Antibody drug conjugates and uses thereof

Abstract

Provided herein are Drug-Linkers and Antibody-Drug Conjugates comprising a Trichothecene for the use of treating diseases, disorders, or conditions.

Description

ANTIBODY DRUG CONJUGATES AND USES THEREOF CROSS-REFERENCE [1] This application claims the benefit of: U.S. Provisional Patent Application No.63 / 637,497 filed on April 23, 2024; and U.S. Provisional Patent Application No.63 / 735,245 filed on December 17, 2024; the entire contents of each of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [2] Antibody-drug conjugates (ADCs) are a class of drugs designed as a targeted therapy for treating disease. There is a need for ADC drugs with better efficacy and / or safety. In particular, there is a need for novel classes of payloads that can address emerging resistance to standard of care mechanisms of action (e.g., camptothecins and tubulin binders). Herein, we describe the first application of certain trithothecenes type molecules to antibody drug conjugates. SUMMARY OF THE INVENTION [3] In an aspect, the present disclosure provides a Drug-Linker of Formula I:(Formula I), or a pharmaceutically acceptable salt thereof, wherein: each Y is independently a Spacer unit; y is selected from 0, 1, and 2; D is a Drug unit; each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1. [4] In an aspect, the present disclosure provides a Drug-Linker of Formula I-RA-a:or a pharmaceutically acceptable salt thereof.[5] In an aspect, the present disclosure provides a Drug-Linker of Formula I-RA-b:or a pharmaceutically acceptable salt thereof.[6] In an aspect, the present disclosure provides a Drug-Linker of Formula I-RE:or a pharmaceutically acceptable salt thereof.[7] In an aspect, the present disclosure provides a Conjugate of Formula Ila:or a pharmaceutically acceptable salt thereof, wherein:Ab is an antibody or an antigen-binding portion thereof; each Y is independently a Spacer unit;y is selected from 0, 1, and 2; each D is a Drug unit; p is an integer from 1 to 20; each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1.[8] In some embodiments, for a Conjugate of Formula Ila, Ab is an antibody; each Y is independently a Spacer unit; y is selected from 0, 1, and 2; each D is a Drug unit; p is an integer from 1 to 20; each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1.[9] In an aspect, the present disclosure provides a Conjugate of Formula II-RA-a:or a pharmaceutically acceptable salt thereof.

[0010] In an aspect, the present disclosure provides a Conjugate of Formula II-RA-b:or a pharmaceutically acceptable salt thereof.

[0011] In an aspect, the present disclosure provides a Conjugate of Formula II-RE:, or a pharmaceutically acceptable salt thereof.

[0012] In an aspect, the present disclosure provides a compound or salt of Formula III-a:or a pharmaceutically acceptable salt thereof, wherein: E1is selected from hydrogen and an End unit; X1is absent or selected from -N(R1)-, -O-, and heterocycle; R1is selected from hydrogen and C1-6alkyl; and P is selected fromR2is selected from hydrogen and -OR10; R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, - S(O)2R20, -P(O)(OR20)2, -Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, - N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0013] In certain embodiments, the disclosure provides a pharmaceutical composition comprising a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I- RE, a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, or a compound or salt of Formula IIIa, and a pharmaceutically acceptable excipient.

[0014] In certain embodiments, the disclosure provides a method of treating a disease or disorder, comprising administering to a subject in need thereof a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, or a compound or salt of Formula IIIa, or a pharmaceutical composition comprising a Drug-Linker or salt Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, or a compound or salt of Formula IIIa, and a pharmaceutically acceptable excipient. In some cases, the disease, disorder, or condition is cancer.

[0015] In certain embodiments, the disclosure provides a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, for use in a method of treating orpreventing a disease, disorder, or condition. In some cases, the disease, disorder, or condition is cancer. INCORPORATION BY REFERENCE

[0016] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. To the extent publications and patents or patent applications incorporated by reference contradict the disclosure contained in the specification, the specification is intended to supersede and / or take precedence over any such contradictory material. DETAILED DESCRIPTION OF THE INVENTION

[0017] While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby. Definitions

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs. All patents and publications referred to herein are incorporated by reference.

[0019] As used in the specification and claims, the singular form “a”, “an” and “the” includes plural references unless the context clearly dictates otherwise.

[0020] The term “Cx-y” when used in conjunction with a chemical moiety, such as alkyl, alkenyl, or alkynyl is meant to include groups that contain from x to y carbons in the chain. For example, the term “C1-6alkyl” refers to saturated hydrocarbon groups, including straight-chain alkyl and branched-chain alkyl groups that contain from 1 to 6 carbons. The term –Cx-yalkylene- refers to a substituted or unsubstituted alkylene chain with from x to y carbons in the alkylene chain. For example –C1-6alkylene- may be selected from methylene, ethylene, propylene, butylene, pentylene, and hexylene, any one of which is optionally substituted.

[0021] “Alkyl” as used herein refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, containing no unsaturation, and preferablyhaving from one to fifteen carbon atoms (i.e., C1-C15alkyl). In certain embodiments, an alkyl comprises one to thirteen carbon atoms (i.e., C1-C13alkyl). In certain embodiments, an alkyl comprises one to eight carbon atoms (i.e., C1-C8alkyl). In other embodiments, an alkyl comprises one to five carbon atoms (i.e., C1-C5alkyl). In other embodiments, an alkyl comprises one to four carbon atoms (i.e., C1-C4alkyl). In other embodiments, an alkyl comprises one to three carbon atoms (i.e., C1-C3alkyl). In other embodiments, an alkyl comprises one to two carbon atoms (i.e., C1-C2alkyl). In other embodiments, an alkyl comprises one carbon atom (i.e., C1alkyl). In other embodiments, an alkyl comprises five to fifteen carbon atoms (i.e., C5-C15alkyl). In other embodiments, an alkyl comprises five to eight carbon atoms (i.e., C5-C8alkyl). In other embodiments, an alkyl comprises two to five carbon atoms (i.e., C2-C5alkyl). In other embodiments, an alkyl comprises three to five carbon atoms (i.e., C3-C5alkyl). In certain embodiments, the alkyl group is selected from methyl, ethyl, 1-propyl (n-propyl), 1-methylethyl (iso-propyl), 1-butyl (n-butyl), 1-methylpropyl (sec-butyl), 2-methylpropyl (iso-butyl), 1,1-dimethylethyl (tert-butyl), 1-pentyl (n-pentyl). The alkyl is attached to the rest of the molecule by a single bond.

[0022] “Alkenyl” as used herein refers to a straight or branched hydrocarbon chain radical group consisting solely of carbon and hydrogen atoms, containing at least one carbon-carbon double bond, and preferably having from two to twelve carbon atoms (i.e., C2-C12alkenyl). In certain embodiments, an alkenyl comprises two to eight carbon atoms (i.e., C2-C8alkenyl). In certain embodiments, an alkenyl comprises two to six carbon atoms (i.e., C2-C6alkenyl). In other embodiments, an alkenyl comprises two to four carbon atoms (i.e., C2-C4alkenyl). The alkenyl is attached to the rest of the molecule by a single bond, for example, ethenyl (i.e., vinyl), prop-1-enyl (i.e., allyl), but-1-enyl, pent-1-enyl, penta-1,4-dienyl, and the like.

[0023] “Alkynyl” as used herein refers to a straight or branched hydrocarbon chain radical group consisting solely of carbon and hydrogen atoms, containing at least one carbon-carbon triple bond, and preferably having from two to twelve carbon atoms (i.e., C2-C12alkynyl). In certain embodiments, an alkynyl comprises two to eight carbon atoms (i.e., C2-C8alkynyl). In other embodiments, an alkynyl comprises two to six carbon atoms (i.e., C2-C6alkynyl). In other embodiments, an alkynyl comprises two to four carbon atoms (i.e., C2-C4alkynyl). The alkynyl is attached to the rest of the molecule by a single bond, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, and the like.

[0024] The terms “Cx-yalkenyl” and “Cx-yalkynyl” refer to unsaturated aliphatic groups analogous in length and possible substitution to the alkyls described above, but that contain at least one double or triple bond, respectively. The term –Cx-yalkenylene- refers to a substituted orunsubstituted alkenylene chain with from x to y carbons in the alkenylene chain. For example, – C2-6alkenylene- may be selected from ethenylene, propenylene, butenylene, pentenylene, and hexenylene, any one of which is optionally substituted. An alkenylene chain may have one double bond or more than one double bond in the alkenylene chain. The term –Cx-yalkynylene- refers to a substituted or unsubstituted alkynylene chain with from x to y carbons in the alkynylene chain. For example, –C2-6alkynylene- may be selected from ethynylene, propynylene, butynylene, pentynylene, and hexynylene, any one of which is optionally substituted. An alkynylene chain may have one triple bond or more than one triple bond in the alkynylene chain.

[0025] “Alkylene” refers to a straight divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing no unsaturation, and preferably having from one to twelve carbon atoms, for example, methylene, ethylene, propylene, butylene, and the like. The alkylene chain is attached to the rest of the molecule through a single bond and to the radical group through a single bond. The points of attachment of the alkylene chain to the rest of the molecule and to the radical group are through the terminal carbons respectively. An alkylene chain may be optionally substituted by one or more substituents such as those substituents described herein.

[0026] “Alkenylene” refers to a straight divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing at least one carbon-carbon double bond, and preferably having from two to twelve carbon atoms. The alkenylene chain is attached to the rest of the molecule through a single bond and to the radical group through a single bond. The points of attachment of the alkenylene chain to the rest of the molecule and to the radical group are through the terminal carbons respectively. An alkenylene chain may be optionally substituted by one or more substituents such as those substituents described herein.

[0027] “Alkynylene” refers to a straight divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing at least one carbon-carbon triple bond, and preferably having from two to twelve carbon atoms. The alkynylene chain is attached to the rest of the molecule through a single bond and to the radical group through a single bond. The points of attachment of the alkynylene chain to the rest of the molecule and to the radical group are through the terminal carbons respectively. An alkynylene chain may be optionally substituted by one or more substituents such as those substituents described herein.

[0028] “Halo” or “halogen” as used herein refers to halogen substituents such as bromo, chloro, fluoro and iodo substituents.

[0029] “Haloalkyl” as used herein refers to an alkyl radical, as defined above, that is substituted by one or more halogen radicals, for example, trifluoromethyl, dichloromethyl, bromomethyl, 2,2,2-trifluoroethyl, 1-fluoromethyl-2-fluoroethyl, and the like. Examples of halogen substituted alkanes (“haloalkanes”) include halomethane (e.g., chloromethane, bromomethane, fluoromethane, iodomethane), di-and trihalomethane (e.g., trichloromethane, tribromomethane, trifluoromethane, triiodomethane), 1-haloethane, 2-haloethane, 1,2-dihaloethane, and any other suitable combinations of alkanes (or substituted alkanes) and halogens. When an alkyl group is substituted with more than one halogen radicals, each halogen may be independently selected, for example 1-chloro,2-bromoethane.

[0030] “Aminoalkyl” refers to an alkyl radical, as defined above, that is substituted by one or more amine radicals, for example, propan-2-amine, butane-1,2-diamine, pentane-1,2,4-triamine and the like.

[0031] “Hydroxyalkyl” refers to an alkyl radical, as defined above, that is substituted by one or more hydroxy radicals, for example, propan-1-ol, butane-1,4-diol, pentane-1,2,4-triol, and the like.

[0032] “Alkoxyalkyl” refers to an alkyl radical, as defined above, that is substituted by one or more alkoxy radicals, for example, methoxymethane, 1,3-dimethoxybutane, 1-methoxypropane, 2-ethoxypentane, and the like.

[0033] “Cyanoalkyl” as used herein refers to an alkyl radical, as defined above, that is substituted by one or more cyano radicals, for example, acetonitrile, 2-ethyl-3- methylsuccinonitrile, butyronitrile, and the like.

[0034] The term “carbocycle” as used herein refers to a saturated, unsaturated or aromatic ring in which each atom of the ring is carbon. Carbocycle may include 3- to 10-membered monocyclic rings, 6- to 12-membered bicyclic rings, and 6- to 12-membered bridged rings. Each ring of a bicyclic carbocycle may be selected from saturated, unsaturated, and aromatic rings. In some embodiments, the carbocycle is an aryl. In some embodiments, the carbocycle is a cycloalkyl. In some embodiments, the carbocycle is a cycloalkenyl. In an exemplary embodiment, an aromatic ring, e.g., phenyl, may be fused to a saturated or unsaturated ring, e.g., cyclohexane, cyclopentane, or cyclohexene. Any combination of saturated, unsaturated and aromatic bicyclic rings, as valence permits, are included in the definition of carbocyclic. Exemplary carbocycles include cyclopentyl, cyclohexyl, cyclohexenyl, adamantyl, phenyl, indanyl, and naphthyl. Bicyclic carbocycles may be fused, bridged or spiro-ring systems. A carbocycle may be optionally substituted by one or more substituents such as those substituents described herein.

[0035] The term “unsaturated carbocycle” refers to carbocycles with at least one degree of unsaturation and excluding aromatic carbocycles. Examples of unsaturated carbocycles include cyclohexadiene, cyclohexene, and cyclopentene.

[0036] The term “cycloalkyl” as used herein refers to a saturated carbocycle. Exemplary cycloalkyl rings include cyclopropyl, cyclohexyl, and norbornane. Carbocycles may be optionally substituted by one or more substituents such as those substituents described herein.

[0037] The term “Cx-ycarbocycle” is meant to include groups that contain from x to y carbons in the cycle. For example, the term “C3-6carbocycle” refers to a saturated, unsaturated, or aromatic ring comprising from 3 to 6 carbons. For example –C3-6carbocycle- may be selected from cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and phenyl, any one of which is optionally substituted.

[0038] “Aryl” as used herein refers to a radical derived from an aromatic monocyclic or aromatic multicyclic hydrocarbon ring system by removing a hydrogen atom from a ring carbon atom. The aromatic monocyclic or aromatic multicyclic hydrocarbon ring system contains only hydrogen and carbon and from five to eighteen carbon atoms, where at least one of the rings in the ring system is aromatic, i.e., it contains a cyclic, delocalized (4n+2) π–electron system in accordance with the Hückel theory. The ring system from which aryl groups are derived include, but are not limited to, groups such as benzene, fluorene, indane, indene, tetralin and naphthalene.

[0039] The term “heterocycle” as used herein refers to a saturated, unsaturated or aromatic ring comprising one or more heteroatoms. Exemplary heteroatoms include N, O, Si, P, B, and S atoms. The heterocycle may be attached to the rest of the molecule through any atom of the heterocycle, valence permitting, such as a carbon or nitrogen atom of the heterocycle. Heterocycles include 3- to 10-membered monocyclic rings, 6- to 12-membered bicyclic rings, and 6- to 12-membered bridged rings. A bicyclic heterocycle includes any combination of saturated, unsaturated and aromatic bicyclic rings, as valence permits. In an exemplary embodiment, an aromatic ring, e.g., pyridyl, may be fused to a saturated or unsaturated ring, e.g., cyclohexane, cyclopentane, morpholine, piperidine or cyclohexene. A bicyclic heterocycle includes any combination of ring sizes such as 4-5 fused ring systems, 5-5 fused ring systems, 5- 6 fused ring systems, 6-6 fused ring systems, 5-7 fused ring systems, 6-7 fused ring systems, 5-8 fused ring systems, and 6-8 fused ring systems. Bicyclic heterocycles may be fused, bridged, or spiro-ring systems. A spiro-ring system may be referred as a “spiro heterocycle” or “spiroheterocycle” or “spiro-ring heterocycle”. In some cases, spiro heterocycle, spiro-ring heterocycles or spiroheterocycles have at least two molecular rings with only one common atom.The spiro heterocycle, spiro-ring heterocycle or spiroheterocycle comprises one or more heteroatoms.

[0040] “Heteroaryl” or “aromatic heterocycle” refers to a radical derived from a heteroaromatic ring radical that comprises one to eleven carbon atoms and at least one heteroatom wherein each heteroatom may be selected from N, O, and S. As used herein, the heteroaryl ring may be selected from monocyclic or bicyclic and fused or bridged ring systems rings wherein at least one of the rings in the ring system is aromatic, i.e., it contains a cyclic, delocalized (4n+2) π– electron system in accordance with the Hückel theory. The heteroatom(s) in the heteroaryl radical may be optionally oxidized. One or more nitrogen atoms, if present, are optionally quaternized. The heteroaryl may be attached to the rest of the molecule through any atom of the heteroaryl, valence permitting, such as a carbon or nitrogen atom of the heteroaryl. Examples of heteroaryls include, but are not limited to, pyridine, pyrimidine, oxazole, furan, thiophene, benzthiazole, and imdazopyridine.

[0041] An “X-membered heteroaryl” refers to the number of endocylic atoms, i.e., X, in the ring. For example, a 5-membered heteroaryl ring or 5-membered aromatic heterocycle has 5 endocyclic atoms, e.g., triazole, oxazole, thiophene, etc.

[0042] The term “unsaturated heterocycle” refers to heterocycles with at least one degree of unsaturation and excluding aromatic heterocycles. Examples of unsaturated heterocycles include dihydropyrrole, dihydrofuran, oxazoline, pyrazoline, and dihydropyridine. Heterocycles may be optionally substituted by one or more substituents such as those substituents described herein.

[0043] The term “substituted” refers to moieties having substituents replacing a hydrogen on one or more carbons or substitutable heteroatoms, e.g., an NH or NH2of a compound. It will be understood that “substitution” or “substituted with” includes the implicit proviso that such substitution is in accordance with permitted valence of the substituted atom and the substituent, and that the substitution results in a stable compound, i.e., a compound which does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, etc. In certain embodiments, substituted refers to moieties having substituents replacing two hydrogen atoms on the same carbon atom, such as substituting the two hydrogen atoms on a single carbon with an oxo, imino or thioxo group. As used herein, the term “substituted” is contemplated to include all permissible substituents of organic compounds. In a broad aspect, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and non-aromatic substituents of organic compounds. The permissible substituents can be one or more and the same or different for appropriate organic compounds.

[0044] The term “heterocyclene” as used herein refers to a divalent saturated, unsaturated, non-aromatic or aromatic ring comprising one or more heteroatoms. Exemplary heteroatoms include N, O, Si, P, B, and S atoms. The heterocyclene is attached to the rest of the molecule through a single bond and to the radical group through a single bond. The single bond attaching the heterocyclene group to the rest of the molecule and the single bond attaching the heterocyclene group to the radical group may be each independently connected through any atom of the heterocyclene as valency permits, including a carbon atom in the heterocyclene ring or a heteroatom in the heterocyclene ring. A heterocyclene may be optionally substituted by one or more substituents such as those substituents described herein. Heterocyclenes include 3- to 10- membered monocyclic rings and polycyclic rings (e.g., 6- to 12-membered bicyclic rings). Each ring of a polycyclic heterocyclene may be selected from saturated, unsaturated, and aromatic rings. Polycyclic heterocyclenes may be fused, bridged or spiro-ring systems. The single bond connecting the heterocyclene to the rest of the molecule and the single bond connecting the heterocyclene to the radical group may be located on the same ring or different rings of a polycyclic heterocyclene and may be attached to the rest of the molecule or the radical group through any atom of the heterocyclene, valence permitting, such as a carbon or nitrogen atom of the heterocycle. In some embodiments, the heterocyclene comprises at least one heteroatom selected from oxygen, nitrogen, sulfur, or any combination thereof. In some embodiments, the heterocyclene comprises at least one heteroatom selected from oxygen, nitrogen, or any combination thereof. In some embodiments, the heterocyclene comprises at least one heteroatom selected from oxygen, sulfur, or any combination thereof. In some embodiments, the heterocyclene comprises at least one heteroatom selected from nitrogen, sulfur, or any combination thereof. In some embodiments, the heterocyclene is a heteroarylene. In some embodiments, the heterocyclene is a heterocycloalkylene.

[0045] In some embodiments, substituents may include any substituents described herein, for example: halogen, hydroxy, oxo (=O), thioxo (=S), cyano (-CN), nitro (-NO2), imino (=N-H), oximo (=N-OH), hydrazine (=N-NH2), -Rb-ORa, -Rb-OC(O)-Ra, -Rb-OC(O)-ORa, -Rb-OC(O)-N(Ra)2, -Rb-N(Ra)2, -Rb-C(O)Ra, -Rb-C(O)ORa, -Rb-C(O)N(Ra)2, -Rb-O-Rc-C(O)N(Ra)2, -Rb-N(Ra)C(O)ORa, -Rb-N(Ra)C(O)Ra, -Rb-N(Ra)S(O)tRa(where t is 1 or 2), -Rb-S(O)tRa(where t is 1 or 2), -Rb-S(O)tORa(where t is 1 or 2), and -Rb-S(O)tN(Ra)2(where t is 1 or 2); and alkyl, alkenyl, alkynyl, aryl, aralkyl, aralkenyl, aralkynyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heterocycloalkylalkyl, heteroaryl, and heteroarylalkyl any of which may be optionally substituted by alkyl, alkenyl, alkynyl, halogen, haloalkyl, haloalkenyl, haloalkynyl,oxo (=O), thioxo (=S), cyano (-CN), nitro (-NO2), imino (=N-H), oximo (=N-OH), hydrazine (=N-NH2), -Rb-ORa, -Rb-OC(O)-Ra, -Rb-OC(O)-ORa, -Rb-OC(O)-N(Ra)2, -Rb-N(Ra)2, -Rb-C(O)Ra, -Rb-C(O)ORa, -Rb-C(O)N(Ra)2, -Rb-O-Rc-C(O)N(Ra)2, -Rb-N(Ra)C(O)ORa, -Rb-N(Ra)C(O)Ra, -Rb-N(Ra)S(O)tRa(where t is 1 or 2), -Rb-S(O)tRa(where t is 1 or 2), -Rb-S(O)tORa(where t is 1 or 2) and -Rb-S(O)tN(Ra)2(where t is 1 or 2); wherein each Rais independently selected from hydrogen, alkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, heterocycloalkyl, heterocycloalkylalkyl, heteroaryl, or heteroarylalkyl, wherein each Ra, valence permitting, may be optionally substituted with alkyl, alkenyl, alkynyl, halogen, haloalkyl, haloalkenyl, haloalkynyl, oxo (=O), thioxo (=S), cyano (-CN), nitro (-NO2), imino (=N-H), oximo (=N-OH), hydrazine (=N-NH2), -Rb-ORa, -Rb-OC(O)-Ra, -Rb-OC(O)-ORa, -Rb-OC(O)-N(Ra)2, -Rb-N(Ra)2, -Rb-C(O)Ra, -Rb-C(O)ORa, -Rb-C(O)N(Ra)2, -Rb-O-Rc-C(O)N(Ra)2, -Rb-N(Ra)C(O)ORa, -Rb-N(Ra)C(O)Ra, -Rb-N(Ra)S(O)tRa(where t is 1 or 2), -Rb-S(O)tRa(where t is 1 or 2), -Rb-S(O)tORa(where t is 1 or 2) and -Rb-S(O)tN(Ra)2(where t is 1 or 2); and wherein each Rbis independently selected from a direct bond or a straight or branched alkylene, alkenylene, or alkynylene chain, and each Rcis a straight or branched alkylene, alkenylene or alkynylene chain. It will be understood by those skilled in the art that substituents can themselves be substituted, if appropriate.

[0046] The phrases “parenteral administration” and “administered parenterally” as used herein means modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraspinal and intrasternal injection and infusion.

[0047] The phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, and / or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit / risk ratio.

[0048] The phrase “pharmaceutically acceptable excipient” or “pharmaceutically acceptable carrier” as used herein means a pharmaceutically acceptable material, composition or vehicle, such as a liquid or solid filler, diluent, excipient, solvent or encapsulating material. Each carrier must be “acceptable” in the sense of being compatible with the other ingredients of the formulation and not injurious to the patient. Some examples of materials which can serve as pharmaceutically acceptable carriers include: (1) sugars, such as lactose, glucose and sucrose; (2)starches, such as corn starch and potato starch; (3) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen- free water; (17) isotonic saline; (18) Ringer’s solution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21) other non-toxic compatible substances employed in pharmaceutical formulations.

[0049] The terms “subject,” “individual,” and “patient” may be used interchangeably and refer to humans, the as well as non-human mammals (e.g., non-human primates, canines, equines, felines, porcines, bovines, ungulates, lagomorphs, and the like). In various embodiments, the subject can be a human (e.g., adult male, adult female, adolescent male, adolescent female, male child, female child) under the care of a physician or other health worker in a hospital, as an outpatient, or other clinical context. In certain embodiments, the subject may not be under the care or prescription of a physician or other health worker.

[0050] As used herein, the phrase “a subject in need thereof” refers to a subject, as described infra, that suffers from, or is at risk for, a pathology to be prophylactically or therapeutically treated with a compound or salt described herein.

[0051] The terms “administer”, “administered”, “administers” and “administering” are defined as providing a composition (e.g., conjguates) to a subject via a route known in the art, including but not limited to intravenous, intraarterial, oral, parenteral, buccal, topical, transdermal, rectal, intramuscular, subcutaneous, intraosseous, transmucosal, or intraperitoneal routes of administration. In certain embodiments, oral routes of administering a composition can be used.

[0052] The terms ““administer”, “administered”, “administers” and “administering” a compound should be understood to mean providing a compound of the invention (e.g., conjugates) to the individual in need.

[0053] The term “effective amount” or “therapeutically effective amount” refers to that amount of a compound or salt described herein that is sufficient to effect the intended application including but not limited to disease treatment, as defined below. The therapeutically effective amount may 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 byone of ordinary skill in the art. The term can also apply to a dose that can induce a particular response in target cells, e.g., reduction of proliferation or down regulation of activity of a target protein. The specific dose can vary depending on the particular compounds chosen, the dosing regimen to be followed, whether it is administered in combination with other compounds, timing of administration, the tissue to which it is administered, and the physical delivery system in which it is carried.

[0054] As used herein, “treatment” or “treating” refers to an approach for obtaining beneficial or desired results with respect to a disease, disorder, or medical condition including, but not limited to, a therapeutic benefit and / or a prophylactic benefit. In certain embodiments, treatment or treating involves administering a compound or composition disclosed herein to a subject. A therapeutic benefit may include the eradication or amelioration of the underlying disorder being treated. Also, a therapeutic benefit may be achieved with the eradication or amelioration of one or more of the physiological symptoms associated with the underlying disorder, such as observing an improvement in the subject, notwithstanding that the subject may still be afflicted with the underlying disorder. In certain embodiments, for prophylactic benefit, the compositions are administered to a subject at risk of developing a particular disease, or to a subject reporting one or more of the physiological symptoms of a disease, even though a diagnosis of this disease may not have been made. Treating can include, for example, reducing, delaying or alleviating the severity of one or more symptoms of the disease or condition, or it can include reducing the frequency with which symptoms of a disease, defect, disorder, or adverse condition, and the like, are experienced by a patient. Treating can be used herein to refer to a method that results in some level of treatment or amelioration of the disease or condition, and can contemplate a range of results directed to that end, including but not restricted to prevention of the condition entirely.

[0055] In certain embodiments, the term “prevent” or “preventing” as related to a disease or disorder may refer to a compound that, in a statistical sample, reduces the occurrence of the disorder or condition in the treated sample relative to an untreated control sample, or delays the onset or reduces the severity of one or more symptoms of the disorder or condition relative to the untreated control sample.

[0056] A “therapeutic effect,” as that term is used herein, encompasses a therapeutic benefit and / or a prophylactic benefit as described above. A prophylactic effect includes delaying or eliminating the appearance of a disease or condition, delaying or eliminating the onset of symptoms of a disease or condition, slowing, halting, or reversing the progression of a disease or condition, or any combination thereof.

[0057] The term “selective inhibition” or “selectively inhibit” as referred to a biologicallyactive agent refers to the agent’s ability to preferentially reduce the target signaling activity as compared to off-target signaling activity, via direct or interact interaction with the target.

[0058] "Linker", "Linker Unit", or "link" means a chemical moiety comprising a covalent bond or a chain of atoms that covalently attaches an antibody to a drug moiety. In various embodiments, a linker is specified as LU. Linkers include a divalent radical such as an alkyldiyl, an aryldiyl, a heteroaryldiyl, moieties such as: -(CR2)nO(CR2)n-, repeating units of alkyloxy (e.g., polyethylenoxy, PEG, polymethyleneoxy) and alkylamino (e.g., polyethyleneamino, Jeffamine™); and diacid ester and amides including succinate, succinamide, diglycolate, malonate, and caproamide.

[0059] The term "chiral" refers to molecules which have the property of nonsuperimposability of the mirror image partner, while the term "achiral" refers to molecules which are superimposable on their mirror image partner.

[0060] Chemical entities having carbon-carbon double bonds or carbon-nitrogen double bonds may exist in Z- or E- form (or cis- or trans- form). Furthermore, some chemical entities may exist in various tautomeric forms. Unless otherwise specified, compounds described herein are intended to include all Z-, E- and tautomeric forms as well.

[0061] “Isomers” are different compounds that have the same molecular formula. “Stereoisomers” are isomers that differ only in the way the atoms are arranged in space. “Enantiomers” are a pair of stereoisomers that are non-superimposable mirror images of each other. A 1:1 mixture of a pair of enantiomers is a “racemic” mixture. The term “(±)” is used to designate a racemic mixture where appropriate. “Diastereoisomers” or “diastereomers” are stereoisomers that have at least two asymmetric atoms but are not mirror images of each other. The absolute stereochemistry is specified according to the Cahn-Ingold-Prelog R-S system. When a compound is a pure enantiomer, the stereochemistry at each chiral carbon can be specified by either R or S. Resolved compounds whose absolute configuration is unknown can be designated (+) or (-) depending on the direction (dextro- or levorotatory) in which they rotate plane polarized light at the wavelength of the sodium D line. Certain compounds described herein contain one or more asymmetric centers and can thus give rise to enantiomers, diastereomers, and other stereoisomeric forms, the asymmetric centers of which can be defined, in terms of absolute stereochemistry, as (R)- or (S)-. The present chemical entities, pharmaceutical compositions and methods are meant to include all such possible stereoisomers, including racemic mixtures, optically pure forms, mixtures of diastereomers and intermediate mixtures. Optically active (R)- and (S)-isomers can be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques. The optical activity of a compound can beanalyzed via any suitable method, including but not limited to chiral chromatography and polarimetry, and the degree of predominance of one stereoisomer over the other isomer can be determined.

[0062] When stereochemistry is not specified, molecules with stereocenters described herein include isomers, such as enantiomers and diastereomers, mixtures of enantiomers, including racemates, mixtures of diastereomers, and other mixtures thereof, to the extent they can be made by one of ordinary skill in the art by routine experimentation. In certain embodiments, the single enantiomers or diastereomers, i.e., optically active forms, can be obtained by asymmetric synthesis or by resolution of the racemates or mixtures of diastereomers. Resolution of the racemates or mixtures of diastereomers, if possible, can be accomplished, for example, by conventional methods such as crystallization in the presence of a resolving agent, or chromatography, using, for example, a chiral high-pressure liquid chromatography (HPLC) column. Furthermore, a mixture of two enantiomers enriched in one of the two can be purified to provide further optically enriched form of the major enantiomer by recrystallization and / or trituration.

[0063] In certain embodiments, compositions of the disclosure may comprise two or more enantiomers or diatereomers of a compound wherein a single enantiomer or diastereomer accounts for at least about 70% by weight, at least about 80% by weight, at least about 90% by weight, at least about 98% by weight, or at least about 99% by weight or more of the total weight of all stereoisomers. Methods of producing substantially pure enantiomers are well known to those of skill in the art. For example, a single stereoisomer, e.g., an enantiomer, substantially free of its stereoisomer may be obtained by resolution of the racemic mixture using a method such as formation of diastereomers using optically active resolving agents (Stereochemistry of Carbon Compounds, (1962) by E. L. Eliel, McGraw Hill; Lochmuller (1975) J. Chromatogr., 113(3): 283-302). Racemic mixtures of chiral compounds can be separated and isolated by any suitable method, including, but not limited to: (1) formation of ionic, diastereomeric salts with chiral compounds and separation by fractional crystallization or other methods, (2) formation of diastereomeric compounds with chiral derivatizing reagents, separation of the diastereomers, and conversion to the pure stereoisomers, and (3) separation of the substantially pure or enriched stereoisomers directly under chiral conditions. Another approach for separation of the enantiomers is to use a Diacel chiral column and elution using an organic mobile phase such as done by Chiral Technologies (www.chiraltech.com) on a fee for service basis.

[0064] A "tautomer" refers to a molecule wherein a proton shift from one atom of a molecule to another atom of the same molecule is possible. The compounds presented herein, in certainembodiments, exist as tautomers. In circumstances where tautomerization is possible, a chemical equilibrium of the tautomers will exist. The exact ratio of the tautomers depends on several factors, including physical state, temperature, solvent, and pH. Some examples of tautomeric equilibrium include:.

[0065] The compounds disclosed herein, in some embodiments, are used in different enriched isotopic forms, e.g., enriched in the content of2H,3H,11C,13C and / or14C. In one particular embodiment, the compound is deuterated in at least one position. Such deuterated forms can be made by the procedure described in U.S. Patent Nos.5,846,514 and 6,334,997. As described in U.S. Patent Nos.5,846,514 and 6,334,997, deuteration can improve the metabolic stability and or efficacy, thus increasing the duration of action of drugs. In some cases, the compounds are Drug- Linkers. In some cases, the compounds are conjugates.

[0066] Unless otherwise stated, compounds described herein are intended to include compounds which differ only in the presence of one or more isotopically enriched atoms. For example, compounds having the present structures except for the replacement of a hydrogen by a deuterium or tritium, or the replacement of a carbon by13C- or14C-enriched carbon are within the scope of the present disclosure.

[0067] The compounds of the present disclosure optionally contain unnatural proportions of atomic isotopes at one or more atoms that constitute such compounds. For example, the compounds may be labeled with isotopes, such as for example, deuterium (2H), tritium (3H), iodine-125 (125I) or carbon-14 (14C). Isotopic substitution with2H,11C,13C,14C,15C,12N,13N,15N,16N,16O,17O,14F,15F,16F,17F,18F,33S,34S,35S,36S,35Cl,37Cl,79Br,81Br, and125I are allcontemplated. All isotopic variations of the compounds of the present invention, whether radioactive or not, are encompassed within the scope of the present invention.

[0068] In certain embodiments, the compounds disclosed herein have some or all of the1H atoms replaced with2H atoms. The methods of synthesis for deuterium-containing compounds are known in the art and include, by way of non-limiting example only, the following synthetic methods.

[0069] Deuterium substituted compounds are synthesized using various methods such as described in: Dean, Dennis C.; Editor. Recent Advances in the Synthesis and Applications of Radiolabeled Compounds for Drug Discovery and Development. [In: Curr., Pharm. Des., 2000; 6(10)] 2000, 110 pp; George W.; Varma, Rajender S. The Synthesis of Radiolabeled Compounds via Organometallic Intermediates, Tetrahedron, 1989, 45(21), 6601-21; and Evans, E. Anthony. Synthesis of radiolabeled compounds, J. Radioanal. Chem., 1981, 64(1-2), 9-32.

[0070] Deuterated starting materials are readily available and are subjected to the synthetic methods described herein to provide for the synthesis of deuterium-containing compounds. Large numbers of deuterium-containing reagents and building blocks are available commercially from chemical vendors, such as Aldrich Chemical Co.

[0071] Compounds of the present invention also include crystalline and amorphous forms of those compounds, pharmaceutically acceptable salts, and active metabolites of these compounds having the same type of activity, including, for example, polymorphs, pseudopolymorphs, solvates, hydrates, unsolvated polymorphs (including anhydrates), conformational polymorphs, and amorphous forms of the compounds, as well as mixtures thereof.

[0072] Included in the present disclosure are salts, particularly pharmaceutically acceptable salts, of the compounds described herein. The compounds of the present disclosure that possess a sufficiently acidic, a sufficiently basic, or both functional groups, can react with any of a number of inorganic bases, and inorganic and organic acids, to form a salt. Alternatively, compounds that are inherently charged, such as those with a quaternary nitrogen, can form a salt with an appropriate counterion, e.g., a halide such as bromide, chloride, or fluoride, particularly bromide.

[0073] The methods and compositions described herein include the use of amorphous forms as well as crystalline forms (also known as polymorphs). The compounds described herein may be in the form of pharmaceutically acceptable salts. As well, in some embodiments, active metabolites of these compounds having the same type of activity are included in the scope of the present disclosure. In addition, the compounds described herein can exist in unsolvated as well as solvated forms with pharmaceutically acceptable solvents such as water, ethanol, and the like.The solvated forms of the compounds presented herein are also considered to be disclosed herein.

[0074] Synthetic chemistry transformations and methodologies useful in synthesizing the compounds described herein are known in the art and include, for example, those described in R. Larock, Comprehensive Organic Transformations (1989); T. W. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, 2d. Ed. (1991); L. Fieser and M. Fieser, Fieser and Fieser's Reagents for Organic Synthesis (1994); and L. Paquette, ed., Encyclopedia of Reagents for Organic Synthesis (1995).

[0075] "Leaving group" refers to a functional group that can be substituted by another functional group. Such leaving groups are well known in the art, and examples include, but are not limited to, a halide (e.g., fluoride, chloride, bromide, iodide), methanesulfonyl (mesyl), p- toluenesulfonyl (tosyl), trifluoromethylsulfonyl (triflate), and trifluoromethylsulfonate.

[0076] The following abbreviations are used herein and have the indicated definitions: Boc is N- (t-butoxycarbonyl), cit is citrulline, dap is dolaproine, DCC is 1,3-dicyclohexylcarbodiimide, DCM is dichloromethane, DEA is diethylamine, DEAD is diethylazodicarboxylate, DEPC is diethylphosphorylcyanidate, DIAD is diisopropylazodicarboxylate, DIEA is N,N- diisopropylethylamine, dil is dolaisoleuine, DMAP is 4-dimethylaminopyridine, DME is ethyleneglycol dimethyl ether (or 1,2-dimethoxyethane), DMF is N,N-dimethylformamide, DMSO is dimethylsulfoxide, doe is dolaphenine, dov is N,N-dimethylvaline, DTNB is 5,5' - dithiobis(2-nitrobenzoic acid), DTP A is diethylenetriaminepentaacetic acid, DTT is dithiothreitol, EDCl is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, EEDQ is 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline, ES-MS is electrospray mass spectrometry, EtOAc is ethyl acetate, Fmoc is N-(9-fluorenylmethoxycarbonyl), gly is glycine, HATU is O-(7- azabenzotriazol-l -yl )-N,N,N',N'-tetramethyluronium hexafluorophosphate, HOBt is 1- hydroxybenzotriazole, HPLC is high pressure liquid chromatography, ile is isoleucine, lys is lysine, MeCN (CH3CN) is acetonitrile, MeOH is methanol, Mtr is 4-anisyldiphenylmethyl (or 4- methoxytrityl), nor is (1S, 2R)-(+)norephedrine, PAB is p-aminobenzyl, PBS is phosphate- buffered saline (pH 7.4), PEG is polyethylene glycol, Ph is phenyl, Pnp is p-nitrophenyl, MC is 6-maleimidocaproyl, phe is L-phenylalanine, PyBrop is bromo tris-pyrrolidino phosphonium hexafluorophosphate, SEC is size-exclusion chromatography, Su is succinimide, TBTU is O- benzotriazol-1-yl-N,N,N,N-tetramethyluronium tetrafluoroborate, TFA is trifluoroacetic acid, TLC is thin layer chromatography, UV is ultraviolet, and val is valine.

[0077] The following linker abbreviations are used herein and have the indicated definitions: Val Cit is a valine-citrulline, dipeptide site in protease cleavable linker; PAB is p-aminobenzylcarbamoyl; (Me)vc is N-methyl-valine citrulline, where the linker peptide bond has been modified to prevent its cleavage by cathepsin B; MC(PEG)6-0H is maleimidocaproyl- polyethylene glycol; SPP is N-Succinimidyl 4-(2-pyridylthio) pentanoate; and SMCC is N- Succinimidyl 4-(N-maleimidom ethyl) cyclohexane- 1 carboxylate.

[0078] When trade names are used herein, applicants intend to independently include the trade name product formulation, the generic drug, and the active pharmaceutical ingredient(s) of the trade name product.

[0079] The term "antibody" herein is used in the broadest sense and specifically covers intact monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies) formed from at least two intact antibodies, and antibody fragments, so long as they exhibit the desired biological activity. An antibody is a protein generated by the immune system that is capable of recognizing and binding to a specific antigen. Described in terms of its structure, an antibody typically has a Y-shaped protein consisting of four amino acid chains, two heavy and two light. Each antibody has primarily two regions: a variable region and a constant region. The variable region, located on the ends of the arms of the Y, binds to and interacts with the target antigen. This variable region includes a complementary determining region (CDR) that recognizes and binds to a specific binding site on a particular antigen. The constant region, located on the tail of the Y, is recognized by and interacts with the immune system. A target antigen generally has numerous binding sites, also called epitopes, recognized by CDRs on multiple antibodies. Each antibody that specifically binds to a different epitope has a different structure. Thus, one antigen may have more than one corresponding antibody.

[0080] The term "antibody" as used herein, also refers to a full-length immunoglobulin molecule or an immunologically active portion of a full-length immunoglobulin molecule, i.e., a molecule that contains an antigen binding site that immunospecifically binds an antigen of a target of interest or part thereof, such targets including but not limited to, cancer cell or cells that produce autoimmune antibodies associated with an autoimmune disease. The immunoglobulin disclosed herein can be of any type (e.g., IgG, IgE, IgM, IgD, and IgA), class (e.g., IgGl, IgG2, IgG3, IgG4, IgAl, and IgA2) or subclass of immunoglobulin molecule. The immunoglobulins can be derived from any species. In one aspect, however, the immunoglobulin is of human, murine, or rabbit origin. In another aspect, the antibodies are polyclonal, monoclonal, bispecific, human, humanized or chimeric antibodies, single chain antibodies, Fv, Fab fragments, F(ab') fragments, F(ab’)2fragments, fragments produced by a Fab expression library, anti -idiotypic (anti-Id) antibodies, CDR's, and epitope-binding fragments of any of the above which immunospecifically bind to cancer cell antigens, viral antigens or microbial antigens.

[0081] 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 site. Furthermore, in contrast to polyclonal antibody preparations which include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they may be synthesized uncontaminated by other antibodies. 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 invention may be made by the hybridoma method , or may be made by recombinant DNA methods. The "monoclonal antibodies" may also be isolated from phage antibody libraries.

[0082] The monoclonal antibodies 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 exhibit the desired biological activity.

[0083] Various methods have been employed to produce monoclonal antibodies (mAbs). Hybridoma technology, which refers to a cloned cell line that produces a single type of antibody, uses the cells of various species, including mice (murine), hamsters, rats, and humans. Another method to prepare MAbs uses genetic engineering including recombinant DNA techniques. Monoclonal antibodies made from these techniques include, among others, chimeric antibodies and humanized antibodies. A chimeric antibody combines DNA encoding regions from more than one type of species. For example, a chimeric antibody may derive the variable region from a mouse and the constant region from a human. A humanized antibody comes predominantly from a human, even though it contains nonhuman portions. Like a chimeric antibody, a humanized antibody may contain a completely human constant region. But unlike a chimeric antibody, the variable region may be partially derived from a human. The nonhuman, synthetic portions of a humanized antibody often come from CDRs in murine antibodies. In any event, these regions are crucial to allow the antibody to recognize and bind to a specific antigen.

[0084] As noted, murine antibodies can be used. While useful for diagnostics and short-term therapies, murine antibodies cannot be administered to people long-term without increasing the risk of a deleterious immunogenic response. This response, called Human Anti-Mouse Antibody (HAMA), occurs when a human immune system recognizes the murine antibody as foreign and attacks it. A HAMA response can cause toxic shock or even death.

[0085] Chimeric and humanized antibodies reduce the likelihood of a HAMA response by minimizing the nonhuman portions of administered antibodies. Furthermore, chimeric and humanized antibodies have the additional benefit of activating secondary human immune responses, such as antibody dependent cellular cytotoxicity.

[0086] "Antibody fragments" comprise a portion of an intact antibody, preferably comprising the antigen-binding or variable region thereof. Examples of antibody fragments include Fab, Fab', F(ab')2, and Fv fragments; diabodies; linear antibodies; single-chain antibody molecules; and multispecific antibodies formed from antibody fragment(s).

[0087] An "intact" antibody is one which comprises an antigen-binding variable region as well as a light chain constant domain (CL) and heavy chain constant domains, CH1, CH2 and CH3. The constant domains may be native sequence constant domains (e.g., human native sequence constant domains) or amino acid sequence variant thereof.

[0088] The intact antibody may have one or more "effector functions" which refer to those biological activities attributable to the Fc region (a native sequence Fc region or amino acid sequence variant Fc region) of an antibody. Examples of antibody effector functions include Clq binding; complement dependent cytotoxicity; Fc receptor binding; antibody-dependent cell- mediated cytotoxicity (ADCC); phagocytosis; down regulation of cell surface receptors (e.g., B cell receptor; BCR), etc.

[0089] Depending on the amino acid sequence of the constant domain of their heavy chains, intact antibodies can be assigned to different "classes." There are five major classes of intact antibodies: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into "subclasses" (isotypes), e.g., IgG1 , IgG2, IgG3, IgG4, IgA, and IgA2. The heavy-chain constant domains that correspond to the different classes of antibodies are called α, β, ε, γ, and μ, respectively. The subunit structures and three-dimensional configurations of different classes of immunoglobulins are well known.

[0090] The expressions "ErbB2" and "HER2" are used interchangeably herein and refer to human HER2 protein (Genebank accession number X03363). The term "erbB2" refers to the gene encoding human ErbB2 and "neu" refers to the gene encoding rat p185neu. Preferred ErbB2 is native sequence human ErbB2.

[0091] A "native sequence" polypeptide is one which has the same amino acid sequence as a polypeptide, e.g., tumor-associated antigen receptor, derived from nature. Such native sequence polypeptides can be isolated from nature or can be produced by recombinant or synthetic means. Thus, a native sequence polypeptide can have the amino acid sequence of naturally-occurring human polypeptide, murine polypeptide, or polypeptide from any other mammalian species.

[0092] The term "amino acid sequence variant" refers to polypeptides having amino acid sequences that differ to some extent from a native sequence polypeptide. Ordinarily, amino acid sequence variants will possess at least about 70% homology with at least one receptor binding domain of a native ligand, or with at least one ligand binding domain of a native receptor, such as a tumor-associated antigen, and preferably, they will be at least about 80%, more preferably, at least about 90% homologous with such receptor or ligand binding domains. The amino acid sequence variants possess substitutions, deletions, and / or insertions at certain positions within the amino acid sequence of the native amino acid sequence.

[0093] "Sequence identity" is defined as the percentage of residues in the amino acid sequence variant that are identical after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity. Methods and computer programs for the alignment are well known in the art.

[0094] The terms "Fc receptor" or "FcR" are used to describe a receptor that binds to the Fc region of an antibody. The preferred FcR is a native sequence human FcR. Moreover, a preferred FcR is one which binds an IgG antibody (a gamma receptor) and includes receptors of the FcγRI, FcγRII, and FcγRIII subclasses, including allelic variants and alternatively spliced forms of these receptors. FcyRII receptors include FcγRIIA (an "activating receptor") and FcγRIIB (an "inhibiting receptor"), which have similar amino acid sequences that differ primarily in the cytoplasmic domains thereof. Activating receptor FcyRIIA contains an immunoreceptor tyrosine-based activation motif (IT AM) in its cytoplasmic domain. Inhibiting receptor FcγRIIB contains an immunoreceptor tyrosine-based inhibition motif (ITTIM) in its cytoplasmic domain. Other FcRs, including those to be identified in the future, are encompassed by the term "FcR" herein. The term also includes the neonatal receptor, FcRn, which is responsible for the transfer of maternal IgGs to the fetus.

[0095] The term "variable" refers to the fact that certain portions of the variable domains differ extensively in sequence among antibodies and are used in the binding and specificity of each particular antibody for its particular antigen. However, the variability is not evenly distributed throughout the variable domains of antibodies. It is concentrated in three segments called hypervariable regions both in the light chain and the heavy chain variable domains. The morehighly conserved portions of variable domains are called the framework regions (FRs). The variable domains of native heavy and light chains each comprise four FRs, largely adopting a β- sheet configuration, connected by three hypervariable regions, which form loops connecting, and in some cases forming part of, the β-sheet structure. The hypervariable regions in each chain are held together in close proximity by the FRs and, with the hypervariable regions from the other chain, contribute to the formation of the antigen-binding site of antibodies. The constant domains are not involved directly in binding an antibody to an antigen, but exhibit various effector functions, such as participation of the antibody in antibody dependent cellular cytotoxicity (ADCC).

[0096] The term "hypervariable region" when used herein refers to the amino acid residues of an antibody which are responsible for antigen-binding. The hypervariable region generally comprises amino acid residues from a "complementarity determining region" or "CDR" (e.g., residues 24-34 (Ll), 50-56 (L2) and 89-97 (L3) in the light chain variable domain and 31-35 (Hl ), 50-65 (H2) and 95-102 (H3) in the heavy chain variable domain) and / or those residues from a "hypervariable loop:' (e.g., residues 26-32 (Ll), 50-52 (L2) and 91-96 (L3) in the light chain variable domain and 26- 32 (Hl), 53-55 (H2) and 96-101 (H3) in the heavy chain variable domain). "Framework Region" or "FR" residues are those variable domain residues other than the hypervariable region residues as herein defined.

[0097] Papain digestion of antibodies produces two identical antigen-binding fragments, called "Fab" fragments. each with a single antigen-binding site, and a residual "Fc" fragment, whose name reflects its ability to crystallize readily. Pepsin treatment yields an F(ab')2fragment that has two antigen-binding sites and is still capable of crosslinking antigen.

[0098] “Fv” is the minimum antibody fragment which contains a complete antigen-recognition and antigen-binding site. This region consists of a dimer of one heavy chain and one light chain variable domain in tight, non-covalent association. It is in this configuration that the three hypervariable regions of each variable domain interact to define an antigen-binding site on the surface of the VH-VL dimer. Collectively, the six hypervariable regions confer antigen-binding specificity to the antibody. However, even a single variable domain (or half of an Fv comprising only three hypervariable regions specific for an antigen) has the ability to recognize and bind antigen, although at a lower affinity than the entire binding site.

[0099] The Fab fragment also contains the constant domain of the light chain and the first constant domain (CH1) of the heavy chain. Fab' fragments differ from Fab fragments by the addition of a few residues at the carboxy terminus of the heavy chain CH1 domain including one or more cysteines from the antibody hinge region. Fab'-SH is the designation herein for Fab' inwhich the cysteine residue(s) of the constant domains bear at least one free thiol group. F(ab')2antibody fragments originally were produced as pairs of Fab' fragments which have hinge cysteines between them. Other chemical couplings of antibody fragments are also known.

[0100] The "light chains" of antibodies from any vertebrate species can be assigned to one of two clearly distinct types, called kappa (κ) and lambda (λ), based on the amino acid sequences of their constant domains.

[0101] "Single-chain Fv" or "scFv" antibody fragments comprise the VH and VL domains of antibody, wherein these domains are present in a single polypeptide chain. Preferably, the Fv polypeptide further comprises a polypeptide linker between the VH and VL domains which enables the scFv to form the desired structure for antigen binding.

[0102] The term "diabodies" refers to small antibody fragments with two antigenbinding sites, which fragments comprise a variable heavy domain (VH) connected to a variable light domain (VL) in the same polypeptide chain (VH - VL). By using a linker that is too short to allow pairing between the two domains on the same chain, the domains are forced to pair with the complementary domains of another chain and create two antigen-binding sites. Diabodies are known and have been described.

[0103] "Humanized" forms of non-human (e.g., rodent) antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulin. For the most part, humanized antibodies &re human immunoglobulins (recipient antibody) in which residues from a hypervariable region of the recipient are replaced by residues from a hypervariable region of a non-human species (donor antibody) such as mouse, rat, rabbit or nonhuman primate having the desired specificity, affinity, and capacity. In some instances, framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, humanized antibodies may comprise residues that are not found in the recipient antibody or in the donor antibody. These modifications are made to further refine antibody performance. 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 hypervariable loops correspond to those of a non-human immunoglobulin and all or substantially all of the FRs are those of a human immunoglobulin sequence. The humanized antibody optionally also will comprise at least a portion of an immunoglobulin constant region (Fe), typically that of a human immunoglobulin.

[0104] An "isolated" antibody is one which has been identified and separated and / or recovered from a component of its natural environment. Contaminant components of its natural environment are materials which would interfere with diagnostic or therapeutic uses for the antibody, and may include enzymes, hormones, and other proteinaceous or nonproteinaceoussolutes. In preferred embodiments, the antibody will be purified (1) to greater than 95% by weight of antibody as determined by the Lowry method, and most preferably more than 99% by weight. (2) to a degree sufficient to obtain at least 15 residues of N-terminal or internal amino acid sequence by use of a spinning cup sequenator, or (3) to homogeneity by SDS-PAGE under reducing or nonreducing conditions using Coomassie blue or, preferably, silver stain. Isolated antibody includes the antibody in situ within recombinant cells since at least one component of the antibody’s natural environment will not be present. Ordinarily, however, isolated antibody will be prepared by at least one purification step.

[0105] An antibody "which binds" an antigen of interest is one capable of binding that antigen with sufficient affinity such that the antibody is useful in targeting a cell expressing the antigen.

[0106] The term "therapeutically effective amount" refers to an amount of a drug effective to treat a disease or disorder in a mammal. In the case of cancer, the therapeutically effective amount of the drug may reduce the number of cancer cells; reduce the tumor size; inhibit (i.e., slow to some extent and preferably stop) cancer cell infiltration into peripheral organs; inhibit (i.e., slow to some extent and preferably stop) tumor metastasis; inhibit, to some extent, tumor growth; and / or relieve to some extent one or more of the symptoms associated with the cancer. To the extent the drug may prevent growth and / or kill existing cancer cells, it may be cytostatic and / or cytotoxic. For cancer therapy, efficacy can, for example, be measured by assessing the time to disease progression (TTP) and / or determining the response rate (RR).

[0107] The term "intracellular metabolite" refers to a compound resulting from a metabolic process or reaction inside a cell on an antibody drug conjugate (ADC). The metabolic process or reaction may be an enzymatic process such as proteolytic cleavage of a peptide linker of the ADC, or hydrolysis of a functional group such as a hydrazone, ester, or amide. Intracellular metabolites include, but are not limited to, antibodies and free drug which have undergone intracellular cleavage after entry, diffusion, uptake or transport into a cell.

[0108] The terms "intracellularly cleaved" and "intracellular cleavage" refer to a metabolic process or reaction inside a cell on an antibody drug conjugate or the like whereby the covalent attachment, e.g., the linker, between the drug moiety (D) and the antibody (Ab) is broken, resulting in the free drug dissociated from the antibody inside the cell. The cleaved moieties of the Drug-Ligand Conjugate, a Drug-Linker-Ligand Conjugate or ADC are thus intracellular metabolites.

[0109] The terms "cancer" and "cancerous" refer to or describe the physiological condition in mammals that is typically characterized by unregulated cell growth. A "tumor" comprises one or more cancerous cells.

[0110] An "ErbB2-expressing cancer" is one which produces sufficient levels of ErbB2 at the surface of cells thereof, such that an anti-ErbB2 antibody can bind thereto and have a therapeutic effect with respect to the cancer.

[0111] A cancer "characterized by excessive activation" of an ErbB2 receptor is one in which the extent of ErbB2 receptor activation in cancer cells significantly exceeds the level of activation of that receptor in non-cancerous cells of the same tissue type. Such excessive activation may result from overexpression of the ErbB2 receptor and / or greater than normal levels of an ErbB2 ligand available for activating the ErbB2 receptor in the cancer cells. Such excessive activation may cause and / or be caused by the malignant state of a cancer cell. In some embodiments, the cancer will be subjected to a diagnostic or prognostic assay to determine whether amplification and / or overexpression of an ErbB2 receptor is occurring which results in such excessive activation of the ErbB2 receptor. Alternatively, or additionally, the cancer may be subjected to a diagnostic or prognostic assay to determine whether amplification and / or overexpression an ErbB2 ligand is occurring in the cancer which attributes to excessive activation of the receptor. In a subset of such cancers, excessive activation of the receptor may result from an autocrine stimulatory pathway.

[0112] A cancer which "overexpresses" an ErbB2 receptor is one which has significantly higher levels of an ErbB2 receptor at the cell surface thereof, compared to a noncancerous cell of the same tissue type. Such overexpression may be caused by gene amplification or by increased transcription or translation. ErbB2 receptor overexpression may be determined in a diagnostic or prognostic assay by evaluating increased levels of the ErbB2 protein present on the surface of a cell (e.g., via an immunohistochemistry assay; IHC). Alternatively, or additionally, one may measure levels of ErbB2-encoding nucleic acid in the cell, e.g., via fluorescent in situ hybridization, southern blotting, or polymerase chain reaction (PCR) techniques, such as real time quantitative PCR (RT-PCR). Overexpression of the ErbB2 ligand, may be determined diagnostically by evaluating levels of the ligand (or nucleic acid encoding it) in the patient, e.g., in a tumor biopsy or by various diagnostic assays such as the IHC, FISH, southern blotting, PCR or in vivo assays described above. One may also study ErbB2 receptor overexpression by measuring shed antigen (e.g., ErbB2 extracellular domain) in a biological fluid such as serum. Aside from the above assays, various other in vivo assays are available to the skilled practitioner. For example, one may expose cells within the body of the patient to an antibody which is optionally labeled with a detectable label, e.g., a radioactive isotope, and binding of the antibody to cells in the patient can be evaluated, e.g., by external scanning for radioactivity or by analyzing a biopsy taken from a patient previously exposed to the antibody.

[0113] The tumors overexpressing HER2 are rated by immunohistochemical scores corresponding to the number of copies of HER2 molecules expressed per cell, and can been determined biochemically: 0 = 0-10,000 copies / cell, 1 + = at least about 200,000 copies / cell, 2+ = at least about 500,000 copies / cell, 3+ = about 1-2 x 106copies / cell. Overexpression of HER2 at the 3+ level, which leads to ligand-independent activation of the tyrosine kinase, occurs in approximately 30% of breast cancers, and in these patients, relapse-free survival and overall survival are diminished.

[0114] An "isolated" nucleic acid molecule is a nucleic acid molecule that is identified and separated from at least one contaminant nucleic acid molecule with which it is ordinarily associated in the natural source of the antibody nucleic acid. An isolated nucleic acid molecule is other than in the form or setting in which it is found in nature. Isolated nucleic acid molecules therefore are distinguished from the nucleic acid molecule as it exists in natural cells. However, an isolated nucleic acid molecule includes a nucleic acid molecule contained in cells that ordinarily express the antibody where, for example, the nucleic acid molecule is in a chromosomal location different from that of natural cells.

[0115] As used herein, the expressions "cell," "cell line," and "cell culture" are used interchangeably and all such designations include progeny. Thus, the words "transformants" and "transformed cells" include the primary subject cell and cultures derived therefrom without regard for the number of transfers. It is also understood that all progeny may not be precisely identical in DNA content, due to deliberate or inadvertent mutations. Mutant progeny that have the same function or biological activity as screened for in the originally transformed cell are included. Where distinct designations are intended, it will be clear from the context.

[0116] It is intended that every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.

[0117] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.Drug-Linkers / Conjugates

[0118] In an aspect, the present disclosure provides a conjugate represented by Formula la:or a pharmaceutically acceptable salt or solvate thereof, wherein: L is a Ligand unit Aa–Ww–Yyis a Linker unit (LU), wherein the Linker unit includes: A is a Stretcher unit; a is 0 or 1; each W is independently an Amino Acid unit; w is 0 to 12; Y is a Spacer unit; and y is selected from 0, 1, and 2; and each D is selected from a Roridin molecule; and p is an integer from 1 to 20.

[0119] In an aspect, the present disclosure provides a conjugate represented by Formula Ia::or a pharmaceutically acceptable salt or solvate thereof, wherein: Aa–Ww–Yyis a Linker unit (LU), wherein the Linker unit includes: A is a Stretcher unit; a is 0 or 1; each W is independently an Amino Acid unit; w is 0 to 12; Y is a Spacer unit; and y is selected from 0, 1, and 2; and each D is selected from a Roridin molecule; and p is an integer from 1 to 20.

[0120] In another aspect, the present disclosure provides Drug-Linker-Ligand Compounds having Formula (II):or a pharmaceutically acceptable salt or solvate thereof, wherein: L is a Ligand unit;Aa–Ww–Yyis a Linker unit (LU), wherein the Linker unit includes: A is a Stretcher unit; a is 0 or 1; each W is independently an Amino Acid unit; w is an integer from 0 to 12; Y is a Spacer unit; and y is 0, 1 or 2; and p is an integer from 1 to 20; and each D is a Drug unit.

[0121] In an aspect, the present disclosure provides a Drug-Linker of Formula I:or a pharmaceutically acceptable salt thereof, wherein: each Y is independently a Spacer unit; y is selected from 0, 1, and 2; D is a Drug unit; each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1.

[0122] In some embodiments, for the Drug-Linker of Formula I, D is selected from a Trichothecene.

[0123] In some embodiments, for the Drug-Linker of Formula I, D is selected from, wherein E is absent or an Extender unit; X is selected from -N(R1)-, -O-, and heterocycle; R1is selected from hydrogen and C1-6alkyl; R2is selected from hydrogen and -OR10;R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, -S(O)2R20, -P(O)(OR20)2, - Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10- membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0124] In some embodiments, for the Drug-Linker of Formula I, D isor a pharmaceutically acceptable salt thereof.

[0125] In some embodiments, for the Drug-Linker of Formula I, D is, or a pharmaceutically acceptable salt thereof.

[0126] In some embodiments, for the Drug-Linker of Formula I, D isor a pharmaceutically acceptable salt thereof.

[0127] In some embodiments, the Drug-Linker of Formula I is represented by Formula I-RA-a*:, or a pharmaceutically acceptable salt thereof.

[0128] In some embodiments, the Drug-Linker of Formula I is represented by Formula I-RA-b*:or a pharmaceutically acceptable salt thereof.

[0129] In some embodiments, the Drug-Linker of Formula I is represented by Formula I-RE*:or a pharmaceutically acceptable salt thereof.

[0130] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from C1-C20alkylene, C1-C20alkenylene, and C1-C20alkynylene, wherein one or more CH2units of the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, – C(O)N(R30)–, –S(O)2–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene, and 4- to 10-membered heterocyclene are each optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, oxo, -OR30, -N(R30)2, -C(O)R30, - C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C3-10carbocycle and 4- to 10- membered heterocycle are each optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle and 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)N(R30)2, - S(O)2(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; wherein the C3-10carbocycle and 4- to 10-membered heterocycle are each optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle and 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)(NH2), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, oxo, -OH, -CN, - NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a C3-C6carbocycle or 4- to 10-membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0131] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are each optionally substituted with one or more substituents independently selected from halogen, oxo, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0132] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from.

[0133] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from C1-C20alkylene, C1-C20alkenylene, and C1-C20alkynylene, wherein one or more CH2units of the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, – C(O)N(R30)–, –S(O)2–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene, and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), - C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, - NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0134] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, - N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, - N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, - NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, - NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0135] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, wherein E is selected from C1-C20alkylene,wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, - S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0136] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -S(O)2R30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0137] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from C1-C20alkylene,wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -C(O)OR30, -C(O)N(R30)2, -S(O)2R30, and 4- to 10-membered heterocycle, wherein the 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0138] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from

[0139] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is selected from

[0140] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, X is selected from heterocycle. In some cases, the heterocycle is a heteroaryl. In some cases, the heterocycle is a 5- to 6-membered heterocycle. In some cases, X is a 5- to 6-membered heterocycle. In some cases, X is a 5- to 6-membered heterocycle. In some cases, X is

[0141] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, X is selected fromIn some cases, X is,

[0142] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, X is selected from

[0143] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, or Formula I- RA-b*, R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, - S(O)2OR20, -S(O)2R20, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0144] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, or Formula I- RA-b*, R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -S(O)2N(R20)2, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; andeach R20is independently selected from hydrogen, C1-6alkyl, and 4- to 6-membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0145] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, or Formula I- RA-b*, R2is selected from, , , , In some c2ases, R is selected fromIn some cases, R2is selected fromIn some cases, R2is selected fromand. In some cases, R2is selected from from, , .

[0146] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, or Formula I- RA-b*, R2is selected from, , , , ,

[0147] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, or Formula I- RA-b*, R2is selected from.

[0148] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, or Formula I-RE*, E is absent.

[0149] In some embodiments, the Drug-Linker of Formula I or Formula I-RA-a* is represented by Formula I-RA-a:or a pharmaceutically acceptable salt thereof.

[0150] In some embodiments, the Drug-Linker of Formula I or Formula I-RA-b* is represented by Formula I-RA-b:, or a pharmaceutically acceptable salt thereof.

[0151] In some embodiments, the Drug-Linker of Formula I or Formula I-RE* is represented by Formula I-RE:or a pharmaceutically acceptable salt thereof.

[0152] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, y is 1. In some cases, y is 2.

[0153] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Y is selected from

[0154] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, y is 0.

[0155] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, w is 1. In some cases, w is 2. In some caes, w is 3. In some cases, w is 4.

[0156] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, each W isindependently selected from, ,

[0157] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, each W is independently selected from

[0158] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, a is 1.

[0159] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, A is selected from.

[0160] In some embodiments, for the Drug-Linker of Formula I, Formula I-RA-a*, Formula I- RA-b*, Formula I-RE*, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, A is selected from

[0161] In some embodiments, for the Drug-Linker of Formula I, the Drug-Linker is:or a pharmaceutically acceptable salt thereof.

[0162] In some embodiments, for the Drug-Linker of Formula I, the Drug-Linker is:, or a pharmaceutically acceptable salt thereof.

[0163] In some embodiments, for the Drug-Linker of Formula I, the Drug-Linker is:or a pharmaceutically acceptable salt thereof.

[0164] In some embodiments, for the Drug-Linker of Formula I, the Drug-Linker is selected from:, or a pharmaceutically acceptable salt of any one thereof.

[0165] In some embodiments, for the Drug-Linker of Formula I, the Drug-Linker is selected from Table 2.

[0166] In some embodiments, for the Drug-Linker of Formula I, the Drug-Linker is selected from compound DL-1 to DL-84.

[0167] In some embodiments, for the Drug-Linker of Formula I, further comprises an antibody (Ab) to form a conjugate, wherein Ab is attached to A, wherein A has reacted and formed a covalent bond to Ab.each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1.

[0168] In some embodiments, an Antibody-Drug Conjugate may be referred to as Conjugate.

[0169] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, the Drug-Linker is selected from:,or a pharmaceutically acceptable salt thereof. In some cases, the Drug-Linker is selected from:pharmaceutically acceptable salt thereof. In some cases, the Drug-Linker is:pharmaceutically acceptable salt thereof. In some cases, the Drug-Linker is:pharmaceutically acceptable salt thereof. In some cases, the Drug-Linker is:or a pharmaceutically acceptable salt thereof.

[0170] In an aspect, the present disclosure provides a Conjugate of Formula IIa:or a pharmaceutically acceptable salt thereof, wherein: Ab is an antibody or an antigen-binding portion thereof; each Y is independently a Spacer unit; y is selected from 0, 1, and 2; each D is a Drug unit; p is an integer from 1 to 20;

[0171] In some embodiments, Ab is an antibody.

[0172] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, the conjugate is selected from:,or a pharmaceutically acceptable salt of any one thereof. In some cases, the conjugate is selected from:andor a pharmaceutically acceptable salt of any one thereof. In some cases, the conjugate is represented by:pharmaceutically acceptable salt thereof. In some cases, the conjugate is represented by:or a pharmaceutically acceptable salt thereof. In some cases, the conjugate is represented by:pharmaceutically acceptable salt thereof.

[0173] In some embodiments, for a conjugate or salt of Formula Ila, D is selected from a Trichothecene.

[0174] In some embodiments, for a conjugate or salt of Formula Ila, D is selected fromE is absent or an Extender unit; X is selected from -N(R1)-, -O-, and heterocycle; R1is selected from hydrogen and C1-6alkyl; R2is selected from hydrogen and -OR10; R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, - S(O)2R20, -P(O)(OR20)2, -Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, - N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0175] In some embodiments, the conjugate or salt of Formula IIa is represented by Formula II- RA-a*:or a pharmaceutically acceptable salt thereof.

[0176] In some embodiments, the conjugate or salt of Formula IIa is represented by Formula II- RA-b*:or a pharmaceutically acceptable salt thereof.

[0177] In some embodiments, the conjugate or salt of Formula IIa is represented by Formula II- RE*:or a pharmaceutically acceptable salt thereof

[0178] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from C1-C20alkylene, C1-C20alkenylene, and C1-C20alkynylene, wherein one or more CH2units of the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, – C(O)N(R30)–, –S(O)2–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene, and 4- to 10-membered heterocyclene are each optionally substituted with one or more substituents independently selected from halogen, oxo, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, - C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR20, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C3-10carbocycle and 4- to 10- membered heterocycle are each optionally substituted with one or more substituentsindependently selected from halogen, oxo, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, - NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle, 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)N(R30)2, - S(O)2(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; wherein the C3-10carbocycle and 4- to 10-membered heterocycle are each optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle and 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)(NH2), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, oxo, -OH, -CN, - NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a C3-C6carbocycle or 4- to 10-membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0179] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from C1-C20alkylene, C1-C20alkenylene, and C1-C20alkynylene, wherein one or more CH2units of the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, – C(O)N(R30)–, –S(O)2–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene, and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen,-OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), - C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, - NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0180] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, - N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, - N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, - NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, - NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independentlyselected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0181] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, - S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0182] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -S(O)2R30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl;each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0183] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -C(O)OR30, -C(O)N(R30)2, -S(O)2R30, and 4- to 10-membered heterocycle, wherein the 4- to 10-membered heterocycle is optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0184] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -S(O)2R30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0185] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*,E is selected from,.

[0186] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is selected from

[0187] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, X is selected from heterocycle. In some cases, the heterocycle is a heteroaryl. In some cases, the heterocycle is a 5- to 6-membered heterocycle. In some cases, X is a 5- to 6-membered heterocycle. In some cases, X is a 5- to 6-membered heterocycle. In some cases, X is

[0188] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, X is selected fromsome cases, X is

[0189] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, X is selected from, , In some cases, X is selected from. In some cases, X is.

[0190] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, - S(O)2OR20, -S(O)2R20, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0191] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -S(O)2N(R20)2, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, and 4- to 6-membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0192] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, R2is selected from,

[0193] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, R2is selected from.

[0194] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, E is absent.

[0195] In some embodiments, for a conjugate or salt of Formula IIa, the conjugate of Formula IIa or Formula II-RA-a* is represented by Formula II-RA-a:or a pharmaceutically acceptable salt thereof.

[0196] In some embodiments, for a conjugate or salt of Formula IIa, the conjugate of Formula IIa or Formula II-RA-b* is represented by Formula II-RA-b:or a pharmaceutically acceptable salt thereof.

[0197] In some embodiments, for a conjugate or salt of Formula IIa, the conjugate of Formula IIa or Formula II-RE* is represented by Formula II-RE:or a pharmaceutically acceptable salt thereof.

[0198] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, y is 1. In some cases, y is 0.

[0199] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, Y is selectedIn some cases, Y is.

[0200] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, w is 1.

[0201] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, each W is

[0202] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, each W is.

[0203] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, a is 1

[0204] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, A is selected

[0205] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, A is selected,

[0206] In some embodiments, the conjugate of Formula Ila includes a compound of Illa.

[0207] In some embodiments, for a conjugate of Formula Ila or the drug linker of Formula I, D is selected fromwherein D isE is selected fromX1is selected fromand R2is selected from21In some cases, R is selected fromIn some X isIn some X1is

[0208] In some embodiments, for a compound of IIIa, wherein P isE1is selected from ,,; X1is selected from, , ; and R2is selected from, , , , In some cases, R2is selected fromIn some X1isIn some X1is1In some cases, E is selected from, , , , , In some cases, E1is selected from

[0209] In some embodiments, for a conjugate or salt of Formula Ila, Formula II-RA-a, or Formula II-RA-a*, the conjugate is represented by:or a pharmaceutically acceptable salt thereof.

[0210] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-b, or Formula II-RA-b*, the conjugate is represented by:, or a pharmaceutically acceptable salt thereof.

[0211] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RE, or Formula II-RE*, the conjugate is represented by:, or a pharmaceutically acceptable salt thereof.

[0212] In some embodiments, for a conjugate or salt of Formula IIa, the conjugate is selected from:.

[0213] In some embodiments, for a conjugate or salt of Formula IIa, the conjugate is selected from Table 3.

[0214] In some embodiments, for a conjugate or salt of Formula IIa, the conjugate is selected from compound C-1 to C-82, Ab is as defined in Table 3.

[0215] In some embodiments, for a conjugate or salt of Formula IIa, the conjugate is selected from Table AA.

[0216] In some embodiments, for a conjugate or salt of Formula IIa, the Ab is selected from trastuzumab and Sacituzumab .

[0217] In some embodiments, for a conjugate or salt of Formula IIa, p is selected from 2 to 8. In some cases, p is 4. In some cases, p is 8.

[0218] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, p is an integer from 1 to 20. In some cases, p is an integer from 1 to 16. In some cases, p is an integer from 1 to 12. In some cases, p is an integer from 1 to 8. In some cases, p is an integer from 1 to6. In some cases, p is an integer from 1 to 4. In some cases, p is an integer from 1 to 2. In some cases, p is 1. In some cases, p is selected from 2 to 8. In some cases, p is 2. In some cases, p is 4. In some cases, p is 6. In some cases, p is 8. In some cases, p is 10. In some cases, p is 12. In some cases, p is 14. In some cases, p is 16. In some cases, p is 18. In some cases, p is 20.

[0219] The drug loading is represented by p, the average number of drug molecules per antibody in a molecule (e.g., of Formula la, la’ , II, and lia). Drug loading may range from 1 to 20 drugs (D) per Ligand (eg. Ab or mAb ). The average number of drugs per antibody in preparation of conjugation reactions may be characterized by conventional means such as mass spectroscopy, ELISA assay, and HPLC. The quantitative distribution of Ligand-Drug-Conjugates in terms of p may also be determined. In some instances, separation, purification, and characterization of homogeneous Ligand-Drug-conjugates where p is a certain value from Ligand-Drug Conjugates with other drug loadings may be achieved by means such as reverse phase HPLC or electrophoresis.

[0220] For some antibody drug conjugates, p may be limited by the number of attachment sites on the antibody. For example, where the attachment is a cysteine thiol, as in the exemplary embodiments above, an antibody may have only one or several cysteine thiol groups, or may have only one or several sufficiently reactive thiol groups through which a linker may be attached.

[0221] Typically, fewer than the theoretical maximum of drug moieties are conjugated to an antibody during a conjugation reaction. An antibody may contain, for example, many lysine residues that do not react with the drug-linker intermediate or linker reagent. Only the most reactive lysine groups may react with an amine-reactive linker reagent. Generally, antibodies do not contain many, if any, free and reactive cysteine thiol groups which may be linked to a drug moiety. Most cysteine thiol residues in the antibodies of the compounds of the invention exist as disulfide bridges and must be reduced with a reducing agent such as dithiothreitol (DTT). Additionally, the antibody must be subjected to denaturing conditions to reveal reactive nucleophilic groups such as lysine or cysteine. The loading (drug / antibody ratio) of an ADC may be controlled in several different manners, including: (i) limiting the molar excess of druglinker intermediate or linker reagent relative to antibody, (ii) limiting the conjugation reaction time or temperature, and (iii) partial or limiting reductive conditions for cysteine thiol modification.

[0222] In some embodiments, where more than one nucleophilic group reacts with a drug-linker intermediate, or linker reagent followed by drug moiety reagent, then the resulting product is a mixture of ADC compounds with a distribution of one or more drug moieties attached to anantibody. The average number of drugs per antibody may be calculated from the mixture by dual ELISA antibody assay, specific for antibody and specific for the drug. Individual ADC molecules may be identified in the mixture by mass spectroscopy, and separated by HPLC, e.g., hydrophobic interaction chromatograph. Thus, a homogeneous ADC with a single loading value may be isolated from the conjugation mixture by electrophoresis or chromatography.

[0223] THE LINKER UNIT

[0224] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila, or Formula II, includes a Linker unit.

[0225] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula LRA-b*, or Formula I-RE*, includes a Linker unit.

[0226] The “Linker unit” (LU) is a bifunctional compound which can be used to link a Drug unit and an Ligand unit to form a conjugate, or which are useful in the formation of immunoconjugates directed against tumor associated antigens. Such immunoconjugates allow the selective delivery of toxic drugs to tumor cells.

[0227] The Linker unit has the formula:wherein: each Y is independently a Spacer unit; y is selected from 0, 1, and 2; each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1. wherein: for the Drug-Linker, the Linker is capable of linking the Drug moiety (the wavy line on Aais absent); for the conjugate, the Linker is capable of linking the Drug moiety and the Ligand unit / Antibody; and the wavy lines indicate the covalent attachment to either the Ligand / Antibody or D.

[0228] THE STRETCHER UNIT

[0229] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila, or Formula II, includes a Stretcher unit.

[0230] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, includes a Stretcher unit.

[0231] The Stretcher unit (-A-), when present, is capable of linking a Ligand unit to an amino acid unit (-W-). In this regard a Ligand (L-) has a functional group that can form a bond with a functional group of a Stretcher. Useful functional groups that can be present on a ligand, either naturally or via chemical manipulation include, but are not limited to, sulfhydryl (-SH), amino, hydroxyl, carboxy, the anomeric hydroxyl group of a carbohydrate, and carboxyl. In one aspect, the Ligand functional groups are sulfhydryl and amino. Sulfhydryl groups can be generated by reduction of an intramolecular disulfide bond of a Ligand. Alternatively, sulfhydryl groups can be generated by reaction of an amino group of a lysine moiety of a Ligand using 2-iminothiolane (Traut’s reagent) or another sulfhydryl generating reagent.

[0232] The Stretcher unit forms a bond with a sulfur atom of the Ligand unit. The sulfur atom can be derived from a sulfhydryl group of a Ligand. Representative Stretcher units of this embodiment are depicted within the square brackets of Formulas IVa and IVb, wherein L-, -W-, -Y-, -D, wand y are as defined above, and R30is selected from – C1-C10alkylene-, -C3-C8carbocyclo-, -O-(C3-C8alkyl)-, -arylene-, -C1-C10alkylene-arylene-, -arylene-C1-C10alkylene-, - C1-C10alkylene-(C3-C8carbocyclo)-, -(C3-C8carbocyclo)- C1-C10 alkylene-, -C3-C8heterocyclo- , -C1-C10alkylene-(C3-C8heterocyclo)-, -(C3-C8heterocyclo)-C1-C10alkylene-, -(CH2CH2O)r-, and –(CH2CH2O)r-CH2-; and r is an integer from 1 to 10. It is to be understood from all the exemplary embodiments of Formula Ia, such as IV-VII (and sub-formulas), that even where not denoted expressly, from 1 to 20 drug moieties are linked to a Ligand (p = 1 to 20) by the appropriate number of Linker units.

[0233] An illustrative Stretcher unit is that of Formula IVa wherein R30is –(CH2)5-:

[0234] An illustrative Stretcher unit is that of Formula IVa wherein R30is –(CH2CH2O)r-CH2-; and r is 2:

[0235] An illustrative Stretcher unit is that of Formula IVb wherein R30wherein R30is –(CH2)5-:

[0236] In some embodiments, the Stretcher unit is linked to the Ligand unit via a disulfide bond between a sulfur atom of the Ligand unit and a sulfur atom of the Stretcher unit. A representative Stretcher unit of this embodiment is depicted within the square brackets of Formula V, wherein R30, L-, -W-, -Y-, -D, w and y are as defined above.

[0237] In some embodiments, the reactive group of the Stretcher contains a reactive site that can form a bond with a primary or secondary amino group of a Ligand. Example of these reactive sites include, but are not limited to, activated esters such as succinimide esters, 4-nitrophenyl esters, pentafluorophenyl esters, tetrafluorophenyl esters, anhydrides, acid chlorides, sulfonyl chlorides, isocyanates and isothiocyanates.

[0238] Representative Stretcher units of this embodiment are depicted within the square brackets of Formulas VIa and VIb, wherein -R30-. L-, -W-, -Y-, -D, w and y are as defined above.

[0239] In some embodiments, the reactive group of the Stretcher contains a reactive site that is reactive to a modified carbohydrate’s (-CHO) group that can be present on a Ligand. For example, a carbohydrate can be mildly oxidized using a reagent such as sodium periodate and the resulting (-CHO) unit of the oxidized carbohydrate can be condensed with a Stretcher that contains a functionality such as a hydrazide, an oxime, a primary or secondary amine, a hydrazine, a thiosemicarbazone, a hydrazine carboxylate, and an arylhydrazide such as those known to one skilled in the art. Representative Stretcher units of this embodiment are depicted within the square brackets of Formulas VIIa, VIIb, and VIIc, wherein -R30, L-, -W-, -Y-, -D, w and y are as defined above.

[0240] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, a is 0 or 1. In some cases, a is 1. In some cases, a is 0.

[0241] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, each A is independently a Stretcher unit. In some cases A is a Stretcher unit. In some cases, A is, and a is 1.

[0242] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, a is 0 or 1. In some cases, wherein a is 1. In some cases, A is 0.

[0243] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, each A is independently a Stretcher unit. In some cases A is a Stretcher unit. In some cases, A isIn some cases, A isand a is 1.

[0244] THE AMINO ACID UNIT

[0245] In some embodiments, for a Drug-Linker or salt of Formula I, or a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa, or Formula II, includes an Amino Acid unit.

[0246] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, includes an Amino Acid unit.

[0247] The Amino Acid unit (-W-), when present, links the Stretcher unit to the Spacer unit if the Spacer unit is present, links the Stretcher unit to the Drug moiety if the Spacer unit is absent, and links the Ligand unit to the Drug unit if the Stretcher unit and Spacer unit are absent.

[0248] In some embodiments, Ww is a dipeptide, tripeptide, tetrapeptide, pentapeptide, hexapeptide, heptapeptide, octapeptide, nonapeptide, decapeptide, undecapeptide or dodecapeptide unit. Each -W- unit independently is selected from the formulae denoted below in the square brackets, and w is an integer from 0 to 12:wherein R31is selected from hydrogen, methyl, isopropyl, isobutyl, sec-butyl, benzyl, p- hydroxybenzyl, -CH2OH, -CH(OH)CH3, -CH2CH2SCH3, -CH2CONH2, -CH2CO2H, - CH2CH2CONH2, -CH2CH2CO2H, -(CH2)3NHC(=NH)NH2, -(CH2)3NH2, -(CH2)3NHCOCH3, - (CH2)3NHCHO, -(CH2)4NHC(=NH)NH2, -(CH2)4NH2, -(CH2)4NHCOCH3, -(CH2)4NHCHO, - (CH2)3NHCONH2, -(CH2)4NHCONH2, -CH2CH2CH(OH)CH2NH2, 2-pyridylmethyl-, 3- pyridylmethyl-, 4-pyridylmethyl-, phenyl, cyclohexyl,

[0249] The Amino Acid unit can be enzymatically cleaved by one or more enzymes, including a tumor-associated protease, to liberate the Drug unit (-D), which in some embodiments is protonated in vivo upon release to provide a Drug (D). In some cases, the released drug is a Roridin compound. In some cases, the released drug is Roridin A. In some cases, the released Drug isIn some cases, the released Drug is Roridin E. In some cases, the released Drug isIllustrative Ww units are represented by formulas (VIII), (VIII*), or (IX):wherein R32and R33are as follows:wherein R32, R33, and R34are as follows:wherein R32, R33, R34, and R35are as follows:

[250] Exemplary Amino Acid units include, but are not limited to, units of formula (VIII) where: R32is benzyl and R33is –(CH2)4NH2; R32isopropyl and R33is –(CH2)4NH2; R32isopropyl and R33is –(CH2)3NHCONH2. Another exemplary Amino Acid unit is a unit of formula (VIII*) wherein R32is benzyl, R33is benzyl, and R34is -(CH2)4NH2.

[0251] Useful -Ww- units can be designed and optimized in their selectivity for enzymatic cleavage by a particular enzymes, for example, a tumor-associated protease.

[0252] In some embodiments, a -Ww- unit is that whose cleavage is catalyzed by cathepsin B, C and D, or a plasmin protease.

[0253] In some embodiments, -Ww- is a dipeptide, tripeptide, tetrapeptide or pentapeptide.

[0254] In some embodiments, when R31, R32, R33, R34, or R35 is other than hydrogen, the carbon atom to which R31, R32, R33, R34, or R35is attached is chiral.

[0255] Each carbon atom to which R31, R32, R33, R34, or R35 is attached is independently in the (S) or (R) configuration.

[0256] In some embodiments of the Amino Acid unit, the Amino Acid unit is valine-citrulline.

[0257] In some embodiments, the Amino Acid unit is phenylalanine-lysine (i.e. fk).

[0258] In some embodiments of the Amino Acid unit, the Amino Acid unit is N-methylvaline- citrulline.

[0259] In some embodiments, the Amino Acid unit is 5-aminovaleric acid, homo phenylalanine lysine, tetraisoquinolinecarboxylate lysine, cyclohexylalanine lysine, isonepecotic acid lysine, beta-alanine lysine, glycine, serine, valine, glutamine, and isonepecotic acid.

[0260] In some embodiments, the Amino Acid unit can comprise natural amino acids.

[0261] In some embodiments, WW is -Val-Cit-. In some cases, Ww is

[0262] In some embodiments, the Amino Acid unit can comprise non-natural amino acids.

[0263] In some embodiments, the Amino Acid unit is selected fromIn some cases, the Amino Acid unit is. In some cases, the Amino Acid unit is

[0264] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, w is 0 to 12. In some cases, w is 0 to 10. In some cases, w is 0 to 8. In some cases, w is 0 to 6. In some cases, w is 0 to 4. In some cases, w is 0 to 2. In some cases, w is 0 or 1. In some cases, w is 0. In some cases, w is 1.

[0265] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, each W is independently an Amino Acid unit. In some cases, each W is independently selected fromIn some cases, W is independently selected fromand w is 1 to 2. In some cases, W is independently selected fromandand w is 1. In some cases, W isIn some cases. W isIn some cases, W isand w is 1 to 2. In some cases. W isand w is 1 to 2. In some cases, W isand w is 1. In some cases. W isand w is 1. In some cases, W is selected from

[0266] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, w is 0 to 12. In some cases, w is 0 to 10. In some cases, w is 0 to 8. In some cases, w is 0 to 6. In some cases, w is 0 to 4. In some cases, w is 0 to 2. In some cases, w is 0 or 1. In some cases, w is 0. In some cases, w is 1.

[0267] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, each W is independently an Amino Acid unit. In some cases, each W is independently selected fromIn some cases, W is independently selected fromand w is 1 to 2. In some cases, W is independently selected fromandand w is 1. In some cases, W isIn some cases. W isIn some cases, W isand w is 1 to 2. In some cases. W isand w is 1 to 2. In some cases, W isand w is 1. In some cases. W isand w is 1. In some cases, W isIn some cases, Wwis, wherein w is 1 to 5. In some cases, w is 1. In some cases, w is 2. In some cases, w is 3. In some cases, w is 4.

[0268] THE SPACER UNIT

[0269] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, or a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa, or Formula II, includes a Spacer unit.

[0270] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, includes a Spacer unit.

[0271] The Spacer unit (-Y-), when present, links an Amino Acid unit to the Drug moiety when an Amino Acid unit is present. Alternately, the Spacer unit links the Stretcher unit to the Drug moiety when the Amino Acid unit is absent. The Spacer unit also links the Drug moiety to the Ligand unit when both the Amino Acid unit and Stretcher unit are absent.

[0272] Spacer units are of two general types: self-immolative and non self-immolative. A non self-immolative Spacer unit is one in which part or all of the Spacer unit remains bound to the Drug moiety after cleavage, particularly enzymatic, of an Amino Acid unit from the Drug- Linker-Ligand Conjugate or the Drug-Linker Compound. Examples of a non self-immolative Spacer unit include, but are not limited to a (glycineglycine) Spacer unit and a glycine Spacer unit. When Drug-linker or conjugate containing a glycine-glycine Spacer unit or a glycine Spacer unit undergoes enzymatic cleavage via a tumor-cell associated-protease, a cancer-cellassociated protease or a lymphocyte-associated protease, a glycine-glycine-Drug moiety or a glycine-Drug moiety is cleaved from L-Aa-Ww-. In some cases, an independent hydrolysis reaction takes place within the target cell, cleaving the glycine Drug moiety bond and liberating the Drug.

[0273] In some embodiments, -Yy- is a p-aminobenzyl alcohol (PAB) unit whose phenylene portion is substituted with Qm:wherein Q is selected from -C1-C8alkyl, -O-(C1-C8alkyl), halogen, nitro, and cyano; and m is an integer selected from 0 to 4.

[0274] In some embodiments, -Yy- is

[0275] In some embodiments, a non self-immolative Spacer unit (-Y-) is -Gly-Gly-. In some cases, a non self-immolative the Spacer unit (-Y-) is -Gly-.

[0276] In some embodiments, a Drug-Linker Compound or a Drug-Linker Ligand Conjugate is provided in which the Spacer unit is absent (y = 0), or a pharmaceutically acceptable salt or solvate thereof.

[0277] In some embodiments, a Drug-Linker or conjugate containing a self-immolative Spacer unit can release -D without the need for a separate hydrolysis step. In some cases, -Y- is a PAB group that is linked to -Ww- via the amino nitrogen atom of the PAB group, and connected directly to -D via a carbonate, carbamate or ether group:wherein Q is selected from -C1-C8alkyl, -O-(C1-C8alkyl), halogen, nitro, and cyano; m is an integer selected from 0 to 4; and p is from 1 to 20.

[0278] Other examples of self-immolative spacers include, but are not limited to, aromatic compounds that are electronically similar to the PAB group such as 2-aminoimidazol-5-methanol derivatives and ortho or para-aminobenzyl acetals. In some cases, the self-immolative spacer is para-aminobenzyl carbamate (PABC). Spacers can be used that undergo cyclization upon amide bond hydrolysis, such as substituted and unsubstituted 4-aminobutyric acid amides, appropriately substituted bicyclo[2.2.l] and bicyclo[2.2.2] ring systems, and 2-aminophenylpropionic acid amides. Elimination of amine-containing drugs that are substituted at the a-position of glycine are also examples of self-immolative spacer useful in a Drug-Linker or a conjugate.

[0279] In some embodiments, Spacer units (-Yy-) are represented by Formulas (X)-(XII):wherein Q is selected from -C1-C8alkyl, -O-(C1-C8alkyl), halogen, nitro, and cyano; m is an integer from 0 to 4;.

[0280] In some embodiments a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa, or Formula II, is represented by:,wherein w and y are each 0,and wherein each p is selected from 1 and about 20. In some cases, each p is selected from about 2 to about 8. In some cases, each p is selected from about 4. In some cases, each p is selected from about 2. In some cases, each p is selected from about 6. In some cases, each p is selected from about 8.

[0281] In some embodiments a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa, or Formula II, is represented by:In some cases, represented by:

[0282] In some embodiments, for a Drug-Linker of Formula I is represented by

[0283] In some embodiments a conjugate or salt of Formula Ia,,,,In some cases, Ab is selected from an anti-BCMA antibody, anti-HER2 antibody and anti-TROP2 antibody. In some cases, Ab is Sacituzumab. In some cases, Ab is Trastuzumab. In some cases, p is an integer from about 1 to about 8.

[0284] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, y is selected from 0, 1, and 2. In some cases, y is selected from 0 and 1. In some cases, y is selected from 1 and 2. In some cases, y is selected from 0 and 2. In some cases, y is 2. In some cases, y is 1. In some cases, y is 0.

[0285] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, each Y is independently a Spacer unit. In some cases Y is a Spacer unit. In some cases, Y isIn some cases, Y isand y is selected from 1 and 2. In some cases, Y isand y is 1.

[0286] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, y is selected from 0, 1, and 2. In some cases, y is selected from 0 and 1. In some cases, y is selected from 1 and 2. In some cases, y is selected from 0 and 2. In some cases, y is 2. In some cases, y is 1. In some cases, y is 0.

[0287] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, each Y is independently a Spacer unit. In some cases Y is a Spacer unit. In some cases, Y is. In some cases, Y isand y is selected from 1 and 2. In some cases, Y isand y is 1.

[0288] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, Y isTable AA. Examplary Conjugates

[0289] For Table AA, L is an antibody or antigen-binding portion thereof.In some embodiments, the exemplary conjugates of Table AA have a DAR of at most about 16. In some cases, the exemplary conjugates of Table AA have a DAR about 8. In some cases, the exemplary conjugates of Table AA have a DAR about 10. In some cases, the exemplary conjugates of Table AA have a DAR of at least about 1. In some cases, the exemplary conjugates of Table AA have a DAR at least about 2. In some cases, the exemplary conjugates of Table AA have a DAR at least about 4. In some cases, the exemplary conjugates of Table AA have a DAR at least about 8. In some cases, the exemplary conjugates of Table AA have a DAR at most about 8. In some cases, the exemplary conjugates of Table AA have a DAR from about 1 to about 16. In some cases, the exemplary conjugates of Table AA have a DAR from about 4 to about 12. In some cases, the exemplary conjugates of Table AA have a DAR from about 6 to about 10. In some cases, the exemplary conjugates of Table AA have a DAR from about 7 to about 9. In some cases, the exemplary conjugates of Table AA have a DAR from about 8 to about 10. In some cases, the exemplary conjugates of Table AA have a DAR from about 6 to about 8. In some embodiments, the antibody is selected from an anti-HER2 antibody and anti- TROP2 antibody. In some embodiments, the antibody is selected from Trastuzumab and Sacituzumab. In some embodiments, the antibody is Trastuzumab. In some embodiments, the antibody is Sacituzumab.

[0290] THE DRUG UNIT (Drug moiety)

[0291] In some embodiments, for a Drug-Linker or salt of Formula I, or a conjugate or salt of Formula Ia, Formula Ia’, Formula II, Formula IIa, D is selected from a Trichothecene. In some cases, D is selected from a Type A Trichothecene, a Type B Trichothecene, a Type C Trichothecene, and a Type D Trichothecene. In some cases, D is selected from a Type B Trichothecene, a Type C Trichothecene, and a Type D Trichothecene. In some cases, D is selected from a Type C Trichothecene and a Type D Trichothecene. In some cases, D is selectedfrom a Type A Trichothecene, a Type B Trichothecene, and a Type C Trichothecene. In some cases, D is selected from a Type A Trichothecene and a Type B Trichothecene. In some cases, D is selected from a Type D Trichothecene. In some cases, D is selected from a macrocyclic Trichothecene. In some cases, D is selected from a Roridin compound. In some cases, D is selected from Roridin A and Roridin E. In some cases, D is Roridin A. In some cases, D is Roridin E.

[0292] In some embodiments, for a conjugate or salt of Formula Ila, D is selected from a Trichothecene. In some cases, D is selected from a Type A Trichothecene, a Type B Trichothecene, a Type C Trichothecene, and a Type D Trichothecene. In some cases, D is selected from a Type B Trichothecene, a Type C Trichothecene, and a Type D Trichothecene. In some cases, D is selected from a Type C Trichothecene and a Type D Trichothecene. In some cases, D is selected from a Type A Trichothecene, a Type B Trichothecene, and a Type C Trichothecene. In some cases, D is selected from a Type A Trichothecene and a Type B Trichothecene. In some cases, D is selected from a Type D Trichothecene. In some cases, D is selected from a macrocyclic Trichothecene. In some cases, D is selected from a Roridin compound. In some cases, D is selected from Roridin A and Roridin E. In some cases, D is Roridin A. In some cases, D is Roridin E.

[0293] In some embodiments, for a conjugate or salt of Table 3, L is Ab, wherein Ab is an antibody or an antigen-binding portion thereof, In some cases, Ab is selected from an anti- BCMA antibody, anti-HER2 antibody and anti-TROP2 antibody. In some cases, Ab is selected from TNFRSF17, Sacituzumab, and Trastuzumab. In some cases, Ab is anti-BCMA antibody. In some cases, Ab is anti-HER2 antibody. In some cases, Ab is anti-TROP2 antibody. In some cases, Ab is TNFRSF17. In some cases, Ab is Sacituzumab. In some cases, Ab is Trastuzumab. In some cases, p is selected from about 1 to about 8. In some cases, p is about 8.

[0294] In some embodiments, for a Drug-Linker or salt of Formula I, or a conjugate or salt of Formula la, Formula la’, Formula II, Formula Ila, the Drug unit (D) is selected from a Trichothecene. In some cases, the Drug unit is a Roridin compound. In some cases the Drug unit is Roridin A. In some cases, the Drug unit is Roridin E. In some cases, the Drug unit is Roridin A. In some cases, the Drug unit is Roridin E. In some cases, the Drug unit is formed by removing a hydrogen atom of a drug (e.g., Roridin A or Roridine E), such that the Drug unit can form a bond to the rest of the antibody drug conjugate or drug-linker or linker unit, at the position of theremoved hydrogen atom. In some cases, the Drug unit is selected fromcases, the Drug unit is selected from, g In some cases, D is a Drug unit (moiety) having a nitrogen atom or oxygen atom that can form a bond with the Spacer unit when y = 1 or 2, with the C-terminal carboxyl group of an Amino Acid unit when y = 0, with the carboxyl group of a Stretcher unit when w and y = 0, and with the carboxyl group of a Drug unit when a, w, and y = 0. In some cases, D is a Drug unit (moiety) having an oxygen atom that can form a bond with the Spacer unit when y = 1 or 2, with the C-terminal carboxyl group of an Amino Acid unit when y = 0, with the carboxyl group of a Stretcher unit when w and y = 0, and with the carboxyl group of a Drug unit when a, w, and y = 0. In some cases, D is a Drug unit (moiety) having an oxygen atom that can form a bond with the Spacer unit when y = 1. It is to be understood that the terms "drug unit" and "drug moiety" are synonymous and used interchangeably herein.

[0295] In some embodiments, D is a Drug unit. In some cases, D comprises a Trichothecene. In some cases, the D comprises a Roridin compound. In some cases, D is a compound represented by the structure represented by the structure of Formula (IIIa):or a pharmaceutically acceptable salt thereof, wherein: E1is selected from hydrogen and an End unit; X1is absent or selected from -N(R1)-, -O-, and heterocycle; R1is selected from hydrogen and C1-6alkyl; and P is selected fromwherein R2is selected from hydrogen and -OR10; R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, - S(O)2R20, -P(O)(OR20)2, -Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, - N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0296] In some embodiments, for a compound or salt of Formula (IIIa), P is. In some cases, P is

[0297] In some embodiments, for a compound or salt of Formula (IIIa), the End unit is a moiety. In some cases, the moiety includes at least one heteroatom. In some cases, the heteroatom is selected from nitrogen, sulfur, and oxygen. In some cases, the heteroatom is nitrogen. In some cases, the moiety includes a carbonyl. In some cases, the moiety is capable of forming a bond . In some cases, the moiety is capable of forming a covalent bond.

[0298] In some embodiments, for a compound or salt of Formula (IIIa), X1is absent and E1is azide.

[0299] In some embodiments, for a compound or salt of Formula (IIIa), X1is a heterocycle. In some cases, X1is a 5- to 6-membered heterocycle. In some cases, X1is a 5- to 6-membered heteroaryl. In some cases, X1is a 5-membered heteroaryl. In some cases, X1is a 6-membered heteroaryl.

[0300] In some embodiments, for a compound or salt of Formula (IIIa), X1is selected from - N(R1)-, -O-, and triazole. In some cases, X1is is selected from -N(R1)- and -O-. In some cases, X1is selected from -N(R1)- and triazole. In some cases, X1is selected -O- and triazole. from In some cases, X1is -N(R1)-. In some cases, X1is -O-. In some cases, X1is triazole.

[0301] In some embodiments, for a compound or salt of Formula (IIIa), X1is selected from In some cases, X1is selected fromandIn some cases, X1isIn some cases, X1is. In some cases, X1is selected from

[0302] In some embodiments, for a compound or salt of Formula (IIIa), E1selected from: hydrogen, C1-10alkyl, C2-10alkenyl, C2-10alkynyl, -C(O)R30, -C(O)N(R30)2, -C(O)OR30, - S(O)2N(R30)2, -S(O)2OR30, -S(O)R30, -S(O)2R30, -P(O)(OR30)2, -Si(R30)3, - Si(R30)2(OR30), -Si(R30)2(OR30)2, and -Si(OR30)3, wherein one or more CH2units of the C1-10alkyl, C2-10alkenyl, C2-10alkynyl are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)N(R30)–, or –S(O)2–, and wherein the C1-10alkyl, C2-10alkenyl, and C2-10alkynyl are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, - C(O)R30, -C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, - S(O)2OR30, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, - NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0303] In some embodiments, for a compound or salt of Formula (IIIa), E1selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)– or –C(O)N(R30)–, andwherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), - C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), - C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0304] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)–, –C(O)O–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from F, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, C3-6carbocycle and 5- to 9-membered heterocycle, wherein the C3-6carbocycle and 5- to 9-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 7- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 7-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independentlyselected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

[0305] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)– or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from F, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, C3-6carbocycle and 5- to 9-membered heterocycle, wherein the C3-6carbocycle and 5- to 9-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 7- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 7-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

[0306] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)– or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from F, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, C3-6carbocycle and 5- to 9-membered heterocycle, wherein the C3-6carbocycle and 5- to 9-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, and 4- to 7-membered heterocycle, wherein the C1-8alkyl and 4- to 7-membered heterocycle are optionally substituted withone or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

[0307] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)– or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from F, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, C3-6carbocycle and 5- to 9-membered heterocycle, wherein the C3-6carbocycle and 5- to 9-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, and C1-6alkyl,; and each R30is independently selected from hydrogen, C1-8alkyl, and 4- to 7-membered heterocycle; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, C1-6alkyl, and C1-6haloalkyl.

[0308] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)–, –C(O)O–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from F, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, C3-6carbocycle and 5- to 9-membered heterocycle, wherein the C3-6carbocycle and 5- to 9-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, and C1-6alkyl,; and each R30is independently selected from hydrogen, C1-8alkyl, and 4- to 7-membered heterocycle; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, C1-6alkyl, and C1-6haloalkyl.

[0309] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from ,

[0310] In some embodiments, for a compound or salt of Formula (IIIa), wherein E1is selected from C1-10alkyl and -C(O)R30; wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O– or –C(O)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle areoptionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), - C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), - C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl.

[0311] In some embodiments, for a compound or salt of Formula (IIIa), wherein E1is selected from C1-10alkyl and -C(O)R30; wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O– or –C(O)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and - O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

[0312] In some embodiments, for a compound or salt of Formula (IIIa), wherein E1is selected from C1-10alkyl and -C(O)R30;wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O– or –C(O)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen and C1-8alkyl, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

[0313] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from

[0314] In some embodiments, for a compound or salt of Formula (Illa), E1is selected from C1-10alkyl and -C(O)R30, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by — C(O)-, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -C(O)R30; andR30is selected from C3-10carbocycle and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl.

[0315] In some embodiments, for a compound or salt of Formula (Illa), E1is selected from - C(O)R30; andR30is selected from C3 -10carbocycle and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, - NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and - O-C1-6alkyl. In some cases, E1is selected from -C(O)R30; andR30is selected from C3-10carbocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), - C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl. In some cases, E1is selected from -C(O)R30; andR30is selected 4- to 10-membered heterocycle, optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl. In some cases, E1is selected from -C(O)R30; andR30is selected 4- to 10-membered heterocycle, optionally substituted with one or more substituents independently selected from halogen, -OH, -NH2, -NH(C1-6aminoalkyl), -C(O)(C1-6aminoalkyl), and C1-6alkyl.

[0316] In some embodiments, for a compound or salt of Formula (Illa), E1is selected from.

[0317] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from selected from C1-10alkyl, -S(O)2OR30, -S(O)R30, -S(O)2N(R30)2, and -S(O)2R30, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –S(O)2–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

[0318] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from selected from C1-10alkyl, -S(O)2OR30, and -S(O)2N(R30)2, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –S(O)2–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -N(R30)2, -C(O)OR30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, - CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0319] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from

[0320] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from selected from selected from C1-10alkyl and -C(O)N(R30)2, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, and -N(R30)C(O)R30; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independentlyselected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0321] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from selected from selected from C1-10alkyl and -C(O)N(R30)2, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, and -N(R30)C(O)R30; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

[0322] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl and -C(O)N(R30)2, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, and -C(O)OR30; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0323] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl and -C(O)N(R30)2, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, and -C(O)OR30;each R30is independently selected from hydrogen and C1-8alkyl, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0324] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, and -C(O)OR30; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0325] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, and -C(O)OR30; each R30is independently selected from hydrogen, C1-8alkyl, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, - CN, -NH2, C1-6alkyl, and C1-6haloalkyl.

[0326] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, and -C(O)OR30; each R30is independently selected from hydrogen and C1-8alkyl.

[0327] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, andwherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, and -C(O)OR30; each R30is hydrogen.

[0328] In some embodiments, for a compound or salt of Formula (IIIa), E1is -C(O)N(R30)2, and each R30is independently selected from hydrogen, C1-8alkyl, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl. In some cases, E1is -C(O)N(R30)2, and each R30is independently selected from hydrogen, C1-8alkyl, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, - CN, -NH2, and C1-6alkyl. In some cases, E1is selected from.

[0329] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from.

[0330] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from - Si(R30)3, -Si(R30)2(OR30), -Si(R30)2(OR30)2, and -Si(OR30)3; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl. In some cases, E1is selected from - Si(R30)3, -Si(R30)2(OR30), -Si(R30)2(OR30)2, and -Si(OR30)3; and each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl. In some cases, E1is selected from -Si(R30)3and -Si(OR30)3; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, - CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl. In some cases, E1isselected from -Si(R30)3and -Si(OR30)3; and each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0331] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from - Si(R30)3; and each R30is independently selected from C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl. In some cases, each R30is independently selected from C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, and C1-6haloalkyl. In some cases, each R30is independently selected from C1-4alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, and C1-6haloalkyl. In some cases, each R30is independently selected from C1-4 alkyl. In some cases, each R30is independently selected from methyl and tert-butyl.

[0332] In some embodiments, for a compound or salt of Formula (IIIa), E1is

[0333] In some embodiments, for a compound or salt of Formula (IIIa), E1is hydrogen.

[0334] In some embodiments, for a compound or salt of Formula (IIIa), E1is selected from hydrogen,, , , , , ,

[0335] In some embodiments, for a compound or salt of Formula (Illa), E1is selected from, , , , In some cases, E1is selected from, , , , In so1me cases, E is selected from, , , ,

[0336] In some embodiments, for a compound or salt of Formula (IIIa), R2is selected from - OR10; wherein R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, - S(O)2R20, -P(O)(OR20)2, -Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, - N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0337] In some embodiments, for a compound or salt of Formula (IIIa), R2is selected from - OR10; wherein R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, - S(O)2OR20, -S(O)2R20, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0338] In some embodiments, for a compound or salt of Formula (IIIa), R2is selected from - OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -S(O)2N(R20)2, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, and 4- to 6-membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

[0339] In some embodiments, for a compound or salt of Formula (IIIa), R2is selected from

[0340] In some embodiments, for a compound or salt of Formula (IIIa), X1is selected from ,. In some cases, X1is selected from

[0341] In some embodiments, for a compound or salt of Formula (III-RA-a), Formula (III-RA- b), or Formula (III-RE), R2is selected from,

[0342] In some embodiments, for a compound or salt of Formula (IIIa), E1is as defined in Table 1A. In some cases, X1is as defined as in Table 1A. In some cases, R2is as defined in Table 1A. In some cases, E1is as defined in Table 1B. In some cases, X1is as defined as in Table 1B. In some cases, R2is as defined in Table 1B. In some cases, E1is as defined in Table 1A and Table 1B. In some cases, X1is as defined as in Table 1A and Table 1B. In some cases, E2is as defined in Table 1A and Table 1B.

[0343] In some embodiments, for a compound or salt of Formula (IIIa), E1; X1; and R2are as defined in Table 1A. In some cases, E1; X1; and R2are as defined in Table 1B. In some cases, E1; X1; and R2are as defined in Table 1A and Table 1B.

[0344] In some embodiments, for a compound or salt of Formula (IIIa), the compound is selected from Table 1A. In some cases, the compound is selected from Table 1B. In some cases, the compound is selected from Table 1A and Table 1B.

[0345] In some embodiments, for a compound or salt of Formula (IIIa), the compound is selected from compound PA-1 to compound PA-294 and compound PB-1.

[0346] THE LIGAND UNIT (L) / ANTIBODY (Ab)

[0347] In some embodiments, for a a conjugate or salt of Formula Ia or Formula II, includes a Ligand unit. In some cases, the Ligand unit is an antibody.

[0348] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, can further comprise a Ligand unit or Antibody.

[0349] The Ligand unit (L-) includes within its scope any unit of a Ligand (L) that binds or reactively associates or complexes with a receptor, antigen or other receptive moiety associated with a given target-cell population. A Ligand is a molecule that binds to, complexes with, or reacts with a moiety of a cell population sought to be therapeutically or otherwise biologically modified. In one aspect, the Ligand unit acts to deliver the Drug unit to the particular target cell population with which the Ligand unit reacts. Such Ligands include, but are not limited to, large molecular weight proteins such as, for example, full-length antibodies, antibody fragments, smaller molecular weight proteins, polypeptide or peptides, lectins, glycoproteins, non-peptides, vitamins, antigen binding portion, nutrient transport molecules (such as, but not limited to, transferrin), or any other cell binding molecule or substance. In some cases, the Ligand unit is selected from an antibody or antigen binding portion thereof. In some cases, the Ligand unit is selected from an antibody. In some cases, the Ligand unit is an antibody (Ab).

[0350] In some embodiments, for a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, the Drug-Linker is conjugated to an antibody (Ab) to form a conjugate, wherein Ab is attached to A, wherein A has reacted and formed a covalent bond to Ab.

[0351] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, Ab is selected from an anti-BCMA antibody, anti-HER2 antibody and anti-TROP2 antibody. In some cases, Ab is selected from TNFRSF17, Sacituzumab, and Trastuzumab. In some cases, Ab is anti-BCMA antibody. In some cases, Ab is anti-HER2 antibody. In some cases, Ab is anti- TROP2 antibody. In some cases, Ab is TNFRSF17. In some cases, Ab is Sacituzumab. In some cases, Ab is Trastuzumab.

[0352] In some embodiments, for a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, Ab is an antibody. In some cases, the Ab is trastuzumab.

[0353] In some embodiments, for a a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa or Formula II, the Ligand or Antibody can form a bond to a Stretcher unit, an Amino Acid unit, a Spacer Unit, or a Drug Unit. A Ligand unit can form a bond to a Linker unit via a heteroatom ofthe Ligand. Heteroatoms that may be present on a Ligand unit include sulfur (in some embodiments, from a sulfhydryl group of a Ligand), oxygen (in some embodiments, from a carbony1, carboxyl or hydroxyl group of a Ligand) and nitrogen (in some embodiments, from a primary or secondary amino group of a Ligand). These heteroatoms can be present on the Ligand in the Ligand's natural state, for example a naturally-occurring antibody, or can be introduced into the Ligand via chemical modification.

[0354] In some embodiments, for a a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa or Formula II, the Ligand or Antibody has a sulfhydryl group and the Ligand bonds to the Linker unit via the sulfhydryl group's sulfur atom.

[0355] In some embodiments, for a a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa or Formula II, the Ligand or Antibody has one or more lysine residues that can be chemically modified to introduce one or more sulfuydryl groups. The Ligand unit bonds to the Linker unit via the sulfhydryl group's sulfur atom. The reagents that can be used to modify lysines include, but are not limited to, N-succinimidyl S-acetylthioacetate (SATA) and 2-Iminothiolane hydrochloride (Traut's Reagent).

[0356] In some embodiments, for a a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa or Formula II, the Ligand or Antibody can have one or more carbohydrate groups that can be chemically modified to have one or more sulfuydryl groups. The Ligand unit bonds to the Linker Unit, such as the Stretcher Unit, via the sulfhydryl group's sulfur atom.

[0357] In some embodiments, for a a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa or Formula II, the Ligand or Antibody can have one or more carbohydrate groups that can be oxidized to provide an aldehyde (-CHO) group. The corresponding aldehyde can form a bond with a Reactive Site on a Stretcher. Reactive sites on a Stretcher that can react with a carbonyl group on a Ligand include, but are not limited to, hydrazine and hydroxylamine.

[0358] In some embodiments, for a a conjugate or salt of Formula Ia or Formula II, useful non- immunoreactive protein, polypeptide, or peptide Ligands include, but are not limited to, transferrin, epidermal growth factors ("EGF"), bombesin, gastrin, gastrin-releasing peptide, platelet-derived growth factor, IL-2, IL-6, transforming growth factors ("TGF'), such as TGF-α and TGF-α, vaccinia growth factor ("VGF'), insulin and insulin-like growth factors I and II, lectins and apoprotein from low density lipoprotein.

[0359] In some embodiments, for a conjugate or salt of Formula Ia, Formula Ia’, Formula IIa or Formula II, the Ligand or Antibody is a polyclonal antibody. In some cases, useful polyclonal antibodies are heterogeneous populations of antibody molecules derived from the sera of immunized animals. Various procedures well known in the art may be used for the production ofpolyclonal antibodies to an antigen-of-interest. For example, for the production of polyclonal antibodies, various host animals can be immunized by injection with an antigen of interest or derivative thereof, including but not limited to rabbits, mice, rats, and guinea pigs. Various adjuvants may be used to increase the immunological response, depending on the host species, and including but not limited to Freund's (complete and incomplete) adjuvant, mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, keyhole limpet hemocyanins, dinitrophenol, and potentially useful human adjuvants such as BCG (bacille Calmette-Guerin) and corynebacterium parvum. Such adjuvants are also well known in the art.

[0360] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, the Ligand or Antibody is a monoclonal antibody. In some cases, useful monoclonal antibodies are homogeneous populations of antibodies to a particular antigenic determinant (e.g., a cancer cell antigen, a viral antigen, a microbial antigen, a protein, a peptide, a carbohydrate, a chemical, nucleic acid, or fragments thereof). A monoclonal antibody (mAb) to an antigen-of- interest can be prepared by using any technique known in the art which provides for the production of antibody molecules by continuous cell lines in culture. These include, but are not limited to, the hybridoma technique, the human B cell hybridoma technique, and the EBV- hybridoma technique. Such antibodies may be of any immunoglobulin class including IgG, IgM, IgE, IgA, and IgD and any subclass thereof. The hybridoma producing the mAbs of use in this invention may be cultivated in vitro or in vivo. In some cases, useful monoclonal antibodies include, but are not limited to, human monoclonal antibodies, humanized monoclonal antibodies, antibody fragments, or chimeric human-mouse (or other species) monoclonal antibodies. Human monoclonal antibodies may be made by any of numerous techniques known in the art.

[0361] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, the Ligand or Antibody is a bispecific antibody. Methods for making bispecific antibodies are known in the art. Traditional production of full-length bispecific antibodies is based on the coexpression of two immunoglobulin heavy chain-light chain pairs, where the two chains have different specificities. Because of the random assortment of immunoglobulin heavy and light chains, these hybridomas (quadromas) can produce a potential mixture of 10 different antibody molecules, of which only one has the correct bispecific structure.

[0362] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, the antibody can be a functionally active fragment, derivative or analog of an antibody that immunospecifically binds to cancer cell antigens, viral antigens, or microbial antigens or other antibodies bound to tumor cells or matrix. In this regard, "functionally active"means that the fragment, derivative or analog is able to elicit anti-anti-idiotype antibodies that recognize the same antigen that the antibody from which the fragment, derivative or analog is derived recognized. Specifically, in an exemplary embodiment the antigenicity of the idiotype of the immunoglobulin molecule can be enhanced by deletion of framework and CDR sequences that are C-terminal to the CDR sequence that specifically recognizes the antigen. To determine which CDR sequences bind the antigen, synthetic peptides containing the CDR sequences can be used in binding assays with the antigen by any binding assay method known in the art.

[0363] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, other useful antibodies include fragments of antibodies such as, but not limited to, F(ab')2fragments, which contain the variable region, the light chain constant region and the CH1 domain of the heavy chain can be produced by pepsin digestion of the antibody molecule, and Fab fragments, which can be generated by reducing the disulfide bridges of the F(ab')2fragments. Other useful antibodies are heavy chain and light chain dimers of antibodies, or any minimal fragment thereof such as Fvs or single chain antibodies (SCAs), or any other molecule with the same specificity as the antibody.

[0364] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, the Ligand or Antibody is a recombinant antibody. In some cases, recombinant antibodies, such as chimeric and humanized monoclonal antibodies, comprising both human and non-human portions, which can be made using standard recombinant DNA techniques, are useful antibodies. A chimeric antibody is a molecule in which different portions are derived from different animal species, such as those having a variable region derived from a murine monoclonal and human immunoglobulin constant regions. Humanized antibodies are antibody molecules from nonhuman species having one or more complementarity determining regions (CDRs) from the non-human species and a framework region from a human immunoglobulin molecule. Such chimeric and humanized monoclonal antibodies can be produced by recombinant DNA techniques known in the art.

[0365] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, the Ligand or Antibody is a human antibody. In some case, completely human antibodies are particularly desirable and can be produced using transgenic mice that are incapable of expressing endogenous immunoglobulin heavy and light chains genes, but which can express human heavy and light chain genes. The transgenic mice are immunized in the normal fashion with a selected antigen, e.g., all or a portion of a polypeptide of the invention. Monoclonal antibodies directed against the antigen can be obtained using conventional hybridoma technology. The human immunoglobulin transgenes harbored by the transgenic micerearrange during B cell differentiation, and subsequently undergo class switching and somatic mutation. Thus, using such a technique, it is possible to produce therapeutically useful IgG, IgA, IgM, and IgE antibodies. In some cases, completely human antibodies that recognize a selected epitope can be generated using a technique referred to as "guided selection." In this approach a selected non-human monoclonal antibody, e.g., a mouse antibody, is used to guide the selection of a completely human antibody recognizing the same epitope. Human antibodies can also be produced using various techniques known in the art, including phage display libraries.

[0366] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, the Ligand or Antibody is is a fusion protein of an antibody, or a functionally active fragment thereof, for example in which the antibody is fused via a covalent bond (e.g., a peptide bond), at either the N-terminus or the C-terminus to an amino acid sequence of another protein (or portion thereof, preferably at least 10, 20, or 50 amino acid portion of the protein) that is not the antibody. Preferably, the antibody or fragment thereof is covalently linked to the other protein at the N-terminus of the constant domain.

[0367] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, antibodies include analogs and derivatives that are either modified, i.e, by the covalent attachment of any type of molecule as long as such covalent attachment permits the antibody to retain its antigen binding immunospecificity. For example, but not by way of limitation, the derivatives and analogs of the antibodies include those that have been further modified, e.g., by glycosylation, acetylation, pegylation, phosphorylation, amidation, derivatization by known protecting / blocking groups, proteolytic cleavage, linkage to a cellular antibody unit or other protein, etc. Any of numerous chemical modifications can be carried out by known techniques, including, but not limited to specific chemical cleavage, acetylation, formylation, metabolic synthesis inthe presence of tunicamycin, etc. Additionally, the analog or derivative can contain one or more unnatural amino acids.

[0368] In some embodiments, for a conjugate or salt of Formula la, Formula la’, Formula Ila or Formula II, the antibodies include antibodies having modifications (e.g., substitutions, deletions or additions) in amino acid residues that interact with Fc receptors. In particular, antibodies include antibodies having modifications in amino acid residues identified as involved in the interaction between the anti-Fc domain and the FcRn receptor. Antibodies immunospecific for a cancer cell antigen can be obtained commercially, for example, from Genentech (San Francisco, CA) or produced by any method known to one of skill in the art such as, e.g., chemical synthesis or recombinant expression techniques. The nucleotide sequence encoding antibodiesimmunospecific for a cancer cell antigen can be obtained, e.g., from the GenBank database or a database like it, the literature publications, or by routine cloning and sequencing. PRODUCTION OF RECOMBINANT ANTIBODIES / ANTIBODIES

[0369] Antibodies of the invention (e.g., Recombinant antibodies, Polyclonal antibodies, Monoclonal antibodies, Humanized antibodies, Human antibodies, Antibody fragments, Bispecific antibodies) can be produced using any method known in the art to be useful for the synthesis of antibodies. PHARMACEUTICAL FORMULATIONS

[0370] A Drug-Linker or salt thereof, or a conjugate or salt, or a compound or salt thereof thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, Formula IIa, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, Formula IIIa) may be formulated in any suitable pharmaceutical formulation. A pharmaceutical formulation of the present disclosure typically contains an active ingredient (e.g., Drug-linkers or Conjugates of Formulas described herein) and one or more pharmaceutically acceptable excipients or carriers, including but not limited to: inert solid diluents and fillers, diluents, sterile aqueous solution and various organic solvents, permeation enhancers, antioxidents, solubilizers, and adjuvants.

[0371] In certain embodiments, a Drug-Linker or salt thereof, a conjugate or salt thereof, or a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, Formula IIa, Formula II- RA-a, Formula II-RA-b, or Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II- RE*, Formula IIIa) is formulated with a pH modifying agent to maintain a pH of about 4 to about 6. Acceptable pH modifying agents include, but are not limited to citric acid, sodium citrate, dilute HCl, and other mild acids or bases capable of buffering a solution containing a compound or a salt of the discloure to a pH in the range of about 4 to about 6.

[0372] In certain embodiments, a Drug-Linker or salt thereof, a conjugate or salt thereof, or a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, Formula IIa, Formula II- RA-a, Formula II-RA-b, or Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II- RE*, Formula IIIa) is formulated with a chelating agent or other material capable of bindingmetal ions, such as ethylene diamine tetra acetic acid (EDTA) and its salts are capable of enhancing the stability of a compound or salt of any one of the Formulas described herein.

[0373] Pharmaceutical formulations may be provided in any suitable form, which may depend on the route of administration. In some embodiments, the pharmaceutical composition disclosed herein can be formulated in dosage form for administration to a subject. In some embodiments, the pharmaceutical composition is formulated for oral, intravenous, intraarterial, aerosol, parenteral, buccal, topical, transdermal, rectal, intramuscular, subcutaneous, intraosseous, intranasal, intrapulmonary, transmucosal, inhalation, and / or intraperitoneal administration. In some embodiments, the dosage form is formulated for oral administration. For example, the pharmaceutical composition can be formulated in the form of a pill, a tablet, a capsule, an inhaler, a liquid suspension, a liquid emulsion, a gel, or a powder. In some embodiments, the pharmaceutical composition can be formulated as a unit dosage in liquid, gel, semi-liquid, semisolid, or solid form.

[0374] It will be recognized by one of skill in the art that the optimal quantity and spacing of individual dosages of a Drug-Linker or salt thereof, a conjugate or salt thereof, or a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula LRA-b, or Formula I- RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, Formula Ila, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, or Formula Illa) described herein will be determined by the nature and extent of the condition being treated, the form, route and site of administration, and the age and condition of the particular subject being treated, and that a physician will ultimately determine appropriate dosages to be used. This dosage may be repeated as often as appropriate. If side effects develop the amount and / or frequency of the dosage can be altered or reduced, in accordance with normal clinical practice.

[0375] In some embodiments, the disclosure provides a pharmaceutical composition for oral administration containing at least one Drug-Linker or salt thereof, a conjugate or salt thereof, or a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, Formula Ila, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II- RE*, or Formula Illa) and a pharmaceutical excipient suitable for oral administration. The composition may be in the form of a solid, liquid, gel, semi-liquid, or semi-solid. In some embodiments, the composition further comprises a second agent.

[0376] Pharmaceutical compositions of the disclosure suitable for oral administration can be presented as discrete dosage forms, such as hard or soft capsules, cachets, troches, lozenges, ortablets, or liquids or aerosol sprays each containing a predetermined amount of an active ingredient as a powder or in granules, a solution, or a suspension in an aqueous or non-aqueous liquid, an oil-in-water emulsion, or a water-in-oil liquid emulsion, or dispersible powders or granules, or syrups or elixirs. Such dosage forms can be prepared by any of the methods of pharmacy, which typically include the step of bringing the active ingredient(s) into association with the carrier. In general, the composition are prepared by uniformly and intimately admixing the active ingredient(s) with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product into the desired presentation. For example, a tablet can be prepared by compression or molding, optionally with one or more accessory ingredients. Compressed tablets can be prepared by compressing in a suitable machine the active ingredient(s) in a free-flowing form such as powder or granules, optionally mixed with an excipient such as, but not limited to, a binder, a lubricant, an inert diluent, and / or a surface active or dispersing agent. Molded tablets can be made by molding in a suitable machine a mixture of the powdered compound or salt of any one of the Formulas or sub Formulas described herein moistened with an inert liquid diluent.

[0377] In some embodiments, the disclosure provides a pharmaceutical composition for injection containing a Drug-Linker or salt thereof, a conjugate or salt thereof, or a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, or Formula IIIa) and a pharmaceutical excipient suitable for injection. Components and amounts of agents in the composition are as described herein.

[0378] In certain embodiments, a Drug-Linker or salt thereof, a conjugate or salt, or a compound or salt thereof thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, Formula IIa, Formula II- RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, Formula IIIa) may be formulated for injection as aqueous or oil suspensions, emulsions, with sesame oil, corn oil, cottonseed oil, or peanut oil, as well as elixirs, mannitol, dextrose, or a sterile aqueous solution, and similar pharmaceutical vehicles.

[0379] Aqueous solutions in saline are also conventionally used for injection. Ethanol, glycerol, propylene glycol, liquid polyethylene glycol, and the like (and suitable mixtures thereof), cyclodextrin derivatives, and vegetable oils may also be employed. The proper fluidity can be maintained, for example, by the use of a coating, such as lecithin, for the maintenance of the required particle size in the case of dispersion and by the use of surfactants. The prevention ofthe action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like.

[0380] Pharmaceutical compositions may also be prepared from a Drug-Linker or salt thereof, a conjugate or salt thereof, or a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, Formula I-RE*, Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II- RA-a*, Formula II-RA-b*, Formula II-RE*, Formula IIIa) and one or more pharmaceutically acceptable excipients suitable for transdermal, inhalative, sublingual, buccal, rectal, intraosseous, intraocular, intranasal, epidural, or intraspinal administration. Preparations for such pharmaceutical composition are well-known in the art. See, e.g., Anderson, Philip O.; Knoben, James E.; Troutman, William G, eds., Handbook of Clinical Drug Data, Tenth Edition, McGraw- Hill, 2002; Pratt and Taylor, eds., Principles of Drug Action, Third Edition, Churchill Livingston, New York, 1990; Katzung, ed., Basic and Clinical Pharmacology, Ninth Edition, McGraw Hill, 2003; Goodman and Gilman, eds., The Pharmacological Basis of Therapeutics, Tenth Edition, McGraw Hill, 2001; Remingtons Pharmaceutical Sciences, 20th Ed., Lippincott Williams & Wilkins., 2000; Martindale, The Extra Pharmacopoeia, Thirty-Second Edition (The Pharmaceutical Press, London, 1999).

[0381] The disclosure also provides kits. The kits may include a Drug-Linker or salt thereof, a conjugate or salt thereof, a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, Formula I-RE*, Formula IIa, Formula II-RA-a, Formula II-RA-b, or Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, or Formula IIIa) and one or more additional agents in suitable packaging with written material that can include instructions for use, discussion of clinical studies, listing of side effects, and the like. Such kits may also include information, such as scientific literature references, package insert materials, clinical trial results, and / or summaries of these and the like, which indicate or establish the activities and / or advantages of the composition, and / or which describe dosing, administration, side effects, drug interactions, or other information useful to the health care provider. Such information may be based on the results of various studies, for example, studies using experimental animals involving in vivo models and studies based on human clinical trials. The kit may further contain another agent. In some embodiments, a Drug-Linker or salt thereof, a conjugate or salt thereof, a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, Formula I-RE*, Formula IIa, Formula II-RA-a, Formula II- RA-b, or Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, or FormulaIIIa) and the agent are provided as separate compositions in separate containers within the kit. In some embodiments, a Drug-Linker or salt thereof, a conjugate or salt thereof, a compound or salt thereof described herein (e.g., Formula I, Formula I-RA-a, Formula I-RA-b, or Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, Formula I-RE*, Formula IIa, Formula II-RA-a, Formula II- RA-b, or Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, or Formula IIIa) and the agent are provided as a single composition within a container in the kit. Suitable packaging and additional articles for use (e.g., measuring cup for liquid preparations, foil wrapping to minimize exposure to air, and the like) are known in the art and may be included in the kit. Kits described herein can be provided, marketed and / or promoted to health providers, including physicians, nurses, pharmacists, formulary officials, and the like. Kits may also, in some embodiments, be marketed directly to the consumer. Therapeutic Applications

[0382] In an aspect, the present disclosure provides a method of treating a disease, disorder, or condition in a subject in need thereof, comprising administering to the subject a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, (when further comprising a Ligand) , a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, Formula II-RE*, or a compound or salt of Formula IIIa.

[0383] In an aspect, the disclosure provides a pharmaceutical composition comprising a Drug- Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, (when further comprising a Ligand), a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II- RA-b*, or Formula II-RE*, or a compound or salt of Formula IIIa, and a pharmaceutically acceptable excipient.

[0384] In an aspect, the disclosure provides a method of treating a disease or disorder, comprising administering to a subject in need thereof a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA-b*, or Formula I-RE*, (when further comprising a Ligand), a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II- RE*, or a compound or salt of Formula IIIa, or a pharmaceutical composition comprising a Drug-Linker or salt Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA- a*, Formula I-RA-b*, or Formula I-RE*, (when further comprising a Ligand), a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, FormulaII-RA-b*, or Formula II-RE*, or a compound or salt of Formula IIIa, and a pharmaceutically acceptable excipient. In some cases, the disease, disorder, or condition is cancer.

[0385] In some aspects, the present disclosure provides a method of treating a disease or disorder. The methods comprises administering a conjugate or salt thereof disclosed herein or a pharmaceutical composition comprising a conjugate or salt disclosed herein and a pharmacueticaly acceptable salt, to a subject in need thereof. The disease or disorder is cancer. The disease or disorder is a tumor.

[0386] In some cases, a pharmaceutical composition comprising a Drug-Linker or salt of Formula I, Formula I-RA-a, Formula I-RA-b, Formula I-RE, Formula I-RA-a*, Formula I-RA- b*, or Formula I-RE*, (when further comprising a Ligand) , a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II-RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*, or a compound or salt of Formula IIIa, and a pharmaceutically acceptable excipient is admistered to a subject in need thereof for the treatment of a disease or disorder described herein.

[0387] In some aspects, the present disclosure provides a method of treating a disease or disorder , wherein the method comprises administering to a subject in need thereof a conjugate described herein (e.g., a conjugate or salt of Formula IIa, Formula II-RA-a, Formula II-RA-b, Formula II- RE, Formula II-RA-a*, Formula II-RA-b*, or Formula II-RE*), or a compound or salt of Formula IIIa.

[0388] In some embodiments, conjugates described herein can be used for treating diseases such as, but not limited to, hyperproliferative diseases, including: cancers of the head and neck which include tumors of the head, neck, nasal cavity, paranasal sinuses, nasopharynx, oral cavity, oropharynx, larynx, hypopharynx, salivary glands, and paragangliomas; cancers of the liver and biliary tree, particularly hepatocellular carcinoma; intestinal cancers, particularly colorectal cancer; ovarian cancer; small cell and non-small cell lung cancer (SCLC and NSCLC); breast cancer sarcomas, such as fibrosarcoma, malignant fibrous histiocytoma, embryonal rhabdomyosarcoma, leiomysosarcoma, neurofibrosarcoma, osteosarcoma, synovial sarcoma, liposarcoma, and alveolar soft part sarcoma; leukemias such as acute promyelocytic leukemia (APL), acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic myelogenous leukemia (CML); neoplasms of the central nervous systems, particularly brain cancer; multiple myeloma (MM), lymphomas such as Hodgkin's lymphoma, lymphoplasmacytoid lymphoma, follicular lymphoma, mucosa-associated lymphoid tissue lymphoma, mantle cell lymphoma, B-lineage large cell lymphoma, Burkitt's lymphoma, and T- cell anaplastic large cell lymphoma. Clinically, practice of the methods and use of compositionsdescribed herein will result in a reduction in the size or number of the cancerous growth and / or a reduction in associated symptoms (where applicable). Pathologically, practice of the method and use of compositions described herein will produce a pathologically relevant response, such as: inhibition of cancer cell proliferation, reduction in the size of the cancer or tumor, prevention of further metastasis, and inhibition of tumor angiogenesis. The method of treating such diseases comprises administering a therapeutically effective amount of an inventive combination to a subject. The method may be repeated as necessary. The cancer can be renal, lung, gastric, or ovarian cancer.

[0389] In some embodiments, the treatment of tumor-bearing subjects inhibits tumor growth by at least about 20%, more preferably by at least about 40%, even more preferably by at least about 60%, and still more preferably by at least about 80% relative to untreated subjects. A therapeutically effective amount of a therapeutic compound can decrease tumor size, or otherwise ameliorate symptoms in a subject, which is typically a human but can be another mammal.

[0390] The compositions and methods of the present disclosure can be useful for a plurality of different subjects including, but are not limited to, a mammal, human, non-human mammal, a domesticated animal (e.g., laboratory animals, household pets, or livestock), non-domesticated animal (e.g., wildlife), dog, cat, rodent, mouse, hamster, cow, bird, chicken, fish, pig, horse, goat, sheep, rabbit, and any combination thereof.Kits

[0391] In some aspects, the present disclosure provides a kit comprising a compound (e.g., a conjugate) or salt disclosed herein and instructions. In some cases, the compound is a conjugate.

[0392] In some aspects, the present disclosure provides a kit comprising a pharmaceutical composition comprising the compound or salt disclosed herein and instructions.

[0393] In certain aspects, the present disclosure provides a kit comprising a compound, salt or pharmaceutical composition disclosed herein and instructions for administering the compound, salt or pharmaceutical composition disclosed form to a subject in need thereof. In some embodiments, the kit comprises a compound, salt or pharmaceutical composition disclosed herein, packaged in a low moisture vapor transmission container with a desiccant. Optionally, a label is on or associated with the container. For example, a label is on a container when letters, numbers or other characters forming the label are attached, molded or etched on the container itself, and a label is associated with a container when it is present within a receptacle or carrier, such as a box, that also holds the container, e.g., as a package insert. In addition, a label may beused to indicate that the contents are to be used for a specific therapeutic application. In some embodiments, the label includes directions for use of the contents, such as in the methods described herein. In some embodiments, a compound, salt or pharmaceutical composition disclosed herein is presented in a pack or container that contains one or more unit dosage forms comprising the compound, salt or pharmaceutical composition disclosed herein. The pack may contain metal or plastic foil, such as a blister pack. The pack or container may be accompanied by instructions for administration of the unit dosage form. In some embodiments, the pack or container is accompanied with a notice in a form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals, which notice is reflective of approval by the agency of the form of the drug for human or veterinary administration. Such notice, for example, may be the labeling approved by the U.S. Food and Drug Administration for prescription of drugs, or the approved product insert. In some embodiments, compositions comprising the compound, salt or pharmaceutical composition disclosed herein are prepared, placed in an appropriate container, and labeled for treatment of an indicated condition.Preparation of Compounds

[0394] The compounds (e.g., Linkers, Drug-Linkers or conjugates) of the present disclosure can generally be prepared in a number of ways well known to those skilled in the art of organic synthesis and / or antibody drug conjugation. By way of example, compounds of the present disclosure can be synthesized using the methods described herein, together with synthetic methods known in the art of synthetic organic chemistry, or variations thereof as appreciated by those skilled in the art.

[0395] In some embodiments, a Drug-Linker or conjugate can be made using known methods. In some cases, a Drug-Linker or conjugate can be conveniently prepared using a Linker having a reactive site for binding to the Drug and Ligand. In one aspect, a Linker has a reactive site which has an electrophilic group that is reactive to a nucleophilic group present on a Ligand, such as but not limited to an antibody. Useful nucleophilic groups on an antibody include but are not limited to, sulfhydryl, hydroxyl and amino groups. The heteroatom of the nucleophilic group of an antibody is reactive to an electrophilic group on a Linker and forms a covalent bond to a Linker unit. Useful electrophilic groups include, but are not limited to, maleimide and haloacetamide groups. The electrophilic group provides a convenient site for antibody attachment.

[0396] In some embodiments, a Linker has a reactive site which has a nucleophilic group that is reactive to an electrophilic group present on an antibody. Useful electrophilic groups on anantibody include, but are not limited to, aldehyde and ketone carbonyl groups. The heteroatom of a nucleophilic group of a Linker can react with an electrophilic group on an antibody and form a covalent bond to an antibody unit. Useful nucleophilic groups on a Linker include, but are not limited to, hydrazide, oxime, amino, hydrazine, thiosemicarbazone, hydrazine carboxylate, and arylhydrazide. The electrophilic group on an antibody provides a convenient site for attachment to a Linker.

[0397] Carboxylic acid functional groups and chloroformate functional groups are also useful reactive sites for a Linker because they can react with secondary amino groups of a Drug to form an amide linkage. Also useful as a reactive site is a carbonate functional group on a Linker, such as but not limited to p-nitrophenyl carbonate, which can react with an amino group of a Drug, such as but not limited to N-methyl valine, to form a carbamate linkage. Typically, peptide- based Drugs can be prepared by forming a peptide bond between two or more amino acids and / or peptide fragments. Such peptide bonds can be prepared, for example, according to the liquid phase synthesis method.

[0398] The synthesis of an illustrative Stretcher described herein having an electrophilic maleimide group can be synthesized using known methods.

[0399] Exemplary Conjugates can be conveniently prepared using a Linker having two or more Reactive Sites for binding to the Drug and a Ligand. In one aspect, a Linker has a Reactive site which has an electrophilic group that is reactive to a nucleophilic group present on a Ligand, such as an antibody. Useful nucleophilic groups on an antibody include but are not limited to, sulfhydryl, hydroxyl and amino groups. The heteroatom of the nucleophilic group of an antibody is reactive to an electrophilic group on a Linker and forms a covalent bond to a Linker unit. Useful electrophilic groups include, but are not limited to, maleimide and haloacetamide groups. The electrophilic group provides a convenient site for antibody attachment.

[0400] In some embodiments, a Linker has a Reactive site which has a nucleophilic group that is reactive to an electrophilic group present on a Ligand, such as an antibody. Useful electrophilic groups on an antibody include, but are not limited to, aldehyde and ketone carbonyl groups. The heteroatom of a nucleophilic group of a Linker can react with an electrophilic group on an antibody and form a covalent bond to an antibody unit. Useful nucleophilic groups on a Linker include, but are not limited to, hydrazide, oxime, amino, hydrazine, thiosemicarbazone, hydrazine carboxylate, and arylhydrazide. The electrophilic group on an antibody provides a convenient site for attachment to a Linker.Drug Moiety Synthesis

[0401] Typically, peptide-based Drugs can be prepared by forming a peptide bond between two or more amino acids and / or peptide fragments. Such peptide bonds can be prepared, for example, according to the liquid phase synthesis method that is well known in the field of peptide chemistry.

[0402] In some embodiments, a Drug is prepared by combining about a stoichiometric equivalent of a dipeptide and a tripeptide, preferably in a one-pot reaction under suitable condensation conditions. EXAMPLES

[0403] The following examples are offered to illustrate, but not to limit the claimed invention. It will be recognized that these preparation methods are illustrative and not limiting. Using the teaching provided herein, numerous other methods of producing the compounds described herein will be available to one of skill in the art. Materials and general analytical methods

[0404] All solvents and reagents purchased are commercially available and used without further purification. All reactions were carried out under an atmosphere of nitrogen with magnetic stirring. Column chromatography was performed on Silicycle Inc. silica gel (100-200 mesh). Thin layer chromatography was performed on Silicycle Inc.0.25 mm silica gel plates. Visualization was accomplished with UV light (254 nm), I2, phosphomolybdic acid and KMnO4.

[0405] 1H NMR spectra was obtained in CDCl3, DMSO or MeOD at ambient temperature and chemical shifts are expressed in parts per million (δ, ppm). Proton chemical shifts are referenced to 7.26 ppm (CHCl3), 2.5 ppm (DMSO), 3.31 ppm (MeOD). Data reporting uses the following abbreviations: s, singlet; bs, broad singlet; d, doublet; t, triplet; m, multiplet; and J, coupling constant in Hz. Example 0: Drug / Payload Syntheses

[0406] General procedure A: amide coupling using HATU

[0407] Amine (1.0 equiv) and Boc- or Fmoc- protected amino acid (1.0 equiv) were dissolved in DMF. The solution was charged with N-ethyldiisopropylamine (1.1 equiv) then HATU (1.0 equiv). The reaction was stirred at ambient temperature until full conversion was observed by LCMS (254 nm). The reaction was diluted with ethyl acetate, washed with 1 N HCl (aq), satd. NaHCO3(aq) (2 mL) and brine. The organic layer was dried over sodium sulfate, filtered, and concentrated in vacuo. The crude material was used without further purification.

[0408] Carboxylic acid (1.0 equiv) and Boc- or Fmoc- protected amine (1.0 equiv) were dissolved in DMF. The solution was charged with N-ethyldiisopropylamine (1.1 equiv) then HATU (1.0 equiv). The reaction was stirred at ambient temperature until full conversion was observed by LCMS (254 nm). The reaction was diluted with ethyl acetate, washed with 1 N HCl (aq), satd. NaHCO3(aq) (2 mL) and brine. The organic layer was dried over sodium sulfate, filtered, and concentrated in vacuo. The crude material was used without further purification.

[0409] General procedure B: Fmoc deprotection

[0410] The crude (1.0 equiv) was dissolved in acetonitrile and charged with piperidine (1.0 equiv) at ambient temperature. The reaction was stirred overnight at ambient temperature. The reaction was concentrated in vacuo then passed through a silica plug using 1:1 ethyl acetate:hexanes then methanol. The methanol fraction was concentrated in vacuo and the residue was purified by prep-HPLC to yield the desired product as a solid.

[0411] General procedure C: Boc deprotection using hexafluoroisopropanol (HFIP)

[0412] A vial equipped with a stir bar was charged with Boc protected compound and an acid such as HFIP and placed in a flask and heated either with a hot plate or microwave reactor for 4 h at 120 °C. The reaction was concentrated in vacuo, and the crude was purified by prep HPLC to afford the desired product as a solid.

[0413] General procedure D: Boc deprotection using hot silica

[0414] The Boc protected compound was loaded onto silica with DCM and concentrated under reduced pressure. The reaction mixture was heated to 95 °C in open air for 24 h. The reaction was cooled down, extracted with DCM, filtered and concentrated under reduced pressure. The crude material was purified by prep HPLC to afford the desired product as a solid.

[0415] General procedure E: sulfonamide formation

[0416] To a solution of an amine (1.0 equiv) and sulfonyl chloride (2.0 equiv) in acetonitrile (0.8-1.2 mM) at ambient temperature was added N-ethyldiisopropylamine (2.0 eq.) and the resulting reaction mixture was stirred until complete reaction as monitored by LCMS. The reaction was concentrated under reduced pressure, dissolved in minimal amounts of DCM, and purified by ISCO column chromatography (hexanes -> ethyl acetate) affording the desired product.

[0417] General procedure F: sulfamide formation

[0418] To a solution of an amine (1.0 equiv) and sodium bicarbonate (8.0 equiv) in acetonitrile at ambient temperature was added sulfamyl chloride (2.0 equiv) and the resulting reaction mixture was stirred at 60 °C for 16 h. The reaction was filtered, washed with DCM and concentrated under reduced pressure. The crude was purified by flash column chromatography (hexanes -> ethyl acetate) to afford the desired product.

[0419] General procedure G: alkylation of C13’ hydroxyl

[0420] To a solution of an alcohol (1.0 equiv) in tetrahydrofuran at ambient temperature was added disilver oxide (4.0 equiv) followed by an electrophile such as alkyl halide (8.0 equiv) and the resulting reaction mixture was stirred at 55 °C in a sealed vial for 4 h and then at ambient temperature for 12 h. Then, sodium hydride 60%w / w (4.0 equiv) was added and the reaction was stirred for additional 1-5 h. The reaction was then directly purified by flash column chromatography (hexanes -> ethyl acetate) to afford the desired product.

[0421] General Procedure H: TBS deprotection using TBAF

[0422] A vial equipped with a stir bar was charged with TBS-protected compound in DMF and TBAF was added. The reaction was stirred at ambient temperature until completion as indicated by LCMS). The reaction was concentrated in vacuo and purified by flash column chromatography to afford the desired product.

[0423] General Procedure I: TBS deprotection using HF*pyridine

[0424] In a plastic Eppendorf tube, TBS-protected compound (1.0 equiv) in THF was cooled to 0 °C. The solution was charged with HF*pyridine (30 equiv) and stirred at 0 °C for 15 min. The reaction was removed from the ice bath and allowed to warm up to ambient temperature over 1.5 h. The reaction mixture was cooled to 0 °C and quenched with methoxytrimethylsilane (25 equiv) and left to stir for 10 min. The reaction was diluted with ethyl acetate, washed with 1M HCl, satd. NaHCO3, brine, dried over Na2SO4, filtered and concentrated in vacuo. The crude was purified by prep HPLC to afford the desired product.

[0425] General procedure J: amide coupling using DIC

[0426] Amine, carboxylic acid (1.0 equiv), and HOAt (0.2 equiv) were dissolved in DCM. The reaction was charged with DIC (1.0 equiv) and stirred at ambient temperature for 2 h. The reaction was concentrated in vacuo then dissolved in ethyl acetate. The solution was washed with 1 N HCl(aq), sat. NaHCO3(aq), then brine. The organic layer was dried over sodium sulfate, filtered, and concentrated in vacuo. The crude material was used without further purification.

[0427] General procedure K: Alkylation of C2’-OH

[0428] To a solution of TBS ether (1.0 equiv) in dry tetrahydrofuran (20 mL) was added sodium hydride 60%w / w (1.1 equiv) at 0 °C. The mixture was warmed to ambient temperature and stirred for 10 minutes. Electrophile (1.1 equiv) was added and stirred continued for 30 minutes. The mixture was then quenched with acetic acid (2 equiv) at 0 °C. The resultant reaction mixture was concentrated then purified by HPLC.

[0429] General procedure L: amide coupling using DIC no protecting group

[0430] Amine (1.0 equiv), carboxylic acid (1.1 equiv), and DMAP (0.1 equiv) were dissolved in DCM. The reaction was then charged with DIC (1.0 equiv) and stirred at ambient temperature for 2 h. The reaction was concentrated in vacuo then dissolved in ethyl acetate. The solution was washed with 1 N HCl(aq), sat. NaHCO3(aq), then brine. The organic layer was dried over sodium sulfate, filtered, and concentrated in vacuo. The crude material was used without further purification for subsequent steps or HPLC for final products.

[0431] General procedure M: Carbonate formation Step 1:

[0432] To a solution of an alcohol (1.0 equiv) in DCM at ambient temperature was added p- nitrobenzenyl chloroformate (3.5 equiv) followed by N,N-dimethyl-4-pyridylamine (1.0 equiv) and N-ethyldiisopropylamine (7.0 equiv) and the resulting reaction mixture was stirred at ambient temperature for 16 h. The reaction was then concentrated under reduced pressure and purified by flash column chromatography (hexanes -> ethyl acetate) to afford the desired product. Step 2:

[0433] To a solution of a p-nitrobenzenecarbonate (1.0 equiv) in dimethylformamide and pyridine (4:1 mixture) at ambient temperature were added an alcohol alcohol (10 equiv), HOAt(0.2 equiv), N-ethyldiisopropylamine (3 equiv), and N,N-dimethyl-4-pyridylamine (2 equiv) and the resulting reaction mixture was stirred at 50 °C for 2 h. The reaction was diluted with a minimal amount of MeCN and purified by semi-prep HPLC (water / MeCN 80:20 -> 5:95 +0.1% FA) affording the desired product.

[0434] General procedure N: cathepsin cleavable linker carbamate formationAmine (1 equiv), carbonate (1 equiv), and 4-methylmorpholine (3 equiv) were dissolved in dimethylformamide (0.2 mL, 2.58 mmol). The solution was charged with HOAt (1 equiv.) and stirred for 1 hour. The reaction was diluted with acetonitrile and purified directly by RP HPLC using C18 as the stationary phase and water / acetonitrile+0.1% formic acid as the mobile phase. The material was lyophilized to give linker payload as a white solid.

[0435] General procedure O: Glucuronide linker-payload synthesisStep 1:

[0436] Amine (1 equiv), Fmoc-BA-Gluc-MABC-PNP carbonate (1 equiv.), and 4- methylmorpholine (3 equiv.) were dissolved in dimethylformamide (0.1 M). The solution was charged with HOAt (1 equiv.) and stirred for 1-6 hours. The reaction was diluted with 1:1 ethylacetate:hexanes and 10% LiCl(aq). The aqueous solution is extracted for a total of 3 times with 1:1 ethyl acetate:hexanes. The combined organic layers were washed with sat. NH4Cl(aq)then brine. The solution is dried over sodium sulfate, filtered, and concentrated in vacuo. The crude material is used without further purification. Step 2:

[0437] Crude Fmoc amine was dissolved in methanol (0.1 M) and charged with lithium hydroxide (5 equiv) at ambient temperature. The reaction was stirred at ambient temperature overnight (16-18 hours). The reaction was quenched with formic acid and concentrated in vacuo. The crude material was triturated with 1:1 ethyl acetate hexanes then passed through a silica plug using 1:1 ethyl acetate hexanes then methanol. The methanol fraction was concentrated in vacuo and used without further purification. Step 3:

[0438] Crude amine and N-ethyldiisopropylamine (2 equiv) were dissolved in dimethylformamide (0.1 M) at ambient temperature. The solution was charged with N-[3-(2,5- dioxo-1-pyrrolidinyloxy)-3-oxopropyl](2,5-dioxo-3-pyrrolin-1-yl)acetamide 90%w / w (1 equiv) in a single portion. The reaction was stirred overnight (17 hours). The reaction was diluted with acetonitrile and was purified by RP HPLC using C18 as the stationary phase and water / acetonitrile +0.1% formic acid as the mobile phase. The desired fractions were lyophilized to provide the desired product as a white fluffy solid.

[0439] General procedure P: Urea or carbamate formation

[0440] To a solution of an amine or an alcohol (1.0 equiv) in DMF at ambient temperature was added p-nitrobenzenyl chloroformate (2.0 equiv) and the resulting reaction mixture was stirred for 16 h. Then, an excess of a different amine (4.5 equiv) was added and the reaction was stirred for an additional 16 h. The reaction was diluted with ethyl acetate, washed with 1M HCl, sat. NaHCO3, brine, dried over Na2SO4, filtered and concentrated under reduced pressure. The crude was purified by flash chromatography to afford the desired product.

[0441] General procedure Q: Linker payload Alloc / allyl deprotection

[0442] Allyl / alloc protected linker payload (1 equiv.) and phenylsilane (1 equiv. / protecting group) were stirred in anhydrous dichloromethane (0.1 M) under argon. The solution was charged with palladium tetrakis (0.2 equiv.) and stirred under argon until the reaction was complete by LCMS. The reaction was purified directly by HPLC to provide the desired product.

[0443] General procedure S: 2’ amino alkylation

[0444] Amine (1 equiv), DIPEA (3 equiv), and electrophile (1.5 equiv) are mixed in acetonitrile. The solution is heated to 55 °C for 24 hours. The reaction is cooled to ambient temperature and concentrated in vacuo and purified by flash column chromatography or reverse phase HPLC.

[0445] General procedure T: 13’ esterification

[0446] The alcohol (1 equiv) was dissolved in DCM then charged with anhydride (1.1) and triethylamine (1.5) or carboxylic acid (1.1) and DCC (1.5). The solution was charged with DMAP (0.1 equiv) and stirred at ambient temperature for 1-24 hours. The solution was concentrated in vacuo then purified by flash column chromatography.

[0447] General Procedure U: Triazole formation

[0448] Azide was combined with acid, copper and corresponding alkyne, stirred for 18 hours, concentrated and directly purified via silica gel chromatography.

[0449] General procedure V:

[0450] Amine (1.0 equiv) and 2-propene-1- chloroformate (1.3 equiv) were dissolved in DCM. The solution was charged with pyridine (10 equiv). The reaction was stirred at ambient temperature until full conversion was observed by LCMS (254 nm). The reaction was concentrated in vacuo then dissolved in ethyl acetate . The solution was washed with 1 N HCl(aq)(x 2) then sat. NaHCO3(aq)then brine . The organic layer was dried over sodium sulfate, filtered, and concentrated in vacuo. The crude material was used without further purification.

[0451] General procedure W:Step 1:

[0452] Payload XX (1 equiv), AM-G-Alloc XX (2eq) and 1-pyridinium p-toluenesulfonate (0.1 equiv) were added to a reaction vial equipped with a stir bar and left to stir at 40C overnight under argon.1 additional equiv of AM-G-Alloc XX and 1-pyridinium p-toluenesulfonate added and left to stir at 40 for 24hr. Diluted with ethyl acetate, washed with sat sodium carb, and extracted with ethyl acetate. Organic washed with brine, dried over sodium sulfate, filtered, and concentrated in vacuo. Used as crude in the next step. Step 2:

[0453] A vial equipped with a stir bar was charged with step 1 crude (1eq) in DCM. Phenysilane (1.2eq) and Pd(PPh3)4 were added and the reaction mixture was left to stir at ambient temperature for 45 under argon. The reaction was filtered through Cellite. The crude material was purified by flash column chromatography using ethyl acetate then 10% methanol in DCM then methanol. Step 3:

[0454] A vial equipped with a stir bar was charged with step 2 product (1eq) in DMF. Carboxylic acid (1.5eq), HOAt (1eq), HATU (1.2eq), and DIPEA (3eq) were added to the reaction vial and left to stir at ambient temperature for 30min. The reaction vial was diluted with ACN and directly injected on HPLC (10-95% ACN in Water- no additives) and lyophilized to yield white solid. Example 0.1: Synthesis of PA-90 and PA-120 SchemeStep 1:

[0455] Synthesis of (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12'-hydroxy-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro- [oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione

[0456] (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-hydroxy-17'-[(1R)-1- hydroxyethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane-2,26'- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]-heptacosane]-4',18',20'-triene-11',22'-dione (22.300 g, 41.868 mmol, 1.000 eq) was dissolved in DMF (334.500 ml, 15.000 vol) at ambient temperature. Then, imidazole (8.551 g, 125.603 mmol, 3.000 eq) was added. Next, tert-butyldimethylsilyl chloride (12.621 g, 83.735 mmol, 2.000 eq) was slowly added. Reaction was stirred at ambient temperature for 2 h. After that time, reaction was diluted with ethyl acetate and washed with water (2 x) and brine. Organic layer was dried over Na2SO4, filtered and concentrated. The crude was purified using FCC column, eluting with ethyl acetate in cyclohexane (0-100%). The fraction was evaporated to give (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1- [(tert-butyldimethylsilyl)oxy]ethyl]-12'-hydroxy-5',13',25'-trimethyl-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (19.380 g, 29.959 mmol, 71.56%) as a white foam.

[0457] 1H NMR (300 MHz, CDCl3) δ 7.76 – 7.41 (m, 1H), 6.68 (t, J = 11.4 Hz, 1H), 6.09 (dd, J = 15.6, 3.1 Hz, 1H), 5.92 – 5.65 (m, 2H), 5.57 – 5.27 (m, 1H), 4.83 – 4.31 (m, 2H), 4.13 (dd, J = 7.3, 2.7 Hz, 1H), 3.88 (tt, J = 9.7, 5.4 Hz, 3H), 3.66 – 3.43 (m, 3H), 3.13 (d, J = 4.0 Hz, 1H), 2.81 (d, J = 3.2 Hz, 1H), 2.47 (dd, J = 15.4, 8.2 Hz, 1H), 2.23 (dt, J = 15.4, 4.7 Hz, 1H), 2.18 – 2.06 (m, 1H), 2.06 – 1.85 (m, 3H), 1.82 – 1.62 (m, 6H), 1.36 – 1.21 (m, 1H), 1.08 (dd, J = 9.4, 6.5 Hz, 6H), 0.91 (s, 9H), 0.84 (s, 3H), 0.09 (d, J = 2.3 Hz, 6H).Step 2:

[0458] Synthesis of (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1S)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-11',22'-dioxo-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-trien-12'-yl trifluoromethanesulfonate

[0459] To a solution of (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12'-hydroxy-5',13',25'-trimethyl-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (19.380 g, 29.959 mmol, 1.000 eq) in DCM (1356.600 ml, 70.000 vol) and pyridine (23.698 g, 24.231 ml, 299.586 mmol, 10.000 eq) at -10 °C, triflic anhydride (16.904 g, 10.062 ml, 59.917 mmol, 2.000 eq) was slowly added. The reaction was stirred at -10 °C and slowly allowed to warm to 0 °C within 1 h. The reaction was diluted with water and extracted with DCM (x 2). The combined organic layers were washed with water and dried over Na2SO4, filtered, and concentrated to obtain crude product: (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'- [(1S)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-11',22'-dioxo-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-trien-12'-yl trifluoromethanesulfonate (21.570 g, 26.860 mmol, 89.66%) as a white foam. The product was used in the next step without any further purification.

[0460] 1H NMR (300 MHz, CDCl3) δ 7.51 (dd, J = 15.7, 11.4 Hz, 1H), 6.68 (t, J = 11.4 Hz, 1H), 6.10 (dd, J = 15.7, 3.1 Hz, 1H), 5.78 (dd, J = 9.5, 4.6 Hz, 2H), 5.44 (d, J = 5.1 Hz, 1H), 4.99 (d, J = 3.1 Hz, 1H), 4.77 – 4.24 (m, 2H), 4.08 – 3.81 (m, 3H), 3.70 – 3.45 (m, 3H), 3.14 (d, J = 4.0 Hz, 1H), 2.82 (d, J = 4.1 Hz, 1H), 2.47 (dd, J = 15.3, 8.2 Hz, 2H), 2.24 (dt, J = 15.3, 4.9 Hz, 1H), 2.09 – 1.85 (m, 3H), 1.75 (d, J = 10.9 Hz, 6H), 1.25 (d, J = 6.8 Hz, 3H), 1.06 (d, J = 6.1 Hz, 3H), 0.91 (s, 9H), 0.82 (s, 3H), 0.09 (d, J = 1.3 Hz, 6H). Step 3:

[0461] Synthesis of (1'R,2S,3'R,8'R,12'R,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12'-iodo-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro-[oxirane- 2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione

[0462] Crude (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1S)-1-[(tert-butyl- dimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-11',22'-dioxo-2',10',16',23'-tetraoxa-spiro[oxirane- 2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-trien-12'-yl trifluoromethanesulfonate (21.570 g, 27.691 mmol, 1.000 eq)) was dissolved in DMF (215.700 ml, 10.000 vol). Reaction mixture was charged with sodium iodide (6.226 g, 41.537 mmol, 1.500 eq) and heated at 50 °C for 1 h. Then, reaction was diluted with EtOAc, washed with LiCl (10% aq. solution, twice) andbrine. Organic layer was dried over Na2SO4, filtered and evaporated to give crude product: (1'R,2S,3'R,8'R,12'R,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12'-iodo-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane- 2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (22.380 g, 28.094 mmol, yield quantitative) as an orange foam. The product was used in the next step without any further purification.

[0463] 1H NMR (300 MHz, CDCl3) δ 7.52 (dd, J = 15.6, 11.5 Hz, 1H), 6.67 (t, J = 11.3 Hz, 1H), 6.07 (dd, J = 15.6, 3.1 Hz, 1H), 5.91 – 5.71 (m, 2H), 5.45 (d, J = 5.2 Hz, 1H), 4.80 – 4.24 (m, 2H), 4.12 (d, J = 9.1 Hz, 1H), 3.87 (d, J = 5.3 Hz, 2H), 3.81 (s, 1H), 3.66 – 3.57 (m, 2H), 3.54 – 3.42 (m, 1H), 3.14 (d, J = 4.1 Hz, 1H), 2.86 (d, J = 4.2 Hz, 1H), 2.48 (dd, J = 15.3, 8.2 Hz, 1H), 2.23 (dt, J = 15.4, 4.8 Hz, 1H), 2.13 – 1.87 (m, 6H), 1.77 (s, 3H), 1.54 – 1.45 (m, 1H), 1.31 (d, J = 6.5 Hz, 3H), 1.07 (d, J = 6.0 Hz, 3H), 0.91 (s, 12H), 0.09 (d, J = 1.8 Hz, 6H). Step 4:

[0464] Synthesis of (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-azido-17'-[(1S)-1- [(tert-butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane- 2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione

[0465] Crude (1'R,2S,3'R,8'R,12'R,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12'-iodo-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane- 2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (22.380 g, 29.572 mmol, 1.000 eq) was dissolved in DMF (223.800 ml, 10.000 vol) and reaction was charged with sodium azide (5.768 g, 88.717 mmol, 3.000 eq) and stirred at ambient temperature for 48 h. After that time, reaction was diluted with ethyl acetate and washed with LiCl (10% aq. solution, twice) and brine. Organic layer was dried over Na2SO4, filtrated and concentrated to give crude (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-azido-17'-[(1S)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane-2,26'- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (19.230 g, 27.189 mmol, 91.94%) as an orange foam. The product was used in the next step without any further purification.

[0466] 1H NMR (300 MHz, CDCl3) δ 7.56 (dd, J = 15.6, 11.5 Hz, 1H), 6.68 (t, J = 11.4 Hz, 1H), 6.08 (dd, J = 15.7, 3.1 Hz, 1H), 5.90 – 5.60 (m, 2H), 5.45 (d, J = 5.2 Hz, 1H), 4.66 (d, J = 12.3 Hz, 1 H), 4.25 (d, J = 12.3 Hz, 1 H), 4.00 – 3.73 (m, 3H), 3.61 (d, J = 5.5 Hz, 1H), 3.53 (t, J = 5.8 Hz, 2H), 3.14 (d, J = 4.0 Hz, 1H), 2.83 (d, J = 4.1 Hz, 1H), 2.47 (dd, J = 15.3, 8.1 Hz, 2H), 2.22 (dt, J = 15.3, 4.8 Hz, 1H), 2.10 – 1.85 (m, 4H), 1.76 (s, 3H), 1.73 – 1.63 (m, 2H), 1.40 – 1.21 (m, 1H), 1.10 (dd, J = 18.3, 6.3 Hz, 6H), 0.91 (s, 9H), 0.82 (s, 3H), 0.17 – 0.01 (m, 6H).Step 5:

[0467] Synthesis of (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-amino-17'-[(1R)-1- [(tert-butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane- 2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione

[0468] Crude (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-azido-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane-2,26'- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (19.000 g, 26.864 mmol, 1.000 eq) was dissolved in THF (285.000 ml, 15.000 vol) and reaction mixture was charged with triphenylphosphine (21.139 g, 80.592 mmol, 3.000 eq) and stirred at 50 °C for 1.5 h. After that time, water (95.000 ml, 5.000 vol) was added to the reaction mixture and reaction was heated at 60 °C overnight. Reaction mixture was diluted with water, extracted with ethyl acetate (x 2). Organic layers were combined, dried over Na2SO4, filtered and concentrated. Triphenylphosphine oxide was partially removed by FCC eluting with ethyl acetate in cyclohexane (0-70%). Additional amount of triphenylphosphine oxide was removed by trituration with methanol. Desired product was isolated using RP-FCC (PF-X – polymer column), eluting with ACN in water under basic conditions (0.2% ammonia in both eluents). The proper fraction was evaporated to give (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)- 12’-amino-17’-[(1R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione (8.450 g, 13.082 mmol, 48.70%) as a white solid.

[0469] 1H NMR (300 MHz, CDCl3) δ 7.55 (dd, J = 15.7, 11.5 Hz, 1H), 6.67 (t, J = 11.4 Hz, 1H), 6.08 (dd, J = 15.7, 3.1 Hz, 1H), 5.78 (dd, J = 11.9, 6.3 Hz, 2H), 5.44 (d, J = 5.2 Hz, 1H), 4.38 (d, J = 4.2 Hz, 2H), 4.02 – 3.89 (m, 1H), 3.89 – 3.76 (m, 2H), 3.70 – 3.50 (m, 3H), 3.43 (d, J = 3.6 Hz, 1H), 3.13 (d, J = 4.1 Hz, 1H), 2.82 (d, J = 4.1 Hz, 1H), 2.47 (dd, J = 15.4, 8.2 Hz, 1H), 2.32 – 2.10 (m, 2H), 2.04 – 1.77 (m, 5H), 1.75 (s, 3H), 1.67 (q, J = 6.3 Hz, 2H), 1.28 (s, 1H), 1.08 (dd, J = 9.5, 6.5 Hz, 6H), 0.91 (s, 9H), 0.85 (s, 3H), 0.09 (d, J = 2.3 Hz, 6H). Step 6:

[0470] Synthesis of (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-amino-17’-[(1R)- 1-hydroxyethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane-2,26’- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’-dione

[0471] (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-amino-17’-[(1R)-1-[(tert- butyldi-methylsilyl)oxy]ethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane-2,26’- tetra-cyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’-dione (8.450 g, 13.082 mmol, 1.000 eq) was dissolved in THF (169.000 ml, 20.000 vol) under argon atmosphere. Next,tetrabutylammonium fluoride solution 1.0 M in THF (6.841 g, 26.165 ml, 26.165 mmol, 2.000 eq) was added. Reaction was stirred for 2 h at ambient temperature. After that time, solvents was evaporated and crude was purified using RP-FCC (PF-X – polymer column), eluting with ACN in water under basic conditions (0.2% ammonia in both eluents). Proper fraction was evaporated to give (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-amino-17’-[(1R)-1- hydroxyethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane-2,26’- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’-dione (5.980 g, 11.248 mmol, 85.98%) as a white solid.

[0472] 1H NMR (300 MHz, MeOD) δ 7.80 – 7.49 (m, 1H), 6.78 (t, J = 11.4 Hz, 1H), 6.14 (dd, J = 15.6, 3.1 Hz, 1H), 5.85 (dd, J = 8.3, 4.2 Hz, 1H), 5.78 (d, J = 11.1 Hz, 1H), 5.42 (dd, J = 5.1, 1.9 Hz, 1H), 4.39 (dd, J = 70.5, 12.3 Hz, 2H), 3.93 – 3.81 (m, 1H), 3.81 – 3.68 (m, 3H), 3.64 – 3.46 (m, 2H), 3.39 (d, J = 3.8 Hz, 1H), 3.07 (d, J = 4.0 Hz, 1H), 2.87 (d, J = 4.0 Hz, 1H), 2.49 (dd, J = 15.3, 8.3 Hz, 1H), 2.22 – 2.02 (m, 2H), 2.03 – 1.94 (m, 2H), 1.94 – 1.83 (m, 2H), 1.74 (s, 3H), 1.71 (d, J = 2.7 Hz, 1H), 1.65 – 1.48 (m, 1H), 1.10 (dd, J = 13.4, 6.6 Hz, 6H), 0.84 (s, 3H). Example 0.2, synthesis of DL-36Step 1:

[0473] Payload, (38.7 µmol, 1 equiv.), Fmoc-BA-Gluc-MABC-PNP carbonate (38.7 µmol, 1 equiv.), and 4-methylmorpholine (3 equiv.) were dissolved in dimethylformamide (0.1 M). The solution was charged with HOAt (1 equiv.) and stirred for 1-6 hours. The reaction was diluted with 1:1 ethyl acetate:hexanes and 10% LiCl(aq). The aqueous solution is extracted for a total of 3 times with 1:1 ethyl acetate:hexanes. The combined organic layers were washed with sat. NH4Cl(aq)then brine. The solution is dried over sodium sulfate, filtered, and concentrated in vacuo. The crude material is used without further purification. Step 2:

[0474] Step 1 crude (53.2 mg, 38.7 µmol) was dissolved in methanol (387 µL, 9.54 mmol) and charged with lithium hydroxide (4.63 mg, 5 eq., 193 µmol) at ambient temperature. The reaction was stirred at ambient temperature overnight (16-18 hours). The reaction was quenched with formic acid and concentrated in vacuo. The crude material was triturated with 1:1 ethyl acetate hexanes then passed through a silica plug using 1:1 ethyl acetate hexanes then methanol. The methanol fraction was concentrated in vacuo and used without further purification. Step 3:

[0475] Step 2 crude (39.2 mg, 38.7 µmol) and N-ethyldiisopropylamine (13.5 µL, 2 eq., 77.3 µmol) were dissolved in dimethylformamide (387 µL, 4.99 mmol) at ambient temperature. The solution was charged with N-[3-(2,5-dioxo-1-pyrrolidinyloxy)-3-oxopropyl](2,5-dioxo-3- pyrrolin-1-yl)acetamide 90%w / w (13.9 mg, 38.7 µmol) in a single portion. The reaction was stirred overnight (17 hours). The reaction was diluted with acetonitrile (0.5 mL) and was purified by RP HPLC using C18 as the stationary phase and water / acetonitrile +0.1% formic acid as the mobile phase. The desired fractions were lyophilized to provide (2S,3S,4S,5R,6S)-6-{2-[3-(3- {[(2,5-dioxo-3-pyrrolin-1-yl)methyl]carbonylamino}propionylamino)propionylamino]-4-[({2- [N-(1R,3R,8R,12S,13R,17R,18E,20Z,24R,25S,26S)-17-[(R)-1-hydroxyethyl]-5,13,25-trimethyl- 11,22-dioxospiro[(18E,20Z)-2,10,16,23-tetraoxatetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosa-4,18,20- triene-26,2'-oxiran]-12-ylcarbamoyl]ethyl}(aminocarbonyloxy))methyl]phenoxy}-3,4,5- trihydroxytetrahydro-2H-pyran-2-carboxylic acid (8.8 mg, 6.4 µmol) in 17% yield (89%, 254nm) over 3 steps as a white fluffy solid. m / z M+H: expected 1223.49 observed: 1223.00 m / z M-H: expected 1221.47 observed: 1221.80

[0476] 1H NMR (600 MHz, MeOD) δ 8.17 (s, 1H), 8.13 (d, J = 9.1 Hz, 1H), 7.61 (d, J = 27.2 Hz, 0H), 7.27 (d, J = 8.9 Hz, 1H), 7.07 (s, 1H), 6.90 (d, J = 9.2 Hz, 1H), 6.87 (s, 2H), 6.76 (t, J = 11.4 Hz, 1H), 6.13 (d, J = 18.2 Hz, 1H), 5.87 – 5.81 (m, 1H), 5.77 (d, J = 11.0 Hz, 1H), 5.37 (s, 1H), 4.63 – 4.52 (m, 4H), 4.40 (s, 1H), 4.17 (d, J = 12.3 Hz, 1H), 4.13 (s, 2H), 3.83 (s, 1H), 3.75 – 3.68 (m, 3H), 3.56 (d, J = 8.4 Hz, 3H), 3.53 – 3.45 (m, 1H), 3.05 (d, J = 3.9 Hz, 1H), 2.86 (d, J = 4.1 Hz, 1H), 2.69 (s, 2H), 2.54 – 2.43 (m, 1H), 2.40 (t, J = 6.5 Hz, 2H), 2.25 (s, 1H), 2.12 (d, J = 15.0 Hz, 1H), 1.97 (s, 2H), 1.91 – 1.81 (m, 1H), 1.70 (s, 3H), 1.30 (s, 2H), 1.10 (d, J = 6.3 Hz, 3H), 1.06 (d, J = 6.8 Hz, 3H), 0.91 (s, 1H), 0.81 (s, 3H). Example 0.3: synthesis of PA-120Step 1:

[0477] Synthesis of (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-17’-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12’-hydroxy-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione

[0478] (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-hydroxy-17’-[(1R)-1- hydroxyethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane-2,26’- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’-dione (21.350 g, 40.084 mmol, 1.000 eq) was dissolved in DMF (320.250 ml, 15.000 vol) at ambient temperature. Then, imidazole (8.187 g, 120.252 mmol, 3.000 eq) was added. Then, tert-butyldimethylsilyl chloride (12.083 g, 80.168 mmol, 2.000 eq) was slowly added and the reaction mixture was stirred at ambient temperature overnight. Reaction was diluted with ethyl acetate and washed with water (2 x) and brine. Organic layer was dried over Na2SO4, filtered and concentrated. Desired product was isolated using FCC column, eluting with ethyl acetate in cyclohexane (0-100%). The proper fraction was evaporated to give (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-17’- [(1R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-12’-hydroxy-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione (16.080 g, 24.857 mmol, 62.01%) as a white foam.

[0479] 1H NMR (300 MHz, CDCl3) δ 7.69 – 7.47 (m, 1H), 6.69 (t, J = 11.4 Hz, 1H), 6.09 (dd, J = 15.7, 3.1 Hz, 1H), 5.93 – 5.68 (m, 2H), 5.45 (d, J = 5.2 Hz, 1H), 4.65 – 4.25 (m, 2H), 4.21 – 4.08 (m, 1H), 3.97 – 3.77 (m, 3H), 3.72 – 3.43 (m, 3H), 3.13 (d, J = 4.0 Hz, 1H), 2.82 (d, J = 3.9 Hz, 1H), 2.47 (dd, J = 15.4, 8.2 Hz, 1H), 2.23 (dt, J = 15.4, 4.7 Hz, 1H), 2.16 – 2.05 (m, 1H), 2.05 – 1.88 (m, 3H), 1.76 (s, 6H), 1.28 (t, J = 7.1 Hz, 1H), 1.08 (dd, J = 9.5, 6.4 Hz, 6H), 0.91 (s, 9H), 0.85 (s, 3H), 0.09 (d, J = 2.4 Hz, 6H). Step 2’:

[0480] Synthesis of (1’R,2S,3’R,8’R,12’R,13’R,17’R,18’Z,20’Z,24’R,25’S)-17’-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12’-iodo-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione

[0481] (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-17’-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12’-hydroxy-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione (15.000 g, 23.188 mmol, 1.000 eq) with imidazole (4.104 g, 60.288 mmol, 2.600 eq) and triphenylphosphine (7.298 g, 27.825 mmol, 1.200 eq) were dissolved in anhydrous toluene (300.000 ml, 20.000 vol) and heated at 80 °C for 0.5 h. Then, reaction mixture was cooled to ambient temperature and iodine (7.062 g, 27.825 mmol, 1.200 eq) was added. Reaction mixture was then heated at 80 °C for next 2 h and then cooled down. After that time, the reaction mixture was diluted with ethyl acetate and washed with 10% aq. solution of Na2S2O3, water and brine. Organic layer was separated, dried over anhydrous Na2SO4and concentrated under reduced pressure. Product was purified via trituration with methanol. (1’R,2S,3’R,8’R,12’R,13’R,17’R,18’Z,20’Z,24’R,25’S)-17’-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12’-iodo-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione (16.140 g, 21.327 mmol, 91.97%) was obtained as a white solid. The product was used in the next step without any further purification.

[0482] 1H NMR (300 MHz, CDCl3) δ 7.52 (dd, J = 15.6, 11.5 Hz, 1H), 6.67 (t, J = 11.4 Hz, 1H), 6.08 (dd, J = 15.6, 3.2 Hz, 1H), 5.85 (dd, J = 8.2, 4.2 Hz, 1H), 5.79 (d, J = 11.1 Hz, 1H), 5.45 (d, J = 5.2 Hz, 1H), 4.69 – 4.22 (m, 2H), 4.12 (d, J = 9.0 Hz, 1H), 3.98 – 3.83 (m, 2H), 3.80 (s, 1H), 3.64 (dd, J = 10.0, 4.8 Hz, 2H), 3.49 (d, J = 13.2 Hz, 1H), 3.14 (d, J = 4.1 Hz, 1H), 2.86 (d, J = 4.1 Hz, 1H), 2.48 (dd, J = 15.4, 8.3 Hz, 1H), 2.23 (dt, J = 15.3, 4.7 Hz, 1H), 2.12 – 1.87 (m, 5H),1.77 (s, 3H), 1.50 (d, J = 8.1 Hz, 2H), 1.31 (d, J = 6.4 Hz, 3H), 1.07 (d, J = 6.1 Hz, 3H), 0.91 (s, 12H), 0.09 (d, J = 2.1 Hz, 6H). Step 4:

[0483] Synthesis of (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-azido-17’-[(1R)- 1-[(tert-butyldimethylsilyl)oxy]ethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane- 2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’-dione

[0484] (1’R,2S,3’R,8’R,12’R,13’R,17’R,18’Z,20’Z,24’R,25’S)-17’-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-12’-iodo-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione (15.640 g, 20.666 mmol, 1.000 eq) was dissolved in DMF (156.400 ml, 10.000 vol) and reaction mixture was charged with sodium azide (5.374 g, 82.665 mmol, 4.000 eq) and stirred at ambient temperature for 48 h. After that time, reaction was diluted with ethyl acetate and washed with LiCl (10% aq. solution, twice) and brine. Organic layer was dried over Na2SO4, filtrated and concentrated to give (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-azido-17’- [(1R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione (13.510 g, 19.102 mmol, 92.43%) as a white foam. The product was used in the next step without any further purification.

[0485] 1H NMR (300 MHz, CDCl3) δ 7.79 – 7.43 (m, 1H), 6.68 (t, J = 11.4 Hz, 1H), 6.09 (dd, J = 15.6, 3.1 Hz, 1H), 5.92 – 5.64 (m, 2H), 5.60 – 5.23 (m, 1H), 4.67 (d, J = 12.3 Hz, 1H), 4.25 (d, J = 12.3 Hz, 1H), 4.02 – 3.70 (m, 3H), 3.61 (d, J = 5.5 Hz, 1H), 3.53 (t, J = 5.8 Hz, 2H), 3.14 (d, J = 4.0 Hz, 1H), 2.83 (d, J = 4.1 Hz, 1H), 2.46 (dt, J = 13.8, 7.2 Hz, 2H), 2.23 (dt, J = 15.3, 4.8 Hz, 1H), 2.11 – 1.85 (m, 4H), 1.76 (s, 3H), 1.72 – 1.50 (m, 2H), 1.37 – 1.22 (m, 1H), 1.13 (d, J = 6.7 Hz, 3H), 1.07 (d, J = 6.0 Hz, 3H), 0.91 (s, 9H), 0.82 (s, 3H), 0.10 (d, J = 2.6 Hz, 6H). Step 5:

[0486] Synthesis of (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-amino-17’-[(1R)- 1-[(tert-butyldimethylsilyl)oxy]ethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane- 2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’-dione

[0487] Crude (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)-12’-azido-17’-[(1R)-1- [(tert-butyldimethylsilyl)oxy]ethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’-tetraoxaspiro[oxirane- 2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’-dione (14.350 g, 20.317 mmol, 1.000 eq)) was dissolved in THF (215.250 ml, 15.000 vol) and reaction mixture was charged with triphenylphosphine (15.987 g, 60.952 mmol, 3.000 eq) and stirred at 50 °C for 1.5 h. After that time, water (71.750 ml, 5.000 vol) was added and reaction was heated at 60 °Covernight. After that time, water was added and reaction was extracted with ethyl acetate (2 x). Organic layers were combined, dried over Na2SO4, filtered and concentrated. Triphenylphosphine oxide was partially removed by FCC eluting with ethyl acetate in cyclohexane (0-70%). Additional amount of triphenylphosphine oxide was removed by trituration with methanol. Desired product was isolated using RP-FCC (PF-X – polymer column), eluting with ACN in water under basic conditions (0.2% ammonia in both eluents). The proper fraction was evaporated to give (1’R,2S,3’R,8’R,12’S,13’R,17’R,18’Z,20’Z,24’R,25’S)- 12’-amino-17’-[(1R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-5’,13’,25’-trimethyl-2’,10’,16’,23’- tetraoxaspiro[oxirane-2,26’-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4’,18’,20’-triene-11’,22’- dione (10.690 g, 16.550 mmol, 86.65%) as a white solid

[0488] 1H NMR (300 MHz, CDCl3) δ 7.52 (dd, J = 15.7, 11.5 Hz, 1H), 6.65 (t, J = 11.4 Hz, 1H), 6.06 (dd, J = 15.6, 3.1 Hz, 1H), 5.86 – 5.62 (m, 2H), 5.42 (d, J = 5.2 Hz, 1H), 4.37 (d, J = 2.0 Hz, 2H), 4.10 – 3.74 (m, 3H), 3.69 – 3.40 (m, 4H), 3.10 (d, J = 4.0 Hz, 1H), 2.80 (d, J = 4.1 Hz, 1H), 2.44 (dd, J = 15.3, 8.2 Hz, 1H), 2.20 (dt, J = 15.5, 4.8 Hz, 2H), 2.05 – 1.58 (m, 10H), 1.42 – 1.12 (m, 1H), 1.06 (dd, J = 14.8, 6.5 Hz, 6H), 0.89 (s, 9H), 0.82 (s, 3H), 0.07 (d, J = 2.4 Hz, 6H). Step 6:

[0489] Synthesis of (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-amino-17'-[(1R)-1- hydroxyethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane-2,26'- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione

[0490] (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-amino-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane-2,26'- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (10.160 g, 15.730 mmol, 1.000 eq) was dissolved in THF (203.200 ml, 20.000 vol) under argon atmosphere. Then, tetrabutylammonium fluoride solution 1.0 M in THF (8.226 g, 31.460 ml, 31.460 mmol, 2.000 eq) was added. The reaction was stirred for 2 h. After that time, solvents were evaporated and crude was purified using RP-FCC (PF-X – polymer column), eluting with ACN in water under basic conditions (0.2% ammonia in both eluents). Proper fraction was evaporated to give (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-amino-17'-[(1R)-1-hydroxyethyl]- 5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane-2,26'- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (6.690 g, 12.584 mmol, 80.00%) as a white solid.

[0491] 1H NMR (300 MHz, MeOD) δ 7.84 – 7.49 (m, 1H), 6.79 (t, J = 11.4 Hz, 1H), 6.15 (dd, J = 15.6, 3.2 Hz, 1H), 5.87 (dd, J = 8.3, 4.2 Hz, 1H), 5.80 (d, J = 11.0 Hz, 1H), 5.43 (d, J = 5.2 Hz, 1H), 4.40 (dd, J = 70.2, 12.3 Hz, 2H), 3.84 (s, 1H), 3.82 – 3.70 (m, 2H), 3.62 – 3.47 (m, 2H),3.40 (d, J = 3.8 Hz, 1H), 3.09 (d, J = 4.0 Hz, 1H), 2.89 (d, J = 4.0 Hz, 1H), 2.50 (dd, J = 15.3, 8.3 Hz, 1H), 2.27 – 1.82 (m, 6H), 1.75 (s, 4H), 1.67 – 1.49 (m, 1H), 1.35 (d, J = 11.3 Hz, 1H), 1.12 (dd, J = 13.3, 6.6 Hz, 6H), 0.85 (s, 3H). Example 0.4: Synthesis of PA-97 Scheme

[0492] Step 1: The TBS deprotection was performed using general procedure H to afford (2S,4'S,5'R,9'R,10'E,12'Z,16'R,16a'S,18'R,19a'R,23a'R)-4'-azido-9'-((R)-1-hydroxyethyl)- 5',16a',21'-trimethyl-4',5',6',7',16',16a',19a',22'-octahydro-1'H,3'H,18'H,23'H-spiro[oxirane-2,17'- [16,18]methano[1,6,12]trioxacyclooctadecino[3,4-d]chromene]-3',14'(9'H)-dione (23 mg, 56%) as a white solid.1H NMR (400 MHz, CHLOROFORM-d) δ (ppm) 7.65 - 7.45 (m, 1H), 6.57 (t, J = 11.4 Hz, 1H), 5.93 (dd, J = 3.4, 15.6 Hz, 1H), 5.76 - 5.66 (m, 2H), 5.36 (br d, J = 4.3 Hz, 1H), 4.66 (d, J = 12.4 Hz, 1H), 4.07 (d, J = 12.3 Hz, 1H), 3.78 (d, J = 5.0 Hz, 1H), 3.69 (d, J = 5.1 Hz, 1H), 3.63 - 3.58 (m, 1H), 3.57 - 3.46 (m, 3H), 3.41 (td, J = 4.9, 9.5 Hz, 1H), 3.05 (d, J = 4.0 Hz, 1H), 2.74 (d, J = 4.0 Hz, 1H), 2.43 - 2.31 (m, 2H), 2.14 (td, J = 4.8, 15.3 Hz, 1H), 2.01 - 1.89 (m, 2H), 1.88 - 1.78 (m, 2H), 1.67 (s, 3H), 1.64 - 1.52 (m, 2H), 1.30 - 1.22 (m, 1H), 1.12 (d, J = 6.1 Hz, 3H), 1.04 (d, J = 6.8 Hz, 3H), 0.71 (s, 3H). LCMS m / z = 558 [M+H].

[0493] Step 2: Add (1R,3R,8R,12S,13R,17R,18E,20Z,24R,25S,26S)-12-azido-17-[(R)-1- hydroxyethyl]-5,13,25-trimethylspiro[(18E,20Z)-2,10,16,23- tetraoxatetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosa-4,18,20-triene-26,2'-oxirane]-11,22-dione (23 mg, 41.6 µmol), acetic acid (0.108 µL, 0.08 eq., 1.9 µmol) and N-ethyldiisopropylamine (0.58 µL, 0.08 eq., 3.33 µmol) to a solution of 2-propynylamine (2.75 mg, 1.2 eq., 49.9 µmol) and CuI (264 µg, 0.1 eq., 4.16 µmol) in dichloromethane (1.05 mL, 16.3 mmol). Stir the resulting solution for 18 h at ambient temperature. Concentrate the solvent in vacuo. Purified the crude by Si column to obtain (1R,3R,8R,12S,13R,17R,18E,20Z,24R,25S,26S)-12-[4-(aminomethyl)-1H- 1,2,3-triazol-1-yl]-17-[(R)-1-hydroxyethyl]-5,13,25-trimethylspiro[(18E,20Z)-2,10,16,23- tetraoxatetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosa-4,18,20-triene-26,2'-oxirane]-11,22-dione (8.7 mg, 34%) as a white solid.1H NMR (400 MHz, CHLOROFORM-d) δ = 8.22 (br s, 1H), 8.04 - 7.99 (m, 1H), 7.67 (br dd, J = 11.8, 15.4 Hz, 1H), 6.69 (t, J = 11.4 Hz, 1H), 6.02 (dd, J = 3.0, 15.5 Hz,1H), 5.88 - 5.74 (m, 2H), 5.41 (br d, J = 4.5 Hz, 1H), 5.32 (s, 2H), 5.31 - 5.24 (m, 1H), 4.88 (br d, J = 12.4 Hz, 1H), 4.22 (br s, 1H), 4.13 - 4.03 (m, 1H), 3.87 (d, J = 5.0 Hz, 1H), 3.72 - 3.51 (m, 5H), 3.14 (br d, J = 3.9 Hz, 1H), 3.04 - 2.95 (m, 1H), 2.83 (br d, J = 4.0 Hz, 1H), 2.72 (br d, J = 6.8 Hz, 1H), 2.46 (br dd, J = 8.2, 15.3 Hz, 1H), 2.23 (td, J = 4.7, 15.2 Hz, 1H), 2.04 - 1.77 (m, 5H), 1.69 (s, 3H), 1.35 - 1.28 (m, 1H), 1.23 - 1.16 (m, 3H), 1.00 (br d, J = 6.8 Hz, 3H), 0.79 (s, 3H). LCMS m / z = 613 [M+H]. Example 0.5: Synthesis of PA-67 Scheme

[0494] Step 1: (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-12'-amino-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-2',10',16',23'-tetraoxaspiro[oxirane-2,26'- tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (0.500 g, 0.774 mmol, 1.000 eq) and Allyl chloroformate (0.112 g, 0.099 ml, 0.929 mmol, 1.200 eq)were dissolved in DCM (10.000 ml, 20.000 vol). Triethylamine, >99.5% (0.235 g, 0.324 ml, 2.322 mmol, 3.000 eq) was added and the resulting mixture was stirred at AT overnight. The reaction was concentrated. The product was purified by FCC (DCM / EtOAc 0-20%) to afford prop-2-en-1-yl N-[(1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-11',22'-dioxo-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-trien-12'- yl]carbamate (300.000 mg, 0.390 mmol, 50.44%).

[0495] Step 2: prop-2-en-1-yl N-[(1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)- 1-[(tert-butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-11',22'-dioxo-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-trien-12'- yl]carbamate (37.999 mg, 0.049 mmol, 1.000 eq)was dissolved inTHF (0.760 ml, 20.000 vol) and Sodium hydride (60 % dispersion in mineral oil) (0.002 g, 0.074 mmol, 1.500 eq) was added at 0 C. Methyl iodide (0.021 g, 0.009 ml, 0.148 mmol, 3.000 eq)was added and the resulting mixture was stirred at AT overnight. The reaction was slowly quenched with water and extracted with EtOAc. Organic layer was combined and dried over MgSO4. The crude was used in the next step without further purification.

[0496] Step 3: Prop-2-en-1-yl N-[(1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)- 1-[(tert-butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-11',22'-dioxo-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-trien-12'-yl]-N- methylcarbamate (0.226 g, 0.304 mmol, 0.200 eq)was dissolved in DCM (3.200 ml, 20.000 vol)and the mixture was degassed with argon for 10 min. Thenphenylsilane (0.160 g, 1.521 mmol, 1.000 eq)andTetrakis(triphenylphosphine)palladium (0.070 g, 0.061 mmol, 0.040 eq)were added. The resulting mixture was stirred at AT overnight. The product was purified by FCC (DCM / EtOAc 0-25%).

[0497] Step 4: (1'R,2S,3'R,8'R,12'S,13'R,17'R,18'Z,20'Z,24'R,25'S)-17'-[(1R)-1-[(tert- butyldimethylsilyl)oxy]ethyl]-5',13',25'-trimethyl-12'-(methylamino)-2',10',16',23'- tetraoxaspiro[oxirane-2,26'-tetracyclo[22.2.1.0³,⁸.0⁸,²⁵]heptacosane]-4',18',20'-triene-11',22'-dione (170.000 mg, 0.245 mmol, 1.000 eq)was dissolved in anhydrous THF (3.400 ml, 20.000 vol)followed by addition of Tetrabutylammonium fluoride solution 1.0 M in THF (0.070 g, 0.078 ml, 0.269 mmol, 1.100 eq). Then the resulting mixture was stirred at ambient temperature overnight. UPLC / MS confirmed formation of DP. The crude product was purified by RP-FCC (40 g PF-X, ACN / H2O +0.2% NH3) to afford (2S,4'S,5'R,9'R,10'E,12'Z,16'R,16a'S,18'R,19a'R,23a'R)-9'-((R)-1-((tert- butyldimethylsilyl)oxy)ethyl)-5',16a',21'-trimethyl-4'-(methylamino)-4',5',6',7',16',16a',19a',22'- octahydro-1'H,3'H,18'H,23'H-spiro[oxirane-2,17'- [16,18]methano[1,6,12]trioxacyclooctadecino[3,4-d]chromene]-3',14'(9'H)-dione (130 mg, 90%). Example 0.6: Synthesis

[0498] Step 1: To a solution of Roridin A (1 g) in dry tetrahydrofuran (20 mL) was added sodium hydride 60%w / w (82.6 mg, 1.1 eq., 2.07 mmol)at 0 °C. Warm the reaction to ambient temperature and stirred at RT for 10 min. Methyl bromoacetate (203 μL, 1.1 eq., 2.07 mmol) was added and stirred at rt. Monitor the reaction at 30 min and quench the reaction by acetic acid (2.28 μL, 2 eq., 39.8 μmol)at 0 °C. Concentrate the reaction mixture and purify the resulting oil by HPLC to obtain methyl ester (1.05 g) in 92% yield as white solid.1H NMR (600 MHz, CDCl3) δ 8.09 (q, J = 1.9 Hz, 0H), 7.62 (t, J = 13.6 Hz, 1H), 6.63 (t, J = 11.1 Hz, 1H), 5.98 (d, J = 15.4 Hz, 1H), 5.82 – 5.74 (m, 2H), 5.42 (s, 1H), 4.44 – 4.31 (m, 3H), 4.00 – 3.94 (m, 2H), 3.84 (t, J = 4.0 Hz, 1H), 3.74 (q, J = 1.9 Hz, 3H), 3.61 (dt, J = 31.7, 13.1 Hz, 4H), 3.11 (t, J = 3.5 Hz, 1H), 2.79 (d, J = 3.7 Hz, 1H), 2.44 (dd, J = 15.6, 8.3 Hz, 1H), 2.20 (d, J = 19.4 Hz, 2H), 2.11 – 1.96 (m, 1H), 1.89 (d, J = 10.3 Hz, 2H), 1.74 (s, 4H), 1.43 (d, J = 35.7 Hz, 1H), 1.33 (s, 1H), 1.18 (ddd, J = 10.6, 5.4, 2.4 Hz, 6H), 0.95 – 0.90 (m, 1H), 0.78 (d, J = 3.1 Hz, 3H). LCMS m / z = 605.1 [M+H].

[0499] Step 2: To a solution of methyl ester (1.05 g) in dry tetrahydrofuran (20 mL) was added lithium hydroxide (43.7 mg, 1.1 eq., 1.82 mmol)and stirred at rt. Monitor the reaction until finished and quench the reaction by acetic acid (104 mg, 1.74 mmol)at 0 C. Concentrate the reaction mixture and purify by HPLC to obtain the compound above (940 mg) in 91% yield as white solid.

[0500] 1H NMR (600 MHz, MeOD) δ 7.64 – 7.57 (m, 1H), 6.75 (t, J = 11.4 Hz, 1H), 6.13 (dd, J = 15.6, 3.2 Hz, 1H), 5.84 (dd, J = 8.3, 4.2 Hz, 1H), 5.76 (d, J = 11.1 Hz, 1H), 5.43 – 5.39 (m, 1H), 4.47 (d, J = 12.2 Hz, 1H), 4.36 – 4.27 (m, 1H), 4.20 (d, J = 16.7 Hz, 1H), 4.02 – 3.96 (m, 2H), 3.82 (dt, J = 5.2, 2.3 Hz, 1H), 3.78 – 3.71 (m, 3H), 3.59 (dt, J = 10.3, 5.4 Hz, 1H), 3.49 (td, J = 8.6, 4.8 Hz, 1H), 3.05 (d, J = 4.0 Hz, 1H), 2.85 (d, J = 4.0 Hz, 1H), 2.47 (dd, J = 15.3, 8.3 Hz, 1H), 2.22 – 2.08 (m, 2H), 2.04 – 1.80 (m, 6H), 1.74 (s, 3H), 1.62 (tq, J = 13.9, 6.7 Hz, 1H), 1.11 (t, J = 6.7 Hz, 6H), 0.80 (s, 3H). LCMS m / z = 591.1 [M+H].

[0501] In some embodiments, the compound is selected from compounds in Table 1A. Table 1A. Representative compounds disclosed herein.

[0502] In some embodiments, the compound is selected from compounds in Table 1B.Table 1b. Representative compounds disclosed herein

[0503] In some embodiments, the compound is selected from compounds in Table 1A and Table 1B.Characterization of CompoundsExample 1: Drug-Linker Syntheses Example 1.1: Synthesis of Compound X4 Scheme 1Step 1: Synthesis of Compound X1A

[0504] To a solution of roridin A (10 mg, 18.8 µmol) in tetrahydrofuran (944 µL, 11.6 mmol) at 0 ℃, was added Lithium bis(trimethylsilyl)amide (5.65 mg, 1.8 eq., 33.8 µmol, and the reaction was stirred for 0.5 hours at 0 ℃. Then {[allyl(oxycarbonylamino)]methyl}carbonylamino)methyl acetate (13 mg, 3 eq., 56.3 µmol) was added to the solution . The mixture was allowed to warm to room temperature. Until the completion of the reaction was observed, {[allyl(oxycarbonylamino)]methyl}carbonylamino)methyl acetate (4.32 mg, 18.8 µmol) and Lithium bis(trimethylsilyl)amide (3.14 mg, 18.8 µmol) were added every hour (ca.6 hours in total). The reaction was quenched with saturated aqueous ammonium chloride (1.5 mL) and extracted with ethyl acetate (2 mL x 4). The combined organic layers were washed with H2O (2 mL x 2), dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The crude material was purified by prep-TLC to obtain Compound X1A (12 mg, 17.1 µmol) as a colorless solid in 91% yield. LCMS [M+H]+expected: 703.3, observed: 703.3. Step 2: Synthesis of Compound X2

[0505] To a solution of Compound X1A (12 mg, 17.1 µmol) in dichloromethane (2.4 mL, 37.5 mmol) was added tetrakis(triphenylphosphine)palladium (0) (1.97 mg, 0.1 eq., 1.71 µmol) and phenylsilane (2.45 µL, 1.2 eq., 20.5 µmol). The reaction was stirred at room temperature for 1 h under N2. The mixture was filtered, and the plug was washed with dichloromethane (5 ml). Thefiltrate was concentrated in vacuo and purified by flash column chromatography (10% MeOH in DCM) to deliver Compound X2 (10 mg, 16.2 µmol) as a white solid in 95% yield.1H NMR (600 MHz, CDCl3): δ 8.03 – 7.95 (m, 1H), 7.58 (dd, J = 15.5, 11.7 Hz, 1H), 6.61 (t, J = 11.3 Hz, 1H), 5.96 (dd, J = 15.5, 3.1 Hz, 1H), 5.77 (t, J = 8.8 Hz, 2H), 5.45 – 5.37 (m, 1H), 5.28 (d, J = 11.9 Hz, 2H), 4.85 (dd, J = 10.6, 7.8 Hz, 1H), 4.73 (dd, J = 10.7, 6.6 Hz, 1H), 4.34 (q, J = 12.4 Hz, 2H), 4.05 (d, J = 3.3 Hz, 1H), 3.83 (d, J = 5.1 Hz, 1H), 3.66 – 3.54 (m, 3H), 3.55 – 3.49 (m, 1H), 3.42 – 3.30 (m, 2H), 3.10 (d, J = 4.0 Hz, 1H), 2.80 (d, J = 4.0 Hz, 1H), 2.62 (q, J = 1.3 Hz, 10H), 2.43 (dd, J = 15.5, 8.2 Hz, 1H), 2.19 (dt, J = 15.9, 5.0 Hz, 1H), 2.08 – 2.02 (m, 2H) overlapping, 1.73 (s, 3H), 1.17 (d, J = 6.1 Hz, 3H), 1.12 (d, J = 6.8 Hz, 3H), 0.79 (s, 3H). LCMS [M+H]+expected: 619.3, observed 619.3. Step 3: Synthesis of Compound X4

[0506] Compound X2 (10 mg, 13.3 µmol) was transferred to an oven dried center draining 1.5 mL vial using DMF (100 μL). The vial was charged with Compound X3 (7.51 mg, 1.2 eq., 15.9 µmol), 1-hydroxy-7-azabenzotriazole (1.8 mg, 13.3 µmol), and diisopropylamine (4.63 µL, 2 eq., 26.5 µmol) and stirred with a triangle shaped stir bar. To the ambient temperature solution, HATU (5.04 mg, 13.3 µmol) was added. The reaction was quenched with NaHCO3(aq)(0.5 mL) and extracted with ethyl acetate (1ml x 3). The organic solution was washed with brine, dried over Na2SO4and concentrated under vacuum. Then purified by flash column chromatography (10% MeOH in DCM) and HPLC to deliver Compound X4 (6.5 mg, 6.06 µmol) in 60% yield as a white solid.1H NMR (600 MHz, Acetone) δ 8.07 (t, J = 5.8 Hz, 1H), 7.92 (q, J = 5.4 Hz, 2H), 7.78 – 7.72 (m, 2H), 7.62 – 7.54 (m, 1H), 7.32 – 7.24 (m, 4H), 7.20 (t, J = 6.4 Hz, 1H), 6.84 (d, J = 4.8 Hz, 2H), 6.76 (td, J = 11.4, 4.7 Hz, 1H), 6.18 (dt, J = 15.5, 4.0 Hz, 1H), 5.83 (dt, J = 8.7, 4.4 Hz, 1H), 5.74 (dd, J = 11.3, 4.7 Hz, 1H), 5.36 (d, J = 5.3 Hz, 1H), 4.77 (dt, J = 8.2, 6.5 Hz, 1H), 4.58 (dt, J = 10.5, 5.1 Hz, 1H), 4.49 (dq, J = 11.9, 4.5 Hz, 1H), 4.35 (d, J = 12.1 Hz, 1H), 4.30 (d, J = 12.1 Hz, 1H), 4.09 (d, J = 3.6 Hz, 1H), 3.87 (dd, J = 27.6, 4.5 Hz, 3H), 3.82 – 3.68 (m, 8H), 3.56 – 3.40 (m, 4H), 3.28 (dt, J = 14.4, 4.6 Hz, 1H), 3.04 (ddd, J = 14.8, 10.4, 4.5 Hz, 1H), 2.99 (t, J = 4.4 Hz, 1H), 2.79 (d, J = 4.3 Hz, 1H), 2.47 (dd, J = 15.1, 8.3 Hz, 1H), 2.31 (t, J = 7.6 Hz, 2H), 2.09 (s, 4H), 1.94 – 1.87 (m, 2H), 1.80 (td, J = 12.5, 5.7 Hz, 1H), 1.69 (s, 3H), 1.66 (d, J = 7.6 Hz, 1H), 1.56 (dt, J = 11.2, 6.0 Hz, 3H), 1.35 – 1.31 (m, 2H), 1.19 (d, J = 4.2 Hz, 1H), 1.05 (q, J = 5.4 Hz, 6H), 0.81 (d, J = 4.7 Hz, 3H). LCMS [M+Na]+expected: 1095.5, observed: 1095.3 LCMS [M+H]+expected: 1073.5, observed 1073.4. Scheme 2Steps 1-2: Synthesis of Compound X2

[0507] In a center draining 1.5 mL vial, roridin A (20.4 mg, 38.3 µmol) was dissolved in tetrahydrofuran (383 µL) and cooled to -78 °C. At -78 °C, potassium tert-butoxide (5.59 mg, 1.3 eq., 49.8 µmol) was added and stirred for 5 minutes, then the reaction was charged with [({[(9H- fluoren-9-yl)methyl](oxycarbonylamino)}methyl)carbonylamino]methyl acetate (28.2 mg, 2 eq., 76.6 µmol) and stirred for 10 minutes at -78 °C. The reaction was then warmed to 0 °C and stirred for 1 hour. The reaction was quenched with solid NH4Cl (50 mg) and diluted with ethyl acetate (1 mL). The solution was filtered through a Cellite plug and concentrated in vacuo. The crude reaction was dissolved in anhydrous acetonitrile (0.4 mL). The solution was charged with piperidine (3.79 µL, 38.3 µmol) and stirred for 13 hours at ambient temperature. The reaction was concentrated in vacuo then passed through a silica plug (1 in.) using ethyl acetate then 10% v / v methanol / CH2Cl2to yield Compound X2 (10.3 mg, 14.2 µmol) in 37% yield over 2 steps with 85% purity LCMS 254nm. Step 3: Synthesis of Compound X4 (DL-41)

[0508] Compound X2 (10 mg, 13.3 µmol) was transferred to an oven dried center draining 1.5 mL vial using DMF (100 μL). The vial was charged with Compound X3 (7.51 mg, 1.2 eq., 15.9 µmol), 1-hydroxy-7-azabenzotriazole (1.8 mg, 13.3 µmol), and diisopropylamine (4.63 µL, 2eq., 26.5 µmol) and stirred with a triangle shaped stir bar. To the ambient temperature solution, HATU (5.04 mg, 13.3 µmol) was added. The reaction was quenched with NaHCO3(aq)(0.5 mL) and extracted with ethyl acetate (1ml x 3). The organic solution was washed with brine, dried over Na2SO4and concentrated under vacuum. Then purified by flash column chromatography (10% MeOH in DCM) and HPLC to deliver Compound X4 (DL-41)(6.5 mg, 6.06 µmol) in 60% yield as a white solid.1H NMR (600 MHz, Acetone) δ 8.07 (t, J = 5.8 Hz, 1H), 7.92 (q, J = 5.4 Hz, 2H), 7.78 – 7.72 (m, 2H), 7.62 – 7.54 (m, 1H), 7.32 – 7.24 (m, 4H), 7.20 (t, J = 6.4 Hz, 1H), 6.84 (d, J = 4.8 Hz, 2H), 6.76 (td, J = 11.4, 4.7 Hz, 1H), 6.18 (dt, J = 15.5, 4.0 Hz, 1H), 5.83 (dt, J = 8.7, 4.4 Hz, 1H), 5.74 (dd, J = 11.3, 4.7 Hz, 1H), 5.36 (d, J = 5.3 Hz, 1H), 4.77 (dt, J = 8.2, 6.5 Hz, 1H), 4.58 (dt, J = 10.5, 5.1 Hz, 1H), 4.49 (dq, J = 11.9, 4.5 Hz, 1H), 4.35 (d, J = 12.1 Hz, 1H), 4.30 (d, J = 12.1 Hz, 1H), 4.09 (d, J = 3.6 Hz, 1H), 3.87 (dd, J = 27.6, 4.5 Hz, 3H), 3.82 – 3.68 (m, 8H), 3.56 – 3.40 (m, 4H), 3.28 (dt, J = 14.4, 4.6 Hz, 1H), 3.04 (ddd, J = 14.8, 10.4, 4.5 Hz, 1H), 2.99 (t, J = 4.4 Hz, 1H), 2.79 (d, J = 4.3 Hz, 1H), 2.47 (dd, J = 15.1, 8.3 Hz, 1H), 2.31 (t, J = 7.6 Hz, 2H), 2.09 (s, 4H), 1.94 – 1.87 (m, 2H), 1.80 (td, J = 12.5, 5.7 Hz, 1H), 1.69 (s, 3H), 1.66 (d, J = 7.6 Hz, 1H), 1.56 (dt, J = 11.2, 6.0 Hz, 3H), 1.35 – 1.31 (m, 2H), 1.19 (d, J = 4.2 Hz, 1H), 1.05 (q, J = 5.4 Hz, 6H), 0.81 (d, J = 4.7 Hz, 3H). LCMS [M+Na]+expected: 1095.5, observed: 1095.3 LCMS [M+H]+expected: 1073.5, observed 1073.4. Example 1.2: Synthesis of Compound Y3 SchemeStep 1: Synthesis of Compound Y1

[0509] In an oven dried conical based 2 mL vial, roridin E (40 mg, 77.7 µmol) and ({[allyl(oxycarbonylamino)]methyl}carbonylamino)methyl acetate (35.8 mg, 2 eq., 155 µmol) in tetrahydrofuran (2.6 mL, 32 mmol) was added with pyridinium p-toluenesulfonate (1.95 mg, 0.1 eq., 7.77 µmol) at 0 °C. The mixture was stirred for 0.5 h at 0 °C. The reaction was slowly warm up to 40°C and stirred for 6 h. The mixture was purified by flash column chromatography (50% ethyl acetate in hexanes) to deliver Compound Y1 (14 mg, 20.4 µmol) in 26% yield (35% yield BRSM) as a white solid and recovery of Roridin E 10 mg. LCMS [M+H]+expected: 685.3, observed: 685.3. Step 2: Synthesis of Compound Y2

[0510] Compound Y1 (14 mg, 20.4 µmol) in dichloromethane (701 µL, 11 mmol) was added tetrakis(triphenylphosphine)palladium (0) (2.36 mg, 0.1 eq., 2.04 µmol) and phenylsilane (3.02 µL, 1.2 eq., 24.5 µmol). The mixture was stirred at room temperature for 1 h under argon. The mixture was concentrated and purified by flash column chromatography to deliver Compound Y2 (12 mg, 20 µmol) in 98% yield as a white solid. LCMS [M+H]+expected: 601.3 observed: 601.3. Step 3: Synthesis of Compound Y3 (DL-46)

[0511] Compound Y2 (14 mg, 23.3 µmol) was transferred to an oven dried center draining 1.5 mL vial using dimethylformamide (1.47 mL, 18.9 mmol). The vial was charged with Compound X3 (13.2 mg, 1.2 eq., 28 µmol) , 1-hydroxy-7-azabenzotriazole (3.17 mg, 23.3 µmol), and diisopropylamine (8.14 µL, 2 eq., 46.6 µmol) and stirred with a triangle shaped stir bar. To the ambient temperature solution, HATU (8.86 mg, 23.3 µmol) was added. The reaction was quenched with NaHCO3(aq)0.5 ml and extracted with ethyl acetate (3 ml x 3). The organic layer was washed with brine, dried over anhydrous sodium sulfate, and concentrated under vacuum. Then purified by flash column chromatography (10% MeOH in DCM) and HPLC to deliverCompound Y3 (DL-46) (11.6 mg, 11 µmol) in 47% yield as a white solid.1H NMR (600 MHz, MeOD) δ 7.35 – 7.28 (m, 1H), 7.27 – 7.19 (m, 4H), 7.19 – 7.14 (m, 1H), 6.75 (s, 2H), 6.62 (t, J = 11.4 Hz, 1H), 6.02 (dd, J = 15.6, 3.1 Hz, 1H), 5.95 (dd, J = 8.3, 4.1 Hz, 1H), 5.77 (s, 1H), 5.65 (d, J = 11.2 Hz, 1H), 5.45 (s, 1H), 5.43 – 5.37 (m, 1H), 4.71 (s, 2H), 4.57 (s, 1H), 4.49 (dd, J = 9.2, 5.8 Hz, 1H), 4.40 (d, J = 12.5 Hz, 1H), 4.03 (dt, J = 5.4, 2.5 Hz, 1H), 3.88 (d, J = 17.0 Hz, 1H), 3.85 – 3.81 (m, 2H), 3.80 (m, 4H), 3.75 (s, 1H), 3.74 – 3.67 (m, 3H), 3.53 (dt, J = 8.9, 6.3 Hz, 1H), 3.44 (t, J = 7.1 Hz, 2H), 3.27 (p, J = 1.7 Hz, 6H), 3.21 – 3.15 (m, 1H), 3.02 (d, J = 4.0 Hz, 1H), 2.97 (dd, J = 14.0, 9.3 Hz, 1H), 2.82 (d, J = 4.0 Hz, 1H), 2.47 (dd, J = 15.3, 8.2 Hz, 1H), 2.39 (t, J = 5.9 Hz, 2H), 2.23 (q, J = 3.1 Hz, 4H), 2.04 – 1.84 (m, 4H), 1.81 (dd, J = 13.2, 5.4 Hz, 1H), 1.69 (s, 3H), 1.57 (dp, J = 39.8, 7.5 Hz, 4H), 1.31 – 1.26 (m, 2H), 1.00 (d, J = 6.3 Hz, 3H), 0.76 (s, 3H). LCMS [M+Na]+expected: 1077.5 observed: 1077.3.

[0512] Compounds DL-1 to DL-40 and DL-41 to DL-84 in Table 2 were prepared analogously with the general procedures as disclosed herein starting from the appropriate starting material. Table 2. Representative Drug-Linker CompoundsCharacterization of Drug-LinkersExample 2: General Conjugation Procedure I Scheme

[0513] Prior to conjugation, phosphate buffer solution (PBS) (pH = 7.4) was filtered through a 0.2 micron filter. A 10 mM solution of tris(2-carboxyethyl)phosphine hydrochloride (TCEP) in degassed ultra-pure grade water (sparged with argon and sonicated for 15 minutes at 30 °C). mAb (5 mg / mL, PBS, pH = 7.4) was warmed to 37 °C using an aluminum block or water bath. The head space of the vial was flushed with argon and the reaction vessel charged with 8 equiv. of TCEP. The reaction was incubated for 2 hours at 37 °C. The reaction was cooled to ambient temperature then charged with 14 equiv. of a Drug-Linker disclosed herein. The reaction was incubated at ambient temperature for 2 hours or ambient temperature for 1 hour then 4 °C for 18 hours. The resulting solution was purified using PD-10 buffer exchange gravity columns and filtered through a 0.2 micron filter providing an ADC with a DAR 0<8. Aggregation was determined by size-exclusion chromatography using a XBridgeTMPremier Protein SEC 250Å 2.5 μm 7.8 x 300 mm column and PBS (pH =7.4) as the mobile phase and integration at 280 nm. Example 2.1: Conjugation of Compound X4 – DAR 8.0 Trastuzumab (Conjugate 1 (C-1) )

[0514] Prepared according to General Conjugation Procedure I on a 0.2 to 30 mg scale using Drug-Linker Compound X4 and Trastuzumab afforded the desired product: DAR 8.0 Trastuzumab-mc-GGFG-am-roridin A (Conjugate 1). Example 2.2: Conjugation of Compound X4 – DAR 1.9 Trastuzumab (Conjugate 2 (C-2) )

[0515] Prepared according to General Conjugation Procedure I on a 0.2 to 30 mg scale using 6 equiv. of Drug-Linker Compound X4, 3 equiv. of TCEP, and Trastuzumab afforded the desired product: DAR 1.9 Trastuzumab-mc-GGFG-am-roridin A (Conjugate 2). Example 2.3: Conjugation of Compound X4 – DAR 8.0 Sacituzumab (Conjugate 3 (C-3) )

[0516] Prepared according to General Conjugation Procedure I on a 0.2 to 30 mg scale using Drug-Linker Compound X4 and Sacituzumab afforded the desired product: DAR 8.0 Sacituzumab-mc-GGFG-am-roridin A (Conjugate 3). Example 2.4 Conjugation of Compound Y3 – DAR 8.0 Trastuzumab (Conjugate 4 (C-4) )Prepared according to General Conjugation Procedure I on a 0.2 to 30 mg scale using Drug- Linker Compound Y3 and Trastuzumab afforded the desired product: DAR 8.0 Trastuzumab- mc-GGFG-am-roridin E (Conjugate 4).Example 2.5 Conjugation of Compound Y3 – DAR 3.1 Trastuzumab (Conjugate 5 (C-5) )

[0517] Prepared according to General Conjugation Procedure I on a 0.2 to 30 mg scale using 5 equiv. of Drug-Linker Compound Y3, 3 equiv. of TCEP, and Trastuzumab afforded the desired product: DAR 3.1 Trastuzumab-mc-GGFG-am-roridin E (Conjugate 5).

[0518] Conjugates 6 to 147 (C-6 to C-147) in Table 3 were prepared analogously with the general procedures as disclosed herein starting from the appropriate starting material. Table 3. Representative ConjugatesExample 3: General procedure for drug-antibody-ratio determination

[0519] To an Eppendorf tube, 10 μL of ADC, 1 μL of PNGase F, and 1 μL of 10 mM TCEP were incubated at 37 °C for 30 minutes then diluted with 40 μL of LCMS grade water. The solution was centrifuged (13,100 rpm, 20 °C, 5 min). The supernatant was transferred to a 1.5 mL vial with HPLC insert. Drug-antibody-ratio (DAR) was analyzed using a SCIEX X500B QToF with a BioResolveTMRP mAb polyphenyl, 450Å, 2.7 μm 2.1 x 50 mm column as the stationary phase and water / acetonitrile + 0.1% formic acid as the mobile phase. DAR wasdetermined by the area of the peaks from the deconvoluted TIC spectra using the following formula:wherein: DAR = the drug-antibody-ratio of the ADC; %AreaLCnis the percent area of a contributing light chain conjugate containing n conjugates; %AreaHCnis the percent area of a contributing heavy chain conjugate containing n conjugates; and n=the number of conjugates present on the light chain or heavy chain of the ADC. Assay protocols Example 4: Cytotoxic Activity of ADCs in cell lines

[0520] The cytotoxic effect of anti-HER2 roridin A / E conjugates was tested in a panel of cancer cell lines with varying surface HER2 antigen expression levels, including NCI-N87 (gastric carcinoma, HER2 high), AU-565 (breast adenocarcinoma, HER2 high), Calu-3 (lung adenocarcinoma, HER2 high), MDA-MB-453 (breast carcinoma, HER2 medium), and MDA- MB-468 (breast carcinoma, HER2 negative). Cells were seeded at an appropriate density depending on the cell line (typically 3000 - 8000 cells per well) in 125 µl of appropriate cell culture media in 96-well plates. Cells were allowed to adhere for 18 - 24 hours at 37 °C in a 5% CO2 incubator and dosed with anti-HER2 roridin A / E conjugates at the starting concentration of 100 nM in a 10-point, 4-fold dilution curve. Cells were incubated for 120 hours at 37 °C in a 5% CO2 incubator. Cell viability was measured using CellTiter-Glo (Promega) by adding 125 µl of CellTiter-Glo reagent per well. Plates were shaken for 2 minutes and incubated for 10 minutes before the measurement of the luminescence signal in a plate reader (Promega GloMax).

[0521] The results are displayed in Table 4. Table 4. Conjugate Cytotoxic Activity – Cell Lineswhere for Table 4: <1 nM = +++, 1-10 nM = ++ and >10 nM = +. Example 5: Cytotoxic Activity of Drug / Payload Compounds in cell lines

[0522] The cytotoxic effect of compounds of Formula (III) (i.e. compounds from Table 1) were tested in a panel of cancer cell lines with varying surface HER2 antigen expression levels, including NCI-N87 (gastric carcinoma, HER2 high), AU-565 (breast adenocarcinoma, HER2 high), Calu-3 (lung adenocarcinoma, HER2 high), and MDA-MB-468 (breast carcinoma, HER2 negative). Cells were seeded at an appropriate density depending on the cell line (typically 3000 - 8000 cells per well) in 125 µl of appropriate cell culture media in 96-well plates. Cells were allowed to adhere for 18 - 24 hours at 37 °C in a 5% CO2 incubator and dosed with anti-HER2 roridin A / E conjugates at the starting concentration of 100 nM in a 10-point, 4-fold dilution curve. Cells were incubated for 120 hours at 37 °C in a 5% CO2 incubator. Cell viability was measured using CellTiter-Glo (Promega) by adding 125 µl of CellTiter-Glo reagent per well. Plates were shaken for 2 minutes and incubated for 10 minutes before the measurement of the luminescence signal in a plate reader (Promega GloMax).

[0523] Results are shown in Table 5. Table 5. Drug / Drug / Payload Compounds Cytotoxic Activity – Cell Lineswhere for Table 5: <10 nM = +++, 10-100 nM = ++ and >100 nM = +.

Claims

WHAT IS CLAIMED IS:

1. A Drug-Linker of Formula I:or a pharmaceutically acceptable salt thereof, wherein: each Y is independently a Spacer unit; y is selected from 0, 1, and 2; D is a Drug unit; each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1.

2. The Drug-Linker or salt of claim 1, wherein D is selected from a Trichothecene.

3. The Drug-Linker or salt of claim 1 or claim 2, wherein D is selected from, wherein E is absent or an Extender unit; X is selected from -N(R1)-, -O-, and heterocycle; R1is selected from hydrogen and C1-6alkyl; R2is selected from hydrogen and -OR10; R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, - S(O)2R20, -P(O)(OR20)2, -Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, - N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

4. The Drug-Linker or salt of claim 3, wherein the Drug-Linker of Formula I is represented by Formula I-RA-a*:or a pharmaceutically acceptable salt thereof.

5. The Drug-Linker or salt of claim 3, wherein the Drug-Linker of Formula I is represented by Formula I-RA-b*:or a pharmaceutically acceptable salt thereof.

6. The Drug-Linker or salt of claim 3, wherein the Drug-Linker of Formula I is represented by Formula I-RE*:or a pharmaceutically acceptable salt thereof.

7. The Drug-Linker or salt of any one of claims 3 to 6, wherein E is selected from C1-C20alkylene, C1-C20alkenylene, and C1-C20alkynylene,wherein one or more CH2units of the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, – C(O)N(R30)–, –S(O)2–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene, and 4- to 10-membered heterocyclene are each optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, oxo, -OR30, -N(R30)2, -C(O)R30, - C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C3-10carbocycle and 4- to 10- membered heterocycle are each optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle and 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)N(R30)2, - S(O)2(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; wherein the C3-10carbocycle and 4- to 10-membered heterocycle are each optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle and 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)(NH2), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, oxo, -OH, -CN, - NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a C3-C6carbocycle or 4- to 10-membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

8. The Drug-Linker or salt of of any one of claims 3 to 7, wherein E is selected from C1-C20alkylene,wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are each optionally substituted with one or more substituents independently selected from halogen, oxo, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

9. The Drug-Linker or salt of any one of claims 3 to 8, wherein E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -S(O)2R30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

10. The Drug-Linker or salt of any one of claims 3 to 9, wherein E is selected from11. The Drug-Linker or salt of any one of claims 3 to 10, wherein X is selected from12. The Drug-Linker or salt of any one of claims 3 to 11, wherein X is selected from13. The Drug-Linker or salt of any one of claims 3 to 12, wherein R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, - S(O)2OR20, -S(O)2R20, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

14. The Drug-Linker or salt of any one of claims 3 to 13, wherein R2 is selected from -OR10;R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -S(O)2N(R20)2, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, and 4- to 6-membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

15. The Drug-Linker or salt of any one of claims 3 to 14, wherein R2is selected from16. The Drug-Linker or salt of any one of claims 3 to 15, wherein R2is selected from17. The Drug-Linker or salt of any one of claims 3 to 6 or 11 to 16, wherein E is absent.

18. The Drug-Linker or salt of any one of claims 1 to 4 or 11 to 17, wherein the Drug-Linker of Formula I or Formula I-RA-a* is represented by Formula I-RA-a:or a pharmaceutically acceptable salt thereof.

19. The Drug-Linker or salt of any one of claims 1 to 3, 5, or 11 to 17, wherein the Drug- Linker of Formula I or Formula I-RA-b* is represented by Formula I-RA-b:or a pharmaceutically acceptable salt thereof.

20. The Drug-Linker or salt of any one of claims 1 to 3, 6 or 11 to 17, wherein the Drug- Linker of Formula I or Formula I-RE* is represented by Formula I-RE:or a pharmaceutically acceptable salt thereof.

21. The Drug-Linker or salt of any one of claims 1 to 20, wherein y is 1.

22. The Drug-Linker or salt of any one of claims 1 to 21, wherein Y is selected from.

23. The Drug-Linker or salt of any one of claims 1 to 20, wherein y is 0.

24. The Drug-Linker or salt of any one of claims 1 to 23, wherein w is 1.

25. The Drug-Linker or salt of any one of claims 1 to 24, wherein each W is independently selected from, ,26. The Drug-Linker or salt of any one of claims 1 to 25, wherein each W is independently27. The Drug-Linker or salt of any one of claims 1 to 26, wherein a is 1.

28. The Drug-Linker or salt of any one of claims 1 to 27, wherein A is selected from29. The Drug-Linker or salt of any one of claims 1 to 28, wherein A is selected from30. The Drug-Linker or salt of any one of claims 1 to 29, wherein the Drug-Linker is:or a pharmaceutically acceptable salt thereof.

31. The Drug-Linker or salt of any one of claims 1 to 29, wherein the Drug-Linker is:or a pharmaceutically acceptable salt thereof.

32. The Drug-Linker or salt of any one of claims 1 to 29, wherein the Drug-Linker is:or a pharmaceutically acceptable salt thereof.

33. The Drug-Linker or salt of any one of claims 1 to 29, wherein the Drug-Linker is selectedor a pharmaceutically acceptable salt of any one thereof.

34. The Drug-Linker or salt of any one of claims 1-29, wherein the Drug-Linker is selected from Table 2.

35. The Drug-Linker or or salt of any one of claims 1-29, wherein the Drug-Linker is selected from compound DL-1 to DL-84.

36. The Drug-Linker or salt of any one of claims 1 to 35, further comprising an antibody (Ab) to form a conjugate, wherein Ab is attached to A, wherein A has reacted and formed a covalent bond to Ab.

37. A Conjugate of Formula Ila:or a pharmaceutically acceptable salt thereof, wherein:Ab is an antibody or an antigen-binding portion thereof; each Y is independently a Spacer unit; y is selected from 0, 1, and 2; each D is a Drug unit; p is an integer from 1 to 20; each W is independently an Amino Acid unit; w is 0 to 12; each A is independently a Stretcher unit; and a is 0 or 1.

38. The conjugate or salt of claim 37, wherein D is selected from a Trichothecene.

39. The conjugate or salt of claims 37 or 38, wherein D is selected from, wherein E is absent or an Extender unit; X is selected from -N(R1)-, -O-, and heterocycle; R1is selected from hydrogen and C1-6alkyl; R2is selected from hydrogen and -OR10; R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, - S(O)2R20, -P(O)(OR20)2, -Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, - N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

40. The conjugate or salt of claim 39, wherein the Conjugate of Formula IIa is represented by Formula II-RA-a*:,or a pharmaceutically acceptable salt thereof.

41. The conjugate or salt of claim 39, wherein the Drug-Linker of Formula I is represented by Formula II-RA-b*:, or a pharmaceutically acceptable salt thereof.

42. The conjugate or salt of claim 39, wherein the Drug-Linker of Formula I is represented by Formula II-RE*:or a pharmaceutically acceptable salt thereof.

43. The conjugate or salt of any one of claims 39 to 42, wherein E is selected from C1-C20alkylene, C1-C20alkenylene, and C1-C20alkynylene, wherein one or more CH2units of the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)O–, – C(O)N(R30)–, –S(O)2–, or 4- to 10-membered heterocyclene, and wherein the C1-C20alkylene, C1-C20alkenylene, C1-C20alkynylene, and 4- to 10-membered heterocyclene are each optionally substituted with one or more substituents independently selected from halogen, oxo, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, - C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR20, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and4- to 10-membered heterocycle, wherein the C1-6alkyl, C3-10carbocycle and 4- to 10- membered heterocycle are each optionally substituted with one or more substituents independently selected from halogen, oxo, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, - NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle, 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)N(R30)2, - S(O)2(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; wherein the C3-10carbocycle and 4- to 10-membered heterocycle are each optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NHC1-6alkyl, -NH(C1-6aminoalkyl), -C(O)(OH), -NH(C=NH)NH2, -NHC(O)(C1-6alkyl), C3-10carbocycle and 4- to 10-membered heterocycle, -C(O)(C1-6alkyl), -C(O)(NH2), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, oxo, -OH, -CN, - NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a C3-C6carbocycle or 4- to 10-membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

44. The conjugate or salt of of any one of claims 39 to 43, wherein E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, - S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected fromhalogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

45. The conjugate or salt of any one of claims 39 to 44, wherein E is selected from C1-C20alkylene, wherein one or more CH2units of the C1-C20alkylene is each optionally and independently replaced by –N(R30)–, –O–, –C(O)–, –C(O)O–, –C(O)N(R30)–, –S(O)2–, or 4- to 10- membered heterocyclene, and wherein the C1-C20alkylene and 4- to 10-membered heterocyclene are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, C1-6haloalkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, -S(O)2R30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; each R30is independently selected from hydrogen and C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1- 6 alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

46. The conjugate or salt of any one of claims 39 to 45, wherein E is selected from, , , , ,47. The conjugate or salt of any one of claims 39 to 46, wherein X is selected from48. The conjugate or salt of any one of claims 39 to 47, wherein X is selected from49. The conjugate or salt of any one of claims 39 to 48, wherein R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, - S(O)2OR20, -S(O)2R20, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

50. The conjugate or salt of any one of claims 39 to 49, wherein R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -S(O)2N(R20)2, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, and 4- to 6-membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

51. The conjugate or salt of any one of claims 39 to 50, wherein R2is selected from52. The conjugate or salt of any one of claims 39 to 51, wherein R2is selected from53. The conjugate or salt of any one of claims 37 to 40 or 47 to 51, wherein E is absent.

54. The conjugate or salt of any one of claims 37 to 40 or 47 to 52, wherein the conjugate of Formula IIa or Formula II-RA-a* is represented by Formula II-RA-a:or a pharmaceutically acceptable salt thereof.

55. The conjugate or salt of any one of claims 37 to 39, 41 or 47 to 52, wherein the conjugate of Formula IIa or Formula II-RA-b* is represented by Formula II-RA-b:or a pharmaceutically acceptable salt thereof.

56. The conjugate or salt of any one of claims 37 to 39, 42, or 47 to 52, wherein the conjugate of Formula IIa or Formula II-RE* is represented by Formula II-RE:, or a pharmaceutically acceptable salt thereof.

57. The conjugate or salt of any one of claims 37 to 56, wherein y is 1.

58. The conjugate or salt of any one of claims 20 to 27, wherein Y is selected from,.

59. The conjugate or salt of any one of claims 37 to 56, wherein y is 0.

60. The conjugate or salt of any one of claims 37 to 59, wherein w is 1.

61. The conjugate or salt of any one of claims 37 to 60, wherein each W is independently62. The conjugate or salt of any one of claims 37 to 61, wherein each W is independently selected from, 63. The conjugate or salt of any one of claims 37 to 62, wherein a is 1.

64. The conjugate or salt of any one of claims 37 to 63, wherein A is selected from , and.

65. The conjugate or salt of any one of claims 37 to 64, wherein A is selected from.

66. The conjugate or salt of any one of claims 37 to 64, wherein the conjugate is represented by:or a pharmaceutically acceptable salt thereof.

67. The conjugate or salt of any one of claims 37 to 64, wherein the conjugate is representedor a pharmaceutically acceptable salt thereof.

68. The conjugate or salt of any one of claims 37 to 64, wherein the conjugate is represented by:or a pharmaceutically acceptable salt thereof.

69. The conjugate or salt of any one of claims 37 to 64, wherein the conjugate is selected from:.

70. The conjugate or salt of any one of claims 37 to 64, wherein the conjugate is selected from Table 3.

71. The conjugate or salt of any one of claims 37 to 64, wherein the conjugate is selected from compound C-1 to C-147, Ab is as defined in Table 3.

72. The conjugate or salt of any one of claims 37 to 64, wherein the conjugate is selected from Table AA.

73. The conjugate of any one of claims 37 to 69 or 72, wherein the Ab is selected from trastuzumab and Sacituzumab.

74. The conjugate of any one of claims 37 to 69, 72, or 73, wherein p is selected from 2 to 8.

75. The conjugate of any one of claims 37 to 69, or 72 to 74, wherein p is 4.

76. The conjugate of any one of claims 37 to 69, or 72 to 74, wherein p is 8.

77. A pharmaceutical composition comprising a conjugate of anyone of claims 37 to 76 and a pharmaceutically acceptable excipient.

78. A method of treating a disease, disorder, or condition, comprising administering to a subject in need thereof, a conjugate of any one of claims 37 to 76, or the pharmaceutical composition of claim 77.

79. The method of claim 78, wherein the disease, disorder, or condition is cancer.

80. A method of treating a tumor, comprising administering to a subject in need thereof, a conjugate of any one of claims 37 to 76, or the pharmaceutical composition of claim 78.

81. A compound represented by the structure of Formula (IIIa):or a pharmaceutically acceptable salt thereof, wherein: E1is selected from hydrogen and an End unit; X1is absent or selected from -N(R1)-, -O-, and heterocycle; R1is selected from hydrogen and C1-6alkyl; andP is selected fromR2is selected from hydrogen and -OR10; R10is selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, -C(O)R20, - C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, -S(O)2OR20, -S(O)R20, - S(O)2R20, -P(O)(OR20)2, -Si(R20)3, -Si(R20)2(OR20), -Si(R20)2(OR20)2, -Si(OR20)3, C3-10carbocycle, and 4- to 10-membered heterocycle wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are each optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, - N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

82. The compound or salt of claim 81 wherein X1is absent and E1is azide.

83. The ompound or salt of claim 81 wherein X1is selected from -N(R1)-, -O-, and triazole.

84. The compound or salt of claim 81 or claim 83, wherein X1is selected from85. The compound or salt of any one of claims 81, 83, or 84, wherein E1is selected from hydrogen, C1-10alkyl, C2-10alkenyl, C2-10alkynyl, -C(O)R30, -C(O)N(R30)2, -C(O)OR30, - S(O)2N(R30)2, -S(O)2OR30, -S(O)R30, -S(O)2R30, -P(O)(OR30)2, -Si(R30)3, -Si(R30)2(OR30), -Si(R30)2(OR30)2, and -Si(OR30)3, wherein one or more CH2units of the C1-10alkyl, C2-10alkenyl, C2-10alkynyl are each optionally and independently replaced by ––N(R30)–, –O–, –C(O)–, –C(O)N(R30)–, or –S(O)2–, andwherein the C1-10alkyl, C2-10alkenyl, and C2-10alkynyl are optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, - C(O)R30, -C(O)OR30, -C(O)N(R30)2, -N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, - S(O)2OR30, -S(O)R30, -S(O)2R30, -(C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; each R30is independently selected from hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C2-8alkenyl, C2-8alkynyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, - NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

86. The compound or salt of any one of claims 81 or 83 to 85, wherein E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)– or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), - C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independentlyselected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), - C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl.

87. The compound or salt of any one of claims 83 to 86, wherein E1is selected from C1-10alkyl, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––N(R30)– or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from F, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, C3-6carbocycle and 5- to 9-membered heterocycle, wherein the C3-6carbocycle and 5- to 9-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 7- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 7-membered heterocycle are optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from F, Cl, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

88. The compound or salt of any one of claims 83 to 87, wherein E1is selected from89. The compound or salt of any one of claims 81, 83, or 84, wherein E1is selected from C1-10alkyl and -C(O)R30; wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O– or –C(O)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), - C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), - C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independentlyselected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl.

90. The compound or salt of any one of claims any one of claims 81, 83, 84, or 89, wherein E1is selected from C1-10alkyl and -C(O)R30; wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O– or –C(O)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)2R30, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and - O-C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

91. The compound or salt of any one of claims any one of claims 81, 83, 84, 89, or 90, wherein E1is selected from92. The compound or salt of any one of claims 81, 83, or 84, wherein E1is selected from C1- 10alkyl and -C(O)R30, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by ––C(O)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -C(O)R30; and R30is selected from C3-10carbocycle and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, -NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl.

93. The compound or salt of any one of claims 81, 83, 84, or 92, wherein E1is selected from-C(O)R30; and R30 is selected from C3-10 carbocycle and 4- to 10-membered heterocycle, whereinthe C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, - NH(C1-6aminoalkyl), -C(O)(C1-6alkyl), -C(O)(C1-6aminoalkyl), C1-6alkyl, -C1-6haloalkyl, and - O-C1-6alkyl.

94. The compound or salt of any one of claims 81, 83, 84, 92, or 93, wherein E1is selected from.

95. The compound or salt of any one of claims 81, 83, or 84, wherein E1is selected from selected from C1-10alkyl, -S(O)2OR30, -S(O)R30, -S(O)2N(R30)2, and -S(O)2R30, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –S(O)2–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from halogen, C1-6alkyl, -OR30, -N(R30)2, -C(O)R30, -C(O)OR30, -C(O)N(R30)2, - N(R30)C(O)R30, -S(O)2N(R30)2, -N(R30)S(O)2R30, -S(O)2OR30, -S(O)R30, -S(O)2R30, - (C=NR30)N(R30)2, -NR30(C=NR30)N(R30)2, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, -C1-6haloalkyl, and -O-C1-6alkyl; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl.

96. The compound of any one of claims 81, 83, 84, or 95, wherein E1is selected from selected from C1-10alkyl, -S(O)2OR30, and -S(O)2N(R30)2, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –S(O)2–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -N(R30)2, -C(O)OR30, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, - CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

97. The compound or salt of any one of claims 81, 83, 84, 95, 96, wherein E1is selected from98. The compound or salt of any one of claims 81, 83, or 84, wherein E1is selected from selected from selected from C1-10alkyl and -C(O)N(R30)2, wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, -C(O)R30, -–C(O)O–, -C(O)N(R30)2, and -N(R30)C(O)R30; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O- C1-6alkyl; or two R30come together with the atom to which they are attached to the atom to form a 4- to 10- membered heterocycle optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

99. The compound or salt of any one of claims 81, 83, 84, or 98, wherein E1is selected from C1-10alkyl and -C(O)N(R30)2,wherein one or more CH2units of the C1-10alkyl are each optionally and independently replaced by –O–, –N(R30)–, or –C(O)N(R30)–, and wherein the C1-10alkyl is optionally substituted with one or more substituents independently selected from -OR30, -N(R30)2, and –C(O)O–; each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle and 4- to 10- membered heterocycle, wherein the C1-8alkyl is optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

100. The compound or salt of any one of claims 81, 83, 84, 98, or 99, wherein E1is selected from.

101. The compound or salt of any one of claims 81, 83, or 84, wherein E1is selected from - Si(R30)3, -Si(R30)2(OR30), -Si(R30)2(OR30)2, and -Si(OR30)3; and each R30is independently selected from hydrogen, C1-8alkyl, C3-10carbocycle, and 4- to 10-membered heterocycle, wherein the C1-8alkyl, C3-10carbocycle and 4- to 10-membered heterocycle are optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, - NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

102. The compound or salt of any one of claims 81, 83, 84, or 101, wherein E1is selected from -Si(R30)3; and each R30is independently selected from C1-8alkyl optionally substituted with one or more substituents independently selected from halogen, -OH, -CN, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

103. The compound or salt of any one of claims 81, 83, 84, 101, or 102, wherein E1is.

104. The compound or salt of any one of claims 81, 83, or 84, wherein E1is hydrogen.

105. The compound or salt of any one of claims 81 to 104, wherein E1is selected fromhydrogen,106. The compound or salt of any one of claims 81 to 105, wherein R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -C(O)OR20, -S(O)2N(R20)2, - S(O)2OR20, -S(O)2R20, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, C3-10carbocycle, and 4- to 10- membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NO2, -NH2, -N(C1-6alkyl)2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

107. The compound or salt of any one of claims 81 to 106, wherein R2is selected from -OR10; R10is selected from hydrogen, C1-6alkyl, -C(O)R20, -C(O)N(R20)2, -S(O)2N(R20)2, and -Si(R20)3, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl; and each R20is independently selected from hydrogen, C1-6alkyl, and 4- to 6-membered heterocycle, wherein the C1-6alkyl is optionally with one or more substituents independently selected from halogen, -OH, -CN, -NH2, C1-6alkyl, C1-6haloalkyl, and -O-C1-6alkyl.

108. The compound or salt of any one of claims 81 to 107, wherein R2is selected from109. The compound or salt of any one of claims 81 to 108, wherein the compound is selected from Table 1A and Table 1B.

110. The compound or salt of any one of claims 81 to 108, wherein the compound is selected from compound PA-1 to compound PA-294 and compound PB-1.

111. A pharmaceutical composition comprising a compound of any one of claims 81 to 110 and a pharmaceutically acceptable excipient.

112. A method of treating a disease, disorder, or condition, comprising administering to a subject in need thereof, a compound of any one of claims 81 to 110, or the pharmaceutical composition of claim 111.

113. The method of claim 112, wherein the disease, disorder, or condition is cancer.

114. A method of treating a tumor, comprising administering to a subject in need thereof, a compound of any one of claims 81 to 110 or the pharmaceutical composition of claim 111.

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