Antibody-drug conjugate metabolites

Abstract

Antibodies and antigen-binding fragments thereof for binding to antibody-drug conjugates (ADCs) or metabolites thereof are disclosed. The disclosure further relates to methods for measuring antibody-drug conjugates (ADCs) and metabolites thereof, e.g., by using the antibodies or antigen-binding fragments disclosed herein.

Description

Attorney Docket No.15648.0054-00304 ANTIBODY-DRUG CONJUGATE METABOLITES

[0001] This application claims the benefit of U.S. Provisional Application No.63 / 590,288, filed on October 13, 2023, the contents of which are incorporated by reference in their entirety.

[0002] The present disclosure relates to methods of analysis of antibody-drug conjugates (ADCs), e.g., those comprising eribulin, and the quantitative assessment of intact ADC or metabolites thereof in vitro and in vivo. Antibodies and antigen-binding fragments thereof suitable for use in the assays are also disclosed. BACKGROUND

[0003] When analyzing ADCs, for example to provide quantitative assessment of ADC concentration and metabolism in vitro or in vivo, the typical assays performed involve assessing total antibody (both conjugated and unconjugated antibody), intact ADC (all conjugated antibody species with drug-to-antibody ratio (DAR) > 0, generally measured in a DAR-insensitive manner), and free payload. Assessment of total antibody and intact ADC are almost exclusively determined using immunoassay methods, while free payload is typically measured by quantitative mass spectrometry. While providing valuable information on components of ADC metabolism, these assays often do not provide a complete picture of the overall metabolic process. Intact ADC assays are typically DAR-insensitive, i.e., all DAR species are recovered equally, which simplifies the interpretation of pharmacokinetic analyses by reducing the complexity of test agent to a single species – conjugated antibody. However, intact ADC assays can overrepresent ADC stability, especially for ADCs with higher starting DAR (e.g., DAR4 to DAR8 or higher). These ADCs could lose all but one of their conjugated payloads or linker-payloads to chemical or enzymatic processes and still be quantitated in the intact ADC assay as “intact.” Furthermore, other biologically active payload-containing metabolites could be generated in the process of ADC metabolism, and these would not be captured solely with a free payload assay. Thus, a need remains for improved ADC analytical assays.

[0004] One option for improved assays could comprise immunological methods. The measurement of intact ADC by immunological methods, however, requires the use of specific immunoreagents (typically antibodies or antigen-binding fragments) that recognize either the payload alone or the linker-payload, wherein the epitope is comprised of components of bothAttorney Docket No.15648.0054-00304 the linker and payload. Antibodies that recognize the payload alone have the added benefit that they can be used in assays to quantify ADC properties where the payload is paired with many different linker structures, making them useful in early-stage conjugate research activities where the final linker-payload structure is not fixed. Payload-recognizing agents with desirable features of high affinity and specificity for the payload alone may have broader utility beyond use in intact ADC assays, such as in immunodepletion of ADCs, immunopurification of conjugated species, and immunohistochemical analyses of ADCs in tissues.

[0005] Maleimide-based ADCs can undergo a process in matrix and in circulation known as retro-Michael deconjugation, where the intact maleimide linker-payload is released. Maleimides are highly reactive, have very short half-lives in plasma, and have several potential metabolic fates (FIG.1). In some instances, these linker-payload species may represent the majority of payload-related metabolites in circulation. These metabolites are typically measured using mass spectrometry. However, the quantitative assessment of these species by mass spectrometry represents an analytical challenge because each linker-payload metabolite has a unique mass and thus requires a separate assay. Furthermore, protein conjugate metabolites, such as albumin conjugates, would not be amenable to mass spectrometry methods for quantitation. It would therefore be beneficial to have a method to quantitate additional metabolites or all non-antibody conjugated linker-payload metabolites in total.

[0006] Accordingly, in various embodiments, the present disclosure provides improved methods and reagents for detecting and quantifying intact antibody-drug conjugates, constituent antibody-drug conjugate parts such as a linker-payload, e.g., Mal-(PEG)2-VCP- eribulin, and metabolites in a biological sample. SUMMARY

[0007] In various embodiments, the present disclosure provides, in part, a method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker- payload and the payload moiety is eribulin. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered the antibody-drug conjugate. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to anAttorney Docket No.15648.0054-00304 antibody portion of the antibody-drug conjugate and / or an unconjugated antibody or antigen- binding fragment. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to the payload moiety of the linker-payload. In some embodiments, the method comprises contacting the biological sample with a third antibody or antigen-binding fragment, wherein the third antibody or antigen-binding fragment is capable of specifically binding to the linker of the linker-payload. In some embodiments, the method comprises detecting a signal from the third antibody or antigen-binding fragment. In some embodiments, the metabolite in the biological sample is detected.

[0008] In various embodiments, the present disclosure provides a method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload and the payload moiety is eribulin. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered the antibody-drug conjugate. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the antibody-drug conjugate and / or an unconjugated antibody or antigen-binding fragment. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to the payload moiety of the linker-payload. In some embodiments, the method comprises contacting the biological sample with a third antibody or antigen-binding fragment, wherein the third antibody or antigen-binding fragment is capable of specifically binding to albumin. In some embodiments, the method comprises detecting a signal from the third antibody or antigen- binding fragment. In some embodiments, the metabolite in the biological sample is detected.

[0009] In some embodiments, contacting of the biological sample with the first antibody immunodepletes intact antibody-drug conjugate from the biological sample.

[0010] In some embodiments, the first antibody or antigen-binding fragment specifically binds farletuzumab or a fragment thereof. In some embodiments, the first antibody or antigen-binding fragment specifically binds 345A12-HC15-LC4 or a fragment thereof. In some embodiments, the first antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment thereof. In some embodiments, the linker-payload comprises Val-Cit-pAb-eribulin (“VCP-eribulin”). In some embodiments, the linker-payloadAttorney Docket No.15648.0054-00304 comprises Mal-(PEG)2-VCP-eribulin. In some embodiments, the third antibody or antigen- binding fragment specifically binds Val-Cit-pAB (“VCP”).

[0011] In various embodiments, the present disclosure provides a method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-202. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb- 202. In some embodiments, the method comprises contacting the biological sample with 2G9. In some embodiments, the method comprises contacting the biological sample with 5E4. In some embodiments, the method comprises contacting the biological sample with 11G6. In some embodiments, the method comprises detecting a signal from 11G6. In some embodiments, the metabolite in the biological sample is detected.

[0012] In various embodiments, the present disclosure provides a method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-202. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb- 202. In some embodiments, the method comprises contacting the biological sample with 2G9. In some embodiments, the method comprises contacting the biological sample with 5E4. In some embodiments, the method comprises contacting the biological sample with an anti- albumin antibody. In some embodiments, the method comprises detecting a signal from the anti-albumin antibody. In some embodiments, the metabolite in the biological sample is detected.

[0013] In various embodiments, the present disclosure provides a method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-109. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb- 109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc or an anti-idiotypic antibody or antigen binding fragment. In some embodiments, the anti-idiotypic antibody or antigen-binding fragmentAttorney Docket No.15648.0054-00304 comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. In some embodiments, the method comprises contacting the biological sample with 5E4. In some embodiments, the method comprises contacting the biological sample with 11G6. In some embodiments, the method comprises detecting a signal from 11G6. In some embodiments, the metabolite in the biological sample is detected.

[0014] In various embodiments, the present disclosure provides a method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-109. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb- 109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc or an anti-idiotypic antibody or antigen binding fragment. In some embodiments, the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. In some embodiments, the method comprises contacting the biological sample with 5E4. In some embodiments, the method comprises contacting the biological sample with an anti- albumin antibody. In some embodiments, the method comprises detecting a signal from the anti-albumin antibody. In some embodiments, the metabolite in the biological sample is detected.

[0015] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is an anti-idiotypic antibody. In some embodiments, the anti-idiotypic antibody specifically binds farletuzumab or a fragmentAttorney Docket No.15648.0054-00304 thereof. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen- binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0016] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen- binding fragment is an anti-idiotypic antibody. In some embodiments, the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0017] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting theAttorney Docket No.15648.0054-00304 biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen- binding fragment, wherein the first antibody or antigen-binding fragment is an anti-idiotypic antibody. In some embodiments, the anti-idiotypic antibody specifically binds 345A12- HC15-LC4 or a fragment thereof. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen- binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0018] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen- binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti- human IgG Fc antibody or antigen-binding fragment. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment is an anti-idiotypic antibody. In some embodiments, the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof. In some embodiments, the method comprises detecting a signal from the second antibody or antigen- binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0019] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment,Attorney Docket No.15648.0054-00304 wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen- binding fragment comprises 2G9. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the method comprises detecting a signal from second antibody or antigen-binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0020] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen- binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises 2G9. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0021] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting theAttorney Docket No.15648.0054-00304 biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the method comprises detecting a signal from second antibody or antigen-binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0022] In various embodiments, the present disclosure provides a method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen-binding fragment thereof. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen- binding fragment. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample is detected.

[0023] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to eribulin. In some embodiments, the method comprises contacting the biologicalAttorney Docket No.15648.0054-00304 sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment. In some embodiments, the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0024] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an antigen-binding fragment thereof, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment. In some embodiments, the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to eribulin. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0025] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to eribulin. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment. In some embodiments, the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof. In some embodiments, theAttorney Docket No.15648.0054-00304 method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0026] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti- idiotypic antibody or antigen-binding fragment. In some embodiments, the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen- binding fragment capable of specifically binding to eribulin. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0027] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is 5E4. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or is 2G9 or an antigen-binding fragment thereof. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0028] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specificallyAttorney Docket No.15648.0054-00304 binding to an antibody portion of the ADC and / or an antigen-binding fragment thereof, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment, or is 2G9 or an antigen-binding fragment. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding, wherein the second antibody or antigen-binding fragment is 5E4. In some embodiments, the method comprises detecting a signal from the second antibody or antigen- binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0029] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is 5E4. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment. In some embodiments, the anti-idiotypic antibody comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0030] In various embodiments, the present disclosure provides a method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method comprises contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an antigen-binding fragment thereof, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen binding fragment. In some embodiments, the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO:Attorney Docket No.15648.0054-00304 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. In some embodiments, the method comprises contacting the biological sample with a second antibody or antigen-binding, wherein the second antibody or antigen-binding fragment is 5E4. In some embodiments, the method comprises detecting a signal from the second antibody or antigen-binding fragment. In some embodiments, the intact ADC in the biological sample is detected.

[0031] In various embodiments, the present disclosure provides a method for detecting intact and / or total antibody-drug conjugate (ADC) and / or a metabolite of an ADC, wherein the metabolite is unconjugated antibody or antigen-binding fragment, linker-payload, and / or free payload.

[0032] In various embodiments, the present disclosure provides an antibody or antigen- binding fragment thereof capable of binding to an antibody-drug conjugate comprising farletuzumab and / or to farletuzumab or an antigen-binding fragment thereof. In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14.

[0033] In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system.

[0034] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14.Attorney Docket No.15648.0054-00304

[0035] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO: 16.

[0036] In various embodiments, the present disclosure provides an antibody or antigen- binding fragment thereof capable of binding to an antibody-drug conjugate comprising 345A12-HC15-LC4 and / or to 345A12-HC15-LC4 or an antigen-binding fragment thereof, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286.

[0037] In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system.

[0038] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286.

[0039] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO: 288.

[0040] In various embodiments, the present disclosure provides an antibody or antigen- binding fragment thereof capable of binding to eribulin.

[0041] In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable regionAttorney Docket No.15648.0054-00304 comprising an amino acid sequence of SEQ ID NO: 29, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30.

[0042] In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system.

[0043] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30.

[0044] In some embodiments, the antibody or antigen-binding fragment is an antigen- binding fragment. In some embodiments, the antigen-binding fragment is a Fab fragment.

[0045] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 31, and a light chain comprising an amino acid sequence of SEQ ID NO: 32.

[0046] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 294, and a light chain comprising an amino acid sequence of SEQ ID NO: 32.

[0047] In some embodiments, the antibody or antigen-binding fragment is an anti-eribulin antibody or antigen-binding fragment disclosed herein, e.g., in Tables 16-19.

[0048] In various embodiments, the present disclosure provides an antibody or antigen- binding fragment thereof capable of binding to Val-Cit-pAB (“VCP”).

[0049] In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and three light chainAttorney Docket No.15648.0054-00304 complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46.

[0050] In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 33 (HCDR1), SEQ ID NO: 34 (HCDR2), and SEQ ID NO: 35 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 36 (LCDR1), SEQ ID NO: 37 (LCDR2), and SEQ ID NO: 38 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 39 (HCDR1), SEQ ID NO: 40 (HCDR2), and SEQ ID NO: 41 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 42 (LCDR1), SEQ ID NO: 43 (LCDR2), and SEQ ID NO: 38 (LCDR3), as defined by the IMGT numbering system.

[0051] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46.

[0052] In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 47, and a light chain comprising an amino acid sequence of SEQ ID NO: 48.

[0053] In some embodiments, the antibody or antigen-binding fragment is an anti-VCP antibody or antigen-binding fragment disclosed herein, e.g., in Tables 22-25.

[0054] In some embodiments, an antibody or antigen-binding fragment disclosed herein is conjugated to a label. In some embodiments, the label comprises a fluorescent tag, a luminescent tag, an electrochemiluminescent tag, an enzyme reporter, a biotin, or a bead. In some embodiments, the label is a biotin. In some embodiments, the label is a bead. In some embodiments, the bead is an agarose bead or a magnetic bead. In some embodiments, the label is a fluorescent tag. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG.1 provides various metabolic pathways for maleimide-based ADCs.

[0056] FIG.2 shows forms of Mal-(PEG)2-VCP-eribulin immunizing and screening reagents.Attorney Docket No.15648.0054-00304

[0057] FIG.3 shows titer of rabbit immunized with KLH-(Mal-(PEG)2-VCP-eribulin) represented by bleed dilution factor (1 / x).

[0058] FIG.4 shows linker-payload structures and bio-layer interferometry (BLI) binding data used in screening anti-Mal-(PEG)2-VCP-eribulin clones. The linker-payloads structures used in the screening of an initial 12-gene rescued clones are shown in FIG 4A. FIG.4B shows BLI binding curves for the initial 12 gene-rescued clones. The VH and VL protein sequences for anti-Mal-(PEG)2-VCP eribulin antibodies are shown in FIG.4C. The linker payload structures of MORAb-003-based ADCS used to screen 6 selected clones are shown in FIG.4D. BLI binding trace data for anti-Mal-(PEG)2-VCP-eribulin antibodies binding to MORAb-003 and MORAb-003 ADCs are shown in FIG.4E. FIG.4F shows BLI binding curve data for 11G6 specificity.

[0059] FIG.5 shows sensogram data for 5E4 binding affinity. The first column displays 5E4 binding affinity, the second columns shows AbD26976 binding affinity, and the third column shows AbD26978 binding affinity.

[0060] FIG.6 is a schematic of an assay for measuring intact MORAb-202 using a biotinylated 5E4 monovalent Fab fragment as a capture reagent and anti-farletuzumab antibody 2G9 as a detector on the Gyros Xpand platform (FIG.6A). FIG.6B shows a standard binding curve.

[0061] FIG.7 is a schematic of an assay for measuring intact MORAb-109 using biotinylated 5E4 monovalent Fab fragment as a capture reagent and an anti-human Fc (CH2- specific) antibody as a detector on the Gyros XPand platform (FIG.7A). FIG.7B shows a standard binding curve.

[0062] FIGS.8A-B show the pharmacokinetics (PK) of MORAb-109 administered as an IV bolus dose in normal mice treated with MORAb-109 at a dose of either 10 mg / kg or 25 mg / kg. FIG.8C shows DAR and percent maleimide hydrolysis of MORAb-109 in normal mice.

[0063] FIGS.9A-C show MORAb-109 PK in NCI-H2110 tumor-bearing mice at a dose of 25 mg / kg or 50 mg / kg in plasma (FIG.9A) or tumor tissues (FIG.9B), and the corresponding PK parameters (FIG.9C).

[0064] FIGS.10A-B show mean concentration of total antibody, intact ADC, or eribulin after administration of MORAb-109 in cynomolgus monkeys (IV bolus, 2 monkeys) (FIG.Attorney Docket No.15648.0054-00304 10A), and corresponding DAR and percent maleimide hydrolysis after MORAb-109 administration (FIG.10B).

[0065] FIGS.11A-B show the concentration of MORAb-109 DAR2 and MORAb-109 DAR4 in plasma from normal rats dosed at 25 mg / kg or 75 mg / kg (FIG.11A) and corresponding PK parameters (FIG.11B).

[0066] FIG.12 is a schematic of an assay measuring intact anti-trastuzumab using a biotinylated 5E4 monovalent Fab fragment as a capture reagent and anti-trastuzumab as a detector on the Gyros Xpand platform (FIG.12A). FIG.12B shows a standard binding curve.

[0067] FIG.13 shows the stability of various trastuzumab-eribulin ADCs in both mouse plasma and human plasma (FIG.13A). The structures of linker-payloads attached to antibodies via transglutaminase transamidation onto the amide nitrogen of the glutamine residue in each linker are shown in FIG.13B in red. Corresponding PK parameters in normal mice injected with an IV bolus of either 5 mg / kg or 20 mg / kg of eribulin-conjugated trastuzumab are shown in FIGS.13C-D.

[0068] FIG.14 shows a schematic of an immunodepletion assay followed by linker- payload quantification (FIG.14A) and dynamic range of quantification assay (FIG.14B).

[0069] FIGS.15A-C show free linker-payload from MORAb-109 DAR2 in mouse plasma (comparison with random conjugation) (FIG.15A), DAR and percent maleimide hydrolysis of MORAb-109 (FIG.15B), and free eribulin and Mal-(PEG)2-VCP-eribulin in mouse plasma (FIG.15C).

[0070] FIG.16 shows released linker-payload and free payload after treatment with MORAb-109 in mouse or human plasma following maleimide ring opening.

[0071] FIG.17 is a schematic of an assay for detecting eribulin-conjugated albumin species in plasma.

[0072] FIGS.18A-C show the total released linker-payload, eribulin-conjugated albumin, and free eribulin in plasma from mice, humans, or monkeys treated with MORAb-202 (FIG. 18), percent DAR loss after MORAb-202 treatment (FIG.18B), and percent maleimide hydrolysis after MORAb-202 treatment (FIG.18C). FIG.18D shows MORAb-202 plasma stability in monkeys.

[0073] FIG.19 shows total antibody, intact ADC, total non-ADC linker-payload, eribulin- conjugated albumin, and free payload in MORAb-202-dosed non-human primate (NHP) (FIG.19A) and PK parameters (FIG.19B).Attorney Docket No.15648.0054-00304

[0074] FIGS.20A-B show levels of circulating total antibody, intact ADC, albumin- eribulin conjugate, and free eribulin (FIG.20A) and corresponding PK parameters (FIG. 20B) in normal rats dosed with MORAb-109. FIG.20C shows DAR loss due to retro- Michael release and maleimide hydrolysis in normal rats dosed with MORAb-109.

[0075] FIG.21 shows staining of human ovarian cancer xenograft OVCAR-3 tumors from MORAb-202-treated mice.

[0076] FIG.22 shows staining of human lung cancer xenograft NCI-H2110 tumors from MORAb-109-treated mice (day 3 post-treatment).

[0077] FIG.23 shows an analytical workflow diagram. DETAILED DESCRIPTION

[0078] The disclosed compositions and methods may be understood more readily by reference to the following detailed description taken in connection with the accompanying figures, which form a part of this disclosure. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed compositions and methods unless the context indicates otherwise.

[0079] Throughout this text, the descriptions refer to compositions and methods of using the compositions. Where the disclosure describes or claims a feature or embodiment associated with a composition, such a feature or embodiment is equally applicable to the methods of using the composition. Likewise, where the disclosure describes or claims a feature or embodiment associated with a method of using a composition, such a feature or embodiment is equally applicable to the composition.

[0080] When a range of values is expressed, it includes embodiments using any particular value within the range. Further, reference to values stated in ranges includes each and every value within that range. All ranges are inclusive of their endpoints and combinable. When values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. Reference to a particular numerical value includes at least that particular value unless the context clearly dictates otherwise. The use of “or” will mean “and / or” unless the specific context of its use dictates otherwise. All references cited herein are incorporated by reference for any purpose. Where a reference and the specification conflict, the specification will control.Attorney Docket No.15648.0054-00304

[0081] It is to be appreciated that certain features of the disclosed compositions and methods, which are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosed compositions and methods that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Definitions

[0082] Various terms relating to aspects of the description are used throughout the specification and claims. Such terms are to be given their ordinary meaning in the art unless otherwise indicated. Other specifically defined terms are to be construed in a manner consistent with the definitions provided herein.

[0083] As used herein, the singular forms “a,” “an,” and “the” include plural forms unless the context clearly dictates otherwise.

[0084] The terms "about" or "approximately" in the context of numerical values and ranges refers to values or ranges that approximate or are close to the recited values or ranges such that the embodiment may perform as intended, such as having a desired amount of nucleic acids or polypeptides in a reaction mixture, as is apparent to the skilled person from the teachings contained herein. Thus, these terms encompass values beyond those resulting from systematic error. In some embodiments, about means plus or minus 10% of a numerical amount.

[0085] The terms “antibody-drug conjugate,” “antibody conjugate,” “conjugate,” “immunoconjugate,” and “ADC” are used interchangeably, and refer to a therapeutic compound (e.g., an eribulin moiety) that is linked to an antibody moiety and is defined by the generic formula: Ab-(L-D)p (Formula I), wherein Ab is an antibody moiety (e.g., an antibody or antigen-binding fragment), L is a linker moiety, D is a drug moiety (e.g., an eribulin drug moiety), and p is the number of drug moieties per antibody moiety. In ADCs comprising an eribulin drug moiety, “p” refers to the number of eribulin moieties linked to the antibody moiety. In some embodiments, the linker L can include a cleavable moiety that can either directly attach to the antibody moiety and to the therapeutic compound, or the cleavable moiety can be attached to either or both the antibody moiety and therapeutic compound by spacer unit(s). In some embodiments, when a spacer unit attaches the cleavable moiety to the therapeutic compound, it is a self-immolative spacer unit.Attorney Docket No.15648.0054-00304

[0086] As used herein, “intact,” in the context of an ADC, refers to an ADC that remains attached to its original number of linker-payload moieties, e.g., if an ADC has DAR4, an “intact” ADC has an average ratio of 4 linker-payload moieties per antibody in solution, e.g., plasma.

[0087] The term “antibody” is used in the broadest sense to refer to an immunoglobulin molecule that recognizes and specifically binds to a target, such as a protein, polypeptide, carbohydrate, polynucleotide, lipid, or combinations of the foregoing through at least one antigen recognition site within the variable region of the immunoglobulin molecule. The heavy chain of an antibody is composed of a heavy chain variable domain (VH) and a heavy chain constant region (CH). The light chain is composed of a light chain variable domain (VL) and a light chain constant domain (CL). For the purposes of this application, the mature heavy chain and light chain variable domains each comprise three complementarity determining regions (CDR1, CDR2, and CDR3) within four framework regions (FR1, FR2, FR3, and FR4) arranged from N-terminus to C-terminus: FR1, CDR1, FR2, CDR2, FR3, CDR3, and FR4. An “antibody” can be naturally occurring or man-made, such as monoclonal antibodies produced by conventional hybridoma technology. The term “antibody” includes full-length monoclonal antibodies and full-length polyclonal antibodies, as well as antibody fragments such as Fab, Fab’, F(ab’)2, Fv, and single chain antibodies. An antibody can be any one of the five major classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM, or subclasses thereof (e.g., isotypes IgG1, IgG2, IgG3, IgG4). The term further encompasses human antibodies, chimeric antibodies, humanized antibodies and any modified immunoglobulin molecule containing an antigen recognition site, so long as it demonstrates the desired biological activity.

[0088] The term “monoclonal antibody,” as used herein, refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic epitope. In contrast, conventional (polyclonal) antibody preparations typically include a multitude of antibodies directed against (or specific for) different epitopes. The modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, theAttorney Docket No.15648.0054-00304 monoclonal antibodies to be used in accordance with the present disclosure may be made by the hybridoma method first described by Kohler et al. (1975) Nature 256:495, or may be made by recombinant DNA methods (see, e.g., U.S. Patent No.4,816,567). Monoclonal antibodies may also be isolated from phage antibody libraries using the techniques described in Clackson et al. (1991) Nature 352:624-8, and Marks et al. (1991) J. Mol. Biol.222:581-97, for example.

[0089] The monoclonal antibodies described herein specifically include “chimeric” antibodies, in which a portion of the heavy and / or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they specifically bind the target antigen and / or exhibit the desired biological activity.

[0090] The term “chimeric antibody,” as used herein, refers to antibodies wherein the amino acid sequence of the immunoglobulin molecule is derived from two or more species. In some instances, the variable regions of both heavy and light chains correspond to the variable regions of antibodies derived from one species with the desired specificity, affinity, and activity while the constant regions are homologous to antibodies derived from another species (e.g., human) to minimize an immune response in the latter species.

[0091] As used herein, the term “humanized antibody” refers to forms of antibodies that contain sequences from non-human (e.g., rabbit) antibodies as well as human antibodies. Such antibodies are chimeric antibodies which contain minimal sequences derived from non- human immunoglobulin. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the hypervariable loops correspond to those of a non-human immunoglobulin and all or substantially all of the framework (FR) regions are those of a human immunoglobulin sequence. The humanized antibody optionally also will comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin. The humanized antibody can be further modified by the substitution of residues, either in the Fv framework region and / or within the replaced non-human residues to refine and optimize antibody specificity, affinity, and / or activity.Attorney Docket No.15648.0054-00304

[0092] The term “antigen-binding fragment,” “antigen-binding domain,” or “antigen- binding portion” of an antibody, as used herein, refers to one or more fragments of an antibody or protein that retain the ability to specifically bind to an antigen (e.g., eribulin). Antigen-binding fragments may also retain the ability to internalize into an antigen- expressing cell. In some embodiments, antigen-binding fragments also retain immune effector activity. It has been shown that fragments of a full-length antibody can perform the antigen-binding function of a full-length antibody. Examples of binding fragments encompassed within the term “antigen-binding fragment,” “antigen-binding domain,” or “antigen-binding portion” of an antibody include (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL, and CH1 domains; (ii) a F(ab')2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting of the VH and CH1 domains; (iv) a Fv fragment consisting of the VL and VH domains of a single arm of an antibody; (v) a dAb fragment, which comprises a single variable domain, e.g., a VH domain (see, e.g., Ward et al. (1989) Nature 341:544-6; and Intl. Pub. No. WO 1990 / 005144); and (vi) an isolated complementarity determining region (CDR). Furthermore, although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VL and VH regions pair to form monovalent molecules (known as single chain Fv (scFv)). See, e.g., Bird et al. (1988) Science 242:423-6; and Huston et al. (1988) Proc. Natl. Acad. Sci. USA 85:5879-83. Such single chain antibodies are also intended to be encompassed within the term “antigen-binding fragment” or “antigen-binding portion” of an antibody, and are known in the art as an exemplary type of binding fragment that can internalize into cells upon binding (see, e.g., Zhu et al. (2010) 9:2131-41; He et al. (2010) J. Nucl. Med.51:427-32; and Fitting et al. (2015) MAbs 7:390-402). In certain embodiments, scFv molecules may be incorporated into a fusion protein. Other forms of single chain antibodies, such as diabodies, are also encompassed. Diabodies are bivalent, bispecific antibodies in which VH and VL domains are expressed on a single polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with complementary domains of another chain and creating two antigen-binding sites (see e.g., Holliger et al. (1993) Proc. Natl. Acad. Sci. USA 90:6444-8; and Poljak et al. (1994) Structure 2:1121-3). Antigen-binding fragments are obtained using conventional techniquesAttorney Docket No.15648.0054-00304 known to those of skill in the art, and the binding fragments are screened for utility (e.g., binding affinity, internalization) in the same manner as are intact antibodies. Antigen-binding fragments may be prepared by cleavage of the intact protein, e.g., by protease or chemical cleavage.

[0093] “Internalizing” as used herein in reference to an antibody or antigen-binding fragment refers to an antibody or antigen-binding fragment that is capable of being taken through the cell’s lipid bilayer membrane to an internal compartment (i.e., “internalized”) upon binding to the cell, typically into a degradative compartment in the cell. For example, an internalizing anti-eribulin antibody is one that is capable of being taken into the cell after binding to eribulin on the cell membrane. In some embodiments, the antibody or antigen- binding fragment used in the ADCs disclosed herein targets a cell surface antigen (e.g., eribulin) via an internalizing antibody or internalizing antigen-binding fragment (allowing the ADC to transfer through the cellular membrane after antigen-binding).

[0094] The term “mesothelin” or “MSLN,” as used herein, refers to any native form of human mesothelin (MSLN). The term encompasses full-length mesothelin (e.g., NCBI Reference Sequence: AAC50348.1; SEQ ID NO: 271), as well as any form of human mesothelin that results from cellular processing. The term also encompasses naturally occurring variants of mesothelin, including but not limited to splice variants, allelic variants, and isoforms. Mesothelin can be isolated from a human, or may be produced recombinantly or by synthetic methods. The term may also encompass any synthetic variant to which an anti-mesothelin antibody, e.g., an antibody disclosed herein, and / or antigen-binding fragment, can specifically bind.

[0095] The term “anti-MSLN antibody” or “antibody that specifically binds MSLN” refers to any form of antibody or fragment thereof that specifically binds MSLN, and encompasses monoclonal antibodies (including full length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they specifically bind MSLN. Preferably the anti-MSLN antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment.345A12-HC15-LC4 (“345A12”) is an exemplary internalizing anti-human MSLN antibody. An anti-MSLN antibody may be conjugated to a drug, e.g., eribulin, via a linker. Exemplary antibody-drug conjugates comprising anti-MSLN antibodies are known in the literature and include MORAb-109. The structure of MORAb-109 is as shown in US Patent Serial No.11,572,414, which isAttorney Docket No.15648.0054-00304 incorporated herein by reference for all ADC and linker-payload structures and methods of synthesizing those structures. In some embodiments, MORAb-109 comprises an anti-MSLN antibody or antigen-binding fragment, 345A12-HC15-LC4, a cleavable linker comprising Mal-(PEG)2-Val-Cit-pAB, and a payload comprising eribulin (see Table 1).

[0096] The term “folate receptor alpha” or “FRA,” as used herein, refers to any native form of human FRA. The term encompasses full-length FRA (e.g., NCBI Reference Sequence: NP_000793; SEQ ID NO: 270), as well as any form of human FRA that results from cellular processing. The term also encompasses naturally occurring variants of FRA, including but not limited to splice variants, allelic variants, and isoforms. FRA can be isolated from a human or may be produced recombinantly or by synthetic methods.

[0097] The term “anti-FRA antibody” or “antibody that specifically binds FRA” refers to any form of antibody or fragment thereof that specifically binds FRA, and encompasses monoclonal antibodies (including full length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they specifically bind FRA. Preferably the anti-FRA antibody used in the ADCs disclosed herein is an internalizing antibody or internalizing antibody fragment. MORAb-003 is an exemplary internalizing anti- human FRA antibody. As used herein, the term “MORAb-003” and “farletuzumab” are interchangeable. An anti-FRA antibody may be conjugated to a drug, e.g., eribulin, via a linker. Exemplary antibody-drug conjugates comprising anti-FRA antibodies are known in the literature and include MORAb-202. The structure of MORAb-202 is as shown in US Patent Serial No.10,322,192, which is incorporated herein by reference for all ADC and linker-payload structures and methods of synthesizing those structures. In some embodiments, MORAb-202 comprises the anti-FRA antibody farletuzumab, a cleavable linker comprising Mal-(PEG)2-Val-Cit-pAB, and a payload comprising eribulin (see Table 1). Table 1. MORAb-202 and MORAb-109 Target Antibody Linker Payload M RA 2 2 FRA M RA M l PE V l it AB E i li

[0098] The term “human epidermal growth factor receptor 2,” “HER2,” or “HER2 / neu,” as used herein, refers to any native form of human HER2. The term encompasses full-lengthAttorney Docket No.15648.0054-00304 her2 (e.g., NCBI Reference Sequence: NP_004439.2; SEQ ID NO: 272), as well as any form of human her2 that results from cellular processing. The term also encompasses naturally occurring variants of her2, including but not limited to splice variants, allelic variants, and isoforms. Her2 can be isolated from human, or may be produced recombinantly or by synthetic methods. An anti-HER2 antibody may be conjugated to a drug, e.g., eribulin, via a linker. Exemplary ADCs comprising anti-HER2 antibodies are known in the literature.

[0099] The term “anti-ID antibody” or “anti-idiotypic antibody” refers to an antibody that binds the idiotype, i.e., variable region, of a second antibody. Exemplary anti-ID antibodies include anti-farletuzumab antibodies (e.g., 2G9) and anti-345A12 antibodies (e.g., M000053) as described herein.

[0100] The term “anti-eribulin antibody” or “antibody that specifically binds eribulin” or “eribulin-specific antibody” refers to any form of antibody or fragment thereof that specifically binds eribulin, and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they specifically bind eribulin. In some embodiments, 5E4 is an exemplary eribulin-specific antibody.

[0101] The term “anti-linker antibody” refers to any form of antibody or antigen-binding fragment thereof that specifically binds a linker. As an example, an “anti-VCP antibody” or “antibody that specifically binds VCP” or “VCP-specific antibody” or “antibody that specifically binds a linker-payload comprising VCP” is an antibody that binds a linker comprising valine-citruline-p-aminobenzyloxycarbonyl (VCP), and encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, and biologically functional antibody fragments so long as they specifically bind VCP. In some embodiments, 11G6 is an exemplary VCP-specific antibody. An anti-linker antibody may bind the linker when conjugated to an antibody and / or payload, or it may bind only when the linker is liberated from one or more of the other components, or it may bind in both contexts.

[0102] As used herein, the terms “specific,” “specifically binds,” and “binds specifically” refer to the selective binding of an antibody to a target antigen epitope. Antibodies can be tested for specificity of binding by comparing binding to an appropriate antigen with binding to an irrelevant antigen or antigen mixture under a given set of conditions. Methods for measuring antibody binding affinity and kinetics are known in the art and include, e.g.,Attorney Docket No.15648.0054-00304 Biacore. If the antibody binds to the appropriate antigen with at least 2, 5, 7, or 10 times greater affinity than to the irrelevant antigen or antigen mixture, then it is considered to be specific. A “specific antibody” or “target-specific antibody” is one that only binds the target antigen (e.g., farletuzumab, 345A12, or human IgG Fc), but does not bind (or exhibits minimal binding to) other antigens.

[0103] The term “epitope” refers to the portion of an antigen capable of being recognized and specifically bound by an antibody. When the antigen is a polypeptide, epitopes can be formed from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of the polypeptide. The epitope bound by an antibody may be identified using any epitope mapping technique known in the art, including X-ray crystallography for epitope identification by direct visualization of the antigen-antibody complex, as well as monitoring the binding of the antibody to fragments or mutated variations of the antigen, or monitoring solvent accessibility of different parts of the antibody and the antigen. Exemplary strategies used to map antibody epitopes include, but are not limited to, array-based oligo-peptide scanning, limited proteolysis, site-directed mutagenesis, high-throughput mutagenesis mapping, hydrogen-deuterium exchange, and mass spectrometry (see, e.g., Gershoni et al. (2007) 21:145-56; and Hager-Braun and Tomer (2005) Expert Rev. Proteomics 2:745-56).

[0104] Competitive binding and epitope binning can also be used to determine antibodies sharing identical or overlapping epitopes. Competitive binding can be evaluated using a cross-blocking assay, such as the assay described in “Antibodies, A Laboratory Manual,” Cold Spring Harbor Laboratory, Harlow and Lane (1stedition 1988, 2ndedition 2014). In some embodiments, competitive binding is identified when a test antibody or binding protein reduces binding of a reference antibody or binding protein to a target antigen such as farletuzumab or 345A12 (e.g., a binding protein comprising CDRs and / or variable domains selected from those identified in Tables 1-3 and Tables 6-8), by at least about 50% in the cross-blocking assay (e.g., 50%, 60%, 70%, 80%, 90%, 95%, 99%, 99.5%, or more, or any percentage in between), and / or vice versa. In some embodiments, competitive binding can be due to shared or similar (e.g., partially overlapping) epitopes, or due to steric hindrance where antibodies or binding proteins bind at nearby epitopes (see, e.g., Tzartos, Methods in Molecular Biology (Morris, ed. (1998) vol.66, pp.55-66)). In some embodiments, competitive binding can be used to sort groups of binding proteins that share similar epitopes. For example, binding proteins that compete for binding can be “binned” as a group of bindingAttorney Docket No.15648.0054-00304 proteins that have overlapping or nearby epitopes, while those that do not compete are placed in a separate group of binding proteins that do not have overlapping or nearby epitopes.

[0105] The term "kon" or "ka" refers to the on-rate constant for association of an antibody to the antigen to form the antibody / antigen complex. The rate can be determined using standard assays, such as a surface plasmon resonance, biolayer inferometry, or ELISA assay.

[0106] The term "koff" or "kd" refers to the off-rate constant for dissociation of an antibody from the antibody / antigen complex. The rate can be determined using standard assays, such as a surface plasmon resonance, biolayer inferometry, or ELISA assay.

[0107] The term "KD" refers to the equilibrium dissociation constant of a particular antibody-antigen interaction. KDis calculated by ka / kd. The rate can be determined using standard assays, such as a surface plasmon resonance, biolayer inferometry, or ELISA assay.

[0108] The term “p” or “drug loading” or “drug:antibody ratio” or “drug-to-antibody ratio” or “DAR” refers to the number of drug moieties per antibody moiety, i.e., drug loading, or the number of -L-D moieties per antibody or antigen-binding fragment (Ab) in ADCs of Formula (I). In ADCs comprising an eribulin drug moiety, “p” refers to the number of eribulin moieties linked to the antibody moiety. For example, if two eribulin moieties are linked to an antibody moiety, p = 2. In compositions comprising multiple copies of ADCs of Formula (I), “average p” refers to the average number of -L-D moieties per antibody or antigen-binding fragment in a population of ADCs, also referred to as “average drug loading.”

[0109] A “linker” or “linker moiety” is used herein to refer to any chemical moiety that is capable of covalently joining a compound, usually a drug moiety such as eribulin, to another moiety such as an antibody moiety. Linkers can be susceptible to or substantially resistant to acid-induced cleavage, peptidase-induced cleavage, light-based cleavage, esterase-induced cleavage, and / or disulfide bond cleavage, at conditions under which the compound or the antibody remains active.

[0110] The term “payload” is used herein to refer to a chemical compound or a biological macromolecule that is capable of being conjugated to an antibody. A payload may be capable of modulating a biological process and / or have biological activity. The terms “agent,” “therapeutic agent,” “drug,” or “drug moiety” are interchangeable with “payload” herein. In some embodiments, the payload is eribulin.Attorney Docket No.15648.0054-00304

[0111] The term “linker-payload” is used herein to refer to a conjugate comprising a linker (e.g., VCP) and a payload (e.g., eribulin). Unless otherwise indicated, reference to a “linker-payload” as used herein refers to a linker-payload metabolite that is not conjugated to an antibody or ADC. In some embodiments, an antibody disclosed herein is capable of binding to an epitope present in a linker-payload.

[0112] The term “eribulin” or “eribulin monomer,” as used herein, refers to a synthetic analog of halichondrin B, a macrocyclic compound that was originally isolated from the marine sponge Halichondria okadais. Eribulin is a microtubule dynamics inhibitor, which is thought to bind tubulin and induce cell cycle arrest at the G2 / M phase by inhibiting mitotic spindle assembly. The term “eribulin mesylate” refers to the mesylate salt of eribulin, which is marketed under the trade name Halaven™. Exemplary eribulin analogs include those shown and described in U.S. Patent No.6,214,865 and U.S. Patent No.6,653,341, which are incorporated herein by reference for the disclosed eribulin structures and methods of synthesizing those structures. The structure of eribulin is shown below.

[0113] The term “homolog” refers to a molecule which exhibits homology to another molecule, by for example, having sequences of chemical residues that are the same or similar at corresponding positions.

[0114] The term “inhibit” or “inhibition of,” as used herein, means to reduce by a measurable amount, and can include but does not require complete prevention or inhibition.

[0115] The term “cancer” refers to the physiological condition in mammals in which a population of cells is characterized by unregulated cell growth. Examples of cancers include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia. More particular examples of such cancers include squamous cell cancer, small cell lung cancer, nonsmall cell lung cancer, adenocarcinoma of the lung, squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer (e.g., triple negative breast cancer), osteosarcoma, melanoma, colon cancer, colorectal cancer, endometrial (e.g., serous) or uterine cancer, salivary gland carcinoma, kidney cancer, liver cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, and various types of head and neck cancers. Triple negative breast cancer refers to breast cancer that is negative for expression of the genes for estrogen receptor (ER), progesterone receptor (PR), or Her2 / neu.Attorney Docket No.15648.0054-00304

[0116] The terms “tumor” and “neoplasm” refer to any mass of tissue that results from excessive cell growth or proliferation, either benign or malignant, including precancerous lesions.

[0117] The term “tumor cell” refers to individual cells or the total population of cells derived from a tumor, including both non-tumorigenic cells and cancer stem cells. As used herein, the term “tumor cell” will be modified by the term “non-tumorigenic” when referring solely to those tumor cells lacking the capacity to renew and differentiate to distinguish those tumor cells from cancer stem cells.

[0118] The terms “subject” and “patient” are used interchangeably herein to refer to any animal, such as any mammal, including but not limited to, humans, non-human primates, rodents, and the like. In some embodiments, the mammal is a mouse. In some embodiments, the mammal is a human.

[0119] As used herein, “to treat” or “therapeutic” and grammatically related terms refer to any improvement of any consequence of disease, such as prolonged survival, less morbidity, and / or a lessening of side effects which are the byproducts of an alternative therapeutic modality. As is readily appreciated in the art, full eradication of disease is encompassed but not required for a treatment act. “Treatment” or “treat,” as used herein, refers to the administration of a described antibody, antigen-binding fragment, and / or ADC to a subject, e.g., a patient. The treatment can be to cure, heal, alleviate, relieve, alter, remedy, ameliorate, palliate, improve or affect the disorder, the symptoms of the disorder or the predisposition toward the disorder, e.g., a cancer. In some embodiments, in addition to treating a subject with a condition, a composition disclosed herein can also be provided prophylactically to prevent or reduce the likelihood of developing that condition.

[0120] In some embodiments, a labeled antibody, antigen-binding fragment, and / or ADC is used. A label is any moiety attached to an antibody that facilitates its detection in an assay in which the antibody is used. In some embodiments, the label is a detectable label. Suitable “labels” or “detectable labels” include fluorescent tags, radionuclides, enzymes, substrates, cofactors, inhibitors, fluorescent moieties, luminescent moieties, chemiluminescent moieties, electrochemiluminescent moieties, biotin, beads, magnetic particles, and the like. The terms “conjugated to a biotin” and “biotinylated” are used interchangeably herein.

[0121] For amino acid sequences, sequence identity and / or similarity may be determined using standard techniques known in the art, including, but not limited to, the local sequenceAttorney Docket No.15648.0054-00304 identity algorithm of Smith and Waterman (1981) Adv. Appl. Math.2:482, the sequence identity alignment algorithm of Needleman and Wunsch (1970) J. Mol. Biol.48:443, the search for similarity method of Pearson and Lipman (1988) Proc. Nat. Acad. Sci. USA 85:2444, computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Drive, Madison, Wis.), the Best Fit sequence program described by Devereux et al. (1984) Nucl. Acid Res.12:387-95, e.g., using the default settings, or by inspection. In some embodiments, percent identity is calculated by FastDB based upon the following parameters: mismatch penalty of 1; gap penalty of 1; gap size penalty of 0.33; and joining penalty of 30 (“Current Methods in Sequence Comparison and Analysis,” Macromolecule Sequencing and Synthesis, Selected Methods and Applications, pp.127-149 (1988), Alan R. Liss, Inc).

[0122] Generally, the amino acid homology, similarity, or identity between proteins disclosed herein and variants thereof, including variants of target antigens (such as farletuzumab or 345A12), variants of tubulin sequences, and variants of antibody variable domains (including individual variant CDRs), are at least 80% to the sequences depicted herein, e.g., homologies or identities of at least 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, almost 100%, or 100%.

[0123] In a similar manner, “percent (%) nucleic acid sequence identity” with respect to the nucleic acid sequence of the antibodies and other proteins identified herein is defined as the percentage of nucleotide residues in a candidate sequence that are identical with the nucleotide residues in the coding sequence of the antigen-binding protein. A specific method utilizes the BLASTN module of WU-BLAST-2 set to the default parameters, with overlap span and overlap fraction set to 1 and 0.125, respectively.

[0124] While the site or region for introducing an amino acid sequence variation is predetermined, the mutation per se need not be predetermined. For example, in order to optimize the performance of a mutation at a given site, random mutagenesis may be conducted at the target codon or region and the expressed antigen-binding protein CDR variants screened for the optimal combination of desired activity. Techniques for making substitution mutations at predetermined sites in DNA having a known sequence are well known, for example, MI3 primer mutagenesis and PCR mutagenesis.

[0125] The term “immunodepletion” or “antibody depletion” refers to an assay whereby a target antigen, e.g., an ADC, antibody, antigen-binding fragment, or linker-payloadAttorney Docket No.15648.0054-00304 conjugate, is depleted or removed from a solution using an antibody that specifically binds to said antigen.

[0126] The terms “metabolite” and “ADC metabolite” refer to components of an ADC that, through chemical, biochemical, or enzymatic processes are released from the ADC. ADC metabolites may include ADCs with DAR lower than starting DAR, antibodies, antigen-binding fragments, linker-payload conjugates, free payload moieties, free linker conjugates (i.e., without a payload attached), or any combination thereof. Antibodies and Antigen-Binding Fragments

[0127] The present disclosure provides antibodies or antigen-binding fragments thereof for use in methods of detecting and quantifying intact antibody-drug conjugates or constituent antibody-drug conjugate parts such as a linker-payload, e.g., Mal-(PEG)2-VCP-eribulin or albumin-Mal-(PEG)2-VCP-eribulin, in a biological sample.

[0128] In some embodiments, the antibody or antigen-binding fragments may bind to a target antigen with a dissociation constant (KD) of ≤1 mM, ≤100 nM or ≤10 nM, or any amount in between, as measured by, e.g., BIAcore® analysis. In certain embodiments, the KD is 1 pM to 500 pM. In some embodiments, the KD is between 500 pM to 1 µM, 1 µM to 100 nM, or 100 mM to 10 nM.

[0129] In some embodiments, the antibody moiety is a four-chain antibody (also referred to as an immunoglobulin), comprising two heavy chains and two light chains. In some embodiments, the antibody moiety is a two-chain half body (one light chain and one heavy chain), or an antigen-binding fragment of an immunoglobulin.

[0130] In some embodiments, the antibody moiety is an antigen-binding fragment thereof. Anti-Farletuzumab Antibodies and Antigen-Binding Fragments

[0131] The present disclosure provides antibody and antigen-binding fragments thereof that specifically bind to an antibody-drug conjugate comprising farletuzumab and / or to farletuzumab or an antigen-binding fragment thereof. All references herein to “anti- farletuzumab” antibodies encompass antibodies that bind to farletuzumab, to an antibody- drug conjugate comprising farletuzumab, or to an antigen-binding fragment thereof.

[0132] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment, e.g., one used in any of the assays disclosed herein, may comprise a paired set of heavy andAttorney Docket No.15648.0054-00304 light chain variable domains taken from those listed in Table 3, or the set of six CDR sequences from the paired heavy and light chain set, e.g., a set of CDRs listed in Tables 1-2. In some embodiments, an antibody or antigen-binding fragment further comprises human heavy and light chain frameworks (optionally with one or more backmutations to improve binding affinity) and / or human heavy and light chain constant domains or fragments thereof. For instance, the antibody or antigen-binding fragment may comprise a human IgG heavy chain constant domain (such as an IgG1) and a human kappa or lambda light chain constant domain. In some embodiments, the antibody or antigen-binding fragment comprises a human immunoglobulin G subtype 1 (IgG1) heavy chain constant domain (SEQ ID NO: 81) with a human Ig kappa light chain constant domain (SEQ ID NO: 82).

[0133] Amino acid and nucleic acid sequences of exemplary anti-farletuzumab antibodies of the present disclosure are set forth in Tables 2-6. Table 2. Amino acid sequences of Kabat CDRs for an anti-farletuzumab antibody mAb IgG chain SEQ ID Amino acid sequence 2 H DR1 1TYAVHTable 3. Amino acid sequences of IMGT CDRs for an anti-farletuzumab antibody mAb IgG chain SEQ ID Amino acid sequenceAttorney Docket No.15648.0054-00304 Table 4. Amino acid sequences of variable regions for an anti-farletuzumab antibody mAb IgG chain SEQ ID Amino acid sequence 2G9 VH 13QVQLKQSGPGLVQPSQSLSITCTVSGFSLSTYAVHWVS G Q Kantibody mAb IgG chain SEQ ID Amino acid sequence 2G9 Heav chain 15QVQLKQSGPGLVQPSQSLSITCTVSGFSLSTYAVHWVS G K S D E Q I V L L Q K A LAttorney Docket No.15648.0054-00304 Table 6. Nucleic acid sequences of full-length antibody chains for an anti-farletuzumab antibody mAb IgG chain SEQ ID Nucleic acid sequence 2G9 Heavy 83CAGGTGCAGCTGAAGCAGTCAGGACCTGGCCTAGTGCAGCCCTCA T A T T A T C T G G C A T T G G A G C A T G C T T T T GAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence Light 84GACATCCAGATGACTCAGTCTCCAGTCTCCCTATCTGCACCTGTT T C A T A T T A A C T A, ment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three LCDRs comprising SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3) as defined by the Kabat numbering system (Kabat, Sequences of Proteins of Immunological Interest (National Institutes of Health, Bethesda, Md. (1987 and 1991))).

[0135] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three LCDRs comprising SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system (International ImMunoGeneTics Information System (IMGT®)).

[0136] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13. In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14.Attorney Docket No.15648.0054-00304

[0137] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 13. In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment comprises three LCDRs from the light chain variable region comprising SEQ ID NO: 14.

[0138] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 13. In some embodiments, an anti-farletuzumab antibody or antigen- binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 14.

[0139] In some embodiments, an antigen-binding fragment disclosed herein is a variant that retains farletuzumab binding specificity. In some embodiments, the antigen-binding fragment retains farletuzumab binding by comprising three HCDRs comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three LCDRs comprising SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3) as defined by the Kabat numbering system. In some embodiments, the antigen-binding fragment comprises three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) comprising three HCDRs comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three LCDRs comprising SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system. In some embodiments, the antigen- binding fragments disclosed herein may retain farletuzumab binding by comprising a VH domain comprising an amino acid sequence comprising SEQ ID NO: 13 and a VL domain comprising an amino acid sequence comprising SEQ ID NO: 14.

[0140] In various embodiments, an anti-farletuzumab antibody disclosed herein comprises a human IgG heavy chain constant domain. In some embodiments, the IgG heavy chain constant domain is IgG1.Attorney Docket No.15648.0054-00304

[0141] In various embodiments, an anti-farletuzumab antibody disclosed herein comprise a human Ig kappa light chain constant region. In various embodiments, the anti-farletuzumab antibodies comprise a human Ig lambda light chain constant region.

[0142] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15. In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 16.

[0143] In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment is antibody 2G9.

[0144] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein is conjugated to a label. In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment is conjugated to a fluorescent tag. In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment is conjugated to a biotin moiety. In some embodiments, an anti-farletuzumab antibody provided herein is conjugated to streptavidin. In some embodiments, the anti-farletuzumab antibody or antigen- binding fragment is conjugated to an enzyme reporter. In some embodiments, the anti- farletuzumab antibody or antigen-binding fragment is conjugated to a bead. In some embodiments, the bead is an agarose bead or a magnetic bead.

[0145] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein is conjugated to an agarose bead or a magnetic bead.

[0146] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein is biotinylated.

[0147] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 49, HCDR2 comprising SEQ ID NO: 50, HCDR3 comprising SEQ ID NO: 51; LCDR1 comprising SEQ ID NO: 52, LCDR2 comprising SEQ ID NO: 53, and LCDR3 comprising SEQ ID NO: 54, as defined by the Kabat numbering system. In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 55,Attorney Docket No.15648.0054-00304 HCDR2 comprising SEQ ID NO: 56, HCDR3 comprising SEQ ID NO: 57; LCDR1 comprising SEQ ID NO: 58, LCDR2 comprising SEQ ID NO: 59, and LCDR3 comprising SEQ ID NO: 60, as defined by the IMGT numbering system.

[0148] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising a heavy chain variable domain comprising a sequence of SEQ ID NO: 61 and a light chain variable domain comprising a sequence of SEQ ID NO: 62.

[0149] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising a heavy chain of SEQ ID NO: 63 and a light chain sequence of SEQ ID NO: 64.

[0150] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein specifically binds farletuzumab or an ADC comprising farletuzumab.

[0151] In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment provided herein specifically binds MORAb-202. Anti-345A12 Antibodies and Antigen-Binding Fragments

[0152] The present disclosure also provides antibody and antigen-binding fragments thereof that specifically bind to an antibody-drug conjugate comprising 345A12 and / or to 345A12 or an antigen-binding fragment thereof. All references herein to “anti-345A12” antibodies encompass antibodies that bind to 345A12, to an antibody-drug conjugate comprising 345A12, or to an antigen-binding fragment thereof.

[0153] In some embodiments, an anti-345A12 antibody or antigen-binding fragment, e.g., one used in any of the assays disclosed herein, may comprise a paired set of heavy and light chain variable domains taken from those listed in Table 9, or the set of six CDR sequences from the paired heavy and light chain set, e.g., a set of CDRs listed in Tables 7-8. In some embodiments, an antibody or antigen-binding fragment further comprises human heavy and light chain frameworks (optionally with one or more backmutations to improve binding affinity) and / or human heavy and light chain constant domains or fragments thereof. For instance, the antibody or antigen-binding fragment may comprise a human IgG heavy chain constant domain (such as an IgG1) and a human kappa or lambda light chain constant domain. In some embodiments, the antibody or antigen-binding fragment comprises a humanAttorney Docket No.15648.0054-00304 immunoglobulin G subtype 1 (IgG1) heavy chain constant domain (SEQ ID NO: 81) with a human Ig lambda light chain constant domain (SEQ ID NO: 291).

[0154] Amino acid and nucleic acid sequences of exemplary anti-345A12 antibodies of the present disclosure are set forth in Tables 7-11. Table 7. Amino acid sequences of Kabat CDRs for an anti-345A12 idiotypic antibody mAb IgG chain SEQ ID Amino acid sequence Anti-345A12 HC CDR1 273SYAMH. q yp y mAb IgG chain SEQ ID Amino acid sequence FTF YATable 9. Amino acid sequences of variable regions for an anti-345A12 idiotypic antibody mAb IgG chain SEQ ID Amino acid sequence V N D W S LAttorney Docket No.15648.0054-00304 Table 10. Amino acid sequences of full-length antibody chains and scfv antibody fragments for an anti-345A12 idiotypic antibody mAb IgG chain SEQ ID Amino acid sequence Anti-345A12 VH-VL 293QVQLVQSGGGVVQPGRSLRLSCAASGFTFSSYAMHWVN D P T R K V N D L L E I K A S D Q W S L A LAttorney Docket No.15648.0054-00304 Table 11. Nucleic acid sequences of heavy and light chain variable regions for an anti- 345A12 idiotypic antibody mAb IgG chain SEQ ID Nucleic acid sequence Anti- VH 289CAGGTGCAGCTGGTGCAGTCTGGGGGAGGCGTGGTCCAGCCTGGGAAG AG AG AA CT CA TC ACGC CC TG AT CT GG

[0055] n some embod men s, an an -3 5 do ypc an body or an gen-b nd ng fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three LCDRs comprising SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3) as defined by the Kabat numbering system.

[0156] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three LCDRs comprising SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT.

[0157] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285. In some embodiments, an anti-345A12 idiotypic antibody orAttorney Docket No.15648.0054-00304 antigen-binding fragment thereof provided herein comprises a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286.

[0158] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 285. In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment comprises three LCDRs from the light chain variable region comprising SEQ ID NO: 286.

[0159] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 285. In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 286.

[0160] In some embodiments, an antigen-binding fragment disclosed herein is a variant that retains 345A12 binding specificity. In some embodiments, the antigen-binding fragment retains 345A12 binding by comprising three HCDRs comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three LCDRs comprising SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3) as defined by the Kabat numbering system. In some embodiments, the antigen-binding fragment comprises three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) comprising three HCDRs comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three LCDRs comprising SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system. In some embodiments, the antigen-binding fragments disclosed herein may retain 345A12 binding by comprising a VH domain comprising an amino acid sequence comprising SEQ ID NO: 285 and a VL domain comprising an amino acid sequence comprising SEQ ID NO: 286.Attorney Docket No.15648.0054-00304

[0161] In various embodiments, an anti-345A12 idiotypic antibody disclosed herein comprises a human IgG heavy chain constant domain. In some embodiments, the IgG heavy chain constant domain is IgG1.

[0162] In various embodiments, an anti-345A12 idiotypic antibody disclosed herein comprise a human Ig kappa light chain constant region. In various embodiments, the anti- 345A12 idiotypic antibodies comprise a human Ig lambda light chain constant region.

[0163] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287. In some embodiments, an anti-345A12 idiotypic antibody or antigen- binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 288.

[0164] In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment is antibody M000053.

[0165] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein is conjugated to a label. In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment is conjugated to a fluorescent tag. In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment is conjugated to a biotin moiety. In some embodiments, the anti-345A12 idiotypic antibody is conjugated to streptavidin. In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment is conjugated to an enzyme reporter. In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment is conjugated to a bead. In some embodiments, the bead is an agarose bead or a magnetic bead.

[0166] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein is conjugated to an agarose bead or a magnetic bead.

[0167] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein is biotinylated.

[0168] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 65, HCDR2 comprising SEQ ID NO: 66, HCDR3 comprising SEQ ID NO: 67; LCDR1 comprising SEQ ID NO: 68, LCDR2 comprising SEQ ID NO: 69, and LCDR3 comprising SEQ ID NO: 70, as defined by the Kabat numbering system. In someAttorney Docket No.15648.0054-00304 embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 71, HCDR2 comprising SEQ ID NO: 72, HCDR3 comprising SEQ ID NO: 73; LCDR1 comprising SEQ ID NO: 74, LCDR2 comprising SEQ ID NO: 75, and LCDR3 comprising SEQ ID NO: 76, as defined by the IMGT numbering system.

[0169] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising a heavy chain variable domain comprising a sequence of SEQ ID NO: 77 and a light chain variable domain comprising a sequence of SEQ ID NO: 78.

[0170] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein specifically binds an ADC, antibody, or antigen-binding fragment comprising a heavy chain of SEQ ID NO: 79 and a light chain sequence of SEQ ID NO: 80.

[0171] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein specifically binds 345A12 or an ADC comprising 345A12.

[0172] In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment provided herein specifically binds MORAb-109. Exemplary Antibodies Bound by Anti-ID Antibodies

[0173] Tables 12-15 set forth exemplary amino acid sequences of anti-FRA, anti-MSLN, and anti-HER2 antibodies. Amino acid sequences of human FRA, MSLN, and HER2 antibodies are disclosed in Table 16. Table 12. Amino acid sequences of ADC mAb Kabat CDRs mAb IgG chain SEQ ID NO Amino acid sequenceAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID NO Amino acid sequence 345A12-HC15- HC CDR2 66VIDISGNRFYADWVKG. q mAb IgG chain SEQ ID NO Amino acid sequenceAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID NO Amino acid sequence LC CDR1 263QDVNTAa e . mno ac sequences of m vara e regons mAb IgG chain SEQ ID NO Amino acid sequence Farletuzumab VH 61EVQLVESGGGVVQPGRSLRLSCSASGFTS D G S A I D N S G S S A N G N Q D S AAttorney Docket No.15648.0054-00304 Table 15. Amino acid sequences of full-length ADC mAb Ig chains mAb IgG chain SEQ ID NO Amino acid sequence Farletuzumab Heavy chain 63EVQLVESGGGVVQPGRSLRLSCSASGFTFSGYGKG RH AP AL TQ PC CV EQ AL KN TT SV NNGS MY GT ES CE YAGR VD AP AL TQ PC CV EQ AL KN TT SVAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID NO Amino acid sequence Light chain 80DYQMTQSPSSLSASVGDRVTITCQASQSIFSYLSG DN GT ES CE TYKG RW LA GA GT CP VT RE NK LT YK SC AVSR FG SV TE THTable 16. Amino acid sequences of antibodies and constant domains mAb or constant SEQ ID NO Amino acid sequenceKECG LC HF EVAttorney Docket No.15648.0054-00304 mAb or constant domainSEQ ID NO Amino acid sequenceAPQK AC DV AL WR IF PQ EM SL NG PL LQ DMNQ PG LA CA PA VC AN EE GI LH EC CV NC LI EL NK HV KS FT PP IQ DP EGAttorney Docket No.15648.0054-00304 mAb or constant domainSEQ ID NO Amino acid sequenceTD RP SP GAPS LM YN GQ QP AL GAPS DNVT ADVTDrug Moieties

[0174] The drug moiety (D) of the ADCs and linker-payload conjugates described herein can be any chemotherapeutic agent. Useful classes of chemotherapeutic agents include, for example, anti-tubulin agents. In certain embodiments, the drug moiety is an anti-tubulin agent. One exemplary drug moiety for use in the described ADCs and linker-payload conjugates is eribulin.

[0175] Eribulin is a synthetic analog of the macrocyclic compound halichondrin B, which has been previously shown to be a potent inhibitor of tubulin polymerization, microtubule assembly, and tubulin-dependent GTP hydrolysis. Tubulin makes up dynamic filamentous cytoskeletal proteins called microtubules that are involved in a variety of vital cellular functions, including intracellular migration and transport, cell signaling, the maintenance of cell shape, and cell division. The rapid dividing rate of cancer cells makes them particularly sensitive to the obstruction of tubulin function. As such, halichondrin B and eribulin haveAttorney Docket No.15648.0054-00304 demonstrated notable anti-cancer activities in vitro and in vivo (Tan et al. (2009) Clin Cancer Res.15(12): 4213-4219; Vahdat et al. (2009) J. Clin. Oncol.27(18): 2954-2961). The mesylate salt of eribulin (eribulin mesylate) is currently marketed under the trade name Halaven™ for the treatment of patients with refractory metastatic breast cancer.

[0176] In various embodiments, the structure of eribulin used in its natural form in the disclosed ADCs and linker-payload conjugates is as shown in Formula (II):

[0177] In various used in the disclosedADCs and linker- as which is incorporated herein by reference for all eribulin structures and methods of synthesizing those structures. Anti-eribulin Antibodies and Antigen-Binding Fragments

[0178] The present disclosure also provides antibodies or antigen-binding fragments thereof that specifically bind to eribulin, e.g., which may be used in any of the assays disclosed herein.

[0179] The antibodies disclosed herein that specifically bind eribulin may comprise three HC CDRs (HCDR1, HCDR2, and HCDR3) having amino acid sequences selected from the HC CDRs listed in Table 17, infra, as defined by the Kabat numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) having amino acid sequences selected from the LC CDRs listed in Table 17, infra, as defined by the Kabat numbering system. In some embodiments, the antibodies comprise three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) having amino acid sequences selected from the HC CDRs listed in Table 18, infra, as defined by the IMGT numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) having amino acid sequences selected from the LC CDRs listed in Table 18, infra, as defined by the IMGT numbering system.Attorney Docket No.15648.0054-00304

[0180] In some embodiments, an antibody disclosed herein comprises a VH domain having an amino acid sequence selected from SEQ ID NOs: 29, 101, 119, 137, 153, 169, 183, 200, 217, and 234 listed in Table 19, infra. In some embodiments, the antibody comprises a VL domain having an amino acid sequence selected from SEQ ID NOs: 30, 102, 120, 138, 154, 170, 184, 201, 218, and 235 listed in Table 19, infra.

[0181] In some embodiments, an antigen-binding fragment disclosed herein is a variant that retains eribulin binding specificity. In some embodiments, the antigen-binding fragment retains eribulin binding by comprising three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) comprising amino acid sequences selected from the HC CDRs listed in Table 17, infra, as defined by the Kabat numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) comprising amino acid sequences selected from the LC CDRs listed in Table 17, infra, as defined by the Kabat numbering system. In some embodiments, the antigen-binding fragment comprises three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) comprising amino acid sequences selected from the HC CDRs listed in Table 18, infra, as defined by the IMGT numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) comprising amino acid sequences selected from the LC CDRs listed in Table 18, infra, as defined by the IMGT numbering system. In some embodiments, the antigen-binding fragments disclosed herein may retain eribulin binding by comprising a VH domain comprising an amino acid sequence selected from SEQ ID NOs: 29, 101, 119, 137, 153, 169, 183, 200, 217, and 234 listed in Table 19, infra, and a VL domain comprising an amino acid sequence selected from SEQ ID NOs: 30, 102, 120, 138, 154, 170, 184, 201, 218, and 235 listed in Table 19, infra.

[0182] In some embodiments, an antibody or antigen-binding fragment further comprises human heavy and light chain frameworks (optionally with one or more backmutations to improve binding affinity) and / or human heavy and light chain constant domains or fragments thereof. For instance, the antibody or antigen-binding fragment may comprise a human IgG heavy chain constant domain (such as an IgG1) and a human kappa or lambda light chain constant domain. In some embodiments, the antibody or antigen-binding fragment comprises a human IgG1 heavy chain constant domain with a human Ig kappa light chain constant domain.

[0183] In some embodiments, an antibody that specifically binds eribulin comprises a heavy chain having an amino acid sequence selected from SEQ ID NOs: 31, 103, 121, 139,Attorney Docket No.15648.0054-00304 155, 171, 185, 202, 219, and 236 listed in Table 20, infra. In some embodiments, an antibody that specifically binds eribulin comprises a light chain having an amino acid sequence selected from SEQ ID NOs: 32, 104, 122, 140, 156, 172, 186, 203, 220, and 237 listed in Table 20, infra.

[0184] Amino acid and nucleic acid sequences of exemplary anti-eribulin antibodies of the present disclosure, e.g., those which may be used in any of the assays disclosed herein, are set forth in Tables 17-21. Table 17. Amino acid sequences of Kabat CDRs for anti-eribulin antibodies mAb IgG chain SEQ ID Amino acid sequence 5E4 HC CDR1 17SSYGLCAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence LC CDR1 128QASQNINSWLAAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence LC CDR1 44QASQSVYSNNYLA. mAb IgG chain SEQ ID Amino acid sequence 5E4 HC CDR1 23GFSFSSSYGAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence 5P14 HC CDR1 131GFSFSTSYHAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence 12M17 HC CDR1 211GFTLNNYW. q g mAb IgG chain SEQ ID Amino acid sequence VH E LEE DLVKPE LTLT TA F F Y LCWK Y W T V V S L W T VAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence 5E24VH119QSLEESGGDLVKPGASLTLTCTASGFSFSSTYYMCWVT F W T V W A G Q T V W A G Q T V W T G W T V V T FAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence VL184AQVLTQTASPVSAAVGSTVTINCQSSQSVWNNKHLAWT V V T D W T V R S P W T V W K F W T VTable 20. Amino acid sequences of full-length and Fab fragment antibody chains for anti- eribulin antibodies mAb IgG chain SEQ ID Amino acid sequence W K Y A GAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence LYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKV W T V R L W K Y A G V M T K V S T V S L G Y P S P L L G K W T V RAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence EAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTL V T F G Q D D N V K V N W T V R L W A G L L S T E A C F L Q T V RAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence EAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTL W A G L L S T E A C F L Q T V E T W T G K S D E Q I V L L W T V EAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence AKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLT V T F G Q D D N V K V N W T V R L V T D L L E I K A S D Q W T V EAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence AKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLT R S P V S C P E P L F S W T V R L W K F S P N P V Y D T E W T V RAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence EAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTL smAb IgG chain SEQ ID Nucleic acid sequence 5E4 Heavy chain 85CAGGAGCAGCTGGAGGAGTCCGGGGGAGACCTGGTCAAGCCTGAGGGCA AG GC CA CC TG AT GC TT CG CC AC CA CG CC CA TC CC CA AG AA AT TC GG CG GG CT A GGGA AAAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence CAACTGATCTATGATGCATCGAAACTGGCATCTGGGGTCTCATCGCG CG AT GT GC TG GA GG GC CA GT GGCT GG TG GA TT AG CA CT GA GC GC AT AG CA AA CG GG GA CC CC AA GG GC CC CTAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence CCTTCTTCTTATATTCAAAGCTCACCGTGGACAAGAGCAGGTGGCAG AA GGTA AG CG CG AT GT GC TG GA GG GC CA GT TCCT GG AG GG AT GC CT CC AA CC GA GG CA CA TT CC AG AA CAAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence GCGTCCTCACCGTCCTGCACCAGGACTGGCTGAATGGCAAGGAGTAC AC CC CC GA GC AC CA TC GGTA AG CG CG AT GT GC TG GA GG GC CA GT GGTA AG AA GG AT TG CC GC GT CT TG AAAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence CGTGAATCACAAGCCCAGCAACACCAAGGTGGACAAGAAAGTTGAGC CT AA GG TG CA CC AA CA GC AT AA CT GG TA GGTT TG AG GG AT GT GC TG GA GG GC CA GT GGCA AA AG GG TG TGAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence GGGCCCAGGCACCCTGGTCACCGTCTCCTCAGCATCCACCAAGGGCC GC GT CT TG AA GC CT AA GG TG CA CC AA CA GC AT AA CT GG TA GGTT TG AA GG AT GT AT TG AA CA AA CA T GGCAAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence GCTACTGGATATGCTGGGTCCGCCAGGCTCCAGGGAAGAGGCCTGAG AG GG AT CC GG CG GT GG CC AA AT TC AC CG GC AA CT TC CG CA GC TA AT TC CA GGTA AG CG CG AT GT AT TG AA CAAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence GCAAGGACAGCACCTACAGCCTCAGCAGCACCCTGACGCTGAGCAAA CA T TCCT GG AG GG AT GC CT CC AA CC GA GG CA CA TT CC AG AA CA AC AC CC CC GA GC AC CA TC GGTA AG CG CGAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence ACGTGCAGTGTGACGATGCTGCCACTTACTACTGTCTAGGCAGTTAT GT GC TG GA GG GC CA GT GGCA GG TG GG AT TA CA CC CC CG TC TA GA GC CC AT AC CG CG TC GC CC AA CA CG GGAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence CAGCAGGGGAACGTCTTCTCATGCTCCGTGATGCATGAGGCTCTGCA GGTA AG CG CG AT GT AT TG AA CA AA CA T TCCT TC GC TC GT GG AT CA AC CC TG GT CA AA GA GG AC TA GG CC CCAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence CCGAGAACCACAGGTGTACACCCTGCCCCCATCCCGGGATGAGCTGA CC AA CT AC AC GGTA AG CG TG AT GT GC TG GA GG GC CA GT GGCA AG CC CA TG GC CC CC GG GA TA TC GC AC GGAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence ACCGTCAGTCTTCCTCTTCCCCCCAAAACCCAAGGACACCCTCATGA AC GT GT AT CC AC AG GC CA AG TG CC GGGT AG CG CG AT GT GC TG GA GG GC CA GT

[0185] In some embodiments, the sequences of the heavy chain variable domains, light chain variable domains, full-length heavy chains, and full-length light chains may be “mixed and matched” to create variants of the anti-eribulin antibodies. Such “mixed and matched” anti-eribulin antibodies can be tested using binding assays known in the art (e.g., ELISAs and other assays described in the Examples). In various embodiments, the anti-eribulin antibodies disclosed herein may comprise any set of heavy and light chain variable domains listed inAttorney Docket No.15648.0054-00304 Table 19 above, or the set of six CDR sequences from the heavy and light chain set. In some embodiments, the antibodies further comprise human heavy and light chain constant domains or fragments thereof. In some embodiments, the anti-eribulin antibodies may comprise a human IgG heavy chain constant domain and a human kappa light chain constant domain. In some embodiments, the anti-eribulin antibodies may comprise a human IgG1, IgG2, IgG3, or IgG4 heavy chain constant domain. In various embodiments, an anti-eribulin antibody of the present invention comprises a human immunoglobulin G subtype 1 (IgG1) heavy chain constant domain with a human Ig kappa light chain constant domain. In various embodiments, the anti-eribulin antibodies may comprise any set of full-length heavy chain and full-length light chain sequences listed in Table 20 above.

[0186] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three LCDRs comprising SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3) as defined by the Kabat numbering system.

[0187] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three LCDRs comprising SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3) as defined by the IMGT numbering system.

[0188] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 89 (HCDR1), SEQ ID NO: 90 (HCDR2), and SEQ ID NO: 91 (HCDR3); and three LCDRs comprising SEQ ID NO: 92 (LCDR1), SEQ ID NO: 93 (LCDR2), and SEQ ID NO: 94 (LCDR3) as defined by the Kabat numbering system.

[0189] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 95 (HCDR1), SEQ ID NO: 96 (HCDR2), and SEQ ID NO: 97 (HCDR3); and three LCDRs comprising SEQ ID NO: 98 (LCDR1), SEQ ID NO: 99 (LCDR2), and SEQ ID NO: 100 (LCDR3) as defined by the IMGT numbering system.

[0190] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 107 (HCDR1),Attorney Docket No.15648.0054-00304 SEQ ID NO: 108 (HCDR2), and SEQ ID NO: 109 (HCDR3); and three LCDRs comprising SEQ ID NO: 110 (LCDR1), SEQ ID NO: 111 (LCDR2), and SEQ ID NO: 112 (LCDR3) as defined by the Kabat numbering system.

[0191] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 113 (HCDR1), SEQ ID NO: 114 (HCDR2), and SEQ ID NO: 115 (HCDR3); and three LCDRs comprising SEQ ID NO: 116 (LCDR1), SEQ ID NO: 117 (LCDR2), and SEQ ID NO: 118 (LCDR3) as defined by the IMGT numbering system.

[0192] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 125 (HCDR1), SEQ ID NO: 126 (HCDR2), and SEQ ID NO: 127 (HCDR3); and three LCDRs comprising SEQ ID NO: 128 (LCDR1), SEQ ID NO: 129 (LCDR2), and SEQ ID NO: 130 (LCDR3) as defined by the Kabat numbering system.

[0193] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 131 (HCDR1), SEQ ID NO: 132 (HCDR2), and SEQ ID NO: 133 (HCDR3); and three LCDRs comprising SEQ ID NO: 134 (LCDR1), SEQ ID NO: 135 (LCDR2), and SEQ ID NO: 136 (LCDR3) as defined by the IMGT numbering system.

[0194] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 143 (HCDR1), SEQ ID NO: 144 (HCDR2), and SEQ ID NO: 145 (HCDR3); and three LCDRs comprising SEQ ID NO: 146 (LCDR1), SEQ ID NO: 129 (LCDR2), and SEQ ID NO: 147 (LCDR3) as defined by the Kabat numbering system.

[0195] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 148 (HCDR1), SEQ ID NO: 149 (HCDR2), and SEQ ID NO: 150 (HCDR3); and three LCDRs comprising SEQ ID NO: 151 (LCDR1), SEQ ID NO: 135 (LCDR2), and SEQ ID NO: 152 (LCDR3) as defined by the IMGT numbering system.

[0196] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 159 (HCDR1), SEQ ID NO: 160 (HCDR2), and SEQ ID NO: 161 (HCDR3); and three LCDRs comprisingAttorney Docket No.15648.0054-00304 SEQ ID NO: 162 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 163 (LCDR3) as defined by the Kabat numbering system.

[0197] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 164 (HCDR1), SEQ ID NO: 165 (HCDR2), and SEQ ID NO: 166 (HCDR3); and three LCDRs comprising SEQ ID NO: 167 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 168 (LCDR3) as defined by the IMGT numbering system.

[0198] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 175 (HCDR1), SEQ ID NO: 176 (HCDR2), and SEQ ID NO: 109 (HCDR3); and three LCDRs comprising SEQ ID NO: 177 (LCDR1), SEQ ID NO: 111 (LCDR2), and SEQ ID NO: 178 (LCDR3) as defined by the Kabat numbering system.

[0199] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 179 (HCDR1), SEQ ID NO: 180 (HCDR2), and SEQ ID NO: 115 (HCDR3); and three LCDRs comprising SEQ ID NO: 181 (LCDR1), SEQ ID NO: 117 (LCDR2), and SEQ ID NO: 182 (LCDR3) as defined by the IMGT numbering system.

[0200] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 189 (HCDR1), SEQ ID NO: 190 (HCDR2), and SEQ ID NO: 191 (HCDR3); and three LCDRs comprising SEQ ID NO: 192 (LCDR1), SEQ ID NO: 193 (LCDR2), and SEQ ID NO: 194 (LCDR3) as defined by the Kabat numbering system.

[0201] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 195 (HCDR1), SEQ ID NO: 196 (HCDR2), and SEQ ID NO: 197 (HCDR3); and three LCDRs comprising SEQ ID NO: 198 (LCDR1), SEQ ID NO: 117 (LCDR2), and SEQ ID NO: 199 (LCDR3) as defined by the IMGT numbering system.

[0202] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 206 (HCDR1), SEQ ID NO: 207 (HCDR2), and SEQ ID NO: 208 (HCDR3); and three LCDRs comprising SEQ ID NO: 44 (LCDR1), SEQ ID NO: 209 (LCDR2), and SEQ ID NO: 210 (LCDR3) as defined by the Kabat numbering system.Attorney Docket No.15648.0054-00304

[0203] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 211 (HCDR1), SEQ ID NO: 212 (HCDR2), and SEQ ID NO: 213 (HCDR3); and three LCDRs comprising SEQ ID NO: 214 (LCDR1), SEQ ID NO: 215 (LCDR2), and SEQ ID NO: 216 (LCDR3) as defined by the IMGT numbering system.

[0204] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 223 (HCDR1), SEQ ID NO: 224 (HCDR2), and SEQ ID NO: 225 (HCDR3); and three LCDRs comprising SEQ ID NO: 226 (LCDR1), SEQ ID NO: 227 (LCDR2), and SEQ ID NO: 228 (LCDR3) as defined by the Kabat numbering system.

[0205] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 229 (HCDR1), SEQ ID NO: 230 (HCDR2), and SEQ ID NO: 231 (HCDR3); and three LCDRs comprising SEQ ID NO: 232 (LCDR1), SEQ ID NO: 99 (LCDR2), and SEQ ID NO: 233 (LCDR3) as defined by the IMGT numbering system.

[0206] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 30. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 101, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 102. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 119, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 120. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 137, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 138. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 153, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 154. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 169, and a light chainAttorney Docket No.15648.0054-00304 variable region comprising the amino acid sequence of SEQ ID NO: 170. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 183, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 184. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 200, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 201. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 217, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 218. In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 234, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 235.

[0207] In some embodiments, an anti-eribulin antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 30.

[0208] In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 29, and three LCDRs from the light chain variable region comprising SEQ ID NO: 30. In some embodiments, an anti-eribulin antibody or antigen- binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 101, and three LCDRs from the light chain variable region comprising SEQ ID NO: 102. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 119, and three LCDRs from the light chain variable region comprising SEQ ID NO: 120. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 137, and three LCDRs from the light chain variable region comprising SEQ ID NO: 138. In some embodiments, an anti- eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 153, and three LCDRs from the light chain variable region comprising SEQ ID NO: 154. In some embodiments, anAttorney Docket No.15648.0054-00304 anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 169, and three LCDRs from the light chain variable region comprising SEQ ID NO: 170. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 183, and three LCDRs from the light chain variable region comprising SEQ ID NO: 184. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 200, and three LCDRs from the light chain variable region comprising SEQ ID NO: 201. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 217, and three LCDRs from the light chain variable region comprising SEQ ID NO: 218. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 234, and three LCDRs from the light chain variable region comprising SEQ ID NO: 235.

[0209] In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 29, and three LCDRs from the light chain variable region comprising SEQ ID NO: 30.

[0210] In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 29. In some embodiments, an anti-eribulin antibody or antigen- binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 101. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 119. In some embodiments, an anti-eribulinAttorney Docket No.15648.0054-00304 antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 153. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 169. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 183. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 200. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 217. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 234.

[0211] In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 30. In some embodiments, an anti-eribulin antibody or antigen- binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at leastAttorney Docket No.15648.0054-00304 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 102. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 120. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 154. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 170. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 184. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 201. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 218. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 235.Attorney Docket No.15648.0054-00304

[0212] In various embodiments, the anti-eribulin antibody or antigen-binding fragment is an antigen-binding fragment. In some embodiments, an anti-eribulin antigen-binding fragment is a Fab fragment.

[0213] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 31. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 32. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is a Fab fragment.

[0214] In various embodiments, the anti-eribulin antibodies comprise a human IgG heavy chain constant domain. In some embodiments, the IgG heavy chain constant domain is IgG1.

[0215] In various embodiments, the anti-eribulin antibodies comprise a human Ig kappa light chain constant region. In various embodiments, the anti-eribulin antibodies comprise a human Ig lambda light chain constant region.

[0216] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 294. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 32. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 103. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 104. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 121. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 122. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 139. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 140. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 155. In someAttorney Docket No.15648.0054-00304 embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 156. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 171. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 172. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 185. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 186. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 202. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 203. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 219. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 220. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 236. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 237.

[0217] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 294. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 32. In some embodiments, the anti-eribulin antibody or antigen-binding fragment comprises a human IgG1 heavy chain constant domain.

[0218] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein is antibody 5E4. In some embodiments, 5E4 is a Fab. In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein is antibody 5P14.Attorney Docket No.15648.0054-00304

[0219] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein is conjugated to a label. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is conjugated to a fluorescent tag. In some embodiments, the anti- eribulin antibody or antigen-binding fragment is conjugated to a biotin moiety. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is conjugated to a streptavidin. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is conjugated to an enzyme reporter. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is conjugated to a bead. In some embodiments, the bead is an agarose bead or a magnetic bead.

[0220] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein is conjugated to an agarose bead or a magnetic bead.

[0221] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein is conjugated to a biotin. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is immobilized on a solid surface.

[0222] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein binds to eribulin with a binding affinity of at least 0.1 nM, at least 0.2 nM, at least 0.3 nM, at least 0.4 nM, at least 0.5 nM, at least 0.6 nM, at least 0.7 nM, at least 0.8 nM, at least 0.9 nM, at least 1.0 nM, at least 1.1 nM, at least 1.2 nM, at least 1.3 nM, at least 1.4 nM, at least 1.5 nM, at least 2.0 nM, at least 2.5 nM, at least 3.0 nM, at least 3.5 nM, at least 4.0 nM, at least 4.5 nM, at least 5.0 nM, at least 5.5 nM, at least 6.0 nM, at least 6.5 nM, at least 7.0 nM, at least 7.5 nM, at least 8.0 nM, at least 8.5 nM, at least 9.0 nM, at least 9.5 nM, or at least 10.0 nM. Linkers and Linker-Payload Conjugates

[0223] In various embodiments, an antibody or antigen-binding fragment disclosed herein specifically binds to a linker or linker-payload conjugate. An exemplary linker or linker- payload conjugate comprises VCP.

[0224] In some embodiments, the linker in an ADC is stable extracellularly in a sufficient manner to be therapeutically effective. In some embodiments, the linker is stable outside a cell, such that the ADC remains primarily intact when present in extracellular conditions (e.g., prior to transport or delivery into a cell). As used herein, “stable,” in the context of a linker or ADC comprising a linker, means that no more than 20%, no more than about 15%,Attorney Docket No.15648.0054-00304 no more than about 10%, no more than about 5%, no more than about 3%, or no more than about 1% of the linkers (or any percentage in between) in a sample of ADC are cleaved (or in the case of an overall ADC are otherwise not intact) when the ADC is present in extracellular conditions. In some embodiments, the ADC is metabolized in circulation such that a linker- payload is cleaved from the ADC.

[0225] Whether a linker is stable extracellularly can be determined, for example, by including an ADC in plasma for a predetermined time period (e.g., 2, 4, 6, 8, 16, or 24 hours) and then quantifying the amount of free linker-payload and / or free drug moiety present in the plasma. Stability may allow the ADC time to localize to target tumor cells and prevent the premature release of the drug, which could lower the therapeutic index of the ADC by indiscriminately damaging both normal and tumor tissues. In some embodiments, the linker is stable outside of a target cell and releases the drug moiety from the ADC once inside of the cell, such that the drug moiety can bind to its target (e.g., to microtubules). Thus, an effective linker will: (i) maintain the specific binding properties of the antibody moiety; (ii) allow delivery, e.g., intracellular delivery, of the drug moiety via stable attachment to the antibody moiety; (iii) remain stable and intact until the ADC has been transported or delivered to its target site; and (iv) allow for the therapeutic effect, e.g., cytotoxic effect, of the drug moiety after cleavage. In determining the efficacy of a linker, it is beneficial to be able to measure linker or linker-payload metabolites.

[0226] A linker may be “cleavable” or “non-cleavable” (Ducry and Stump, Bioconjugate Chem. (2010) 21:5-13). Cleavable linkers are designed to release the drug when subjected to certain environment factors, e.g., when internalized into a target cell, whereas non-cleavable linkers generally rely on the degradation of the antibody moiety itself.

[0227] In some embodiments, the linker is a cleavable linker. A cleavable linker refers to any linker that comprises a cleavable moiety. As used herein, the term “cleavable moiety” refers to any chemical bond that can be cleaved. Suitable cleavable chemical bonds are known in the art and include, but are not limited to, acid labile bonds, protease / peptidase labile bonds, photolabile bonds, disulfide bonds, and esterase labile bonds. Linkers comprising a cleavable moiety can allow for the release of the drug moiety from the ADC via cleavage at a particular site in the linker. In various embodiments, cleavage of the antibody from the linked payload activates or increases the activity of the payload. ExemplaryAttorney Docket No.15648.0054-00304 cleavable linkers include acid labile linkers, protease / peptidase-sensitive linkers, photolabile linkers, dimethyl-, disulfide-, or sulfonamide-containing linkers.

[0228] In some embodiments, the linker is cleavable by a cleaving agent, e.g., an enzyme, that is present in the intracellular environment (e.g., within a lysosome or endosome or caveolea). The linker can be, e.g., a peptide linker that is cleaved by an intracellular peptidase or protease enzyme, including, but not limited to, a lysosomal or endosomal protease. In some embodiments, the linker is a cleavable peptide linker. As used herein, a cleavable peptide linker refers to any linker that comprises a cleavable peptide moiety. The term “cleavable peptide moiety” refers to any chemical bond linking amino acids (natural or synthetic amino acid derivatives) that can be cleaved by an agent that is present in the intracellular environment. For instance, a linker may comprise an alanine-alanine-asparagine (Ala-Ala-Asn) sequence, a valine-alanine (Val-Ala) sequence, or a valine-citrulline (Val-Cit) sequence that is cleavable by a peptidase such as cathepsin, e.g., cathepsin B.

[0229] In some embodiments, the linker in any of the ADCs disclosed herein may comprise at least one spacer unit joining the antibody moiety to the drug moiety. In some embodiments, the spacer unit joins a cleavage site (e.g., a cleavable peptide moiety) in the linker to the antibody moiety. In some embodiments, the linker, and / or spacer unit in the linker, is substantially hydrophilic. A hydrophilic linker may be used to reduce the extent to which the drug may be pumped out of resistant cancer cells through multiple drug resistance (MDR) or functionally similar transporters. In some aspects, the linker includes one or more polyethylene glycol (PEG) moieties, e.g., 1, 2, 3, 4, 5, or 6 PEG moieties.

[0230] In some embodiments, the spacer unit in the linker comprises one or more PEG moieties. In some embodiments, the spacer unit comprises -(PEG)m-, and m is an integer from 1 to 10. In some embodiments, m ranges from 1 to 10; from 2 to 8; from 2 to 6; from 2 to 5; from 2 to 4; or from 2 to 3. In some embodiments, m is 8. In some embodiments, m is 4. In some embodiments, m is 3. In some embodiments, m is 2. In some embodiments, the spacer unit comprises (PEG)2, (PEG)4, (PEG)8, (PEG)9, (PEG)3-triazole-(PEG)3, (PEG)4-triazole- (PEG)3, or dibenzylcyclooctene-triazole-(PEG)3. In some preferred embodiments, the spacer unit comprises (PEG)2.

[0231] In some embodiments, the spacer unit in the linker comprises an alkyl moiety. In some embodiments, the spacer unit comprises -(CH2)n-, and n is an integer from 1 to 10 (i.e., n may be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10). In some embodiments, n is 5.Attorney Docket No.15648.0054-00304

[0232] A spacer unit may be used, for example, to link the antibody moiety to the drug moiety, either directly or indirectly. In some embodiments, the spacer unit links the antibody moiety to the drug moiety directly. In some embodiments, the antibody moiety and the drug moiety are attached via a spacer unit comprising one or more PEG moieties (e.g., (PEG)2or (PEG)4). In some embodiments, the spacer unit links the antibody moiety to the drug moiety indirectly. In some embodiments, the spacer unit links the antibody moiety to the drug moiety indirectly through a cleavable moiety (e.g., a cleavable peptide, a cleavable disulfide, or a cleavable sulfonamide) and / or an attachment moiety to join the spacer unit to the antibody moiety, e.g., a maleimide moiety.

[0233] The spacer unit, in various embodiments, attaches to the antibody moiety (i.e., the antibody or antigen-binding fragment) via a maleimide moiety (Mal). The term “maleimide moiety,” as used herein, means a compound that contains a maleimide group and that is reactive with a sulfhydryl group, e.g., a sulfhydryl group of a cysteine residue on the antibody moiety. Other functional groups that are reactive with sulfhydryl groups (thiols) include, but are not limited to, iodoacetamide, bromoacetamide, vinyl pyridine, disulfide, pyridyl disulfide, isocyanate, and isothiocyanate. In some embodiments, the Mal is reactive with a cysteine residue on the antibody or antigen-binding fragment. In some embodiments, the Mal is joined to the antibody or antigen-binding fragment via the cysteine residue.

[0234] In certain embodiments, the linker comprises a Mal moiety, a spacer unit, and a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the amino acid unit comprises Val-Cit. In some embodiments, the linker comprises the Mal, a spacer unit, and Val-Cit. In some embodiments, the linker comprises Mal-(PEG)2-Val-Cit. In some embodiments, the linker comprises Mal-(PEG)m-Val-Cit, where m is 2 to 8 or 2 to 5, or 2, 3, 4, or 5. In some embodiments, the linker comprises Mal-(PEG)8-Val-Cit. In some embodiments, the Mal- spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises MC-Val-Cit.

[0235] In some embodiments, the linker comprises the Mal, a spacer unit, and Val-Ala. In some embodiments, the linker comprises Mal-(PEG)2-Val-Ala. In some embodiments, the linker comprises Mal-(PEG)m-Val-Ala, where m is 2 to 8 or 2 to 5, or 2, 3, 4, or 5. In some embodiments, the linker comprises Mal-(PEG)8-Val-Ala. In some embodiments, the Mal-Attorney Docket No.15648.0054-00304 spacer unit comprises a maleimidocaproyl (MC). In some embodiments, the linker comprises MC-Val-Ala.

[0236] In various embodiments, the spacer unit attaches to the antibody or antigen-binding fragment via a succinimide moiety (OSu). The term “succinimide moiety,” as used herein, means a compound that contains a succinimide compound that is reactive with an amine group, e.g., an amine group of a lysine residue on the antibody moiety. An exemplary succinimide moiety is N-hydroxysuccinimide (NHS). In some embodiments, the OSu-spacer unit is reactive with a lysine residue on the antibody or antigen-binding fragment. In some embodiments, the OSu-spacer unit is joined to the antibody or antigen-binding fragment via the lysine residue.

[0237] In certain embodiments, the linker comprises an OSu, a spacer unit, and a cleavable peptide moiety. In some embodiments, the cleavable peptide moiety comprises an amino acid unit. In some embodiments, the amino acid unit comprises Val-Cit. In some embodiments, the linker comprises an OSu, a spacer unit, and Val-Cit. In some embodiments, the linker comprises OSu-(PEG)2-Val-Cit. In other embodiments, the linker comprises OSu- (PEG)9-Val-Cit. In other embodiments, the linker comprises OSu-(CH2)5-Val-Cit. In certain embodiments, the linker comprises OSu-(PEG)3-triazole-(PEG)3-Val-Cit.

[0238] In various embodiments, the cleavable moiety in the linker is joined directly to the payload moiety. In other embodiments, another spacer unit is used to attach the cleavable moiety in the linker to the payload moiety. In various embodiments, the payload moiety is eribulin. In various embodiments, the eribulin is attached to the cleavable moiety in the linker by a spacer unit. In some embodiments, the eribulin is attached to the cleavable moiety in the linker by a self-immolative spacer unit. In certain embodiments, the eribulin is attached to the cleavable moiety in the linker by a self-immolative spacer unit, the cleavable moiety comprises Val-Cit, and a further spacer unit comprising PEG joins the cleavable moiety to the antibody moiety. In certain embodiments, the eribulin is joined to an anti-FRA antibody via a Mal-spacer unit in the linker joined to a Val-Cit cleavable moiety and a pAB self- immolative spacer unit. In certain other embodiments, the eribulin is joined to an anti-MSLN antibody via a Mal-spacer unit in the linker joined to a Val-Cit cleavable moiety and a pAB self-immolative spacer unit.

[0239] A spacer unit may be “self-immolative” or “non-self-immolative.” A “non-self- immolative” spacer unit is one in which part or all of the spacer unit remains bound to theAttorney Docket No.15648.0054-00304 drug moiety upon cleavage of the linker. Examples of non-self-immolative spacer units include, but are not limited to, a glycine spacer unit and a glycine-glycine spacer unit. Non- self-immolative spacer units may eventually degrade over time but do not readily release a linked native drug entirely under cellular conditions. A “self-immolative” spacer unit allows for release of the native drug moiety under intracellular conditions. A “native drug” is one where no part of the spacer unit or other chemical modification remains after cleavage / degradation of the spacer unit.

[0240] Self-immolation chemistry is known in the art and could be readily selected for the disclosed linkers and / or ADCs. In various embodiments, the spacer unit attaching the cleavable moiety in the linker to the drug moiety (e.g., eribulin) is self-immolative, and undergoes self-immolation concurrently with or shortly before / after cleavage of the cleavable moiety under intracellular conditions.

[0241] In certain embodiments, the self-immolative spacer unit in the linker comprises a p-aminobenzyl unit. In some embodiments, a p-aminobenzyl alcohol (pABOH) is attached to an amino acid unit or other cleavable moiety in the linker via an amide bond, and a carbamate, methylcarbamate, or carbonate is made between the pABOH and the drug moiety (Hamann et al. (2005) Expert Opin. Ther. Patents 15:1087-103). In some embodiments, the self-immolative spacer unit is or comprises p-aminobenzyloxycarbonyl (pAB). Without being bound by theory, it is thought that the self-immolation of pAB involves a spontaneous 1,6- elimination reaction (Jain et al. (2015) Pharm Res 32:3526-40).

[0242] In various embodiments, the structure of the p-aminobenzyloxycarbonyl (pAB) used in the disclosed ADCs is shown below:

[0243] In various embodiments, the self-immolative spacer unit attaches the cleavable moiety in the linker to the C-35 amine on eribulin. In some embodiments, the self-immolative spacer unit is pAB. In some embodiments, the pAB attaches the cleavable moiety in the linker to the C-35 amine on eribulin. In some embodiments, the pAB undergoes self- immolation upon cleavage of the cleavable moiety, and eribulin is released from the ADC inAttorney Docket No.15648.0054-00304 its native, active form. In some embodiments, an anti-FRA antibody (e.g., MORAb-003) is joined to the C-35 amine of eribulin by a linker comprising Mal-(PEG)2-Val-Cit-pAB. In other embodiments, an anti-MSLN antibody (e.g., 345A12) is joined to the C-35 amine of eribulin by a linker comprising Mal-(PEG)2-Val-Cit-pAB. In some embodiments, an anti- FRA antibody (e.g., MORAb-003) is joined to the C-35 amine of eribulin by a linker comprising MC-Val-Cit-pAB. In other embodiments, an anti-MSLN antibody (e.g., 345A12) is joined to the C-35 amine of eribulin by a linker comprising MC-Val-Cit-pAB. In other embodiments, an anti-HER2 antibody (e.g., trastuzumab) is joined to the C-35 amine of eribulin by a linker comprising MC-Val-Cit-pAB.

[0244] In some embodiments, an anti-FRA antibody (e.g., MORAb-003) is joined to the C-35 amine of eribulin by a linker comprising Mal-(PEG)2-Val-Ala-pAB. In other embodiments, an anti-MSLN antibody (e.g., 345A12) is joined to the C-35 amine of eribulin by a linker comprising Mal-(PEG)2-Val-Ala-pAB. In other embodiments, an anti-HER2 antibody (e.g., trastuzumab) is joined to the C-35 amine of eribulin by a linker comprising Mal-(PEG)2-Val-Ala-pAB. In some embodiments, an anti-FRA antibody (e.g., MORAb-003) is joined to the C-35 amine of eribulin by a linker comprising MC-Val-Ala-pAB. In other embodiments, an anti-MSLN antibody (e.g., 345A12) is joined to the C-35 amine of eribulin by a linker comprising MC-Val-Ala-pAB. In other embodiments, an anti-HER2 antibody (e.g., trastuzumab) is joined to the C-35 amine of eribulin by a linker comprising MC-Val- Ala-pAB.

[0245] In various aspects, the antibody moiety of the ADC is conjugated to the drug moiety via a linker, wherein the linker comprises a Mal-spacer unit, a cleavable amino acid unit, and a pAB. In some embodiments, the spacer unit comprises a PEG moiety. In some embodiments, the spacer unit comprises an alkyl moiety. In some embodiments, the linker comprises Mal-(PEG)2-Val-Cit-pAB. In some embodiments, the linker comprises Mal- (PEG)8-Val-Cit-pAB. In some embodiments, the linker comprises Mal-(CH2)5-Val-Cit-pAB.

[0246] In some aspects, the antibody moiety of the ADC is conjugated to the drug moiety via a linker, wherein the linker comprises OSu-spacer unit-amino acid unit-pAB. In some embodiments, the spacer unit comprises a PEG moiety. In some embodiments, the spacer unit comprises an alkyl moiety. In some embodiments, the linker comprises OSu-(PEG)2-amino acid unit-pAB. In some embodiments, the linker comprises OSu-(PEG)2-Val-Cit-pAB. In some embodiments, the linker comprises OSu-(PEG)9-Val-Cit-pAB. In some embodiments,Attorney Docket No.15648.0054-00304 the linker comprises OSu-(CH2)5-Val-Cit-pAB. In some embodiments, the linker comprises OSu-(PEG)3-triazole-(PEG)3-Val-Cit-pAB.

[0247] In some embodiments, an anti-VCP antibody disclosed herein specifically binds a linker comprising VCP. In some embodiments, an anti-VCP antibody disclosed herein specifically binds a linker conjugate comprising Mal-(PEG)m-VCP. In some embodiments, an anti-VCP antibody disclosed herein specifically binds a linker conjugate comprising Mal- (PEG)2-VCP. In some embodiments, an anti-VCP antibody disclosed herein specifically binds a linker-payload conjugate comprising VCP. In some embodiments, an anti-VCP antibody disclosed herein specifically binds a linker-payload conjugate comprising VCP- eribulin. In some embodiments, an anti-VCP antibody disclosed herein specifically binds a linker-payload conjugate comprising Mal-(PEG)m-VCP-eribulin. In some embodiments, an anti-VCP antibody disclosed herein specifically binds a linker-payload conjugate comprising Mal-(PEG)2-VCP-eribulin.

[0248] Exemplary linkers and linker-payload conjugates are shown below in Table 22. Table 22. Exemplary Linker-Payload CompoundsAttorney Docket No.15648.0054-00304

[0009] n var ous embod men s, an - n er an bodes or an gen-bnd ng ragmen s may be designed as taught herein to specifically bind linkers or linker-payload conjugates comprising an alternative (e.g., non-VCP) cleavable or non-cleavable linker moiety. Alternative linker moieties are known in the art. Exemplary cleavable linker moieties include, for example, a disulfide moiety, a sulfonamide moiety, or an amino acid unit. Exemplary amino acid units include, but are not limited to, dipeptides, tripeptides, tetrapeptides, and pentapeptides. Exemplary dipeptides include, but are not limited to, valine-citrulline (Val- Cit), alanine-asparagine (Ala-Asn), alanine-phenylalanine (Ala-Phe), phenylalanine-lysine (Phe-Lys), alanine-lysine (Ala-Lys), alanine-valine (Ala-Val), valine-alanine (Val-Ala), valine-lysine (Val-Lys), lysine-lysine (Lys-Lys), phenylalanine-citrulline (Phe-Cit), leucine- citrulline (Leu-Cit), isoleucine-citrulline (Ile-Cit), tryptophan-citrulline (Trp-Cit), and phenylalanine-alanine (Phe-Ala). Exemplary tripeptides include, but are not limited to, alanine-alanine-asparagine (Ala-Ala-Asn), glycine-valine-citrulline (Gly-Val-Cit), glycine- glycine-glycine (Gly-Gly-Gly), phenylalanine-phenylalanine-lysine (Phe-Phe-Lys), and glycine-phenylalanine-lysine (Gly-Phe-Lys). Other exemplary amino acid units include, butAttorney Docket No.15648.0054-00304 are not limited to, Gly-Phe-Leu-Gly, Ala-Leu-Ala-Leu, Phe-N9-tosyl-Arg, and Phe-N9-Nitro- Arg, as described in, e.g., U.S. Pat. No.6,214,345. In some embodiments, the linker or linker- payload comprises a cleavable amino acid unit and eribulin. Anti-VCP Antibodies and Antigen-Binding Fragments

[0250] The present disclosure also provides antibodies or antigen-binding fragments thereof that specifically bind a linker or a linker-payload conjugate comprising VCP, e.g., which may be used in any of the assays disclosed herein. An anti-VCP antibody may bind the linker by binding an epitope on the linker. Alternatively, an anti-VCP antibody may bind an epitope formed from the linker-payload but not present in the linker alone.

[0251] The antibodies or antigen binding fragments disclosed herein that specifically bind VCP may comprise three HC CDRs (HCDR1, HCDR2, and HCDR3) having amino acid sequences selected from the HC CDRs listed in Table 23, infra, as defined by the Kabat numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) having amino acid sequences selected from the LC CDRs listed in Table 23, infra, as defined by the Kabat numbering system. In some embodiments, the anti-VCP antibodies comprise three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) having amino acid sequences selected from the HC CDRs listed in Table 24, infra, as defined by the IMGT numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) having amino acid sequences selected from the LC CDRs listed in Table 24, infra, as defined by the IMGT numbering system.

[0252] In some embodiments, an anti-VCP antibody disclosed herein comprises a VH domain having an amino acid sequence selected from SEQ ID NOs: 45 and 248 listed in Table 25, infra. In some embodiments, the antibody comprises a VL domain having an amino acid sequence selected from SEQ ID NOs: 46 and 249 listed in Table 25, infra.

[0253] In some embodiments, an antigen-binding fragment disclosed herein is a variant that retains VCP binding. In some embodiments, the antigen-binding fragment retains VCP binding by comprising three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) comprising amino acid sequences selected from the HC CDRs listed in Table 23, infra, as defined by the Kabat numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) comprising amino acid sequences selected from the LC CDRs listed in Table 23, infra, as defined by the Kabat numbering system. In some embodiments, the antigen-binding fragment comprises three heavy chain CDRs (HCDR1, HCDR2, and HCDR3) comprising amino acidAttorney Docket No.15648.0054-00304 sequences selected from the HC CDRs listed in Table 24, infra, as defined by the IMGT numbering system, and three light chain CDRs (LCDR1, LCDR2, and LCDR3) comprising amino acid sequences selected from the LC CDRs listed in Table 24, infra, as defined by the IMGT numbering system. In some embodiments, the antigen-binding fragments disclosed herein may retain VCP binding by comprising a VH domain comprising an amino acid sequence selected from SEQ ID NOs: 45 and 248 listed in Table 25, infra, and a VL domain comprising an amino acid sequence selected from SEQ ID NOs: 46 and 249 listed in Table 25, infra.

[0254] In some embodiments, an anti-VCP antibody or antigen-binding fragment further comprises human heavy and light chain frameworks (optionally with one or more backmutations to improve binding affinity) and / or human heavy and light chain constant domains or fragments thereof. For instance, the antibody or antigen-binding fragment may comprise a human IgG heavy chain constant domain (such as an IgG1) and a human kappa or lambda light chain constant domain. In some embodiments, the antibody or antigen-binding fragment comprises a human IgG1 heavy chain constant domain with a human Ig kappa light chain constant domain.

[0255] In some embodiments, an antibody that specifically binds VCP comprises a heavy chain having an amino acid sequence selected from SEQ ID NOs: 47 and 250 listed in Table 26, infra. In some embodiments, an antibody that specifically binds VCP comprises a light chain having an amino acid sequence selected from SEQ ID NOs: 48 and 251 listed in Table 26, infra.

[0256] Amino acid and nucleic acid sequences of exemplary anti-VCP antibodies of the present disclosure are set forth in Tables 23-27. Table 23. Amino acid sequences of Kabat CDRs for anti-VCP antibodies mAb IgG chain SEQ ID Amino acid sequenceAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence 6O11 HC CDR1 159SSYWICmAb IgG chain SEQ ID Amino acid sequence 11G6 HC CDR1 39GIDLSYYGTable 25. Amino acid sequences of variable regions for anti-VCP antibodies mAb IgG chain SEQ ID Amino acid sequence V S Y W T KAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence 6O11VH248QSLEESGGDLVKPGASLTLTCTASGFSFSSSYWICWVS G Q TmAb IgG chain SEQ ID Amino acid sequence 11G6 Heavy chain 47QEQLVESGGGLVQPGESLKLSCKVSGIDLSYYGVSWVS Y T S K T A S N L H W T K A LAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Amino acid sequence 6O11 Heavy chain 250QSLEESGGDLVKPGASLTLTCTASGFSFSSSYWICWVS G K S D E Q I V L L Q T R K SmAb IgG chain SEQ ID Nucleic acid sequence AAAT TC TG TT GT AC CC CC CC TG GC TC TT CAAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence CCTGAACTCCTGGGGGGACCGTCAGTCTTCCTCTTCCCCCCAAAACCC TG TG AG AG CC CC CC GC AC AT TC AG GAAC TC TC TG GT GA AG AT CG CC AA CC CCAC TC TG TG CG CC CC GC ACAttorney Docket No.15648.0054-00304 mAb IgG chain SEQ ID Nucleic acid sequence TCAGGCGCCCTGACCAGCGGCGTGCACACCTTCCCGGCTGTCCTACAG GC GC CT CA GG CT CC TC AC CC TG GC GC AC GC CT AA GAAC TC GC GT GT CT TG CC GT AC AC TCso e e o e s, e sequeces o e eay ca a a e o a s, g chain variable domains, full-length heavy chains, and full-length light chains may be “mixed and matched” to create variants of the anti-VCP antibodies. Such “mixed and matched” anti- VCP antibodies can be tested using binding assays known in the art (e.g., ELISAs and otherAttorney Docket No.15648.0054-00304 assays described in the Examples). In various embodiments, an anti-VCP antibody or antigen binding fragment disclosed herein may comprise any set of heavy and light chain variable domains listed in Table 25 above, or the set of six CDR sequences from the heavy and light chain set. In some embodiments, an antibody or antigen-binding fragment further comprise human heavy and light chain constant domains or fragments thereof. In some embodiments, an anti-VCP antibody may comprise a human IgG heavy chain constant domain and a human kappa light chain constant domain. In some embodiments, the anti-VCP antibody may comprise a human IgG1, IgG2, IgG3, or IgG4 heavy chain constant domain. In various embodiments, an anti-VCP antibody of the present invention comprises a human immunoglobulin G subtype 1 (IgG1) heavy chain constant domain with a human Ig kappa light chain constant domain. In various embodiments, an anti-VCP antibody may comprise any set of full-length heavy chain and full-length light chain sequences listed in Table 26 above.

[0258] In some embodiments, an anti-VCP antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 33 (HCDR1), SEQ ID NO: 34 (HCDR2), and SEQ ID NO: 35 (HCDR3); and three LCDRs comprising SEQ ID NO: 36 (LCDR1), SEQ ID NO: 37 (LCDR2), and SEQ ID NO: 38 (LCDR3) as defined by the Kabat numbering system.

[0259] In some embodiments, an anti-VCP antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 39 (HCDR1), SEQ ID NO: 40 (HCDR2), and SEQ ID NO: 41 (HCDR3); and three LCDRs comprising SEQ ID NO: 42 (LCDR1), SEQ ID NO: 43 (LCDR2), and SEQ ID NO: 38 (LCDR3) as defined by the IMGT numbering system.

[0260] In some embodiments, an anti-VCP antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 159 (HCDR1), SEQ ID NO: 240 (HCDR2), and SEQ ID NO: 241 (HCDR3); and three LCDRs comprising SEQ ID NO: 242 (LCDR1), SEQ ID NO: 209 (LCDR2), and SEQ ID NO: 243 (LCDR3) as defined by the Kabat numbering system.

[0261] In some embodiments, an anti-VCP antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 164 (HCDR1), SEQ ID NO: 244 (HCDR2), and SEQ ID NO: 245 (HCDR3); and three LCDRs comprisingAttorney Docket No.15648.0054-00304 SEQ ID NO: 246 (LCDR1), SEQ ID NO: 215 (LCDR2), and SEQ ID NO: 243 (LCDR3) as defined by the IMGT numbering system.

[0262] In some embodiments, an anti-VCP antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 45, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 46.

[0263] In some embodiments, an anti-VCP antibody or antigen-binding fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 248, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 249.

[0264] In some embodiments, an anti-VCP antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 45, and three LCDRs from the light chain variable region comprising SEQ ID NO: 46. In some embodiments, an anti-VCP antibody or antigen-binding fragment thereof provided herein comprises three HCDRs from the heavy chain variable region comprising SEQ ID NO: 248, and three LCDRs from the light chain variable region comprising SEQ ID NO: 249.

[0265] In some embodiments, an anti-VCP antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 45. In some embodiments, an anti-VCP antibody or antigen-binding fragment thereof provided herein comprises a heavy chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 248.

[0266] In some embodiments, an anti-VCP antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 46. In some embodiments, an anti-eribulin antibody or antigen-binding fragment thereof provided herein comprises a light chain variable region with at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, atAttorney Docket No.15648.0054-00304 least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 249.

[0267] In various embodiments, an anti-VCP antibody comprises a human IgG heavy chain constant domain. In some embodiments, the IgG heavy chain constant domain is IgG1.

[0268] In various embodiments, an anti-VCP antibody comprise a human Ig kappa light chain constant region. In various embodiments, the anti-VCP antibody comprise a human Ig lambda light chain constant region.

[0269] In some embodiments, an anti-VCP antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 47. In some embodiments, an anti-VCP antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 48.

[0270] In some embodiments, an anti-eribulin antibody or antigen-binding fragment provided herein comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 250. In some embodiments, an anti-VCP antibody or antigen-binding fragment thereof provided herein comprises a light chain comprising an amino acid sequence of SEQ ID NO: 251.

[0271] In some embodiments, an anti-VCP antibody or antigen-binding fragment provided herein is antibody 11G6.

[0272] In some embodiments, an anti-VCP antibody or antigen-binding fragment provided herein is conjugated to a label. In some embodiments, the anti-VCP antibody or antigen- binding fragment is conjugated to a fluorescent tag. In some embodiments, the anti-VCP antibody or antigen-binding fragment is conjugated to a biotin moiety. In some embodiments, the anti-VCP antibody or antigen-binding fragment is conjugated to a streptavidin moiety. In some embodiments, the anti-VCP antibody or antigen-binding fragment is conjugated to an enzyme reporter. In some embodiments, the anti-VCP antibody or antigen-binding fragment is conjugated to a bead. In some embodiments, the bead is an agarose bead or a magnetic bead. In some embodiments, the anti-VCP antibody or antigen-binding fragment is conjugated to a luminescent tag. In some embodiments, the anti-VCP antibody or antigen- binding fragment is conjugated to an electrochemiluminescent tag.

[0273] In some embodiments, an anti-VCP antibody or antigen-binding fragment provided herein is conjugated to a fluorescent tag.Attorney Docket No.15648.0054-00304

[0274] In some embodiments, an anti-VCP antibody or antigen-binding fragment provided herein is conjugated to a luminescent tag.

[0275] In some embodiments, an anti-VCP antibody or antigen-binding fragment provided herein is conjugated to an electrochemiluminescent tag.

[0276] In some embodiments, an anti-VCP antibody or antigen binding fragment specifically binds a linker-payload conjugate comprising VCP. In some embodiments, an anti-VCP antibody or antigen binding fragment specifically binds a linker-payload conjugate comprising VCP-eribulin. In some embodiments, an anti-VCP antibody or antigen binding fragment specifically binds a linker-payload conjugate comprising Mal-(PEG)m-VCP- eribulin, wherein m is an integer from 1 to 10. In some embodiments, the linker-payload conjugate comprises Mal-(PEG)2-VCP-eribulin. Methods For Detecting Antibody-Drug Conjugate Metabolites

[0277] In designing efficacious ADC therapies, it is beneficial to evaluate the clinical pharmacology of the ADC, including quantifying the ADC and its constituent parts in circulation after administration of an ADC to a subject. In some embodiments, an ADC administered to a subject may release metabolites in circulation.

[0278] An ADC may metabolize in circulation via a variety of pathways (FIG.1). Exemplary ADC metabolites include an antibody or antigen-binding fragment, linker-payload conjugate, linker-payload conjugated to albumin, free payload, and linker unconjugated to either ADC or payload. Accurate measurement of pharmacologically active metabolites in systemic circulation may inform exposure-response analyses. Such analyses may assist in evaluating efficacious dose selection in a subject or likelihood of side effects from dosing.

[0279] The methods disclosed herein describe novel antibodies, as well as immunodepletion methods for quantifying ADC metabolites. To quantify potential ADC metabolites, an assay or assays may measure one or more of free payload, total ADC and / or antibody or antigen-binding fragment, intact ADC, and linker-payload conjugate. In some embodiments, a method disclosed herein measures intact ADC in a DAR-insensitive manner. In some embodiments, a method disclosed herein measures intact ADC in a DAR-sensitive manner.

[0280] In some embodiments, the methods disclosed herein are performed using a biological sample obtained from a subject. In some embodiments, the biological sampleAttorney Docket No.15648.0054-00304 comprises whole blood, plasma, and / or serum. In some embodiments, the biological sample comprises plasma.

[0281] In some embodiments, the biological sample used in any assay described herein is obtained from a subject after administration of an ADC. In some embodiments, the ADC comprises an anti-FRA antibody or antigen-binding fragment. In some embodiments, the ADC comprises farletuzumab. In some embodiments, the ADC comprises MORAb-202. In some embodiments, the ADC comprises an anti-MSLN antibody or antigen-binding fragment. In some embodiments, the ADC comprises 345A12. In some embodiments, the ADC comprises MORAb-109. In some embodiments, the ADC comprises an anti-HER2 antibody or antigen-binding fragment. In some embodiments, the ADC comprises trastuzumab.

[0282] In some embodiments, the methods disclosed herein comprise an immunoassay. In some embodiments, the immunoassay comprises an antibody conjugated to a label. Methods for conjugating labels to an antibody are known in the art and include, for example, covalent attachment of the label to an antibody (e.g., using succinimide, e.g., NHS, conjugation to lysine, maleimide conjugation to cysteine, or click chemistry to introduce azide or alkyne structures). In some embodiments, the label comprises a streptavidin or bead. In some embodiments, the antibody is immobilized on a solid support. In some embodiments, the label is detectable. In some embodiments, the method comprises detecting a signal from a labeled antibody. “Detecting a signal” may comprises quantifying information from a detectably labeled antibody using any method known in the art. Exemplary signals include fluorescence, luminescence, or electrochemiluminescence. Exemplary detection methods include microfluidic immunoassay detection (e.g., Gyros xPand), flow cytometry, spectrophotometry, and fluorescence microscopy. Any method known in the art for translating signal data into quantification of a target may be used, including reference to standards.

[0283] In various embodiments, disclosed herein are methods for detecting a metabolite of an antibody-drug conjugate. Further details regarding assays for measuring ADC metabolites are enumerated below.Attorney Docket No.15648.0054-00304 Quantifying Free Payload

[0284] In some embodiments, a method for detecting a metabolite of an ADC comprises an assay to quantify free payload. In some embodiments, free payload in a biological sample is quantified. In some embodiments, the biological sample is plasma. Methods for quantifying free payload are known in the art and include, for example, solid phase extraction followed by liquid-chromatography / mass spectrometry or multiple reaction monitoring.

[0285] In some embodiments, the free payload is eribulin. In some embodiments, the eribulin is quantified in a plasma sample from a subject administered an ADC. In some embodiments, the ADC comprises an anti-FRA antibody or antigen-binding fragment. In some embodiments, the ADC comprises farletuzumab. In some embodiments, the ADC comprises MORAb-202. In some embodiments, the ADC comprises an anti-MSLN antibody or antigen-binding fragment. In some embodiments, the ADC comprises 345A12. In some embodiments, the ADC comprises MORAb-109. In some embodiments, the ADC comprises an anti-HER2 antibody or antigen-binding fragment. In some embodiments, the ADC comprises trastuzumab.

[0286] In some embodiments, the limit of quantification (LOQ) of eribulin in a plasma sample is at least 5 pg / ml, at least 10 pg / ml, at least 15 pg / ml, at least 20 pg / ml, at least 25 pg / ml, or at least 30 pg / ml as determined by multiple reaction monitoring (MRM). In some embodiments, the LOQ of eribulin in a plasma sample is at least 10 pg / ml as determined by MRM. Quantifying Total Antibody / ADC

[0287] In some embodiments, a method for detecting a metabolite of an ADC comprises an assay to quantify total ADC and / or antibody or antigen-binding fragment. In some embodiments, total ADC and / or antibody or antigen-binding fragment is quantified in a biological sample. In some embodiments, the biological sample is plasma. In some embodiments, total ADC and / or antibody or antigen-binding fragment in sample is quantified using an anti-idiotype antibody, e.g., an anti-idiotypic antibody against an FRA, MSLN, or HER2 antibody or antigen binding fragment (also referred to herein as an anti-FRA idiotypic antibody or antigen-binding fragment, anti-MSLN idiotypic antibody or antigen-binding fragment, or anti-HER2 idiotypic antibody or antigen-binding fragment).

[0288] Methods for quantifying total ADC and / or antibody or antigen-binding fragment concentration are known in the art and include, for example, a sandwich immunoassay, e.g.,Attorney Docket No.15648.0054-00304 ELISA, fluorescence, luminescence, and electrochemiluminescence. An exemplary method disclosed herein quantifies total ADC and / or antibody or antigen-binding fragment using fluorescent detection in a sandwich immunoassay. Sandwich immunoassays are known in the art and comprise a first step wherein an antigen is captured by a first antibody immobilized on a fixed surface, and a second step wherein the antigen is detected by binding with a second antibody conjugated to a detectable label.

[0289] In some embodiments, the sandwich immunoassay comprises a first antibody (“capture antibody”) and a second antibody (“detection antibody”). In some embodiments, the capture antibody is biotinylated. In some embodiments, the detection antibody is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent label.

[0290] In some embodiments, the assay quantifies total ADC and / or antibody or antigen- binding fragment, wherein the ADC and / or antibody or antigen-binding fragment specifically bind folate receptor alpha. In some embodiments, the ADC is MORAb-202. In some embodiments, the antibody is farletuzumab or an antigen-binding fragment thereof. In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 49, HCDR2 comprising SEQ ID NO: 50, HCDR3 comprising SEQ ID NO: 51; LCDR1 comprising SEQ ID NO: 52, LCDR2 comprising SEQ ID NO: 53, and LCDR3 comprising SEQ ID NO: 54, as defined by the Kabat numbering system. In some embodiments, the antibody or antigen- binding fragment comprises three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 55, HCDR2 comprising SEQ ID NO: 56, HCDR3 comprising SEQ ID NO: 57; LCDR1 comprising SEQ ID NO: 58, LCDR2 comprising SEQ ID NO: 59, and LCDR3 comprising SEQ ID NO: 60, as defined by the IMGT numbering system. In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain variable domain comprising a sequence of SEQ ID NO: 61 and a light chain variable domain comprising a sequence of SEQ ID NO: 62. In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain of SEQ ID NO: 63 and a light chain sequence of SEQ ID NO: 64.

[0291] In some embodiments, the capture antibody or antigen-binding fragment is an anti- FRA idiotypic antibody or antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is an anti-farletuzumab antibody or antigen-bindingAttorney Docket No.15648.0054-00304 fragment. In some embodiments, the capture antibody or antigen-binding fragment is 2G9. In some embodiments, the capture antibody is an antigen-binding Fab fragment, e.g., a Fab fragment of 2G9. In some embodiments, the capture antibody is a Fab2 antigen-binding fragment. In some embodiments, the capture antibody is biotinylated. In some embodiments the capture antibody is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the detection antibody or antigen- binding fragment is an anti-farletuzumab antibody or antigen-binding fragment. In some embodiments, the detection antibody or antigen-binding fragment is 2G9. In some embodiments, the detection antibody or antigen-binding fragment is an anti-FRA idiotypic antibody or antigen-binding fragment. In some embodiments, the detection antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody is conjugated to a fluorescent tag.

[0292] In some embodiments, the assay quantifies total ADC and / or antibody or antigen- binding fragment, wherein the ADC and / or antibody or antigen-binding fragment specifically binds mesothelin. In some embodiments, the ADC is MORAb-109. In some embodiments, the antibody is 345A12 or an antigen-binding fragment thereof. In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 65, HCDR2 comprising SEQ ID NO: 66, HCDR3 comprising SEQ ID NO: 67; LCDR1 comprising SEQ ID NO: 68, LCDR2 comprising SEQ ID NO: 69, and LCDR3 comprising SEQ ID NO: 70, as defined by the Kabat numbering system. In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 71, HCDR2 comprising SEQ ID NO: 72, HCDR3 comprising SEQ ID NO: 73; LCDR1 comprising SEQ ID NO: 74, LCDR2 comprising SEQ ID NO: 75, and LCDR3 comprising SEQ ID NO: 76, as defined by the IMGT numbering system. In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain variable domain comprising a sequence of SEQ ID NO: 77 and a light chain variable domain comprising a sequence of SEQ ID NO: 78. In some embodiments, the antibody or antigen- binding fragment comprises a heavy chain of SEQ ID NO: 79 and a light chain sequence of SEQ ID NO: 80.Attorney Docket No.15648.0054-00304

[0293] In some embodiments, the capture antibody or antigen-binding fragment is an anti- MSLN idiotypic antibody or antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is an anti-345A12 antibody or antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is an antigen-binding Fab fragment. In some embodiments, the capture antibody or antigen-binding fragment is a Fab2 antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is biotinylated. In some embodiments, the capture antibody is immobilized on a solid support. In some embodiments, the detection antibody or antigen- binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the detection antibody or antigen-binding fragment is an anti- 345A12 antibody or antigen-binding fragment. In some embodiments, the detection antibody or antigen-binding fragment is an anti-MSLN idiotypic antibody or antigen-binding fragment. In some embodiments, the detection antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody is conjugated to a fluorescent tag.

[0294] In some embodiments, the assay quantifies total ADC and / or antibody or antigen- binding fragment, wherein the ADC and / or antibody or antigen-binding fragment specifically binds HER2. In some embodiments, the antibody is trastuzumab or an antigen-binding fragment thereof. In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 254, HCDR2 comprising SEQ ID NO: 255, HCDR3 comprising SEQ ID NO: 256; LCDR1 comprising SEQ ID NO: 257, LCDR2 comprising SEQ ID NO: 258, and LCDR3 comprising SEQ ID NO: 259, as defined by the Kabat numbering system. In some embodiments, the antibody or antigen-binding fragment comprises three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 260, HCDR2 comprising SEQ ID NO: 261, HCDR3 comprising SEQ ID NO: 262; LCDR1 comprising SEQ ID NO: 263, LCDR2 comprising SEQ ID NO: 264, and LCDR3 comprising SEQ ID NO: 265, as defined by the IMGT numbering system. In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain variable domain comprising a sequence of SEQ ID NO: 266 and a light chain variable domain comprising a sequence of SEQ ID NO:Attorney Docket No.15648.0054-00304 267. In some embodiments, the antibody or antigen-binding fragment comprises a heavy chain of SEQ ID NO: 268 and a light chain sequence of SEQ ID NO: 269.

[0295] In some embodiments, the capture antibody or antigen-binding fragment is an anti- HER2 idiotypic antibody or antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is an anti-trastuzumab antibody or antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is an antigen-binding Fab fragment, e.g., an anti-trastuzumab antigen-binding Fab fragment. In some embodiments, the capture antibody or antigen-binding fragment is a Fab2 antigen- binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is biotinylated. In some embodiments, the capture antibody is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-HER2 idiotypic antibody or antigen-binding fragment. In some embodiments, the detection antibody is an anti-trastuzumab antibody or antigen-binding fragment. In some embodiments, the detection antibody or antigen-binding fragment is an antigen-binding Fab fragment. In some embodiments, the detection antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is conjugated to a fluorescent tag. Quantifying Intact ADC (DAR insensitive and DAR sensitive)

[0296] In some embodiments, a method for detecting a metabolite of an ADC comprises an assay to quantify intact ADC. In some embodiments, intact ADC is quantified in a biological sample. In some embodiments, the biological sample is plasma. In some embodiments, the assay is a sandwich immunoassay. An exemplary method disclosed herein quantifies intact ADC using fluorescent detection in a sandwich immunoassay.

[0297] In some embodiments, the sandwich immunoassay comprises a first antibody (“capture antibody”) and a second antibody (“detection antibody”). In some embodiments, the capture antibody is biotinylated. In some embodiments, the detection antibody is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent label.

[0298] In some embodiments, the intact ADC assay quantifies an intact ADC, wherein the ADC specifically binds FRA. In some embodiments, the intact ADC is MORAb-202. In some embodiments, the intact ADC comprises farletuzumab or an antigen-binding fragmentAttorney Docket No.15648.0054-00304 thereof. In some embodiments, the intact ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 49, HCDR2 comprising SEQ ID NO: 50, HCDR3 comprising SEQ ID NO: 51; LCDR1 comprising SEQ ID NO: 52, LCDR2 comprising SEQ ID NO: 53, and LCDR3 comprising SEQ ID NO: 54, as defined by the Kabat numbering system. In some embodiments, the intact ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 55, HCDR2 comprising SEQ ID NO: 56, HCDR3 comprising SEQ ID NO: 57; LCDR1 comprising SEQ ID NO: 58, LCDR2 comprising SEQ ID NO: 59, and LCDR3 comprising SEQ ID NO: 60, as defined by the IMGT numbering system. In some embodiments, the intact ADC comprises an antibody comprising a heavy chain variable domain comprising a sequence of SEQ ID NO: 61 and a light chain variable domain comprising a sequence of SEQ ID NO: 62. In some embodiments, the intact ADC comprises an antibody comprising a heavy chain of SEQ ID NO: 63 and a light chain sequence of SEQ ID NO: 64. In some embodiments, the intact ADC has a DAR of 4. In some embodiments, the intact ADC has a DAR of 2.

[0299] In some embodiments, the intact ADC assay quantifies an intact ADC, wherein the ADC specifically binds MSLN. In some embodiments, the intact ADC is MORAb-109. In some embodiments, the intact ADC comprises 345A12 or an antigen-binding fragment thereof. In some embodiments, the intact ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 65, HCDR2 comprising SEQ ID NO: 66, HCDR3 comprising SEQ ID NO: 67; LCDR1 comprising SEQ ID NO: 68, LCDR2 comprising SEQ ID NO: 69, and LCDR3 comprising SEQ ID NO: 70, as defined by the Kabat numbering system. In some embodiments, the intact ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 71, HCDR2 comprising SEQ ID NO: 72, HCDR3 comprising SEQ ID NO: 73; LCDR1 comprising SEQ ID NO: 74, LCDR2 comprising SEQ ID NO: 75, and LCDR3 comprising SEQ ID NO: 76, as defined by the IMGT numbering system. In some embodiments, the intact ADC comprises an antibody comprising a heavy chain variable domain comprising a sequence of SEQ ID NO: 77 and a light chain variable domain comprising a sequence of SEQ ID NO: 78. In some embodiments, the intact ADC comprises an antibody comprising a heavy chain of SEQ IDAttorney Docket No.15648.0054-00304 NO: 79 and a light chain sequence of SEQ ID NO: 80. In some embodiments, the intact ADC has a DAR of 4. In some embodiments, the intact ADC has a DAR of 2.

[0300] In some embodiments, the intact ADC assay quantifies an intact ADC, wherein the ADC specifically binds HER2. In some embodiments, the intact ADC comprises trastuzumab or an antigen-binding fragment thereof. In some embodiments, the intact ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 254, HCDR2 comprising SEQ ID NO: 255, HCDR3 comprising SEQ ID NO: 256; LCDR1 comprising SEQ ID NO: 257, LCDR2 comprising SEQ ID NO: 258, and LCDR3 comprising SEQ ID NO: 259, as defined by the Kabat numbering system. In some embodiments, the intact ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 260, HCDR2 comprising SEQ ID NO: 261, HCDR3 comprising SEQ ID NO: 262; LCDR1 comprising SEQ ID NO: 263, LCDR2 comprising SEQ ID NO: 264, and LCDR3 comprising SEQ ID NO: 265, as defined by the IMGT numbering system. In some embodiments, the intact ADC comprises an antibody comprising a heavy chain variable domain comprising a sequence of SEQ ID NO: 266 and a light chain variable domain comprising a sequence of SEQ ID NO: 267. In some embodiments, the intact ADC comprises an antibody comprising a heavy chain of SEQ ID NO: 268 and a light chain sequence of SEQ ID NO: 269. In some embodiments, the intact ADC has a DAR of 4. In some embodiments, the intact ADC has a DAR of 2.

[0301] In various embodiments, the intact ADC assay is DAR insensitive. In some embodiments, a capture antibody or antigen-binding fragment in a DAR insensitive assay is an anti-eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the capture antibody or antigen-binding fragment is 5E4. In some embodiments, the capture antibody or antigen-binding fragment is an antigen-binding fragment. In some embodiments, the capture antigen-binding fragment is a Fab fragment. In some embodiments, the capture antibody or antigen-binding fragment is biotinylated. In some embodiments, the capture antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti- ID antibody or antigen-binding fragment. In some embodiments, the detection antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the detection antibody or antigen-binding fragment isAttorney Docket No.15648.0054-00304 conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0302] In some embodiments, a method for detecting intact ADC in a DAR insensitive manner is provided herein. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered an ADC. In some embodiments, the method further comprises contacting the biological sample with 5E4. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is biotinylated. In some embodiments, 5E4 is immobilized on a solid support. In some embodiments, the method further comprises contacting the biological sample with an anti-ID antibody or antigen-binding fragment or with an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment and / or the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a detectable label, e.g., a fluorescent tag. In some embodiments, a signal from the detectable label is detected for quantification of the intact ADC. In some embodiments, the anti-ID antibody is 2G9 or an antigen-binding fragment thereof. In some embodiments, the anti-ID antibody is an anti- 345A12 idiotypic antibody or antigen-binding fragment thereof. In some embodiments, the intact ADC is MORAb-202. In some embodiments, the intact ADC is MORAb-109.

[0303] In some embodiments, the DAR insensitive assay quantifies an intact anti-FRA ADC. In some embodiments, the capture antibody or antigen-binding fragment is an anti- eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the capture antibody or antigen-binding fragment is 5E4. In some embodiments, the 5E4 is an antigen-binding fragment. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is biotinylated. In some embodiments, the 5E4 is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-ID antibody or antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment is 2G9. In some embodiments, the 2G9 is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag. In some embodiments, the detection antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti- human IgG Fc antibody or antigen-binding fragment is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.Attorney Docket No.15648.0054-00304

[0304] In some embodiments, the DAR insensitive assay quantifies an intact anti-MSLN ADC. In some embodiments, the capture antibody or antigen-binding fragment is an anti- eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the capture antibody or antigen-binding fragment is 5E4. In some embodiments, the 5E4 is an antigen-binding fragment. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is biotinylated. In some embodiments, the 5E4 is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-ID antibody or antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag. In some embodiments, the detection antibody or antigen- binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0305] In some embodiments, the DAR insensitive assay quantifies an intact anti-HER2 ADC. In some embodiments, the capture antibody or antigen-binding fragment is an anti- eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the capture antibody or antigen-binding fragment is 5E4. In some embodiments, the 5E4 is an antigen-binding fragment. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is biotinylated. In some embodiments, the 5E4 is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-ID antibody or antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment is conjugated to a detectable label. Anti-ID trastuzumab antibodies are known in the art and include, e.g., FAB95471R (R&D Systems). In some embodiments, the detectable label is a fluorescent tag. In some embodiments, the detection antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.Attorney Docket No.15648.0054-00304

[0306] In various embodiments, the assay is DAR sensitive. In some embodiments, a capture antibody or antigen-binding fragment in a DAR sensitive assay is an anti-ID antibody or antigen-binding fragment. In some embodiments, an anti-ID antibody or antigen-binding fragment is the target antigen (e.g., FRA, MSLN, HER2) of the antibody to be captured. In some embodiments, a capture antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the capture antibody or antigen-binding fragment is an antigen-binding fragment. In some embodiments, the capture antigen-binding fragment is a Fab fragment. In some embodiments, the capture antibody or antigen-binding fragment is biotinylated. In some embodiments, the capture antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the capture antibody or antigen-binding fragment is 5E4. In some embodiments, the 5E4 is an antigen-binding fragment. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0307] In some embodiments, a method for detecting intact ADC in a DAR sensitive manner is provided herein. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered an ADC. In some embodiments, the method further comprises contacting the biological sample with an anti-ID antibody or antigen-binding fragment or with an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-ID antibody or antigen- binding fragment and / or the anti-human IgG Fc antibody or antigen-binding fragment is biotinylated. In some embodiments, the anti-ID antibody or antigen-binding fragment and / or the anti-human IgG Fc antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the method further comprises contacting the biological sample with 5E4. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is conjugated to a detectable label, e.g., a fluorescent tag. In some embodiments, a signal from the detectable label is detected for quantification of the intact ADC. In some embodiments, the anti-ID antibody is 2G9 or an antigen-binding fragment thereof. In someAttorney Docket No.15648.0054-00304 embodiments, the anti-ID antibody is an anti-345A12 idiotypic antibody or antigen-binding fragment thereof. In some embodiments, the intact ADC is MORAb-202. In some embodiments, the intact MORAb-202 has DAR4. In some embodiments, the intact ADC is MORAb-109. In some embodiments, the intact MORAb-109 has DAR2. In some embodiments, the intact MORAb-109 has DAR4.

[0308] In some embodiments, the DAR sensitive assay quantifies an intact anti-FRA ADC. In some embodiments, the capture antibody or antigen-binding fragment is an anti-ID antibody or antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen- binding fragment is 2G9. In some embodiments, the 2G9 is an antigen-binding fragment. In some embodiments, the 2G9 is a Fab fragment. In some embodiments, the 2G9 is biotinylated. In some embodiments, the 2G9 is immobilized on a solid support. In some embodiments, the capture antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti- human IgG Fc antibody or antigen-binding fragment is biotinylated. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti- eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is 5E4. In some embodiments, the 5E4 is an antigen-binding fragment. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0309] In some embodiments, the DAR sensitive assay quantifies an intact anti-MSLN ADC. In some embodiments, the capture antibody or antigen-binding fragment is an anti-ID antibody or antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen- binding fragment is an antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment is a Fab fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment is biotinylated. In some embodiments, the anti-ID antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the capture antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen- binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody orAttorney Docket No.15648.0054-00304 antigen-binding fragment is biotinylated. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is 5E4. In some embodiments, the 5E4 is an antigen- binding fragment. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0310] In some embodiments, the DAR sensitive assay quantifies an intact anti-HER2 ADC. In some embodiments, the capture antibody or antigen-binding fragment is an anti-ID antibody or antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen- binding fragment is an antigen-binding fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment is a Fab fragment. In some embodiments, the anti-ID antibody or antigen-binding fragment is biotinylated. In some embodiments, the anti-ID antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the capture antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen- binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is biotinylated. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is an anti-eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the anti-eribulin antibody or antigen-binding fragment is 5E4. In some embodiments, the 5E4 is an antigen- binding fragment. In some embodiments, the 5E4 is a Fab fragment. In some embodiments, the 5E4 is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag. Quantifying Linker-Payload

[0311] In some embodiments, a method for detecting a metabolite of an ADC comprises an assay to quantify free linker-payload, i.e., linker-payload not conjugated to an antibody. In some embodiments, linker-payload is quantified in a biological sample. In some embodiments, the biological sample is plasma. In some embodiments, the assay comprisesAttorney Docket No.15648.0054-00304 immunodepletion. In some embodiments, the assay does not comprise immunodepletion. In some embodiments, the assay comprises a sandwich immunoassay. An exemplary method disclosed herein quantifies linker-payload by immunodepletion of ADC and / or unconjugated antibody or antigen-binding fragment followed by fluorescent detection of linker-payload using a sandwich immunoassay.

[0312] In various embodiments, the immunodepletion step of the assay comprises contacting the sample with a first antibody (“immunodepletion antibody”) or antigen-binding fragment capable of specifically binding to an antibody portion of an antibody-drug conjugate and / or an unconjugated antibody or antigen-binding fragment in the biological sample. In some embodiments, the immunodepletion antibody or antigen-binding fragment is conjugated to a solid support. In some embodiments, the immunodepletion antibody or antigen-binding fragment is conjugated to a label. In some embodiments, the label is a bead, e.g., an agarose bead or a magnetic bead. In some embodiments, bead is a magnetic bead. In some embodiments, the antibody portion of an antibody-drug conjugate and / or an unconjugated antibody or antigen-binding fragment bound to the immunodepletion antibody are immunodepleted from the biological sample. In some embodiments, the immunodepletion is performed by centrifugation, e.g., using agarose bead-labeled immunodepletion antibody or antigen-binding fragment. In some embodiments, the immunodepletion is performed by magnetic separation, e.g., using magnetic bead-labeled immunodepletion antibody or antigen- binding fragment.

[0313] In some embodiments, the immunodepletion antibody or antigen-binding fragment specifically binds an ADC comprising an anti-FRA antibody or antigen-binding fragment thereof. In some embodiments, the ADC is MORAb-202. In some embodiments, the ADC comprises farletuzumab or an antigen-binding fragment thereof. In some embodiments, the ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 49, HCDR2 comprising SEQ ID NO: 50, HCDR3 comprising SEQ ID NO: 51; LCDR1 comprising SEQ ID NO: 52, LCDR2 comprising SEQ ID NO: 53, and LCDR3 comprising SEQ ID NO: 54, as defined by the Kabat numbering system. In some embodiments, the ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 55, HCDR2 comprising SEQ ID NO: 56, HCDR3 comprising SEQ ID NO: 57; LCDR1 comprising SEQ ID NO: 58, LCDR2 comprising SEQ ID NO: 59, and LCDR3 comprisingAttorney Docket No.15648.0054-00304 SEQ ID NO: 60, as defined by the IMGT numbering system. In some embodiments, the ADC comprises an antibody comprising a heavy chain variable domain comprising a sequence of SEQ ID NO: 61 and a light chain variable domain comprising a sequence of SEQ ID NO: 62. In some embodiments, the ADC comprises an antibody comprising a heavy chain of SEQ ID NO: 63 and a light chain sequence of SEQ ID NO: 64.

[0314] In some embodiments, the immunodepletion antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a label. In some embodiments, the label is a bead, e.g., an agarose bead or a magnetic bead. In some embodiments, bead is a magnetic bead.

[0315] In some embodiments, the immunodepletion antibody or antigen-binding fragment comprises an anti-FRA idiotypic antibody or antigen-binding fragment. In some embodiments, the anti-idiotypic antibody or antigen-binding fragment comprises an anti- farletuzumab antibody or antigen-binding fragment as disclosed herein. In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three LCDRs comprising SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3) as defined by the Kabat numbering system. In some embodiments, an anti-farletuzumab antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three LCDRs comprising SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system.

[0316] In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13 and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14.

[0317] In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15 and a light chain comprising an amino acid sequence of SEQ ID NO: 16.

[0318] In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment is antibody 2G9.Attorney Docket No.15648.0054-00304

[0319] In some embodiments, the anti-farletuzumab antibody or antigen-binding fragment is conjugated to a label. In some embodiments, the label is a bead, e.g., an agarose bead or a magnetic bead. In some embodiments, bead is a magnetic bead.

[0320] In some embodiments, the immunodepletion antibody or antigen-binding fragment specifically binds an ADC comprising an anti-MSLN antibody or antigen-binding fragment thereof. In some embodiments, the ADC is MORAb-109. In some embodiments, the ADC comprises 345A12 or an antigen-binding fragment thereof. In some embodiments, the ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 65, HCDR2 comprising SEQ ID NO: 66, HCDR3 comprising SEQ ID NO: 67; LCDR1 comprising SEQ ID NO: 68, LCDR2 comprising SEQ ID NO: 69, and LCDR3 comprising SEQ ID NO: 70, as defined by the Kabat numbering system. In some embodiments, the ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 71, HCDR2 comprising SEQ ID NO: 72, HCDR3 comprising SEQ ID NO: 73; LCDR1 comprising SEQ ID NO: 74, LCDR2 comprising SEQ ID NO: 75, and LCDR3 comprising SEQ ID NO: 76, as defined by the IMGT numbering system. In some embodiments, the ADC comprises an antibody comprising a heavy chain variable domain comprising a sequence of SEQ ID NO: 77 and a light chain variable domain comprising a sequence of SEQ ID NO: 78. In some embodiments, the ADC comprises an antibody comprising a heavy chain of SEQ ID NO: 79 and a light chain sequence of SEQ ID NO: 80.

[0321] In some embodiments, the immunodepletion antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a label. In some embodiments, the label is a bead, e.g., an agarose bead or a magnetic bead. In some embodiments, bead is a magnetic bead.

[0322] In some embodiments, the immunodepletion antibody or antigen-binding fragment comprises an anti-345A12 idiotypic antibody or antigen-binding fragment. In some embodiments, the anti-idiotypic antibody or antigen-binding fragment comprises an anti- 345A12 idiotypic antibody or antigen-binding fragment as disclosed herein. In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO:Attorney Docket No.15648.0054-00304 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three LCDRs comprising SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3) as defined by the Kabat numbering system. In some embodiments, an anti-345A12 idiotypic antibody or antigen-binding fragment comprises three HCDRs comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three LCDRs comprising SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system.

[0323] In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285 and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286.

[0324] In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287 and a light chain comprising an amino acid sequence of SEQ ID NO: 288.

[0325] In some embodiments, the anti-345A12 idiotypic antibody or antigen-binding fragment is antibody M000053.

[0326] In some embodiments, the anti-345A12 antibody or antigen-binding fragment is conjugated to a label. In some embodiments, the label is a bead, e.g., an agarose bead or a magnetic bead. In some embodiments, bead is a magnetic bead.

[0327] In some embodiments, the immunodepletion antibody or antigen-binding fragment specifically binds an ADC comprising HER2 or an antigen-binding fragment thereof. In some embodiments, the ADC comprises trastuzumab or an antigen-binding fragment thereof. In some embodiments, the ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 254, HCDR2 comprising SEQ ID NO: 255, HCDR3 comprising SEQ ID NO: 256; LCDR1 comprising SEQ ID NO: 257, LCDR2 comprising SEQ ID NO: 258, and LCDR3 comprising SEQ ID NO: 259, as defined by the Kabat numbering system. In some embodiments, the ADC comprises an antibody comprising three heavy chain CDRs and three light chain CDRs as follows: HCDR1 comprising SEQ ID NO: 260, HCDR2 comprising SEQ ID NO: 261, HCDR3 comprising SEQ ID NO: 262; LCDR1 comprising SEQ ID NO: 263, LCDR2 comprising SEQ ID NO: 264, and LCDR3 comprising SEQ ID NO: 265, as defined by the IMGT numbering system. In some embodiments, the ADC comprises an antibody comprisingAttorney Docket No.15648.0054-00304 a heavy chain variable domain comprising a sequence of SEQ ID NO: 266 and a light chain variable domain comprising a sequence of SEQ ID NO: 267. In some embodiments, the ADC comprises an antibody comprising a heavy chain of SEQ ID NO: 268 and a light chain sequence of SEQ ID NO: 269.

[0328] In some embodiments, the immunodepletion antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a label. In some embodiments, the label is a bead, e.g., an agarose bead or a magnetic bead. In some embodiments, bead is a magnetic bead.

[0329] In some embodiments, the immunodepletion antibody or antigen-binding fragment comprises an anti-trastuzumab idiotypic antibody or antigen-binding fragment. Anti- trastuzumab idiotypic antibodies or antigen-binding fragments thereof are known in the art and include, e.g., FAB95471R (R&D Systems).

[0330] In some embodiments, the anti-trastuzumab antibody or antigen-binding fragment is conjugated to a label. In some embodiments, the label is a bead, e.g., an agarose bead or a magnetic bead. In some embodiments, bead is a magnetic bead.

[0331] In some embodiments, the sandwich immunoassay comprises contacting the sample with a second antibody (“capture antibody”) or antigen-binding fragment and a third antibody (“detection antibody”) or antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is biotinylated. In some embodiments, the capture antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is immobilized on a solid support. In some embodiments, the detection antibody or antigen-binding fragment is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent label. In some embodiments, the assay comprises detecting a signal from the detectable label on the detection antibody. In some embodiments, the linker-payload in the biological sample is quantified using the signal from the detectable label.

[0332] In some embodiments, the capture antibody or antigen-binding fragment is an anti- eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the capture antibody or antigen-binding fragment is 5E4. In some embodiments, the capture antibody or antigen-binding fragment is an anti-VCP antibody or antigen-binding fragment asAttorney Docket No.15648.0054-00304 provided herein. In some embodiments, the anti-VCP antibody is antibody 11G6. In some embodiments, the capture antibody or antigen-binding fragment is an antigen-binding fragment. In some embodiments, the capture antibody or antigen-binding fragment is a Fab fragment. In some embodiments, the capture antibody or antigen-binding fragment is biotinylated. In some embodiments, the capture antibody or antigen-binding fragment is immobilized on a solid support.

[0333] In some embodiments, the detection antibody or antigen-binding fragment is an anti-VCP antibody or antigen-binding fragment as provided herein. In some embodiments, the anti-VCP antibody is 11G6. In some embodiments, the detection antibody or antigen- binding fragment is an anti-eribulin antibody or antigen-binding fragment as disclosed herein. In some embodiments, the detection antibody or antigen-binding fragment is 5E4. In some embodiments, the detection antibody or antigen-binding fragment is an antigen-binding fragment. In some embodiments, the detection antibody or antigen-binding fragment is a Fab fragment. In some embodiments, the detection antibody or antigen-binding fragment is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0334] In some embodiments, the capture antibody or antigen-binding fragment is 5E4. In some embodiments, 5E4 is an antigen-binding fragment. In some embodiments, 5E4 is a Fab fragment. In some embodiments, 5E4 is biotinylated. In some embodiments, 5E4 is immobilized on a solid support. In some embodiments, the the detection antibody or antigen- binding fragment is 11G6. In some embodiments, 11G6 is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0335] In some embodiments, the limit of quantification of the linker-payload (e.g., VCP- eribulin) in plasma is at least 1.0 ng / mL, at least 1.5 ng / mL, at least 2.0 ng / mL, at least 2.5 ng / mL, at least 3.0 ng / mL, at least 3.5 ng / mL, at least 4.0 ng / mL, at least 4.5 ng / mL, or at least 5.0 ng / mL as measured by Gyrolab xPand immunoassay.

[0336] In some embodiments, the detection antibody or antigen-binding fragment is an anti-albumin antibody or antigen-binding fragment. Anti-albumin antibodies are well known in the art. Any species-specific anti-albumin antibody known in the art may be used in the assays disclosed herein. Albumin is an abundant circulating protein found in plasma. The presence of an unpaired cysteine on albumin provides a possible conjugation site for free linker-payload in circulation. To accurately quantitate linker-payload metabolites inAttorney Docket No.15648.0054-00304 circulation, it may therefore be important to detect albumin-linker-payload conjugates in addition to free linker-payload conjugates.

[0337] In some embodiments, a linker-payload metabolite in circulation may react with an albumin protein to produce an albumin-linker-payload conjugate. In some embodiments, the albumin-linker-payload conjugate comprises albumin-VCP-eribulin. In some embodiments, the albumin-linker-payload conjugate comprises albumin-Mal-(PEG)m-VCP-eribulin. In some embodiments, the albumin-linker-payload conjugate comprises albumin-Mal-(PEG)2- VCP-eribulin.

[0338] In some embodiments, the anti-albumin antibody or antigen-binding fragment is conjugated to a detectable label. In some embodiments, the detectable label is a fluorescent tag.

[0339] In various embodiments, a method for detecting a linker-payload metabolite of MORAb-202 is provided herein. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method further comprises contacting the biological sample with antibody 2G9. In some embodiments, the 2G9 is conjugated to a magnetic bead. In some embodiments, contacting the biological sample with antibody 2G9 immunodepletes the MORAb-202 or an antibody or antigen-binding fragment thereof. In some embodiments, the method further comprises contacting the biological sample with antibody 5E4. In some embodiments, the 5E4 is biotinylated and immobilized on a solid support. In some embodiments, the method further comprises contacting the biological sample with antibody 11G6. In some embodiments, the 11G6 is conjugated to a detectable label, e.g., a fluorescent tag. In some embodiments, a signal from the detectable label is detected for quantification of the linker-payload metabolite. In some embodiments, the linker-payload metabolite comprises VCP-eribulin. In some embodiments, the linker-payload metabolite comprises Mal-(PEG)2-VCP-eribulin.

[0340] In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-202. In some embodiments, the method further comprises contacting the biological sample with antibody 2G9. In some embodiments, the 2G9 is conjugated to a magnetic bead. In some embodiments, contacting the biological sample with antibody 2G9 immunodepletes the MORAb-202 or an antibody or antigen- binding fragment thereof. In some embodiments, the method further comprises contacting theAttorney Docket No.15648.0054-00304 biological sample with antibody 5E4. In some embodiments, the 5E4 is biotinylated and immobilized on a solid support. In some embodiments, the method further comprises contacting the biological sample with an anti-albumin antibody. In some embodiments, the anti-albumin antibody is conjugated to a detectable label, e.g., a fluorescent tag. In some embodiments, a signal from the detectable label is detected for quantification of the linker- payload metabolite. In some embodiments, the linker-payload metabolite comprises VCP- eribulin. In some embodiments, the linker-payload metabolite comprises Mal-(PEG)2-VCP- eribulin.

[0341] In various other embodiments, a method for detecting a linker-payload metabolite of MORAb-109 is provided herein. In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method further comprises contacting the biological sample with an anti- human IgG Fc antibody or antigen-binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a magnetic bead. In some embodiments, contacting the biological sample with the anti-human IgG Fc antibody or antigen-binding fragment immunodepletes the MORAb-109 or an antibody or antigen-binding fragment thereof. In some embodiments, the method further comprises contacting the biological sample with antibody 5E4. In some embodiments, the 5E4 is biotinylated and immobilized on a solid support. In some embodiments, the method further comprises contacting the biological sample with antibody 11G6. In some embodiments, the 11G6 is conjugated to a detectable label, e.g., a fluorescent tag. In some embodiments, a signal from the detectable label is detected for quantification of the linker-payload metabolite. In some embodiments, the linker-payload metabolite comprises VCP-eribulin. In some embodiments, the linker-payload metabolite comprises Mal-(PEG)2-VCP-eribulin.

[0342] In some embodiments, the method comprises obtaining a biological sample from a subject who has been administered MORAb-109. In some embodiments, the method further comprises contacting the biological sample with an anti-human IgG Fc antibody or antigen- binding fragment. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment binds the CH2 domain. In some embodiments, the anti-human IgG Fc antibody or antigen-binding fragment is conjugated to a magnetic bead. In some embodiments, contacting the biological sample with antibody anti-human IgG Fc antibody or antigen-binding fragmentAttorney Docket No.15648.0054-00304 immunodepletes the MORAb-109 or an antibody or antigen-binding fragment thereof. In some embodiments, the method further comprises contacting the biological sample with antibody 5E4. In some embodiments, the 5E4 is biotinylated and immobilized on a solid support. In some embodiments, the method further comprises contacting the biological sample with an anti-albumin antibody. In some embodiments, the anti-albumin antibody is conjugated to a detectable label, e.g., a fluorescent tag. In some embodiments, a signal from the detectable label is detected for quantification of the linker-payload metabolite. In some embodiments, the linker-payload metabolite comprises VCP-eribulin. In some embodiments, the linker-payload metabolite comprises Mal-(PEG)2-VCP-eribulin.

[0343] In various embodiments, the method disclosed herein may also be used to detect a linker-payload metabolite of an anti-HER2 ADC.

[0344] In various embodiments, kits are provided, which may comprise the antibodies disclosed herein and one or more other containers associated therewith that comprise materials desirable from a commercial and user standpoint, including buffers, diluents, filters, needles, syringes; carrier, package, container, vial and / or tube labels listing contents and / or instructions for use, and package inserts with instructions for use.

[0345] A label may be present on or with the kit to indicate that the kit is used for a specific therapy or non-therapeutic application, such as a prognostic, prophylactic, diagnostic, or laboratory application. A label may also indicate directions for either in vivo or in vitro use, such as those described herein. Directions and or other information may also be included on an insert(s) or label(s), which is included with or on the kit. The label may be on or associated with the container. A label may be on a container when letters, numbers, or other characters forming the label are molded or etched into the container itself. A label may be associated with a kit when it is present within a receptacle or carrier that also holds the container, e.g., as a package insert.

[0346] It will be readily apparent to those skilled in the art that other suitable modifications and adaptations of the methods of the invention described herein are obvious and may be made using suitable equivalents without departing from the scope of the invention or the embodiments disclosed herein. Having now described the invention in detail, the same will be more clearly understood by reference to the following examples, which are included for purposes of illustration only and are not intended to be limiting.Attorney Docket No.15648.0054-00304 EXEMPLARY EMBODIMENTS 1. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload and the payload moiety is eribulin, the method comprising: a) obtaining a biological sample from a subject who has been administered the antibody-drug conjugate; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the antibody-drug conjugate and / or an unconjugated antibody or antigen-binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to the payload moiety of the linker-payload; d) contacting the biological sample with a third antibody or antigen-binding fragment, wherein the third antibody or antigen-binding fragment is capable of specifically binding to the linker of the linker-payload; and e) detecting a signal from the third antibody or antigen-binding fragment, thereby detecting the metabolite in the biological sample. 2. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload and the payload moiety is eribulin, the method comprising: a) obtaining a biological sample from a subject who has been administered the antibody-drug conjugate; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the antibody-drug conjugate and / or an unconjugated antibody or antigen-binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to the payload moiety of the linker-payload; d) contacting the biological sample with a third antibody or antigen-binding fragment, wherein the third antibody or antigen-binding fragment is capable of specifically binding to albumin; and e) detecting a signal from the third antibody or antigen-binding fragment, thereby detecting the metabolite in the biological sample.Attorney Docket No.15648.0054-00304 3. The method of embodiment 1 or embodiment 2, wherein the contacting of the biological sample with the first antibody immunodepletes intact antibody-drug conjugate from the biological sample. 4. The method of any one of embodiments 1 to 3, wherein the first, second, and / or third antibody or antigen-binding fragment is conjugated to a detectable label, a biotin, or a bead. 5. The method of embodiment 4, wherein the first antibody or antigen-binding fragment is conjugated to a biotin. 6. The method of embodiment 4, wherein the first antibody or antigen-binding fragment is conjugated to a bead, preferably a magnetic bead. 7. The method of any one of embodiments 4 to 6, wherein the second antibody or antigen-binding fragment is conjugated to a biotin. 8. The method of embodiment 5 or embodiment 7, wherein the first and / or second antibody or antigen-binding fragment is immobilized on a solid support. 9. The method of any one of embodiments 4 to 8, wherein the third antibody or antigen- binding fragment is conjugated to a detectable label. 10. The method of embodiment 9, wherein the detectable label is a fluorescent tag. 11. The method of any one of embodiments 4 to 10, wherein detecting the metabolite comprises detecting a signal from the detectable label on the third antibody or antigen- binding fragment. 12. The method of any one of embodiments 1 to 11, further comprising quantifying the amount of linker-payload in the biological sample by detecting a signal from the detectable label on the third antibody or antigen-binding fragment.Attorney Docket No.15648.0054-00304 13. The method of embodiment 12, wherein the signal from the detectable label on the third antibody or antigen-binding fragment comprises a fluorescent signal. 14. The method of any one of embodiments 1 to 13, wherein the antibody-drug conjugate comprises an anti-folate receptor alpha (FRA) antibody or antigen-binding fragment, and / or wherein the unconjugated antibody or antigen-binding fragment is an anti-FRA antibody or a fragment thereof. 15. The method of embodiment 14, wherein the antibody-drug conjugate comprises farletuzumab or an antigen-binding fragment thereof, and / or wherein the unconjugated antibody or antigen-binding fragment is farletuzumab or a fragment thereof. 16. The method of any one of embodiments 1 to 15, wherein the first antibody or antigen- binding fragment specifically binds an anti-FRA antibody or antigen-binding fragment thereof. 17. The method of any one of embodiments 1 to 16, wherein the first antibody or antigen- binding fragment specifically binds farletuzumab or a fragment thereof. 18. The method of embodiment 17, wherein the first antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14. 19. The method of embodiment 17, wherein the first antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7Attorney Docket No.15648.0054-00304 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system. 20. The method of any one of embodiments 16 to 19, wherein the first antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14. 21. The method of any one of embodiments 16 to 19, wherein the first antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO: 16. 22. The method of any one of embodiments 16 to 21, wherein the first antibody is 2G9. 23. The method of any one of embodiments 1 to 13, wherein the antibody-drug conjugate comprises an anti-mesothelin (MSLN) antibody or antigen-binding fragment, and / or wherein the unconjugated antibody or antigen-binding fragment is an anti-MSLN antibody or a fragment thereof. 24. The method of embodiment 23, wherein the antibody-drug conjugate comprises 345A12-HC15-LC4 or an antigen-binding fragment thereof, and / or wherein the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or a fragment thereof. 25. The method of any one of embodiments 1 to 13, 23, or 24, wherein the first antibody or antigen-binding fragment specifically binds an anti-MSLN antibody or antigen-binding fragment. 26. The method of any one of embodiments 1 to 13 or 23 to 25, wherein the first antibody or antigen-binding fragment specifically binds 345A12-HC15-LC4 or a fragment thereof.Attorney Docket No.15648.0054-00304 27. The method of embodiment 26, wherein the first antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 28. The method of embodiment 26, wherein the first antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system. 29. The method of any one of embodiments 25 to 28, wherein the first antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 30. The method of any one of embodiments 25 to 29, wherein the first antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO: 288. 31. The method of any one of embodiments 1 to 13, wherein the first antibody or antigen- binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment thereof. 32. The method of any one of embodiments 1 to 31, wherein the second antibody or antigen-binding fragment comprises three heavy chain complementarity determining regionsAttorney Docket No.15648.0054-00304 from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30. 33. The method of any one of embodiments 1 to 32, wherein the second antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system. 34. The method of embodiment 32 or embodiment 33, wherein the second antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30. 35. The method of any one of embodiments 32 to 34, wherein the second antibody or antigen-binding fragment is an antigen-binding fragment, preferably a Fab fragment. 36. The method of any one of embodiments 32 to 35, wherein the second antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 31 or SEQ ID NO: 294, and a light chain comprising an amino acid sequence of SEQ ID NO: 32. 37. The method of any one of embodiments 32 to 36, wherein the second antibody or antigen-binding fragment is 5E4.Attorney Docket No.15648.0054-00304 38. The method of any one of embodiments 1 to 37, wherein the second antibody or antigen-binding fragment binds to eribulin with a binding affinity of at least 0.9 nM, at least 1.0 nM, at least 1.1 nM, or at least 1.2 nM. 39. The method of any one of embodiments 1 to 38, wherein the linker-payload comprises Val-Cit-pAb-eribulin (“VCP-eribulin”). 40. The method of embodiment 39, wherein the linker-payload comprises Mal-(PEG)2- VCP-eribulin. 41. The method of any one of embodiments 1 to 40, wherein the linker-payload comprises Mal-(PEG)2-VCP-eribulin, wherein the Mal moiety is conjugated to albumin. 42. The method of any one of embodiments 1 or 3 to 41, wherein the third antibody or antigen-binding fragment specifically binds Val-Cit-pAB (“VCP”). 43. The method of embodiment 42, wherein the third antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46. 44. The method of embodiment 42 or embodiment 43, wherein the third antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 33 (HCDR1), SEQ ID NO: 34 (HCDR2), and SEQ ID NO: 35 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 36 (LCDR1), SEQ ID NO: 37 (LCDR2), and SEQ ID NO: 38 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 39 (HCDR1), SEQ ID NO: 40 (HCDR2), and SEQ ID NO: 41 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ IDAttorney Docket No.15648.0054-00304 NO: 42 (LCDR1), SEQ ID NO: 43 (LCDR2), and SEQ ID NO: 38 (LCDR3), as defined by the IMGT numbering system. 45. The method of any one of embodiments 42 to 44, wherein the third antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46. 46. The method of any one of embodiments 42 to 45, wherein the third antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 47, and a light chain comprising an amino acid sequence of SEQ ID NO: 48. 47. The method of any one of embodiments 42 to 46, wherein the third antibody or antigen-binding fragment is 11G6. 48. The method of any one of embodiments 1 to 47, wherein the biological sample comprises whole blood, plasma, and / or serum from a patient. 49. The method of any one of embodiments 4 to 48, wherein the detectable label comprises a fluorescent tag, a luminescent tag, an electrochemiluminescent tag, or an enzyme reporter. 50. The method of embodiment 49, wherein the detectable label is a fluorescent tag, a luminescent tag, or an electrochemiluminescent tag. 51. The method of any one of embodiments 1 to 50, wherein the first antibody or antigen- binding fragment is conjugated to a magnetic bead, the second antibody or antigen-binding fragment is conjugated to a biotin, and the third antibody or antigen-binding fragment is conjugated to a fluorescent tag. 52. The method of any one of embodiments 1 or 3 to 51, wherein the linker-payload comprises VCP-eribulin, and wherein the limit of quantification of the VCP-eribulin is atAttorney Docket No.15648.0054-00304 least 1.0 ng / mL, at least 1.5 ng / mL, at least 2.0 ng / mL, at least 2.5 ng / mL, at least 3.0 ng / mL, at least 3.5 ng / mL, at least 4.0 ng / mL, at least 4.5 ng / mL, or at least 5.0 ng / mL as measured by Gyrolab xPand immunoassay, wherein the biological sample comprises plasma. 53. The method of any one of embodiments 1 to 52, wherein the limit of quantification for the eribulin is at least 5 pg / mL, at least 10 pg / mL, at least 15 pg / mL, or at least 20 pg / mL as measured by multiple reaction monitoring (MRM) detection. 54. The method of any one of embodiments 1 to 53, wherein the limit of quantification for eribulin is at least 10 pg / mL as measured by multiple reaction monitoring (MRM) detection. 55. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with 2G9; c) contacting the biological sample with 5E4; d) contacting the biological sample with 11G6; and e) detecting a signal from 11G6, thereby detecting the metabolite in the biological sample. 56. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with 2G9; c) contacting the biological sample with 5E4;Attorney Docket No.15648.0054-00304 d) contacting the biological sample with an anti-albumin antibody; and e) detecting a signal from the anti-albumin antibody, thereby detecting the metabolite in the biological sample. 57. The method of embodiment 55 or embodiment 56, wherein the contacting of the biological sample with the 2G9 immunodepletes intact MORAb-202 from the biological sample. 58. The method of any one of embodiments 55 to 57, wherein the 2G9 is conjugated to a biotin or a magnetic bead. 59. The method of any one of embodiments 55 to 58, wherein the 5E4 is conjugated to a biotin. 60. The method of embodiment 59, wherein the 5E4 is immobilized on a solid support. 61. The method of any one of embodiments 55 to 60, wherein the 11G6 or anti-albumin antibody is conjugated to a detectable label, preferably wherein the detectable label is a fluorescent tag. 62. The method of embodiment 61, wherein detecting the metabolite comprises detecting a signal from the detectable label. 63. The method of embodiment 61 or embodiment 62, further comprising quantifying the amount of VCP-eribulin in the biological sample by detecting a signal from the detectable label. 64. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-109, the method comprising:Attorney Docket No.15648.0054-00304 a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti- human IgG Fc or an anti-idiotypic antibody or antigen binding fragment, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; c) contacting the biological sample with 5E4; d) contacting the biological sample with 11G6; and e) detecting a signal from 11G6, thereby detecting the metabolite in the biological sample. 65. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti- human IgG Fc or an anti-idiotypic antibody or antigen binding fragment, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; c) contacting the biological sample with 5E4; d) contacting the biological sample with an anti-albumin antibody; and e) detecting a signal from the anti-albumin antibody, thereby detecting the metabolite in the biological sample.Attorney Docket No.15648.0054-00304 66. The method of embodiment 64 or embodiment 65, wherein the contacting of the biological sample with the first antibody or antigen-binding fragment immunodepletes intact MORAb-109 from the biological sample. 67. The method of any one of embodiments 64 to 66, wherein the first antibody or antigen-binding fragment is conjugated to a biotin. 68. The method of any one of embodiments 64 to 66, wherein the first antibody or antigen-binding fragment is conjugated to a bead, preferably a magnetic bead. 69. The method of any one of embodiments 64 to 68, wherein the 5E4 is conjugated to a biotin. 70. The method of embodiment 69, wherein the 5E4 is immobilized on a solid support. 71. The method of any one of embodiments 64 to 70, wherein the 11G6 or the anti- albumin antibody is conjugated to a detectable label, preferably wherein the detectable label is a fluorescent tag. 72. The method of embodiment 71, wherein detecting the metabolite comprises detecting a signal from the detectable label. 73. The method of embodiment 71 or embodiment 72, further comprising quantifying the amount of VCP-eribulin in the biological sample by detecting a signal from the detectable label. 74. The method of any one of embodiments 55 to 73, wherein 5E4 binds to eribulin with a binding affinity of at least 0.9 nM, at least 1.0 nM, at least 1.1 nM, or at least 1.2 nM. 75. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and theAttorney Docket No.15648.0054-00304 unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample. 76. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen- binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, whereinAttorney Docket No.15648.0054-00304 the second antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample. 77. The method of embodiment 75 or embodiment 76, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14. 78. The method of embodiment 75 or embodiment 76, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system. 79. The method of any one of embodiments 75 to 78, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14.Attorney Docket No.15648.0054-00304 80. The method of any one of embodiments 75 to 79, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO: 16. 81. The method of any one of embodiments 75 to 80, wherein the anti-idiotypic antibody is 2G9. 82. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen- binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample. 83. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen- binding fragment thereof, the method comprising:Attorney Docket No.15648.0054-00304 a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen- binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or antibody or antigen-binding fragment in the biological sample. 84. The method of embodiment 82 or embodiment 83, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 85. The method of embodiment 82 or embodiment 83, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chain complementarity determining regions comprising amino acidAttorney Docket No.15648.0054-00304 sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system. 86. The method of any one of embodiments 83 to 85, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 87. The method of any one of embodiments 83 to 86, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO: 288. 88. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises 2G9; c) contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment; and d) detecting a signal from second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample. 89. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202;Attorney Docket No.15648.0054-00304 b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti- human IgG Fc antibody or antigen-binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises 2G9; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample. 90. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen- binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; c) contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment; and d) detecting a signal from second antibody or antigen-binding fragment, thereby detecting the total ADC and / or antibody or unconjugated antigen-binding fragment in the biological sample. 91. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen- binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109;Attorney Docket No.15648.0054-00304 b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti- human IgG Fc antibody or antigen-binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample. 92. The method of any one of embodiments 75 to 91, wherein the first antibody or antigen-binding fragment is conjugated to a biotin or a bead, preferably a biotin. 93. The method of embodiment 92, wherein the first antibody or antigen-binding fragment is immobilized on a solid support. 94. The method of any one of embodiments 75 to 93, wherein the second antibody or antigen-binding fragment is conjugated to a detectable label. 95. The method of embodiment 94, wherein the detectable label is a fluorescent tag. 96. The method of any one of embodiments 75 to 95, wherein the first antibody or antigen-binding fragment is conjugated to a biotin, and the second antibody or antigen- binding fragment is conjugated to a fluorescent tag. 97. The method of any one of embodiments 75 to 96, wherein detecting the total ADC and / or unconjugated antibody or antigen-binding fragment comprises detecting a signal from the detectable label.Attorney Docket No.15648.0054-00304 98. The method of any one of embodiments 75 to 97, further comprising quantifying the amount of total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample by detecting a signal from the detectable label. 99. The method of any one of embodiments 75 to 98, wherein the biological sample comprises whole blood, plasma, and / or serum from a patient. 100. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to eribulin; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample. 101. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an antigen-binding fragment thereof, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof;Attorney Docket No.15648.0054-00304 c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to eribulin; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample. 102. The method of embodiment 100 or embodiment 101, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14. 103. The method of embodiment 100 or embodiment 101, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system. 104. The method of any one of embodiments 100 to 103, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14. 105. The method of any one of embodiments 100 to 104, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO: 16.Attorney Docket No.15648.0054-00304 106. The method of any one of embodiments 100 to 105, wherein the anti-idiotypic antibody is 2G9. 107. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to eribulin; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample. 108. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to eribulin; and d) detecting a signal from the second antibody or antigen-binding fragment,Attorney Docket No.15648.0054-00304 thereby detecting the intact ADC in the biological sample. 109. The method of embodiment 107 or embodiment 108, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 110. The method of embodiment 107 or embodiment 108, wherein the anti-idiotypic antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system. 111. The method of any one of embodiments 107 to 110, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 112. The method of any one of embodiments 107 to 111, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO: 288.Attorney Docket No.15648.0054-00304 113. The method of any one of embodiments 100 to 112, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin is an antigen- binding fragment, preferably a Fab fragment. 114. The method of any one of embodiments 100 to 113, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30. 115. The method of any one of embodiments 100 to 113, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system. 116. The method of any one of embodiments 100 to 115, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30. 117. The method of any one of embodiments 100 to 116, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 31 or SEQ ID NO: 294, and a light chain comprising an amino acid sequence of SEQ ID NO: 32.Attorney Docket No.15648.0054-00304 118. The method of any one of embodiments 100 to 117, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin is 5E4. 119. The method of any one of embodiments 100 to 118, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin binds to eribulin with a binding affinity of at least 0.9 nM, at least 1.0 nM, at least 1.1 nM, or at least 1.2 nM. 120. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is 5E4; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or is 2G9 or an antigen-binding fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample. 121. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an antigen-binding fragment thereof, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment, or is 2G9 or an antigen-binding fragment;Attorney Docket No.15648.0054-00304 c) contacting the biological sample with a second antibody or antigen-binding, wherein the second antibody or antigen-binding fragment is 5E4; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample. 122. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is 5E4; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample. 123. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an antigen-binding fragment thereof, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment, or an anti-idiotypic antibody or antigen binding fragment, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable regionAttorney Docket No.15648.0054-00304 comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; c) contacting the biological sample with a second antibody or antigen-binding, wherein the second antibody or antigen-binding fragment is 5E4; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample. 124. The method of any one of embodiments 100 to 123, wherein the first antibody or antigen-binding fragment is conjugated to a biotin or a bead, preferably a biotin. 125. The method of embodiment 124, wherein the first antibody or antigen-binding fragment is immobilized on a solid support. 126. The method of any one of embodiments 100 to 125, wherein the second antibody or antigen-binding fragment is conjugated to a detectable label. 127. The method of embodiment 126, wherein the detectable label is a fluorescent tag. 128. The method of any one of embodiments 100 to 127, wherein the first antibody or antigen-binding fragment is conjugated to a biotin, and the second antibody or antigen- binding fragment is conjugated to a fluorescent tag. 129. The method of any one of embodiments 100 to 128, wherein detecting the intact ADC comprises detecting a signal from the detectable label. 130. The method of any one of embodiments 100 to 129, further comprising quantifying the amount of intact ADC in the biological sample by detecting a signal from the detectable label. 131. The method of any one of embodiments 100 to 130, wherein the biological sample comprises whole blood, plasma, and / or serum from a patient.Attorney Docket No.15648.0054-00304 132. A method for detecting intact and / or total antibody-drug conjugate (ADC) and / or a metabolite of an ADC, wherein the metabolite is unconjugated antibody or antigen-binding fragment, linker-payload, and / or free payload, comprising two or more of: a) the method of any one of embodiments 1 to 74; b) the method of any one of embodiments 75 to 99; c) the method of any one of embodiments 100, 102 to 107, 109 to 120, 122, 124 to 132; d) the method of any one of embodiments 101 to 106, 108 to 119, 121, 123 to 132; and e) a method comprising quantification of free payload, wherein the free payload is eribulin, wherein the eribulin is quantified by multiple reaction monitoring. 133. An antibody or antigen-binding fragment thereof capable of binding to an antibody- drug conjugate comprising farletuzumab and / or to farletuzumab or an antigen-binding fragment thereof, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14. 134. The antibody or antigen-binding fragment of embodiment 133, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system.Attorney Docket No.15648.0054-00304 135. The antibody or antigen-binding fragment of embodiment 133 or embodiment 134, wherein the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14. 136. The antibody or antigen-binding fragment of any one of embodiments 133 to 134, wherein the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO: 16. 137. The antibody or antigen-binding fragment of any one of embodiments 133 to 136, wherein the antibody or antigen-binding fragment is conjugated to a label. 138. The antibody or antigen-binding fragment of embodiment 137, wherein the label comprises a fluorescent tag, an enzyme reporter, a biotin, or a bead. 139. The antibody or antigen-binding fragment of embodiment 138, wherein the label is a biotin. 140. The antibody or antigen-binding fragment of embodiment 138, wherein the label is a bead, optionally an agarose bead or a magnetic bead. 141. The antibody or antigen-binding fragment of embodiment 138, wherein the label is a fluorescent tag. 142. An antibody or antigen-binding fragment that binds the same epitope as or competes for binding with 2G9. 143. An antibody or antigen-binding fragment thereof capable of binding to an antibody- drug conjugate comprising 345A12-HC15-LC4 and / or to 345A12-HC15-LC4 or an antigen- binding fragment thereof, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable regionAttorney Docket No.15648.0054-00304 comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 144. The antibody or antigen-binding fragment of embodiment 143, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system. 145. The antibody or antigen-binding fragment of embodiment 143 or embodiment 144, wherein the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286. 146. The antibody or antigen-binding fragment of any one of embodiments 143 to 145, wherein the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO: 288. 147. The antibody or antigen-binding fragment of any one of embodiments 143 to 146, wherein the antibody or antigen-binding fragment is conjugated to a label. 148. The antibody or antigen-binding fragment of embodiment 147, wherein the label comprises a fluorescent tag, an enzyme reporter, a biotin, or a bead.Attorney Docket No.15648.0054-00304 149. The antibody or antigen-binding fragment of embodiment 148, wherein the label is a biotin. 150. The antibody or antigen-binding fragment of embodiment 148, wherein the label is a bead, optionally an agarose bead or a magnetic bead. 151. The antibody or antigen-binding fragment of embodiment 148, wherein the label is a fluorescent tag. 152. An antibody or antigen-binding fragment thereof capable of binding to eribulin, wherein the antibody or antigen-binding fragment comprises (i) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30; (ii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 101, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 102; (iii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 119, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 120; (iv) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 137, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 138; (v) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 153, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 154;Attorney Docket No.15648.0054-00304 (vi) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 169, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 170; (vii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 183, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 184; (viii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 200, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 201; (ix) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 217, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 218; or (x) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 234, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 235. 153. The antibody or antigen-binding fragment thereof of embodiment 152, wherein the antibody or antigen-binding fragment comprises (i) three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ IDAttorney Docket No.15648.0054-00304 NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system; (ii) three HCDRs comprising amino acid sequences of SEQ ID NO: 89 (HCDR1), SEQ ID NO: 90 (HCDR2), and SEQ ID NO: 91 (HCDR3); and three LCDRs comprising SEQ ID NO: 92 (LCDR1), SEQ ID NO: 93 (LCDR2), and SEQ ID NO: 94 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 95 (HCDR1), SEQ ID NO: 96 (HCDR2), and SEQ ID NO: 97 (HCDR3); and three LCDRs comprising SEQ ID NO: 98 (LCDR1), SEQ ID NO: 99 (LCDR2), and SEQ ID NO: 100 (LCDR3) as defined by the IMGT numbering system; (iii) three HCDRs comprising amino acid sequences of SEQ ID NO: 107 (HCDR1), SEQ ID NO: 108 (HCDR2), and SEQ ID NO: 109 (HCDR3); and three LCDRs comprising SEQ ID NO: 110 (LCDR1), SEQ ID NO: 111 (LCDR2), and SEQ ID NO: 112 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 113 (HCDR1), SEQ ID NO: 114 (HCDR2), and SEQ ID NO: 115 (HCDR3); and three LCDRs comprising SEQ ID NO: 116 (LCDR1), SEQ ID NO: 117 (LCDR2), and SEQ ID NO: 118 (LCDR3) as defined by the IMGT numbering system; (iv) three HCDRs comprising amino acid sequences of SEQ ID NO: 125 (HCDR1), SEQ ID NO: 126 (HCDR2), and SEQ ID NO: 127 (HCDR3); and three LCDRs comprising SEQ ID NO: 128 (LCDR1), SEQ ID NO: 129 (LCDR2), and SEQ ID NO: 130 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 131 (HCDR1), SEQ ID NO: 132 (HCDR2), and SEQ ID NO: 133 (HCDR3); and three LCDRs com...

Claims

Attorney Docket No.15648.0054-00304 CLAIMS 1. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload and the payload moiety is eribulin, the method comprising: a) obtaining a biological sample from a subject who has been administered the antibody-drug conjugate; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the antibody-drug conjugate and / or an unconjugated antibody or antigen-binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to the payload moiety of the linker-payload; d) contacting the biological sample with a third antibody or antigen-binding fragment, wherein the third antibody or antigen-binding fragment is capable of specifically binding to the linker of the linker-payload; and e) detecting a signal from the third antibody or antigen-binding fragment, thereby detecting the metabolite in the biological sample.

2. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload and the payload moiety is eribulin, the method comprising: a) obtaining a biological sample from a subject who has been administered the antibody-drug conjugate; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the antibody-drug conjugate and / or an unconjugated antibody or antigen-binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to the payload moiety of the linker-payload; d) contacting the biological sample with a third antibody or antigen-binding fragment, wherein the third antibody or antigen-binding fragment is capable of specifically binding to albumin; and e) detecting a signal from the third antibody or antigen-binding fragment, thereby detecting the metabolite in the biological sample.Attorney Docket No.15648.0054-00304 3. The method of claim 1 or claim 2, wherein the contacting of the biological sample with the first antibody immunodepletes intact antibody-drug conjugate from the biological sample.

4. The method of any one of claims 1 to 3, wherein the first, second, and / or third antibody or antigen-binding fragment is conjugated to a detectable label, a biotin, or a bead, optionally wherein (a) the first antibody or antigen-binding fragment is conjugated to a biotin or a bead, preferably a magnetic bead; (b) the second antibody or antigen-binding fragment is conjugated to a biotin; and / or (c) the third antibody or antigen-binding fragment is conjugated to a detectable label, optionally wherein the detectable label is a fluorescent tag; optionally wherein the first and / or second antibody or antigen-binding fragment is immobilized on a solid support.

5. The method of claim 4, wherein detecting the metabolite comprises detecting a signal from the detectable label on the third antibody or antigen-binding fragment.

6. The method of any one of claims 1 to 5, wherein the antibody-drug conjugate comprises an anti-folate receptor alpha (FRA) antibody or antigen-binding fragment, and / or the unconjugated antibody or antigen-binding fragment is an anti-FRA antibody or a fragment thereof; optionally wherein the antibody-drug conjugate comprises farletuzumab or an antigen-binding fragment thereof, and / or the unconjugated antibody or antigen-binding fragment is farletuzumab or a fragment thereof.

7. The method of any one of claims 1 to 6, wherein the first antibody or antigen-binding fragment specifically binds an anti-FRA antibody or antigen-binding fragment thereof, optionally wherein the first antibody or antigen-binding fragment specifically binds farletuzumab or a fragment thereof.Attorney Docket No.15648.0054-00304 8. The method of claim 7, wherein the first antibody or antigen-binding fragment comprises: (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system.

9. The method of claim 7 or claim 8, wherein the first antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14, optionally wherein the first antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO:

16.

10. The method of any one of claims 7 to 9, wherein the first antibody is 2G9.

11. The method of any one of claims 1 to 5, wherein the antibody-drug conjugate comprises an anti-mesothelin (MSLN) antibody or antigen-binding fragment, and / or the unconjugated antibody or antigen-binding fragment is an anti-MSLN antibody or a fragment thereof,Attorney Docket No.15648.0054-00304 optionally wherein the antibody-drug conjugate comprises 345A12-HC15-LC4 or an antigen-binding fragment thereof, and / or the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or a fragment thereof.

12. The method of any one of claims 1 to 5 or 11, wherein the first antibody or antigen- binding fragment specifically binds an anti-MSLN antibody or antigen-binding fragment, optionally wherein the first antibody or antigen-binding fragment specifically binds 345A12- HC15-LC4 or a fragment thereof.

13. The method of claim 12, wherein the first antibody or antigen-binding fragment comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system.

14. The method of claim 12 or claim 13, wherein the first antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286,Attorney Docket No.15648.0054-00304 optionally wherein the first antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO:

288.

15. The method of any one of claims 1 to 5, wherein the first antibody or antigen-binding fragment is an anti-human IgG Fc antibody or antigen-binding fragment thereof.

16. The method of any one of claims 1 to 15, wherein the second antibody or antigen- binding fragment comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system.

17. The method of claim 15 or claim 16, wherein the second antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30, optionally wherein the second antibody or antigen-binding fragment is an antigen- binding fragment, preferably a Fab fragment,Attorney Docket No.15648.0054-00304 optionally wherein the second antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 31 or SEQ ID NO: 294, and a light chain comprising an amino acid sequence of SEQ ID NO:

32.

18. The method of any one of claims 15 to 17, wherein the second antibody or antigen- binding fragment is 5E4.

19. The method of any one of claims 1 to 18, wherein the linker-payload comprises Val- Cit-pAb-eribulin (“VCP-eribulin”), optionally wherein the third antibody or antigen-binding fragment specifically binds Val-Cit-pAB (“VCP”).

20. The method of claim 19, wherein the linker-payload comprises Mal-(PEG)2-VCP- eribulin, optionally wherein the Mal moiety is conjugated to albumin.

21. The method of claim 19 or claim 20, wherein the third antibody or antigen-binding fragment comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 33 (HCDR1), SEQ ID NO: 34 (HCDR2), and SEQ ID NO: 35 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 36 (LCDR1), SEQ ID NO: 37 (LCDR2), and SEQ ID NO: 38 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 39 (HCDR1), SEQ ID NO: 40 (HCDR2), and SEQ ID NO: 41 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 42 (LCDR1), SEQ ID NO: 43 (LCDR2), and SEQ ID NO: 44 (LCDR3), as defined by the IMGT numbering system.Attorney Docket No.15648.0054-00304 22. The method of any one of claims 19 to 21, wherein the third antibody or antigen- binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46, optionally wherein the third antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 47, and a light chain comprising an amino acid sequence of SEQ ID NO:

48.

23. The method of any one of claims 19 to 22, wherein the third antibody or antigen- binding fragment is 11G6.

24. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with 2G9; c) contacting the biological sample with 5E4; d) contacting the biological sample with 11G6; and e) detecting a signal from 11G6, thereby detecting the metabolite in the biological sample.

25. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with 2G9; c) contacting the biological sample with 5E4; d) contacting the biological sample with an anti-albumin antibody; andAttorney Docket No.15648.0054-00304 e) detecting a signal from the anti-albumin antibody, thereby detecting the metabolite in the biological sample.

26. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti- human IgG Fc or an anti-idiotypic antibody or antigen binding fragment, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; c) contacting the biological sample with 5E4; d) contacting the biological sample with 11G6; and e) detecting a signal from 11G6, thereby detecting the metabolite in the biological sample.

27. A method for detecting a metabolite of an antibody-drug conjugate, wherein the metabolite is a linker-payload comprising Val-Cit-pAB-eribulin (“VCP-eribulin”) and the payload moiety is eribulin, wherein the antibody-drug conjugate is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti- human IgG Fc or an anti-idiotypic antibody or antigen binding fragment, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286;Attorney Docket No.15648.0054-00304 c) contacting the biological sample with 5E4; d) contacting the biological sample with an anti-albumin antibody; and e) detecting a signal from the anti-albumin antibody, thereby detecting the metabolite in the biological sample.

28. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample.

29. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-202 and the unconjugated antibody or antigen-binding fragment is farletuzumab or an antigen-binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202;Attorney Docket No.15648.0054-00304 b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen- binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample.

30. The method of claim 28 or claim 29, wherein the anti-idiotypic antibody or antigen- binding fragment comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system.Attorney Docket No.15648.0054-00304 31. The method of any one of claims 28 to 30, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14, optionally wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO:

16.

32. The method of any one of claims 28 to 31, wherein the anti-idiotypic antibody is 2G9.

33. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and the unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen- binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or unconjugated antibody or antigen-binding fragment in the biological sample.

34. A method for detecting total antibody-drug conjugate (ADC) and / or unconjugated antibody or antigen-binding fragment, wherein the ADC is MORAb-109 and theAttorney Docket No.15648.0054-00304 unconjugated antibody or antigen-binding fragment is 345A12-HC15-LC4 or an antigen- binding fragment thereof, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen- binding fragment; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to a second epitope of the antibody portion of the ADC and / or the unconjugated antibody or antigen-binding fragment, wherein the second antibody or antigen-binding fragment is an anti-idiotypic antibody, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the total ADC and / or antibody or antigen-binding fragment in the biological sample.

35. The method of claim 33 or claim 34, wherein the anti-idiotypic antibody or antigen- binding fragment comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chainAttorney Docket No.15648.0054-00304 complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system.

36. The method of any one of claims 33 to 35, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286, optionally wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO:

288.

37. The method of any one of claims 28 to 36, wherein (a) the first antibody or antigen-binding fragment is conjugated to a biotin or a bead, preferably a biotin, optionally wherein the first antibody or antigen-binding fragment is immobilized on a solid support; and / or (b) the second antibody or antigen-binding fragment is conjugated to a detectable label, optionally wherein the detectable label is a fluorescent tag.

38. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to eribulin; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment,Attorney Docket No.15648.0054-00304 thereby detecting the intact ADC in the biological sample.

39. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-202, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-202; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC and / or an antigen-binding fragment thereof, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds farletuzumab or a fragment thereof; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to eribulin; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample.

40. The method of claim 38 or claim 39, wherein the anti-idiotypic antibody or antigen- binding fragment comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ IDAttorney Docket No.15648.0054-00304 NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system.

41. The method of any one of claims 38 to 40, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14, optionally wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO:

16.

42. The method of any one of claims 38 to 41, wherein the anti-idiotypic antibody is 2G9.

43. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109; b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to eribulin; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the second antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample.

44. A method for detecting intact antibody-drug conjugate (ADC), wherein the ADC is MORAb-109, the method comprising: a) obtaining a biological sample from a subject who has been administered MORAb-109;Attorney Docket No.15648.0054-00304 b) contacting the biological sample with a first antibody or antigen-binding fragment capable of specifically binding to an antibody portion of the ADC, wherein the first antibody or antigen-binding fragment comprises an anti-human IgG Fc antibody or antigen-binding fragment or an anti-idiotypic antibody or antigen-binding fragment, wherein the anti-idiotypic antibody specifically binds 345A12-HC15-LC4 or a fragment thereof; c) contacting the biological sample with a second antibody or antigen-binding fragment capable of specifically binding to eribulin; and d) detecting a signal from the second antibody or antigen-binding fragment, thereby detecting the intact ADC in the biological sample.

45. The method of claim 43 or claim 44, wherein the anti-idiotypic antibody or antigen- binding fragment comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system.

46. The method of any one of claims 43 to 45, wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286,Attorney Docket No.15648.0054-00304 optionally wherein the anti-idiotypic antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO:

288.

47. The method of any one of claims 38 to 46, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin comprises (a) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30; or (b) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system.

48. The method of any one of claims 38 to 47, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30, optionally wherein first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin is an antigen-binding fragment, preferably a Fab fragment, optionally wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 31 or SEQ ID NO: 294, and a light chain comprising an amino acid sequence of SEQ ID NO: 32.Attorney Docket No.15648.0054-00304 49. The method of any one of claims 38 to 48, wherein the first and / or second antibody or antigen-binding fragment capable of specifically binding to eribulin is 5E4.

50. The method of any one of claims 38 to 49, wherein (a) the first antibody or antigen-binding fragment is conjugated to a biotin or a bead, preferably a biotin, optionally wherein the first antibody or antigen-binding fragment is immobilized on a solid support; and / or (b) the second antibody or antigen-binding fragment is conjugated to a detectable label, optionally wherein the detectable label is a fluorescent tag.

51. A method for detecting intact and / or total antibody-drug conjugate (ADC) and / or a metabolite of an ADC, wherein the metabolite is unconjugated antibody or antigen-binding fragment, linker-payload, and / or free payload, comprising two or more of: a) the method of any one of claims 1 to 27; b) the method of any one of claims 28 to 37; c) the method of any one of claims 38, 40 to 43, or 45 to 50; d) the method of any one of claims 39 to 42, or 44 to 50; and e) a method comprising quantification of free payload, wherein the free payload is eribulin, wherein the eribulin is quantified by multiple reaction monitoring.

52. An antibody or antigen-binding fragment thereof capable of binding to an antibody- drug conjugate comprising farletuzumab and / or to farletuzumab or an antigen-binding fragment thereof, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO:

14.

53. The antibody or antigen-binding fragment of claim 52, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 1 (HCDR1), SEQ ID NO: 2 (HCDR2), and SEQ ID NO: 3 (HCDR3); and three light chain complementarity determining regionsAttorney Docket No.15648.0054-00304 comprising amino acid sequences of SEQ ID NO: 4 (LCDR1), SEQ ID NO: 5 (LCDR2), and SEQ ID NO: 6 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 7 (HCDR1), SEQ ID NO: 8 (HCDR2), and SEQ ID NO: 9 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 10 (LCDR1), SEQ ID NO: 11 (LCDR2), and SEQ ID NO: 12 (LCDR3), as defined by the IMGT numbering system.

54. The antibody or antigen-binding fragment of claim 52 or claim 53, wherein the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 13, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 14, optionally wherein the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 15, and a light chain comprising an amino acid sequence of SEQ ID NO:

16.

55. An antibody or antigen-binding fragment thereof capable of binding to an antibody- drug conjugate comprising 345A12-HC15-LC4 and / or to 345A12-HC15-LC4 or an antigen- binding fragment thereof, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO:

286.

56. The antibody or antigen-binding fragment of claim 55, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 273 (HCDR1), SEQ ID NO: 274 (HCDR2), and SEQ ID NO: 275 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 276 (LCDR1), SEQ ID NO: 277 (LCDR2), and SEQ ID NO: 278 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 279 (HCDR1), SEQ ID NO: 280 (HCDR2), and SEQ ID NO: 281Attorney Docket No.15648.0054-00304 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 282 (LCDR1), SEQ ID NO: 283 (LCDR2), and SEQ ID NO: 284 (LCDR3), as defined by the IMGT numbering system.

57. The antibody or antigen-binding fragment of claim 55 or claim 56, wherein the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 285, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 286, optionally wherein the antibody or antigen-binding fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID NO: 287, and a light chain comprising an amino acid sequence of SEQ ID NO:

288.

58. An antibody or antigen-binding fragment thereof capable of binding to eribulin, wherein the antibody or antigen-binding fragment comprises (i) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30; (ii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 101, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 102; (iii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 119, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 120; (iv) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 137, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 138; (v) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 153, and three light chainAttorney Docket No.15648.0054-00304 complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 154; (vi) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 169, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 170; (vii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 183, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 184; (viii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 200, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 201; (ix) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 217, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 218; or (x) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 234, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO:

235.

59. The antibody or antigen-binding fragment thereof of claim 58, wherein the antibody or antigen-binding fragment comprises (i) three heavy chain complementarity determining regions (HCDRs) comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions (LCDRs) comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three lightAttorney Docket No.15648.0054-00304 chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system; (ii) three HCDRs comprising amino acid sequences of SEQ ID NO: 89 (HCDR1), SEQ ID NO: 90 (HCDR2), and SEQ ID NO: 91 (HCDR3); and three LCDRs comprising SEQ ID NO: 92 (LCDR1), SEQ ID NO: 93 (LCDR2), and SEQ ID NO: 94 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 95 (HCDR1), SEQ ID NO: 96 (HCDR2), and SEQ ID NO: 97 (HCDR3); and three LCDRs comprising SEQ ID NO: 98 (LCDR1), SEQ ID NO: 99 (LCDR2), and SEQ ID NO: 100 (LCDR3) as defined by the IMGT numbering system; (iii) three HCDRs comprising amino acid sequences of SEQ ID NO: 107 (HCDR1), SEQ ID NO: 108 (HCDR2), and SEQ ID NO: 109 (HCDR3); and three LCDRs comprising SEQ ID NO: 110 (LCDR1), SEQ ID NO: 111 (LCDR2), and SEQ ID NO: 112 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 113 (HCDR1), SEQ ID NO: 114 (HCDR2), and SEQ ID NO: 115 (HCDR3); and three LCDRs comprising SEQ ID NO: 116 (LCDR1), SEQ ID NO: 117 (LCDR2), and SEQ ID NO: 118 (LCDR3) as defined by the IMGT numbering system; (iv) three HCDRs comprising amino acid sequences of SEQ ID NO: 125 (HCDR1), SEQ ID NO: 126 (HCDR2), and SEQ ID NO: 127 (HCDR3); and three LCDRs comprising SEQ ID NO: 128 (LCDR1), SEQ ID NO: 129 (LCDR2), and SEQ ID NO: 130 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 131 (HCDR1), SEQ ID NO: 132 (HCDR2), and SEQ ID NO: 133 (HCDR3); and three LCDRs comprising SEQ ID NO: 134 (LCDR1), SEQ ID NO: 135 (LCDR2), and SEQ ID NO: 136 (LCDR3) as defined by the IMGT numbering system; (v) three HCDRs comprising amino acid sequences of SEQ ID NO: 143 (HCDR1), SEQ ID NO: 144 (HCDR2), and SEQ ID NO: 145 (HCDR3); and three LCDRs comprising SEQ ID NO: 146 (LCDR1), SEQ ID NO: 129 (LCDR2), and SEQ ID NO: 147 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 148 (HCDR1), SEQ ID NO: 149 (HCDR2), and SEQ ID NO: 150 (HCDR3); and three LCDRs comprising SEQ ID NO: 151 (LCDR1), SEQ ID NO: 135 (LCDR2), and SEQ ID NO: 152 (LCDR3) as defined by the IMGT numbering system;Attorney Docket No.15648.0054-00304 (vi) three HCDRs comprising amino acid sequences of SEQ ID NO: 159 (HCDR1), SEQ ID NO: 160 (HCDR2), and SEQ ID NO: 161 (HCDR3); and three LCDRs comprising SEQ ID NO: 162 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 163 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 164 (HCDR1), SEQ ID NO: 165 (HCDR2), and SEQ ID NO: 166 (HCDR3); and three LCDRs comprising SEQ ID NO: 167 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 168 (LCDR3) as defined by the IMGT numbering system; (vii) three HCDRs comprising amino acid sequences of SEQ ID NO: 175 (HCDR1), SEQ ID NO: 176 (HCDR2), and SEQ ID NO: 109 (HCDR3); and three LCDRs comprising SEQ ID NO: 177 (LCDR1), SEQ ID NO: 111 (LCDR2), and SEQ ID NO: 178 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 179 (HCDR1), SEQ ID NO: 180 (HCDR2), and SEQ ID NO: 115 (HCDR3); and three LCDRs comprising SEQ ID NO: 181 (LCDR1), SEQ ID NO: 117 (LCDR2), and SEQ ID NO: 182 (LCDR3) as defined by the IMGT numbering system; (viii) three HCDRs comprising amino acid sequences of SEQ ID NO: 189 (HCDR1), SEQ ID NO: 190 (HCDR2), and SEQ ID NO: 191 (HCDR3); and three LCDRs comprising SEQ ID NO: 192 (LCDR1), SEQ ID NO: 193 (LCDR2), and SEQ ID NO: 194 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 195 (HCDR1), SEQ ID NO: 196 (HCDR2), and SEQ ID NO: 197 (HCDR3); and three LCDRs comprising SEQ ID NO: 198 (LCDR1), SEQ ID NO: 117 (LCDR2), and SEQ ID NO: 199 (LCDR3) as defined by the IMGT numbering system; (ix) three HCDRs comprising amino acid sequences of SEQ ID NO: 206 (HCDR1), SEQ ID NO: 207 (HCDR2), and SEQ ID NO: 208 (HCDR3); and three LCDRs comprising SEQ ID NO: 92 (LCDR1), SEQ ID NO: 209 (LCDR2), and SEQ ID NO: 210 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 211 (HCDR1), SEQ ID NO: 212 (HCDR2), and SEQ ID NO: 213 (HCDR3); and three LCDRs comprising SEQ ID NO: 214 (LCDR1), SEQ ID NO: 215 (LCDR2), and SEQ ID NO: 216 (LCDR3) as defined by the IMGT numbering system; or (x) three HCDRs comprising amino acid sequences of SEQ ID NO: 223 (HCDR1), SEQ ID NO: 224 (HCDR2), and SEQ ID NO: 225 (HCDR3); and three LCDRs comprising SEQ ID NO: 226 (LCDR1), SEQ ID NO: 227 (LCDR2), and SEQ ID NO: 228 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acidAttorney Docket No.15648.0054-00304 sequences of SEQ ID NO: 229 (HCDR1), SEQ ID NO: 230 (HCDR2), and SEQ ID NO: 231 (HCDR3); and three LCDRs comprising SEQ ID NO: 232 (LCDR1), SEQ ID NO: 99 (LCDR2), and SEQ ID NO: 233 (LCDR3) as defined by the IMGT numbering system.

60. The antibody or antigen-binding fragment thereof of claim 58 or claim 59, wherein the antibody or antigen-binding fragment comprises three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 17 (HCDR1), SEQ ID NO: 18 (HCDR2), and SEQ ID NO: 19 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 20 (LCDR1), SEQ ID NO: 21 (LCDR2), and SEQ ID NO: 22 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 23 (HCDR1), SEQ ID NO: 24 (HCDR2), and SEQ ID NO: 25 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 26 (LCDR1), SEQ ID NO: 27 (LCDR2), and SEQ ID NO: 28 (LCDR3), as defined by the IMGT numbering system.

61. The antibody or antigen-binding fragment of claim 58 or claim 59, wherein the antibody or antigen-binding fragment comprises (i) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 30; (ii) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 101, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 102; (iii) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 119, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 120; (iv) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 137, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 138;Attorney Docket No.15648.0054-00304 (v) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 153, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 154; (vi) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 169, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 170; (vii) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 183, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 184; (viii) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 200, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 201; (ix) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 217, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 218; or (x) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 234, and a light chain variable region comprising the amino acid sequence of SEQ ID NO:

235.

62. The antibody or antigen-binding fragment of any one of claims 58 to 61, wherein the antibody or antigen-binding fragment comprises a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 29, and a light chain variable region comprising an amino acid sequence of SEQ ID NO:

30.

63. The antibody or antigen-binding fragment of any one of claims 58 to 62, wherein the antibody or antigen-binding fragment is an antigen-binding fragment, preferably a Fab fragment.

64. The antibody or antigen-binding fragment of any one of claims 58 to 63, wherein the antibody or antigen-binding fragment comprises (i) a heavy chain comprising an amino acid sequence of SEQ ID NO: 31 or 294 and a light chain comprising an amino acid sequence of SEQ ID NO: 32;Attorney Docket No.15648.0054-00304 (ii) a heavy chain comprising an amino acid sequence of SEQ ID NO: 103 and a light chain comprising an amino acid sequence of SEQ ID NO: 104; (iii) a heavy chain comprising an amino acid sequence of SEQ ID NO: 121 and a light chain comprising an amino acid sequence of SEQ ID NO: 122; (iv) a heavy chain comprising an amino acid sequence of SEQ ID NO: 139 and a light chain comprising an amino acid sequence of SEQ ID NO: 140; (v) a heavy chain comprising an amino acid sequence of SEQ ID NO: 155 and a light chain comprising an amino acid sequence of SEQ ID NO: 156; (vi) a heavy chain comprising an amino acid sequence of SEQ ID NO: 171 and a light chain comprising an amino acid sequence of SEQ ID NO: 172; (vii) a heavy chain comprising an amino acid sequence of SEQ ID NO: 185 and a light chain comprising an amino acid sequence of SEQ ID NO: 186; (viii) a heavy chain comprising an amino acid sequence of SEQ ID NO: 202 and a light chain comprising an amino acid sequence of SEQ ID NO: 203; (ix) a heavy chain comprising an amino acid sequence of SEQ ID NO: 219 and a light chain comprising an amino acid sequence of SEQ ID NO: 220; or (x) a heavy chain comprising an amino acid sequence of SEQ ID NO: 236 and a light chain comprising an amino acid sequence of SEQ ID NO:

237.

65. An antibody or antigen-binding fragment thereof capable of binding to Val-Cit-pAB (“VCP”), wherein the antibody or antigen-binding fragment comprises (i) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46; or (ii) three heavy chain complementarity determining regions from a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 248, and three light chain complementarity determining regions from a light chain variable region comprising an amino acid sequence of SEQ ID NO:

249.

66. The antibody or antigen-binding fragment thereof of claim 65, wherein the antibody or antigen-binding fragment comprisesAttorney Docket No.15648.0054-00304 (i) three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 33 (HCDR1), SEQ ID NO: 34 (HCDR2), and SEQ ID NO: 35 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 36 (LCDR1), SEQ ID NO: 37 (LCDR2), and SEQ ID NO: 38 (LCDR3), as defined by the Kabat numbering system; or three heavy chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 39 (HCDR1), SEQ ID NO: 40 (HCDR2), and SEQ ID NO: 41 (HCDR3); and three light chain complementarity determining regions comprising amino acid sequences of SEQ ID NO: 42 (LCDR1), SEQ ID NO: 43 (LCDR2), and SEQ ID NO: 44 (LCDR3), as defined by the IMGT numbering system; or (ii) three HCDRs comprising amino acid sequences of SEQ ID NO: 159 (HCDR1), SEQ ID NO: 240 (HCDR2), and SEQ ID NO: 241 (HCDR3); and three LCDRs comprising SEQ ID NO: 242 (LCDR1), SEQ ID NO: 209 (LCDR2), and SEQ ID NO: 243 (LCDR3) as defined by the Kabat numbering system; or three HCDRs comprising amino acid sequences of SEQ ID NO: 164 (HCDR1), SEQ ID NO: 244 (HCDR2), and SEQ ID NO: 245 (HCDR3); and three LCDRs comprising SEQ ID NO: 246 (LCDR1), SEQ ID NO: 215 (LCDR2), and SEQ ID NO: 247 (LCDR3) as defined by the IMGT numbering system.

67. The antibody or antigen-binding fragment of claim 65 or claim 66, wherein the antibody or antigen-binding fragment comprises (i) a heavy chain variable region comprising an amino acid sequence of SEQ ID NO: 45, and a light chain variable region comprising an amino acid sequence of SEQ ID NO: 46; (ii) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 248, and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 249; (iii) a heavy chain comprising an amino acid sequence of SEQ ID NO: 47, and a light chain comprising an amino acid sequence of SEQ ID NO: 48; or (iv) a heavy chain comprising an amino acid sequence of SEQ ID NO: 250, and a light chain comprising an amino acid sequence of SEQ ID NO: 251.Attorney Docket No.15648.0054-00304 68. The antibody or antigen-binding fragment of any one of claims 52 to 67, wherein the antibody or antigen-binding fragment is conjugated to a label, optionally wherein the label comprises a fluorescent tag, an enzyme reporter, a biotin, or a bead.