaceutically acceptable carrier.

497. The method of claim 495 or claim 496, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

498. The method of claim 484, wherein the neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable diluent.

499. The method of claim 484, wherein the neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable adjuvant.

500. The method of any one of claims 484 to 499, wherein the neoantigen mRNA is encapsulated by an encapsulating agent.

501. The method of claim 500, wherein the encapsulating agent is a liposome.

502. The method of claim 500, wherein the encapsulating agent is a nanoparticle.

503. The method of claim 494, wherein the neoplastic cell is present in an in vitro cell culture.

504. The method of claim 494 or claim 503, wherein the neoplastic cell is obtained from the subject.

505. The method of claim 494, wherein the neoplastic cell is present in the subject.

506. The method of any one of claims 417 to 435, wherein the at least one additional therapy comprises administering a cytokine or cytokine analog.

507. The method of claim 506, wherein the subject is intolerant, non-responsive, or poorly responsive to the cytokine or cytokine analog when administered alone.

508. The method of claim 506 or claim 507, wherein the cytokine or cytokine analog comprises a T-cell enhancer.

509. The method of any one of claims 506 to 508, wherein the cytokine or cytokine analog comprises IL-2, IL-10, IL-12, IL-15, IFNy, and / or TNFa.

510. The method of any one of claims 417 to 435, wherein the at least one additional therapy comprises administering engineered tumor-targeting T-cells.

511. The method of any one of claims 417 to 510, wherein the subject has a non- synonymous mutational burden of about 150 mutations or less.

512. The method of any one of claims 417 to 511 , wherein the subject has a non- synonymous mutational burden of about 100 mutations or less.

513. The method of any one of claims 417 ot 512, wherein the subject has a non- synonymous mutational burden of about 50 mutations or less.

514. The method of any one of claims 417 to 513, wherein the neoplastic disorder is a hematological malignancy or a solid tumor.

515. The method of claim 514, wherein the hematological malignancy is selected from a 13- cell malignancy, a leukemia, a lymphoma, and a myeloma.

516. The method of claim 514 or claim 515, wherein the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma.

517. The method of claim 514, wherein the solid tumor is selected from breast cancer, gastric cancer, prostate cancer, ovarian cancer, lung cancer, uterine cancer, salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer.

518. A method of identifying at least one neoantigen, comprising:(a) contacting a neoplastic cell with an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224;(b) detecting at least one alternatively-spliced mRNA transcript after contacting the neoplastic cell with the compound, antibody-drug conjugate, or composition;(c) predicting translation of the at least one alternatively-spliced mRNA transcript into at least one peptide; and(d) comparing the at least one peptide to a reference proteome, wherein at least one neoantigen is identified if the at least one peptide does not match any peptides in the reference proteome.

519. The method of claim 518, wherein detecting at least one alternatively-spliced mRNA transcript comprises RNAseq.

520. The method of claim 518 or claim 519, wherein predicting translation of the at least one alternatively-spliced mRNA transcript comprises quantifying the change in percent spliced in (dPSI) value for the at least one transcript.

521. The method of any one of claims 518 to 520, wherein predicting translation of the at least one alternatively-spliced mRNA transcript comprises RiboSeq and / or ribosomal profiling.

522. The method of any one of claims 518 to 521 , wherein the method further comprises evaluating the at least one peptide for predicted major histocompatibility complex (MHC) binding.

523. The method of claim 522, wherein predicted MHC binding is determined by measuring raw affinity predicted binding strength of the at least one peptide.

524. The method of claim 523, wherein a raw affinity predicted binding strength of about 500 nM or higher indicates MHC binding.

525. The method of any one of claims 522 to 524, wherein predicted MHC binding is determined by identifying a distribution of predicted binding strengths for a series of random peptides; and comparing predicted binding strength of the at least one peptide to the distribution.

526. The method of claim 525, wherein a predicted binding strength in the top 2% of the distribution indicates weak MHC binding.

527. The method of claim 525, wherein a predicted binding strength in the top 0.5% of the distribution indicates strong MHC binding.

528. The method of any one of claims 518 to 527, wherein the neoplastic cell is present in an in vitro cell culture.

529. The method of claim 528, wherein the neoplastic cell is obtained from the subject.

530. The method of any one of claims 518 to 527, wherein the neoplastic cell is present in the subject.

531. The method of any one of claims 518 to 530, further comprising contacting one or more additional neoplastic cells to identify at least one universal neoantigen.

532. A method of identifying at least one neoantigen, comprising:(a) contacting a neoplastic cell with an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224;(b) detecting at least one peptide comprising a potential neoantigen sequence after contacting the neoplastic cell with the compound, antibody-drug conjugate, or composition; and(c) comparing the at least one peptide to a reference proteome, wherein at least one neoantigen is identified if the at least one peptide does not match any peptides in the reference proteome.

533. The method of claim 532, wherein the method further comprises evaluating the at least one peptide for predicted major histocompatibility complex (MHC) binding.

534. The method of claim 533, wherein predicted MHC binding is determined by measuring raw affinity predicted binding strength of the at least one peptide.

535. The method of claim 534, wherein a raw affinity predicted binding strength of about 500 nM or higher indicates MHC binding.

536. The method of any one of claims 533 to 535, wherein predicted MHC binding is determined by identifying a distribution of predicted binding strengths for a series of random peptides; and comparing predicted binding strength of the at least one peptide to the distribution.

537. The method of claim 536, wherein a predicted binding strength in the top 2% of the distribution indicates weak MHC binding.

538. The method of claim 536, wherein a predicted binding strength in the top 0.5% of the distribution indicates strong MHC binding.

539. The method of any one of claims 532 to 538, wherein the neoplastic cell is present in an in vitro cell culture.

540. The method of claim 539, wherein the neoplastic cell is obtained from the subject.

541. The method of any one of claims 532 to 538, wherein the neoplastic cell is present in the subject.

542. The method of any one of claims 532 to 541 , further comprising contacting one or more additional neoplastic cells to identify at least one universal neoantigen.

543. A method of making a neoantigen vaccine, comprising:(a) identifying at least one neoantigen using the method of any one of claims 518 to 542; and(b) formulating the at least one neoantigen together with a pharmaceutically acceptable carrier, diluent, or adjuvant.

544. The method of claim 543, wherein the at least one neoantigen is linked to the pharmaceutically acceptable carrier.

545. The method of claim 544, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

546. A method of treating a subject having or suspected of having a neoplastic disorder, comprising:(a) administering to the subject an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or thecomposition of any one of claims 220 to 224;(b) detecting one or more neoantigens in the subject after administration of the compound, antibody-drug conjugate, or composition;(c) comparing the one or more neoantigens to a panel of universal neoantigens; and(d) administering to the subject a universal neoantigen vaccine comprising at least one universal neoantigen present in the subject.

547. The method of claim 546, wherein the universal neoantigen vaccine is administered alone or in combination with at least one additional therapy.

548. The method of claim 547, wherein the at least one additional therapy comprises at least one, at least two, at least three, at least four, or at least five additional therapies.

549. The method of claim 547 or claim 548, wherein the at least one additional therapy comprises repeated administration of the compound, antibody-drug conjugate, or composition.

550. The method of claim 549, wherein repeated administration of the compound, antibody- drug conjugate, or composition is initiated before administration of the universal neoantigen vaccine.

551. The method of claim 549, wherein repeated of the compound, antibody-drug conjugate, or composition is initiated after administration of the universal neoantigen vaccine.

552. The method of claim 549, wherein repeated administration of the compound, antibody- drug conjugate, or composition is initiated concurrently with administration of the universal neoantigen vaccine.

553. The method of any one of claims 549 to 552, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced as compared to the amount used for initial administration.

554. The method of any one of claims 549 to 553, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

555. The method of any one of claims 549 to 554, wherein the amount of the compound, antibody-drug conjugate, or composition used for repeated administration is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the compound, antibody-drug conjugate, or composition.

556. The method of any one of claims 547 to 555, wherein the at least one additional therapy comprises administering a checkpoint inhibitor.

557. The method of claim 556, wherein administration of the checkpoint inhibitor is initiated before administration of the universal neoantigen vaccine and / or repeated administration of the compound, antibody-drug conjugate, or composition.

558. The method of claim 556, wherein administration of the checkpoint inhibitor is initiated after administration of the universal neoantigen vaccine and / or repeated of the compound, antibody-drug conjugate, or composition.

559. The method of claim 556, wherein administration of the checkpoint inhibitor is initiated concurrently with administration of the universal neoantigen vaccine and / or repeatedadministration of the compound, antibody-drug conjugate, or composition.

560. The method of any one of claims 556 to 559, wherein administration of the checkpoint inhibitor is repeated at least once after initial administration.

561. The method of claim 560, wherein the amount of the checkpoint inhibitor used for repeated administration is reduced as compared to the amount used for initial administration.

562. The method of claim 560 or claim 561 , wherein the amount of the checkpoint inhibitor used for repeated administration is reduced as compared to a standard dosage of the checkpoint inhibitor.

563. The method of any one of claims 560 to 562, wherein the amount of the checkpoint inhibitor used for repeated administration is reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 75%, or 90%, as compared to a standard dosage of the checkpoint inhibitor.

564. The method of any one of claims 556 to 563, wherein the subject is intolerant, non- responsive, or poorly responsive to the checkpoint inhibitor when administered alone.

565. The method of any one of claims 556 to 564, wherein the checkpoint inhibitor targets CTLA4, PD1 , PDL1 , 0X40, CD40, GITR, LAG3, TIM3, and / or KIR.

566. The method of any one of claims 556 to 565, wherein the checkpoint inhibitor targets CTLA4, 0X40, CD40, and / or GITR.

567. The method of any one of claims 556 to 566, wherein the checkpoint inhibitor comprises a cytotoxic T-lymphocyte-associated antigen 4 pathway (CTLA4) inhibitor.

568. The method of claim 567, wherein the CTLA4 inhibitor is an anti-CTLA4 antibody.

569. The method of claim 568, wherein the anti-CTLA4 antibody is ipilimumab.

570. The method of any one of claims 556 to 566, wherein the checkpoint inhibitor comprises a programmed death-1 pathway (PD1) inhibitor.

571. The method of claim 570, wherein the PD1 inhibitor is an anti-PD1 antibody.

572. The method of claim 571 , wherein the anti-PD1 antibody is nivolumab.

573. The method of claim 570, wherein the PD1 inhibitor is an anti-PDL1 antibody.

574. The method of claim 573, wherein the anti-PDL1 antibody is atezolizumab.

575. The method of any one of claims 556 to 566, wherein the checkpoint inhibitor comprises a CTLA4 inhibitor and a PD1 inhibitor.

576. The method of claim 575, wherein the CTLA4 inhibitor is an anti-CTLA4 antibody.

577. The method of claim 576, wherein the anti-CTLA4 antibody is ipilimumab.

578. The method of claim 575, wherein the PD1 inhibitor is an anti-PD1 antibody.

579. The method of claim 578, wherein the anti-PD1 antibody is nivolumab.

580. The method of claim 575, wherein the PD1 inhibitor is an anti-PDL1 antibody.

581. The method of claim 580, wherein the anti-PDL1 antibody is atezolizumab.

582. The method of any one of claims 546 to 581 , wherein the universal neoantigen vaccine comprises at least one neoantigen peptide.

583. The method of claim 582, wherein the at least one neoantigen peptide ranges from about 10 to about 35 amino acids in length.

584. The method of claim 582 or claim 583, wherein the at least one neoantigen peptide ranges from about 15 to about 25 amino acids in length.

585. The method of any one of claims 582 to 584, wherein the at least one neoantigen peptide comprises one or more than one universal neoantigen sequence.

586. The method of claim 585, wherein the universal neoantigen sequence is capable of binding to at least one HLA allele expressed in at least 10%, at least 15%, at least 20%, at least25%, at least 30%, at least 35%, at least 40%, or at least 45% of subjects in a population of subjects suffering from the neoplastic disorder.

587. The method of claim 585 or claim 586, wherein the universal neoantigen sequence is capable of eliciting a T-cell response against a tumor present in at least 1%, at least 5%, or at least 10% of a population of subjects suffering from the neoplastic disorder.

588. The method of claim 582, wherein the universal neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable carrier.

589. The method of claim 588, wherein the at least one neoantigen peptide is linked to the pharmaceutically acceptable carrier.

590. The method of claim 588 or claim 589, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

591. The method of any one of claims 588 to 590, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are covalently attached via a linker.

592. The method of any one of claims 588 to 590, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are expressed as a fusion protein.

593. The method of claim 582, wherein the universal neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable diluent.

594. The method of claim 582, wherein the universal neoantigen vaccine comprises at least one neoantigen peptide and a pharmaceutically acceptable adjuvant.

595. The method of any one of claims 546 to 581 , wherein the universal neoantigen vaccine comprises at least one neoantigen mRNA.

596. The method of claim 595, wherein the at least one neoantigen mRNA encodes one or more than one universal neoantigen sequence.

597. The method of claim 596, wherein the universal neoantigen sequence is capable of binding to at least one HLA allele expressed in at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, or at least 45% of subjects in a population of subjects suffering from the neoplastic disorder.

598. The method of claim 596 or claim 597, wherein the universal neoantigen sequence is capable of eliciting a T-cell response against a tumor present in at least 1%, at least 5%, or at least 10% of a population of subjects suffering from the neoplastic disorder.

599. The method of claim 595, wherein the universal neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable carrier.

600. The method of claim 599, wherein the at least one neoantigen mRNA is linked to the pharmaceutically acceptable carrier.

601. The method of claim 599 or claim 600, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

602. The method of claim 595, wherein the universal neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable diluent.

603. The method of claim 595, wherein the universal neoantigen vaccine comprises at least one neoantigen mRNA and a pharmaceutically acceptable adjuvant.

604. The method of any one of claims 595 to 603, wherein the neoantigen mRNA is encapsulated by an encapsulating agent.

605. The method of claim 604, wherein the encapsulating agent is a liposome.

606. The method of claim 604, wherein the encapsulating agent is a nanoparticle.

607. The method of any one of claims 546 to 606, wherein the subject has a non- synonymous mutational burden of about 150 mutations or less.

608. The method of any one of claims 546 to 607, wherein the subject has a non- synonymous mutational burden of about 100 mutations or less.

609. The method of any one of claims 546 to 608, wherein the subject has a non- synonymous mutational burden of about 50 mutations or less.

610. The method of any one of claims 546 to 609, wherein the neoplastic disorder is a hematological malignancy or a solid tumor.

611. The method of claim 610, wherein the hematological malignancy is selected from a 13- cell malignancy, a leukemia, a lymphoma, and a myeloma.

612. The method of claim 610 or claim 611 , wherein the hematological malignancy is selected from acute myeloid leukemia and multiple myeloma.

613. The method of claim 610, wherein the solid tumor is selected from breast cancer, gastric cancer, prostate cancer, ovarian cancer, lung cancer, uterine cancer, salivary duct carcinoma, melanoma, colon cancer, cervical cancer, pancreatic cancer, kidney cancer, colorectal cancer, and esophageal cancer.

614. A neoantigen vaccine comprising at least one neoantigen peptide, wherein the at least one neoantigen peptide comprises a neoantigen sequence induced by contacting a neoplastic cell with an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224.

615. The neoantigen vaccine of claim 614, wherein the at least one neoantigen peptide ranges from about 10 to about 35 amino acids in length.

616. The neoantigen vaccine of claim 614 or claim 615, wherein the at least one neoantigen peptide ranges from about 15 to about 25 amino acids in length.

617. The neoantigen vaccine of any one of claims 614 to 616, further comprising a pharmaceutically acceptable carrier.

618. The neoantigen vaccine of claim 617, wherein the at least one neoantigen peptide is linked to the pharmaceutically acceptable carrier.

619. The neoantigen vaccine of claim 617 or claim 618, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

620. The neoantigen vaccine of any one of claims 617 to 619, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are covalently attached via a linker.

621. The neoantigen vaccine of any one of claims 617 to 619, wherein the neoantigen peptide and the pharmaceutically acceptable carrier are expressed as a fusion protein.

622. The neoantigen vaccine of any one of claims 614 to 616, further comprising a pharmaceutically acceptable diluent.

623. The neoantigen vaccine of any one of claims 614 to 616, further comprising a pharmaceutically acceptable adjuvant.

624. The neoantigen vaccine of any one of claims 614 to 623, wherein the neoplastic cell is present in an in vitro cell culture.

625. The neoantigen vaccine of any one of claims 614 to 624, wherein the neoplastic cell is obtained from a subject.

626. The neoantigen vaccine of any one of claims 614 to 623, wherein the neoplastic cell is present in a subject.

627. A neoantigen vaccine comprising at least one neoantigen mRNA, wherein the at least one neoantigen RNA encodes a neoantigen sequence induced by contacting a neoplastic cell with an effective amount of the antibody-drug conjugate of any one of claims 1 to 189, the compound of any one of claims 190 to 219, or the composition of any one of claims 220 to 224.

628. The neoantigen vaccine of claim 627, further comprising a pharmaceutically acceptable carrier.

629. The neoantigen vaccine of claim 628, wherein the at least one neoantigen mRNA is linked to the pharmaceutically acceptable carrier.

630. The neoantigen vaccine of claim 628 or claim 629, wherein the pharmaceutically acceptable carrier is selected from a peptide, a serum albumin, a keyhole limpet hemocyanin, an immunoglobulin, a thyroglobulin, an ovalbumin, a toxoid or an attenuated toxoid derivative, a cytokine, and a chemokine.

631. The neoantigen vaccine of claim 627, further comprising a pharmaceutically acceptable diluent.

632. The neoantigen vaccine of claim 627, further comprising a pharmaceutically acceptable adjuvant.

633. The neoantigen vaccine of any one of claims 627 to 632, wherein the neoantigen mRNA is encapsulated by an encapsulating agent.

634. The neoantigen vaccine of claim 633, wherein the encapsulating agent is a liposome.

635. The neoantigen vaccine of claim 633, wherein the encapsulating agent is a nanoparticle.

636. The neoantigen vaccine of any one of claims 627 to 635, wherein the neoplastic cell is present in an in vitro cell culture.

637. The neoantigen vaccine of any one of claims 627 to 636, wherein the neoplastic cell is obtained from a subject.

638. The neoantigen vaccine of any one of claims 627 to 635, wherein the neoplastic cell is present in a subject.

639. A method of treating a subject having or suspected of having a neoplastic disorder, comprising administering to the subject a therapeutically effective amount of the compound of any one of claims 190 to 219 or the pharmaceutical composition of claim 220.

640. A method of reducing or inhibiting growth of a tumor in a subject having or suspected of having a neoplastic disorder, comprising administering to the subject a therapeutically effective amount of the compound of any one of claims 190 to 219 or the pharmaceutical composition of claim 220.

641. A compound chosen from:ally acceptable salts thereof,wherein L is a linker which covalently attaches to an antibody.

642. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

643. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

644. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

645. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

646. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

647. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

648. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

649. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

650. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

651. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

652. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

653. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

654. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

655. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

656. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

657. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

658. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

659. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

660. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

661. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

662. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

663. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

664. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

665. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

666. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

667. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

668. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

669. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

670. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

671. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

672. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

673. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

674. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

675. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

676. A compound of claim 641 , wherein the compound ispharmaceutically acceptable salt thereof.

677. A compound of claim 641 , wherein the compound is, or a pharmaceutically acceptable salt thereof.

678. A compound of claim 641 , wherein the compound is679. The compound of any one of claims 641 to 678, wherein the linker is a cleavable linker.

680. The compound of claim 679, wherein the linker comprises a cleavable peptide moiety.

681. The compound of claim 680, wherein the cleavable peptide moiety is cleavable by an enzyme.

682. The compound of any one of claims 679 to 681 , wherein the cleavable peptide moiety or linker comprises an amino acid unit.

683. The compound of claim 682, wherein the amino acid unit comprises valine-citrulline (Val- Cit).

684. The compound of claim 682, wherein the amino acid unit comprises valine-alanine (Val- Ala).

685. The compound of claim 682, wherein the amino acid unit comprises glutamine-valine- citrulline (Glu-Val-Cit).

686. The compound of claim 682, wherein the amino acid unit comprises alanine-alanine- asparagine (Ala-Ala- Asn).

687. The compound of claim 679, wherein the linker comprises a cleavable glucuronide moiety.

688. The compound of claim 687, wherein the cleavable glucuronide moiety is cleavable by an enzyme.

689. The compound of claim 687 or claim 688, wherein the cleavable glucuronide moiety is cleavable by a glucuronidase.

690. The compound of any one of claims 687 to 689, wherein the cleavable glucuronide moiety is cleavable by b-glucuronidase.

691. The compound of any one of claims 641 to 690, wherein the linker comprises at least one spacer unit.

692. The compound of claim 691 , wherein the spacer unit or linker comprises a polyethylene glycol (PEG) moiety.

693. The compound of claim 692, wherein the PEG moiety comprises -(PEG)m- and m is an integer from 1 to 10.

694. The compound of claim 693, wherein m is 2.

695. The compound of claim 693, wherein the spacer unit or linker comprises an alkyl moiety.

696. The compound of claim 695, wherein the alkyl moiety comprises-(CHzV and n is an integer from 1 to 10.

697. The compound of claim 696, wherein n is 2.

698. The compound of claim 696, wherein n is 5.

699. The compound of claim 696, wherein n is 6.

700. The compound of any one of claims 691 to 699, wherein the spacer unit attaches to the antibody or antigen binding fragment via a maleimide (Mai) moiety (“Mal-spacer unit”).

701. The compound of claim 700, wherein the Mal-spacer unit is reactive with a cysteine residue on the antibody or antigen binding fragment.

702. The compound of claim 700 or claim 701 , wherein the Mal-spacer unit is joined to the antibody or antigen binding fragment via a cysteine residue on the antibody or antigen binding fragment.

703. The compound of any one of claims 700 to 702, wherein the linker comprises the Mal- spacer unit and a cleavable peptide moiety.

704. The compound of claim 703, wherein the cleavable peptide moiety comprises an amino acid unit.

705. The compound of claim 703 or claim 704, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit.

706. The compound of claim 703 or claim 704, wherein the cleavable peptide moiety or amino acid unit comprises Val-Ala.

707. The compound of claim 703 or claim 704, wherein the cleavable peptide moiety or amino acid unit comprises Glu-Val-Cit.

708. The compound of claim 703 or claim 704, wherein the cleavable peptide moiety or amino acid unit comprises Ala-Ala-Asn.

709. The compound of any one of claims 700 to 708, wherein the Mal-spacer unit comprises an alkyl moiety.

710. The compound of any one of claims 700 to 708, wherein the Mal-spacer unit comprises a PEG moiety.

711. The compound of any one of claims 700 to 710, wherein the Mal-spacer unit comprises a maleimidocaproyl (MC).

712. The compound of any one of claims 700 to 711 , wherein the Mal-spacer unit attaches the antibody or antigen binding fragment to the cleavable moiety in the linker.

713. The compound of claim 712, wherein the cleavable moiety in the linker comprises a cleavable peptide moiety.

714. The compound of claim 713, wherein the cleavable peptide moiety comprises an amino acid unit.

715. The compound of claim 713 or claim 714, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn.

716. The compound of any one of claims 712 to 715, wherein the linker comprises MC-Val- Cit.

717. The compound of any one of claims 712 to 715, wherein the linker comprises MC-Val- Ala.

718. The compound of any one of claims 712 to 715, wherein the linker comprises MC-Glu- Val-Cit.

719. The compound of any one of claims 712 to 715, wherein the linker comprises MC-Ala- Ala-Asn.

720. The compound of any one of claims 712 to 719, wherein the Mal-spacer unit comprises an alkyl moiety.

721. The compound of any one of claims 7125 to 719, wherein the Mal-spacer unit comprises a PEG moiety.

722. The compound of any one of claims 712 to 721 , wherein the Mal-spacer unit comprises a maleimidocaproyl (MC).

723. The compound of any one of claims 691 to 722, wherein the cleavable moiety in the linker is directly joined to the splicing modulator, or wherein a spacer unit attaches the cleavable moiety in the linker to the splicing modulator.

724. The compound of claim 723, wherein cleavage of the conjugate releases the splicing modulator from the antibody or antigen binding fragment and linker.

725. The compound of claim 723 or claim 724, wherein the spacer unit attaching the cleavable moiety in the linker to the splicing modulator is self-immolative.

726. The compound of any one of claims 723 to 725, wherein the spacer unit attaching the cleavable moiety in the linker to the splicing modulator comprises a p-aminobenzyloxycarbonyl (pABC).

727. The compound of claim 726, wherein the pABC attaches the cleavable moiety in the linker to the splicing modulator.

728. The compound of claim 726 or claim 727, wherein the cleavable moiety in the linker comprises a cleavable peptide moiety.

729. The compound of claim 728, wherein the cleavable peptide moiety comprises an amino acid unit.

730. The compound of claim 728 or claim 729, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn.

731. The compound of any one of claims 726 to 730, wherein the linker comprises Val-Cit- pABC.

732. The compound of any one of claims 726 to 730, wherein the linker comprises Val-Ala- pABC.

733. The compound of any one of claims 726 to 730, wherein the linker comprises Glu-Val- Cit-pABC.

734. The compound of any one of claims 726 to 730, wherein the linker comprises Ala-Ala- Asn-pABC.

735. The compound of any one of claims 723 to 725, wherein the spacer unit attaching the cleavable moiety in the linker to the splicing modulator comprises a p-aminobenzyl (pAB).

736. The compound of claim 735, wherein the pAB attaches the cleavable moiety in the linker to the splicing modulator.

737. The compound of claim 735 or claim 736, wherein the cleavable moiety in the linker comprises a cleavable peptide moiety.

738. The compound of claim 737, wherein the cleavable peptide moiety comprises an amino acid unit.

739. The compound of claim 737 or claim 738, wherein the cleavable peptide moiety or amino acid unit comprises Val-Cit, Val-Ala, Glu-Val-Cit, or Ala-Ala-Asn.

740. The compound of any one of claims 735 to 739, wherein the linker comprises Val-Cit- pAB.

741. The compound of any one of claims 735 to 739, wherein the linker comprises Val-Ala- pAB.

742. The compound of any one of claims 735 to 739, wherein the linker comprises Glu-Val- Cit-pAB.

743. The compound of any one of claims 735 to 739, wherein the linker comprises Ala-Ala- Asn-pAB.

744. The compound of any one of claims 641 to 678, wherein the linker is a non-cleavable linker.

745. The compound of claim 744, wherein the linker comprises at least one spacer unit.

746. The compound of claim 744 or claim 745, wherein the spacer unit or linker comprises a polyethylene glycol (PEG) moiety.

747. The compound of claim 746, wherein the PEG moiety comprises -(PEG)m- and m is an integer from 1 to 10.

748. The compound of claim 747, wherein m is 2.

749. The compound of claim 744 or claim 745, wherein the spacer unit or linker comprises an alkyl moiety.

750. The compound of claim 749, wherein the alkyl moiety comprises-(CHz and n is an integer from 1 to 10.

751. A method of producing an antibody-drug conjugate, comprising reacting an antibody or antigen binding fragment with the compound of any one of claims 641 to 750 under conditions that allow conjugation.

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