Linkers, drug linkers and conjugates thereof and methods of using the same

Abstract

lt provides linker compounds, or stereoisomers or salts thereof, including (a) a linker unit having from 1 to 4 attachment sites for a drug unit and having one of the following structures (i) or (ii): (b) at least one polar group containing a polymer unit, optionally a sugar unit, optionally a carboxyl unit, and combinations thereof; and (c) optionally a stretcher group having an attachment site for a targeting group, wherein a-is an attachment site to an enzyme- cleavable group; (3-is an attachment site to the at least one polar group; 6-is H, an attachment site to at least one of the drug unit, or an attachment site to a linking group attached to the at least one of the drug unit. It also provides drug-linker compounds and conjugates formed from linker compounds, as well as related pharmaceutical compositions and methods.

Description

(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (43) International Publication Date 18 July 2024 (18.07.2024) llllllllllllllllllllllllllllllllllllllllllll (10) International Publication Number WO 2024 / 149345 Al WIPO I PCT (51) International Patent Classification: A61K47 / 65 (2017.01) A61K47 / 61 (2017.01) A61K 47 / 60 (2017.01) C07H 5 / 06 (2006.01) A61K 47 / 54 (2017.01) A61P35 / 00 (2006.01) A61K 47 / 56 (2017.01) (21) International Application Number: PCT / CN2024 / 071901 (22) International Filing Date: 11 January 2024 (11.01.2024) (25) Filing Language: English (26) Publication Language: English (30) Priority Data: PCT / CN2023 / 071778 11 January 2023 (11.01.2023) CN (71) Applicant: PROFOUNDBIO US CO. [US / US]; 14241 NE Woodinville-Duvall Rd. #228, Woodinville, Washing­ ton 98072 (US). (72) Inventors: LIU, Haidong; Suite 101 & 102, Bldg 1, P3 A 1 Xinze Street, SIP, Suzhou, Jiangsu 215123 (CN). WANG, Guobao; Suite 101 & 102, Bldg 1, P3A 1 Xinze Street, SIP, Suzhou, Jiangsu 215123 (CN). JIANG, Xiaolong; Suite 101 & 102, Bldg 1, P3A 1 Xinze Street, SIP, Suzhou, Jiangsu 215123 (CN). SHANG, Xiao; 14241 NE Wood­ inville-Duvall Rd. #228, Woodinville, Washington 98072 (US). (74) Agent: METIS IP (CHENGDU) LLC; Room 401, 4th Floor, Unit 1 of Building 1, No. 269 North Section of Hu- pan Road, Tianfu New District, China Free Trade Zone (Sichuan), Chengdu, Sichuan 610213 (CN). (81) Designated States (unless otherwise indicated, for every kind of national protection available)'. AE, AG, AL, AM, (54) Title: LINKERS, DRUG LINKERS AND CONJUGATES THEREOF AND METHODS OF USING THE SAME OVCAR-3 w o 20 24 / 1 49 34 5 A l llll llll llll llll llll llll llll llll llll lll̂ FIG. 1 (57) Abstract: It provides linker compounds, or stereoisomers or salts thereof, including (a) a linker unit having from 1 to 4 attachment sites for a drug unit and having one of the following structures (i) or (ii): (b) at least one polar group containing a polymer unit, optionally a sugar unit, optionally a carboxyl unit, and combinations thereof; and (c) optionally a stretcher group having an attachment site for a targeting group, wherein a-is an attachment site to an enzyme- cleavable group; (3-is an attachment site to the at least one polar group; 6-is H, an attachment site to at least one of the drug unit, or an attachment site to a linking group attached to the at least one of the drug unit. It also provides drug-linker compounds and conjugates formed from linker compounds, as well as related pharmaceutical compositions and methods. [Continued on next page] WO 2024 / 149345 Al IIIIIIIIIIIIIIIIIIIIIIIIIIIIM AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, BZ, CA, CH, CL, CN, CO, CR, CU, CV, CZ, DE, DJ, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IQ, IR, IS, IT, JM, JO, JP, KE, KG, KH, KN, KP, KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, MG, MK, MN, MU, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, WS, ZA, ZM, ZW. (84) Designated States (unless otherwise indicated, for every kind of regional protection available)'. ARIPO (BW, CV, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SC, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, ME, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG). Published: — with international search report (Art. 21(3)) — with sequence listing part of description (Rule 5.2(a)) WO 2024 / 149345 PCT / CN2024 / 071901 LINKERS, DRUG LINKERS AND CONJUGATES THEREOF AND METHODS OF USING THE SAME CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to International Application No. PCT / CN2023 / 071778 filed on January 11, 2023, the entire contents of which are hereby incorporated by reference. BACKGROUND

[0002] A great deal of interest has surrounded the use of monoclonal antibodies (mAbs) for the targeted delivery of cytotoxic agents to cells associated with disease, such as cancer cells and other cells, in the form of antibody drug conjugates (or ADCs). The design of antibody drug conjugates, by attaching a cytotoxic agent, immune modulatory agent or other agent (collectively a “drug”) to an antibody, typically via a linker, involves consideration of a variety of factors. These factors include the identity and location of the chemical group for attachment of the drug, the mechanism of drug release, the structural element(s) (if any) providing release of the drug, and structural modification of the released free drug, if any. If the drug is released in the extracellular environment, the released form of the drug must able to reach its target. If the drug is to be released after antibody internalization, the structural elements and mechanism of drug release must be consonant with the intracellular trafficking of the conjugate.

[0003] Another important factor in the design of antibody drug conjugates is the amount of drug that can be delivered per targeting group (i.e., the number of drugs attached to each targeting group (e.g., an antibody), referred to as the drug load or drug loading). Historically, assumptions were that higher drugs loads were superior to lower drug loads (e.g., 8-loads vs 4-loads). The rationale was that higher loaded conjugates would deliver more drug (e.g., cytotoxic agent) to the target cells. This rationale was supported by the observations that conjugates with higher drug loadings were more active against cell lines in vitro. Certain later studies revealed, however, that this assumption was not confirmed in animal models. Conjugates having drug loads of 4 or 8 of certain auristatins were observed to have similar activities in mouse models. See, e.g., Hamblett et al., Clinical Cancer Res. 10:7063-70 (2004). Hamblett et al. further reported that the higher loaded ADCs were cleared more quickly from circulation in animal models. This faster clearance suggested a PK liability for higher loaded species as compared to lower loaded species. See Hamblett et al. In addition, higher loaded conjugates had lower maximum tolerated doses (MTDs) in mice, and as a result had narrower reported therapeutic indices. Id. In contrast, ADCs with a drug loading of 2 at engineered sites in a monoclonal antibody were reported to have the same or better PK and therapeutic indices as compared to certain 4-loaded ADCs. For example, see Junutula et al., Clinical Cancer Res. 16:4769 (2010). Thus, recent trends are to develop ADCs with low drug loadings.

[0004] There is a need, therefore, for antibody drug conjugate formats (and more generally for formats for other conjugates), that allow for higher drug loading, but that maintain other characteristics of lower loaded conjugates, such as favorable PK properties. Surprisingly, the present invention addresses those needs. 1 WO 2024 / 149345 PCT / CN2024 / 071901 SUMMARY

[0005] Provided herein are Linkers having hydrophilic characteristics that maintain the intrinsic properties of antibodies conjugated with the Linkers and drugs. In particular, the Linkers aid in maintaining the hydrophilic properties of the antibodies when conjugated at higher drug loading and / or to hydrophobic drugs and other agents. Also provided are Drug-Linkers and conjugates comprising the Linkers, as well as methods of using such conjugates for the treatment of cancer and other diseases.

[0006] In some embodiments, provided are Linker compounds, or a stereoisomers or salts thereof, comprising: (a) a Linker unit having from 1 to 4 attachment sites for a Drug unit and having one of the following structures (i) or (ii): (b) at least one Polar group comprising a Polymer unit, optionally a Sugar unit, optionally a Carboxyl unit, and combinations thereof; and (c) optionally a Stretcher group having an attachment site for a Targeting group; wherein: a— is an attachment site to an enzyme-cleavable group; β— is an attachment site to the at least one Polar group; δ— is H, an attachment site to at least one of the Drug units, or an attachment site to a linking group attached to the at least one of the Drug units; the Polymer unit comprises a polyamide, a polyether, or a combination thereof, wherein the polyether comprises a hydroxyl group, a polyhydroxyl group, a sugar group, a carboxyl group, or combinations thereof; each Ra independently is H or Ci-Ce alkyl; each Rb independently is halo, Ci-6 alkyl, an attachment site to at least one of the Drug units, or an attachment site to at least one of the Polar groups; x is 0, 1, 2, 3 or 4; y is 0, 1, 2 or 3; Rc is a bond, -C(O)-, -S(O)-, -SO2-, C1-6 alkylene, C1-6 alkynylene, triazolyl or combinations thereof; and Y is a bond, -O-, -S-, -N(Ra)-, -C(O)-, -S(O)-, -SO2-Ci-C6 alkylene, Ci-C6 alkenylene, Ci-C6 alkynylene, triazolyl, a group containing triazolyl, or combinations thereof.

[0007] In some embodiments, provided are Drug-Linker compounds, comprising a Linker compound 2 WO 2024 / 149345 PCT / CN2024 / 071901 described herein with at least one Drug unit attached via the attachment site.

[0008] In some embodiments, provided are Conjugates comprising a Targeting group attached to a Drug-Linker compound described herein.

[0009] In some embodiments, provided are pharmaceutical compositions comprising a Conjugate described herein and a pharmaceutically acceptable carrier.

[0010] In some embodiments, provided are methods of treating a subject in need thereof, comprising administering to the subject a conjugate described herein or a pharmaceutical composition described herein, wherein the subject has cancer or an autoimmune disease and the conjugate binds to a target antigen associated with the cancer or autoimmune disease.

[0011] These and other aspects of the present invention may be more fully understood by reference to the following detailed description, non-limiting examples of specific embodiments and the appended drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against OVCAR-3;

[0013] Figure 2 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against PA-1;

[0014] Figure 3 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against NCI-H292;

[0015] Figure 4 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against MDA-MB-468;

[0016] Figure 5 is a graph comparing mean fluorescence intensity versus concentration for in vitro mAbs and ADCs binding to OVCAR-3 cells;

[0017] Figure 6 is a graph comparing cell viability versus concentration for ADCs on OVCAR-3 cells;

[0018] Figure 7 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against NCI-H441;

[0019] Figure 8 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against HCC4006;

[0020] Figure 9 is a graph comparing mean fluorescence intensity versus concentration for in vitro mAbs and ADCs binding to CFPAC-1 cells;

[0021] Figure 10 is a graph comparing mean fluorescence intensity versus concentration for in vitro mAbs and ADCs binding to PC-3 cells;

[0022] Figure 11 is a graph comparing viability versus concentration for ADCs on CFPAC-1;

[0023] Figure 12 is a graph comparing viability versus concentration for ADCs on PC-3;

[0024] Figure 13 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against CFPAC-1; and

[0025] Figure 14 is a graph comparing tumor volume versus treatment time for in vivo tests of antitumor agents against PC-3. 3 WO 2024 / 149345 PCT / CN2024 / 071901 DEFINITIONS

[0026] For convenience, certain terms in the specification, examples and claims are defined here. Unless stated otherwise, or implicit from context, the following terms and phrases have the meanings provided below. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0027] As used herein and unless otherwise indicated, the terms "a" and "an" are taken to mean "one," "at least one" or "one or more". Unless otherwise required by context, singular terms used herein shall include pluralities and plural terms shall include the singular.

[0028] Unless the context requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

[0029] The terms "decreased," "reduce," "reduced," "reduction," "decrease," and "inhibit" are all used herein generally to mean a decrease by a statistically significant amount relative to a reference.

[0030] The terms "increased," "increase," or "enhance," or "activate" are all used herein to generally mean an increase by a statically significant amount relative to a reference.

[0031] As used herein, the terms "protein" and "polypeptide" are used interchangeably herein to designate a series of amino acid residues each connected to each other by peptide bonds between the alpha-amino and carboxyl groups of adjacent residues. The terms "protein" and "polypeptide" also refer to a polymer of amino acids, including modified amino acids (e.g., phosphorylated, glycated, glycosylated, etc.) and amino acid analogs, regardless of its size or function. "Protein" and "polypeptide" are often used in reference to relatively large polypeptides, whereas the term "peptide" is often used in reference to small polypeptides, but usage of these terms in the art overlaps. The terms "protein" and "polypeptide" are used interchangeably herein when referring to an encoded gene product and fragments thereof. Thus, exemplary polypeptides or proteins include gene products, naturally occurring proteins, homologs, orthologs, paralogs, fragments and other equivalents, variants, fragments, and analogs of the foregoing.

[0032] As used herein, an "epitope" refers to the amino acids conventionally bound by an immunoglobulin VH / VL pair, such as the antibodies, antigen binding portions thereof and other binding agents described herein. Other binding agents comprise non-antibody scaffolds. An epitope can be formed on a polypeptide from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of a protein. Epitopes formed from contiguous amino acids are typically retained on exposure to denaturing solvents, whereas epitopes formed by tertiary folding are typically lost on treatment with denaturing solvents. An epitope typically includes at least 3, and more usually, at least 5, about 9, or about 8-10 amino acids in a unique spatial conformation. An epitope defines the minimum binding site for an antibody, antigen binding portions thereof and other binding agent, and thus represents the target of specificity of an antibody, antigen binding portion thereof or other immunoglobulin-based binding agent. In the case of a single domain antibody, an epitope represents the unit of structure bound by a variable domain in isolation. 4 WO 2024 / 149345 PCT / CN2024 / 071901

[0033] As used herein, "specifically binds" refers to the ability of a binding agent (e.g., an antibody or antigen binding portion thereof) described herein to bind to a target with a KD of 10-5 M (10000 nM) or less, e.g., 10-6 Μ, 10-7 Μ, 10-8 Μ, 10-9 Μ, 10'10 Μ, 10-11 Μ, 10-12 M, or less. “Specifically binds” as stated herein also refers to the ability of a molecule (e.g., an antibody or antigen binding portion thereof or non-antibody scaffold) described herein to bind to a target with a KD of 10-5 M (10000 nM) or less, e.g., 10-6 Μ, 10-7 Μ, 10-8 Μ, 10-9 Μ, 1010 Μ, 1011 Μ, 1012 M, or less. Specific binding can be influenced by, for example, the affinity and avidity of the antibody, antigen binding portion or other binding agent and the concentration of target polypeptide. A person of ordinary skill in the art can determine appropriate conditions under which antibodies, antigen binding portions and other binding agents described herein selectively bind to a target molecule using any suitable methods, such as titration of an antibody or a binding agent in a suitable cell binding assay. A binding agent specifically bound to a target molecule is not displaced by a non-similar competitor. In certain embodiments, an antibody or antigen-binding portion thereof or other binding agent is said to specifically bind to a target molecule when it preferentially recognizes its target molecule in a complex mixture of proteins and / or macromolecules. Specific binding can be influenced by, for example, the affinity and avidity of the antibody, antigen binding portion or non-antibody scaffold and the concentration of target polypeptide. A person of ordinary skill in the art can determine appropriate conditions under which antibodies, antigen binding portions and non-antibody scaffolds described herein selectively bind to a target molecule using any suitable methods, such as titration of an antibody or a non-antibody scaffold in a suitable cell binding assay. A molecule specifically bound to a target molecule is not displaced by a non-similar competitor. In certain embodiments, an antibody or antigen-binding portion thereof or non-antibody scaffold is said to specifically bind to a target molecule when it preferentially recognizes its target molecule in a complex mixture of proteins and / or macromolecules.

[0034] Unless otherwise indicated, the term "alkyl" by itself or as part of another term refers to a substituted or unsubstituted straight chain or branched, saturated hydrocarbon having the indicated number of carbon atoms (e.g., "-C1-C5 alkyl," "-Ci-Cs alkyl," or "-C1-C10" alkyl refer to an alkyl group having from 1 to 5,1 to 8, or 1 to 10 carbon atoms, respectively). Examples include methyl (Me, - CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, - CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-l-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(CH3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n- pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl- 2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-l-butyl (- CH2CH2CH(CH3)2), 2-methyl-l-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2- hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (- C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH(CH3)CH2CH3), 4-methyl-2-pentyl (- CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (- CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), and 3,3-dimethyl-2-butyl (- CH(CH3)C(CH3)3.

[0035] Unless otherwise indicated, "alkenyl" by itself or as part of another term refers to a C2-C8 5 WO 2024 / 149345 PCT / CN2024 / 071901 substituted or unsubstituted straight chain or branched, hydrocarbon with at least one site of unsaturation (i.e., a carbon-carbon, sp2 double bond). Examples include, but are not limited to: ethylene or vinyl (-CH=CH2), allyl (-CH2CH=CH2), cyclopentenyl (-C5H7), and 5-hexenyl (- CH2CH2CH2CH2CH=CH2).

[0036] Unless otherwise indicated, "alkynyl" by itself or as part of another term refers to a refers to C2-C8, substituted or unsubstituted straight chain or branched, hydrocarbon with at least one site of unsaturation (i.e., a carbon-carbon, sp triple bond. Examples include, but are not limited to: acetylenic and propargyl.

[0037] Unless other indicated, "alkylene" refers to a saturated, branched or straight chain or hydrocarbon radical of 1-8 carbon atoms, and having two monovalent radical centers derived by the removal of two hydrogen atoms from the same or two different carbon atoms of a parent alkane. Typical alkylene radicals include, but are not limited to: methylene (-CH2-), 1,2-ethyl (-CH2CH2-), 1,3- propyl (-CH2CH2CH2-), 1,4-butyl (-CH2CH2CH2CH2-), and the like.

[0038] Unless otherwise indicated, "alkenylene" refers to an unsaturated, branched or straight chain hydrocarbon radical of 2-8 carbon atoms, and having two monovalent radical centers derived by the removal of two hydrogen atoms from the same or two different carbon atoms of a parent alkene. Typical alkenylene radicals include, but are not limited to: 1,2-ethylene (-CH=CH-).

[0039] Unless otherwise indicated, "alkynylene" refers to an unsaturated, branched or straight chain or cyclic hydrocarbon radical of 2-8 carbon atoms, and having two monovalent radical centers derived by the removal of two hydrogen atoms from the same or two different carbon atoms of a parent alkyne. Typical alkynylene radicals include, but are not limited to: acetylene, propargyl, and 4- pentynyl.

[0040] Unless otherwise indicated, the term "heteroalkyl," by itself or in combination with another term, refers to a substituted or unsubstituted stable straight or branched chain hydrocarbon, or combinations thereof, saturated and from one to ten, preferably one to three, heteroatoms selected from the group consisting of Ο, N, Si and S, and wherein the nitrogen and sulfur atoms may optionally be oxidized and the nitrogen heteroatom may optionally be quaternized. The heteroatom(s) Ο, N and S may be placed at any interior position of the heteroalkyl group (i.e., as part of the main chain) or at the position at which the alkyl group is attached to the remainder of the molecule. The heteroatom Si may be placed at any position of the heteroalkyl group, including the position at which the alkyl group is attached to the remainder of the molecule. Examples of heteroalkyl include the following: -CH2CH2OCH3, -CH2CH2NHCH3, -CH2CH2N(CH3)CH3, - CH2SCH2CH3, CH2CH2S(O)CH3, -CH2CH2S(O)2CH3, and -Si(CH3)3. Up to two heteroatoms may be consecutive, such as, for example, -CH2NHOCH3 and CH2OSi(CH3)3. In some embodiments, a Ci to C4 heteroalkyl has 1 to 4 carbon atoms and 1 or 2 heteroatoms and a Ci to C3 heteroalkyl has 1 to 3 carbon atoms and 1 or 2 heteroatoms.

[0041] Unless otherwise indicated, the terms "heteroalkenyl" and “heteroalkynyl” by themselves or in combination with another term, refers to a substituted or unsubstituted stable straight or branched chain alkenyl or alkynyl having from one to ten, preferably one to three, heteroatoms selected from the group consisting of Ο, N, Si and S, and wherein the nitrogen and sulfur atoms may optionally be 6 WO 2024 / 149345 PCT / CN2024 / 071901 oxidized and the nitrogen heteroatom may optionally be quaternized. The heteroatom(s) Ο, N and S may be placed at any interior position of a heteroalkenyl or heteroalkynyl group (i.e., as part of the main chain) or at the position at which the alkyl group is attached to the remainder of the molecule. The heteroatom Si may be placed at any position of a heteroalkenyl or heteroalkynyl group, including the position at which the alkyl group is attached to the remainder of the molecule.

[0042] Unless otherwise indicated, the term "heteroalkylene" by itself or as part of another substituent refers to a substituted or unsubstituted divalent group derived from a heteroalkyl (as discussed above), as exemplified by -CH2CH2SCH2CH2- and -CH2SCH2CH2NHCH2-. In some embodiments, a Ci to C4 heteroalkylene has 1 to 4 carbon atoms and 1 or 2 heteroatoms and a Ci to C3 heteroalkylene has 1 to 3 carbon atoms and 1 or 2 heteroatoms. For heteroalkylene groups, heteroatoms can also occupy either or both of the chain termini. Still further, for alkylene and heteroalkylene linking groups, no orientation of the linking group is implied.

[0043] Unless otherwise indicated, the terms "heteroalkenylene" and “heteroalkynylene" by themselves or as part of another substituent refers to a substituted or unsubstituted divalent group derived from an heteroalkenyl or heteroalkynyl (as discussed above). In some embodiments, a C2 to C4 heteroalkenylene or heteroalkynylene has 1 to 4 carbon atoms. For heteroalkenylene and heteroalkynylene groups, heteroatoms can also occupy either or both of the chain termini. Still further, for alkylene and heteroalkenylene and heteroalkynylene linking groups, no orientation of the linking group is implied.

[0044] Unless otherwise indicated, a "C3-C8 carbocycle," by itself or as part of another term, refers to a substituted or unsubstituted 3-, 4-, 5-, 6-, 7- or 8-membered monovalent, substituted or unsubstituted, saturated or unsaturated non-aromatic monocyclic or bicyclic carbocyclic ring derived by the removal of one hydrogen atom from a ring atom of a parent ring system. Representative -C3- C8 carbocycles include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentadienyl, cyclohexyl, cyclohexenyl, 1,3-cyclohexadienyl, 1,4-cyclohexadienyl, cycloheptyl, 1,3- cycloheptadienyl, 1,3,5-cycloheptatrienyl, cyclooctyl, and cyclooctadienyl.

[0045] Unless otherwise indicated, a "C3-C8 carbocyclo," by itself or as part of another term, refers to a substituted or unsubstituted Cs-Cs carbocycle group defined above wherein another of the carbocycle groups' hydrogen atoms is replaced with a bond (i.e., it is divalent).

[0046] Unless otherwise indicated, a "C3-C10 carbocycle," by itself or as part of another term, refers to a substituted or unsubstituted 3-, 4-, 5-, 6-, 7-, 8-, 9- or 10-membered monovalent, substituted or unsubstituted, saturated or unsaturated non-aromatic monocyclic, bicyclic or tricyclic carbocyclic ring derived by the removal of one hydrogen atom from a ring atom of a parent ring system. Representative -C3-C10 carbocycles include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentadienyl, cyclohexyl, cyclohexenyl, 1,3-cyclohexadienyl, 1,4-cyclohexadienyl, cycloheptyl, 1,3-cycloheptadienyl, 1,3,5-cycloheptatrienyl, cyclooctyl, and cyclooctadienyl. -C3-C10 carbocycles can further include fused cyclooctyne carbocycles, such as the fused cyclooctyne compounds disclosed in International Publication Number WO2011 / 136645 (the disclosure of which is incorporated by reference herein), including BCN (bicyclo[6.1.0]nonyne) and DBCO (Dibenzocyclooctyne). 7 WO 2024 / 149345 PCT / CN2024 / 071901

[0047] Unless otherwise indicated, a "C3-C8 heterocycle," by itself or as part of another term, refers to a substituted or unsubstituted monovalent substituted or unsubstituted aromatic or non-aromatic monocyclic or bicyclic ring system having from 3 to 8 carbon atoms (also referred to as ring members) and one to four heteroatom ring members independently selected from N, Ο, P or S, and derived by removal of one hydrogen atom from a ring atom of a parent ring system. One or more N, C or S atoms in the heterocycle can be oxidized. The ring that includes the heteroatom can be aromatic or nonaromatic. Unless otherwise noted, the heterocycle is attached to its pendant group at any heteroatom or carbon atom that results in a stable structure. Representative examples of a C3- Cs heterocycle include, but are not limited to, pyrrolidinyl, azetidinyl, piperidinyl, morpholinyl, tetrahydrofuranyl, tetrahydro pyranyl, benzofuranyl, benzothiophene, indolyl, benzopyrazolyl, pyrrolyl, thiophenyl (thiophene), furanyl, thiazolyl, imidazolyl, pyrazolyl, pyrimidinyl, pyridinyl, pyrazinyl, pyridazinyl, isothiazolyl, and isoxazolyl. Unless otherwise indicate, the term “heterocarbocycle” is synonymous with the terms “heterocycle” or “heterocyclo” as described herein.

[0048] Unless otherwise indicated, "C3-C8 heterocyclo," by itself or as part of another term, refers to a substituted or unsubstituted C3-Ce heterocycle group defined above wherein one of the heterocycle group's hydrogen atoms is replaced with a bond (i.e., it is divalent).

[0049] Unless otherwise indicated, "aryl" by itself or as part of another term, means a substituted or unsubstituted monovalent carbocyclic aromatic hydrocarbon radical of 6-20 carbon (preferably 6-14 carbon) atoms derived by the removal of one hydrogen atom from a single carbon atom of a parent aromatic ring system. Some aryl groups are represented in the exemplary structures as "Ar". Typical aryl groups include, but are not limited to, radicals derived from benzene, substituted benzene, naphthalene, anthracene, biphenyl, and the like. An exemplary aryl group is a phenyl group.

[0050] Unless otherwise indicated, an "arylene" by itself or as part of another term, is an unsubstituted or substituted aryl group as defined above wherein one of the aryl group's hydrogen atoms is replaced with a bond (i.e., it is divalent) and can be in the ortho, meta, or para orientations.

[0051] Unless otherwise indicated, “heteroaryl" and "heterocycle" refer to a ring system in which one or more ring atoms is a heteroatom, e.g., nitrogen, oxygen, and sulfur. A heterocycle radical comprises 1 to 20 carbon atoms and 1 to 3 heteroatoms selected from N, Ο, P, and S. A heterocycle may be a monocycle having 3 to 7 ring members (2 to 6 carbon atoms and 1 to 3 heteroatoms selected from N, Ο, P, and S) or a bicycle having 7 to 10 ring members (4 to 9 carbon atoms and 1 to 3 heteroatoms selected from N, Ο, P, and S), for example: a bicyclo [4,5], [5,5], [5,6], or [6,6] system.

[0052] Unless otherwise indicated, an "heteroarylene" by itself or as part of another term, is an unsubstituted or substituted heteroaryl group as defined above wherein one of the heteroaryl group's hydrogen atoms is replaced with a bond (i.e., it is divalent).

[0053] Unless otherwise indicated, “carboxyl” refers to COOH or COO'M+, where M+ is a cation.

[0054] Unless otherwise indicated, “oxo” refers to (C=O).

[0055] Unless otherwise indicated, "substituted alkyl" and "substituted aryl" mean alkyl and aryl, respectively, in which one or more hydrogen atoms are each independently replaced with a substituent. Typical substituents include, but are not limited to, -X, -R10, -O', -OR10, -SR10, -S; - 8 WO 2024 / 149345 PCT / CN2024 / 071901 nr 102, -nr 103, =nr 10, -cx 3, -cn , -ocn , -scn , -n =c=o , -ncs , -no , -no 2, =n 2, -n 3, - NR10C(=O)R10, -C(=O)R10, -C(=O)NR102, -SO3-, -SO3H, -S(=O)2R10, -OS(=O)2OR10, -S(=O)2NR10, - S(=O)R10, -OP(=O)(OR10)2, -P(=O)(OR10)2, -PO-3, -PO3H2, -AsO2H2, -C(=O)R10, -C(=O)X, -C(=S)R10, -CO2R10, -CO2-, -C(=S)OR10, C(=O)SR10, C(=S)SR10, C(=O)NR102, C(=S)NR102, or C(=NR10)NR102, where each X is independently a halogen: -F, -Cl, -Br, or -I; and each R10 is independently -H, -Ci- C20 alkyl, -C6-C20 aryl, -C3-Ci4 heterocycle, a protecting group or a prodrug moiety. Typical substitutents also include (=O). Alkylene, carbocycle, carbocyclo, arylene, heteroalkyl, heteroalkylene, heterocycle, and heterocyclo groups as described above may also be similarly substituted.

[0056] Unless otherwise indicated, “polyhydroxyl group” refers to an alkyl, alkylene, carbocycle or carbocyclo group including two or more, or three or more, substitutions of hydroxyl groups for hydrogen on carbon atoms of the carbon chain. In some embodiments, a polyhydroxyl group comprises at least three hydroxyl groups. In some embodiments, a polyhydroxyl group comprises carbon atoms containing only one hydroxyl group per carbon atom. A polyhydroxyl group may contain one or more carbon atoms that are not substituted with hydroxyl. A polyhydroxyl group may have each carbon atom substituted with a hydroxyl group. Examples of polyhydroxyl group includes linear (acyclic) or cyclic forms of monosaccharides such as C6 or C5 sugars, such as glucose, ribose, galactose, mannose, arabinose, 2-deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose, talose, aldose, and ketose, sugar acids such as gluconic acid, aldonic acid, uronic acid or ulosonic acid, and an amino sugars, such as glucosamine, N-acetyl glucosamine, galactosamine, and N-acetyl galactosamine. In some embodiments, polyhydroxyl group includes linear or cyclic forms of disaccharides and polysaccharides.

[0057] Unless otherwise indicated by context, "optionally substituted" refers to an alkyl, alkenyl, alkynyl, alkylaryl, arylalkyl heterocycle, aryl, heteroaryl, alkylheteroaryl, heteroarylalkyl, or other substituent, moiety or group as defined or disclosed herein wherein hydrogen atom(s) of that substituent, moiety or group has been optionally replaced with different moiety(ies) or group(s), or wherein an alicyclic carbon chain that comprise one of those substituents, moiety or group is interrupted by replacing carbon atom(s) of that chain with different moiety(ies) or group(s). In some aspects an alkene function group replaces two contiguous sp3 carbon atoms of an alkyl substituent, provided that the radical carbon of the alkyl moiety is not replaced, so that the optionally substituted alkyl is an unsaturated alkyl substituent.

[0058] Optional substituent replacing hydrogen(s) in any of the foregoing substituents, moieties or groups is independently selected from the group consisting of aryl, heteroaryl, hydroxyl, alkoxy, aryloxy, cyano, halogen, nitro, fluoroalkoxy, and amino, including mono-, di- and tri-substituted amino groups, and the protected derivatives thereof, or is selected from the group consisting of -X, - OR', -SR' , -NH2, -N(R')(R”), -N(R”)3, =NR, -CX3, -CN, -NO2, - NR'C(=O)H, -NR'C(=O)R, - NR'C(=O)R”, -C(=O)R', -C(=O)NH2, -C(=O)N(R')R”, -S(=O)2R”, -S(=O)2NH2, -S(=O)2N(R’)R”, - S(=O)2NH2, -S(=O)2N(R')R”, -S(=O)2OR', -S(=O)R’, -OP(=O)(OR')(OR”), -OP(OH)3, - P(=O)(OR')(OR”), -PO3H2, -C(=O)R’, -C(=S)R”, -CO2R', -C(=S)OR”, -C(=O)SR', -C(=S)SR’, - C(=S)NH2, -C(=S)N(R')(R”)2, -C(=NR')NH2, -C(=NR')N(R')R”, and salts thereof, wherein each X is 9 WO 2024 / 149345 PCT / CN2024 / 071901 independently selected from the group consisting of a halogen: -F, -Cl, -Br, and -I; and wherein each R'is independently selected from the group consisting of C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C24 aryl, C3-C24 heterocyclyl (including C5-C24 heteroaryl), a protecting group, and a prodrug moiety or two of R” together with the heteroatom to which they are attached defines a heterocyclyl; and R' is hydrogen or R”, wherein R” is selected from the group consisting of C1-C20 alkyl, C6- C24 aryl, C3-C24 heterocyclyl (including C5-C24 heteroaryl), and a protecting group.

[0059] Typically, optional substituents are selected from the group consisting of -X, -OH, -OR", -SH, -SR", -NH2, -NH(R"), -NR'(R")2i -N(R")3, =NH, =NR”, -CX3, -CN, -NO2, -NR'C(=O)H, NR'C(=O)R", - CO2H, -C(=O)H, -C(=O)R", -C(=O)NH2, -C(=O)NR'R - -S(=O)2R", -S(=O)2NH2, -S(=O)2N(R')R", - S(=O)2NH2, - S(=O)2N(R')(R"), -S(=O)2OR', -S(=O)R”, -C(=S)R", -C(=S)NH2, -C(=S)N(R')R", - C(=NR')N(R")2, and salts thereof, wherein each X is independently selected from the group consisting of-F and -Cl, R" is typically selected from the group consisting of Ci-Ce alkyl, Ce-Cio aryl, C3-C10 heterocyclyl (including C5-C10 heteroaryl), and a protecting group; and R' independently is hydrogen, Ci-Ce alkyl, Ce-Cio aryl, C3-C10 heterocyclyl (including C5-C10 heteroaryl), and a protecting group, independently selected from R". More typically, substituents are selected from the group consisting of -X, -R", -OH, -OR", -NH2, -NH(R"), -N(R")2, -N(R")3, -CX3, -NO2, -NHC(=O)H, - NHC(=O)R“, -C(=O)NH2, -C(=O)NHR", -C(=O)N(R")2, -CO2H, -CO2R", -C(=O)H, -C(=O)R", - C(=O)NH2, -C(=O)NH(R"), -C(=O)N(R")2, -C(=NR')NH2, -C(=NR')NH(R"), -C(=NR')N(R")2, a protecting group and salts thereof, wherein each X is -F, R" is independently selected from the group consisting of Ci-C6 alkyl, C6-Cio aryl, C5-C10 heteroaryl and a protecting group; and R' is selected from the group consisting of hydrogen, Ci-Ce alkyl and a protecting group, independently selected from R".

[0060] The compounds of the invention, or their pharmaceutically acceptable salts may contain one or more asymmetric centers and may thus give rise to enantiomers, diastereomers, and other stereoisomeric forms that are defined, in terms of absolute stereochemistry, as (R) or (S) or, as (D) or (L) for amino acids. The present invention is meant to include all such possible isomers, as well as their racemic and optically pure forms. Optically active (+) and (), (R) and (S), or (D) and (L) isomers may be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques, for example, chromatography and fractional crystallization. Conventional techniques for the preparation / isolation of individual enantiomers include chiral synthesis from a suitable optically pure precursor or resolution of the racemate (or the racemate of a salt or derivative) using, for example, chiral high pressure liquid chromatography (HPLC). When the compounds described herein contain olefinic double bonds or other centres of geometric asymmetry, and unless specified otherwise, it is intended that the compounds include both E and Z geometric isomers. Likewise, all tautomeric forms are also intended to be included.

[0061] A “stereoisomer” refers to a compound made up of the same atoms bonded by the same bonds but having different three-dimensional structures, which are not interchangeable. The present invention contemplates various stereoisomers and mixtures thereof and includes “enantiomers,” which refers to two stereoisomers whose molecules are nonsuperimposeable mirror images of one another. The present invention also includes “diastereomers,” which refers to two or more stereoisomers of a compound that have different configurations at one or more of the equivalent 10 WO 2024 / 149345 PCT / CN2024 / 071901 stereocenters and are not mirror images of each other.

[0062] Although structures shown throughout the specification are depicted with specific stereocenters, the specification should be read to include variations in those stereocenters. For example, the structure of exatecan may be shown in the (S,S) configuration, but the (R,S) diastereomer of exatecan is also envisioned as being found in a separate embodiment of a conjugate as described herein.

[0063] Unless otherwise indicated, the term “Drug unit” or drug refers to cytotoxic agents (such as chemotherapeutic agents or drugs), immunomodulatory agents, nucleic acids (including siRNAs), growth inhibitory agents, toxins (e.g., protein toxins, enzymatically active toxins of bacterial, fungal, plant, or animal origin, or fragments thereof), radioactive isotopes, PROTACs and other compounds that are active against target cells when delivered to those cells.

[0064] Unless otherwise indicated, the term “Polymer unit” refers to a polymeric moiety composed of repeating subunits. Examples of polymer units include polyamides and polyethers. In some embodiments, the Polymer unit is selected from an optionally substituted polyamide, a substituted polyether, or combinations thereof. In further embodiments, the Polymer unit is selected from / θ Ra Rb\ \ r7(i) an optionally substituted polyamide comprising the formula ' / n0, or a stereoisomer thereof, wherein each Ra is independently H or Ci-6 alkyl and each Rb is independently H or Ci-6 alkyl, and n° is independently 2-26; H / Rb O RA Fo+W \ Rb Rb RA (ii) a substituted polyether comprising the formula ' / n0, or a stereoisomer thereof, wherein each Rb is independently H or Ci-6 alkyl, and n° is independently 2-26; or (iii) combinations thereof.

[0065] Unless otherwise indicated, the term “Sugar unit” or “sugar group” refers to a carbohydrate group. Examples of sugar units include glycosides.

[0066] Unless otherwise indicated, the term “Carboxyl unit” or “carboxyl group” refers to a group including a carbonyl group [-C(O)-], a carboxyl group [-CO2H], and / or a carboxylate group [-CO2M, M refers to a cationic counterion],

[0067] Unless otherwise indicated, the term “Stretcher group” refers to a linking moiety that connects the Targeting group to the enzyme-cleavable group.

[0068] Unless otherwise indicated, the term “polyamide” refers to polymeric groups composed of repeating subunits containing amide bonds.

[0069] Unless otherwise indicated, the term “polyether” refers to polymeric groups composed to repeating subunits containing ether bonds. Unless otherwise indicated, the term “enzyme-cleavable group” refers to a group that is cleavable by 11 WO 2024 / 149345 PCT / CN2024 / 071901 the action of a metabolic process or reaction inside a cell or in the extracellular milieu, whereby the covalent attachment between a Drug unit (e.g., a cytotoxic agent) and the Linker unit or portion thereof is broken, resulting in the free Drug unit, or a metabolite of the Linker unit-Drug, which is dissociated from the remainder of the Linker unit.

[0070] Unless otherwise indicated, the term “Targeting group” refers to a macromolecule, such a protein, polypeptide or peptide, that specifically binds to a target molecule. Examples of targeting groups include antibodies.

[0071] The phrase "pharmaceutically acceptable salt," as used herein, refers to pharmaceutically acceptable organic or inorganic salts of a compound (e.g., a Linker, Drug Linker, or a conjugate). The compound typically contains at least one amino group, and accordingly acid addition salts can be formed with this amino group. Exemplary salts include, but are not limited to, sulfate, citrate, acetate, oxalate, chloride, bromide, iodide, nitrate, bisulfate, phosphate, acid phosphate, isonicotinate, lactate, salicylate, acid citrate, tartrate, oleate, tannate, pantothenate, bitartrate, ascorbate, succinate, linleate, gentisinate, fumarate, gluconate, glucuronate, saccharate, formate, benzoate, glutamate, methanesulfonate, ethanesulfonate, benzenesulfonate, toluenesulfonate, and pamoate (i.e., l,l'-methylene-bis -(2-hydroxy-3- naphthoate)) salts. A pharmaceutically acceptable salt may involve the inclusion of another molecule such as an acetate ion, a succinate ion or other counterion. The counterion may be any organic or inorganic moiety that stabilizes the charge on the parent compound. Furthermore, a pharmaceutically acceptable salt may have more than one charged atom in its structure. Instances where multiple charged atoms are part of the pharmaceutically acceptable salt can have multiple counter ions. Hence, a pharmaceutically acceptable salt can have one or more charged atoms and / or one or more counterion.

[0072] As used herein, the term "consisting essentially of" refers to those elements required for a given embodiment. The term permits the presence of elements that do not materially affect the basic and novel or functional characteristic(s) of that embodiment.

[0073] As used herein, the term "consisting of" refers to compositions, methods, and respective components thereof as described herein, which are exclusive of any element not recited in that description of the embodiment.

[0074] Other than in the examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein should be understood as modified in all instances by the term "about." The term "about" when used in connection with percentages can mean + / -1%.

[0075] The terms "statistically significant" or "significantly" refer to statistical significance and generally mean a two standard deviation (2SD) difference, above or below a reference value.

[0076] Other terms are defined herein within the description of the various aspects of the invention. DETAILED DESCRIPTION

[0077] Provided herein are Linker compounds comprising a Linker unit, at least one Polar group, and optionally at least one of an enzyme-cleavable group and a Stretcher group. Such Linker compounds have hydrophilic characteristics that maintain the intrinsic properties of antibodies conjugated with the Linkers and drugs. In particular, the Linkers aid in maintaining the hydrophilic properties of the antibodies when conjugated at higher drug loading and / or to hydrophobic drugs and 12 WO 2024 / 149345 PCT / CN2024 / 071901 other agents.

[0078] In some embodiments, provided are a Linker compound, or a stereoisomer or salt thereof, comprising: (a) a Linker unit having from 1 to 4 attachment sites for a Drug unit and having one of the following structures (i) or (ii): (b) at least one Polar group comprising a Polymer unit, optionally a Sugar unit, optionally a Carboxyl unit, and combinations thereof; and (c) optionally a Stretcher group having an attachment site for a Targeting group; wherein: a— is an attachment site to an enzyme-cleavable group; β— is an attachment site to the at least one Polar group; δ— is H, an attachment site to at least one of the Drug units, or an attachment site to a linking group attached to the at least one of the Drug units; the Polymer unit comprises a polyamide, a polyether, or a combination thereof, wherein the polyether comprises a hydroxyl group, a polyhydroxyl group, a sugar group, a carboxyl group, or combinations thereof; each Ra independently is H or Ci-Ce alkyl; each Rb independently is halo, Ci-6 alkyl, an attachment site to at least one of the Drug units, or an attachment site to at least one of the Polar groups; x is 0, 1, 2, 3 or 4; y is 0, 1, 2 or 3; Rc is a bond, -C(O)-, -S(O)-, -SO2-, C1-6 alkylene, C1-6 alkynylene, triazolyl or combinations thereof; and Y is a bond, -O-, -S-, -N(Ra)-, -C(O)-, -S(O)-, -SO2-C1-C6 alkylene, Ci-Ce alkenylene, Ci-Ce alkynylene, a group containing triazolyl, or combinations thereof.

[0079] In some embodiments,the Linker unit has one of the following structures (i-a), or (ii-a), or (iii- 13 WO 2024 / 149345 PCT / CN2024 / 071901 Ο or a stereoisomer or salt thereof.

[0080] In some embodiments,wherein the Linker unit has one of the following structures (i-b), (i-c), (i-d), (i-e) or (i-f):

[0081] In some embodiments, the Linker unit has the following structure (ii-b) or (iii-b): 14 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer or salt thereof. Polar Groups

[0082] In some embodiments, provided are Linker compounds as described above, or stereoisomers or salts thereof, wherein the at least one Polar group comprises at least one Sugar unit having the following formula: L3-N(CH2- (CH(XR))k - X1(X2))2 (X) or a stereoisomer or salt thereof, wherein: each X is independently selected from NH and O; each R is independently selected from hydrogen, acetyl, a monosaccharide, a disaccharide, and a polysaccharide; each Xi is independently selected from CH2 and C(O); each X2 is independently selected from H, OH and OR; k is 1 to 10; and L3 is a point of attachment to a remainder of the Polar group.

[0083] In some embodiments, the at least one Sugar unit described above has one of the following structures (XII) or (XIII): (XIII) or a stereoisomer or salt thereof, wherein: each R is independently selected from hydrogen, a monosaccharide, a disaccharide and a polysaccharide; m is 1 to 8; and n is 0 to 4.

[0084] In some embodiments, provided are Linker compounds as described above, or stereoisomers or salts thereof, comprising a Polar group having a formula selected from: (a) ~R20-R21-[O-CH2-CH2]n20-R22-NR24R25 (XX) or a stereoisomer a salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or Ci-C3 alkylene; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; - C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted Ci-C3 alkylene C3-Cio carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; 15 WO 2024 / 149345 PCT / CN2024 / 071901 and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle, provided that R24 and R25 are not both H; and n20 is 2 to 26; or (b) ~R20-R21-[O-CH2-CH2]n20-R22-NR24R25 (XXI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-Ci0 carbocycle; optionally substituted Ci-C3 alkylene C3-Cio carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is a polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; and n20 is 2 to 26; or (c) ~R20-[-R26-[R29-[0-CH2-CH2-]n2oR29]n2i-R27-NR24R25] n27 (XXII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R26 and R27 are each optional and are, independently, selected from a bond, C1-C12 alkylene, -NH-Ci-Ci2 alkylene, -C1-C12 alkylene-ΝΗ-, -C1-C12 alkylene-N(CH3)-, -C(O)- C1-C12 alkylene, -C1-C12 alkylene-C(O)-, -NH-C1-C12 alkylene-C(O)- and -C(O)-Ci-Ci2 alkylene-NH-; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)- polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-Ci0 carbocycle; optionally substituted Ci-C3 alkylene C3-Cio carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)- R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)- polyhydroxyl group; optionally substituted C3-Cio carbocycle; optionally substituted Ci-C3 alkylene C3-Cio carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted - Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; or - NR24R25 together from a C3-C8 heterocycle, provided that R24 and R25 are not both H; each R29 is optional and independently selected from -C(O)-, -NH-, -C(O)-Ci-Ce alkylene-, -NH-Ci-Ce alkylene-, - Ci-Ce alkylene-ΝΗ-, -Ci-Ce alkylene-C(O)-, -NH(CO)-Ci-C6alkylene-, -N(CH3)-(CO)-Ci-C6alkylene-, - NH(CO)NH-, and triazole; n20 is 2 to 26; n21 is 1 to 4; and n27 is 1 to 4, or (d) -R20-R21-[-C(Ra)H-C(O)-N(RN)-]n20-R22-NR24R25 (XXIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 is a bond, Ci-C3 alkylene, -Ci-C3alkylene-[0-CH2-CH2-]n2o, -[CH2-CH2- O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[O-CH2-CH2-]n20-C(O)-; R22 is Ci-C3 alkylene, -Ci-C3alkylene- [0-CH2-CH2-]n2o, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[0-CH2-CH2-]n2o_C(0)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-Ce alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-Ci0 carbocycle; optionally substituted Ci-C3 alkylene C3-Cio carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; 16 WO 2024 / 149345 PCT / CN2024 / 071901 and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle, provided that R24 and R25 are not both H; and each n20 is independently 2 to 26, or (e) ~R20-R21-[-C(R^H-C(O)-N(RN)-]n20-R22-CO2 (XXIV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, C1-C3 alkylene, or -Ci- C3alkylene[0-CH2-CH2-]n2o; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-C6 alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-Cio carbocycle; optionally substituted Ci-C3 alkylene C3-Cio carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle, provided that R24 and R25 are not both H; R26 is H or Ci-C4 alkyl; and each n20 is independently 2 to 26,with the proviso that at least one Ra or RN is -R22-NR24R25; or (f) ~R20-R21-[C(Ra)H-C(O)-N(RN)-]n20-R22-N-(R23-NR24R25)2 (XXV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, Ci-C3 alkylene, or -Ci- C3alkylene-[0-CH2-CH2-]n2o; each Ra is independently H or -R22-NR24R25; each RN is independently H or Ci-Ce alkyl; each R23 is independently Ci-Ce alkylene; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-Cio carbocycle; optionally substituted Ci-C3 alkylene C3-Ci0 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle, provided that R24 and R25 are not both H; and each n20 is independently 2 to 26.

[0085] In some embodiments, provided are Linker compounds as described above, comprising a Polar group having a formula selected from: (a) ~R20-R21-[O-CH2-CH2]n20-R22-NR24R25 (XX) or a stereoisomer a salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or Ci-C3 alkylene; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; - C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII), provided that R24 and R25 are not both H; and n20 is 2 to 26; or (b) ~R20-R21-[O-CH2-CH2]n20-R22-NR24R25 (XXI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or Ci-C3 alkylene; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 17 WO 2024 / 149345 PCT / CN2024 / 071901 and R25 is a polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; and n20 is 2 to 26; (c) ~R20-[-R26-[R29-[0-CH2-CH2-]n2oR29]n2i-R27-NR24R25] n27 (XXII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R26 and R27 are each optional and are, independently, selected from a bond, Ci-Ci2 alkylene, -NH-Ci-Ci2 alkylene, -C1-C12 alkylene-ΝΗ-, -Ci-Ci2 alkylene-N(CH3)-, -C(O)- Ci-Ci2 alkylene, -C1-C12 alkylene-C(O)-, -NH-Ci-Ci2 alkylene-C(O)- and -C(O)-Ci-Ci2 alkylene-NH-; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)- polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -Ci-C8 alkyl; substituted - C(O)-Ci-Cs alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; - C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits, provided that R24 and R25 are not both H; each R29 is optional and independently selected from -C(O)-, -NH-, -C(O)-Ci-C6 alkylene-, -NH-Ci-C6 alkylene-, -Ci-C6 alkylene-ΝΗ-, -Ci-C6 alkylene-C(O)-, -NH(CO)-Ci- Cealkylene-, -N(CH3)-(CO)-Ci-C6alkylene-, -NH(CO)NH-, and triazole; n20 is 2 to 26; n21 is 1 to 4; and n27 is 1 to 4, or (d) ~R20-R21-[-C(Ra)H-C(O)-N(RN)-]n20-R22-NR24R25 (XXIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 is a bond, Ci-C3 alkylene, -Ci-C3alkylene-[0-CH2-CH2-]n2o, -[CH2-CH2- O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[0-CH2-CH2-]n2o-C(0)-; R22 is Ci-C3 alkylene, -Ci-C3alkylene- [O-CH2-CH2-]n20, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[O-CH2-CH2-]n20-C(O)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-C6 alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII), provided that R24 and R25 are not both H; and each n20 is independently 2 to 26, or (e) -R20-R21-[-C(Ra)H-C(O)-N(RN)-]n20-R22-CO2R26 (XXIV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, Ci-C3 alkylene, or -Ci- C3alkylene[0-CH2-CH2-]n2o; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-Cs alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII), provided that R24 and R25 are not both H; R26 is H or C1-C4 alkyl; and each n20 is independently 2 to 26,with the proviso that at least one Ra or RN is -R22- NR24R25; or (f) ~R20-R21-[C(Ra)H-C(O)-N(RN)-]n20-R22-N-(R23-NR24R25)2 (XXV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the 18 WO 2024 / 149345 PCT / CN2024 / 071901 enzyme-cleavable group; R21 and R22 are each, independently, a bond, C1-C3 alkylene, or -Ci- C3alkylene-[0-CH2-CH2-]n2o; each Ra is independently H or -R22-NR24R25; each RN is independently H or Ci-C6 alkyl; each R23 is independently Ci-C6 alkylene; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -Ci-Cs alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII), provided that R24 and R25 are not both H; and each n20 is independently 2 to 26.

[0086] In some embodiments, the Linker compound comprises a Polar group wherein both R24 and R25 are not H. For example, in some embodiments R24 and R25 are each independently selected from H and a polyhydroxyl group, provided that R24 and R25 are not both H.

[0087] In some embodiments, wherein the polyhydroxyl group as described above is a linear monosaccharide, optionally selected from a C6 or C5 sugar, a sugar acid and an amino sugar. In more specific embodiments, the polyhydroxyl group is a the C6 or C5 sugar is selected from glucose, ribose, galactose, mannose, arabinose, 2-deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose, talose, aldose, and ketose; or the polyhydroxyl group is a sugar acid is selected from gluconic acid, aldonic acid, uronic acid and ulosonic acid; or the polyhydroxyl group is an amino sugar is selected from glucosamine, N-acetyl glucosamine, galactosamine, and N-acetyl galactosamine.

[0088] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 19 WO 2024 / 149345 PCT / CN2024 / 071901 20 WO 2024 / 149345 PCT / CN2024 / 071901 21 WO 2024 / 149345 PCT / CN2024 / 071901 22 WO 2024 / 149345 PCT / CN2024 / 071901 OH HO,, J h %Aoh OH OH Α*ΟΗ A. J\ / Nx ho flfl fl 0H 0H| d 1 1 d 1 ϊ \ ^xA A A / N. A / \^N. A N T N T N T Jy 0 1 0 1 0 fl 0 ^N^ 1 ίϊ 1 II N T N T N X 0 1 o H fl o ^A 1 N 1 II\ χ"\ x A A , / \ Ax A / 0. N T N T N \A S 1 o H 1 0 ^Ν\ Η0"Ά, XNTN J ,H0 / II __ _ / < ΓΑ0 — Νχ J ηΧΛζΧ0Χ>>χ ,Χ0Χ.Α H o-J HO "VC™ z-Ja Hd'A-A HO dH °H HoA_oh x^°'x^^0 / ^x^°'x^^0 (T HO \~R39 HO )—7 / —( θΗ HO OH 0^ HO N—\ OH HO V M \—( ho y—\ o—< OH HO OH HO OH OH OHfl ,0H R3’ H0A >An h°A HO fl / OH ? / A / X—-X / 0H \M^x / νά̂ -ν n^tn \Ax r39 Z 0 O 23 WO 2024 / 149345 PCT / CN2024 / 071901 24 WO 2024 / 149345 PCT / CN2024 / 071901 25 WO 2024 / 149345 PCT / CN2024 / 071901 26 WO 2024 / 149345 PCT / CN2024 / 071901 wherein each R is independently H or alkyl; each R39 is independently selected from H, a linear monosaccharide and polyethylene glycol, optionally having from 1 to 24 ethylene glycol subunits; each n independently is 1-12; and the wavy line is an attachment site to Rb, or to the enzyme- cleavable group.

[0089] In some embodiments, one of R24 and R25 as described above is a linear monosaccharide and the other is a cyclic monosaccharide.

[0090] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 27 WO 2024 / 149345 PCT / CN2024 / 071901 OH wherein R41 is a cyclic monosaccharide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0091] In some embodiments, R24 and R25 as described above are independently a poluyhydroxyl selected from a cyclic monosaccharide, disaccharide and polysaccharide.

[0092] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 28 WO 2024 / 149345 PCT / CN2024 / 071901 wherein each R45 is selected from H and a monosaccharide, a disaccharide, or a polysaccharide; and R46 is selected from a cyclic monosaccharide, disaccharide, or polysaccharide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0093] In some embodiments, R24 and R25 as described above are independently selected from a linear monosaccharide and a substituted linear monosaccharide, wherein the substituted linear monosaccharide is substituted with a monosaccharide, a disaccharide or a polysaccharide.

[0094] In some embodiments, provided herein are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 29 WO 2024 / 149345 PCT / CN2024 / 071901 ΟΙ I wherein R47 is a linear monosaccharide; and each R49 is selected from a monosaccharide, a disaccharide and a polysaccharide; and the wavy line is an attachment site to Rb, or to the enzyme- cleavable group.

[0095] In some embodiments, R24 and R25 as described above are independently selected from a linear monosaccharide and a substituted monosaccharide, wherein the substituted linear monosaccharide is substituted with one or more substituents selected from alkyl, O-alkyl, aryl, O- aryl, carboxyl, ester, or amide, and optionally further substituted with a monosaccharide, disaccharide or a polysaccharide.

[0096] In some embodiments, R24 and R25 as described above are independently selected from a linear monosaccharide and a substituted monosaccharide, wherein the substituted linear monosaccharide is substituted with one or more substituents selected from carboxyl, ester, and amide, and optionally further substituted with a monosaccharide, disaccharide, or a polysaccharide.

[0097] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: o o o > O J >OH HO A* ,,OH O^OH wherein each R42 is independently selected from a linear monosaccharide and a substituted linear monosaccharide; each R43 is independently selected from alkyl, O-alkyl, aryl, O-aryl, carboxyl, ester, and amide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0098] In some embodiments, provided are Linker compounds comprising a Polar group selected 30 WO 2024 / 149345 PCT / CN2024 / 071901 from the following, or a stereoisomer or salt thereof: R42 OH HO ...OH oh and wherein each R42 is independently selected from a linear monosaccharide and a substituted linear monosaccharide; each R43 is independently selected from hydroxyl, carboxyl, ester, and amide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0099] In some embodiments, one of R24 and R25 as described above is a -C(O)-polyhydroxyl group or substituted -C(O)-polyhydroxyl group, and the other of R24 and R25 is a H, -C(O)-polyhydroxyl group, substituted -C(O)-polyhydroxyl group, polyhydroxyl group or substituted polyhydroxyl group; wherein the substituted -C(O)-polyhydroxyl group and polyhydroxyl group are substituted with a monosaccharide, a disaccharide, a polysaccharide, alkyl, -O-alkyl, aryl, carboxyl, ester, or amide.

[0100] In some embodiments, one of R24 and R25 as described above is a -C(O)-polyhydroxyl group or substituted -C(O)-polyhydroxyl group, and the other of R24 and R25 is a H, -C(O)-polyhydroxyl group, substituted -C(O)-polyhydroxyl group, polyhydroxyl group or substituted polyhydroxyl group; wherein the substituted -C(O)-polyhydroxyl group and polyhydroxyl group are substituted with a monosaccharide, a disaccharide, a polysaccharide, carboxyl, ester, or amide.

[0101] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: OH OH 31 WO 2024 / 149345 PCT / CN2024 / 071901 wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0102] In some embodiments, R24 and R25 as described above are independently selected from a H, substituted -Ci-Cs alkyl, substituted -C1-C4 alkyl or substituted -C1-C3 alkyl; provided that both R24 and R25 are not H; wherein substituted -Ci-Cs alkyl, -C1-C4 alkyl, and -C1-C3 alkyl are substituted with hydroxyl and / or carboxyl.

[0103] In some embodiments, R24 and R25 as described above are independently H or substituted - Ci-Cs alkyl; provided that both R24 and R25 are not H; wherein substituted -Ci-C8 alkyl is substituted with hydroxyl and / or carboxyl.

[0104] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 32 WO 2024 / 149345 PCT / CN2024 / 071901 OH O OH OH O wherein R48 is selected from H, OH, CH2OH, COOH or -Ci-C6 alkyl substituted with hydroxyl or carboxyl; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0105] In some embodiments, one of R24 and R25 as described above is selected from H, substituted -C(O)-Ci-C8 alkyl, substituted -C(O)-Ci-C4 alkyl, and substituted -C(O)-Ci-C3 alkyl and the other of R24 and R25 is selected from substituted -C(O)-Ci-C8 alkyl, substituted -C(O)-Ci-C4 alkyl, substituted -C(O)-Ci-C3 alkyl, substituted -Ci-Cs alkyl, substituted -Ci-C4 alkyl, and substituted -Ci- C3 alkyl, wherein substituted -C(O)-Ci-C8 alkyl, substituted -C(O)-Ci-C4 alkyl, substituted -C(O)-Ci- C3 alkyl, substituted -Ci-C8 alkyl, -Ci-C4 alkyl and -C1-C3 alkyl are substituted with hydroxyl and / or carboxyl.

[0106] In some embodiments, wherein one of R24 and R25 is H or substituted -C(O)-Ci-C8 alkyl, and the other of R24 and R25 is substituted -C(O)-Ci-C8 alkyl, or substituted -Ci-C8 alkyl, wherein substituted -C(O)-Ci-C8 alkyl and substituted -Ci-C8 alkyl, are substituted with hydroxyl and / or carboxyl.

[0107] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 33 WO 2024 / 149345 PCT / CN2024 / 071901 34 WO 2024 / 149345 PCT / CN2024 / 071901 Ο Ο wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0108] In some embodiments, R24 and R25 as described above are selected from H and optionally substituted aryl; provided that both R24 and R25 are not H.

[0109] In some embodiments, provided as Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0110] In some embodiments, R24 and R25 as described above together form an optionally substituted Ca-Cs heterocycle or heteroaryl.

[0111] In some embodiments, provided are Linker compounds comprising a Polar group having the following structure: or a stereoisomer or salt thereof, wherein the wavy line is an attachment site to Rb, or to the enzyme- cleavable group.

[0112] In some embodiments, R24 and R25 as described above are independently selected from H and a chelator, wherein the chelator is optionally attached to the nitrogen of -NR24R25 by an alkylene, arylene, carbocyclo, heteroarylene or heterocarbocylo; provided that both R24 and R25are not H. For example, in some embodiments the chelator is selected from ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), benzyl-DTPA, l,4,7,10-tetraazacyclododeca’e-”N'”",N'"-tetraacetic acid (DOTA), benzyl-DOTA, l,4,7-triazacyclonona’e-”N',N"-triacetic acid (NOTA), benzyl-NOTA, 1,4,8,11- tetraazacyclotetradecane-l,4,8,ll-tetraacetic acid (TETA) a’d Ν,Ν'-dialkyl substituted piperazine.

[0113] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 35 WO 2024 / 149345 PCT / CN2024 / 071901 wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0114] In some embodiments, each monosaccharide as described above is independently selected from: a C5 or C6 sugar selected from glucose, ribose, galactose, mannose, arabinose, 2- deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose talose, aldose, ketose, glucosamine, N-acetyl glucosamine, galactosamine, and N-acetyl galactosamine;a sugar acid selected from gluconic acid, aldonic acid, uronic acid and ulosonic acid; or an amino sugar is selected from glucosamine, N-acetyl glucosamine, galactosamine, and N-acetyl galactosamine.

[0115] In some embodiments, each monosaccharide as described above is independently selected from: a C5 or C6 sugar selected from glucose, ribose, galactose, mannose, arabinose, 2- deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose talose, aldose, and ketose, a sugar acid selected from gluconic acid, aldonic acid, uronic acid and ulosonic acid; or an amino sugar selected from glucosamine, N-acetyl glucosamine, galactosamine, and N-acetyl galactosamine.

[0116] In some embodiments, the attachment site as described above is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, and protected forms thereof.

[0117] In some embodiments, provided are Linker compounds comprising a Polar group having a formula selected from the following: (a) ~R20-R21-[O-CH2-CH2]n20-R22-R30 (XXX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently, a bond or Ci-C3 alkylene groups; R30 is selected from an optionally substituted C3-C10 carbocycle; thiourea; optionally substituted thiourea; urea; optionally substituted urea; sulfamide; alkyl sulfamide; acyl sulfamide, optionally substituted alkyl sulfamide; optionally substituted acyl sulfamide; sulfonamide; optionally substituted sulfonamide; guanidine, including alkyl and aryl guanidine; phosphoramide; or optionally substituted 36 WO 2024 / 149345 PCT / CN2024 / 071901 phosphoramide; or R30 is selected from azido, alkynyl, substituted alkynyl, -NH-C(O)-alkynyl, -NH- C(O)-alkynyl-R65; cyclooctyne; -NH-cyclooctyne, -NH-C(O)-cyclooctyne, or -NH-(cyclooctyne)2; wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (b) ~R20-R21-[O-CH2-CH2]n20-R22-NH-C(O)-R31 (XXXI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (c) ~R20-R21-[O-CH2-CH2]n20-R22-C(O)NH-R31 (XXXII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each , independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch, independently, having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle and optionally substituted heteroaryl; and n20 is 2 to 26; (d) ~R20-R21-[O-CH2-CH2]n20-R22-C(O)NR31-R22-NR24R25 (XXXIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R31 is H or R22-NR24R25; R21 and R22 are each, independently, a bond or C1-C3 alkylene groups; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group, provided that R24 and R25 are not both H; and n20 is 2 to 26; (e) ~R20-R2HO-CH2-CH2]n20-R22-N(R33-R31)2 (XXXIV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R33 is C1-C3 alkylene, C1-C3 alkylene-C(O), -C(O)-Ci-C3 alkylene, or -C(O)-Ci-C3 alkylene-C(O); R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (f) ~R20-(R21-[CH2-CH(OR34)-CH2-O]n20-R36)n25 (XXXV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; each R21 is independently a bond, -O- or C1-C3 alkylene group; each R34 is 37 WO 2024 / 149345 PCT / CN2024 / 071901 independently H, -[CH2-CH(OH)-CH2-O]n2o-R36, -C(O)-NR24R25or -C(O)N(RN)-Ci-C6alkylene- NR24R25; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; or substituted polyhydroxyl group, provided that both R24 and R25 are not H; each R36 is independently H, Ci-C6alkylene-C(OH)H-NR44R45, Ci-C6alkylene-C(OH)H-Ci-C6alkylene-NR44R45, - C(O)-NR24R25, -C(O)N(RN)-Ci-C6alkylene-NR24R25, Ci-C6alkylene-C(O)NR24R25 or Ci- C6alkylene-CO2R37; each R37 is independently H or Ci-Ce alkyl; R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; and substituted -C(O)-polyhydroxyl group, provided that both R44and R45are not H; each n20 is independently 1 to 26; and n25 is 2 or 2; (g) ~R20-R21-[[CH2-CH2-O]n20-R22-[CH2-[CH(OH)]n23-CH2-OM^ (XXXVI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21, R22 and R23 are each independently a bond or C1-C3 alkylene group; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; and substituted -C(O)-polyhydroxyl group, provided that R24 and R25 are not both H; each n20 is independently 0 to 26, and each n21 is independently 0 to 26, with the proviso that at least one of n20 or n21 is 2 to 26; n22 is 1 to 5; each n23 is independently 1 or 2; (h) ~R20-(R21-[O-CH2-CH2]n20-R22-N(RN)-CO2-[CH2-CH(OR34)-CH2-O]n2i-R36)n25 (XXXVII) (i) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently a bond or Ci-C3 alkylene groups; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; and substituted polyhydroxyl group, provided that both R44 and R45 and not H; each R34 is independently H, -[CH2-CH(OH)-CH2-O]n2o-R36 or -C(O)N(RN)-Ci-C6alkylene- NR24R25; each R36 is independently H, Ci-C6alkylene-C(OH)H-NR44R45, Ci- C6alkylene-C(OH)H-Ci-C6alkylene-NR44R45, -C(O)N(RN)-Ci-C6alkylene- NR24R25, Ci-C6alkylene-C(O)NR24R25 or Ci-C6alkylene-CO2R37; each R37 is independently H or Ci-Ce alkyl; R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)- polyhydroxyl group; and substituted -C(O)-polyhydroxyl group, provided that both R44 and R45 are not H; n20 is 2 to 26; n21 is 1 to 26; and n25 is 1 or -R20-(R21-[N(RN)-C(O)-[O-CH2-CH(OH)-CH2]n20]n2i-R22-NR24R25)n25 (XXXVIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently a bond or Ci-C3 alkylene groups; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; and substituted polyhydroxyl group, provided that R24 and R25 are not both H; n20 is 2 to 26; n21 is 1 to 4; and n25 is 1, 2 or 3; (j) ~R20-(R21-[C(Ra)H-C(O)-N(RN)]n20-R22-[CH2-CH2-O]n20-NR24R25)n25 38 WO 2024 / 149345 PCT / CN2024 / 071901 (XXXIX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, C1-C3 alkylene,-Ci- C3alkylene-[O-CH2-CH2-]n20, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[0-CH2-CH2-]n2o- C(O)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-C6 alkyl or -R22- NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)- Ci-Cs alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle, provided that R24 and R25 are not both H; each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; and n25 is 1 or 2; and (k) ~R20-R21-[C(Ra)H-C(O)-N(RN)]n20-R22-[CH2-CH2-O]n20-NR24R25 R21-[C(RQH-C(O)-N(RN)]n2i-R22-[CH2-CH2-O]n2i-R23-CO2^ (XXXVX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21, R22 and R23 are each, independently, a bond, C1-C3 alkylene, -Ci- C3alkylene-[O-CH2-CH2-]n20, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[O-CH2-CH2-]n20- C(O)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-C6 alkyl or -R22- NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)- Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle, provided that R24 and R25 are not both H; R26 is H or Ci-C6 alkyl; each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; and each n21 is independently 0 to 26, with the proviso that at least one n21 is 2 to 26.

[0118] In some embodiments, provided are Linker compounds comprising a Polar group having a formula selected from the following: (a) ~R20-R21-[O-CH2-CH2]n20-R22-R30 (XXX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently, a bond or C1-C3 alkylene groups; R30 is selected from an optionally substituted C3-C10 carbocycle; thiourea; optionally substituted thiourea; urea; optionally substituted urea; sulfamide; alkyl sulfamide; acyl sulfamide, optionally substituted alkyl sulfamide; optionally substituted acyl sulfamide; sulfonamide; optionally substituted sulfonamide; guanidine, including alkyl and aryl guanidine; phosphoramide; or optionally substituted phosphoramide; or R30 is selected from azido, alkynyl, substituted alkynyl, -NH-C(O)-alkynyl, -NH- C(O)-alkynyl-R65; cyclooctyne; -NH-cyclooctyne, -NH-C(O)-cyclooctyne, or -NH-(cyclooctyne)2; wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally 39 WO 2024 / 149345 PCT / CN2024 / 071901 substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (b) ~R20-R21-[O-CH2-CH2]n20-R22-NH-C(O)-R31 (XXXI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (c) ~R20-R21-[O-CH2-CH2]n20-R22-C(O)NH-R31 (XXXII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each , independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch, independently, having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle and optionally substituted heteroaryl; and n20 is 2 to 26; (d) ~R20-R21-[O-CH2-CH2]n20-R22-C(O)NR31-R22-NR24R25 (XXXIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R31 is H or R22-NR24R25; R21 and R22 are each, independently, a bond or Ci-C3 alkylene groups; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group, provided that R24 and R25 are not both H; and n20 is 2 to 26; (e) ~R20-R21-[O-CH2-CH2]n20-R22-N(R33-R31)2 (XXXIV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or Ci-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R33 is Ci-C3 alkylene, Ci-C3 alkylene-C(O), -C(O)-Ci-C3 alkylene, or -C(O)-Ci-C3 alkylene-C(O); R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (f) ~R20-(R21-[CH2-CH(OR34)-CH2-O]n20-R36)n25 (XXXV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; each R21 is independently a bond, -O- or Ci-C3 alkylene group; each R34 is independently H, -[CH2-CH(OH)-CH2-O]n2o-R36, -C(O)-NR24R25or -C(O)N(RN)-Ci-C6alkylene- NR24R25; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; or substituted polyhydroxyl group, provided that both R24 and R25 are not H; each R36 is 40 WO 2024 / 149345 PCT / CN2024 / 071901 independently H, Ci-C6alkylene-C(OH)H-NR44R45, Ci-C6alkylene-C(OH)H-Ci-C6alkylene-NR44R45, - C(O)-NR24R25, -C(O)N(RN)-Ci-C6alkylene-NR24R25, Ci-C6alkylene-C(O)NR24R25 or Ci- C6alkylene-CO2R37; each R37 is independently H or Ci-C6 alkyl; R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; and substituted -C(O)-polyhydroxyl group, provided that both R44and R45are not H; each n20 is independently 1 to 26; and n25 is 2 or 2; (g) ~R20-R21-[[CH2-CH2-O]n20-R22-[CH2-[CH(OH)]n23-CH2^ (XXXVI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21, R22 and R23 are each independently a bond or Ci-C3 alkylene group; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; and substituted -C(O)-polyhydroxyl group, provided that R24 and R25 are not both H; each n20 is independently 0 to 26, and each n21 is independently 0 to 26, with the proviso that at least one of n20 or n21 is 2 to 26; n22 is 1 to 5; each n23 is independently 1 or 2; (h) ~R20-(R21-[O-CH2-CH2]n20-R22-N(RN)-CO2-[CH2-CH(OR34^ (XXXVII) (i) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently a bond or C1-C3 alkylene groups; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; and substituted polyhydroxyl group, provided that both R44 and R45 and not H; each R34 is independently H, -[CH2-CH(OH)-CH2-O]n2o-R36 or -C(O)N(RN)-Ci-C6alkylene- NR24R25; each R36 is independently H, Ci-C6alkylene-C(OH)H-NR44R45, Ci- C6alkylene-C(OH)H-Ci-C6alkylene-NR44R45, -C(O)N(RN)-Ci-C6alkylene- NR24R25, Ci-C6alkylene-C(O)NR24R25 or Ci-C6alkylene-CO2R37; each R37 is independently H or Ci-C6 alkyl; R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)- polyhydroxyl group; and substituted -C(O)-polyhydroxyl group, provided that both R44 and R45 are not H; n20 is 2 to 26; n21 is 1 to 26; and n25 is 1 or ~R20-(R21-[N(RN)-C(O)-[O-CH2-CH(OH)-CH2]n20]n2i-R22-NR24R25)n25 (XXXVIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently a bond or Ci-C3 alkylene groups; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; and substituted polyhydroxyl group, provided that R24 and R25 are not both H; n20 is 2 to 26; n21 is 1 to 4; and n25 is 1, 2 or 3; (j) ~R20-(R21-[C(Ra)H-C(O)-N(RN)]n20-R22-[CH2-CH2-O]n20-NR24R25)n25 (XXXIX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, Ci-C3 alkylene,-Ci- 41 WO 2024 / 149345 PCT / CN2024 / 071901 C3alkylene-[O-CH2-CH2-]n20, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[O-CH2-CH2-]n20- C(O)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-Ce alkyl or -R22- NR24r25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted - C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII), provided that R24 and R25 are not both H; each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; and n25 is 1 or 2; and (k) ~R20-R21-[C(Ra)H-C(O)-N(RN)]n20-R22-[CH2-CH2-O]n20-NR24R25 R21-[C(Ra)H-C(O)-N(RN)]n2i-R22-[CH2-CH2-O]n2i-R23-CO2-R26 (XXXVX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21, R22 and R23 are each, independently, a bond, Ci-C3 alkylene, -Ci- C3alkylene-[0-CH2-CH2-]n2o, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[0-CH2-CH2-]n2o- C(O)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-Ce alkyl or -R22- Nr24R25· r24 anc | r25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted - C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII), provided that R24 and R25 are not both H; R26 is H or Ci-Ce alkyl; each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; and each n21 is independently 0 to 26, with the proviso that at least one n21 is 2 to 26.

[0119] In some embodiments, provided are Linker compounds comprising a Polar group having a formula selected from the following, or a stereoisomer or salt thereof: ~R20-R21-[O-CH2-CH2]n20-R22-NH-C(O)-R31 (XXXI); ~R20-R21-[O-CH2-CH2]n20-R22-C(O)NH-R31 (XXXII); and ~R2°-R21-[O-CH2-CH2]n20-R22-N-(R33-R31)2 (XXXIII), wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or Ci-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R33 is Ci-C3 alkylene, -Ci-C3 alkylene-C(O), -C(O)-Ci-C3 alkylene or -C(O)-Ci-C3 alkylene- C(O); R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; the wavy (~j line indicates an attachment site to R20; and n20 is 2 to 26.

[0120] In some embodiments, provided are Linker compounds comprising a Polar group formed from a precursor group selected from the following: 42 WO 2024 / 149345 PCT / CN2024 / 071901 wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0121] In some embodiments, the attachment site to Rb, or to the enzyme-cleavable group, as 43 WO 2024 / 149345 PCT / CN2024 / 071901 described above, is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, and protected forms thereof.

[0122] In some embodiments, provided are Linker compounds comprising a Polar group having a formula: ~R20-(R43.R4i.^.CH2.CH2]n40.R42.R43.(NR44^^ (XL) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, bond or Ci-Ce alkylene; each R43 is, independently, selected from a bond, Ci-Ci2 alkylene, -OCi-Ci2 alkylene, -C(=O)-, -NRa-Ci-Ci2 alkylene, -Ci-Ci2 alkylene-NRa-, -C(O)-Ci-Ci2 alkylene, -C1-C12 alkylene-C(O)-, -NRa-Ci-Ci2 alkylene-C(O)-, -C(O)-Ci-Ci2 alkylene-NRa-, -NRa-C(O)-NRa-, -NRa-C(O)-, -NRa-C(O)-Ci-Ci2 alkylene, -C(O)-NRa-Ci-Ci2 alkylene, -heteroarylene, heteroaryl-Ci-Ci2 alkylene, heteroaryl-Ci-Ci2 alkylene-C(O)-, or -C(O)NR46R47, wherein each alkylene is optionally substituted with hydroxyl, SO3H and / or oxo, Ra is H, Ci-Ce alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group, and one of R46 and R47 is H or Ci-Ci2 alkylene and the other is C1-C12 alkylene, wherein one of the Ci-C2 alkylenes is bound to NR44R45 at the nitrogen atom; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)- polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; n40 is 2 to 26; n41 is 1 to 6; and n42 is 1 to 6.

[0123] In some embodiments, provided are Linker compounds comprising a Polar group having a formula: ~R20-(R4i-[O-CH2-CH2]n40-R42-R43-(NR44R45)n4i)n42 (XLI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, bond or Ci-C6 alkylene; R43 is selected from a bond, C1-C12 alkylene, -OC1-C12 alkylene, -C(=O)-, -NRa-Ci-Ci2 alkylene, -C1-C12 alkylene-NRa-, -C(O)-Ci-Ci2 alkylene, -C1-C12 alkylene-C(O)-, -NRa-Ci-Ci2 alkylene-C(O)-, -C(O)-Ci- C12 alkylene-NRa-, -NRa-C(O)-NRa-, -NRa-C(O)-, -NRa-C(O)-Ci-Ci2 alkylene, C(O)-NRa-Ci-Ci2 alkylene, -heteroarylene, heteroaryl-Ci-Ci2 alkylene, heteroaryl-Ci-Ci2 alkylene-C(O)-, and - C(O)NR46R47, wherein each alkylene is optionally substituted with hydroxyl, SO3H and / or oxo, Ra is H, Ci-Ce alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group and one of R46 and R47 is H or Ci-Ci2 alkylene and the other is Ci-Ci2 alkylene, wherein one of the Ci-C2 alkylenes is bound to NR44R45 at the nitrogen atom; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; n40 is 1 to 26; n41 is 1 to 6; and n42 is 1 to 6.

[0124] In some embodiments, provided are Linker compounds comprising a Polar group having a formula: ~R20-(R41-[O-CH2-CH2]n40-R42-R43-(NR44R^ (XLI I) 44 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, a bond or C1-C3 alkylene; R43 is selected from a bond, Ci-C6 alkylene, -OC1-C12 alkylene, -C(=O)-, -NRa -C1-C12 alkylene, -Ci-Ce alkylene-NRa-, -C(O)-Ci-C6 alkylene, -Ci-Ce alkylene-C(O)-, -NRa-Ci-C6 alkylene-C(O)-, -C(O)-Ci-C6 alkylene-NRa-, -NRa-C(O)-NRa-, -NRa-C(O)-, -NRa-C(O)-Ci- Ce alkylene, -C(O)-NRa-Ci-Ci2 alkylene, -heteroarylene, heteroaryl-Ci-Ce alkylene, heteroaryl-Ci-C6 alkylene-C(O)-, and -C(O)NR46R47, wherein each alkylene is optionally substituted with hydroxyl, SO3H, and / or oxo, Ra is H, Ci-Ce alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group and one of R46 and R47 is H or Ci-Ce alkylene and the other is C1-C12 alkylene, wherein one of the C1-C2 alkylenes is bound to NR44R45 at the nitrogen atom; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; n40 is 1 to 16; n41 is 1 to 4; and n42 is 1 to 4.

[0125] In some embodiments, R20as described above is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, or protected forms thereof.

[0126] In some embodiments, R20 as described above comprises one of the following structures: 45 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer thereof, wherein R is H, Ci-Ce alkyl or polyhydroxyl group, n is 0 to 12, the (-^ *) indicates an attachment site to Rb, or to the enzyme-cleavable group, and the (-^) indicates an attachment site to a remainder portion of the Polar group. 46 WO 2024 / 149345 PCT / CN2024 / 071901

[0127] In some embodiments, R20 as described above has one of the following structures: 47 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer thereof, wherein n = 0 to 12, the (-^ *) indicates an attachment site to Rb, or to the enzyme-cleavable group, and the (-^) indicates an attachment site to a remainder portion of the Polar group.

[0128] In some embodiments, R43-(NR44R45)n4i as described above has one of the following structures:

[0129] or a stereoisomer thereof, wherein Ra is Η, Οι-Οβ alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group; p is an integer from 1 to 6, and the (-^) indicates the attachment site of R43 to the remainder of the Polar group. 48 WO 2024 / 149345 PCT / CN2024 / 071901

[0130] In some embodiments, R43-(NR44R45)n4i as described above has one of the following structures: or a stereoisomer thereof, wherein the (-^) indicates the attachment site of R43 to the remainder of the Polar group.

[0131] In some embodiments, -NR44R45 as described above has one of the following structures: 49 WO 2024 / 149345 PCT / CN2024 / 071901 indicates the attachment site of -NR44R45 to theor a stereoisomer thereof, wherein the (-^ remainder of the Polar group.

[0132] In some embodiments, provided are Linker compounds comprising a Polar group having one of the following structures prior to attachment to the Linker Unit: 50 WO 2024 / 149345 PCT / CN2024 / 071901 51 WO 2024 / 149345 PCT / CN2024 / 071901 52 WO 2024 / 149345 PCT / CN2024 / 071901 OH 53 WO 2024 / 149345 PCT / CN2024 / 071901 OH 54 WO 2024 / 149345 PCT / CN2024 / 071901 55 WO 2024 / 149345 PCT / CN2024 / 071901 OH HO,, J ho V^oh OH OH p^OH HO γ^ γ > 0H 0Hi 2 1 । 2 1 x xx ,N. A A _N. A xx _N N X N X N Y 0 1 O 1 0 [ 0 HN* OH HO,, J HOykH OH OH ^ΟΗ xx A / k .A HO Y^ 0H 0H| j S । § XN Jy 0 1 0 1 0 [ 0 HN. * OH HO,, J ho Y^oh OH OH γ*ΟΗ xN A J\A HO Y^ γ > ^°\°H °H| 8 1 1 8 0^ \ / χ,Ν. A A _N. A χχ / ^Y N Y N < 11 1 11 1Vo^ o 1 o 1 NH, * H OH OH OH 1 H OH OH OH A / N H2n ' J HO HO" / YOH HO-K Υ·0Η 0 \ A^o^o^o^n^oh oh o ho ); HO Aoh HO HO" / YOH HO— / YOH । 8N. A / x ^0^ / X. / X OH Η Η / \ PH 0 HO )—< HO Aoh HO HO" / / -OH HO— / Aoh Ja ~o-v '"°—γΎοη oh J H Ϊ ho YY HO Aoh OH OH OHΑ^ο^γί^ο^Χ / ΟΗ OH OH OH -Ox ^ / A^°x ^A'xYx A^AOH 56 WO 2024 / 149345 PCT / CN2024 / 071901 57 WO 2024 / 149345 PCT / CN2024 / 071901 58 WO 2024 / 149345 PCT / CN2024 / 071901 59 WO 2024 / 149345 PCT / CN2024 / 071901 60 WO 2024 / 149345 PCT / CN2024 / 071901 61 WO 2024 / 149345 PCT / CN2024 / 071901 62 WO 2024 / 149345 PCT / CN2024 / 071901 63 WO 2024 / 149345 PCT / CN2024 / 071901 OH * OH 64 WO 2024 / 149345 PCT / CN2024 / 071901 HO HO 65 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH 66 WO 2024 / 149345 PCT / CN2024 / 071901 OH O 67 WO 2024 / 149345 PCT / CN2024 / 071901 68 WO 2024 / 149345 PCT / CN2024 / 071901 69 WO 2024 / 149345 PCT / CN2024 / 071901 70 WO 2024 / 149345 PCT / CN2024 / 071901 71 WO 2024 / 149345 PCT / CN2024 / 071901 72 WO 2024 / 149345 PCT / CN2024 / 071901 Ο Ο 73 WO 2024 / 149345 PCT / CN2024 / 071901 wherein: (*) indicates the attachment site to site Rb, or to the enzyme-cleavable group; each R is independently H or Ci-Ce alkyl; R’ is H, Ci-Ce alkyl, -N(R24)(R25) or -CO2H; each n is independently 1 to 12; X is O, NR or -CH2-; V is bond or Ci-Ce alkyl; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -C(O)-Ci-Cs alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; substituted -C(O)-Ci-Cs alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits, provided that R24 and R25 are not both H. In some embodiments of the previous embodiment, wherein: each R is independently H or Ci-Ce alkyl; R’ is H, Ci-Ce alkyl, -N(R24)(R25) or -CO2H; each n is independently 1 to 12; X is O, NR or -CH2-; V is bond or Ci-Ce alkyl; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; 74 WO 2024 / 149345 PCT / CN2024 / 071901 substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; or -NR24R25 together from a C8-C8 heterocycle, provided that R24 and R25 are not both H.

[0133] In some embodiments, provided are Linker compounds comprising a Polar group having a formula selected ~R40-(R43-R41-[O-CH2-CH2]n40-R4HO-CH2-CH2]n40-R42-R43-(NR44R45)^ (XLIII) or a stereoisomer or salt thereof, wherein: R40 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, a bond or Ci-C6 alkylene; each R43 is, independently, selected from a bond, Ci-Ci2 alkylene, -OC1-C12 alkylene, -C(=O)-, -NH-C1-C12 alkylene, -C1-C12 alkylene-ΝΗ-, -C(O)-Ci-Ci2 alkylene, -Ci-Ci2 alkylene-C(O)-, -NH-C1-C12 alkylene- C(O)-, -C(O)-Ci-Ci2 alkylene-ΝΗ-, -NH-C(O)-NH-, -NH-C(O)-, -NH-C(O)-Ci-Ci2 alkylene, -C(O)-NH- Ci-Ci2 alkylene, Ci-Ci2alkylene-NH-C(O)-, -heteroarylene, heteroaryl-Ci-Ci2 alkylene, heteroaryl-Ci- Ci2 alkylene-C(O)-, or -C(O)NR46R47, wherein one of R46 and R47 is H or C1-C12 alkylene and the other is C1-C12 alkylene; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; each R46 is independently selected from -NR50-, -NR50-Ci- C6alkylene-NR50-, -NR50-C(O)-NR50-S(O)2-NR50- or -NR50-C(O)-Ci-6alkylene-; each R50 is independently selected from H, Ci-C6 alkyl, or polyhydroxyl group; each n40 is independently 2 to 26; n41 is 1 to 6; and n42 is 1 to 6; (b) ~R40-(R51-[O-CH2-CH2]n43-R52-Xi-R55-X2-R53-[O-CH2-CH2]n43-R54-[X3-R56]n44-^^^^ (XLIV) or a stereoisomer or salt thereof, wherein:R40 is an attachment group to site Rb, or to the enzyme-cleavable group; R51, R52, R53 and R54 are each, independently, a bond, or Ci-C8 alkylene; Xi, X2 and X3 are each independently -NRN-C(O)- or -C(O)-NRN-;each RN independently represent H, Ci-Cs alkyl, or polyhydroxyl group; R55 and R56 each independently represent a bivalent polyhydroxyl group; R57 is H, OH or Ci-Ce alkyl; each n43 is independently 0 to 26, with the proviso that at least one n43 is 1 to 26; n44 is 0 to 10; and n45 is 1 or 2; and (c) ~R40-R51-[O-CH2-CH2]n43-R52-N-(R53-Xi-R54-[O-CH2-CH2]n43-(NR44R45))2 (XLV) or a stereoisomer or salt thereof, wherein: R40 is an attachment group to site Rb, or to the enzyme-cleavable group; R51, R53 and R54 are each, independently, a bond or optionally-substituted Ci-C6 alkylene; R52 is a bond, Ci-C6 alkylene, -C(O)- or -O-C(O)-; each Xi is independently -NRN- C(O)- or -C(O)-NRN-; each RN independently represent H, Ci-Ce alkyl, or polyhydroxyl group; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)- 75 WO 2024 / 149345 PCT / CN2024 / 071901 polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; and each n43 is independently 2 to 26.

[0134] In some embodiments, provided are Linker compounds comprising a Polar group having one of the following structures prior to attachment to the enzyme-cleavable group and / or to the Linker Unit: I N * NR4R5 * Ra I 76 WO 2024 / 149345 PCT / CN2024 / 071901 O OH OH OH OH O OH OH wherein: (*) indicates the attachment site to Rb, or to the enzyme-cleavable group; each R is independently H, alkyl or polyhydroxyl group; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; and each n is independently 1 to 12.

[0135] In some embodiments, provided are Linker compounds comprising a Polar group having a formula selected from: 77 WO 2024 / 149345 PCT / CN2024 / 071901 OR76 ^^OR76 or a stereoisomer or salt thereof, wherein: each Y is independently R76 or ; each R76 is independently H, acetyl, -P(=O)(OH)-, or -(CH2)v-O-S(=O)2(OH); each Ra and Rb is independently H or Ra and Rb are taken together with the carbon to which they are attached to form an oxo group; each q is independently 2-26; each m is independently 1 to 4; each n is independently 1 to 4; each v is independently 1 to 6; and each * is an attachment site to Rb, or to the enzyme-cleavable group. In OR76 p^OR76 some embodiments, Y is R76. In other embodiments, Y is

[0136] In some embodiments, provided are Linker compounds comprising a Polar group having a formula selected from: (XVIa) 78 WO 2024 / 149345 PCT / CN2024 / 071901 (XVII la) or a stereoisomer or salt thereof, wherein: each R76 is independently H, acetyl, -P(=O)(OH)_, or -(CH2)v S(=O)2(OH); each q is independently 2-26; each m is independently 1 to 4; each n is independently 1 to 4; each v is independently 1 to 6; and each * is an attachment site to Rb, or to the enzyme-cleavable group.

[0137] In some embodiments, provided are Linker compounds comprising a Polar group having a formula selected from: WO 2024 / 149345 PCT / CN2024 / 071901 (XVII lb) or a stereoisomer or salt thereof, wherein: each q is independently 2-26; each m is independently 1 to 4; each n is independently 1 to 4; and each * is an attachment site to Rb, or to the enzyme-cleavable group.

[0138] In some embodiments, each Ra and Rb as described above are independently H. In other embodiments, Ra and Rb as described above are taken together with the carbon to which they are attached to form an oxo group.

[0139] In some embodiments, q as described above is 10-20. For example, in some embodiments q as described above is 12.

[0140] In some embodiments, provided are Linker compounds comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 80 81 WO 2024 / 149345 PCT / CN2024 / 071901 82 WO 2024 / 149345 PCT / CN2024 / 071901 OH HO OH OH OH 83 WO 2024 / 149345 PCT / CN2024 / 071901 84 WO 2024 / 149345 PCT / CN2024 / 071901 85 WO 2024 / 149345 PCT / CN2024 / 071901 86 WO 2024 / 149345 PCT / CN2024 / 071901 87 WO 2024 / 149345 PCT / CN2024 / 071901 88 WO 2024 / 149345 PCT / CN2024 / 071901 89 WO 2024 / 149345 PCT / CN2024 / 071901 HO HO NH 90 WO 2024 / 149345 PCT / CN2024 / 071901 91 WO 2024 / 149345 PCT / CN2024 / 071901 OH 92 WO 2024 / 149345 PCT / CN2024 / 071901 93 WO 2024 / 149345 PCT / CN2024 / 071901 94 WO 2024 / 149345 PCT / CN2024 / 071901 95 WO 2024 / 149345 PCT / CN2024 / 071901 96 WO 2024 / 149345 PCT / CN2024 / 071901 / ( / < \\ / '0 > 0 O O op Y -------f / 11. / $ / : -^ < u / +-° 0 0 0 0 ) >=O / -------4 0 i ί i 0 + o / : / : o< , ί P P P P ___ / \ Ο -ω -Ο / — / > "O : / : / / \ s a ( 'x ■> < °? c <A 0 < ° -° / ° A, ° a < > ( > \ zO / \ -ω " < Ο -ω -ο O O O O (J)' ,-----' ) O \ \ II J / A I ° ' f—' < / 0 z+ 0 q zT p X X \ Μ 0 N M 0 °\ .0 / ° ) X 0 0 1 u r ho"Aoh 0 hoA-oh ,-x ,0. xx / -x ^0^ / x zx xx x-x A / x. J O 0 0 N N H HN^ L ,.0H hoA Χ>0Η Λ. ,ΌΗ OH γ HO— y HO' γ ο A.J . Χ.'0Η A χ^ Χ^ 0 ■ Χ^ 0 Η ■ ΌΗ HO ΗΟ Α,Ν^Ο Ν OH Lqh ΟΗ Η Ν "^Χ^Η 0' η'''° Η ηοΑ ηο"Αοη η<Υ"οη A ^*0Η oh ; Γ ηο"Λοη ο ηοΑ"οη ■^χ0'^^'°χ^^0'^-^0χ-^^0'^-^0χ-^Λ'Ν^Υ^^Λ'Ν ̂ ηοηνχ Α0Η Η°. J 1 ΰΗ 1 0Η QH γ Ηθ+γ ΗΟ" \"0Η ,0. Λ. Ρ, 1 ΧΟΗ 1 0 0 Η Ρ ΟΗ ΗΟ*Χ|·' 1 κ + Υ,Ν^Ο Ν ΟΗ / >Η ΗΝ"χ2Η0-·γ..-0Η Ηθγ ηΟ"·Α°Η ηοΑ"οη ^ΟΗ |Άη οη ; D . 0 0 / χ / 0^ \Χ ΧχΧ-^0^\ / x^ / 'xq / 'X / \χ°χ----^θ'''’''χ^ -Ό / ^θχ^Ο^Οχ^Ο^ν0^ 97 WO 2024 / 149345 PCT / CN2024 / 071901 98 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH 99 WO 2024 / 149345 PCT / CN2024 / 071901 100 WO 2024 / 149345 PCT / CN2024 / 071901 101 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH OH OH 102 WO 2024 / 149345 PCT / CN2024 / 071901 OH 103 WO 2024 / 149345 PCT / CN2024 / 071901 104 WO 2024 / 149345 PCT / CN2024 / 071901 105 WO 2024 / 149345 PCT / CN2024 / 071901 106 WO 2024 / 149345 PCT / CN2024 / 071901 107 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH 108 WO 2024 / 149345 PCT / CN2024 / 071901 wherein each Z is attached at * and is individually selected from: 109 WO 2024 / 149345 PCT / CN2024 / 071901

[0141] In some embodiments, provided are Linker compounds comprising a Polar group comprising at least one Carboxyl unit having the following formula: R70 L70 (XXXX) or a stereoisomer or salt thereof, wherein: (a) L70 is selected from Ci-C8 alkylene, Ci-C8 alkylene-C(O)-, -C(O)-Ci-C8 alkylene-, and -C(O)-Ci-C8 alkylene-C(O)-, and * is an attachment site to Rb, to the enzyme-cleavable group, or to a remainder of the Polar group; R70 is ~NR71(R72-R73), wherein R71 is selected from H, C1-C12 alkyl, substituted C1-C12 alkyl, or polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits), R72 is a bond or is selected from optionally substituted C1-C3 alkylene, optionally substituted ether, optionally substituted thioether, optionally substituted ketone, optionally substituted amide, polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits), optionally substituted carbocycle, optionally substituted aryl or optionally substituted heteroaryl, and R73 is a carboxyl or polycarboxyl, wherein polycarboxyl comprises 1 to 10, or 1 to 6, or 1 to 4 carboxyl groups, wherein the carboxyl groups are interconnected by alkyl, alkylene, substituted alkyl, substituted alkylene, 110 WO 2024 / 149345 PCT / CN2024 / 071901 heteroalkyl, heteroalkylene, amino and / or amide; or (b) L70 is selected from Ci-C8 alkylene, Ci-C8 alkylene-C(O)-, -C(O)-Ci-C8 alkylene-, and -C(O)-Ci-C8 alkylene-C(O)-, and * is an attachment site to Rb, to the enzyme-cleavable group, or to a remainder of the Polar group; R70 is ~NR71(R75.(R73)2), wherein R71 is selected from H, C1-C12 alkyl, substituted C1-C12 alkyl, or polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits), R75 is a branched optionally substituted C1-C3 alkylene, optionally substituted ether, optionally substituted thioether, optionally substituted ketone, optionally substituted amide, polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits), optionally substituted carbocycle, optionally substituted aryl or optionally substituted heteroaryl and each R73 is independently carboxyl or polycarboxyl, wherein the polycarboxyl comprises 1 to 10, or 1 to 6, or 1 to 4 carboxyl groups, wherein the carboxyl groups are interconnected by alkyl, alkylene, substituted alkyl, substituted alkylene, heteroalkyl, heteroalkylene, amino and / or amidelr (c) L70 is selected from Ci-C8 alkylene, Ci-C8 alkylene-C(O)-, -C(O)-Ci-C8 alkylene-, and -C(O)-Ci-C8 alkylene-C(O)-, and * is an attachment site to Rb, to the enzyme-cleavable group, or to a remainder of the Polar group; R70 is ~N(R74-R73)(R72.R73), wherein R72 and R74 are each independently selected from optionally substituted C1-C3 alkylene, optionally substituted ether, optionally substituted thioether, optionally substituted ketone, optionally substituted amide, polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits), optionally substituted carbocycle, optionally substituted aryl or optionally substituted heteroaryl, and each R73 is independently carboxyl or polycarboxyl, wherein the polycarboxyl comprises 1 to 10, or 1 to 6, or 1 to 4 carboxyl groups, wherein the carboxyl groups are interconnected by alkyl, alkylene, substituted alkyl, substituted alkylene, heteroalkyl, heteroalkylene, amino and / or amide.

[0142] In some embodiments, provided are Linker compounds comprising a Polar group including the Polymer unit and a Sugar unit. In other embodiments, provided are Linker compounds comprising a Polar group including at least two Polymer units. In other embodiments, provided are Linker compounds comprising a Polar group including the Polymer unit and a Carboxyl unit. In other embodiments, provided are Linker compounds comprising at least two Polar groups. In other embodiments, provided are Linker compounds comprising a Polar group including the Polymer unit, the Sugar unit and the Carboxyl unit. In still other embodiments, provided are Linker compounds comprising a Polar group including at least two Polymer units, at least one Sugar unit and at least one Carboxyl unit.

[0143] In some embodiments, provided are Linker compounds comprising at least one of the Polar group attached to the enzyme-cleavable group. For example, in some embodiments provided are Linker compounds comprising at least one Polar group and an the enzyme-cleavable group comprising at least two amino acids. Linker Unit

[0144] In some embodiments, the Linker unit has one of the following structures (i) or (ii): 111 WO 2024 / 149345 PCT / CN2024 / 071901 wherein: a— is an attachment site to an enzyme-cleavable group; β— is an attachment site to the at least one Polar group; δ— is H, an attachment site to at least one of the Drug units, or an attachment site to a linking group attached to the at least one of the Drug units; each Ra independently is H or Ci-C6 alkyl; each Rb independently is halo, Ci-6 alkyl, an attachment site to at least one of the Drug units, or an attachment site to at least one of the Polar group; x is 0, 1, 2, 3 or 4; y is 0, 1, 2 or 3; Rc is a bond, -C(O)-, -S(O)-, -SO2-, Ci-6 alkylene, Ci-6 alkynylene, triazolyl, or combinations thereof; and Y is a bond, -O-, -S-, -N(Ra)-, -C(O)-, -S(O)-, -SO2-Ci-C6 alkylene, Ci-C6 alkenylene, Ci-C6 alkynylene, a group containing triazolyl, or combinations thereof.

[0145] In some embodiments, the Linker unit has from 1 to 4 attachment sites for a Drug unit. In some embodiments, the Linker unit has from 1 to 3 or 1 to 2 attachment sites for a Drug unit (D).

[0146] In some embodiments, a Linker unit includes at least one Polar group, such as a Polymer unit. In some embodiments, the Polar group includes at least one Polymer unit and optionally a Sugar unit and / or Carboxyl unit or combinations thereof. In some embodiments, the Polymer unit comprises a polyamide, a polyether, or a combination thereof, wherein the polyether comprises a hydroxyl group, a polyhydroxyl group, a sugar group, a carboxyl group, or combinations thereof.

[0147] In some embodiments, the Linker unit is a cleavable linker subunit. As used herein, the term “cleavable " refers to a metabolic process or reaction inside a cell or in the extracellular milieu, whereby the covalent attachment between a Drug unit (e.g., a cytotoxic agent) and the Linker unit or portion thereof is broken, resulting in the free Drug unit, or a metabolite of the Linker unit-Drug, which is dissociated from the remainder of the Linker unit.

[0148] In some embodiments, the Linker unit includes a protease cleavable linker subunit. In some embodiments, the Linker unit is a protease cleavable linker that is cleavable under intracellular conditions, such that cleavage of or within the Linker unit releases the Drug unit from Linker unit or the remainder of Linker unit in the intracellular environment. For example, in some embodiments, the Linker unit is cleavable by a cleaving agent that is present in the intracellular environment (e.g., within a lysosome or endosome or caveolae). As used herein, the terms “cleavable under intracellular conditions,” "intracellularly cleaved," and "intracellular cleavage" refer to a metabolic 112 WO 2024 / 149345 PCT / CN2024 / 071901 process or reaction inside a cell, whereby the covalent attachment between a Drug unit (e.g., a cytotoxic agent) and the Linker unit or portion thereof is broken, resulting in the free Drug unit, or ar metabolite of the Linker unit-Drug unit dissociated from the remainder of the Linker unit inside the cell. One advantage of using intracellular proteolytic release of the Drug unit is that the activity of the Drug unit is typically attenuated when conjugated and the serum stabilities of the conjugates are typically high.

[0149] In some embodiments, a linkage between the Linker unit and the Drug unit can be cleaved by enzymatically cleavage within the Linker unit by one or more enzymes, including a tumor- associated protease, to liberate the Drug unit. The Linker unit can be, for example, a peptidyl linker that is cleaved by an intracellular peptidase or protease enzyme, including, but not limited to, a lysosomal or endosomal protease. Intracellular protease or cleaving agents can include cathepsins B, C and D and plasmin, all of which are known to hydrolyze dipeptide drug derivatives resulting in the release of active drug inside target cells (see, e.g., Dubowchik and Walker, 1999, Pharm. Therapeutics 83:67-123). Peptidyl linkers can be cleavable by enzymes that are present in target antigen-expressing cells. For example, a Linker unit that is cleavable by the thiol-dependent protease cathepsin-B, which is highly expressed in cancerous tissue, can be used (e.g., having a Phe-Leu, Val-Ala, Val-Cit or Gly-Phe-Leu-Gly peptide).

[0150] Typically, a Linker unit has at least one amino acid or at least two amino acids that form a recognition site for a protease or other cleaving agent. In certain embodiments, the Linker unit has a dipeptide, tripeptide, tetrapeptide or pentapeptide. In certain embodiments, a Linker unit can comprise only natural amino acids. In some embodiments, For example, a Linker unit can have a Phe-Leu, Val-Ala, or Val-Cit peptide that is attached to a PABA group of structure (i) or (ii). Other such cleavable Linker units are described, for example, in U.S. Pat. No. 6,214,345, WO2004 / 010957, US20150297748, US2008 / 0166363, US20120328564 and US20200347075, each of which is incorporated by reference herein. In some embodiments, a Linker unit that is cleavable by an intracellular protease comprises a Val-Cit peptide or a Phe-Lys peptide or Gly-Gly-Phe-Gly linker (see, e.g., US Published Application No. 2015 / 0297748).

[0151] In some embodiments, a Linker unit contains one or more the following: glycine and / or L- amino acids, such as arginine, glutamine, phenylalanine, tyrosine, tryptophan, lysine, alanine, histidine, serine, proline, glutamic acid, aspartic acid, threonine, cysteine, methionine, leucine, asparagine, isoleucine, and valine, that form a recognition and cleavage site for a protease or other cleaving enzyme.

[0152] In some embodiments, an amino acid of a Linker unit has the formula denoted below in the square brackets: wherein Rigo is hydrogen, methyl, isopropyl, isobutyl, sec-butyl, benzyl, p-hydroxybenzyl, -CH2OH, - CH(OH)CH3, -CH2CH2SCH3, -CH2CONH2, -CH2COOH -CH2CH2CONH2, -CH2CH2COOH, - 113 WO 2024 / 149345 PCT / CN2024 / 071901 (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,

[0153] In some embodiments, a Linker unit includes one or more of the following L-(natural) amino acids: alanine, arginine, aspartic acid, asparagine, histidine, glycine, glutamic acid, glutamine, phenylalanine, lysine, leucine, serine, tyrosine, threonine, isoleucine, tryptophan and valine. In some embodiments, a Linker unit does not contain cysteine. In some embodiments, a peptidyl linker does not contain proline.

[0154] In some embodiments, a Linker unit includes one or more of the following amino acids: alanine, arginine, aspartic acid, asparagine, histidine, glycine, glutamic acid, glutamine, phenylalanine, lysine, leucine, serine, tyrosine, threonine, isoleucine, proline, tryptophan, valine, ornithine, penicillamine, β-alanine, aminoalkanoic acid, aminoalkynoic acid, amino alkanedioic acid, aminobenzoic acid, amino-heterocyclo-alkanoic acid, heterocyclo-carboxylic acid, citrulline, statine, diaminoalkanoic acid, and derivatives thereof.

[0155] In some embodiments, a Linker unit includes protease cleavable linker comprising a thiol­ reactive maleimidocaproyl spacer or Stretcher, an amino acid or peptide and a self-immolative group. In some embodiments, a Linker unit includes protease cleavable linker comprising a thiol­ reactive maleimidocaproyl spacer, a valine-citrulline dipeptide, and a p-amino-benzyloxycarbonyl self immolative group.

[0156] In some embodiments, a Linker unit includes a self-stabilizing moiety comprising a maleimide group as described in WO2013 / 173337.

[0157] In some embodiments, the Linker unit includes a glucuronide-cleavable moiety, see, e.g., US 2014 / 0031535.

[0158] In some embodiments, provided are Linker compounds having one of the following structures: 114 WO 2024 / 149345 PCT / CN2024 / 071901 115 WO 2024 / 149345 PCT / CN2024 / 071901 116 WO 2024 / 149345 PCT / CN2024 / 071901 117 WO 2024 / 149345 PCT / CN2024 / 071901 118 WO 2024 / 149345 PCT / CN2024 / 071901 wherein: Rc is a bond or Ci-6 alkylene; the wavy line on the amino group indicates an attachment site for a Stretcher group; or, prior to attachment to the Stretcher group, indicates Η; β— is the attachment site to the at least one Polar group; and the benzylic H on the benzylic OH is optionally replaced with a bond to at least one of the Drug units or to the linking group attached to at least one of the Drug units.

[0159] In some embodiments, at least one of the Drug units is attached directly to the benzylic O at δ. In some embodiments, at least one of the Drug units is attached indirectly, via a linking group. A linking group can be any suitable group for connection of the at least one Drug unit to the benzylic - O- that allows for release of an active Drug unit, or release of an active derivative of the linking group-Drug unit. In some embodiments, a linking group is -NH-CH2-CH2-CH2-C(O)-, the Drug unit is exatecan and the released Drug unit is DXd. (See., e.g., Published US Application No. 2019 / 000898). In other embodiments, the linking group is -C(O)-NH-CH2-CH2-CH2-C(O)-.

[0160] In some embodiments, provided are Linker compounds wherein the Linker unit is a cleavable linker unit. For example, in some embodiments the enzyme-cleavable group comprises a peptide that is cleavable by an intracellular protease. In some embodiments, the intracellular protease is Cathepsin B. In more specific embodiments, the cleavable peptide comprises a valine-citrulline peptide, a valine-alanine peptide, a valine-lysine peptide, a phenylalanine-lysine peptide, or a glycine-glycine-phenylalanine-glycine peptide.

[0161] In some embodiments, provided are Linker compounds comprising one of the following structures: 119 WO 2024 / 149345 PCT / CN2024 / 071901 120 WO 2024 / 149345 PCT / CN2024 / 071901 121 WO 2024 / 149345 PCT / CN2024 / 071901 122 WO 2024 / 149345 PCT / CN2024 / 071901 123 WO 2024 / 149345 PCT / CN2024 / 071901 124 WO 2024 / 149345 PCT / CN2024 / 071901 125 WO 2024 / 149345 PCT / CN2024 / 071901 126 WO 2024 / 149345 PCT / CN2024 / 071901 127 WO 2024 / 149345 PCT / CN2024 / 071901 128 WO 2024 / 149345 PCT / CN2024 / 071901 Ο HO 129 WO 2024 / 149345 PCT / CN2024 / 071901 wherein: Rc is a bond or Ci-6 alkylene; the wavy line on the amino group indicates an attachment site for the Stretcher group; or, prior to attachment to the Stretcher group, indicates H; β— is an attachment site to the at least one Polar group; and the H on the benzylic OH is optionally replaced with a bond to at least one of the Drug units or to the attachment site to at least one of the Drug units.

[0162] In some embodiments, provided are Linker compounds having one of the following structures: 130 WO 2024 / 149345 PCT / CN2024 / 071901 131 WO 2024 / 149345 PCT / CN2024 / 071901 132 WO 2024 / 149345 PCT / CN2024 / 071901 133 WO 2024 / 149345 PCT / CN2024 / 071901 134 WO 2024 / 149345 PCT / CN2024 / 071901 OH 135 WO 2024 / 149345 PCT / CN2024 / 071901 136 WO 2024 / 149345 PCT / CN2024 / 071901 137 WO 2024 / 149345 PCT / CN2024 / 071901 138 WO 2024 / 149345 PCT / CN2024 / 071901 139 WO 2024 / 149345 PCT / CN2024 / 071901 HO 140 WO 2024 / 149345 PCT / CN2024 / 071901 141 WO 2024 / 149345 PCT / CN2024 / 071901 142 WO 2024 / 149345 PCT / CN2024 / 071901 143 WO 2024 / 149345 PCT / CN2024 / 071901 144 WO 2024 / 149345 PCT / CN2024 / 071901 145 WO 2024 / 149345 PCT / CN2024 / 071901 146 WO 2024 / 149345 PCT / CN2024 / 071901 147 WO 2024 / 149345 PCT / CN2024 / 071901 148 WO 2024 / 149345 PCT / CN2024 / 071901 149 WO 2024 / 149345 PCT / CN2024 / 071901 OH 150 WO 2024 / 149345 PCT / CN2024 / 071901 151 WO 2024 / 149345 PCT / CN2024 / 071901 152 WO 2024 / 149345 PCT / CN2024 / 071901 wherein the wavy line on the amino group indicates an attachment site to the Stretcher group; or, prior to attachment to the Stretcher group, indicates H, and the H on the benzylic OH is optionally replaced with a bond to at least one of the Drug units or a linking group attached to the at least one of the Drug units.

[0163] In some embodiments, provided are Linker compounds as described above wherein the Linker unit is attached to a side chain of a subunit of the enzyme-cleavable group.

[0164] In some embodiments, provided are Linker compounds a described above wherein the enzyme-cleavable group is joined to the Stretcher group by a non-peptidic linking group. For example, in some embodiments the non-peptidic linking group is selected from optionally-substituted Ci-Cio alkylene, optionally-substituted C2-C10 alkenylene, optionally-substituted C2-C10 alkynylene, or optionally-substituted polyethylene glycol.

[0165] In some embodiments, provided are Linker compounds as described above comprising the Stretcher group attached to the enzyme-cleavable group. Stretcher Groups

[0166] In some embodiments, provided are Linker compounds comprising a Stretcher group is selected from the following: 153 WO 2024 / 149345 PCT / CN2024 / 071901 wherein R17 is -C1-C10 alkylene-, -Ci-Cio heteroalkylene-, -C3-C8 carbocyclo-, -O-(Ci-C8 alkylene)-, -(CH2-O-CH2)b-Ci-C8 alkylene- (where b is 1 to 26), -Ci-C8 alkylene-(CH2-O-CH2)b- (where b is 1 to 26), -Ci-C8 alkylene-(CH2-O-CH2)b-Ci-C8 alkylene- (where b is 1 to 26), -arylene-, - Ci-Cio alkylene-arylene-, -arylene-Ci-Cio alkylene-, -Ci-Cio alkylene-(C3-C8 carbocyclo)-, -(C3-C8 carbocyclo)-Ci-Cio alkylene-, -C3-C8 heterocyclo-, -Ci-Cio alkylene-(C3-C8 heterocyclo)-, -(C3-C8 heterocyclo)-Ci-Cio alkylene-, -Ci-Cio alkylene-C(=O)-, -Ci-Cioalkylene-C(0)NH-Ci-C8alkylene-[0- CH2-CH2]n-C(O)- (where n is 1 to 26), Ci-Cio heteroalkylene-C(=O)-, -Ci-C8 alkylene-(CH2-O-CH2)b- C(=O)- (where b is 1 to 26), -(CH2-O-CH2)b-Ci-C8 alkylene-C(=O)- (where b is 1 to 26), -Ci-C8 alkylene-(CH2-O-CH2)b-Ci-C8 alkylene-C(=O)- (where b is 1 to 26), -C3-C8 carbocyclo-C(=O)-, -O- (Ci-C8 alkyl)-C(=O)-, -arylene-C(=O)-, -Ci-Cio alkylene-arylene-C(=O)-, -arylene-Ci-Cio alkylene- C(=O)-, -Ci-Cio alkylene-(C3-C8 carbocyclo)-C(=O)-, -(C3-C8 carbocyclo)-Ci-Ci0 alkylene-C(=O)-, - C3-C8 heterocyclo-C(=O)-, -Ci-Cio alkylene-(C3-C8 heterocyclo)-C(=O)-, -(C3-C8 heterocyclo)-Ci-Cio alkylene-C(=O)-, -Ci-Cio alkylene-ΝΗ-, -Ci-Cio heteroalkylene-ΝΗ-, -Ci-C8 alkylene-(CH2-O-CH2)b- NH- (where b is 1 to 26), -(CH2-O-CH2)b-Ci-C8 alkylene-ΝΗ- (where b is 1 to 26), -Ci-C8 alkylene- (CH2-O-CH2)b-Ci-C8 alkylene-ΝΗ- (where b is 1 to 26), -Ci-C8 alkylene-(C(=O))-NH-(CH2-O-CH2)b- C(=O)- (where b is 1 to 26), -Ci-C8 alkylene-(C(=O))-NH-(CH2-O-CH2)b-Ci-C8 alkylene-C(=O)- (where b is 1 to 26), -Ci-C8 alkylene-NH-(C(=O))-(CH2-O-CH2)b-NH- (where b is 1 to 26), -Ci-C8 alkylene-NH-(C(=O))-(CH2-O-CH2)b-Ci-C8 alkylene-ΝΗ- (where b is 1 to 26), -C3-C8 carbocyclo-NH-, -O-(Ci-C8 alkyl)-NH-, -arylene-ΝΗ-, -Ci-Cio alkylene-arylene-ΝΗ-, -arylene-Ci-Cio alkylene-ΝΗ-, -Ci- Cio alkylene-(C3-C8 carbocyclo)-NH-, -(C3-C8 carbocyclo)-Ci-Ci0 alkylene-ΝΗ-, -C3-C8 heterocyclo- NH-, -Ci-Cio alkylene-(C8-C8 heterocyclo)-NH-, -(C3-C8 heterocyclo)-Ci-Cio alkylene-ΝΗ-, -Ci-Cio alkylene-S-, Ci-Cio heteroalkylene-S-, -C3-C8 carbocyclo-S-, -O-(Ci-C8 alkyl)-S-, -arylene-S-, -Ci-Cio alkylene-arylene-S-, -arylene-Ci-Cw alkylene-S-, -Ci-Cio alkylene-(C3-C8 carbocyclo)-S-, -(C3-C8 carbocyclo)-Ci-Cio alkylene-S-, -C3-C8 heterocyclo-S-, -Ci-Cio alkylene-(C3-C8 heterocyclo)-S-, or - (C8-C8 heterocyclo)-Ci-Cio alkylene-S-; or wherein the Stretcher group comprises maleimido(Ci- Cioalkylene-C(O)-, maleimido(CH20CH2)P2(Ci-Cioalkyene)C(0)-, maleimido(Ci-Ci0alkyene) (CH2OCH2)p2C(O)-, or a ring open form thereof, wherein p2 is from 1 to 26; and wherein * is an attachment site to the Targeting group, and the wavy line is an attachment site to the enzyme- cleavable group.

[0167] In some embodiments, provided are Linker compounds comprising a Stretcher group is selected from the following: 154 WO 2024 / 149345 PCT / CN2024 / 071901 wherein the wavy line indicates an attachment site of the Stretcher group to the enzyme- cleavable group, and the attachment site to the Targeting group is on the maleimide, primary amine or alkyne functional group. Linker Compounds

[0168] In some embodiments, provided are Linker compounds selected from one of the following structures: 155 WO 2024 / 149345 PCT / CN2024 / 071901 156 WO 2024 / 149345 PCT / CN2024 / 071901 157 WO 2024 / 149345 PCT / CN2024 / 071901 158 WO 2024 / 149345 PCT / CN2024 / 071901 159 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH OH O^NH ,o \ / A η V h ? UU oH^UNY ΉΗ O^NH2 HO HOh. / hoJ^oh XoH UK / \ zx 1 xx x0 0 N X) O^NH zo / / v. 1 X^^X^ JU 0H Y Xh o^nh2 HO HO-· / Ηοχ°Η YoH 0^"-^ / -0 S o Ο,,,ΝΗ cC^^Xx ju 0H 0 H 0 v H NH O^NH2 Γ U°h r U°h ,0 Y ^OH ο Y ο Y o y OH OH L OH HO HOh. / HoX°H ΖοΗ ,0 ^N—.Y OH hY γ.γΗ ho^oh “A OH0-^ HO,, / \~~°\ ho\AJ '--\ / ΌΗ o- \̂ / OH--N ηοΎ^οη HoU^OH OH 160 WO 2024 / 149345 PCT / CN2024 / 071901 161 WO 2024 / 149345 PCT / CN2024 / 071901 HO OH 162 WO 2024 / 149345 PCT / CN2024 / 071901 163 WO 2024 / 149345 PCT / CN2024 / 071901 NH OH OH O OH OH 164 WO 2024 / 149345 PCT / CN2024 / 071901 165 WO 2024 / 149345 PCT / CN2024 / 071901 OH 166 WO 2024 / 149345 PCT / CN2024 / 071901 OH 167 WO 2024 / 149345 PCT / CN2024 / 071901 168 WO 2024 / 149345 PCT / CN2024 / 071901 169 WO 2024 / 149345 PCT / CN2024 / 071901 170 WO 2024 / 149345 PCT / CN2024 / 071901 171 WO 2024 / 149345 PCT / CN2024 / 071901 OH 0^ NH2 172 WO 2024 / 149345 PCT / CN2024 / 071901 173 WO 2024 / 149345 PCT / CN2024 / 071901 174 WO 2024 / 149345 PCT / CN2024 / 071901 175 WO 2024 / 149345 PCT / CN2024 / 071901 wherein the H on the benzylic OH is optionally replaced with a bond to the at least one Drug unit or to the linking group attached to the at least one Drug unit.

[0169] In some embodiments, provided is a Drug-Linker compound, comprising a Linker compound as described herein attached to the at least one Drug unit, or attached to the linking group attached to the at least one Drug unit, at the attachment site. Drug units

[0170] In some embodiments, the Linkers are attached to at least one Drug unit. As used herein, the term “Drug unit” or drug refers to cytotoxic agents (such as chemotherapeutic agents or drugs), immunomodulatory agents, nucleic acids (including siRNAs), growth inhibitory agents, toxins (e.g., protein toxins, enzymatically active toxins of bacterial, fungal, plant, or animal origin, or fragments thereof), radioactive isotopes, PROTACs and other compounds that are active against target cells when delivered to those cells.

[0171] In some embodiments, provided is a Drug-Linker wherein the Drug unit is selected from a cytotoxic agent, an immune modulatory agent, a nucleic acid, a growth inhibitory agent, a PROTAC, a toxin, a radioactive isotope and a chelating ligand. Cytotoxic Agents

[0172] In some embodiments, a Drug unit is a cytotoxic agent. A "cytotoxic agent" refers to an agent that has a cytotoxic effect on a cell. A "cytotoxic effect" refers to the depletion, elimination 176 WO 2024 / 149345 PCT / CN2024 / 071901 and / or the killing of a target cell(s). Cytotoxic agents include, for example, tubulin disrupting agents, topoisomerase inhibitors, DNA minor groove binders, and DNA alkylating agents.

[0173] In some embodiments, the cytotoxic agent is selected from the group consisting of an auristatin, a maytansinoid, a camptothecin, a duocarmycin, and a calicheamicin. In some embodiments, the cytotoxic agent is an auristatin. Oth other embodiments, the cytotoxic agent is MMAE or MMAF. In some embodiments, the cytotoxic agent is a camptothecin. In some embodiments, the cytotoxic agent is exatecan or SN-38 or DxD. In certain embodiments, the cytotoxic agent is RS-exatecan or SS-exatecan. In other embodiments, the cytotoxic agent is a calicheamicin. In some embodiments, the cytotoxic agent is a maytansinoid. In certain embodiments, the maytansinoid is maytansine, maytansinol or ansamatocin-2.

[0174] Tubulin disrupting agents include, for example, auristatins, dolastatins, tubulysins, colchicines, vinca alkaloids, taxanes, cryptophycins, maytansinoids, hemiasterlins, as well as other tubulin disrupting agents. Auristatins are derivatives of the natural product dolastatin 10. Exemplary auristatins include MMAE (N-methylvaline-valine-dolaisoleuine-dolaproine-norephedrine), MMAF (N- methylvaline-valine-dolaisoleuine-dolaproine-phenylalanine) and AFP (see WO2004 / 010957 and WO2007 / 008603). Other auristatin like compounds are disclosed in, for example, Published US Application Nos. US2021 / 0008099, US2017 / 0121282, US2013 / 0309192 and US2013 / 0157960. Dolastatins include, for example, dolastatin 10 and dolastatin 15 (see, e.g., Pettit et al., J. Am. Chern. Soc., 1987, 109, 6883-6885; Pettit et al., Anti-Cancer Drug Des., 1998, 13, 243-277; and Published US Application US2001 / 0018422). Additional dolastatin derivatives contemplated for use herein are disclosed in U.S. Patent 9,345,785, incorporated herein by reference.

[0175] Tubulysins include, but are not limited to, tubulysin D, tubulysin M, tubuphenylalanine and tubutyrosine. WO2017 / 096311 and WO / 2016-040684 describe tubulysin analogs including tubulysin M.

[0176] Colchicines include, but are not limited to, colchicine and CA-4.

[0177] Vinca alkaloids include, but are not limited to, vinblastine (VBL), vinorelbine (VRL), vincristine (VCR) and vindesine (VOS).

[0178] Taxanes include, but are not limited to, paclitaxel and docetaxel.

[0179] Cryptophycins include but are not limited to cryptophycin-1 and cryptophycin-52.

[0180] Maytansinoids include, but are not limited to, maytansine, maytansinol, maytansine analogs in DM1, DM3 and DM4, and ansamatocin-2. Exemplary maytansinoid drug moieties include those having a modified aromatic ring, such as: C-19-dechloro (U.S. Pat. No. 4,256,746) (prepared by lithium aluminum hydride reduction of ansamitocin P2); C-20-hydroxy (or C-20- demethyl) + / -C-19- dechloro (U.S. Pat. Nos. 4,361,650 and 4,307,016) (prepared by demethylation using Streptomyces or Actinomyces or dechlorination using LAH); and C-20- demethoxy, C-20-acyloxy (-OCOR), + / - dechloro (U.S. Pat. No. 4,294,757) (prepared by acylation using acyl chlorides), and those having modifications at other positions.

[0181] Maytansinoid drug moieties also include those having modifications such as: C-9-SH (U.S. Pat. No. 4,424,219) (prepared by the reaction of maytansinol with H2S or P2S5); C-14- alkoxymethyl(demethoxy / CH2OR) (see, U.S. Pat. No. 4,331,598); C-14- hydroxymethyl or 177 WO 2024 / 149345 PCT / CN2024 / 071901 acyloxymethyl (CH2OH or CH2OAc) (see, U.S. Pat. No. 4,450,254) (prepared from Nocardia); C-15- hydroxy / acyloxy (see, U.S. Pat. No. 4,364,866) (prepared by the conversion of maytansinol by Streptomyces); C-15-methoxy (see, U.S. Pat. Nos. 4,313,946 and 4,315,929) (isolated from Trewia nudiflora); C-18-N-demethyl (see, U.S. Pat. Nos. 4,362,663 and 4,322,348) (prepared by the demethylation of maytansinol by Streptomyces); and 4,5-deoxy (see, U.S. Pat. No. 4,371,533) (prepared by the titanium trichloride / LAH reduction of maytansinol).

[0182] Hemiasterlins include but are not limited to, hemiasterlin and HTI-286.

[0183] Other tubulin disrupting agents include taccalonolide A, taccalonolide B, taccalonolide AF, taccalonolide AJ, taccalonolide Al-epoxide, discodermolide, epothilone A, epothilone B, and laulimalide.

[0184] In some embodiments, a cytotoxic agent can be a topoisomerase inhibitor, such as a camptothecin. Exemplary camptothecins include, for example, camptothecin, irinotecan (also referred to as CPT-11), belotecan, (7-(2-(N-isopropylamino)ethyl)camptothecin), topotecan, 10- hydroxy-CPT, SN-38, exatecan and the exatecan analog DXd (see US20150297748). In some embodiments, the cytotoxic agent is exatecan or SN-38 or DxD. In some embodiments, the cytotoxic agent is RS exatecan or SS exatecan. Other camptothecins are disclosed in WO1996 / 021666, WO00 / 08033, US2016 / 0229862 and WO2020 / 156189.

[0185] In some embodiments, a cytotoxic agent is a duocarmcycin, including the synthetic analogues, KW-2189 and CBI-TML Immune Modulatory Agents

[0186] In some embodiments, a Drug unit is an immune modulatory agent. An immune modulatory agent can be, for example, a TLR7 and / or TLR8 agonist, a STING agonist, a RIG-1 agonist or other immune modulatory agent. In some embodiments, the immune modulatory agent is selected from a TRL7 agonist, a TLR8 agonist, a STING agonist, or a RIG-1 agonist.

[0187] In some embodiments, the immune modulatory agent is an TLR7 agonist. In certain embodiments, the TLR7 agonist is an imidazoquinoline, an imidazoquinoline amine, a thiazoquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2-d]pyrimidine-2,4-diamine, pyrimidine-2,4-diamine, 2-aminoimidazole, l-alkyl-lH-benzimidazol-2-amine, tetrahydropyridopyrimidine, heteroarothiadiazide-2,2-dioxide, a benzonaphthyridine, a guanosine analog, an adenosine analog, a thymidine homopolymer, ssRNA, CpG-A, PolyGlO, or PolyG3. In some embodiments, the immune modulatory agent is a TLR8 agonist. In certain embodiments, the TLR8 agonist is selected from an imidazoquinoline, a thiazoloquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2-d]pyrimidine-2,4-diamine, pyrimidine-2,4-diamine, 2-aminoimidazole, l-alkyl-lH-benzimidazol-2-amine, tetrahydropyridopyrimidine or a ssRNA. In some embodiments, the immune modulatory agent is a STING agonist. In other embodiments, the immune modulatory agent is a RIG-1 agonist. In certain embodiments, the RIG-1 agonist is selected from KIN1148, SB- 9200, KIN700, KIN600, KIN500, KIN100, KIN101, KIN400 and KIN2000.

[0188] In some embodiments, a Drug unit is an immune modulatory agent, such as a TLR7 and / or TLR8 agonist. In some embodiments, a TLR7 agonist is selected from an imidazoquinoline, an imidazoquinoline amine, a thiazoquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2- 178 WO 2024 / 149345 PCT / CN2024 / 071901 d]pyrimidine-2,4-diamine, pyrimidine-2,4-diamine, 2-aminoimidazole, l-alkyl-lH-benzimidazol-2- amine, tetrahydropyridopyrimidine, heteroarothiadiazide-2,2-dioxide, a benzonaphthyridine, a guanosine analog, an adenosine analog, a thymidine homopolymer, ssRNA, CpG-A, PolyGlO, and PolyG3. In some embodiments, the TLR7 agonist is selected from an imidazoquinoline, an imidazoquinoline amine, athiazoquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2- d]pyrimidine-2,4-diamine, pyrimidine-2,4-diamine, 2-aminoimidazole, l-alkyl-lH-benzimidazol-2- amine, tetrahydropyridopyrimidine, heteroarothiadiazide-2,2-dioxide or a benzonaphthyridine. In some embodiments, a TLR7 agonist is a non-naturally occurring compound. Examples of TLR7 modulators include GS-9620, GSK-2245035, imiquimod, resiquimod, DSR-6434, DSP-3025, IMO- 4200, MCT-465, MEDI-9197, 3M-051, SB-9922, 3M-052, Limtop, TMX-30X, TMX-202, RG- 7863, RG-7795, and the compounds disclosed in US20160168164, US 20150299194, US20110098248, US20100143301, and US20090047249.

[0189] In some embodiments, a TLR8 agonist is selected from a benzazepine, an imidazoquinoline, a thiazoloquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2-d]pyrimidine-2,4-diamine, pyrimidine-2,4-diamine, 2-aminoimidazole, l-alkyl-lH-benzimidazol-2-amine, tetrahydropyridopyrimidine or a ssRNA. In some embodiments, a TLR8 agonist is selected from a benzazepine, an imidazoquinoline, a thiazoloquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2-d]pyrimidine-2,4-diamine, pyrimidine-2,4-diamine, 2-aminoimidazole, 1-alkyl-lH- benzimidazol-2-amine, and a tetrahydropyrido pyrimidine. In some embodiments, a TLR8 agonist is a non-naturally occurring compound. Examples of TLR8 agonists include motolimod, resiquimod, 3M-051, 3M-052, MCT-465, IMO-4200, VTX-763, VTX-1463.

[0190] In some embodiments, a TLR8 agonist can be any of the compounds described WO2018 / 170179, WO2020 / 056198 and WO2020056194.

[0191] Other TLR7 and TLR8 agonists are disclosed in, for example, WO2016142250, WO2017046112, WO2007024612, WO2011022508, WO2011022509, WO2012045090, WO2012097173, WO2012097177, WO2017079283, US20160008374, US20160194350, US20160289229, US Patent No. 6043238, US20180086755, WO2017216054, WO2017190669, WO2017202704, WO2017202703, WO20170071944, US20140045849, US20140073642, WO2014056953, WO2014076221, WO2014128189, US20140350031, WO2014023813, US20080234251, US20080306050, US20100029585, US20110092485, US20110118235, US20120082658, US20120219615, US20140066432, US20140088085, US20140275167, and US20130251673, WO2018198091, and US20170131421.

[0192] In some embodiments, an immune modulatory agent is a STING agonist. Examples of STING agonists include, for example, those disclosed in WO2020059895, WO2015077354, WO2020227159, WO2020075790, WO2018200812, and WO2020074004.

[0193] In some embodiments, an immune modulatory agent is a RIG-1 agonist. Examples of RIG-1 agonists include KIN1148, SB-9200, KIN700, KIN600, KIN500, KIN100, KIN101, KIN400 and KIN2000. Toxins

[0194] In some embodiments, a Drug unit is an enzymatically active toxin or fragment thereof, 179 WO 2024 / 149345 PCT / CN2024 / 071901 including but not limited to diphtheria A chain, nonbinding active fragments of diphtheria toxin, exotoxin A chain (from Pseudomonas aeruginosa), ricin A chain, abrin A chain, modeccin A chain, alpha-sarcin, Aleurites fordii proteins, dianthin proteins, Phytolaca americana proteins (PAPI, PAPI I, and PAP-S), momordica charantia inhibitor, curcin, crotin, sapaonaria officinalis inhibitor, gelonin, mitogellin, restrictocin, phenomycin, enomycin, and the tricothecenes. Radioisotopes

[0195] In some embodiments, a Drug unit is a radioactive atom. A variety of radioactive isotopes are available for the production of radioconjugates. Examples include yittrium-88, yittrium-90, technetium-99, copper-67, rhenium-188, rhenium-186, galium-66, galium-67, indium-Ill, indium- 114, indium-115, lutetium-177, strontium-89, sararium-153, and lead-212. PROTACs

[0196] In some embodiments, a Drug unit is a proteolysis targeted chimera (PROTAC). PROTACs are described in, for example, Published US Application Nos. 20210015942, 20210015929, 20200392131, 20200216507, US20200199247 and US20190175612; the disclosures of which are incorporated by reference herein. Ligands

[0197] In some embodiments, a Drug unit includes ligands that can be bound by a Carboxyl unit, such as platinum (Pt), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu), molybdenum (Mo), titanium (Ti), or iridum (Ir); a radioisotope such as yittrium-88, yittrium-90, technetium-99, copper-67, rhenium-188, rhenium-186, galium-66, galium-67, indium-Ill, indium- 114, indium-115, lutetium-177, strontium-89, sararium-153, and lead-212. Drug-Linker Compounds

[0198] In some embodiments, provided are Drug-Linker compounds comprising a Linker compound as described above with at least one Drug unit attached via the attachment site.

[0199] In some embodiments, provided are Drug-Linker compounds comprising a Drug unit is selected from a cytotoxic agent, an immune modulatory agent, a nucleic acid, a growth inhibitory agent, a PROTAC, a toxin, a radioactive isotope and a chelating ligand. In more specific embodiments, the Drug unit is a cytotoxic agent. In more specific embodiments, the cytotoxic agent is selected from the group consisting of an auristatin, a maytansinoid, a camptothecin, a duocarmycin, and a calicheamicin. In some embodiments, the cytotoxic agent is an auristatin. In some embodiments, the cytotoxic agent is MMAE or MMAF. In some embodiments, the cytotoxic agent is SS-exatecan. In some embodiments, the cytotoxic agent is RS-exatecan. In some embodiments, the cytotoxic agent is a camptothecin. In some embodiments, the cytotoxic agent is exatecan or SN-38. In some embodiments, the cytotoxic agent is exatecan. In some embodiments, the cytotoxic agent is DxD. In some embodiments, the cytotoxic agent is a calicheamicin. In some embodiments, the cytotoxic agent is a maytansinoid. In more specific embodiments, the maytansinoid is maytansine, maytansinol or ansamatocin-2.

[0200] In some embodiments, provided are Drug-Linker comopunds comprising a Linker compound as described above with a Drug unit attached via the attachment site, wherein the Drug unit is an immune modulatory agent. For example, in some embodiments the immune modulatory agent is 180 WO 2024 / 149345 PCT / CN2024 / 071901 selected from a TRL7 agonist, a TLR8 agonist, a STING agonist, or a RIG-1 agonist. In more specific embodiments, the immune modulatory agent is an TLR7 agonist. In more specific embodiments, the TLR7 agonist is an imidazoquinoline, an imidazoquinoline amine, a thiazoquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2-d]pyrimidine-2,4-diamine, pyrimidine-2,4-diamine, 2-aminoimidazole, l-alkyl-lH-benzimidazol-2-amine, tetrahydropyridopyrimidine, heteroarothiadiazide-2,2-dioxide, a benzonaphthyridine, a guanosine analog, an adenosine analog, a thymidine homopolymer, ssRNA, CpG-A, PolyGlO, or PolyG3. In certain embodiments, the immune modulatory agent is a TLR8 agonist. In more specific embodiments, the TLR8 agonist is selected from an imidazoquinoline, a thiazoloquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3,2-d]pyrimidine-2,4-diamine, pyrimidine-2,4- diamine, 2-aminoimidazole, l-alkyl-lH-benzimidazol-2-amine, tetrahydropyridopyrimidine or a ssRNA. In some embodiments, the immune modulatory agent is a STING agonist. In other embodiments, the immune modulatory agent is a RIG-1 agonist. For exmaple, in some embodiments, the RIG-1 agonist is selected from KIN1148, SB-9200, KIN700, KIN600, KIN500, KIN100, KIN101, KIN400 and KIN2000.

[0201] In some embodiments, provided are Drug-Linker comopunds comprising a Linker compound as described above with a Drug unit attached via the attachment site, wherein the Drug unit is a chelating ligand. For example, in some embodiments the chelating ligand is selected from platinum (Pt), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu), molybdenum (Mo), titanium (Ti), or iridum (Ir); a radioisotope such as yittrium-88, yittrium-90, technetium-99, copper-67, rhenium-188, rhenium-186, galium-66, galium-67, indium-Ill, indium-114, indium-115, lutetium-177, strontium-89, sararium-153, and lead-212.

[0202] In some embodiments, provided is a Drug-Linker compound, represented by the structure of Formula (A) α Formula (A); or a salt thereof, wherein: (i) β is R20(-R21-[O-CH2-CH2]n20-R22-NR24R25)z; wherein R21 and R22 are each, independently, a bond or C1-C3 alkylene; 181 WO 2024 / 149345 PCT / CN2024 / 071901 R24 and R25 are each independently selected from H; polyhydroxyl group; and -C(O)- polyhydroxyl group; provided that R24 and R25 are not both H; z is 1, or 2; and n20 is 2 to 26; (ii) Ra is H or Ci-C6 alkyl; (iii) Rc is a bond, -C(O)-, -S(O)-, -SO2-, Ci-β alkylene, Ci-6 alkynylene, or Ci-β alkynylene- triazolyl; (iv) R1 is a bond, -C(O)-, or Ci-β alkylene; and (v) δ is selected from a Drug; (vi) a is represented by R2 ; wherein R2 is a peptide having 2-5 amino acids; R3 is -C1-C10 alkylene-C(=O)-, -C1-C10 alkylene-,-Ci-Ci0alkylene-C(O)NH-Ci-C8alkylene-[O- CH2-CH2]n-C(O)- (where n is 1 to 26), or -Ci-C8 alkylene-(CH2-O-CH2)b-C(=O)- (where b is 1 to 26). O H Si A H N \ M2 i F \

[0203] In some embodiments, for a Drug-Linker, R20 is 0

[0204] In some embodiments, for a Drug-Linker, z is 1.

[0205] In some embodiments, for a Drug-Linker, z is 2.

[0206] In some embodiments, for a Drug-Linker, R24 and R25 are each independently selected from a polyhydroxyl group.

[0207] In some embodiments, for a Drug-Linker, R21 is C1-C3 alkylene. In some cases, R21 is C2 alkylene.

[0208] In some embodiments, for a Drug-Linker, R22 is a bond.

[0209] In some embodiments, for a Drug-Linker, β is 182 WO 2024 / 149345 PCT / CN2024 / 071901 and n20 is 4 to 12;

[0210] In some embodiments, for a Drug-Linker, wherein β is

[0211] In some embodiments, for a Drug-Linker, R2 is selected from:

[0212] In some embodiments, for a Drug-Linker, R2 is selected from: 183 WO 2024 / 149345 PCT / CN2024 / 071901

[0213] In some embodiments, for a Drug-Linker, R3 is selected from:

[0214] In some embodiments, for a Drug-Linker, R3 is selected from:

[0215] In some embodiments, for a Drug-Linker, Rc is a -C(O)- or Ci-6 alkynylene-triazolyl;

[0216] In some embodiments, for a Drug-Linker, Rc is -C(O)-.

[0217] In some embodiments, for a Drug-Linker, R1 is -C(O)-.

[0218] In some embodiments, for a Drug-Linker, the Drug is selected from a cytotoxic agent. In some embodiments, the Drug is MMAE or MMAF. In some embodiments, the Drug is MMAE. In some embodiments, the Drug is exatecan.

[0219] In some embodiments, for a Drug-Linker, the Drug is selected from an immune modulatory agent.

[0220] In some embodiments, for a Drug-Linker, δ is selected from 184 WO 2024 / 149345 PCT / CN2024 / 071901 In some embodiments, δ isembodiments, δ is

[0221] In some embodiments, the wavy bond indicates a point of attachment to the Drug-Linker.

[0222] In some embodiments, provided are Drug-Linker compounds selected from following structures: 185 WO 2024 / 149345 PCT / CN2024 / 071901 186 WO 2024 / 149345 PCT / CN2024 / 071901 OH 187 WO 2024 / 149345 PCT / CN2024 / 071901 188 WO 2024 / 149345 PCT / CN2024 / 071901 OH nh2 189 WO 2024 / 149345 PCT / CN2024 / 071901 190 WO 2024 / 149345 PCT / CN2024 / 071901 HO 191 WO 2024 / 149345 PCT / CN2024 / 071901 HO OH 192 WO 2024 / 149345 PCT / CN2024 / 071901 193 WO 2024 / 149345 PCT / CN2024 / 071901 o nh2 194 WO 2024 / 149345 PCT / CN2024 / 071901 195 WO 2024 / 149345 PCT / CN2024 / 071901 196 WO 2024 / 149345 PCT / CN2024 / 071901 197 WO 2024 / 149345 PCT / CN2024 / 071901 198 WO 2024 / 149345 PCT / CN2024 / 071901 199 WO 2024 / 149345 PCT / CN2024 / 071901 200 WO 2024 / 149345 PCT / CN2024 / 071901 201 WO 2024 / 149345 PCT / CN2024 / 071901 202 WO 2024 / 149345 PCT / CN2024 / 071901 203 WO 2024 / 149345 PCT / CN2024 / 071901 OH NH NH2 NH NH O^NH2 204 WO 2024 / 149345 PCT / CN2024 / 071901 OH nh2 OH OH OH OH 205 WO 2024 / 149345 PCT / CN2024 / 071901 206 WO 2024 / 149345 PCT / CN2024 / 071901 207 WO 2024 / 149345 PCT / CN2024 / 071901

[0223] In some embodiments, the Drug-Linker may be a stereoisomer of one of the above structures. Targeting Groups

[0224] In some embodiments, the Linkers are attached to Targeting groups (also described herein as “Targeting units”) to form Targeting unit-Linkers. In some embodiments, the Linkers are attached to Targeting groups via a Stretcher unit and to a Drug unit(s) via the attachment site δ to form a conjugate. In some embodiments, a Targeting group is a protein, polypeptide or peptide. The Targeting groups can be antibodies, antigen binding portions thereof or non-antibody targeting groups. Non-antibody targeting groups may also be referred to as non-antibody scaffolds.

[0225] In some embodiments, a Targeting group specifically binds to a target molecule. As used herein, "specifically binds" refers to the ability of a Targeting group (e.g., an antibody or portion thereof) described herein to bind to a target with a KD 10-5 M (10000 nM) or less, e.g., 10-6 Μ, 10-7 Μ, ΙΟ-8 Μ, ΙΟ-9 Μ, 10'10 Μ, 10-11 Μ, IO'12 M, or less. Specific binding can be influenced by, for example, the affinity and avidity of the Targeting group and the concentration of target polypeptide. The person of ordinary skill in the art can determine appropriate conditions under which the antibodies, antibody binding portions and non-antibody scaffolds described herein selectively bind to a target using any suitable methods, such as titration of a binding agent in a suitable cell binding 208 WO 2024 / 149345 PCT / CN2024 / 071901 assay. A Targeting group specifically bound to its target is not displaced by a non-similar competitor. In certain embodiments, a Targeting unit is said to specifically bind to its target when it preferentially recognizes its target in a complex mixture of proteins and / or macromolecules.

[0226] As used herein, the term "antibody" refers to an immunoglobulin molecule and immunologically active portions of immunoglobulin molecules, i.e., molecules that contain an antigen binding site(s) that specifically bind(s) to a target antigen. The term generally refers to antibodies comprised of two immunoglobulin heavy chain variable regions and two immunoglobulin light chain variable regions including full length antibodies (having heavy and light chain constant regions).

[0227] Each heavy chain is typically composed of a variable region (abbreviated as a VH region) and a constant region. The heavy chain constant region may include three domains CHI, CH2 and CH3 and optionally a fourth domain, CH4. Each light chain is composed of a variable region (abbreviated as a VL region) and a constant region. The light chain constant region is a CL domain. The VH and VL regions may be further divided into hypervariable regions referred to as complementarity-determining regions (CDRs) and interspersed with conserved regions referred to as framework regions (FR). Each VH and VL region thus includes three CDRs and four FRs that are arranged from the N terminus to the C terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, and FR4. This structure is well known to those skilled in the art.

[0228] As used herein, an "antigen-binding portion" of an antibody refers to the portions of an antibody having VH and / or VL sequences of an antibody or the CDRs of an antibody and that specifically binds to the target antigen. Examples of antigen binding portions include a Fab, a Fab', a F(ab')2, a Fv, a scFv, a disulfide linked Fv, a single domain antibody (also referred to as a VHH, VNAR, sdAb, or nanobody) or a diabody (see, e.g., Huston et al., Proc. Natl. Acad. Sci. U.S.A., 85, 5879-5883 (1988) and Bird et al., Science 242, 423-426 (1988), which are incorporated herein by reference). As used herein, the terms Fab, F(ab’)2 and Fv refer to the following: (i) a Fab is a monovalent fragment composed of the VL, VH, CL and CHI domains; (ii) a F(ab')2 is a bivalent fragment comprising two Fab fragments linked to one another in the hinge region via a disulfide bridge; and (iii) a Fv composed of the VL and VH domains. Although the two domains of the Fv fragment, namely VL and VH, are encoded by separate coding regions, they may further be linked to one another using a synthetic linker, e.g., a poly-G4S amino acid sequence ('(G4S)n, disclosed as SEQ ID NO: 1, wherein n =1 to 5), making it possible to prepare them as a single protein chain in which the VL and VH regions combine in order to form monovalent molecules (known as single chain Fv or scFv). The term "antigen-binding portion" of an antibody is also intended to include such single chain antibodies. Other forms of single chain antibodies such as "diabodies" are likewise included here. Diabodies are bivalent, bispecific antibodies in which VH and VL regions are expressed on a single polypeptide chain, but using a linker connecting the VH and VL regions that is too short for the two regions to be able to combine on the same chain, thereby forcing the VH and VL regions to pair with complementary regions of a different chain (VL and VH, respectively), and to form two antigen-binding sites (see, for example, Holliger, R, et al. (1993) Proc. Natl. Acad. Sci. USA 90:64446448; Poljak, R. J, et al. (1994) Structure 2:1121-1123).

[0229] A single-domain antibody is an antigen binding portion of an antibody containing a single 209 WO 2024 / 149345 PCT / CN2024 / 071901 monomeric variable antibody region. Single domains antibodies can be derived from the variable region of the antibody heavy chain from camelids (e.g., nanobodies or VHH portions). Furthermore, the term single-domain antibody includes an autonomous human heavy chain variable domain (aVH) or VNAR portions derived from sharks (see, e.g., Hasler et al., Mol. Immunol. 75:28-37, 2016).

[0230] Techniques for producing single domain antibodies (e.g., DABs or VHH) are known in the art, as disclosed for example in Cossins et al. (2006, Prot Express Purif 51:253-259) and Li et al. (Immunol. Lett. 188:89-95, 2017). Single domain antibodies may be obtained, for example, from camels, alpacas or llamas by standard immunization techniques. (See, e.g., Muyldermans et al., TIBS 26:230-235, 2001; Yau et al., J Immunol Methods 281:161-75, 2003; and Maass et al., J Immunol Methods 324:13-25, 2007.) A VHH may have potent antigen-binding capacity and can interact with novel epitopes that are inaccessible to conventional VH-VL pairs (see, e.g., Muyldermans et aL, 2001). Alpaca serum IgG contains about 50% camelid heavy chain only IgG antibodies (HCAbs) (see, e.g., Maass et al., 2007). Alpacas may be immunized with antigens and VHHs can be isolated that bind to and neutralize a target antigen (see, e.g., Maass et al., 2007). PCR primers that amplify alpaca VHH coding sequences have been identified and may be used to construct alpaca VHH phage display libraries, which can be used for antibody fragment isolation by standard biopanning techniques well known in the art (see, e.g., Maass et al., 2007).

[0231] In some embodiments, the Targeting group is an antibody or antigen binding portion thereof is a bispecific or multispecific binding agent. Bispecific and multi-specific antibodies include the following: an scFvl-ScFv2, an ScFvl2-Fc-scFv22, an IgG-scFv, a DVD-lg, a triomab / quadroma, a two-in-one IgG, a scFv2-Fc, a TandAb, and an scFv-HSA-scFv. In some embodiments, an IgG-scFv is an lgG(H)-scFv, scFv-(H)lgG, lgG(L)-scFv, svFc-(L)lgG, 2scFV-lgG or lgG-2scFv. See, e.g., Brinkmann and Kontermann, MAbs 9(2):182-212 (2017); Wang et aL, Antibodies, 2019, 8, 43; Dong et aL, 2011, MAbs 3:273-88; Natsume et aL, J. Biochem. 140(3):359-368, 2006; Cheal et aL, MoL Cancer Ther. 13(7):1803-1812, 2014; and Bates and Power, Antibodies, 2019, 8, 28.

[0232] In some embodiments, the Targeting group specifically binds to a cancer associated antigen such as CD19, CD20, CD30, CD33, CD38, CA125, HER2, MUC-1, prostate-specific membrane antigen (PSMA), CD44 surface adhesion molecule, mesothelin (MLSN), carcinoembryonic antigen (CEA), epidermal growth factor receptor (EGFR), EGFRvlll, vascular endothelial growth factor receptor-2 (VEGFR2), high molecular weight-melanoma associated antigen (HMW-MAA), MAGE- Al, IL-13R-a2, GD2, lpl9q, ABL1, AKT1, ALK, APC, AR, ATM, BRAF, BRCA1, BRCA2, cKIT, cMET, CSF1R, CTNNB1, FGFR1, FGFR2, FLT3, GNA11, GNAQ, GNAS, HRAS, IDH1, IDH2, JAK2, KDR (VEGFR2), KRAS, MGMT, MGMT-Me, MLH1, MPL, NOTCH1, NRAS, PDGFRA, Pgp, PIK3CA, PR, PTEN, RET, RRM1, SMO, SPARC, TLE3, TOP2A, TOPO1, TP53, TS, TUBB3, VHL, CDH1, ERBB4, FBXW7, HNF1A, JAK3, NPM1, PTPN11, RBI, SMAD4, SMARCB1, STK1, MLH1, MSH2, MSH6, PMS2, ROS1, ERCC1, 5T4 (TPBG), B7-H3, CCR7, CD105, CD22, CD46, CD47, CD56, CD70, CD71, CD79b, CDH6, CLDN6, CLDN18.2, CLEC12A, DLL3, DR5, ERBB3 (HER3), EPCAM, FOLRI, IGF1R, IL2RA (CD25), IL3RA, ITGB6, LIV-1, LRRC15, mesothelin (MSLN), NaPi2b (SLC34A2), nectin-4, PTK7, ROR1, SEZ6, SLC44A4, SLITRK6, Tissue Factor (TF), TROP2 or B7-H4. According to the invention, the terms "cancer associated antigen," "tumor antigen," "tumor 210 WO 2024 / 149345 PCT / CN2024 / 071901 expressed antigen," "cancer antigen," "cancer associated antigen," and "cancer expressed antigen" are equivalents and are used interchangeably herein.

[0233] In some embodiments, a Targeting group specifically binds to a target such as CD19, CD20, CD30, CD33, CD70, LIV-1 or EGFRv3.

[0234] In some embodiments, the Targeting group is an antibody (or fragment thereof) that binds to a target having a sequence as disclosed in Leuschner et al., US 2022 / 0048951 and / or Lerchen et al., US 2022 / 0016258. Non-limiting examples of monoclonal antibodies include rituximab (Rituxan®), trastuzumab (Herceptin®), pertuzumab (Perjeta®)), bevacizumab (Avastin®), ranibizumab (Lucentis®), cetuximab (Erbitux®), alemtuzumab (Campath®), panitumumab (Vectibix®), ibritumomab (Zevalin®), tositumomab (Bexxar®), ipilimumab, zalutumumab, dalotuzumab, figitumumab, ramucirumab, galiximab, farletuzumab, ocrelizumab, ofatumumab (Arzerra®), the CD20 antibodies 2F2 (HuMax-CD20), 7D8, lgM2C6, IgGl 2C6, 11B8, Bl, 2H7, LT20, IES or AT80 (see Teeling et al., J. Immunol. 177:362-371 (2006)), daclizumab (Zenapax®), and anti-LHRH receptor antibodies such as clones A9E4, F1G4, AT2G7, GNRH03, GNRHR2, etc. which can be used in combination with, inter alia, a conjugate in accordance with the invention.

[0235] In some embodiments, a Targeting group is a non-antibody scaffold. Such non-antibody scaffolds include, for example, Affibodies, Affilins, Anticalins, Atrimers, Avimers, Bicyclic peptides, Cys-knots, DARPins, FN3 scaffolds (e.g., Adnectins, Centyrins, Pronectins, and Tn3), Fynomers, Kunitz domains and OBodies. (See, e.g., Vazquez-Lombardi et al., Drug Discovery Today 20(10):1271 (2015) and the references cited therein.) Such Non-antibody protein scaffolds include, for example, Affibodies, Affilins, Anticalins, Atrimers, Avimers, Bicyclic peptides, Cys-knots, DARPins, FN3 scaffolds (e.g., Adnectins, Centyrins, Pronectins, and Tn3), Fynomers, Kunitz domains and OBodies. (See, e.g., Vazquez-Lombardi et al., Drug Discovery Today 20(10):1271 (2015) and the references cited therein.) Non-antibody scaffolds can be considered to fall into two structural categories, domain-sized constructs (in the range of 6 to 20 kDa), and constrained peptides (in the 2-4 kDa range). Domain-sized non-antibody scaffolds include, but are not limited to, affibodies, affilins, anticalins, atrimers, DARPins, FN3 scaffolds (such as adnectins and centyrins), fynomers, Kunitz domains, pronectins and OBodies. Peptide-sized non-antibody scaffolds include, for example, avimers, bicyclic peptides and cysteine knots. Non-antibody protein scaffolds can be considered to fall into two structural categories, domain-sized constructs (in the range of 6 to 20 kDa), and constrained peptides (in the 2-4 kDa range). Domain-sized non-antibody scaffolds include, but are not limited to, affibodies, affilins, anticalins, atrimers, DARPins, FN3 scaffolds (such as adnectins and centyrins), fynomers, Kunitz domains, pronectins and OBodies. Peptide-sized non­ antibody scaffolds include, for example, avimers, bicyclic peptides and cysteine knots. These non­ antibody scaffolds and the underlying proteins or peptides on which they are based or from which they have been derived are reviewed by, e.g., Simeon and Chen, Protein Cell 9(1): 3-14 (2018); Vazquez-Lombardi et al., Drug Discovery Today 20: 1271-1283 (2015), and by Binz et aL, Nature Biotechnol. 23: 1257-1268 (2005), the contents of each of which are herein incorporated by reference in their entireties.

[0236] Advantages of using non-antibody scaffolds include increased affinity, target neutralization, 211 WO 2024 / 149345 PCT / CN2024 / 071901 and stability. Various non-antibody scaffolds also can overcome some of the limitations of antibody scaffolds, e.g., in terms of tissue penetration, smaller size, and thermostability. Some non-antibody scaffolds can also permit easier construction, not being hindered, for example, by potential light chain association concerns when bispecific constructs are desired. Methods of constructing constructs on a non-antibody scaffold are known to those of ordinary skill in the art.

[0237] Accordingly, in some embodiments, a Targeting group can comprise a non-antibody scaffold. Accordingly, in some embodiments, a Targeting group can comprise a non-antibody scaffold protein. One of skill in the art would appreciate that a Targeting group can include, in some embodiments, e.g., an adnectin scaffold or a portion derived from human tenth fibronectin type III domain (10Fn3); an anticalin scaffold derived from human lipocalin (e.g., such as those described in, e.g., WO2015 / 104406); an avimer scaffold or a protein fragment derived from the A-domain of low density-related protein (LRP) and / or very low density lipoprotein receptor (VLDLR); a fynomer scaffold or portion of the SH3 domain of FYN tyrosine kinase; a kunitz domain scaffold or portion of Kunitz-type protease inhibitors, such as a human trypsin inhibitor, aprotinin (bovine pancreatic trypsin inhibitor), Alzheimer’s amyloid precursor protein, and tissue factor pathway inhibitor; a knottin scaffold (cysteine knot miniproteins), such as one based on a trypsin inhibitor from E. elaterium; an affibody scaffold or all or part of the Z domain of S. aureus protein A; a β-Hairpin mimetic scaffold; a Designed ankyrin repeat protein (DARPin) scaffold or artificial protein scaffolds based on ankyrin repeat (AR) proteins; or any scaffold derived or based on human transferrin, human CTLA-4, human crystallin, and human ubiquitin. For example, the binding site of human transferrin for human transferrin receptor can be diversified to create a diverse library of transferrin variants, some of which have acquired affinity for different antigens. See, e.g., Ali et al. (1999) J. Biol. Chern. 274:24066-24073. The portion of human transferrin not involved with binding the receptor remains unchanged and serves as a scaffold, like framework regions of antibodies, to present the variant binding sites. The libraries are then screened, as an antibody library is, and in accordance with the methods described herein, against a target antigen of interest to identify those variants having optimal selectivity and affinity for the target antigen. See, e.g., Hey et al. (2005) TRENDS Biotechnol. 23(10):514-522. Constant Regions

[0238] In some embodiments, a Targeting group, such as an antibody or antigen-binding portion thereof or other Targeting group, has an antibody constant region(s). In some embodiments, the constant region is a fully human constant region(s). In some embodiments, the constant region is a humanized constant region(s). In some embodiments, the constant region is a non-human constant region(s). An immunoglobulin constant region refers to a heavy or light chain constant region. Human heavy chain and light chain constant region amino acid sequences are known in the art. A constant region can be of any suitable type, which can be selected from the classes of immunoglobulins, IgA, IgD, IgE, IgG, and IgM. Several immunoglobulin classes can be further divided into isotypes, e.g., IgGl, lgG2, lgG3, lgG4, or IgAI, and lgA2. The heavy-chain constant regions (Fc) that correspond to the different classes of immunoglobulins can be α, δ, ε, γ, and μ, respectively. The light chains can be one of either kappa (or k ) and lambda (or λ). 212 WO 2024 / 149345 PCT / CN2024 / 071901

[0239] In some embodiments, a constant region can have an IgG isotype. In some embodiments, a constant region can have an IgGl isotype. In some embodiments, a constant region can have an lgG2 isotype. In some embodiments, a constant region can have an lgG3 isotype. In some embodiments, a constant region can have an lgG4 isotype. In some embodiments, a constant region can have a hybrid isotype comprising constant regions from two or more isotypes. In some embodiments, an immunoglobulin constant region can be an IgGl or lgG4 constant region. In some embodiments, a constant region is of the IgGl isotype and has the amino acid sequence set forth in SEQ ID NO:2. In some embodiments, a constant region is of the kappa isotype and has the amino acid sequence set forth in SEQ ID NO:3.

[0240] Furthermore, a Targeting group comprising an antibody or an antigen-binding portion thereof or non-antibody scaffold may be part of a larger molecule formed by covalent or noncovalent association of the antibody or antigen binding portion with one or more other proteins or peptides. Relevant to such Targeting groups are the use, for example, of the streptavidin core region in order to prepare a tetrameric scFv molecule (Kipriyanov, S. M., et al. (1995), Human Antibodies and Hybridomas 6:93-101) and the use of a cysteine residue, a marker peptide and a C-terminal polyhistidinyl peptide, e.g. hexahistidinyl tag ('hexahistidinyl tag' disclosed as SEQ ID NO: 4) in order to produce bivalent and biotinylated scFv molecules (Kipriyanov, S. M., et al. (1994) Mol. Immunol. 31:10471058). Fc Domain Modifications to Alter Effector Function

[0241] In some embodiments, an Fc region or Fc domain of a Targeting group, such as an antibody or antigen binding portion thereof or non-antibody scaffold, has substantially no binding to at least one Fc receptor selected from FcyRI (CD64), FcyRIIA (CD32a), FcyRIIB (CD32b), FcyRIIIA (CD16a), and FcyRI I IB (CD16b). In some embodiments, an Fc region or domain exhibits substantially no binding to any of the Fc receptors selected from FcyRI (CD64), FcyRIIA (CD32a), FcyRIIB (CD32b), FcyRIIIA (CD16a), and FcyRI I IB (CD16b). As used herein, “substantially no binding” refers to weak to no binding to a selected Fcgamma receptor or receptors. In some embodiments, “substantially no binding” refers to a reduction in binding affinity (i.e., increase in Kd) to a Fc gamma receptor of at least 1000-fold. In some embodiments, an Fc domain or region is an Fc null. As used herein, an “Fc null” refers to an Fc region or Fc domain that exhibits weak to no binding to any of the Fcgamma receptors. In some embodiments, an Fc null domain or region exhibits a reduction in binding affinity (i.e., increase in Kd) to Fc gamma receptors of at least 1000- fold.

[0242] In some embodiments, an Fc domain has reduced or substantially no effector function activity. As used herein, “effector function activity” refers to antibody dependent cellular cytotoxicity (ADCC), antibody dependent cellular phagocytosis (ADCP) and / or complement dependent cytotoxicity (CDC). In some embodiments, an Fc domain exhibits reduced ADCC, ADCP or CDC activity, as compared to a wildtype Fc domain. In some embodiments, an Fc domain exhibits a reduction in ADCC, ADCP and CDC, as compared to a wildtype Fc domain. In some embodiments, an Fc domain exhibits substantially no effector function (i.e., the ability to stimulate or effect ADCC, ADCP or CDC). As used herein, “substantially no effector function” refers to a reduction in effector 213 WO 2024 / 149345 PCT / CN2024 / 071901 function activity of at least 1000-fold, as compared to a wildtype or reference Fc domain.

[0243] In some embodiments, an Fc domain has reduced or no ADCC activity. As used herein reduced or no ADCC activity refers to a decrease in ADCC activity of an Fc domain by a factor of at least 10, at least 20, at least 30, at least 50, at least 100 or at least 500.

[0244] In some embodiments, an Fc domain has reduced or no CDC activity. As used herein reduced or no CDC activity refers to a decrease in CDC activity of an Fc domain by a factor of at least 10, at least 20, at least 30, at least 50, at least 100 or at least 500.

[0245] In vitro and / or in vivo cytotoxicity assays can be conducted to confirm the reduction / depletion of ADCC and / or CDC activity. For example, Fc receptor (FcR) binding assays can be conducted to ensure that the antibody lacks Fcgamma receptor binding (hence likely lacking ADCC activity). The primary cells for mediating ADCC, NK cells, express FcgammaRIII only, whereas monocytes express FcgammaRI, FcgammaRII and FcgammaRIII. FcR expression on hematopoietic cells is summarized in Table 3 on page 464 of Ravetch and Kinet, Annu. Rev. Immunol. 9:457-492 (1991). Non-limiting examples of in vitro assays to assess ADCC activity of a molecule of interest are described in U.S. Pat. No. 5,500,362 (see, e.g. Hellstrom, I. et al. Proc. Nat'l Acad. Sci. USA 83:7059-7063 (1986)) and Hellstrom, I et al., Proc. Nat'l Acad. Sci. USA 82:1499-1502 (1985); U.S. Pat. No. 5,821,337 (see Bruggemann, M. et al., J. Exp. Med. 166:1351-1361 (1987)). Alternatively, non-radioactive assay methods may be employed (see, for example, ACTI™ non-radioactive cytotoxicity assay for flow cytometry (CellTechnology, Inc. Mountain View, Calif.; and CytoTox 96™ non-radioactive cytotoxicity assay (Promega, Madison, Wis.). Useful effector cells for such assays include peripheral blood mononuclear cells (PBMC) and Natural Killer (NK) cells. Alternatively, or additionally, ADCC activity of the molecule of interest may be assessed in vivo, e.g., in an animal model such as that disclosed in Clynes et al., Proc. Nat'l Acad. Sci. USA 95:652-656 (1998).

[0246] Clq binding assays may also be carried out to confirm that an antibody or Fc domain or region is unable to bind Clq and hence lacks CDC activity or has reduced CDC activity. See, e.g., Clq and C3c binding ELISA in WO 2006 / 029879 and WO 2005 / 100402. To assess complement activation, a CDC assay may be performed (see, for example, Gazzano-Santoro et al., J. Immunol. Methods 202:163 (1996); Cragg, M. S. et al., Blood 101:1045-1052 (2003); and Cragg, M. S. and M. J. Glennie, Blood 103:2738-2743 (2004)).

[0247] In some embodiments, an Fc domain has reduced or no ADCP activity. As used herein reduced or no ADCP activity refers to a decrease in ADCP activity of an Fc domain by a factor of at least 10, at least 20, at least 30, at least 50, at least 100 or at least 500.

[0248] ADCP binding assays may also be carried out to confirm that an antibody or Fc domain or region lacks ADCP activity or has reduced ADCP activity. See, e.g., US20190079077 and US20190048078 and the references disclosed therein.

[0249] A Targeting group, such as an antibody or antigen binding portion thereof or non-antibody scaffold, with reduced effector function activity includes those with substitution of one or more of Fc region residues, such as, for example, 238, 265, 269, 270, 297, 327 and 329, according to the EU number of Kabat (see, e.g., U.S. Pat. No. 6,737,056). Such Fc mutants include Fc mutants with substitutions at two or more of amino acid positions 265, 269, 270, 297 and 327, including the so- 214 WO 2024 / 149345 PCT / CN2024 / 071901 called "DANA" Fc mutant with substitution of residues 265 and 297 to alanine, according to the EU numbering of Kabat (see U.S. Pat. No. 7,332,581). Certain antibody variants with diminished binding to FcRs are also known. (See, e.g., U.S. Pat. No. 6,737,056; WO 2004 / 056312, and Shields et al., J. Biol. Chern. 9(2): 6591-6604 (2001).) A Targeting group, such as an antibody or antigen binding portion thereof or non-antibody scaffold, with diminished binding to FcRs can be prepared containing such amino acid modifications.

[0250] In some embodiments, a Targeting group, such as an antibody or antigen binding portion thereof or non-antibody scaffold, comprises an Fc domain or region with one or more amino acid substitutions which diminish FcgammaR binding, e.g., substitutions at positions 234 and 235 of the Fc region (EU numbering of residues). In some embodiments, the substitutions are L234A and L235A (LALA), according to the EU numbering of Kabat. In some embodiments, the Fc domain comprises D265A and / or P329G in an Fc region derived from a human IgGl Fc region, according to the EU numbering of Kabat. In some embodiments, the substitutions are L234A, L235A and P329G (LALA-PG), according to the EU numbering of Kabat, in an Fc region derived from a human IgGl Fc region. (See, e.g., WO 2012 / 130831). In some embodiments, the substitutions are L234A, L235A and D265A (LALA-DA) in an Fc region derived from a human IgGl Fc region, according to the EU numbering of Kabat.

[0251] In some embodiments, alterations are made in the Fc region that result in altered (i.e., either diminished) Clq binding and / or Complement Dependent Cytotoxicity (CDC), e.g., as described in U.S. Pat. No. 6,194,551, WO 99 / 51642, and Idusogie et al. J. Immunol. 164: 4178-4184 (2000). Methods of Making Antibodies and Antigen Binding Portions and Other Targeting groups

[0252] In various embodiments, Targeting groups such as antibodies and antigen binding portions thereof, can be produced in human, murine or other animal-derived cells lines. Recombinant DNA expression can be used to produce antibodies and antigen binding portions thereof. This allows the production of antibodies as well as a spectrum of antigen binding portions (including fusion proteins) in a host species of choice. The production of antibodies and antigen binding portions thereof in bacteria, yeast, transgenic animals and chicken eggs are also alternatives for cell-based production systems. The main advantages of transgenic animals are potential high yields from renewable sources.

[0253] Nucleic acid molecules encoding the amino acid sequence(s) of Targeting group, such as an antibody or antigen binding portion thereof can be prepared by a variety of methods known in the art. These methods include, but are not limited to, preparation of synthetic nucleotide sequences encoding of an antibody or antigen binding portion. In addition, oligonucleotide-mediated (or site- directed) mutagenesis, PCR-mediated mutagenesis, and cassette mutagenesis can be used to prepare nucleotide sequences encoding an antibody or antigen binding portion. A nucleic acid sequence encoding at least an antibody or antigen binding portion thereof, or a polypeptide thereof, as described herein, can be recombined with vector DNA in accordance with conventional techniques, such as, for example, blunt-ended or staggered-ended termini for ligation, restriction enzyme digestion to provide appropriate termini, filling in of cohesive ends as appropriate, alkaline phosphatase treatment to avoid undesirable joining, and ligation with appropriate ligases or other 215 WO 2024 / 149345 PCT / CN2024 / 071901 techniques known in the art. Techniques for such manipulations are disclosed, e.g., by Maniatis et al., Molecular Cloning, Lab. Manual (Cold Spring Harbor Lab. Press, NY, 1982 and 1989), and Ausubel et al., Current Protocols in Molecular Biology (John Wiley & Sons), 1987-1993, and can be used to construct nucleic acid sequences and vectors that encode an antibody or antigen binding portion thereof or a VH or VL polypeptide thereof.

[0254] As used herein, the terms "nucleic acid" or "nucleic acid sequence" or “polynucleotide sequence” or “nucleotide” refers to a polymeric molecule incorporating units of ribonucleic acid, deoxyribonucleic acid or an analog thereof. The nucleic acid can be either single-stranded or double-stranded. A single-stranded nucleic acid can be one strand nucleic acid of a denatured double-stranded DNA. In some embodiments, the nucleic acid can be a cDNA, e.g., a nucleic acid lacking introns.

[0255] A nucleic acid molecule, such as DNA, is said to be "capable of expressing" a polypeptide if it contains nucleotide sequences that contain transcriptional and translational regulatory information and such sequences are "operably linked" to nucleotide sequences that encode the polypeptide. An operable linkage is a linkage in which the regulatory DNA sequences and the DNA sequence sought to be expressed (e.g., an antibody or antigen binding portion thereof) are connected in such away as to permit gene expression of a polypeptide(s) or antigen binding portions in recoverable amounts. The precise nature of the regulatory regions needed for gene expression may vary from organism to organism, as is well known in the analogous art. See, e.g., Sambrook et al., 1989; Ausubel et al., 1987-1993.

[0256] Accordingly, the expression of a Targeting group, such as an antibody or antigen-binding portion thereof, can occur in either prokaryotic or eukaryotic cells. Suitable hosts include bacterial or eukaryotic hosts, including yeast, insects, fungi, bird and mammalian cells either in vivo or in situ, or host cells of mammalian, insect, bird or yeast origin. The mammalian cell or tissue can be of human, primate, hamster, rabbit, rodent, cow, pig, sheep, horse, goat, dog or cat origin, but other mammalian cells may be used. Further, by use of, for example, the yeast ubiquitin hydrolase system, in vivo synthesis of ubiquitin-transmembrane polypeptide fusion proteins can be accomplished. The fusion proteins so produced can be processed in vivo or purified and processed in vitro, allowing synthesis of an antibody or antigen binding portion thereof as described herein with a specified amino terminus sequence. Moreover, problems associated with retention of initiation codon-derived methionine residues in direct yeast (or bacterial) expression maybe avoided. (See, e.g., Sabin et al., 7 Bio / Technol. 705 (1989); Miller et al., 7 Bio / Technol. 698 (1989).) Any of a series of yeast gene expression systems incorporating promoter and termination elements from the actively expressed genes coding for glycolytic enzymes produced in large quantities when yeast is grown in medium rich in glucose can be utilized to obtain recombinant antibodies or antigen-binding portions thereof. Known glycolytic genes can also provide very efficient transcriptional control signals. For example, the promoter and terminator signals of the phosphoglycerate kinase gene can be utilized.

[0257] Production of antibodies or antigen-binding portions in insects can be achieved, for example, by infecting an insect host with a baculovirus engineered to express a polypeptide by methods known to those of ordinary skill in the art. See Ausubel et al., 1987-1993. 216 WO 2024 / 149345 PCT / CN2024 / 071901

[0258] In some embodiments, the introduced nucleic acid sequence(s) (encoding an antibody or antigen binding portion thereof or a polypeptide thereof) is incorporated into a plasmid or viral vector capable of autonomous replication in a recipient host cell. Any of a wide variety of vectors can be employed for this purpose and are known and available to those of ordinary skill in the art. See, e.g., Ausubel et al., 1987-1993. Factors of importance in selecting a particular plasmid or viral vector include: the ease with which recipient cells that contain the vector may be recognized and selected from those recipient cells which do not contain the vector; the number of copies of the vector which are desired in a particular host; and whether it is desirable to be able to "shuttle" the vector between host cells of different species.

[0259] Exemplary prokaryotic vectors known in the art include plasmids such as those capable of replication in E. coli. Other gene expression elements useful for the expression of DNA encoding antibodies or antigen-binding portions thereof include, but are not limited to (a) viral transcription promoters and their enhancer elements, such as the SV40 early promoter. (Okayama et al., 3 Mol. Cell. Biol. 280 (1983)), Rous sarcoma virus LTR (Gorman et al., 79 PNAS 6777 (1982)), and Moloney murine leukemia virus LTR (Grosschedl et aL, 41 Cell 885 (1985)); (b) splice regions and polyadenylation sites such as those derived from the SV40 late region (Okayarea et al., 1983), and (c) polyadenylation sites such as in SV40 (Okayama et al., 1983). Immunoglobulin-encoding DNA genes can be expressed as described by Liu et al., infra, and Weidle et al., 51 Gene 21 (1987), using as expression elements the SV40 early promoter and its enhancer, the mouse immunoglobulin H chain promoter enhancers, SV40 late region mRNA splicing, rabbit S-globin intervening sequence, immunoglobulin and rabbit S-globin polyadenylation sites, and SV40 polyadenylation elements.

[0260] For immunoglobulin encoding nucleotide sequences, the transcriptional promoter can be, for example, human cytomegalovirus, the promoter enhancers can be cytomegalovirus and mouse / human immunoglobulin.

[0261] In some embodiments, for expression of DNA coding regions in rodent cells, the transcriptional promoter can be a viral LTR sequence, the transcriptional promoter enhancers can be either or both the mouse immunoglobulin heavy chain enhancer and the viral LTR enhancer, and the polyadenylation and transcription termination regions. In other embodiments, DNA sequences encoding other proteins are combined with the above-recited expression elements to achieve expression of the proteins in mammalian cells.

[0262] Each coding region or gene fusion is assembled in, or inserted into, an expression vector. Recipient cells capable of expressing the variable region(s) or antigen binding portions thereof are then transfected singly with nucleotides encoding an antibody or an antibody polypeptide or antigen­ binding portion thereof, or are co-transfected with a polynucleotide(s) encoding VH and VL chain coding regions. The transfected recipient cells are cultured under conditions that permit expression of the incorporated coding regions and the expressed antibody chains or intact antibodies or antigen binding portions are recovered from the culture.

[0263] In some embodiments, the nucleic acids containing the coding regions encoding an antibody or antigen-binding portion thereof are assembled in separate expression vectors that are then used to co-transfect a recipient host cell. Each vector can contain one or more selectable genes. For 217 WO 2024 / 149345 PCT / CN2024 / 071901 example, in some embodiments, two selectable genes are used, a first selectable gene designed for selection in a bacterial system and a second selectable gene designed for selection in a eukaryotic system, wherein each vector has a set of coding regions. This strategy results in vectors which first direct the production, and permit amplification, of the nucleotide sequences in a bacterial system. The DNA vectors so produced and amplified in a bacterial host are subsequently used to co­ transfect a eukaryotic cell, and allow selection of a co-transfected cell carrying the desired transfected nucleic acids (e.g., containing antibody heavy and light chains). Non-limiting examples of selectable genes for use in a bacterial system are the gene that confers resistance to ampicillin and the gene that confers resistance to chloramphenicol. Selectable genes for use in eukaryotic transfectants include the xanthine guanine phosphoribosyl transferase gene (designated gpt) and the phosphotransferase gene from Tn5 (designated neo). Alternatively, the fused nucleotide sequences encoding VH and VL chains can be assembled on the same expression vector.

[0264] For transfection of the expression vectors and production of antibodies or antigen binding portions thereof, the recipient cell line can be a Chinese Hamster ovary cell line (e.g., DG44) or a myeloma cell. Myeloma cells can synthesize, assemble and secrete immunoglobulins encoded by transfected immunoglobulin genes and possess the mechanism for glycosylation of the immunoglobulin. For example, in some embodiments, the recipient cell is the recombinant Ig- producing myeloma cell SP2 / 0. SP2 / 0 cells only produce immunoglobulins encoded by the transfected genes. Myeloma cells can be grown in culture or in the peritoneal cavity of a mouse, where secreted immunoglobulin can be obtained from ascites fluid.

[0265] An expression vector encoding an antibody or antigen-binding portion thereof can be introduced into an appropriate host cell by any of a variety of suitable means, including such biochemical means as transformation, transfection, protoplast fusion, calcium phosphate­ precipitation, and application with polycations such as diethylaminoethyl (DEAE) dextran, and such mechanical means as electroporation, direct microinjection and microprojectile bombardment, as known to one of ordinary skill in the art. (See, e.g., Johnston et al., 240 Science 1538 (1988)).

[0266] Yeast provides certain advantages over bacteria for the production of immunoglobulin heavy and light chains. Yeasts carry out post-translational peptide modifications including glycosylation. A number of recombinant DNA strategies exist that utilize strong promoter sequences and high copy number plasmids which can be used for production of the desired proteins in yeast. Yeast recognizes leader sequences of cloned mammalian gene products and secretes polypeptides bearing leader sequences (i.e., pre-polypeptides). See, e.g., Hitzman et al., 11th Inti. Conf. Yeast, Genetics & Molec. Biol. (Montpelier, France, 1982).

[0267] Yeast gene expression systems can be routinely evaluated for the levels of production, secretion and the stability of antibodies, and assembled antibodies and antigen binding portions thereof. Various yeast gene expression systems incorporating promoter and termination elements from the actively expressed genes coding for glycolytic enzymes produced in large quantities when yeasts are grown in media rich in glucose can be utilized. Known glycolytic genes can also provide very efficient transcription control signals. For example, the promoter and terminator signals of the phosphoglycerate kinase (PGK) gene can be utilized. Another example is the translational 218 WO 2024 / 149345 PCT / CN2024 / 071901 elongation factor lalpha promoter, such as that from Chinese hamster cells. A number of approaches can be taken for evaluating optimal expression plasmids for the expression of immunoglobulins in yeast. See II DNA Cloning 45, (Glover, ed., IRL Press, 1985) and e.g., U.S. Publication No. US 2006 / 0270045 Al.

[0268] Bacterial strains can also be utilized as hosts for the production of the antibody molecules or antigen binding portions thereof as described herein. E. coli K12 strains such as E. coli W3110, Bacillus species, enterobacteria such as Salmonella typhimurium or Serratia marcescens, and various Pseudomonas species can be used. Plasmid vectors containing replicon and control sequences that are derived from species compatible with a host cell are used in connection with these bacterial hosts. The vector carries a replication site, as well as specific genes which are capable of providing phenotypic selection in transformed cells. A number of approaches can be taken for evaluating the expression plasmids for the production of antibodies and antigen binding portions thereof in bacteria (see Glover, 1985; Ausubel, 1987, 1993; Sambrook, 1989; Colligan, 1992-1996).

[0269] Host mammalian cells can be grown in vitro or in vivo. Mammalian cells provide post- translational modifications to immunoglobulin molecules including leader peptide removal, folding and assembly of VH and VL chains, glycosylation of the antibody molecules, and secretion of functional antibody and / or antigen binding portions thereof.

[0270] Mammalian cells which can be useful as hosts for the production of antibody proteins, in addition to the cells of lymphoid origin described above, include cells of fibroblast origin, such as Vero or CHO-K1 cells. Exemplary eukaryotic cells that can be used to express immunoglobulin polypeptides include, but are not limited to, COS cells, including COS 7 cells; 293 cells, including 293-6E cells; CHO cells, including CHO-S and DG44 cells; PERC6™ cells (Crucell); and NSO cells. In some embodiments, a particular eukaryotic host cell is selected based on its ability to make desired post-translational modifications to the heavy chains and / or light chains. For example, in some embodiments, CHO cells produce polypeptides that have a higher level of sialylation than the same polypeptide produced in 293 cells.

[0271] In some embodiments, one or more antibodies or antigen-binding portions thereof can be produced in vivo in an animal that has been engineered or transfected with one or more nucleic acid molecules encoding the polypeptides, according to any suitable method.

[0272] In some embodiments, an antibody or antigen-binding portion thereof is produced in a cell- free system. Non-limiting exemplary cell-free systems are described, e.g., in Sitaraman et al., Methods Mol. Biol. 498: 229-44 (2009); Spirin, Trends Biotechnol. 22: 538-45 (2004); and Endo et al., Biotechnol. Adv. 21: 695-713 (2003).

[0273] Many vector systems are available for the expression of the VH and VL chains in mammalian cells (see Glover, 1985). Various approaches can be followed to obtain intact antibodies. As discussed above, it is possible to co-express VH and VL chains and optionally the associated constant regions in the same cells to achieve intracellular association and linkage of VH and VL chains into complete tetrameric H2L2 antibodies or antigen-binding portions thereof. The co­ expression can occur by using either the same or different plasmids in the same host. Nucleic acids 219 WO 2024 / 149345 PCT / CN2024 / 071901 encoding the VH and VL chains or antigen binding portions thereof can be placed into the same plasmid, which is then transfected into cells, thereby selecting directly for cells that express both chains. Alternatively, cells can be transfected first with a plasmid encoding one chain, for example the VL chain, followed by transfection of the resulting cell line with a VH chain plasmid containing a second selectable marker. Cell lines producing antibodies or antigen-binding portions thereof via either route could be transfected with plasmids encoding additional copies of peptides, VH, VL, or VH plus VL chains in conjunction with additional selectable markers to generate cell lines with enhanced properties, such as higher production of assembled antibodies or antigen binding portions thereof or enhanced stability of the transfected cell lines.

[0274] Additionally, plants have emerged as a convenient, safe and economical alternative expression system for recombinant antibody production, which are based on large scale culture of microbes or animal cells. Antibodies or antigen binding portions thereof can be expressed in plant cell culture, or plants grown conventionally. The expression in plants may be systemic, limited to sub-cellular plastids, or limited to seeds (endosperms). See, e.g., U.S. Patent Pub. No. 2003 / 0167531; U.S. Pat. No. 6,080,560; U.S. Pat. No. 6,512,162; and WO 0129242. Several plant- derived antibodies have reached advanced stages of development, including clinical trials (see, e.g., Biolex, N.C.).

[0275] For intact antibodies, the variable regions (VH and VL regions) of antibodies are typically linked to at least a portion of an immunoglobulin constant region (Fc) or domain, typically that of a human immunoglobulin. Human constant region DNA sequences can be isolated in accordance with well-known procedures from a variety of human cells, such as immortalized B-cells (WO 87 / 02671). An antibody can contain both light chain and heavy chain constant regions. The heavy chain constant region can include CHI, hinge, CH2, CH3, and, optionally, CH4 regions. In some embodiments, the CH2 domain can be deleted or omitted.

[0276] Techniques described for the production of single chain antibodies (see, e.g. U.S. Pat. No. 4,946,778; Bird, Science 242:423-42 (1988); Huston et al., Proc. Natl. Acad. Sci. USA 85:5879-5883 (1988); and Ward et al., Nature 334:544-54 (1989); which are incorporated by reference herein in their entireties) can be adapted to produce single chain antibodies that specifically bind to the target antigen. Single chain antibodies are formed by linking the heavy and light chain variable regions of the Fv region via an amino acid bridge, resulting in a single chain polypeptide. Techniques for the assembly of functional Fv portions in E. coli can also be used (see, e.g. Skerra et al., Science 242:1038-1041 (1988); which is incorporated by reference herein in its entirety).

[0277] In some embodiments, an antigen binding portion comprises one or more scFvs. An scFv can be, for example, a fusion protein of the variable regions of the heavy (VH) and light chain (VL) variable regions of an antibody, connected with a short linker peptide of ten to about 25 amino acids. The linker is usually rich in glycine for flexibility, as well as serine or threonine for solubility, and can either connect the N-terminus of the VH with the C-terminus of the VL, or vice versa. This protein retains the specificity of the original antibody, despite removal of the constant regions and the introduction of the linker. scFv antibodies are, e.g. described in Houston, J. S., Methods in Enzymol. 203 (1991) 46-96. Methods for making scFv molecules and designing suitable peptide linkers are 220 WO 2024 / 149345 PCT / CN2024 / 071901 described in, for example, U.S. Pat. No. 4,704,692; U.S. Pat. No. 4,946,778; Raag and Whitlow, FASEB 9:73-80 (1995) and Bird and Walker, TIBTECH, 9: 132-137 (1991). scFv-Fcs have been described by Sokolowska-Wedzina et al., Mol. Cancer Res. 15(8):1040-1050, 2017.

[0278] In some embodiments, an antigen binding portion is a single-domain antibody is an antibody portion consisting of a single monomeric variable antibody domain. Single domains antibodies can be derived from the variable domain of the antibody heavy chain from camelids (e.g., nanobodies or VHH portions). Furthermore, a single-domain antibody can be an autonomous human heavy chain variable domain (aVH) or VNAR portions derived from sharks (see, e.g., Hasler et al., Mol. Immunol. 75:28-37, 2016).

[0279] Techniques for producing single domain antibodies (DABs or VHH) are known in the art, as disclosed for example in Cossins et al. (2006, Prot Express Purif 51:253-259) and Li et al. (Immunol. Lett. 188:89-95, 2017). Single domain antibodies may be obtained, for example, from camels, alpacas or llamas by standard immunization techniques. (See, e.g., Muyldermans et al., TIBS 26:230-235, 2001; Yau et al., J Immunol Methods 281:161-75, 2003; and Maass et al., J Immunol Methods 324:13-25, 2007.) A VHH may have potent antigen-binding capacity and can interact with epitopes that are inaccessible to conventional VH-VL pairs (see, e.g., Muyldermans et al., 2001). Alpaca serum IgG contains about 50% camelid heavy chain only IgG antibodies (HCAbs) (see, e.g., Maass et al., 2007). Alpacas may be immunized with antigens and VHHs can be isolated that bind to and neutralize the target antigen (see, e.g., Maass et al., 2007). PCR primers that amplify alpaca VHH coding sequences have been identified and can be used to construct alpaca VHH phage display libraries, which can be used for antibody fragment isolation by standard biopanning techniques well known in the art (see, e.g., Maass et al., 2007).

[0280] Techniques for making multispecific antibodies include, but are not limited to, recombinant co-expression of two immunoglobulin heavy chain-light chain pairs having different specificities (see, e.g., Milstein and Cuello, Nature 305: 537 (1983)), WO 93 / 08829, and Traunecker et al., EMBO J. 10: 3655 (1991)), and "knob-in-hole" engineering (see, e.g., U.S. Pat. No. 5,731,168; Carter (2001), J Immunol Methods 248, 7-15). Multi-specific antibodies may also be made by engineering electrostatic steering effects for making antibody Fc-heterodimeric molecules (see, e.g., WO 2009 / 089004A1); cross-linking of two or more antibodies or antigen binding portions thereof (see, e.g., U.S. Pat. No. 4,676,980, and Brennan et al., Science, 229: 81 (1985)); using leucine zippers to produce bi-specific antibodies (see, e.g., Kostelny et al., J. Immunol., 148(5):1547-1553 (1992)); using "diabody" technology for making bispecific antibody portions (see, e.g., Hollinger et al., Proc. Natl. Acad. Sci. USA, 90:6444-6448 (1993)); and using single-chain Fv (scFv) dimers (see, e.g. Gruber et al., J. Immunol., 152:5368 (1994)); and preparing trispecific antibodies as described, e.g., in Tutt et al. J. Immunol. 147: 60 (1991).

[0281] Engineered antibodies with three or more functional antigen binding sites, including "Octopus antibodies," also can be Targeting groups (see, e.g. US 2006 / 0025576A1).

[0282] In some embodiments, the Targeting groups comprise different antigen-binding sites, fused to one or the other of the two subunits of the Fc domain; thus, the two subunits of the Fc domain may be comprised in two non-identical polypeptide chains. Recombinant co-expression of these 221 WO 2024 / 149345 PCT / CN2024 / 071901 polypeptides and subsequent dimerization leads to several possible combinations of the two polypeptides. To improve the yield and purity of the bispecific molecules in recombinant production, it will thus be advantageous to introduce in the Fc domain of the Targeting group a modification promoting the association of the desired polypeptides.

[0283] Generally, this method involves replacement of one or more amino acid residues at the interface of the two Fc domains by charged amino acid residues so that homodimer formation becomes electrostatically unfavorable but heterodimerization electrostatically favorable.

[0284] In some embodiments, a Targeting group is a "bispecific T cell engager" or BiTE (see, e.g., WO2004 / 106381, WO2005 / 061547, WO2007 / 042261, and WO2008 / 119567). This approach utilizes two antibody variable domains arranged on a single polypeptide. For example, a single polypeptide chain can include two single chain Fv (scFv) portions, each having a variable heavy chain (VH) and a variable light chain (VL) domain separated by a polypeptide linker of a length sufficient to allow intramolecular association between the two domains. This single polypeptide further includes a polypeptide spacer sequence between the two scFvs. Each scFv recognizes a different epitope, and these epitopes may be specific for different proteins, such that both proteins are bound by the BiTE.

[0285] As it is a single polypeptide, the bispecific T cell engager may be expressed using any prokaryotic or eukaryotic cell expression system known in the art, e.g., a CHO cell line. However, specific purification techniques (see, e.g., EP1691833) may be necessary to separate monomeric bispecific T cell engagers from other multimeric species, which may have biological activities other than the intended activity of the monomer. In one exemplary purification scheme, a solution containing secreted polypeptides is first subjected to a metal affinity chromatography, and polypeptides are eluted with a gradient of imidazole concentrations. This eluate is further purified using anion exchange chromatography, and polypeptides are eluted using with a gradient of sodium chloride concentrations. Finally, this eluate is subjected to size exclusion chromatography to separate monomers from multimeric species. In some embodiments, a Targeting group is a bispecific antibody is composed of a single polypeptide chain comprising two single chain FV portions (scFV) fused to each other by a peptide linker.

[0286] In some embodiments, a Targeting group is multispecific, such as an IgG-scFV. IgG-scFv formats include lgG(H)-scFv, scFv-(H)lgG, lgG(L)-scFv, svFc-(L)lgG, 2scFV-lgG and lgG-2scFv. These and other bispecific antibody formats and methods of making them have been described in for example, Brinkmann and Kontermann, MAbs 9(2):182-212 (2017); Wang et al., Antibodies, 2019, 8, 43; Dong et al., 2011, MAbs 3:273-88; Natsume et al., J. Biochem. 140(3):359-368, 2006; Cheal et al., Mol. Cancer Ther. 13(7):1803-1812, 2014; and Bates and Power, Antibodies, 2019, 8, 28.

[0287] Igg-like dual-variable domain antibodies (DVD-lg) have been described by Wu et al., 2007, Nat Biotechnol 25:1290-97; Hasler et al., Mol. Immunol. 75:28-37, 2016 and in WO 08 / 024188 and WO 07 / 024715. Triomabs have been described by Chelius et al., MAbs 2(3):309-319, 2010. 2-in-l- IgGs have been described by Kontermann et al., Drug Discovery Today 20(7):838-847, 2015. Tanden antibody or TandAb have been described by Kontermann et al., id. ScFv-HSA-scFv antibodies have also been described by Kontermann et al. (id.).

[0288] Intact (e.g., whole) antibodies, their dimers, individual light and heavy chains, or antigen 222 WO 2024 / 149345 PCT / CN2024 / 071901 binding portions thereof can be recovered and purified by known techniques, e.g., immunoadsorption or immunoaffinity chromatography, chromatographic methods such as HPLC (high performance liquid chromatography), ammonium sulfate precipitation, gel electrophoresis, or any combination of these. See generally, Scopes, Protein Purification (Springer-Verlag, N.Y., 1982). Substantially pure antibodies or antigen binding portions thereof of at least about 90% to 95% homogeneity are advantageous, as are those with 98% to 99% or more homogeneity, particularly for pharmaceutical uses. Once purified, partially or to homogeneity as desired, an intact antibody or antigen binding portions thereof can then be used therapeutically or in developing and performing assay procedures, immunofluorescent staining, and the like. See generally, Vols. I & II Immunol. Meth. (Lefkovits & Pernis, eds., Acad. Press, NY, 1979 and 1981). Conjugates

[0289] In some embodiments, provided are Conjugates comprising a Targeting group as described herein attached to a Drug-Linker as described herein. In some embodiments, provided are Conjugates comprising a Targeting group as described herein attached to a Drug-Linker as described herein (e.g., Formula (A). For example, in some embodiments the Targeting group is selected from an antibody or an antigen-binding portion thereof. In more specific embodiments, the Targeting group is a monoclonal antibody, a Fab, a Fab’, an F(ab’), an Fv, a disulfide linked Fc, a scFv, a single domain antibody, a diabody, a bi-specific antibody, or a multi-specific antibody. In more specific embodiments, the Targeting group is a diabody, a DART, an anticalin, an affibody, an avimer, a DARPin, or an adnectin. In some embodiments, the Targeting group is mono-specific. In some embodiments, the Targeting group is bivalent. In some embodiments, the Targeting group is bispecific.

[0290] In some embodiments, provided are conjugates comprising a Targeting group attached to a Drug-Linker as described above, wherein the average drug loading (pload) of the conjugate is from about 1 to about 8, about 2, about 4, about 6, about 8, about 10, about 12, about 14, about 16, about 3 to about 5, about 6 to about 8, or about 8 to about 16. In some cases, the pload is about 1. In some cases, the pload is about 2. In some cases, the pload is about 4. In some cases, the pload is about 8.

[0291] In some embodiments, provided a Conjugates selected from the following: 223 WO 2024 / 149345 PCT / CN2024 / 071901 224 WO 2024 / 149345 PCT / CN2024 / 071901 225 WO 2024 / 149345 PCT / CN2024 / 071901 226 WO 2024 / 149345 PCT / CN2024 / 071901 227 WO 2024 / 149345 PCT / CN2024 / 071901 228 WO 2024 / 149345 PCT / CN2024 / 071901 229 WO 2024 / 149345 PCT / CN2024 / 071901 230 WO 2024 / 149345 PCT / CN2024 / 071901 231 WO 2024 / 149345 PCT / CN2024 / 071901 232 WO 2024 / 149345 PCT / CN2024 / 071901 233 WO 2024 / 149345 PCT / CN2024 / 071901 234 WO 2024 / 149345 PCT / CN2024 / 071901 235 WO 2024 / 149345 PCT / CN2024 / 071901 236 WO 2024 / 149345 PCT / CN2024 / 071901 237 WO 2024 / 149345 PCT / CN2024 / 071901 238 WO 2024 / 149345 PCT / CN2024 / 071901 239 WO 2024 / 149345 PCT / CN2024 / 071901 240 WO 2024 / 149345 PCT / CN2024 / 071901 241 WO 2024 / 149345 PCT / CN2024 / 071901 242 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH 243 WO 2024 / 149345 PCT / CN2024 / 071901 244 WO 2024 / 149345 PCT / CN2024 / 071901 245 WO 2024 / 149345 PCT / CN2024 / 071901 wherein Ab is a Targeting group and n is pload.

[0292] In some embodiments, the conjugate is a stereoisomer of one of the above structures.

[0293] In some embodiments, provided are conjugates described above wherein the Targeting group specifically binds to a target molecule. In more specific embodiments, the target molecule is CD19, CD20, CD30, CD33, CD70, LIV-1 or EGFRv3. In more specific embodiments, the target molecule is CD19, CD20, CD30, CD33, CD70, LIV-1 EGFRv3, or HER2. For example, in some embodiments the Targeting group is selected from: a scFvl-ScFv2, a ScFvl2-Fc-scFv22, an IgG- scFv, a DVD-lg, a triomab / quadroma, a two-in-one IgG, a scFv2-Fc, a TandAb, and an scFv-HSA- scFv.

[0294] In other embodiments, provided are conjugates described above wherein the target molecule is a cancer associated antigen. For example, in some embodiments the target molecule is CD19, CD20, CD30, CD33, CD38, CA125, HER2, MUC-1, prostate-specific membrane antigen (PSMA), CD44 surface adhesion molecule, mesothelin (MLSN), carcinoembryonic antigen (CEA), epidermal growth factor receptor (EGER), EGFRvlll, vascular endothelial growth factor receptor-2 (VEGFR2), high molecular weight-melanoma associated antigen (HMW-MAA), MAGE-Al, IL-13R-a2, GD2, lpl9q, ABL1, AKT1, ALK, APC, AR, ATM, BRAF, BRCA1, BRCA2, cKIT, cMET, CSF1R, CTNNB1, FGFR1, FGFR2, FLT3, GNA11, GNAQ, GNAS, HRAS, IDH1, IDH2, JAK2, KDR (VEGFR2), KRAS, MGMT, MGMT-Me, MLH1, MPL, NOTCH1, NRAS, PDGFRA, Pgp, PIK3CA, PR, PTEN, RET, RRM1, SMO, SPARC, TLE3, TOP2A, TOPO1, TP53, TS, TUBB3, VHL, CDH1, ERBB4, FBXW7, HNF1A, JAK3, NPM1, PTPN11, RBI, SMAD4, SMARCB1, STK1, MLH1, MSH2, MSH6, PMS2, ROS1, ERCC1, 5T4 (TPBG), B7-H3, CCR7, CD105, CD22, CD46, CD47, CD56, CD70, CD71, CD79b, CDH6, CLDN6, CLDN18.2, CLEC12A, DLL3, DR5, ERBB3 (HER3), EPCAM, FOLRI, IGF1R, IL2RA (CD25), IL3RA, ITGB6, LIV-1, LRRC15, mesothelin (MSLN), NaPi2b (SLC34A2), nectin-4, PTK7, ROR1, SEZ6, SLC44A4, SLITRK6, Tissue Factor (TF), TROP2 or B7-H4.

[0295] In other embodiments, provided are conjugates described above wherein the Targeting group is an antibody, or fragment thereof, comprising rituximab (Rituxan®), trastuzumab (Herceptin®), pertuzumab (Perjeta®)), bevacizumab (Avastin®), ranibizumab (Lucentis®), cetuximab (Erbitux®), alemtuzumab (Campath®), panitumumab (Vectibix®), ibritumomab tiuxetan (Zevalin®), tositumomab (Bexxar®), ipilimumab, zalutumumab, dalotuzumab, figitumumab, ramucirumab, galiximab, farletuzumab, ocrelizumab, ofatumumab (Arzerra®), tositumumab, ibritumomab, the CD20 antibodies 2F2 (HuMax-CD20), 7D8, lgM2C6, IgGl 2C6, 11B8, Bl, 2H7, 246 WO 2024 / 149345 PCT / CN2024 / 071901 LT20,1FS or AT80, daclizumab (Zenapax®), or anti-LHRH receptor antibodies including clone A9E4, F1G4, AT2G7, GNRH03, or GNRHR2. Drug Loading

[0296] Conjugates can contain one or more Drug unit per Targeting group. The number of Drug units per Targeting group is referred to as drug loading. The drug loading of a Conjugate is represented by pload, the average number of Drug units (drug molecules (e.g., cytotoxic agents)) per Targeting groups (e.g., an antibody or antigen binding portion or non-antibody scaffold or non­ antibody protein) in a conjugate. For example, if pload is about 4, the average drug loading taking into account all of the Targeting groups (e.g., antibodies or antigen binding portion or non-antibody scaffold or non-antibody proteins) present in the composition is about 4. In some embodiments, pload ranges from about 3 to about 5, from about 3.6 to about 4.4, or from about 3.8 to about 4.2. In some embodiments, pload can be about 3, about 4, or about 5. In some embodiments, pload ranges from about 6 to about 8, more preferably from about 7.5 to about 8.4. In some embodiments, pload can be about 6, about 7, or about 8. In some embodiments, pload ranges from about 8 to about 16.

[0297] The average number of Drug units per Targeting group (e.g., antibody or antigen binding portion or non-antibody scaffold) in a preparation may be characterized by conventional means such as UV, mass spectroscopy, Capillary Electrophoresis (CE), and HPLC. The quantitative distribution of conjugates in terms of pload may also be determined. In some instances, separation, purification, and characterization of homogeneous conjugates where pload is a certain value from conjugates with other drug loadings may be achieved by means such as reverse phase HPLC or Hydrophobic Interaction Chromatography (HIC) HPLC. Attachment of Drug-Linkers to Antibodies, Antigen Binding Portions and Other Binding Agents (including Non-Antibody Scaffolds)

[0298] Techniques for attaching Drug unit(s) to Targeting groups (such as antibodies or antigen binding portions thereof or non-antibody scaffolds) via linkers are well-known in the art. See, e.g., Alley et al., Current Opinion in Chemical Biology 2010 14:1-9; Senter, Cancer J., 2008, 14(3):154- 169. In some embodiments, a Linker is first attached to a Drug unit (e.g., a cytotoxic agent(s), immune modulatory agent or other agent) and then the Drug-Linker(s) is attached to the Targeting group (e.g., an antibody or antigen binding portion thereof or non-antibody protein scaffold). In some embodiments, a Linker(s) is first attached to a Targeting group (e.g., an antibody or antigen binding portion thereof or non-antibody protein scaffold), and then a Drug unit is attached to a Linker. In the following discussion, the term Drug-Linker is used to exemplify attachment of Linkers or Drug- Linkers to Targeting groups; the skilled artisan will appreciate that the selected attachment method can be determined according to Linker and the Drug unit. In some embodiments, a Drug unit is attached to a Targeting group via a Linker in a manner that reduces the activity of the Drug unit until it is released from the conjugate (e.g., by hydrolysis, by proteolytic degradation or by a cleaving agent.).

[0299] Generally, a conjugate may be prepared by several routes employing organic chemistry reactions, conditions, and reagents known to those skilled in the art, including: (1) reaction of a nucleophilic group of a Targeting group (e.g., an antibody or antigen binding portion thereof or non- 247 WO 2024 / 149345 PCT / CN2024 / 071901 antibody protein scaffold) with a bivalent Linker to form a Targeting group-Linker intermediate via a covalent bond, followed by reaction with a Drug unit; and (2) reaction of a nucleophilic group of a Drug unit with a bivalent Linker, to form Drug-Linker, via a covalent bond, followed by reaction with a nucleophilic group of a Targeting group. Exemplary methods for preparing conjugates via the latter route are described in US Patent No. 7,498,298, which is expressly incorporated herein by reference.

[0300] Nucleophilic groups on Targeting groups such as antibodies, antigen binding portions and other binding agents (including non-antibody scaffolds) include, but are not limited to: (i) N-terminal amine groups, (ii) side chain amine groups, e.g. lysine, (iii) side chain thiol groups, e.g. cysteine, and (iv) sugar hydroxyl or amino groups where the antibody is glycosylated. Amine, thiol, and hydroxyl groups are nucleophilic and capable of reacting to form covalent bonds with electrophilic groups on Linkers including: (i) active esters such as NHS esters, HOBt esters, haloformates, and acid halides; (ii) alkyl and benzyl halides such as haloacetamides; and (iii) aldehydes, ketones, carboxyl, and maleimide groups. Certain Targeting groups, such as antibodies (and antigen binding portions and other binding agents (including non-antibody scaffolds)) have reducible interchain disulfides, i.e., cysteine bridges. Antibodies (and antigen binding portions and other binding agents (including non­ antibody scaffolds)) may be made reactive for conjugation with Linkers by treatment with a reducing agent such as DTT (dithiothreitol) or tricarbonylethylphosphine (TCEP), such that the antibody is fully or partially reduced. Each cysteine bridge will thus form, theoretically, two reactive thiol nucleophiles. Additional nucleophilic groups can be introduced into Targeting groups such as antibodies (and antigen binding portions and other binding agents (including non-antibody scaffolds)) through modification of lysine residues, e.g., by reacting lysine residues with 2-iminothiolane (Traut's reagent), resulting in conversion of an amine into a thiol. Reactive thiol groups may also be introduced into a Targeting group (such as an antibody and antigen binding portions and other binding agents (including non-antibody scaffolds)) by introducing one, two, three, four, or more cysteine residues (e.g., by preparing antibodies, antigen binding portions and other binding agents (including non-antibody scaffolds) comprising one or more non-native cysteine amino acid residues).

[0301] Conjugates may also be produced by reaction between an electrophilic group on a Targeting group, such as an aldehyde or ketone carbonyl group, with a nucleophilic group on a Linker reagent. Useful nucleophilic groups on a linker reagent include, but are not limited to, hydrazide, oxime, amino, hydrazine, thiosemicarbazone, hydrazine carboxyl, and arylhydrazide. In an embodiment, an antibody (or antigen binding portion thereof or other binding agent (including non-antibody scaffolds)) is modified to introduce electrophilic moieties that are capable of reacting with nucleophilic substituents on a Linker. In another embodiment, the sugars of glycosylated antibodies may be oxidized, e.g. with periodate oxidizing reagents, to form aldehyde or ketone groups which may react with the amine group of a Linker. The resulting imine Schiff base groups may form a stable linkage, or may be reduced, e.g., by borohydride reagents to form stable amine linkages. In one embodiment, reaction of the carbohydrate portion of a glycosylated antibody with either galactose oxidase or sodium meta-periodate may yield carbonyl (aldehyde and ketone) groups in the antibody (or antigen binding portion thereof or other binding agent (including non-antibody 248 WO 2024 / 149345 PCT / CN2024 / 071901 scaffolds)) that can react with appropriate groups on the Linker (see, e.g., Hermanson, Bioconjugate Techniques). In another embodiment, Targeting groups such as antibodies containing N-terminal serine or threonine residues can react with sodium meta-periodate, resulting in production of an aldehyde in place of the first amino acid (Geoghegan & Stroh, (1992) Bioconjugate Chern. 3:138- 146; US 5362852). Such an aldehyde can be reacted with a Linker.

[0302] Exemplary nucleophilic groups on a Drug unit, such as a cytotoxic agent, include, but are not limited to: amine, thiol, hydroxyl, hydrazide, oxime, hydrazine, thiosemicarbazone, hydrazine carboxyl, and arylhydrazide groups capable of reacting to form covalent bonds with electrophilic groups on a Linker(s) including: (i) active esters such as NHS esters, HOBt esters, haloformates, and acid halides; (ii) alkyl and benzyl halides such as haloacetamides; (iii) aldehydes, ketones, carboxyl, and maleimide groups.

[0303] In some embodiments, a Drug-Linker is attached to an interchain cysteine residue(s) of an antibody (or antigen binding portion thereof or other binding agent (including non-antibody scaffolds)). See, e.g., WO2004 / 010957 and WO2005 / 081711. In such embodiments, the Linker typically comprises a maleimide group for attachment to the cysteine residues of an interchain disulfide. In some embodiments, a Linker or Drug-Linker is attached to a cysteine residue(s) of an antibody or antigen binding portion thereof as described in US Patent Nos. 7,585,491 or 8,080m250. The drug loading of the resulting conjugate typically ranges from 1 to 8 or 1 to 16.

[0304] In some embodiments, a Linker or Drug-Linker is attached to a lysine or cysteine residue(s) of an antibody (or antigen binding portion thereof or other binding agent) as described in WO2005 / 037992 or WO2010 / 141566. The drug loading of the resulting conjugate typically ranges from 1 to 8.

[0305] In some embodiments, engineered cysteine residues, poly-histidine sequences, glycoengineering tags, or transglutaminase recognition sequences can be used for site-specific attachment of linkers or drug-linkers to antibodies or antigen binding portions thereof or other binding agents (including non-antibody scaffolds).

[0306] In some embodiments, a Drug-Linker(s) is attached to an engineered cysteine residue at an Fc residue other than an interchain disulfide. In some embodiments, a Drug-Linker(s) is attached to an engineered cysteine introduced into an IgG (typically an IgGl) at position 118, 221, 224, 227, 228, 230, 231, 223, 233, 234, 235, 236, 237, 238, 239, 240, 241, 243, 244, 245, 247, 249, 250, 258, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 275, 276, 278, 280, 281, 283, 285, 286, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 302, 305, 313, 318, 323, 324, 325, 327, 328, 329, 330, 331, 332, 333, 335, 336, 396, and / or 428, of the heavy chain and / or to a light chain at position 106, 108, 142 (light chain), 149 (light chain), and / or position V205, according to the EU numbering of Kabat. An exemplary substitution for site specific conjugation using an engineered cysteine is S239C (see, e.g., US 20100158909; numbering of the Fc region is according to the EU index).

[0307] In some embodiments, a Linker or Drug-Linker(s) is attached to one or more introduced cysteine residues of an antibody (or antigen binding portion thereof or other binding agent (including non-antibody scaffolds)) as described in WO2006 / 034488, WO2011 / 156328 and / or WO2016040856. 249 WO 2024 / 149345 PCT / CN2024 / 071901

[0308] In some embodiments, an exemplary substitution for site specific conjugation using bacterial transglutaminase is N297S or N297Q of the Fc region. In some embodiments, a Linker or Drug- Linker(s) is attached to the glycan or modified glycan of an antibody or antigen binding portion or a glycoengineered antibody (or other binding agent (including non-antibody scaffolds)). See, e.g., WO2017 / 147542, WO2020 / 123425, WO2020 / 245229, WO2014 / 072482; WO2014 / / 065661, WO2015 / 057066 and WO2016 / 022027; the disclosure of which are incorporated by reference herein.

[0309] In some embodiments, a Linker or Drug-Linker is attached to an antibody, antigen binding portion or other binding agent (including non-antibody scaffolds) via Sortase A linker. A Sortase A linker can be created by a Sortase A enzyme fusing an LPXTG recognition motif (SEQ ID NO: 5) to an N-terminal GGG motif to regenerate a native amide bond.

[0310] In some embodiments, a Linker or Drug-Linker is attached to an antibody, antigen binding portion or other binding agent (including non-antibody scaffolds) using SMARTag Technology, in which a bioorthogonal aldehyde handle is introduced through the oxidation of a cysteine residue, embedded in a specific peptide sequence (CxPxR), to an aldehyde-bearing formylglycine (fGly). This enzymatic modification is carried out by the formylglycine-generating enzyme (FGE). See, e.g., Liu et aL, Methods Mol. Biol. 2033:131-147 (2019).

[0311] In some embodiments, a Linker or Drug-Linker is attached to an antibody, antigen binding portion or other binding agent (including non-antibody scaffolds) using cysteine conjugation with quaternized vinyl- and alkynyl-pyridine reagents. See, e.g., Matos et al., Angew Chem. Int. Ed. Engl. 58:6640-6644 (2019).

[0312] In other embodiments, a Linker or Drug-Linker is attached to an antibody, antigen binding portion or other binding agent (including non-antibody scaffolds) using bis-maleimide, C-lock, or K- lock methodologies. PHARMACEUTICAL COMPOSITIONS

[0313] Other aspects of the conjugates relate to compositions comprising active ingredients, including any of the conjugates described herein. In some embodiments, the composition is a pharmaceutical composition. As used herein, the term "pharmaceutical composition" refers to an active agent in combination with a pharmaceutically acceptable carrier accepted for use in the pharmaceutical industry. 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.

[0314] The preparation of a pharmacological composition that contains active ingredients dissolved or dispersed therein is well understood in the art and need not be limited based on any particular formulation. Typically, such compositions are prepared as injectable either as liquid solutions or suspensions; however, solid forms suitable for rehydration, or suspensions, in liquid prior to use can also be prepared. A preparation can also be emulsified or presented as a liposome composition. A conjugate can be mixed with excipients that are pharmaceutically acceptable and compatible with 250 WO 2024 / 149345 PCT / CN2024 / 071901 the active ingredient and in amounts suitable for use in the therapeutic methods described herein. Suitable excipients are, for example, water, saline, dextrose, glycerol, ethanol or the like and combinations thereof. In addition, if desired, a pharmaceutical composition can contain minor amounts of auxiliary substances such as wetting or emulsifying agents, pH buffering agents and the like which enhance or maintain the effectiveness of the active ingredient (e.g., a conjugate).

[0315] The pharmaceutical compositions as described herein can include pharmaceutically acceptable salts of the components therein. Pharmaceutically acceptable salts include the acid addition salts (formed with the free amino groups of a polypeptide) that are formed with inorganic acids such as, for example, hydrochloric or phosphoric acids, or such organic acids as acetic, tartaric, mandelic and the like. Salts formed with the free carboxyl groups can also be derived from inorganic bases such as, for example, sodium, potassium, ammonium, calcium or ferric hydroxides, and such organic bases as isopropylamine, trimethylamine, 2-ethylamino ethanol, histidine, procaine and the like.

[0316] Physiologically tolerable carriers are well known in the art. Exemplary liquid carriers are sterile aqueous solutions that contain the active ingredients (e.g., a conjugate) and water, and may contain a buffer such as sodium phosphate at physiological pH value, physiological saline or both, such as phosphate-buffered saline. Still further, aqueous carriers can contain more than one buffer salt, as well as salts such as sodium and potassium chlorides, dextrose, polyethylene glycol and other solutes. Liquid compositions can also contain liquid phases in addition to and to the exclusion of water. Exemplary of such additional liquid phases are glycerin, vegetable oils such as cottonseed oil, and water-oil emulsions. The amount of an active agent that will be effective in the treatment of a particular disorder or condition will depend on the nature of the disorder or condition, and can be determined by standard clinical techniques.

[0317] In some embodiments, a pharmaceutical composition comprising a conjugate can be a lyophilisate.

[0318] In some embodiments, a syringe comprising a therapeutically effective amount of a conjugate is provided. TREATMENT METHODS

[0319] In some embodiments, provided are methods of treating a subject, comprising administering to the subject a conjugate described herein or a pharmaceutical composition described herein. For example, in some embodiments the subject has cancer or an autoimmune disease and the conjugate binds to the target antigen associated with the cancer or autoimmune disease.

[0320] In some embodiments, provided are methods of treating cancer comprising administering a conjugate. In some embodiments, the subject is in need of treatment for a cancer and / or a malignancy. In some embodiments, the method is for treating a subject having a cancer or malignancy.

[0321] The methods described herein include administering a therapeutically effective amount of a conjugate to a subject having a cancer or malignancy. As used herein, the phrases "therapeutically effective amount," "effective amount," or "effective dose" refer to an amount of a conjugate that provides a therapeutic benefit in the treatment of, management of or prevention of relapse of a 251 WO 2024 / 149345 PCT / CN2024 / 071901 cancer or malignancy, e.g., an amount that provides a statistically significant decrease in at least one symptom, sign, or marker of a tumor or malignancy. Determination of a therapeutically effective amount is well within the capability of those skilled in the art. Generally, a therapeutically effective amount can vary with the subject's history, age, condition, sex, as well as the severity and type of the medical condition in the subject, and administration of other pharmaceutically active agents.

[0322] The terms "cancer" and "malignancy” refer to an uncontrolled growth of cells which interferes with the normal functioning of the bodily organs and systems. A cancer or malignancy may be primary or metastatic, i.e. that is it has become invasive, seeding tumor growth in tissues remote from the original tumor site. A “tumor” refers to an uncontrolled growth of cells which interferes with the normal functioning of the bodily organs and systems. A subject that has a cancer is a subject having objectively measurable cancer cells present in the subject's body. Included in this definition are benign tumors and malignant cancers, as well as potentially dormant tumors and micro­ metastases. Cancers that migrate from their original location and seed other vital organs can eventually lead to the death of the subject through the functional deterioration of the affected organs. Hematologic malignancies (hematopoietic cancers), such as leukemias and lymphomas, are able to, for example, out-compete the normal hematopoietic compartments in a subject, thereby leading to hematopoietic failure (in the form of anemia, thrombocytopenia and neutropenia) ultimately causing death.

[0323] Examples of cancers include, but are not limited to, carcinomas, lymphomas, blastomas, sarcomas, and leukemias. More particular examples of such cancers include, but are not limited to, basal cell cancer, biliary tract cancer, bladder cancer, bone cancer, brain and CNS cancer, breast cancer (e.g., triple negative breast cancer), cancer of the peritoneum, cervical cancer; cholangiocarcinoma, choriocarcinoma, chondrosarcoma, colon and rectum cancer (colorectal cancer), connective tissue cancer, cancer of the digestive system, endometrial cancer, esophageal cancer, eye cancer, cancer of the head and neck, gastric cancer (including gastrointestinal cancer and stomach cancer), glioblastoma (GBM), hepatic cancer, hepatoma, intra-epithelial neoplasm, kidney or renal cancer (e.g., clear cell cancer), larynx cancer, leukemia, liver cancer, lung cancer (e.g., small-cell lung cancer, non-small cell lung cancer, adenocarcinoma of the lung, and squamous cancer of the lung), lymphoma including Hodgkin's and non-Hodgkin's lymphoma, melanoma, mesothelioma, myeloma, neuroblastoma, oral cavity cancer (e.g., lip, tongue, mouth, and pharynx), ovarian cancer, pancreatic cancer, prostate cancer, retinoblastoma, rhabdomyosarcoma, cancer of the respiratory system, salivary gland cancer, sarcoma, skin cancer, squamous cell cancer, testicular cancer, thyroid cancer, uterine or endometrial cancer, uterine serious cancer, cancer of the urinary system, vulval cancer; as well as other carcinomas and sarcomas, as well as B-cell lymphoma (including low grade / follicular non-Hodgkin's lymphoma (NHL), small lymphocytic (SL) NHL, intermediate grade / follicular NHL, intermediate grade diffuse NHL, high grade immunoblastic NHL, high grade lymphoblastic NHL, high grade small non-cleaved cell NHL, bulky disease NHL, mantle cell lymphoma, AIDS-related lymphoma, and Waldenstrom's Macroglobulinemia), chronic lymphocytic leukemia (CLL), acute lymphoblastic leukemia (ALL), Hairy cell leukemia, chronic myeloblastic leukemia, and post-transplant lymphoproliferative disorder (PTLD), as well as abnormal 252 WO 2024 / 149345 PCT / CN2024 / 071901 vascular proliferation associated with phakomatoses, edema (such as that associated with brain tumors), and Meigs' syndrome.

[0324] It is contemplated that the methods herein reduce tumor size or tumor burden in the subject, and / or reduce metastasis in the subject. In various embodiments, tumor size in the subject is decreased by about 25-50%, about 40-70% or about 50-90% or more. In various embodiments, the methods reduce the tumor size by 10%, 20%, 30% or more. In various embodiments, the methods reduce tumor size by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%.

[0325] As used herein, a "subject" refers to a human or animal. Usually, the animal is a vertebrate such as a primate, rodent, domestic animal or game animal. Primates include chimpanzees, cynomolgus monkeys, spider monkeys, and macaques, e.g., Rhesus. Rodents include mice, rats, woodchucks, ferrets, rabbits and hamsters. Domestic and game animals include cows, horses, pigs, deer, bison, buffalo, feline species, e.g., domestic cat, canine species, e.g., dog, fox, wolf, avian species, e.g., chicken, emu, ostrich, and fish, e.g., trout, catfish and salmon. In certain embodiments, the subject is a mammal, e.g., a primate, e.g., a human. The terms, "patient," "individual," and "subject" are used interchangeably herein.

[0326] Preferably, the subject is a mammal. The mammal can be a human, non-human primate, mouse, rat, dog, cat, horse, or cow, but are not limited to these examples. Mammals other than humans can be advantageously used, for example, as subjects that represent animal models of, for example, various cancers. In addition, the methods described herein can be used to treat domesticated animals and / or pets. A subject can be male or female. In certain embodiments, the subject is a human.

[0327] In some embodiments, a subject can be one who has been previously diagnosed with or identified as suffering from a cancer and in need of treatment, but need not have already undergone treatment for the cancer. In some embodiments, a subject can also be one who has not been previously diagnosed as having a cancer in need of treatment. In some embodiments, a subject can be one who exhibits one or more risk factors for a condition or one or more complications related to a cancer or a subject who does not exhibit risk factors. A "subject in need" of treatment for a cancer particular can be a subject having that condition or diagnosed as having that condition. In other embodiments, a subject “at risk of developing” a condition refers to a subject diagnosed as being at risk for developing the condition or at risk for having the condition again.

[0328] As used herein, the terms "treat," "treatment," "treating," or "amelioration" when used in reference to a disease, disorder or medical condition, refer to therapeutic treatments for a condition, wherein the object is to reverse, alleviate, ameliorate, inhibit, slow down or stop the progression or severity of a symptom or condition. The term "treating" includes reducing or alleviating at least one adverse effect or symptom of a condition. Treatment is generally "effective" if one or more symptoms or clinical markers are reduced. Alternatively, treatment is "effective" if the progression of a condition is reduced or halted. That is, "treatment" includes not just the improvement of symptoms or markers, but also a cessation or at least slowing of progress or worsening of symptoms that would be expected in the absence of treatment. Beneficial or desired clinical results include, but are not limited 253 WO 2024 / 149345 PCT / CN2024 / 071901 to, reduction in cancer cells in the subject, alleviation of one or more symptom(s), diminishment of extent of the deficit, stabilized (i.e., not worsening) state of a cancer or malignancy, delay or slowing of tumor growth and / or metastasis, and an increased lifespan as compared to that expected in the absence of treatment. As used herein, the term "administering," refers to providing a conjugate as described herein to a subject by a method or route which results in binding of the conjugate to cancer cells or malignant cells. Similarly, a pharmaceutical composition comprising a conjugate as described herein can be administered by any appropriate route which results in an effective treatment in the subject.

[0329] The dosage ranges for a conjugate depend upon the potency, and encompass amounts large enough to produce the desired effect e.g., slowing of tumor growth or a reduction in tumor size. The dosage should not be so large as to cause unacceptable adverse side effects. Generally, the dosage will vary with the age, condition, and sex of the subject and can be determined by one of skill in the art. The dosage can also be adjusted by the individual physician in the event of any complication. In some embodiments, the dosage ranges from 0.1 mg / kg body weight to 10 mg / kg body weight. In some embodiments, the dosage ranges from 0.5 mg / kg body weight to 15 mg / kg body weight. In some embodiments, the dose range is from 0.5 mg / kg body weight to 5 mg / kg body weight. Alternatively, the dose range can be titrated to maintain serum levels between 1 ug / mL and 1000 ug / mL. For systemic administration, subjects can be administered a therapeutic amount, such as, e.g. 0.1 mg / kg, 0.5 mg / kg, 1.0 mg / kg, 2.0 mg / kg, 2.5 mg / kg, 5 mg / kg, 10 mg / kg, 12 mg / kg or more.

[0330] Administration of the doses recited above can be repeated. In a preferred embodiment, the doses recited above are administered weekly, biweekly, every three weeks or monthly for several weeks or months. The duration of treatment depends upon the subject's clinical progress and responsiveness to treatment.

[0331] In some embodiments, a dose can be from about 0.1 mg / kg to about 100 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 25 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 20 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 15 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 12 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 100 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 25 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 20 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 15 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 12 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 10 mg / kg.

[0332] In some embodiments, a dose can be administered intravenously. In some embodiments, an intravenous administration can be an infusion occurring over a period of from about 10 minutes to about 4 hours. In some embodiments, an intravenous administration can be an infusion occurring over a period of from about 30 minutes to about 90 minutes.

[0333] In some embodiments, a dose can be administered weekly. In some embodiments, a dose can be administered bi-weekly. In some embodiments, a dose can be administered about every 2 weeks. In some embodiments, a dose can be administered about every 3 weeks. In some 254 WO 2024 / 149345 PCT / CN2024 / 071901 embodiments, a dose can be administered every four weeks.

[0334] In some embodiments, a total of from about 2 to about 10 doses are administered to a subject. In some embodiments, a total of 4 doses are administered. In some embodiments, a total of 5 doses are administered. In some embodiments, a total of 6 doses are administered. In some embodiments, a total of 7 doses are administered. In some embodiments, a total of 8 doses are administered. In some embodiments, a total of 9 doses are administered. In some embodiments, a total of 10 doses are administered. In some embodiments, a total of more than 10 doses are administered.

[0335] Pharmaceutical compositions containing a conjugate can be administered in a unit dose. The term "unit dose" when used in reference to a pharmaceutical composition refers to physically discrete units suitable as unitary dosage for the subject, each unit containing a predetermined quantity of active material (e.g., conjugate), calculated to produce the desired therapeutic effect in association with the required physiologically acceptable diluent, i.e., carrier, or vehicle.

[0336] In some embodiments, the conjugates as described herein can be used in a method(s) comprising administering a conjugate to a subject in need thereof, such as a subject having an autoimmune disease.

[0337] In some embodiments, provided are methods of treating an autoimmune disease comprising administering a conjugate as described herein. In some embodiments, the subject is in need of treatment for an autoimmune disease. The methods described herein include administering a therapeutically effective amount of a conjugate to a subject having an autoimmune disease. As used herein, the phrase "therapeutically effective amount," "effective amount," or "effective dose" refers to an amount of a conjugate as described herein that provides a therapeutic benefit in the treatment of, management of or prevention of relapse of an autoimmune disease, e.g., an amount that provides a statistically significant decrease in at least one symptom, sign, or marker of an autoimmune disease. Determination of a therapeutically effective amount is well within the capability of those skilled in the art. Generally, a therapeutically effective amount can vary with the subject's history, age, condition, sex, as well as the severity and type of the medical condition in the subject, and administration of other pharmaceutically active agents.

[0338] The term "autoimmune disease” refers to an immunological disorder characterized by inappropriate activation of immune cells (e.g., lymphocytes or dendritic cells), that interferes with the normal functioning of the bodily organs and systems. Examples of autoimmune disease include, but are not limited to, rheumatoid arthritis, psoriatic arthritis, autoimmune demyelinative diseases (e.g., multiple sclerosis, allergic encephalomyelitis), endocrine ophthalmopathy, uveoretinitis, systemic lupus erythematosus, myasthenia gravis, Grave's disease, glomerulonephritis, autoimmune hepatological disorder, inflammatory bowel disease (e.g., Crohn's disease), anaphylaxis, allergic reaction, Sjogren's syndrome, type I diabetes mellitus, primary biliary cirrhosis, Wegener's granulomatosis, fibromyalgia, polymyositis, dermatomyositis, multiple endocrine failure, Schmidt's syndrome, autoimmune uveitis, Addison's disease, adrenalitis, thyroiditis, Hashimoto's thyroiditis, autoimmune thyroid disease, pernicious anemia, gastric atrophy, chronic hepatitis, lupoid hepatitis, atherosclerosis, subacute cutaneous lupus erythematosus, 255 WO 2024 / 149345 PCT / CN2024 / 071901 hypoparathyroidism, Dressier's syndrome, autoimmune thrombocytopenia, idiopathic thrombocytopenic purpura, hemolytic anemia, pemphigus vulgaris, pemphigus, dermatitis herpetiformis, alopecia areata, pemphigoid, scleroderma, progressive systemic sclerosis, CREST syndrome (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyl), and telangiectasia), male and female autoimmune infertility, ankylosing spondolytis, ulcerative colitis, mixed connective tissue disease, polyarteritis nodosa, systemic necrotizing vasculitis, atopic dermatitis, atopic rhinitis, Goodpasture's syndrome, Chagas' disease, sarcoidosis, rheumatic fever, asthma, recurrent abortion, anti-phospholipid syndrome, farmer's lung, erythema multiforme, post cardiotomy syndrome, Cushing's syndrome, autoimmune chronic active hepatitis, bird-fancier's lung, toxic epidermal necrolysis, Alport's syndrome, alveolitis, allergic alveolitis, fibrosing alveolitis, interstitial lung disease, erythema nodosum, pyoderma gangrenosum, transfusion reaction, Takayasu's arteritis, polymyalgia rheumatica, temporal arteritis, schistosomiasis, giant cell arteritis, ascariasis, aspergillosis, Samter's syndrome, eczema, lymphomatoid granulomatosis, Behcet's disease, Caplan's syndrome, Kawasaki's disease, dengue, encephalomyelitis, endocarditis, endomyocardial fibrosis, endophthalmitis, erythema elevatum et diutinum, psoriasis, erythroblastosis fetalis, eosinophilic faciitis, Shulman's syndrome, Felty's syndrome, filariasis, cyclitis, chronic cyclitis, heterochronic cyclitis, Fuch's cyclitis, IgA nephropathy, Henoch-Schonlein purpura, graft versus host disease, transplantation rejection, cardiomyopathy, Eaton-Lambert syndrome, relapsing polychondritis, cryoglobulinemia, Waldenstrom's macroglobulemia, Evan's syndrome, and autoimmune gonadal failure.

[0339] In some embodiments, the methods described herein encompass treatment of disorders of B lymphocytes (e.g., systemic lupus erythematosus, Goodpasture's syndrome, rheumatoid arthritis, and type I diabetes), Thl-lymphocytes (e.g., rheumatoid arthritis, multiple sclerosis, psoriasis, Sjorgren's syndrome, Hashimoto's thyroiditis, Grave's disease, primary biliary cirrhosis, Wegener's granulomatosis, tuberculosis, or graft versus host disease), or Th2-lymphocytes (e.g., atopic dermatitis, systemic lupus erythematosus, atopic asthma, rhinoconjunctivitis, allergic rhinitis, Omenn's syndrome, systemic sclerosis, or chronic graft versus host disease). Generally, disorders involving dendritic cells involve disorders of Thl-lymphocytes or Th2-lymphocytes.

[0340] As used herein, a "subject" refers to a human or animal. Usually, the animal is a vertebrate such as a primate, rodent, domestic animal or game animal. Primates include chimpanzees, cynomolgus monkeys, spider monkeys, and macaques, e.g., Rhesus. Rodents include mice, rats, woodchucks, ferrets, rabbits and hamsters. Domestic and game animals include cows, horses, pigs, deer, bison, buffalo, feline species, e.g., domestic cat, canine species, e.g., dog, fox, wolf, avian species, e.g., chicken, emu, ostrich, and fish, e.g., trout, catfish and salmon. In certain embodiments, the subject is a mammal, e.g., a primate, e.g., a human. The terms, "patient," "individual," and "subject" are used interchangeably herein.

[0341] Preferably, the subject is a mammal. The mammal can be a human, non-human primate, mouse, rat, dog, cat, horse, or cow, but are not limited to these examples. Mammals other than humans can be advantageously used, for example, as subjects that represent animal models of, for example, various autoimmune diseases. In addition, the methods described herein can be used to 256 WO 2024 / 149345 PCT / CN2024 / 071901 treat domesticated animals and / or pets. A subject can be male or female. In certain embodiments, the subject is a human.

[0342] In some embodiments, a subject can be one who has been previously diagnosed with or identified as suffering from an autoimmune disease and in need of treatment, but need not have already undergone treatment for the autoimmune disease. In some embodiments, a subject can also be one who has not been previously diagnosed as having an autoimmune disease in need of treatment. In some embodiments, a subject can be one who exhibits one or more risk factors for a condition or one or more complications related to an autoimmune disease or a subject who does not exhibit risk factors. A "subject in need" of treatment for an autoimmune disease particular can be a subject having that condition or diagnosed as having that condition. In other embodiments, a subject “at risk of developing” a condition refers to a subject diagnosed as being at risk for developing the condition or at risk for having the condition again (e.g., an autoimmune disease).

[0343] As used herein, the terms "treat," "treatment," "treating," or "amelioration" when used in reference to a disease, disorder or medical condition, refer to therapeutic treatments for a condition, wherein the object is to reverse, alleviate, ameliorate, inhibit, slow down or stop the progression or severity of a symptom or condition. The term "treating" includes reducing or alleviating at least one adverse effect or symptom of a condition. Treatment is generally "effective" if one or more symptoms or clinical markers are reduced. Alternatively, treatment is "effective" if the progression of a condition is reduced or halted. That is, "treatment" includes not just the improvement of symptoms or markers, but also a cessation or at least slowing of progress or worsening of symptoms that would be expected in the absence of treatment. Beneficial or desired clinical results include, but are not limited to, reduction in autoimmune cells in the subject, alleviation of one or more symptom(s), diminishment of extent of the deficit, stabilized (i.e., not worsening) state of an autoimmune disease, delay or slowing of progression of an autoimmune disease, and an increased lifespan as compared to that expected in the absence of treatment. As used herein, the term "administering," refers to providing a conjugate as described herein to a subject by a method or route which results in binding of the conjugate to target autoimmune cells. Similarly, a pharmaceutical composition comprising a conjugate as described herein can be administered by any appropriate route which results in an effective treatment in the subject.

[0344] The dosage ranges for a conjugate depend upon the potency, and encompass amounts large enough to produce the desired effect e.g., slowing of progression of an autoimmune disease or a reduction of symptoms. The dosage should not be so large as to cause unacceptable adverse side effects. Generally, the dosage will vary with the age, condition, and sex of the subject and can be determined by one of skill in the art. The dosage can also be adjusted by the individual physician in the event of any complication. In some embodiments, the dosage ranges from 0.1 mg / kg body weight to 10 mg / kg body weight. In some embodiments, the dosage ranges from 0.5 mg / kg body weight to 15 mg / kg body weight. In some embodiments, the dose range is from 0.5 mg / kg body weight to 5 mg / kg body weight. Alternatively, the dose range can be titrated to maintain serum levels between 1 ug / mL and 1000 ug / mL. For systemic administration, subjects can be administered a therapeutic amount, such as, e.g. 0.1 mg / kg, 0.5 mg / kg, 1.0 mg / kg, 2.0 mg / kg, 2.5 mg / kg, 5 mg / kg, 257 WO 2024 / 149345 PCT / CN2024 / 071901 10 mg / kg, 12 mg / kg or more.

[0345] Administration of the doses recited above can be repeated. In a preferred embodiment, the doses recited above are administered weekly, biweekly, every three weeks or monthly for several weeks or months. The duration of treatment depends upon the subject's clinical progress and responsiveness to treatment.

[0346] In some embodiments, a dose can be from about 0.1 mg / kg to about 100 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 25 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 20 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 15 mg / kg. In some embodiments, a dose can be from about 0.1 mg / kg to about 12 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 100 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 25 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 20 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 15 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 12 mg / kg. In some embodiments, a dose can be from about 1 mg / kg to about 10 mg / kg.

[0347] In some embodiments, a dose can be administered intravenously. In some embodiments, an intravenous administration can be an infusion occurring over a period of from about 10 minutes to about 4 hours. In some embodiments, an intravenous administration can be an infusion occurring over a period of from about 30 minutes to about 90 minutes.

[0348] In some embodiments, a dose can be administered weekly. In some embodiments, a dose can be administered bi-weekly. In some embodiments, a dose can be administered about every 2 weeks. In some embodiments, a dose can be administered about every 3 weeks. In some embodiments, a dose can be administered every four weeks.

[0349] In some embodiments, a total of from about 2 to about 10 doses are administered to a subject. In some embodiments, a total of 4 doses are administered. In some embodiments, a total of 5 doses are administered. In some embodiments, a total of 6 doses are administered. In some embodiments, a total of 7 doses are administered. In some embodiments, a total of 8 doses are administered. In some embodiments, a total of 9 doses are administered. In some embodiments, a total of 10 doses are administered. In some embodiments, a total of more than 10 doses are administered.

[0350] Pharmaceutical compositions containing a conjugate thereof can be administered in a unit dose. The term "unit dose" when used in reference to a pharmaceutical composition refers to physically discrete units suitable as unitary dosage for the subject, each unit containing a predetermined quantity of active material (e.g., a conjugate), calculated to produce the desired therapeutic effect in association with the required physiologically acceptable diluent, i.e., carrier, or vehicle.

[0351] In some embodiments, a conjugate, or a pharmaceutical composition of any of these, is administered with an immunosuppressive therapy. In some embodiments, provided is a method of improving treatment outcome in a subject receiving immunosuppressive therapy. The method generally includes administering an effective amount of an immunosuppressive therapy to the subject having an autoimmune disorder; and administering a therapeutically effective amount of a 258 WO 2024 / 149345 PCT / CN2024 / 071901 conjugate or a pharmaceutical composition thereof to the subject, wherein the conjugate specifically binds to target autoimmune cells; wherein the treatment outcome of the subject is improved, as compared to administration of the immunotherapy alone. In some embodiments, the conjugate thereof as described herein. In some embodiments, an improved treatment outcome is a decrease in disease progression, an alleviation of one or more symptoms, or the like.

[0352] The present invention is further illustrated by the following embodiments which should not be construed as limiting.

[0353] Embodiment 1. A Linker compound, or a stereoisomer or salt thereof, comprising: (a) a Linker unit having from 1 to 4 attachment sites for a Drug unit and having one of the following structures (i) or (ii): (b) at least one Polar group comprising a Polymer unit, optionally a Sugar unit, optionally a Carboxyl unit, and combinations thereof; and (c) optionally a Stretcher group having an attachment site for a Targeting group; wherein: a— is an attachment site to an enzyme-cleavable group; β— is an attachment site to the at least one Polar group; δ— is H, an attachment site to at least one of the Drug units, or an attachment site to a linking group attached to the at least one of the Drug units; the Polymer unit comprises a polyamide, a polyether, or a combination thereof, wherein the polyether comprises a hydroxyl group, a polyhydroxyl group, a sugar group, a carboxyl group, or combinations thereof; each Ra independently is H or Ci-Ce alkyl; each Rb independently is halo, Ci-6 alkyl, an attachment site to at least one of the Drug units, or an attachment site to at least one of the Polar groups; x is 0, 1, 2, 3 or 4; y is 0, 1, 2 or 3; Rc is a bond, -C(O)-, -S(O)-, -SO2-, C1-6 alkylene, C1-6 alkynylene, triazolyl or combinations thereof; and Y is a bond, -O-, -S-, -N(Ra)-, -C(O)-, -S(O)-, -SO2-C1-C6 alkylene, Ci-Ce alkenylene, Ci-Ce alkynylene, a group containing triazolyl, or combinations thereof.

[0354] Embodiment 2. The Linker compound of Embodiment 1, wherein the Linker unit has one of the following structures (i-a), (ii-a), or (iii-a): 259 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer or salt thereof.

[0355] Embodiment 3. The Linker compound of Embodiment 1 or 2, wherein the Linker unit has (i-f): β Ό-δ (i-e) 260 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer or salt thereof.

[0356] Embodiment 4. The Linker compound of Embodiment 1, wherein the Linker unit has the following structure (ii-b) or (iii-b): (ii-b), (iii-b), or a stereoisomer or salt thereof.

[0357] Embodiment 5. The Linker compound of any one of Embodiments 1-4, wherein the Polar group comprises at least one Sugar unit having the following formula: L3-N(CH2- (CH(XR))k - Χι(Χ2))2 (X) or a stereoisomer or salt thereof, wherein: each X is independently selected from NH and O; each R is independently selected from hydrogen, acetyl, a monosaccharide, a disaccharide, and a polysaccharide; each Xi is independently selected from CH2 and C(O); each X2 is independently selected from H, OH and OR; k is 1 to 10; and L3 is a point of attachment to a remainder of the Polar group.

[0358] Embodiment 6. The Linker compound of Embodiment 5, wherein the at least one Sugar unit has one of the following structures (XII) or (XIII): (XIII) or a stereoisomer or salt thereof, wherein: each R is independently selected from hydrogen, a monosaccharide, a disaccharide and 261 WO 2024 / 149345 PCT / CN2024 / 071901 a polysaccharide; m is 1 to 8; and n is 0 to 4.

[0359] Embodiment 7. The Linker compound of any one of Embodiments 1-6, comprising a Polar group having a formula selected from: (a) ~R20-R21-[O-CH2-CH2]n20-R22-NR24R25 (XX) or a stereoisomer a salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-Cs alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle; and n20 is 2 to 26; or (b) ~R20-R21-[O-CH2-CH2]n20-R22-NR24R25 (XXI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is a polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; and n20 is 2 to 26; or (C) ~R20-[-R26-[R29-[O-CH2-CH2-]n20R29]n21-R27-NR24R25]n27 (XXII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R26 and R27 are each optional and are, independently, selected from a bond, C1-C12 alkylene, -NH-C1-C12 alkylene, -C1-C12 alkylene-ΝΗ-, -C1-C12 alkylene-N(CH3)-, - C(O)-Ci-Ci2 alkylene, -C1-C12 alkylene-C(O)-, -NH-C1-C12 alkylene-C(O)- and -C(O)- C1-C12 alkylene-NH-; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; 262 WO 2024 / 149345 PCT / CN2024 / 071901 substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; or -NR24R25 together from a C3-C8 heterocycle; each R29 is optional and independently selected from -C(O)-, -NH-, -C(O)-Ci-C6 alkylene-, -NH-Ci-C6 alkylene-, -Ci-C6 alkylene-ΝΗ-, -Ci-C6 alkylene-C(O)-, - NH(CO)-Ci-C6alkylene-, -N(CH3)-(CO)-Ci-C6alkylene-, -NH(CO)NH-, and triazole; n20 is 2 to 26; n21 is 1 to 4; and n27 is 1 to 4, or (d) ~R20-R21-[-C(Ra)H-C(O)-N(RN)-]n20-R22-NR24R25 (XXIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 is a bond, C1-C3 alkylene, -Ci-C3alkylene-[O-CH2-CH2-]n20, -[CH2-CH2-O]n2o-Ci-C3alkylene- or Ci-C3alkylene-[O-CH2-CH2-]n20-C(O)-; R22 is C1-C3 alkylene, -Ci-C3alkylene-[O-CH2-CH2-]n20, -[CH2-CH2-O]n2o-Ci-C3alkylene- or Ci-C3alkylene-[O-CH2-CH2-]n2crC(O)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-C6 alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-Cs alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle; and each n20 is independently 2 to 26, or (e) -R20-R21-[-C(Ra)H-C(O)-N(RN)-]il20-R22-CO2R26 (XXIV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, Ci-C3 alkylene, or -Ci-C3alkylene[0-CH2-CH2-]n2o; each Ra is independently H or -R22-NR24R25; 263 WO 2024 / 149345 PCT / CN2024 / 071901 each RN is independently H, Ci-C6 alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-Cs alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle; R26 is H or C1-C4 alkyl; and each n20 is independently 2 to 26, with the proviso that at least one Ra or RN is -R22-NR24R25; or (f) ~R20-R21-[C(Ra)H-C(O)-N(RN)-]n20-R22-N-(R23-NR24R25)2 (XXV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, C1-C3 alkylene, or -Ci-C3alkylene-[0-CH2-CH2-]n2o; each Ra is independently H or -R22-NR24R25; each RN is independently H or Ci-C6 alkyl; each R23 is independently Ci-Ce alkylene; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; and -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle; and each n20 is independently 2 to 26.

[0360] Embodiment 8. The Linker compound of claim Embodiment 7, wherein both R24 and R25 are not H.

[0361] Embodiment 9. The Linker compound of Embodiment 7 or 8, wherein R24 and R25 are each independently selected from H and a polyhydroxyl group, provided that R24 and R25 are not both H.

[0362] Embodiment 10. The Linker compound of any one of Embodiments 7 to 9, wherein the polyhydroxyl group is a linear monosaccharide, optionally selected from a C6 or C5 sugar, a sugar acid and an amino sugar.

[0363] Embodiment 11. The Linker compound of Embodiment 10, wherein: the C6 or C5 sugar is selected from glucose, ribose, galactose, mannose, arabinose, 2- deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose, talose, aldose, and ketose; the sugar acid is selected from gluconic acid, aldonic acid, uronic acid and ulosonic acid; or the amino sugar is selected from glucosamine, N-acetyl glucosamine, galactosamine, and N- 264 WO 2024 / 149345 PCT / CN2024 / 071901 acetyl galactosamine.

[0364] Embodiment 12. The Linker compound of any one of Embodiments 1 to 7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 265 WO 2024 / 149345 PCT / CN2024 / 071901 266 WO 2024 / 149345 PCT / CN2024 / 071901 267 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH R39 V 1 I z\_AANa ho γ γ > OH H 1 I ? 1 II "n-a-^nA^^n^a^o^, Ja O 1 O 1 o h p o OH HO,A ΗΟγ^οΗ OH OH (ΌΗ / A.AAa / Na HO γ > 0H 0H| ϊ 1 1 ϊ । J YAnAnAnAn^nA / Aa-a o 1 0 1 o H [ 0 1 1 N 1 N a aa.A A / a A. A / χΑ / χ / aN Y N Y N ^-^ 0 ^ Ao 1 0 H 1 0 YN\ 1 N 1 N a >^A / N. A / a / IL A / 0. / a / A / O. / N Y N Y N 0Xo । i H [ o YNa HO ''A''o^X / 0 > 0^ HO N-r39HO \__ / R Ha OH HO OH ......1.......... ............. / HO« HO \__ / A_ ZOH Ho^AAn H0 OH HO V0H "°.....A HO \~R39 HO — / ,—( OH HO OH A HO N—\ OH HO A M °H \—( HO )—\ A OH HO OH OH 268 WO 2024 / 149345 PCT / CN2024 / 071901 269 WO 2024 / 149345 PCT / CN2024 / 071901 270 WO 2024 / 149345 PCT / CN2024 / 071901 271 WO 2024 / 149345 PCT / CN2024 / 071901 wherein each R is independently H or alkyl; each R39 is independently selected from H, a linear monosaccharide and polyethylene glycol, optionally having from 1 to 24 ethylene glycol subunits; each n independently is 1-12; and the wavy line is an attachment site to Rb, or to the enzyme- cleavable group.

[0365] Embodiment 13. The Linker compound of Embodiment 7 or 8, wherein one of R24 and R25 is a linear monosaccharide and the other is a cyclic monosaccharide.

[0366] Embodiment 14. The Linker compound of any one of Embodiments 1-7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: o 272 WO 2024 / 149345 PCT / CN2024 / 071901 OH wherein R41 is a cyclic monosaccharide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0367] Embodiment 15. The Linker compound of Embodiment 7 or 8, wherein R24 and R25 are independently a polyhydroxyl selected from a cyclic monosaccharide, disaccharide and polysaccharide.

[0368] Embodiment 16. The Linker compound of any one of Embodiments 1-7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 273 WO 2024 / 149345 PCT / CN2024 / 071901 wherein each R45 is selected from H and a monosaccharide, a disaccharide, or a polysaccharide; and R46 is selected from a cyclic monosaccharide, disaccharide, or polysaccharide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0369] Embodiment 17. The Linker compound of Embodiment 7 or 8, wherein R24 and R25 are independently selected from a linear monosaccharide and a substituted linear monosaccharide, wherein the substituted linear monosaccharide is substituted with a monosaccharide, a disaccharide or a polysaccharide.

[0370] Embodiment 18. The Linker compound of any one of Embodiments 1-7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 274 WO 2024 / 149345 PCT / CN2024 / 071901 wherein R47 is a linear monosaccharide; and each R49 is selected from a monosaccharide, a disaccharide and a polysaccharide; and the wavy line is an attachment site to Rb, or to the enzyme- cleavable group.

[0371] Embodiment 19. The Linker compound of Embodiment 7 or 8, wherein R24 and R25 are independently selected from a linear monosaccharide and a substituted monosaccharide, wherein the substituted linear monosaccharide is substituted with one or more substituents selected from alkyl, O-alkyl, aryl, O-aryl, carboxyl, ester, or amide, and optionally further substituted with a monosaccharide, disaccharide or a polysaccharide.

[0372] Embodiment 20. The Linker compound of any one of Embodiments 1-7, comprising a Polar wherein each R42 is independently selected from a linear monosaccharide and a substituted linear monosaccharide; each R43 is independently selected from alkyl, O-alkyl, aryl, O-aryl, carboxyl, ester, and amide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0373] Embodiment 21. The Linker compound of any one of Embodiments 7 to 8, wherein one of R24 and R25 is a -C(O)-polyhydroxyl group or substituted -C(O)-polyhydroxyl group, and the other of R24 and R25 is a H, -C(O)-polyhydroxyl group, substituted -C(O)-polyhydroxyl group, polyhydroxyl 275 WO 2024 / 149345 PCT / CN2024 / 071901 group or substituted polyhydroxyl group; wherein the substituted -C(O)-polyhydroxyl group and polyhydroxyl group are substituted with a monosaccharide, a disaccharide, a polysaccharide, alkyl, - O-alkyl, aryl, carboxyl, ester, or amide.

[0374] Embodiment 22. The Linker compound of any one of Embodiments 1-21, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0375] Embodiment 23. The Linker compound of Embodiment 7 or 8, wherein R24 and R25 are independently selected from a H, substituted -Ci-C8 alkyl, substituted -C1-C4 alkyl or substituted -Ci- C8 alkyl; provided that both R24 and R25 are not H; wherein substituted -Ci-C8 alkyl, -C1-C4 alkyl, and -C1-C3 alkyl are substituted with hydroxyl and / or carboxyl.

[0376] Embodiment 24. The Linker compound of Embodiments 1-7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: OH 276 WO 2024 / 149345 PCT / CN2024 / 071901 OH O OH OH O OH OH O wherein R48 is selected from H, OH, CH2OH, COOH or -Ci-C6 alkyl substituted with hydroxyl or carboxyl; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0377] Embodiment 25. The Linker compound of Embodiment 7 or 8, wherein one of R24 and R25 is selected from H, substituted -C(O)-Ci-C8 alkyl, substituted -C(O)-Ci-C4 alkyl, and substituted -C(O)- C1-C3 alkyl and the other of R24 and R25 is selected from substituted -C(O)-Ci-C8 alkyl, substituted - C(O)-Ci-C4 alkyl, substituted -C(O)-Ci-C3 alkyl, substituted -Ci-Cs alkyl, substituted -C1-C4 alkyl, and substituted -Ci-C3 alkyl, wherein substituted -C(O)-Ci-Cs alkyl, substituted -C(O)-Ci-C4 alkyl, substituted -C(O)-Ci-C3 alkyl, substituted -Ci-C8 alkyl, -Ci-C4 alkyl and -C1-C3 alkyl are substituted with hydroxyl and / or carboxyl.

[0378] Embodiment 26. The Linker compound of any one of Embodiments 1-7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: 277 WO 2024 / 149345 PCT / CN2024 / 071901 HO^^° O Y ho η OH OH X^\ / 0. ^ / 0. ^\,NH 0 0 0 0 tY^"^ 0 Ο^,ΟΗ HO J \ / \ / O. / \ / \ / O. / \ ,ΝΗ 5Y OT Y \ / ο II \ ° OH OH °=\ X^\O / \ / \O / \ / \ ^NH / γ 7Y. ° O HO I OH OH C / NH \ γ γ ο II I0 OH OH O ^^Ο^θ^Ο^θ^ / ΝΗ AY o II o o % o o / \ YH ϋ ° ° II 1 O OH H OH :O ) OH OH "ΌΗ and 278 WO 2024 / 149345 PCT / CN2024 / 071901 wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0379] Embodiment 27. The Linker compound of any one of Embodiments 6 to 8, wherein R24 and R25 are selected from H and optionally substituted aryl; provided that both R24 and R25 are not H.

[0380] Embodiment 28. The Linker compound of any one of Embodiments 1-7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: Br and Cl wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group .

[0381] Embodiment 29. The Linker compound of Embodiment 7 or 8, wherein R24 and R25 together form an optionally substituted C3-C8 heterocycle or heteroaryl.

[0382] Embodiment 30. The Linker compound of any one of Embodiments 1-7, comprising a Polar group having the following structure: o or a stereoisomer or salt thereof, wherein the wavy line is an attachment site to Rb, or to the enzyme- cleavable group.

[0383] Embodiment 31. The Linker compound of Embodiment 7 or 8, wherein R24 and R25 are independently selected from H and a chelator, wherein the chelator is optionally attached to the nitrogen of -NR24R25 by an alkylene, arylene, carbocyclo, heteroarylene or heterocarbocylo; provided that both R24 and R25are not H.

[0384] Embodiment 32. The Linker compound of Embodiment 31, wherein the chelator is selected from ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), benzyl-DTPA, 1,4,7,10-tetraazacyclododecane- N,N',N",N'"-tetraacetic acid (DOTA), benzyl-DOTA, l,4,7-triazacyclononane-N,N',N"-triacetic acid (NOTA), benzyl-NOTA, l,4,8,ll-tetraazacyclotetradecane-l,4,8,ll-tetraacetic acid (TETA) and Ν,Ν'-dialkyl substituted piperazine. 279 WO 2024 / 149345 PCT / CN2024 / 071901

[0385] Embodiment 33. The Linker compound of any one of Embodiments 1-7, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0386] Embodiment 34. The Linker compound of any one of Embodiments 6 to 21, wherein each monosaccharide is independently selected from: a C5 or C6 sugar selected from glucose, ribose, galactose, mannose, arabinose, 2- deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose talose, aldose, ketose, glucosamine, N-acetyl glucosamine, galactosamine, and N- acetyl galactosamine; a sugar acid selected from gluconic acid, aldonic acid, uronic acid and ulosonic acid; or an amino sugar is selected from glucosamine, N-acetyl glucosamine, galactosamine, and N- acetyl galactosamine.

[0387] Embodiment 35. The Linker compound of any one of Embodiments 1 to 34, wherein the attachment site is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, and protected forms thereof.

[0388] Embodiment 36. The Linker compound of any one of Embodiments 1 to 35, comprising a Polar group having a formula selected from the following: (a) ~R20-R21-[O-CH2-CH2]n20-R22-R30 (XXX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently, a bond or C1-C3 alkylene groups; R30 is selected from an optionally substituted C3-C10 carbocycle; thiourea; optionally substituted thiourea; urea; optionally substituted urea; sulfamide; alkyl sulfamide; acyl sulfamide, optionally substituted alkyl sulfamide; optionally substituted acyl sulfamide; sulfonamide; optionally substituted sulfonamide; guanidine, including alkyl 280 WO 2024 / 149345 PCT / CN2024 / 071901 and aryl guanidine; phosphoramide; or optionally substituted phosphoramide; or R30 is selected from azido, alkynyl, substituted alkynyl, -NH-C(O)-alkynyl, -NH-C(O)- alkynyl-R65; cyclooctyne; -NH-cyclooctyne, -NH-C(O)-cyclooctyne, or -NH- (cyclooctyne)2; wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (b) ~R20-R21-[O-CH2-CH2]n20-R22-NH-C(O)-R31 (XXXI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (c) ~R20-R21-[O-CH2-CH2]n20-R22-C(O)NH-R31 (XXXII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each , independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch, independently, having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle and optionally substituted heteroaryl; and n20 is 2 to 26; (d) ~R20-R21-[O-CH2-CH2]n20-R22-C(O)NR31-R22-NR24R25 (XXXIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R31 is H or R22-NR24R25; R21 and R22 are each, independently, a bond or C1-C3 alkylene groups; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group, provided that R24 and R25 are not both H; and n20 is 2 to 26; (e) ~R20-R21-[O-CH2-CH2]n20-R22-N(R33-R31)2 (XXXIV) 281 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus; R33 is C1-C3 alkylene, C1-C3 alkylene-C(O), -C(O)-Ci-C3 alkylene, or -C(O)-Ci-C3 alkylene-C(O); R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and n20 is 2 to 26; (f) ~R20-(R21-[CH2-CH(OR34)-CH2-O]n2o-R36)n25 (XXXV) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; each R21 is independently a bond, -O- or Ci-C3 alkylene group; each R34 is independently H, -[CH2-CH(OH)-CH2-O]n2o-R36, -C(O)-NR24R25 or C(O)N(RN)-Ci-C6alkylene-NR24R25; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; or substituted polyhydroxyl group, provided that both R24 and R25 are not H; each R36 is independently H, Ci-C6alkylene-C(OH)H-NR44R45, Ci-C6alkylene-C(OH)H- Ci-C6alkylene-NR44R45, -C(O)-NR24R25, -C(O)N(RN)-Ci-C6alkylene-NR24R25, Ci- C6alkylene-C(O)NR24R25 or Ci-C6alkylene-CO2R37; each R37 is independently H or Ci-Ce alkyl; R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; provided that both R44and R45are not H; each n20 is independently 1 to 26; and n25 is 1 or 2; (g) ~R20-R21-[[CH2-CH2-O]n20-R22-[CH2-[CH(OH)]n23-CH2-O]n2i]n22-R23-NR24-R25 (XXXVI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21, R22 and R23 are each independently a bond or Ci-C3 alkylene group; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group, provided that R24 and R25 are not both H; each n20 is independently 0 to 26, and each n21 is independently 0 to 26, with the proviso that at least one of n20 or n21 is 2 to 26; 282 WO 2024 / 149345 PCT / CN2024 / 071901 n22 is 1 to 5; each n23 is independently 1 or 2; (h) A2AR21-[O-CH2-CH2]n20-R22-N(RN)-CO2-[CH2-CH(OR34)-CH2-O]ri2i-R36)ri25 (XXXVII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently a bond or Ci-C3 alkylene groups; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; or substituted polyhydroxyl group, provided that both R24 and R25 are not H; each R34 is independently H, -[CH2-CH(OH)-CH2-O]n2o-R36 or -C(O)N(RN)-Ci-C6alkylene- NR24R25; each R36 is independently H, Ci-C6alkylene-C(OH)H-NR44R45, Ci-C6alkylene-C(OH)H- Ci-C6alkylene-NR44R45, -C(O)N(RN)-Ci-C6alkylene-NR24R25, Ci-C6alkylene- C(O)NR24R25 or Ci-C6alkylene-CO2R37; each R37 is independently H or Ci-C6 alkyl; R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; provided that both R44 and R45 are not H; n20 is 2 to 26; n21 is 1 to 26; and n25 is 1 or 2; (i) A20-(R21-[N(RN)-C(O)-[O-CH2-CH(OH)-CH2]n^ (XXXVIII) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each independently bond or C1-C3 alkylene groups; RN is H or Ci-C4alkyl; R24 and R25 are each independently selected from a H; polyhydroxyl group; or substituted polyhydroxyl group, provided that R24 and R25 are not both H; n20 is 2 to 26; n21 is 1 to 4; and n25 is 1, 2 or 3; (j) ~R20-(R21-[C(Ra)H-C(O)-N(RN)]n20-R22-[CH2-CH2-O]n20-NR24R25)n25 (XXXIX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, a bond, C1-C3 alkylene,-Ci-C3alkylene-[O-CH2- CH2-]n2o, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[0-CH2-CH2-]n2o-C(0)-; each Ra is independently H or -R22-NR24R25; 283 WO 2024 / 149345 PCT / CN2024 / 071901 each RN is independently H, Ci-C6 alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; -C(O)-R28, wherein R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle), provided that R24 and R25 are not both H; each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; and n25 is 1 or 2; or (k) ~R20-R21-[C(Ra)H-C(O)-N(RN)]n20-R22-[CH2-CH2-O]n20-NR24R25 R21-[C(Ra)H-C(O)-N(RN)]n2i-R22-[CH2-CH2-O]n2i-R23-CO2-R26 (XXXVX) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21, R22 and R23 are each, independently, a bond, C1-C3 alkylene,-Ci-C3alkylene-[O- CH2-CH2-]n2o, -[CH2-CH2-O]n2o-Ci-C3alkylene- or -Ci-C3alkylene-[0-CH2-CH2-]n2o- C(O)-; each Ra is independently H or -R22-NR24R25; each RN is independently H, Ci-Ce alkyl or -R22-NR24R25; R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); or -NR24R25 together from a C3-C8 heterocycle), provided that R24 and R25 are not both H; R26 is H or Ci-Cs alkyl; each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; and each n21 is independently 0 to 26, with the proviso that at least one n21 is 2 to 26.

[0389] Embodiment 37. The Linker compound of any one of Embodiments 1 to 36, comprising a Polar group having a formula selected from the following, or a stereoisomer or salt thereof: ~R20-R21-[O-CH2-CH2]n20-R22-NH-C(O)-R31 (XXXI), ~R2°-R21-[0-CH2-CH2]n2o-R22-C(0)NH-R31 (XXXII), and ~R20-R21-[O-CH2-CH2]n20-R22-N-(R33-R31)2 (XXXIII); wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R21 and R22 are each, independently, bond or C1-C3 alkylene groups; R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol 284 WO 2024 / 149345 PCT / CN2024 / 071901 subunits and each branch having an R35 at its terminus; R33 is C1-C3 alkylene, -C1-C3 alkylene-C(O), -C(O)-Ci-C3 alkylene or -C(O)-Ci-C3 alkylene- C(O); R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; the wavy (~) line indicates an attachment site to R20; and n20 is 2 to 26.

[0390] Embodiment 38. The Linker compound of any one of Embodiments 1-37, comprising a Polar group formed from a precursor group selected from the following: 285 WO 2024 / 149345 PCT / CN2024 / 071901 wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.

[0391] Embodiment 39. The Linker compound of any one of Embodiments 36 to 38, wherein the attachment site to Rb, or to the enzyme-cleavable group is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, and protected forms thereof.

[0392] Embodiment 40. The Linker compound of any one of Embodiments 1-39, comprising a Polar group having a formula: ~R20.(R43.R41.[O-CH2-CH2]n40-R42-R43-(NR44R45)n41)n42 (XL) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, bond or Ci-C6 alkylene; each R43 is, independently, a bond or is selected from C1-C12 alkylene, -NH-C1-C12 alkylene, -C1-C12 alkylene-ΝΗ-, -C(O)-Ci-Ci2 alkylene, -C1-C12 alkylene-C(O)-, -NH-C1-C12 286 WO 2024 / 149345 PCT / CN2024 / 071901 alkylene-C(O)-, -C(O)-Ci-Ci2 alkylene-ΝΗ-, -NH-C(O)-NH-, -NH-C(O)-, -NH-C(O)-Ci-Ci2 alkylene, -C(O)-NH-Ci-Ci2 alkylene, -heteroarylene, heteroaryl-Ci-Ci2 alkylene, heteroaryl-Ci-Ci2 alkylene-C(O)-, or -C(O)NR46R47, wherein one of R46 and R47 is H or Ci-Ci2 alkylene and the other is C1-C12 alkylene; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate; n40 is 2 to 26; n41 is 1 to 6; and n42 is 1 to 6.

[0393] Embodiment 41. The Linker compound of any one of Embodiments 1-40, comprising a Polar group having a formula: ~R2°-(R41-[O-CH2-CH2]n40-R42-R43-(NR44R^ (XLI) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, bond or Ci-C6 alkylene; R43 is a bond or is selected from Ci-Ci2 alkylene, -NH-Ci-Ci2 alkylene, -C1-C12 alkylene-ΝΗ-, -C(O)-Ci-Ci2 alkylene, -C1-C12 alkylene-C(O)-, -NH-Ci-Ci2 alkylene-C(O)-, -C(O)-Ci-Ci2 alkylene-ΝΗ-, -NH-C(O)-NH-, -NH-C(O)-, -NH-C(O)-Ci-Ci2 alkylene, C(O)-NH-Ci-Ci2 alkylene, -heteroarylene, heteroaryl-Ci-Ci2 alkylene, heteroaryl-Ci-Ci2 alkylene-C(O)-, or -C(O)NR46R47, wherein one of R46 and R47 is H or C1-C12 alkylene and the other is C1-C12 alkylene; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate; n40 is 1 to 26; n41 is 1 to 6; and n42 is 1 to 6.

[0394] Embodiment 42. The Linker compound of any one of Embodiments 1-41, comprising a Polar group having a formula: ~R20-(R41.[O-CH2-CH2]n40-R42-R43-(NR44R45)n41)n42 (XLI I) or a stereoisomer or salt thereof, wherein: R20 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, bond or C1-C3 alkylene; R43 is a bond or is selected from Ci-Ce alkylene, -NH-Ci-Ci2 alkylene, -Ci-Ce alkylene-ΝΗ-, - C(O)-Ci-C6 alkylene, -Ci-Ce alkylene-C(O)-, -NH-Ci-Ce alkylene-C(O)-, -C(O)-Ci-C6 alkylene-ΝΗ-, -NH-C(O)-NH-, -NH-C(O)-, -NH-C(O)-Ci-C6 alkylene, -C(O)-NH-Ci-Ci2 alkylene, -heteroarylene, heteroaryl-Ci-C6 alkylene, heteroaryl-Ci-C6 alkylene-C(O)-, or - C(O)NR46R47, wherein one of R46 and R47 is H or Ci-Ce alkylene and the other is C1-C12 alkylene; 287 WO 2024 / 149345 PCT / CN2024 / 071901 R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate; n40 is 1 to 16; n41 is 1 to 4; and n42 is 1 to 4.

[0395] Embodiment 43. The Linker compound of any one of Embodiments 7, 36, 37 and 40-42, wherein R20 is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, or protected forms thereof.

[0396] Embodiment 44. The Linker compound of any one of Embodiments 7, 36, 37 and 40-42, wherein R20 comprises one of the following structures: 288 WO 2024 / 149345 PCT / CN2024 / 071901 R * or a stereoisomer thereof, wherein R is H, Ci-Ce alkyl or polyhydroxyl group, n is 0 to 12, the (-^ *) indicates an attachment site to Rb, or to the enzyme-cleavable group, and the (-^) indicates an attachment site to a remainder portion of the Polar group.

[0397] Embodiment 45. The compound of any one of Embodiments 7, 36, 37 and 40-42, wherein R20 has one of the following structures: 289 WO 2024 / 149345 PCT / CN2024 / 071901 290 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer thereof, wherein n = 0 to 12, the (-^ *) indicates an attachment site to Rb, or to the enzyme-cleavable group, and the (-^) indicates an attachment site to a remainder portion of the Polar group.

[0398] Embodiment 46. The Linker compound of any one of Embodiments 40-45, wherein R43-(NR44R45)n4i has one of the following structures: 291 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer thereof, wherein R = H, Ci-C6 alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group; and the (-^) indicates the attachment site of R43 to the remainder of the Polar group.

[0399] Embodiment 47. The Linker compound of any one of Embodiments 40-45, wherein R43-(NR44R45)n4i has one of the following structures: or a stereoisomer thereof, wherein the (-^) indicates the attachment site of R43 to the remainder of the Polar group.

[0400] Embodiment 48. The Linker compound of any one of Embodiments 40-47, wherein -NR44R45 has one of the following structures: 292 WO 2024 / 149345 PCT / CN2024 / 071901 293 WO 2024 / 149345 PCT / CN2024 / 071901 or a stereoisomer thereof, wherein the (-^) indicates the attachment site of -NR44R45 to the remainder of the Polar group.

[0401] Embodiment 49. The Linker compound of any one of Embodiments 1-48, comprising a Polar group having one of the following structures prior to attachment to the Linker Unit: OH 294 WO 2024 / 149345 PCT / CN2024 / 071901 OH 295 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH 296 WO 2024 / 149345 PCT / CN2024 / 071901 297 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH OH 298 WO 2024 / 149345 PCT / CN2024 / 071901 299 WO 2024 / 149345 PCT / CN2024 / 071901 300 WO 2024 / 149345 PCT / CN2024 / 071901 301 WO 2024 / 149345 PCT / CN2024 / 071901 302 WO 2024 / 149345 PCT / CN2024 / 071901 303 WO 2024 / 149345 PCT / CN2024 / 071901 HO H2N OH 304 WO 2024 / 149345 PCT / CN2024 / 071901 305 WO 2024 / 149345 PCT / CN2024 / 071901 306 WO 2024 / 149345 PCT / CN2024 / 071901 307 WO 2024 / 149345 PCT / CN2024 / 071901 HO HO 308 WO 2024 / 149345 PCT / CN2024 / 071901 309 WO 2024 / 149345 PCT / CN2024 / 071901 310 WO 2024 / 149345 PCT / CN2024 / 071901 311 WO 2024 / 149345 PCT / CN2024 / 071901 OH OH 312 WO 2024 / 149345 PCT / CN2024 / 071901 313 WO 2024 / 149345 PCT / CN2024 / 071901 314 WO 2024 / 149345 PCT / CN2024 / 071901 315 WO 2024 / 149345 PCT / CN2024 / 071901 R O O 316 WO 2024 / 149345 PCT / CN2024 / 071901 317 WO 2024 / 149345 PCT / CN2024 / 071901 wherein: each R is independently H or Ci-C6 alkyl; R’ is H, Ci-C6 alkyl, -N(R24)(R25) or -CO2H; each n is independently 1 to 12; X is O, NR or -CH2-; V is bond or Ci-Ce alkyl; one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3-C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; -C(O)-polyhydroxyl group; substituted -C(O)-polyhydroxyl group; optionally substituted C3-C10 carbocycle; optionally substituted C1-C3 alkylene C3- C10 carbocycle; optionally substituted heteroaryl; optionally substituted carbocycle; substituted -Ci-C8 alkyl; substituted -C(O)-Ci-C8 alkyl; a chelator; -C(O)-R28, where R28 is a Sugar unit of formula (XII) or (XIII); and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; or -NR24R25 together from a C3-C8 heterocycle.

[0402] Embodiment 50. The Linker compound of any one of Embodiments 1-49, comprising a Polar group having a formula selected from: (a) ~R40-(R43-R41-[O-CH2-CH2]n40-R46-[O-CH2-CH2]n40-R42-R43-(NR44R45)n41)n42 (XLIII) or a stereoisomer or salt thereof, wherein: R40 is an attachment group to site Rb, or to the enzyme-cleavable group; R41 and R42 are each, independently, bond or Ci-Ce alkylene; each R43 is, independently, selected from a bond, C1-C12 alkylene, -NH-C1-C12 alkylene, -Ci- C12 alkylene-ΝΗ-, -C(O)-Ci-Ci2 alkylene, -C1-C12 alkylene-C(O)-, -NH-C1-C12 alkylene- C(O)-, -C(O)-C1-C12 alkylene-ΝΗ-, -NH-C(O)-NH-, -NH-C(O)-, -NH-C(O)-Ci-Ci2 alkylene, -C(O)-NH-Ci-Ci2 alkylene, Ci-Ci2alkylene-NH-C(O)-, -heteroarylene, heteroaryl-Ci-Ci2 alkylene, heteroaryl-Ci-Ci2 alkylene-C(O)-, or -C(O)NR46R47, wherein one of R46 and R47 is H or Ci-Ci2 alkylene and the other is Ci-Ci2 alkylene; R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C(O)-polyhydroxyl group, or substituted -C(O)-polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate; 318 WO 2024 / 149345 PCT / CN2024 / 071901 each R46 is independently selected from -NR50-, -NR50-Ci-C6alkylene-NR50-, -NR50-C(O)- NR50-S(O)2-NR50- or -NR50-C(O)-Ci-6alkylene-; each R50 is independently selected from H, Ci-C6 alkyl, or polyhydroxyl group; n40 is 2 to 26; n41 is 1 to 6; and n42 is 1 to 6; (b) ~R40-(R51-[O-CH2-CH2]n43-R52-Xi-R55-X2-R5HO-CH2-CH2]n43-R54W (XLIV) or a stereoisomer or salt thereof, wherein: R40 is an attachment group to site Rb, or to the enzyme-cleavable group; R51, R52, R53 and R54 are each, independently, bond or Ci-C6 alkylene; Xi, X2 and X3 are each independently -NRN-C(O)- or -C(O)-NRN-; each RN independently represent H, Ci-C6 alkyl, or polyhydroxyl group; R55 and R56 each independently represent a bivalent polyhydroxyl group; R57 is H, OH or Ci-C6 alkyl; each n43 is independently 0 to 26, with the proviso that at least one n43 is 1 to 26; n44 is 0 to 10; and n45 is 1 or 2; or (c) ~R40-R51-[O-CH2-CH2]n43-R52-N-(R53-Xi-R54-[O-CH2-CH2]n43-(NR44R45))2 (XLV) or a stereoisomer or salt thereof, wherein: R40 is an attachment group to site Rb, or to the enzyme-cleavable group; R51, R53 and R54 are each, independently, bond or optionally-substituted Ci-Ce alkylene; R52 is a bond, Ci-C6 alkylene, -C(O)- or -O-C(O)-; each Xi is independently -NRN-C(O)- or -C(O)-NRN-; each RN independently represent H, Ci-C6 alk...

Claims

1.A Linker compound, or a stereoisomer or salt thereof, comprising:(a) a Linker unit having from 1 to 4 attachment sites for a Drug unit and having one of the following structures (i) or (ii) :(b) at least one Polar group comprising a Polymer unit, optionally a Sugar unit, optionally a Carboxyl unit, and combinations thereof; and(c) optionally a Stretcher group having an attachment site for a Targeting group;wherein:α-is an attachment site to an enzyme-cleavable group;β-is an attachment site to the at least one Polar group;δ-is H, an attachment site to at least one of the Drug units, or an attachment site to a linking group attached to the at least one of the Drug units;the Polymer unit comprises a polyamide, a polyether, or a combination thereof, wherein the polyether comprises a hydroxyl group, a polyhydroxyl group, a sugar group, a carboxyl group, or combinations thereof;each Ra independently is H or C1-C6 alkyl;each Rb independently is halo, C1-6 alkyl, an attachment site to at least one of the Drug units, or an attachment site to at least one of the Polar groups;x is 0, 1, 2, 3, or 4;y is 0, 1, 2, or 3;Rc is a bond, -C (O) -, -S (O) -, -SO2-, C1-6 alkylene, C1-6 alkynylene, triazolyl, or combinations thereof; andY is a bond, -O-, -S-, -N (Ra) -, -C (O) -, -S (O) -, -SO2-C1-C6 alkylene, C1-C6 alkenylene, C1-C6 alkynylene, a group containing triazolyl, or combinations thereof.2.The Linker compound of claim 1, wherein the Linker unit has one of the following structures (i-a) , (ii-a) , or (iii-a) : or a stereoisomer or salt thereof.3.The Linker compound of claim 1, wherein the Linker unit has one of the following structures (i-b) , (i-c) , (i-d) , (i-e) , or (i-f) : or a stereoisomer or salt thereof.4.The Linker compound of claim 1, wherein the Linker unit has the following structure (ii-b) or (iii-b) : or a stereoisomer or salt thereof.5.The Linker compound of any one of claims 1-4, wherein the at least one Polar group comprises at least one Sugar unit having the following formula: L3–N (CH2 – (CH (XR) ) k –X1 (X2) ) 2    (X)or a stereoisomer or salt thereof, wherein:each X is independently selected from NH and O;each R is independently selected from hydrogen, acetyl, a monosaccharide, a disaccharide, and a polysaccharide;each X1 is independently selected from CH2 and C (O) ;each X2 is independently selected from H, OH and OR;k is 1 to 10; andL3 is a point of attachment to a remainder of the Polar group.6.The Linker compound any one of claims 1-4, wherein the at least one Sugar unit has one of the following structures (XII) or (XIII) : or a stereoisomer or salt thereof, wherein:each R is independently selected from hydrogen, a monosaccharide, a disaccharide and a polysaccharide;m is 1 to 8; andn is 0 to 4.7.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula selected from:(a) ～R20-R21- [O-CH2-CH2] n20-R22-NR24R25     (XX)or a stereoisomer a salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond or C1-C3 alkylene;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted C1-C8 alkyl; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) , provided that R24 and R25 are not both H; andn20 is 2 to 26; or(b) ～R20-R21- [O-CH2-CH2] n20-R22-NR24R25      (XXI)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond or C1-C3 alkylene;one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted C1-C8 alkyl; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) ; and the other of R24 and R25 is a polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits; andn20 is 2 to 26; or(c) ～R20- [-R26- [R29- [O-CH2-CH2-] n20R29] n21-R27-NR24R25] n27    (XXII)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R26 and R27 are each optional and are, independently, selected from a bond, C1-C12 alkylene, -NH-C1-C12 alkylene, -C1-C12 alkylene-NH-, -C1-C12 alkylene-N (CH3) -, -C (O) -C1-C12 alkylene, -C1-C12 alkylene-C (O) -, -NH-C1-C12 alkylene-C (O) -and -C (O) -C1-C12 alkylene-NH-;one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted C1-C8 alkyl; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) ; and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group, where R28 is a Sugar unit of formula (XII) or (XIII) ; and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits, provided that R24 and R25 are not both H;each R29 is optional and independently selected from -C (O) -, -NH-, -C (O) -C1-C6 alkylene-, -NH-C1-C6 alkylene-, -C1-C6 alkylene-NH-, -C1-C6 alkylene-C (O) -, -NH(CO) -C1-C6alkylene-, -N (CH3) - (CO) -C1-C6alkylene-, -NH (CO) NH-, and triazole;n20 is 2 to 26;n21 is 1 to 4; andn27 is 1 to 4, or(d) ～R20-R21- [-C (Rα) H-C (O) -N (RN) -] n20-R22-NR24R25    (XXIII)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 is a bond or C1-C3 alkylene,-C1-C3alkylene- [O-CH2-CH2-] n20, - [CH2-CH2-O] n20-C1-C3alkylene-or -C1-C3alkylene- [O-CH2-CH2-] n20-C (O) -;R22 is C1-C3 alkylene, -C1-C3alkylene- [O-CH2-CH2-] n20, - [CH2-CH2-O] n20-C1-C3alkylene-or -C1-C3alkylene- [O-CH2-CH2-] n20-C (O) -;each Rα is independently H or -R22-NR24R25;each RN is independently H, C1-C6 alkyl or -R22-NR24R25;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted C1-C8 alkyl; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) , provided that R24 and R25 are not both H; andeach n20 is independently 2 to 26, or(e) ～R20-R21- [-C (Rα) H-C (O) -N (RN) -] n20-R22-CO2R26      (XXIV)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond, C1-C3 alkylene, or-C1-C3alkylene [O-CH2-CH2-] n20;each Rα is independently H or -R22-NR24R25;each RN is independently H, C1-C6 alkyl or -R22-NR24R25;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted C1-C8 alkyl; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) , provided that R24 and R25 are not both H;R26 is H or C1-C4 alkyl; andeach n20 is independently 2 to 26,with the proviso that at least one Rα or RN is -R22-NR24R25; or(f) ～R20-R21- [C (Rα) H-C (O) -N (RN) -] n20-R22-N- (R23-NR24R25) 2     (XXV)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond, C1-C3 alkylene, or-C1-C3alkylene- [O-CH2-CH2-] n20;each Rα is independently H or -R22-NR24R25;each RN is independently H or C1-C6 alkyl;each R23 is independently C1-C6 alkylene;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted C1-C8 alkyl; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) , provided that R24 and R25 are not both H; andeach n20 is independently 2 to 26.8.The Linker compound of claim 7, wherein R24 and R25 are each independently selected from H and a polyhydroxyl group, provided that R24 and R25 are not both H.9.The Linker compound of claim 7 or 8, wherein the polyhydroxyl group is a linear monosaccharide, optionally selected from a C6 or C5 sugar, a sugar acid, and an amino sugar.10.The Linker compound of claim 9, wherein:the C6 or C5 sugar is selected from glucose, ribose, galactose, mannose, arabinose, 2-deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose, talose, aldose, and ketose;the sugar acid is selected from gluconic acid, aldonic acid, uronic acid, and ulosonic acid; orthe amino sugar is selected from glucosamine, N-acetyl glucosamine, galactosamine, and N-acetyl galactosamine.11.The Linker compound of any one of claims 7 to 10, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein each R is independently H or alkyl; each R39 is independently selected from H, a linear monosaccharide and polyethylene glycol, optionally having from 1 to 24 ethylene glycol subunits; each n independently is 1-12; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.12.The Linker compound of claim 7 or 8, wherein one of R24 and R25 is a linear monosaccharide and the other is a cyclic monosaccharide.13.The Linker compound of claim 12, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein R41 is a cyclic monosaccharide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.14.The Linker compound of claim 7, wherein R24 and R25 are independently a polyhydroxyl selected from a cyclic monosaccharide, disaccharide, and polysaccharide.15.The Linker compound of claim 14, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein each R45 is selected from H and a monosaccharide, a disaccharide, or a polysaccharide; and R46 is selected from a cyclic monosaccharide, disaccharide, or polysaccharide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.16.The Linker compound of claim 7, wherein R24 and R25 are independently selected from a linear monosaccharide and a substituted linear monosaccharide, wherein the substituted linear monosaccharide is substituted with a monosaccharide, a disaccharide, or a polysaccharide.17.The Linker compound of claim 16, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein R47 is a linear monosaccharide; and each R49 is selected from a monosaccharide, a disaccharide, and a polysaccharide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.18.The Linker compound of claim 7, wherein R24 and R25 are independently selected from a linear monosaccharide and a substituted monosaccharide, wherein the substituted linear monosaccharide is substituted with one or more substituents selected from carboxyl, ester, and amide, and optionally further substituted with a monosaccharide, disaccharide, or a polysaccharide.19.The Linker compound of claim 18, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein each R42 is independently selected from a linear monosaccharide and a substituted linear monosaccharide; each R43 is independently selected from hydroxyl, carboxyl, ester, and amide; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.20.The Linker compound of claim 7, wherein one of R24 and R25 is a -C (O) -polyhydroxyl group  or substituted -C (O) -polyhydroxyl group, and the other of R24 and R25 is a H, -C (O) -polyhydroxyl group, substituted -C (O) -polyhydroxyl group, polyhydroxyl group or substituted polyhydroxyl group; wherein the substituted -C (O) -polyhydroxyl group and polyhydroxyl group are substituted with a monosaccharide, a disaccharide, a polysaccharide, carboxyl, ester, or amide.21.The Linker compound of claim 18 or 20, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.22.The Linker compound of claim 7, wherein R24 and R25 are independently H or substituted -C1-C8 alkyl, provided that both R24 and R25 are not H; wherein substituted -C1-C8 alkyl is substituted with hydroxyl and / or carboxyl.23.The Linker compound of claim 22, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein R48 is selected from H, OH, CH2OH, COOH, or -C1-C6 alkyl substituted with hydroxyl or carboxyl; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group .24.The Linker compound of claim 7, wherein one of R24 and R25 is H or substituted -C (O) -C1-C8 alkyl, and the other of R24 and R25 is substituted -C (O) -C1-C8 alkyl, or substituted -C1-C8 alkyl, , wherein substituted -C (O) -C1-C8 alkyl and substituted -C1-C8 alkyl, are substituted with hydroxyl and / or carboxyl.25.The Linker compound of claim 24, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.26.The Linker compound of claim 7, wherein R24 and R25 are independently selected from H and a chelator, wherein the chelator is optionally attached to the nitrogen of -NR24R25 by an alkylene, arylene, carbocyclo, heteroarylene, or heterocarbocylo; provided that both R24 and R25 are not H.27.The Linker compound of claim 26, wherein the chelator is selected from ethylenediaminetetraacetic acid (EDTA) , diethylenetriaminepentaacetic acid (DTPA) , triethylenetetraminehexaacetic acid (TTHA) , benzyl-DTPA, 1, 4, 7, 10-tetraazacyclododecane-N, N', N”, N”'-tetraacetic acid (DOTA) , benzyl-DOTA, 1, 4, 7-triazacyclononane-N, N', N”-triacetic acid (NOTA) , benzyl-NOTA, 1, 4, 8, 11-tetraazacyclotetradecane-1, 4, 8, 11-tetraacetic acid (TETA) and N, N'-dialkyl substituted piperazine.28.The Linker compound of claim 27, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein the wavy line is an attachment site to Rb, or to the enzyme-cleavable group .29.The Linker compound of any one of claims 6 to 20, wherein each monosaccharide is independently selected from:a C5 or C6 sugar selected from glucose, ribose, galactose, mannose, arabinose, 2-deoxyglucose, glyceraldehyde, erythrose, threose, xylose, lyxose, allose, altrose, gulose, idose talose, aldose, and ketose;a sugar acid selected from gluconic acid, aldonic acid, uronic acid and ulosonic acid; oran amino sugar selected from glucosamine, N-acetyl glucosamine, galactosamine, and N-acetyl galactosamine.30.The Linker compound of any one of claims 1 to 29, wherein the attachment site is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, and protected forms thereof.31.The Linker compound of any one of claims 1 to 6, comprising a Polar group having a formula selected from the following:(a) ～R20-R21- [O-CH2-CH2] n20-R22-R30    (XXX)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each independently, a bond or C1-C3 alkylene groups;R30 is selected from an optionally substituted C3-C10 carbocycle; thiourea; optionally substituted thiourea; urea; optionally substituted urea; sulfamide; alkyl sulfamide; acyl sulfamide, optionally substituted alkyl sulfamide; optionally substituted acyl sulfamide; sulfonamide; optionally substituted sulfonamide; guanidine, including alkyl and aryl guanidine; phosphoramide; or optionally substituted phosphoramide; or R30 is selected from azido, alkynyl, substituted alkynyl, -NH-C (O) -alkynyl, -NH-C (O) -alkynyl-R65; cyclooctyne; -NH-cyclooctyne, -NH-C (O) -cyclooctyne, or -NH- (cyclooctyne) 2; wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; andn20 is 2 to 26;(b) ～R20-R21- [O-CH2-CH2] n20-R22-NH-C (O) -R31      (XXXI)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond or C1-C3 alkylene groups;R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus;R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; andn20 is 2 to 26;(c) ～R20-R21- [O-CH2-CH2] n20-R22-C (O) NH-R31       (XXXII)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each , independently, a bond or C1-C3 alkylene groups;R31 is a branched polyethylene glycol chain, each branch, independently, having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus;R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle and optionally substituted heteroaryl; andn20 is 2 to 26;(d) ～R20-R21- [O-CH2-CH2] n20-R22-C (O) NR31-R22-NR24R25       (XXXIII)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R31 is H or R22-NR24R25;R21 and R22 are each, independently, a bond or C1-C3 alkylene groups;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group, provided that R24 and R25 are not both H; andn20 is 2 to 26;(e) ～R20-R21- [O-CH2-CH2] n20-R22-N (R33-R31) 2     (XXXIV)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond or C1-C3 alkylene groups;R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus;R33 is C1-C3 alkylene, C1-C3 alkylene-C (O) , -C (O) -C1-C3 alkylene, or -C (O) -C1-C3 alkylene-C (O) ;R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; andn20 is 2 to 26;(f) ～R20- (R21- [CH2-CH (OR34) -CH2-O] n20-R36) n25      (XXXV)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;each R21 is independently a bond, -O-or C1-C3 alkylene group;each R34 is independently H, - [CH2-CH (OH) -CH2-O] n20-R36, -C (O) -NR24R25 or -C (O) N (RN) -C1-C6alkylene-NR24R25;RN is H or C1-C4alkyl;R24 and R25 are each independently selected from a H; polyhydroxyl group; or substituted polyhydroxyl group, provided that both R24 and R25 are not H;each R36 is independently H, C1-C6alkylene-C (OH) H-NR44R45, C1-C6alkylene-C (OH) H-C1-C6alkylene-NR44R45, -C (O) -NR24R25, -C (O) N (RN) -C1-C6alkylene-NR24R25, C1-C6alkylene-C (O) NR24R25 or C1-C6alkylene-CO2R37;each R37 is independently H or C1-C6 alkyl;R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; and substituted -C (O) -polyhydroxyl group, provided that both R44 and R45 are not H;each n20 is independently 1 to 26; andn25 is 1 or 2;(g) ～R20-R21- [ [CH2-CH2-O] n20-R22- [CH2- [CH (OH) ] n23-CH2-O] n21] n22-R23-NR24-R25 (XXXVI)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21, R22 and R23 are each independently a bond or C1-C3 alkylene group;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; and substituted -C (O) -polyhydroxyl group, provided that R24 and R25 are not both H;each n20 is independently 0 to 26, and each n21 is independently 0 to 26, with the proviso that at least one of n20 or n21 is 2 to 26;n22 is 1 to 5;each n23 is independently 1 or 2;(h) ～R20- (R21- [O-CH2-CH2] n20-R22-N (RN) -CO2- [CH2-CH (OR34) -CH2-O] n21-R36) n25(XXXVII)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each independently a bond or C1-C3 alkylene groups;RN is H or C1-C4alkyl;R24 and R25 are each independently selected from a H; polyhydroxyl group; and substituted polyhydroxyl group, provided that both R24 and R25 are not H;each R34 is independently H, - [CH2-CH (OH) -CH2-O] n20-R36 or -C (O) N (RN) -C1-C6alkylene-NR24R25;each R36 is independently H, C1-C6alkylene-C (OH) H-NR44R45, C1-C6alkylene-C (OH) H-C1-C6alkylene-NR44R45, -C (O) N (RN) -C1-C6alkylene-NR24R25, C1-C6alkylene-C (O) NR24R25 or C1-C6alkylene-CO2R37;each R37 is independently H or C1-C6 alkyl;R44 and R45 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; and substituted -C (O) -polyhydroxyl group; provided that both R44 and R45 are not H;n20 is 2 to 26;n21 is 1 to 26; andn25 is 1 or 2;(i) ～R20- (R21- [N (RN) -C (O) - [O-CH2-CH (OH) -CH2] n20] n21-R22-NR24R25) n25(XXXVIII)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each independently a bond or C1-C3 alkylene groups;RN is H or C1-C4alkyl;R24 and R25 are each independently selected from a H; polyhydroxyl group; and substituted polyhydroxyl group, provided that R24 and R25 are not both H;n20 is 2 to 26;n21 is 1 to 4; andn25 is 1, 2 or 3;(j) ～R20- (R21- [C (Rα) H-C (O) -N (RN) ] n20-R22- [CH2-CH2-O] n20-NR24R25) n25(XXXIX)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond, C1-C3 alkylene, -C1-C3alkylene- [O-CH2-CH2-] n20, - [CH2-CH2-O] n20-C1-C3alkylene-or -C1-C3alkylene- [O-CH2-CH2-] n20-C (O) -;each Rα is independently H or -R22-NR24R25;each RN is independently H, C1-C6 alkyl or -R22-NR24R25;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted -C (O) -C1-C8 alkyl; a chelator; -C (O) -R28, wherein R28 is a Sugar unit of formula (XII) or (XIII) , provided that R24 and R25 are not both H;each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; andn25 is 1 or 2; or(k) ～R20-R21- [C (Rα) H-C (O) -N (RN) ] n20-R22- [CH2-CH2-O] n20-NR24R25|R21- [C (Rα) H-C (O) -N (RN) ] n21-R22- [CH2-CH2-O] n21-R23-CO2-R26(XXXVX)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21, R22 and R23 are each, independently, a bond, C1-C3 alkylene, -C1-C3alkylene- [O-CH2-CH2-] n20, - [CH2-CH2-O] n20-C1-C3alkylene-or -C1-C3alkylene- [O-CH2-CH2-] n20-C (O) -;each Rα is independently H or -R22-NR24R25;each RN is independently H, C1-C6 alkyl or -R22-NR24R25;R24 and R25 are each independently selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) , provided that R24 and R25 are not both H;R26 is H or C1-C6 alkyl;each n20 is independently 0 to 26, with the proviso that at least one n20 is 2 to 26; andeach n21 is independently 0 to 26, with the proviso that at least one n21 is 2 to 26.32.The Linker compound of any one of claims 1 to 6, comprising a Polar group having a formula selected from the following, or a stereoisomer or salt thereof: ～R20-R21- [O-CH2-CH2] n20-R22-NH-C (O) -R31   (XXXI) ,～R20-R21- [O-CH2-CH2] n20-R22-C (O) NH-R31  (XXXII) , and～R20-R21- [O-CH2-CH2] n20-R22-N- (R33-R31) 2   (XXXIII) ;wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R21 and R22 are each, independently, a bond or C1-C3 alkylene groups;R31 is a branched polyethylene glycol chain, each branch having 1 to 26 ethylene glycol subunits and each branch having an R35 at its terminus;R33 is C1-C3 alkylene, -C1-C3 alkylene-C (O) , -C (O) -C1-C3 alkylene or -C (O) -C1-C3 alkylene-C (O) ;R35 is azido, alkynyl, alkynyl-R65, cyclooctyne or cyclooctyne-R65, wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; the wavy (～) line indicates an attachment site to R20; and n20 is 2 to 26.33.The Linker compound of claim 31 or 32, comprising a Polar group formed from a precursor group selected from the following: wherein R65 is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocycle, optionally substituted aryl, optionally substituted heterocarbocycle or optionally substituted heteroaryl; and the wavy line is an attachment site to Rb, or to the enzyme-cleavable group.34.The Linker compound of any one of claims 31 to 33, wherein the attachment site to Rb, or to the enzyme-cleavable group is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl,  carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, and protected forms thereof.35.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula: ～R20- (R43-R41- [O-CH2-CH2] n40-R42-R43- (NR44R45) n41) n42     (XL)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R41 and R42 are each, independently, a bond or C1-C6 alkylene;each R43 is, independently, selected from a bond, C1-C12 alkylene, -OC1-C12 alkylene, -C (=O) -, -NRa-C1-C12 alkylene, -C1-C12 alkylene-NRa-, -C (O) -C1-C12 alkylene, -C1-C12 alkylene-C (O) -, -NRa-C1-C12 alkylene-C (O) -, -C (O) -C1-C12 alkylene-NRa-, -NRa-C (O) -NRa-, -NRa-C (O) -, -NRa-C (O) -C1-C12 alkylene, -C (O) -NRa-C1-C12 alkylene, -heteroarylene, heteroaryl-C1-C12 alkylene, heteroaryl-C1-C12 alkylene-C (O) -, or -C (O) NR46R47, wherein each alkylene is optionally substituted with hydroxyl, SO3H and / or oxo, Ra is H, C1-C6 alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group, and one of R46 and R47 is H or C1-C12 alkylene and the other is C1-C12 alkylene, wherein one of the C1-C2 alkylenes is bound to NR44R45 at the nitrogen atom;R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C (O) -polyhydroxyl group, or substituted -C (O) -polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate; n40 is 2 to 26, provided that R44 and R45 are not both H;n40 is 2 to 26;n41 is 1 to 6; andn42 is 1 to 6.36.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula: ～R20- (R41- [O-CH2-CH2] n40-R42-R43- (NR44R45) n41) n42      (XLI)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R41 and R42 are each, independently, a bond or C1-C6 alkylene;R43 is selected from a bond, C1-C12 alkylene, -OC1-C12 alkylene, -C (=O) -, -NRa-C1-C12 alkylene, -C1-C12 alkylene-NRa-, -C (O) -C1-C12 alkylene, -C1-C12 alkylene-C (O) -, -NRa-C1-C12 alkylene-C (O) -, -C (O) -C1-C12 alkylene-NRa-, -NRa-C (O) -NRa-, -NRa-C (O) -, -NRa-C (O) -C1-C12 alkylene, C (O) -NRa-C1-C12 alkylene, -heteroarylene, heteroaryl-C1-C12 alkylene, heteroaryl-C1-C12 alkylene-C (O) -, and -C (O) NR46R47, wherein each alkylene is optionally substituted with hydroxyl, SO3H and / or oxo, Ra is H, C1-C6 alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group and one of R46 and R47 is H or C1-C12 alkylene and the other is C1-C12 alkylene, wherein one of the C1-C2 alkylenes is bound to NR44R45 at the nitrogen atom;R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C (O) -polyhydroxyl group, or substituted -C (O) -polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H;n40 is 1 to 26;n41 is 1 to 6; andn42 is 1 to 6.37.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula: ～R20- (R41- [O-CH2-CH2] n40-R42-R43- (NR44R45) n41) n42      (XLII)or a stereoisomer or salt thereof, wherein:R20 is an attachment group to site Rb, or to the enzyme-cleavable group;R41 and R42 are each, independently, a bond or C1-C3 alkylene;R43 is selected from a bond, C1-C6 alkylene, -OC1-C12 alkylene, -C (=O) -, -NRa -C1-C12 alkylene, -C1-C6 alkylene-NRa-, -C (O) -C1-C6 alkylene, -C1-C6 alkylene-C (O) -, -NRa-C1-C6 alkylene-C (O) -, -C (O) -C1-C6 alkylene-NRa-, -NRa-C (O) -NRa-, -NRa-C (O) -, -NRa-C (O) -C1-C6 alkylene, -C (O) -NRa-C1-C12 alkylene, -heteroarylene, heteroaryl-C1-C6 alkylene, heteroaryl-C1-C6 alkylene-C (O) -, and -C (O) NR46R47, wherein each alkylene is optionally substituted with hydroxyl, SO3H, and / or oxo, Ra is H, C1-C6 alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group and one of R46 and R47 is H or C1-C6 alkylene and the other is C1-C12 alkylene, wherein one of the C1-C2 alkylenes is bound to NR44R45 at the nitrogen atom;R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C (O) -polyhydroxyl group, or substituted -C (O) -polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H;n40 is 1 to 16;n41 is 1 to 4; andn42 is 1 to 4.38.The Linker compound of any one of claims 7, 31, 32, and 35-37, wherein R20 is formed from a functional group of a precursor compound of the Polar group, said functional group selected from halo, aldehyde, carboxyl, amino, alkynyl, azido, hydroxyl, carbonyl, carbamate, thiol, urea, thiocarbamate, thiourea, sulfonamide, acyl sulfonamide, alkyl sulfonate, triazole, azadibenzocyclooctyne, hydrazine, carbonylalkylheteroaryl, or protected forms thereof.39.The Linker compound of any one of claims 7, 31, 32, and 35-37, wherein R20 comprises one of the following structures: or a stereoisomer thereof, wherein R is H, C1-C6 alkyl or polyhydroxyl group, n is 0 to 12, theindicates an attachment site to Rb, or to the enzyme-cleavable group, and theindicates an attachment site to a remainder portion of the Polar group.40.The compound of any one of claims 7, 31, 32, and 35-37, wherein R20 has one of the following structures: or a stereoisomer thereof, wherein n = 0 to 12, theindicates an attachment site to Rb, or to the enzyme-cleavable group, and theindicates an attachment site to a remainder portion of the Polar group.41.The Linker compound of any one of claims 35-40, wherein R43- (NR44R45) n41 has one of the following structures: or a stereoisomer thereof, wherein Ra is H, C1-C6 alkyl, a polyhydroxyl group, or a substituted polyhydroxyl group; p is an integer from 1 to 6, and theindicates the attachment site of R43 to the remainder of the Polar group.42.The Linker compound of anyone of claims 35-40, wherein R43- (NR44R45) n41 has one of the following structures: or a stereoisomer thereof, wherein theindicates the attachment site of R43 to the remainder of the Polar group.43.The Linker compound of any one of claims 35-42, wherein -NR44R45 has one of the following structures: or a stereoisomer thereof, wherein theindicates the attachment site of -NR44R45 to the remainder of the Polar group.44.The Linker compound of any one of claims 1-44, comprising a Polar group having one of the following structures prior to attachment to the Linker Unit: wherein:(*) indicates the attachment site to site Rb, or to the enzyme-cleavable group;each R is independently H or C1-C6 alkyl;R’ is H, C1-C6 alkyl, -N (R24) (R25) or -CO2H;each n is independently 1 to 12;X is O, NR or -CH2-;V is bond or C1-C6 alkyl;one of R24 and R25 is selected from a H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted -C (O) -C1-C8 alkyl; a chelator; and -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) ; and the other of R24 and R25 is selected from H; polyhydroxyl group; substituted polyhydroxyl group; -C (O) -polyhydroxyl group; substituted -C (O) -polyhydroxyl group; substituted -C (O) -C1-C8 alkyl; a chelator; -C (O) -R28, where R28 is a Sugar unit of formula (XII) or (XIII) ; and polyethylene glycol, optionally having 1 to 24 ethylene glycol subunits, provided that R24 and R25 are not both H.45.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula selected from:(a) ～R40- (R43-R41- [O-CH2-CH2] n40-R46- [O-CH2-CH2] n40-R42-R43- (NR44R45) n41) n42(XLIII)or a stereoisomer or salt thereof, wherein:R40 is an attachment group to site Rb, or to the enzyme-cleavable group;R41 and R42 are each, independently, a bond or C1-C6 alkylene;each R43 is, independently, selected from a bond, C1-C12 alkylene, -OC1-C12 alkylene, -C (=O) -, -NH-C1-C12 alkylene, -C1-C12 alkylene-NH-, -C (O) -C1-C12 alkylene, -C1-C12 alkylene-C (O) -, -NH-C1-C12 alkylene-C (O) -, -C (O) -C1-C12 alkylene-NH-, -NH-C (O) -NH-, -NH-C (O) -, -NH-C (O) -C1-C12 alkylene, -C (O) -NH-C1-C12 alkylene, C1-C12alkylene-NH-C (O) -, -heteroarylene, heteroaryl-C1-C12 alkylene, heteroaryl-C1-C12 alkylene-C (O) -, or -C (O) NR46R47, wherein one of R46 and R47 is H or C1-C12 alkylene and the other is C1-C12 alkylene;R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C (O) -polyhydroxyl group, or substituted -C (O) -polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H;each R46 is independently selected from -NR50-, -NR50-C1-C6alkylene-NR50-, -NR50-C (O) -NR50-S (O) 2-NR50-or -NR50-C (O) -C1-6alkylene-;each R50 is independently selected from H, C1-C6 alkyl, or polyhydroxyl group;each n40 is independently 2 to 26;n41 is 1 to 6; andn42 is 1 to 6;(b) ～R40- (R51- [O-CH2-CH2] n43-R52-X1-R55-X2-R53- [O-CH2-CH2] n43-R54- [X3-R56] n44-R57) n45(XLIV)or a stereoisomer or salt thereof, wherein:R40 is an attachment group to site Rb, or to the enzyme-cleavable group;R51, R52, R53 and R54 are each, independently, a bond or C1-C6 alkylene;X1, X2 and X3 are each independently -NRN-C (O) -or -C (O) -NRN-;each RN independently represent H, C1-C6 alkyl, or polyhydroxyl group;R55 and R56 each independently represent a bivalent polyhydroxyl group;R57 is H, OH or C1-C6 alkyl;each n43 is independently 0 to 26, with the proviso that at least one n43 is 1 to 26;n44 is 0 to 10; andn45 is 1 or 2; or(c) ～R40-R51- [O-CH2-CH2] n43-R52-N- (R53-X1-R54- [O-CH2-CH2] n43- (NR44R45) ) 2(XLV)or a stereoisomer or salt thereof, wherein:R40 is an attachment group to site Rb, or to the enzyme-cleavable group;R51, R53 and R54 are each, independently, abond or optionally-substituted C1-C6 alkylene;R52 is a bond, C1-C6 alkylene, -C (O) -or -O-C (O) -;each X1 is independently -NRN-C (O) -or -C (O) -NRN-;each RN independently represent H, C1-C6 alkyl, or polyhydroxyl group;R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C (O) -polyhydroxyl group, or substituted -C (O) -polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; andeach n43 is independently 2 to 26.46.The Linker compound of claim 45, comprising a Polar group having one of the following structures prior to attachment to the enzyme-cleavable group and / or to the Linker Unit: wherein:(*) indicates the attachment site to site Rb, or to the enzyme-cleavable group;each R is independently H, alkyl or polyhydroxyl group;R44 and R45 are each, independently, H, polyhydroxyl group, substituted polyhydroxyl group, -C (O) -polyhydroxyl group, or substituted -C (O) -polyhydroxyl group, wherein optional substituents are selected from sulfate, phosphate, alkyl sulfate, and alkyl phosphate, provided that R44 and R45 are not both H; andeach n is independently 1 to 12.47.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula selected from: or a stereoisomer or salt thereof, wherein:each Y is independently R76 oreach R76 is independently H, acetyl, -P (=O) (OH) 2, or - (CH2) v-O-S (=O) 2 (OH) ;each Ra and Rb is independently H or Ra and Rb are taken together with the carbon to which they are attached to form an oxo group;each q is independently 2-26;each m is independently 1 to 4;each n is independently 1 to 4;each v is independently 1 to 6; andeach *is an attachment site to Rb, or to the enzyme-cleavable group.48.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula selected from: or a stereoisomer or salt thereof, wherein:each R76 is independently H, acetyl, -P (=O) (OH) 2, or - (CH2) vS (=O) 2 (OH) ;each q is independently 2-26;each m is independently 1 to 4;each n is independently 1 to 4;each v is independently 1 to 6; andeach *is an attachment site to Rb, or to the enzyme-cleavable group.49.The Linker compound of any one of claims 1-6, comprising a Polar group having a formula selected from: or a stereoisomer or salt thereof, wherein:each q is independently 2-26;each m is independently 1 to 4;each n is independently 1 to 4; andeach *is an attachment site to Rb, or to the enzyme-cleavable group.50.The Linker compound of claim 47, wherein Y is R76.51.The Linker compound of claim 47, wherein Y is 52.The Linker compound of claim 47, wherein each Ra and Rb is independently H.53.The Linker compound of claim 47, wherein Ra and Rb are taken together with the carbon to which they are attached to form an oxo group.54.The Linker compound of any one of claims 45-47, wherein q is 10-20.55.The Linker compound of any one of claims 57-49, wherein q is 12.56.The Linker compound of any one of claims 1-6, 35-37, or 47-49, comprising a Polar group selected from the following, or a stereoisomer or salt thereof: wherein each Z is attached at *and is individually selected from:wherein eachis an attachment site to Rb, or to the enzyme-cleavable group.57.The Linker compound of any one of claims 1 to 6, wherein the Polar group comprises at least one Carboxyl unit having the following formula: or a stereoisomer or salt thereof, wherein:(a)L70 is selected from C1-C8 alkylene, C1-C8 alkylene-C (O) -, -C (O) -C1-C8 alkylene-, and -C (O) -C1-C8 alkylene-C (O) -, and *is an attachment site to Rb, to the enzyme-cleavable group, or to a remainder of the Polar group;R70 is ～NR71 (R72-R73) , wherein R71 is selected from H, C1-C12 alkyl, substituted C1-C12 alkyl, or polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits) , R72 is a bond or is selected from optionally substituted C1-C3 alkylene, optionally substituted ether, optionally substituted thioether, optionally substituted ketone, optionally substituted amide, polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits) , optionally substituted carbocycle, optionally substituted aryl or optionally substituted heteroaryl, and R73 is a carboxyl or polycarboxyl, wherein polycarboxyl comprises 1 to 10, or 1 to 6, or 1 to 4 carboxyl groups, wherein the carboxyl groups are interconnected by alkyl, alkylene, substituted alkyl, substituted alkylene, heteroalkyl, heteroalkylene, amino and / or amide; or(b)L70 is selected from C1-C8 alkylene, C1-C8 alkylene-C (O) -, -C (O) -C1-C8 alkylene-, and -C (O) -C1-C8 alkylene-C (O) -, and *is an attachment site to Rb, to the enzyme-cleavable group, or to a remainder of the Polar group;R70 is ～NR71 (R75- (R73) 2) , wherein R71 is selected from H, C1-C12 alkyl, substituted C1-C12 alkyl, or polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits) , R75 is a branched optionally substituted C1-C3 alkylene, optionally substituted ether, optionally substituted thioether, optionally substituted ketone, optionally substituted amide, polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits) , optionally substituted carbocycle, optionally substituted aryl or optionally substituted heteroaryl and each R73 is independently carboxyl or polycarboxyl, wherein polycarboxyl comprises 1 to 10, or 1 to 6, or 1 to 4 carboxyl groups, wherein the carboxyl groups are interconnected by alkyl, alkylene, substituted alkyl, substituted alkylene, heteroalkyl, heteroalkylene, amino and / or amide; or(c)L70 is selected from C1-C8 alkylene, C1-C8 alkylene-C (O) -, -C (O) -C1-C8 alkylene-, and -C (O) -C1-C8 alkylene-C (O) -, and *is an attachment site to Rb, to the enzyme-cleavable group, or to a remainder of the Polar group;R70 is ～N (R74-R73) (R72-R73) , wherein R72 and R74 are each independently selected from optionally substituted C1-C3 alkylene, optionally substituted ether, optionally substituted thioether, optionally substituted ketone, optionally substituted amide, polyethylene glycol (optionally having 1 to 12 ethylene glycol subunits) , optionally substituted carbocycle, optionally substituted aryl or optionally substituted heteroaryl, and each R73 is independently carboxyl or polycarboxyl, wherein the polycarboxyl comprises 1 to 10, or 1 to 6, or 1 to 4 carboxyl groups, wherein the carboxyl groups are interconnected by alkyl, alkylene, substituted alkyl, substituted alkylene, heteroalkyl, heteroalkylene, amino and / or amide.58.The Linker compound of any one of claims 1 to 57, comprising a Polar group including the Polymer unit and a Sugar unit.59.The Linker compound of any o one f claims 1 to 57, comprising a Polar group including at least two Polymer units.60.The Linker compound of any one of claims 1 to 57, comprising a Polar group including the Polymer unit and a Carboxyl unit.61.The Linker compound of any one of claims 1 to 57, comprising at least two Polar groups.62.The Linker compound of any one of claims 1 to 57, comprising a Polar group including the Polymer unit, the Sugar unit and the Carboxyl unit.63.The Linker compound of any one of claims 1 to 57, comprising a Polar group including at least two Polymer units, at least one Sugar unit and at least one Carboxyl unit.64.The Linker compound of any one of claims 1 to 57, wherein the enzyme-cleavable group comprises at least two amino acid units.65.The Linker compound of any one of claims 1 to 64, comprising at least one of the Polar group attached to the enzyme-cleavable group.66.The Linker compound of any one of claims 1-64, having one of the following structures: whereinRc is a bond or C1-6 alkylene;the wavy line on the amino group indicates an attachment site for a Stretcher group or, prior to attachment to the Stretcher group, indicates H;β-is the attachment site to the at least one Polar group; andthe benzylic H on the benzylic OH is optionally replaced with a bond to at least one of the Drug units or to the linking group attached to at least one of the Drug units.67.The Linker compound of any one of claims 1-66, wherein the enzyme-cleavable group comprises a peptide that is cleavable by an intracellular protease.68.The Linker compound of claim 67, wherein the intracellular protease is Cathepsin B.69.The Linker compound of claim 68, wherein the enzyme-cleavable group comprises a cleavable peptide including a valine-citrulline peptide, a valine-alanine peptide, a valine-lysine peptide, a phenylalanine-lysine peptide, or a glycine-glycine-phenylalanine-glycine peptide.70.The Linker compound of any one of claims 67-69, comprising one of the following structures: whereinRc is a bond or C1-6 alkylene;the wavy line on the amino group indicates an attachment site for the Stretcher group; or, prior to attachment to the Stretcher group, indicates H;β-is the attachment site to the at least one Polar group; andthe H on the benzylic OH is optionally replaced with a bond to at least one of the Drug units or to the attachment site to at least one of the Drug units.71.The Linker compound of any one of claims 1-5, having one of the following structures: wherein the wavy line on the amino group indicates an attachment site to the Stretcher group; or, prior to attachment to the Stretcher group, indicates H; and the H on the benzylic OH is optionally replaced with a bond to at least one of the Drug units or a linking group attached to the at least one of the Drug units.72.The Linker compound of any one of claims 1 to 69, wherein the enzyme-cleavable group is joined to the Stretcher group by a non-peptidic linking group.73.The Linker compound of claim 72, wherein the non-peptidic linking group is selected from optionally-substituted C1-C10 alkylene, optionally-substituted C2-C10 alkenylene, optionally-substituted C2-C10 alkynylene, or optionally-substituted polyethylene glycol.74.The Linker compound of any one of claims 1-73, comprising the Stretcher group attached to the enzyme-cleavable group.75.The Linker compound of claim 74, wherein the Stretcher group is selected from the following: wherein R17 is -C1-C10 alkylene-, -C1-C10 heteroalkylene-, -C3-C8 carbocyclo-, -O- (C1-C8 alkylene) -, - (CH2-O-CH2) b-C1-C8 alkylene- (where b is 1 to 26) , -C1-C8 alkylene- (CH2-O-CH2) b- (where b is 1 to 26) , -C1-C8 alkylene- (CH2-O-CH2) b-C1-C8 alkylene- (where b is 1 to 26) , -arylene-, -C1-C10 alkylene-arylene-, -arylene-C1-C10 alkylene-, -C1-C10 alkylene- (C3-C8 carbocyclo) -, - (C3-C8 carbocyclo) -C1-C10 alkylene-, -C3-C8 heterocyclo-, -C1-C10 alkylene- (C3-C8 heterocyclo) -, - (C3-C8 heterocyclo) -C1-C10 alkylene-, -C1-C10 alkylene-C (=O) -, -C1-C10alkylene-C (O) NH-C1-C8alkylene- [O-CH2-CH2] n-C (O) - (where n is 1 to 26) , C1-C10 heteroalkylene-C (=O) -, -C1-C8 alkylene- (CH2-O-CH2) b-C (=O) - (where b is 1 to 26) , - (CH2-O-CH2) b-C1-C8 alkylene-C (=O) - (where b is 1 to 26) , -C1-C8 alkylene- (CH2-O-CH2) b-C1-C8 alkylene-C (=O) - (where b is 1 to 26) , -C3-C8 carbocyclo-C (=O) -, -O- (C1-C8 alkyl) -C (=O) -, -arylene-C (=O) -, -C1-C10 alkylene-arylene-C (=O) -, -arylene-C1-C10 alkylene-C (=O) -, -C1-C10 alkylene- (C3-C8 carbocyclo) -C (=O) -, - (C3-C8 carbocyclo) -C1-C10 alkylene-C (=O) -, -C3-C8 heterocyclo-C (=O) -, -C1-C10 alkylene- (C3-C8 heterocyclo) -C (=O) -, - (C3-C8 heterocyclo) -C1-C10 alkylene-C (=O) -, -C1-C10 alkylene-NH-, -C1-C10 heteroalkylene-NH-, -C1-C8 alkylene- (CH2-O-CH2) b-NH- (where b is 1 to 26) , - (CH2-O-CH2) b-C1-C8 alkylene-NH- (where b is 1 to 26) , -C1-C8 alkylene- (CH2-O-CH2) b-C1-C8 alkylene-NH- (where b is 1 to 26) , -C1-C8 alkylene- (C (=O) ) -NH- (CH2-O-CH2) b-C (=O) - (where b is 1 to 26) , -C1-C8 alkylene- (C (=O) ) -NH- (CH2-O-CH2) b-C1-C8 alkylene-C (=O) - (where b is 1 to 26) , -C1-C8 alkylene-NH- (C (=O) ) - (CH2-O-CH2) b-NH- (where b is 1 to 26) , -C1-C8 alkylene-NH- (C (=O) ) - (CH2-O-CH2) b-C1-C8 alkylene-NH- (where b is 1 to 26) , -C3-C8 carbocyclo-NH-, -O- (C1-C8 alkyl) -NH-, -arylene-NH-, -C1-C10 alkylene-arylene-NH-, -arylene-C1-C10 alkylene-NH-, -C1-C10 alkylene- (C3-C8 carbocyclo) -NH-, - (C3-C8 carbocyclo) -C1-C10 alkylene-NH-, -C3-C8 heterocyclo-NH-, -C1-C10 alkylene- (C3-C8 heterocyclo) -NH-, - (C3-C8 heterocyclo) -C1-C10 alkylene-NH-, -C1-C10 alkylene-S-, C1-C10 heteroalkylene-S-, -C3-C8 carbocyclo-S-, -O- (C1-C8 alkyl) -S-, -arylene-S-, -C1-C10 alkylene-arylene-S-, -arylene-C1-C10 alkylene-S-, -C1-C10 alkylene- (C3-C8 carbocyclo) -S-, - (C3-C8 carbocyclo) -C1-C10 alkylene-S-, -C3-C8 heterocyclo-S-, -C1-C10 alkylene- (C3-C8 heterocyclo) -S-, or - (C3-C8 heterocyclo) -C1-C10 alkylene-S-; orwherein the Stretcher group comprises maleimido (C1-C10alkylene-C (O) -, maleimido (CH2OCH2) p2 (C1-C10alkyene) C (O) -, maleimido (C1-C10alkyene) (CH2OCH2) p2C (O) -, or a ring open form thereof, wherein p2 is from 1 to 26;and wherein *is an attachment site to the Targeting group, and the wavy line is an attachment site to the enzyme-cleavable group.76.The Linker compound of claim 74, wherein the Stretcher group is selected from the following: wherein the wavy lineindicates an attachment site of the Stretcher group to the enzyme-cleavable group, and the attachment site to the Targeting group is on the maleimide, primary amine or alkyne functional group.77.The Linker compound of claim 1, having one of the following structures: wherein the H on the benzylic OH is optionally replaced with a bond to the at least one Drug unit or to the linking group attached to the at least one Drug unit.78.A Drug-Linker compound, comprising a Linker compound of any one of the claims 1-77 attached to the at least one Drug unit, or attached to the linking group attached to the at least one Drug unit, at the attachment site.79.The Drug-Linker of claim 78, wherein the Drug unit is selected from a cytotoxic agent, an immune modulatory agent, a nucleic acid, a growth inhibitory agent, a PROTAC, a toxin, a radioactive isotope, and a chelating ligand.80.The Drug-Linker of claim 79, wherein the Drug unit is a cytotoxic agent.81.The Drug-Linker of claim 80, wherein the cytotoxic agent is selected from the group consisting of an auristatin, a maytansinoid, a camptothecin, a duocarmycin, and a calicheamicin.82.The Drug-Linker of claim 81, wherein the cytotoxic agent is an auristatin.83.The Drug-Linker of claim 82, wherein the cytotoxic agent is MMAE or MMAF.84.The Drug-Linker of claim 81, wherein the cytotoxic agent is a camptothecin.85.The Drug-Linker of claim 84, wherein the cytotoxic agent is exatecan, or SN-38, or DxD.86.The Drug-Linker of claim 85, wherein the cytotoxic agent is RS-exatecan or SS-exatecan.87.The Drug-Linker of claim 81, wherein the cytotoxic agent is a calicheamicin.88.The Drug-Linker of claim 81, wherein the cytotoxic agent is a maytansinoid.89.The Drug-Linker of claim 88, wherein the maytansinoid is maytansine, maytansinol, or ansamatocin-2.90.The Drug-Linker of claim 79, wherein the Drug unit is an immune modulatory agent.91.The Drug-Linker of claim 90, wherein the immune modulatory agent is selected from a TRL7 agonist, a TLR8 agonist, a STING agonist, or a RIG-I agonist.92.The Drug-Linker of claim 91, wherein the immune modulatory agent is an TLR7 agonist.93.The Drug-Linker of claim 92, wherein the TLR7 agonist is an imidazoquinoline, an imidazoquinoline amine, a thiazoquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3, 2-d]pyrimidine-2, 4-diamine, pyrimidine-2, 4-diamine, 2-aminoimidazole, 1-alkyl-1 H-benzimidazol-2-amine, tetrahydropyridopyrimidine, heteroarothiadiazide-2, 2-dioxide, a benzonaphthyridine, a guanosine analog, an adenosine analog, a thymidine homopolymer, ssRNA, CpG-A, PolyG10, or PolyG3.94.The Drug-Linker of claim 91, wherein the immune modulatory agent is a TLR8 agonist.95.The Drug-Linker of claim 94, wherein the TLR8 agonist is selected from an imidazoquinoline, a thiazoloquinoline, an aminoquinoline, an aminoquinazoline, a pyrido [3, 2-d] pyrimidine-2, 4-diamine, pyrimidine-2, 4-diamine, 2-aminoimidazole, 1-alkyl-1 H-benzimidazol-2-amine, tetrahydropyridopyrimidine, or a ssRNA.96.The Drug-Linker of claim 91, wherein the immune modulatory agent is a STING agonist.97.The Drug-Linker of claim 91, wherein the immune modulatory agent is a RIG-I agonist.98.The Drug-Linker of claim 97, wherein the RIG-I agonist is selected from KIN1148, SB-9200, KIN700, KIN600, KIN500, KIN100, KIN101, KIN400, and KIN2000.99.The Drug-Linker of claim 79, wherein the Drug unit is a chelating ligand.100.The Drug-Linker of claim 99, wherein the chelating ligand is selected from platinum (Pt) , ruthenium (Ru) , rhodium (Rh) , gold (Au) , silver (Ag) , copper (Cu) , molybdenum (Mo) , titanium (Ti) , or iridum (Ir) ; a radioisotope such as yittrium-88, yittrium-90, technetium-99, copper-67, rhenium-188, rhenium-186, galium-66, galium-67, indium-111, indium-114, indium-115, lutetium-177, strontium-89, sararium-153, and lead-212.101.The Drug-Linker of claim 78, having one of the following structures: 102.A conjugate comprising a Targeting group attached to the Drug-linker of any one of claims 78 to 101, wherein the Targeting group specifically binds to the target molecule.103.The conjugate of claim 102, wherein the Targeting group is selected from an antibody or an antigen-binding portion thereof.104.The conjugate of claim 103, wherein the Targeting group is a monoclonal antibody, a Fab, a Fab’, an F (ab’) , an Fv, a disulfide linked Fc, a scFv, a single domain antibody, a diabody, a bi-specific antibody, or a multi-specific antibody.105.The conjugate of claim 102, wherein the Targeting group is a diabody, a DART, an anticalin, an affibody, an avimer, a DARPin, or an adnectin.106.The conjugate of any one of claims 102 to 105, wherein the Targeting group is mono-specific.107.The conjugate of any one of claims 102 to 106, wherein the Targeting group is bivalent.108.The conjugate of any one of claims 102 to 105, wherein the Targeting group is bispecific.109.The conjugate of any one of claims 102 to 108, wherein the average drug loading (pload) of the conjugate is from about 1 to about 8, about 2, about 4, about 6, about 8, about 10, about 12, about 14, about 16, about 3 to about 5, about 6 to about 8, or about 8 to about 16.110.The conjugate of any one of claims 102-109, selected from the following: wherein Ab is a Targeting group and n is pload.111.The conjugate of any one of claims 102-110, wherein the target molecule is CD19, CD20, CD30, CD33, CD70, LIV-1, EGFRv3, or HER2.112.The conjugate of any one of claims 102-111, wherein the target molecule is a cancer associated antigen.113.The conjugate of any one of claims 102-111, wherein the target molecule is CD19, CD20, CD30, CD33, CD38, CA125, HER2, MUC-1, prostate-specific membrane antigen (PSMA) , CD44 surface adhesion molecule, mesothelin (MLSN) , carcinoembryonic antigen (CEA) , epidermal growth factor receptor (EGFR) , EGFRvIII, vascular endothelial growth factor receptor-2 (VEGFR2) , high molecular weight-melanoma associated antigen (HMW-MAA) , MAGE-A1, IL-13R-a2, GD2, 1p19q, HER2, ABL1, AKT1, ALK, APC, AR, ATM, BRAF, BRCA1, BRCA2, cKIT, cMET, CSF1R, CTNNB1, FGFR1, FGFR2, FLT3, GNA11, GNAQ, GNAS, HRAS, IDH1, IDH2, JAK2, KDR (VEGFR2) , KRAS, MGMT, MGMT-Me, MLH1, MPL, NOTCH1, NRAS, PDGFRA, Pgp, PIK3CA, PR, PTEN, RET, RRM1, SMO, SPARC, TLE3, TOP2A, TOPO1, TP53, TS, TUBB3, VHL, CDH1, ERBB4, FBXW7, HNF1A, JAK3, NPM1, PTPN11, RB1, SMAD4, SMARCB1, STK1, MLH1, MSH2, MSH6, PMS2, ROS1, ERCC1, 5T4 (TPBG) , B7-H3, CCR7, CD105, CD22, CD46, CD47, CD56, CD70, CD71, CD79b, CDH6, CLDN6, CLDN18.2, CLEC12A, DLL3, DR5, ERBB3 (HER3) , EPCAM, FOLR1, IGF1R, IL2RA (CD25) , IL3RA, ITGB6, LIV-1, LRRC15, mesothelin (MSLN) , NaPi2b (SLC34A2) , nectin-4, PTK7, ROR1, SEZ6, SLC44A4, SLITRK6, Tissue Factor (TF) , TROP2, or B7-H4.114.The conjugate of any one of claims 102-104, wherein the Targeting group is an antibody, or fragment thereof, comprising rituximab trastuzumab pertuzumab  bevacizumab ranibizumab cetuximab alemtuzumab  panitumumab ibritumomab tiuxetan tositumomab ipilimumab, zalutumumab, dalotuzumab, figitumumab, ramucirumab, galiximab, farletuzumab, ocrelizumab, ofatumumab tositumumab, ibritumomab, the CD20 antibodies 2F2 (HuMax-CD20) , 7D8, IgM2C6, IgG1 2C6, 11B8, B1, 2H7, LT20, 1FS or AT80, daclizumab or anti-LHRH receptor antibodies including clone A9E4, F1G4, AT2G7, GNRH03, or GNRHR2.115.A pharmaceutical composition comprising the conjugate of any one of claims 102 to 114 and a pharmaceutically acceptable carrier.116.A method of treating a subject in need thereof, comprising administering to the subject a conjugate of any one of claims 102 to 114 or the pharmaceutical composition of claim 115, wherein the subject has cancer or an autoimmune disease and the conjugate binds to the target antigen associated with the cancer or autoimmune disease.117.A Drug-Linker compound, represented by the structure of Formula (A) or a salt thereof, wherein:(i) β is R20 (-R21- [O-CH2-CH2] n20-R22-NR24R25) z; whereinR20 is NH, R21 and R22 are each, independently, a bond or C1-C3 alkylene;R24 and R25 are each independently selected from H; polyhydroxyl group; and -C (O) -polyhydroxyl group; provided that R24 and R25 are not both H; z is 1, or 2;andn20 is 2 to 26;(ii) Ra is H or C1-C6 alkyl;(iii) Rc is a bond, -C (O) -, -S (O) -, -SO2-, C1-6 alkylene, C1-6 alkynylene, or C1-6 alkynylene-triazolyl;(iv) R1 is a bond, -C (O) -, or C1-6 alkylene; and(v) δ is selected from a Drug;(vi) α is represented bywhereinR2 is a peptide having 2-5 amino acids;R3 is -C1-C10 alkylene-C (=O) -, -C1-C10 alkylene-, -C1-C10alkylene-C (O) NH-C1-C8alkylene- [O-CH2-CH2] n-C (O) - (where n is 1 to 26) , or -C1-C8 alkylene- (CH2-O-CH2) b-C (=O) - (where b is 1 to 26) .118.The Drug-Linker compound of claim 117, wherein R20 is 119.The Drug-Linker compound of claim 117, wherein β is and n20 is 4 to 12.120.The Drug-Linker compound of claim 117, wherein β is 121.The Drug-Linker compound of any one of claims 117 to 120, wherein R2 is selected from: 122.The Drug-Linker compound of any one of claims 117 to 121, wherein R2 is selected from: 123.The Drug-Linker compound of any one of claims 117 to 122, wherein R3 is selected from: 124.The Drug-Linker compound of any one of claims 117 to 123, wherein R3 is selected from: 125.The Drug-Linker compound of any one of claims 117 to 124, wherein Rc is -C (O) -.126.The Drug-Linker compound of any one of claims 117 to 125, wherein R1 is -C (O) -.127.The Drug-Linker compound of any one of claims 117 to 126, wherein the Drug is selected from a cytotoxic agent.128.The Drug-Linker compound of any one of claims 117 to 126, wherein the Drug is MMAE or MMAF.129.The Drug-Linker compound of any one of claims 117 to 126, wherein the Drug is MMAE.130.The Drug-Linker compound of any one of claims 117 to 126, wherein the Drug is exatecan.131.The Drug-Linker compound of any one of claims 117 to 126, wherein the Drug is selected from an immune modulatory agent.132.The Drug-Linker compound of any one of claims 117 to 126, wherein δ is selected from 133.The Drug-Linker compound of any one of claims 117 to 126, wherein δ is 134.The Drug-Linker compound of any one of claims 117 to 126, wherein δ is from 135.A conjugate comprising a Targeting group attached to the Drug-linker of any one of claims 117 to 134, wherein the Targeting group specifically binds to the target molecule.136.The conjugate of claim 135, wherein the ratio of Drug-Linker to Targeting group is represented by a DAR value, wherein the DAR value is from 1 to 8.