CONJUGADOS ANTICORPO-FÁRMACO DLL3 E USOS DESTES

Abstract

The present disclosure provides DLL3 antibody-drug conjugates and uses thereof.

Description

[0001] This application claims the benefit of Provisional Patent Application No. US 63 / 454,009, filed March 22, 2023, disclosure of which is incorporated herein by reference in its entirety. SEQUENCE LISTING

[0002] This application contains a machine-readable Sequence Listing that was submitted in XML file format with this application, the entire contents of which are incorporated by reference herein in their entirety. The sequence listing XML file submitted with this application is titled “14529-133-228_SEQ_LISTING.xml”, was created on March 20, 2024, and is 49,227 bytes in size. FIELD

[0003] This disclosure relates generally to antibody-drug conjugates (ADCs) comprising antibodies against the canonical Delta-Notch type ligand (DLL3) and methods of their use. FUNDAMENTALS

[0004] The Delta-type Canonical Notch Ligand 3 (DLL3) is a type I transmembrane protein belonging to the DSL family of Notch ligands. This protein is generally expressed exclusively on intracellular membranes, especially in the Golgi apparatus. Additional Notch family ligands include Delta-type Canonical Notch Ligand 1 (D1), Delta-type Canonical Notch Ligand 4 (D4), Jag-type Canonical Notch Ligand 1 (J1), and Jag-type Canonical Notch Ligand 2 (J2). With the exception of DLL3, the other ligands can activate Notch signaling. DLL3 acts as an inhibitor of Notch signaling by interfering with the binding between Notch and its ligands. DLL3 is highly expressed on the surface of lung tumor cells, including small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma (LCNEC). Although generally expressed exclusively on intracellular membranes, DLL3 is a potential Petition 870250084316, dated 09 / 18 / 2025, p. 197 / 503 2 / 203 therapeutic tumor target for any tumor expressing DLL3, including SCLC and NSCLC. In recent years, the establishment of DLL3 as a unique target in SCLC has accelerated the development of therapeutic agents. However, therapeutic success with antibodies and ADCs targeting DLL3 has not yet been achieved.

[0005] There is still a need in the technique for ADCs that can target DLL3 to treat, prevent or alleviate DLL3-mediated diseases, disorders or conditions, including lung cancer, such as small cell lung cancer (SCLC) or large cell neuroendocrine carcinoma (LCNEC). SUMMARY

[0006] In one aspect, an antibody-drug conjugate (ADC) of Formula (I) is provided here: (I) or a salt thereof, where n is an integer from 1 to 8, and Ab represents an antibody that binds to DLL3 (“DLL3 antibody”), where the point Petition 870250084316, dated 09 / 18 / 2025, pp. 198 / 503 3 / 203 of the drug conjugate's binding to Ab is via a cysteine ​​or lysine residue of the DLL3 antibody. In certain embodiments, n is 2. In certain embodiments, n is 4. In some embodiments, the ADC is Formula (lA) or a salt thereof. In other forms, the ADC is Formula (lB) or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 199 / 503 4 / 203 Petition 870250084316, dated 09 / 18 / 2025, pp. 200 / 503 5 / 203 where each thick shaded line represents a chain of the DLL3 antibody, the sulfurs shown are cysteine ​​residues of the DLL3 antibody, and X represents the structure below or a salt thereof: where the wavy line represents the connection point for the remainder of the ADC of Formula (A). In some embodiments, the cysteine ​​residues are in the hinge region of the DLL3 antibody. In other embodiments, the cysteine ​​residues form an interchain disulfide bridge in a DLL3 antibody not directly or indirectly conjugated to X, for example, between two heavy chains, between a heavy chain and a light chain, between two VHH chains, or between two VHH-Fc chains. In other embodiments, the cysteine ​​residue is at one or more of the 226 or 229 positions according to the EU numbering (also referred to herein as C226 or C229, respectively). In some embodiments, X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 201 / 503 6 / 203 OH In other forms, X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 202 / 503 7 / 203 OH This document provides an ADC of

[0008] In another aspect, Formula (B): Petition 870250084316, dated 09 / 18 / 2025, pp. 203 / 503 8 / 203 VV (B), where each thick shaded line represents a chain of the DLL3 antibody, the CH2CH2CH2CH2NH cluster shown comes from a lysine residue of the CH2 domain of the DLL3 antibody, and X represents the structure below: Petition 870250084316, dated 09 / 18 / 2025, pp. 204 / 503 9 / 203 HO where the wavy line represents the connection point for the remainder of the ADC of Formula (B). In some embodiments, the lysine residue is at one or more of the positions 246, 248, 288, 290 or 317 according to the EU numbering (also referred to in this document as K246, K248, K288, K290 or K317, respectively). In some embodiments, X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 205 / 503 10 / 203 OH In other forms, X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 206 / 503 11 / 203 OH

[0009] In another aspect, an ADC of Formula (II) is provided in this document: the (II) where n is an integer from 1 to 8, and Ab represents an antibody Petition 870250084316, dated 09 / 18 / 2025, pp. 207 / 503 12 / 203 DLL3. In some embodiments, the binding site of the drug conjugate to Ab is via a cysteine ​​or lysine residue of the DLL3 antibody. In certain embodiments, n is 2. In certain embodiments, n is 4. In some embodiments, the ADC is Formula (ll-A) or a salt thereof: (ll-A) In other forms, the ADC is from Formula (Il-B) or a salt thereof: (ll-B) Petition 870250084316, dated 09 / 18 / 2025, pp. 208 / 503 13 / 203

[0010] In another aspect, an ADC of Formula (A) is provided in this document: where each thick shaded line represents a chain of a DLL3 antibody, the sulfurs shown are from cysteine ​​residues of the DLL3 antibody, and X represents the structure below: the Petition 870250084316, dated 09 / 18 / 2025, pp. 209 / 503 14 / 203 where the wavy line represents the connection point for the remainder of the ADC of Formula (A). In some embodiments, the cysteine ​​residues are in the hinge region of the DLL3 antibody. In other embodiments, the cysteine ​​residues form an interchain disulfide bridge in a DLL3 antibody not directly or indirectly conjugated to X, for example, between two heavy chains, between a heavy chain and a light chain, between two VHH chains, or between two VHH-Fc chains. In other embodiments, the cysteine ​​residue is at one or more of the 226 or 229 positions according to the EU numbering (also referred to herein as C226 or C229, respectively). In some embodiments, X represents the structure below or a salt thereof: OH In some forms, X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, p. 210 / 503 15 / 203 In this respect, an ADC is provided in this document.

[0011] In another where each thick shaded line represents a chain of one Petition 870250084316, dated 09 / 18 / 2025, p. 211 / 503 16 / 203 DLL3 antibody, the CH2CH2CH2CH2NH cluster shown originates from a lysine residue in the CH2 domain of the DLL3 antibody, and X represents the structure below: where the wavy line represents the connection point for the remainder of the ADC of Formula (B). In some embodiments, the lysine residue is at one or more of the positions 246, 248, 288, 290 or 317 according to the EU numbering (also referred to in this document as K246, K248, K288, K290 or K317, respectively). In some embodiments, X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, p. 212 / 503 17 / 203 In some forms, X represents the structure below or a salt thereof: CT OH

[0012] In some embodiments, the DLL3 antibody, as used herein, comprises a VHH. In other embodiments, the DLL3 antibody, as used herein, comprises a VHH-Fc fusion, for example, as illustrated in Figure 1A. Additionally or alternatively, the DLL3 antibody comprises a CDR1, CDR2, and CDR3 of a variable heavy chain (VH) domain, wherein the VH comprises an amino acid sequence as set forth in SEQ ID NO: 14, 15, or 16, for example, as those disclosed in Table 1 and Table 2. In other embodiments, the DLL3 antibody comprises a VH as set forth in SEQ ID NO: 14, 15, or 16. In further embodiments, the DLL3 antibody comprises a homodimer of a VHH-Fc chain as set forth in any of the SEQ ID NO: 4, 5, or 10.

[0013] In another aspect, a pharmaceutical composition comprising an ADC described in this document and a pharmaceutically acceptable carrier is provided in this document. In some embodiments, the pharmaceutical composition has a drug-antibody ratio (DAR) of about 1.5 to about 2.5. In other embodiments, the pharmaceutical composition has a DAR of Petition 870250084316, dated 09 / 18 / 2025, p. 213 / 503 18 / 203 approximately 1.9 to 2.1. In some embodiments, the pharmaceutical composition has a DAR of approximately 1 to approximately 4, for example, approximately 1 to approximately 3, approximately 1 to approximately 2, approximately 2 to approximately 4, or approximately 3 to approximately 4. In other embodiments, the pharmaceutical composition has a DAR of approximately 3.5 to approximately 4.0, such as approximately 3.6, approximately 3.7, approximately 3.8, approximately 3.9, or approximately 4.0.

[0014] In another aspect, a method of modulating a DLL3-related immune response in a subject is provided in this document, comprising administering to the subject an ADC or a pharmaceutical composition described in this document, such that an immune response is modulated in the subject.

[0015] In another aspect, a method for treating cancer in a subject is provided in this document, comprising administering to the subject an ADC or a pharmaceutical composition described in this document, wherein the cancer is positive for DLL3 or exhibits DLL3 overexpression. In certain embodiments, the cancer is selected from lung cancer and neuroendocrine carcinoma. In certain embodiments, the cancer is small cell lung cancer (SCLC), large cell neuroendocrine carcinoma (LCNEC), or colorectal cancer.

[0016] In other respects, methods for making an ADC are provided here and described herein. BRIEF DESCRIPTION OF THE FIGURES

[0017] Figure 1A shows an antibody comprising VHH fused to an Fc. Two interchain disulfide bonds may be present between the hinge regions of the two chains.

[0018] Figure 1B provides exemplary synthesis routes for ADCs, where the antibody can be a conventional antibody comprising two heavy chains and two light chains, or a VHH-Fc fusion, as illustrated in Figure 1A.

[0019] Figure 2 provides an exemplary RP-HPLC analysis result of Petition 870250084316, dated 09 / 18 / 2025, p. 214 / 503 19 / 203 Binding Drug (2-A), Binding Drug (2-B) and Binding Drug (2) (mixture of Binding Drug (2-A) and Binding Drug (2-B)), described in more detail in Example 7.

[0020] Figure 3 illustrates the Binding Drug (2-B).

[0021] Figures 4A-4D show exemplary results for mAb300, mAb301, mAb302 and relevant ADCs from development assays, described in more detail in Example 15. Figure 4A compares mAb302, ADC-013 and ADC-014 using size exclusion chromatography (SEC). Figure 4B compares mAb300 and mAb302 using hydrophobic interaction chromatography (HIC). Figure 4C compares mAb300, ADC-009 and ADC-010 using HIC. Figure 4D compares mAb302, ADC-013 and ADC-014 using HIC.

[0022] Figure 5 shows exemplary results from the evaluation of the binding characteristics of mAb300, mAb301 and mAb302 using a Biacore™ assay, described in more detail in Example 16.

[0023] Figure 6 shows exemplary results of the drug-antibody ratio (DAR) assessment of ADC-015 (labeled as mAb301 Drug-Binder (2) (target DAR = 2.0)), ADC-016 (labeled as mAb301-Drug-Binder (2) (target DAR = 4.0)) and ADC-017 (labeled as mAb301-Drug-Binder (1) (target DAR = 4.0)), described in more detail in Example 17.

[0024] Figures 7A-7R provide exemplary SEC-HPLC analysis results of the produced ADC-009-M (mAb300, Ligand-Drug (2), DAR2, Figure 7A), ADC-009-A (mAb300, Ligand-Drug (2-A), DAR2, Figure 7B), ADC009-B (mAb300, Ligand-Drug (2-B), DAR2, Figure 7C), ADC-015-M (mAb301, Ligand-Drug (2), DAR2, Figure 7D), ADC-015-A (mAb301, Ligand-Drug (2A), DAR2, Figure 7E), ADC-015-B (mAb301, Ligand-Drug (2-B), DAR2, Figure 7F), ADC-013-M (mAb302, Ligand-Drug (2) ADC-018-A (mAb300, Ligand-Drug (2-A), DAR4, Figure 7K), ADC-018-B (mAb300, Ligand-Drug (2-B), DAR4, Figure 7L), ADC-016-M Petition 870250084316, dated 09 / 18 / 2025, page 215 / 503 20 / 203 (mAb301, Drug-Ligant (2), DAR4, Figure 7M), ADC-016-A (mAb301, Drug-Ligant (2-A), DAR4, Figure 7N), ADC-016-B (mAb301, Drug-Ligant (2-B), DAR4, Figure 7O), ADC-020-M (mAb302, Drug-Ligant (2), DAR4, Figure 7P), ADC-020-A (mAb302, Drug-Ligant (2-A), DAR4, Figure 7Q), ADC-020-B (mAb302, Drug-Ligant (2-B), DAR4, Figure 7R), described in more detail in Example 18.

[0025] Figures 8A-8R provide exemplary HIC-HPLC analysis results of the produced ADCs: ADC-009-M (mAb300, Binding Drug (2), DAR2, Figure 8A), ADC-009-A (mAb300, Binding Drug (2-A), DAR2, Figure 8B), ADC-009-B (mAb300, Binding Drug (2-B), DAR2, Figure 8C), ADC-015M (mAb301, Binding Drug (2), DAR2, Figure 8D), ADC-015-A (mAb301, Binding Drug (2-A), DAR2, Figure 8E), ADC-015-B (mAb301, Binding Drug (2-B), DAR2, Figure 8F), ADC-013-M (mAb302, Drug Binding (2), DAR2, Figure 8G), ADC-013-A (mAb302, Drug Binding (2-A), DAR2, Figure 8H), ADC-013-B (mAb302, Drug Binding (2-B), DAR2, Figure 8I), ADC-018-M (mAb300, Drug Binding (2), DAR4, Figure 8J), ADC-018-A (mAb300, Drug Linker (2-A), DAR4, Figure 8K), ADC-018-B (mAb300, Drug Linker (2-B), DAR4, Figure 8L), ADC-016-M (mAb301, Drug Linker (2), DAR4, Figure 8M), ADC-016-A (mAb301, Drug Linker (2-A), DAR4, Figure 8N), ADC-016-B (mAb301, Drug Binding (2-B), DAR4, Figure 8O), ADC-020-M (mAb302, Drug Binding (2),DAR4, Figure 8P), ADC-020-A (mAb302, Binding Drug (2-A), DAR4, Figure 8Q) and ADC-020-B (mAb302, Binding Drug (2-B), DAR4, Figure 8R), as described in detail in Example 18.

[0026] Figures 9A-9E provide exemplary results from cytotoxicity assays investigating the effects of ADC-015, ADC-016, and ADC-017 on hDLL3-overexpressing B16F10 cells, described in more detail in Example 17. Figure 9A compares various concentrations of MMAE, Exatecan, and ADC-017 after 72 hours of incubation. Figure 9B compares various concentrations of MMAE, Exatecan, and ADC-017 after 96 hours of incubation. The corresponding IC50 and maximum inhibition percentages were calculated and Petition 870250084316, dated 09 / 18 / 2025, page 216 / 503 21 / 203 are presented in Figure 9C. In addition, Figure 9D compares various concentrations of MMAE, Exatecan, ADC-015, ADC-016, ADC-017, IgG1 Fc conjugated to Exatecan, and IgG1 Fc conjugated to MMAE after 72 hours of incubation, while Figure 9E presents the corresponding IC50 and maximum inhibition percentages.

[0027] Figures 10A-10E provide exemplary results from in vitro cytotoxicity assays investigating the effects of ADC-015-M, ADC-015-A, ADC-015-B, ADC-016-M, ADC-016-A, and ADC-016-B on a DLL3-overexpressing 293F cell line, as described in detail in Example 20. Figures 10A and 10B plot the data from a first experiment, while Figure 10A plots the concentrations of the tested ADCs on the x-axis and Figure 10B plots the calibrated concentrations of the ligand payloads of the tested ADCs on the x-axis. Figures 10C and 10D represent the data from a second experiment, while Figure 10C shows the concentrations of the tested ADCs on the x-axis and Figure 10D shows the calibrated concentrations of the ligand-payload conjugates of the tested ADCs on the x-axis. Figure 10E represents the data from a third experiment.

[0028] Figures 11A-11F provide exemplary results from cytotoxicity assays investigating the effect of ADC-015, ADC-016, and ADC-017 on H69 cells, as described in detail in Example 21. Figures 11A, 11C, and 11E compare various concentrations of MMAE, Exatecan, ADC015, ADC-016, and ADC-017 after 120 hours of incubation, while their IC50 percentages and maximum inhibition are presented in Figures 11B, 11D, and 11F, respectively.

[0029] Figures 12A-12D provide exemplary results from cytotoxicity assays investigating the effects of ADC-015, ADC-016, and ADC-017 on CORL279 cells, as described in detail in Example 21. Figures 12A and 12C compare different concentrations of MMAE, Exatecan, ADC-015, ADC-016, and ADC-017 after 120 hours of incubation, while their IC50 values ​​and maximum percentages of inhibition are presented in Petition 870250084316, dated 09 / 18 / 2025, page 217 / 503 22 / 203 Figures 12B and 12D, respectively.

[0030] Figures 13A-13B provide exemplary results from cytotoxicity assays investigating the effects of ADC-015, ADC-016, and ADC-017 on SHP77 cells, as described in detail in Example 21. Figure 13A compares different concentrations of MMAE, Exatecan, ADC-015, ADC-016, and ADC-017 after 120 hours of incubation, while the corresponding IC50 values ​​and maximum inhibition percentages are presented in Figure 13B.

[0031] Figures 14A-14B provide exemplary results from cytotoxicity assays investigating the effects of ADC-015, ADC-016, and ADC-017 on H460 cells, as described in detail in Example 21. Figure 14A compares different concentrations of MMAE, Exatecan, ADC-015, ADC-016, and ADC-017 after 120 hours of incubation, while the corresponding IC50 values ​​and maximum inhibition percentages are presented in Figure 14B.

[0032] Figures 15A-15E provide exemplary results from cytotoxicity assays investigating the effects of ADC-009 and ADC-010 on SHP77 cells (Figure 15A), DMS79 cells (Figure 15B), H69 cells (Figure 15C), and CORL279 cells (Figure 15D), described in more detail in Example 22. The corresponding IC50 and maximum inhibition percentages were calculated and are presented in Figure 15E.

[0033] Figures 16A-16F represent tumor volume (TV) measurements from mice implanted with SHP77 small cell lung cancer (SCLC) cells and treated with the indicated compounds, described in more detail in Example 23. Figures 16A, 16C, and 16E represent data during the observation period, while Figures 16B and 16D compare Day 28 (D28) data, and Figure 16F represents Day 24 (D24) data.

[0034] Figures 17A-17K provide spider graphs of mice implanted with SHP77 CPPC cells and treated with the indicated compounds (Figure 17A, Vehicle; Figure 17B, DAR 2 ADC 1 isotype). Petition 870250084316, dated 09 / 18 / 2025, page 218 / 503 23 / 203 mg / kg; Figure 17C, DAR 4 ADC isotype 1 mg / kg; Figure 17D, ADC-015-B 3 mg / kg; Figure 17E, ADC-015-B 1 mg / kg; Figure 17F, ADC-015-B 0.3 mg / kg x3; Figure 17G, ADC-015-M 1 mg / kg; Figure 17H, ADC-016-B 3 mg / kg; Figure 17I, ADC-016-B 1 mg / kg; Figure 17J, ADC-016-B 0.3 mg / kg x3; Figure 17K, ADC016-M 1 mg / kg;), described in more detail in Example 23.

[0035] Figures 18A-18I provide data obtained from the CXF 742 PDX model, described in more detail in Example 24. Figure 18A provides an exemplary IHC staining image of the CXF 742 tumor sample. Figure 18B represents the absolute tumor volumes of the tested groups during the observation period (the mean TV of the group was plotted until two animals were removed from the group due to the TV endpoint). Figure 18C represents the tumor volumes on Day 45 (D45) (mixed-effect analysis was performed using Dunnett's post-hoc test versus vehicle group). Figures 18D-18G provide spider plots of mice treated with the indicated compounds (Figure 18D, Vehicle; Figure 18E, ADC-016-M, 5 mg / kg x 1; Figure 18F, ADC-016-M, 5 mg / kg x 2; Figure 18G, ADC-015-M, 5 mg / kg x 1). Figure 18H represents the relative tumor volumes of the tested groups during the observation period.Figure 18I represents the relative tumor volumes of the groups tested during the observation period.

[0036] Figures 19A-19I provide data obtained from the LXFS 2156 PDX model, described in more detail in Example 24. Figure 19A provides an exemplary IHC staining image of the LXFS 2156 tumor sample. Figure 19B represents the absolute tumor volumes of the tested groups during the observation period (the mean TV of the group was plotted until two animals were removed from the group due to the TV endpoint). Figure 19C represents the tumor volumes on Day 31 (D31) (mixed-effect analysis, Dunnett post-test versus vehicle group). Figures 19D-19G provide spider graphs of mice treated with the indicated compounds (Figure 19D, Vehicle; Figure 19E, ADC-016-M, 5 mg / kg x 1; Figure 19F, ADC-016-M, 5 mg / kg x 2; Figure 19G, ADC-015-M, 5 mg / kg x 1). Petition 870250084316, dated 09 / 18 / 2025, page 219 / 503 24 / 203 Figure 19H represents the relative tumor volumes of the groups tested during the observation period. Figure 19I represents the relative tumor volumes of the groups tested during the observation period.

[0037] Figures 20A-20I provide data obtained from the LXFS 573 PDX model, described in more detail in Example 24. Figure 20A provides an exemplary IHC staining image of the LXFS 573 tumor sample. Figure 20B represents the absolute tumor volumes of the tested groups during the observation period. Figure 20C represents the tumor volumes on Day 46 (D46) (mixed-effect analysis, Dunnett post-test versus vehicle group). Figures 20D-20G provide spider plots of mice treated with the indicated compounds (Figure 20D, Vehicle; Figure 20E, ADC-016-M, 5 mg / kg x 1; Figure 20F, ADC-016-M, 5 mg / kg x 2; Figure 20G, ADC-015-M, 5 mg / kg x 1). Figure 20H represents the relative tumor volumes of the groups tested during the observation period. Figure 20I represents the relative tumor volumes of the groups tested during the observation period.

[0038] Figures 21A-21I provide data obtained from the CXF 94 PDX model, described in more detail in Example 24. Figure 21A provides an exemplary IHC staining image of the CXF 94 tumor sample. Figure 21B represents the absolute tumor volumes of the tested groups during the observation period (the mean TV of the group was plotted until two animals were removed from the group due to the TV endpoint). Figure 21C represents the tumor volumes on Day 31 (D31) (mixed-effect analysis, Dunnett post-test versus vehicle group). Figures 21D-21G provide spider plots of mice treated with the indicated compounds (Figure 21D, Vehicle; Figure 21E, ADC-016-M, 5 mg / kg x 1; Figure 21F, ADC-016-M, 5 mg / kg x 2; Figure 21G, ADC-015-M, 5 mg / kg x 1). Figure 21H represents the relative tumor volumes of the tested groups during the observation period.Figure 21I represents the relative tumor volumes of the groups tested during the observation period.

[0039] Figures 22A-22J provide data obtained from the LXFS 538 model. Petition 870250084316, dated 09 / 18 / 2025, page 220 / 503 25 / 203 PDX, described in more detail in Example 24. Figure 22A provides an exemplary IHC staining image of the LXFS 538 tumor sample. Figure 22B represents the absolute tumor volumes of the tested groups during the observation period (the mean TV of the group was plotted until two animals were removed from the group due to TV endpoint). Figure 22C represents the tumor volumes on Day 35 (D35), while Figure 22D shows the tumor volumes on Day 42 (D42) (mixed-effect analysis, Dunnett post-test versus vehicle group). Figures 22E-22H provide spider plots of mice treated with the indicated compounds (Figure 22E, Vehicle; Figure 22F, ADC-016-M, 5 mg / kg x 1; Figure 22G, ADC-016-M, 5 mg / kg x 2; Figure 22H, ADC-015-M, 5 mg / kg x 1). Figure 22I represents the relative tumor volumes of the tested groups during the observation period.Figure 22J represents the relative tumor volumes of the groups tested during the observation period. DETAILED DESCRIPTION

[0040] This disclosure provides an antibody-drug conjugate (ADC) comprising an antibody that binds to DLL3 and a drug conjugated (directly or indirectly) to it. These DLL3-ADCs are useful in compositions and in methods of treating, preventing, or alleviating a DLL3-mediated disease, disorder, or condition, including one or more symptoms of the disease, disorder, or condition. DLL3-mediated diseases, disorders, and conditions include cancer, for example, lung cancer (such as small cell lung cancer (SCLC)), large cell neuroendocrine carcinoma (LCNEC), or colorectal cancer. The DLL3-ADCs described herein comprise a DLL3 antibody conjugated to one or more drug-ligand conjugates.

[0041] Unless otherwise defined, all technical and scientific terms used in this document have the same meaning as commonly understood by one skilled in the art to which this invention pertains. Although any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. Petition 870250084316, dated 09 / 18 / 2025, page 221 / 503 26 / 203 invention, preferred methods and materials are now described. All publications mentioned herein are incorporated into this document by reference to disclose and describe the methods and / or materials in conjunction with which the publications are cited.

[0042] The terms about and approximately mean a variation within 20%, within 15%, within 10%, within 9%, within 8%, within 7%, within 6%, within 5%, within 4%, within 3%, within 2%, within 1% or less of a given value or range.

[0043] As used herein, comparative terms as used herein, such as reduce, decrease, increase, or any grammatical variation thereof, may refer to certain variations of the reference. In some modalities, this variation may refer to about 10%, or about 20%, or about 30%, or about 40%, or about 50%, or about 60%, or about 70%, or about 80%, or about 90%, or about 1 time, or about 2 times, or about 3 times, or about 4 times, or about 5 times, or about 10 times, or about 20 times, or about 30 times, or about 40 times, or about 100 times or more than the reference.In some modalities, such variation may refer to approximately 1%, or approximately 2%, or approximately 3%, or approximately 4%, or approximately 5%, or approximately 6%, or approximately 7%, or approximately 8%, or approximately 9%, or approximately 10%, or approximately 20%, or approximately 30%, or approximately 40%, or approximately 50%, or approximately 60%, or approximately 70%, or approximately 80%, or approximately 90%, or approximately 95%, or approximately 96%, or approximately 97%, or approximately 98%, or approximately 99% of the reference.

[0044] As used in this disclosure and claims, the singular forms a, an and the include the plural forms, unless the context clearly dictates otherwise.

[0045] In some embodiments, the terms “first,” “second,” “third,” “fourth,” and the like in a component name are used to distinguish and identify more than one component that shares a certain identity in their names. For example, “first antibody” and “second antibody” are Petition 870250084316, dated 09 / 18 / 2025, p. 222 / 503 27 / 203 used to distinguish between two antibodies.

[0046] It is understood that, whenever the modalities are described in this document with the term comprising, analogous modalities described in terms of consisting of and / or consisting essentially of are also provided. It is also understood that wherever the modalities are described in this document with the expression consisting essentially of, analogous modalities otherwise described in terms of consisting of are also provided.

[0047] The term between, as used in a phrase like between A and B or between AB, refers to an interval that includes A and B.

[0048] Thus, the term and / or, as used in an expression such as A and / or B, in this document, is intended to include A and B, A or B, A (alone) and B (alone). Similarly, the term and / or, as used in a phrase such as A, B and / or C, is intended to cover each of the following modalities: A, B and C; A, B or C; A or C; A or B; B or C; A and C; A and B; B and C; A (alone); B (alone); and C (alone).

[0049] The term optional or optionally means that the circumstance described below may or may not occur, so the description includes cases where the circumstance occurs and cases where the circumstance does not occur. DLL3 ANTIBODIES

[0050] In order to better understand the disclosure, definitions and explanations of the relevant terms are provided below.

[0051] The terms “Delta Like Canonical Notch Ligand 3”, “DLL3”, “SCDO1”, “Drosophila Delta Homolog 3”, “Delta-Like Protein 3”, “Delta3”, “D3”, “Delta (Drosophila)-Like 3”, “Delta-Like 3 (Drosophila)”, “Delta-Like 3” or similar terms refer to a polypeptide (“polypeptide” and “protein” are used interchangeably herein) or any DLL3 native to any vertebrate source, including mammals such as primates (e.g., humans, cynomolgus monkeys (cyno)), dogs, and rodents (e.g., mice and rats), the Petition 870250084316, dated 09 / 18 / 2025, p. 223 / 503 28 / 203 unless otherwise indicated. The term DLL3 encompasses “full-length” DLL3 as well as any form of DLL3 or any fragment thereof resulting from processing in the cell. The term DLL3 also encompasses naturally occurring DLL3 variants such as SNP variants, splice variants, and allelic variants. Other related DLL3 polypeptides that are also encompassed by the term DLL3 include fragments, derivatives (e.g., substitution, deletion, truncations, and insertion variants), fusion polypeptides, and interspecific homologs that retain DLL3 activity. Orthologs for the DLL3 polypeptide are also well known in the art. Exemplary DLL3 sequences and additional information can be found in GeneCards: GC19P039498; HGNC: 2909; NCBI Entrez Gene: 10683; Ensembl: ENSG00000090932; OMIM®: 602768; and UniProtKB / SwissProt: Q9NYJ7, each of which is incorporated herein by reference in its entirety.In other embodiments, an exemplary human DLL3 sequence is provided here as SEQ ID NO:11, an exemplary cyno DLL3 sequence is provided here as SEQ ID NO:12, and an exemplary murine DLL3 sequence is provided here as SEQ ID NO:13.

[0052] The term “antibody” (e.g., DLL3 antibody) is used in the broadest sense and encompasses any form of antibody that exhibits the desired biological or binding activity. This includes, but is not limited to, humanized antibodies, fully human antibodies, chimeric antibodies, and single-domain antibodies (sdAbs comprising only one chain, typically similar to a heavy chain, such as VHH), as well as fragments of any of these, provided they exhibit the desired antigen-binding activity, including, for example, an antibody comprising at least one VHH domain. A conventional antibody comprises a heavy chain (or heavy chains) and a light chain (light chains). Heavy chains can be classified as μ, δ, γ, α, and ε, which define the isotypes of an antibody as IgM, IgD, IgG, IgA, and IgE, respectively. A heavy chain may comprise a variable heavy chain (VH) region and Petition 870250084316, dated 09 / 18 / 2025, page 224 / 503 29 / 203 a constant heavy chain region (CH). A heavy chain may comprise one or more constant regions, for example, 3 constant regions (CH1, CH2 and CH3). A light chain may comprise a variable light chain region (VL) and a constant light chain region (CL). A VH region and a VL region may be further divided into hypervariable regions (called complementarity-determining regions (CDRs)), which are interspaced by relatively conservative regions (called structural regions (FRW)). A VH and a VL may comprise 3 CDRs (complementarity-determining regions) and 4 FRs (structural regions) in the following order: FRW1, CDR1, FRW2, CDR2, FRW3, CDR3, FRW4 from the N end to the C end. Antibodies may be of different antibody isotypes, for example, IgG antibody (e.g., subtype IgG1, IgG2, IgG3 or IgG4), IgA1, IgA2, IgD, IgE or IgM.

[0053] A universal numbering system for hypervariable regions has been developed and widely adopted, the ImMunoGeneTics (IMGT®) Information System (Lefranc et al., Dev. Comp. Immunol. 27(1): 55-77 (2003)). IMGT® is an integrated information system specialized in immunoglobulins (IG), T-cell receptors (TR), and major histocompatibility complex (MHC) of humans and other vertebrates. Here, CDRs are referred to in terms of amino acid sequence and location within the light or heavy chain. Because the “location” of CDRs within the immunoglobulin variable region structure is conserved across species and is present in structures called loops, using numbering systems that align sequences of variable regions of structural features, CDRs, and structural residues are easily identified.This information can be used in the grafting and replacement of CDR residues of immunoglobulins from one species into an acceptor structure, typically a human antibody. An additional numbering system (AHon) was developed by Honegger and Plückthun, J. Mol. Biol. 309: 657-670 (2001). The correspondence between the numbering system, including, for example, Kabat numbering, and the unique numbering system. Petition 870250084316, dated 09 / 18 / 2025, page 225 / 503 30 / 203 IMGT® is well known to those skilled in the art (see, for example, Kabat, supra; Chothia and Lesk, supra; Martin, supra; Lefranc et al., supra) and is also illustrated below. Several systems known in the art or described herein represent different ways of delineating CDRs and, when used to define the same antibody, are often considered equivalent. An exemplary system, shown in this document, combines Kabat and Chothia. Exemplificative IMGT® Kabat AbM Chethia Contact CDR1 of Vh 26-35 27-38 31-35 26-35 26-32 30-35 CDR2 of Vh 50-65 56-65 50-65 50-58 53-55 50-65 CDR-47-h of Vh 26-35 26-35 105- 117 95-102 95-102 96-101 93-101 CDR1 of Vl 24-34 27-38 24-34 24-34 26-32 30-36 CDR2 of Vl 50-56 56-65 50-50-56 50-56 46-55 CDR3 of Vl 89-97 105- 117 89-97 89-97 91-96 89-96

[0054] The term Fc region is used in this document to define the C-terminal region of an immunoglobulin heavy chain, including, for example, native sequence Fc regions, recombinant Fc regions, and variant Fc regions. Although the boundaries of the Fc region of an immunoglobulin heavy chain may vary, the Fc region of human IgG heavy chain is usually defined to extend from an amino acid residue at the Cys226 position (according to the EU numbering system), or from Pro230 (according to the EU numbering system), to the carboxyl terminus of the same. The C-terminal lysine (residue 447 according to the system) Petition 870250084316, dated 09 / 18 / 2025, page 226 / 503 The Fc region (as per EU numbering 31 / 203) can be removed, for example, during antibody production or purification, or by recombinant manipulation of the nucleic acid encoding an antibody heavy chain.

[0055] A “functional Fc region” possesses an “effector function” of a native sequence Fc region. Exemplary “effector functions” include C1q binding; complement-dependent cytotoxicity (CDC); Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; downregulation of cell surface receptors (e.g., B cell receptor; BCR), etc. In general, such effector functions require the Fc region to be combined with a binding region or binding domain (e.g., an antibody variable region or domain, including a VHH domain) and can be assessed using various assays as disclosed.

[0056] A “native sequence Fc region” comprises an amino acid sequence identical to the amino acid sequence of an Fc region found in nature and not manipulated, modified and / or altered (e.g., isolated, purified, selected, including or combined with other sequences, such as variable region sequences) by a human being. Human native sequence Fc regions include a native sequence human IgG1 Fc region (non-A and A allotypes); native sequence human IgG2 Fc region; native sequence human IgG3 Fc region; and native sequence human IgG4 Fc region, as well as their naturally occurring variants.

[0057] A “variant Fc region” comprises an amino acid sequence different from the sequence of a native sequence Fc region due to at least one amino acid modification (e.g., substitution, addition, or deletion), preferably one or more amino acid substitutions. In some embodiments, the variant Fc region has at least one amino acid substitution compared to a native sequence Fc region or the Fc region of a parental polypeptide, for example, from about one to about Petition 870250084316, dated 09 / 18 / 2025, page 227 / 503 32 / 203 ten amino acid substitutions, and preferably from about one to about five amino acid substitutions in a native sequence Fc region or in the Fc region of the parent polypeptide. A variant Fc region, as described herein, may have at least about 80% homology with a native sequence Fc region and / or with an Fc region of a parent polypeptide, or at least about 90% homology with the same, for example, at least about 95% homology with the same. The variant Fc region described herein may have a loss of effector function (e.g., Fc silent).

[0058] The DLL3 antibodies described herein include, but are not limited to, synthetic antibodies, monoclonal antibodies, recombinantly produced antibodies, multispecific antibodies (e.g., including bispecific antibodies), human antibodies, humanized antibodies, chimeric antibodies, intrabody antibodies, single-chain Fvs (scFv) (e.g., including monospecific, bispecific, etc.), camelized antibodies, Fab fragments, F(ab') fragments, disulfide-linked Fvs (sdFv), anti-idiotypic antibodies (anti-Id), and epitope-binding fragments of any of the above.

[0059] The term single variable domain of immunoglobulin or single variable domain or VHH domain or VHH or variable domain of heavy chain antibodies may be used interchangeably in this document and refers to a single-chain antigen-binding domain capable of binding to an antigen or epitope independently of a different variable domain. A VHH domain (e.g., variable domain of a heavy chain antibody) represents the smallest known antigen-binding unit generated by adaptive immune responses (Koch-Nolte F. et al., FASEB J. Nov; 21(13):3490-8. Electronic publication, June 15, 2007 (2007)). A VHH domain may be a human domain, but also includes a single domain from other species, such as rodent, nurse shark, and camelid VHH domains. Camelid VHHs are polypeptide domains Petition 870250084316, dated 09 / 18 / 2025, page 228 / 503 33 / 203 single-domain immunoglobulin derivatives from species including camel, llama, alpaca, dromedary, and guanaco, which produce heavy-chain antibodies naturally devoid of light chains. Such VHH domains can be humanized according to standard techniques available in the art and are considered as “single-domain antibodies”. As used in this document, VHH includes camelid VHH domains and humanized VHH domains.

[0060] The term “humanized antibody” refers to antibodies in which germline-derived CDR sequences from other mammalian species, such as a mouse, llama, or alpaca, have been grafted onto human structural sequences. Further structural region modifications may be made within the human structural sequences.

[0061] The term “Ka”, as used herein, refers to the association rate of a given antibody-antigen interaction, and the term “Kd”, as used herein, refers to the dissociation rate of a given antibody-antigen interaction. Kd values ​​for antibodies can be determined using well-established methods in the art. The term Kd, as used herein, refers to the dissociation constant of a given antibody-antigen interaction obtained from the ratio between Kd and Ka (e.g., Kd / Ka) and is expressed as a molar concentration (M). A preferred method for determining the Kd of an antibody is to use surface plasmon resonance, preferably with the use of a biosensor system, such as a Biacore® system.

[0062] The term specific binding or binds specifically, as used in this document, refers to a non-random binding reaction between two molecules, such as, for example, between an antibody and an antigen.

[0063] The term high affinity, as used in this document, refers to a DLL3 that has a Kd equal to or less than 1 x 10-7M, preferably equal to or less than 5 x 10-8M, preferably equal to or less than Petition 870250084316, dated 09 / 18 / 2025, p. 229 / 503 34 / 203 that 1 x 10-8M, preferably equal to or less than 5 x 10-9M and, even more preferably, equal to or less than 1 x 10-9M for a target antigen.

[0064] The term epitope, as used in this document, refers to a portion of an antigen to which an immunoglobulin or antibody binds specifically. “Epitope” is also known as an antigenic determinant. The epitope or antigenic determinant generally comprises chemically active surface groups of a molecule, such as amino acids, carbohydrates, or sugar side chains, and generally possesses a specific three-dimensional structure and a specific charge characteristic. For example, an epitope generally comprises at least 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 consecutive or non-consecutive amino acids in a unique steric conformation, which may be linear or conformational. See, for example, Epitope Mapping Protocols in Methods in Molecular Biology, Volume 66, GE Morris, Edition (1996).In a linear epitope, all interaction sites between a protein and an interacting molecule (e.g., an antibody) are linearly present along the primary amino acid sequence of the protein. In a conformational epitope, the interaction sites span amino acid residues that are separated from each other within a protein. Antibodies can be screened based on their competitiveness for binding to the same epitope using conventional techniques known to a person skilled in the art. For example, studies on competition or cross-competition can be conducted to obtain antibodies that compete or cross-compete with each other for binding to antigens. High-throughput methods for obtaining antibodies that bind to the same epitope, which are based on their cross-competition, are described in international patent application WO 03 / 48731.

[0065] The term isolated antibody, as used in this document, refers to an antibody that is substantially free of other antibodies with different antigenic specificities (for example, an isolated antibody that specifically binds to a DLL3 protein is Petition 870250084316, dated 09 / 18 / 2025, pp. 230 / 503 35 / 203 substantially free of antibodies that bind specifically to antigens with the exception of DLL3 proteins). An isolated antibody that binds specifically to a human DLL3 protein may, however, have cross-reactivity with other antigens, such as DLL3 proteins from other species. In addition, an isolated antibody may be substantially free of other cellular material and / or chemicals.

[0066] Examples of DLL3 antibodies for use in the DLL3-ADCs described herein include, but are not limited to, chimeric antibodies, humanized antibodies, human antibodies, and single-domain antibodies. In some embodiments, a DLL3-ADC as disclosed herein comprises a DLL3 antibody comprising at least one VHH that specifically binds to DLL3. Furthermore, a DLL3 antibody may be a single-domain antibody comprising a VHH. For example, a single-domain antibody has the ability to selectively bind to a specific antigen (e.g., DLL3). In some embodiments, a DLL3-ADC disclosed herein comprises a DLL3 antibody containing a VHH fused to an immunoglobulin Fc region, for example, an IgG Fc region (e.g., IgG4 or IgG1). In some embodiments, the Fc region is a human IgG1 Fc region. By fusing a VHH to an Fc region, it may be more efficient to recruit effector functions.Furthermore, the fusion of a VHH to an Fc region can help a DLL3 antibody form a dimer and can also aid in extending the half-life of DLL3-ADC in vivo. In some embodiments, a DLL3 antibody for use in DLL3-ADC, as disclosed herein, comprises two VHHs and an immunoglobulin Fc region, wherein each of the VHHs is directly or indirectly conjugated to an Fc chain. See, for example, Figure 1A. In some embodiments, the VHH is conjugated directly or indirectly to the N-terminal of the Fc.

[0067] In some embodiments, a DLL3 antibody of a DLL3-ADC, as disclosed herein, is a VHH-Fc fusion protein. As used herein, a VHH-Fc fusion refers to one or more VHH conjugates directly or Petition 870250084316, dated 09 / 18 / 2025, page 231 / 503 36 / 203 indirectly to an Fc. In other embodiments, VHH is conjugated directly or indirectly to the N-terminal of Fc. In some embodiments, a VHH-Fc fusion comprises two VHHs and an immunoglobulin Fc region, wherein each of the VHHs is directly or indirectly conjugated to an Fc chain. In some embodiments, each VHH is conjugated directly or indirectly to the N-terminal of the Fc chain. See, for example, Figure 1A. Additionally or alternatively, a VHH-Fc fusion comprises two chains, wherein each of the two chains comprises, from the N-terminal to the C-terminal, a VHH, a hinge region, a CH2, and a CH3. In other embodiments, one or more ligands may be present between any two of the VHHs, the hinge region, the CH2, and the CH3. In some embodiments, the two chains of the VHH-Fc fusion are identical to each other. In other forms, the two chains of the VHH-Fc fusion are different from each other.For example, the first chain of the VHH-Fc fusion comprises a first VHH that is different from the VHH of the second chain. Furthermore, or alternatively, the CH3 domains of the two chains are modified to facilitate the production of the VHH-Fc fusion, such as by introducing knob-into-hole mutations. As would be understood by a specialist in the field, in some embodiments, a chain of a VHH-Fc fusion may not comprise a CH1 between the VHH and the hinge region and is therefore different from a conventionally defined heavy chain of an antibody. However, when describing a DLL3-ADC or its embodiments, and where appropriate, the term "heavy chain," as used herein, may also be interpreted as referring to a chain of a VHH-Fc fusion protein.

[0068] As is known in the art, Camelidae antibody-derived VHH molecules are among the smallest known intact antigen-binding domains (approximately 15 kDa, or 10 times smaller than a conventional IgG) and are therefore well suited for delivery into dense tissues and for accessing the limited space between macromolecules.

[0069] VHHs as disclosed herein may be produced by a person skilled in the art in accordance with known methods. Petition 870250084316, dated 09 / 18 / 2025, page 232 / 503 37 / 203 in the art or any future method. For example, VHHs can be obtained using methods known in the art, such as immunizing a camel and obtaining hybridomas from it, or cloning a library of VHHs from the dissemination using molecular biology techniques known in the art and subsequent selection using phage display.

[0070] For example, a VHH can be obtained by immunizing llamas or alpacas with the desired antigen and subsequently isolating the mRNA encoding single-domain heavy chain antibodies. Through reverse transcription and polymerase chain reaction, a genetic library of single-domain antibodies containing several million clones is produced. Screening techniques such as phage display and ribosome display help identify the clones that bind to the antigen. One technique is phage display, in which an antibody library (e.g., from humans) is synthesized into phages, the library is screened with the antigen of interest or an antibody-binding portion thereof, and the antigen-binding phage is isolated, from which immunoreactive fragments can be obtained.Methods for preparing and screening libraries are well known in the art, and kits for generating phage display libraries are commercially available (e.g., the Pharmacia Recombinant Phage Antibody System, catalog number 27-9400-01; and the Stratagene SurfZAP™ phage display kit, catalog number 240612). There are also other methods and reagents that can be used in the generation and screening of antibody display libraries (see, for example, Barbas et al., Proc. Natl. Acad. Sci. USA 88:7978-7982 (1991)).

[0071] When potent clones are identified, their sequence is optimized, for example, by affinity maturation or humanization. Another objective is humanization to prevent immune reactions of the human body against the antibody.

[0072] Thus, VHHs can be obtained by (1) isolating the VHH domain from a naturally occurring heavy chain antibody; (2) expressing a nucleotide sequence that encodes a Petition 870250084316, dated 09 / 18 / 2025, pp. 233 / 503 38 / 203 naturally occurring VHH domain; (3) “humanization” (as described below) of a naturally occurring VHH domain or by expression of a nucleic acid encoding such a humanized VHH domain; (4) “camelization” of a naturally occurring VH domain of any animal species, in particular a mammalian species, such as a human, or by expression of a nucleic acid encoding such a camelized VH domain; (5) “camelization” of a “domain antibody” or “Dab”, as described by Ward et al (above), or by expression of a nucleic acid encoding such a camelized VH domain; (6) using synthetic or semi-synthetic techniques for the preparation of proteins, polypeptides or other amino acid sequences; (7) preparation of a nucleic acid encoding a VHH using nucleic acid synthesis techniques, followed by expression of the nucleic acid thus obtained;(8) subjecting heavy chain antibodies or HHVs to affinity maturation, mutagenesis (e.g., random mutagenesis or site-directed mutagenesis) and / or any other technique (or techniques) in order to increase the affinity and / or specificity of the HHV; and / or (9) by any combination of the foregoing. Appropriate methods and techniques for accomplishing the foregoing will become apparent to a person skilled in the art based on the disclosure in this document and include, for example, methods and techniques described in more detail herein.

[0073] Single-domain antibodies are generally generated by PCR cloning of variable-domain cDNA repertoire from blood, lymph node, or spleen obtained from immunized animals in a phage display vector. Antigen-specific single-domain antibodies are commonly screened by phase-scan libraries on immobilized antigen, for example, antigen coated on the plastic surface of a test tube, biotinylated antigens immobilized on streptavidin beads, or membrane proteins expressed on the cell surface. The affinity of sdAbs can often be enhanced by mimicking this strategy in vitro, for example, by site-directed mutagenesis of CDR regions and other screening rounds in Petition 870250084316, dated 09 / 18 / 2025, page 234 / 503 39 / 203 Immobilized antigen under more stringent conditions (higher temperature, high or low salt concentration, high or low pH and low antigen concentrations) (Wesolowski et al., Single-domain antibodies: promising experimental and therapeutic tools in infection and immunity. Med Microbiol Immunol (2009) 198: 157-174).

[0074] Methods for preparing a VHH that binds specifically to an antigen or epitope have been described in the references, for example: R. van der Linden et al., Journal of Immunological Methods, 240(2000) 185-195; Li et al., J Biol Chem., 287(2012)13713-13721; Deffar et al., African Journal of Biotechnology Vol. 8(12), pages 2645, June 17, 2009 and document no. WO 94 / 04678.

[0075] In some embodiments, a VHH may be truncated at the N-end or at the C-end, so that it comprises only a partial FRW1 and / or FRW4 or lacks one or both of these structural regions, provided that the VHH substantially maintains antigen binding and specificity (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%).

[0076] The DLL3 antibodies of the DLL3-ADCs described in this document may be monospecific, bispecific, trispecific, or of greater multispecificity. Such agents may include antibodies. Multispecific antibodies, such as bispecific antibodies, are monoclonal antibodies that possess binding specificities for at least two different targets (e.g., antigens) or two different epitopes on the same target (e.g., a bispecific antibody directed at DLL3 with a first binding domain for a first DLL3 epitope and a second binding domain for a second DLL3 epitope). In some embodiments, multispecific (e.g., bispecific) antibodies may be constructed based on the antibody sequences described in this document. In some embodiments, the multispecific antibodies described in this document Petition 870250084316, dated 09 / 18 / 2025, page 235 / 503 40 / 203 document are bispecific antibodies. In certain embodiments, bispecific antibodies are human or humanized antibodies. In some embodiments, one of the binding specificities of the multispecific antibody is for DLL3, and the other is for any other target (e.g., antigen). In some embodiments, a multispecific (e.g., bispecific) antibody may comprise more than one target-binding domain (e.g., antigen), where different binding domains are specific for different targets (e.g., a first binding domain that binds to DLL3 and a second binding domain that binds to another target (e.g., antigen), such as an immune checkpoint regulator (e.g., a negative checkpoint regulator).In some embodiments, multispecific (e.g., bispecific) antibody molecules can bind to more than one (e.g., two or more) epitopes on the same target (e.g., antigen). In some embodiments, one of the binding specificities is DLL3 and the other is for one or more of the following: cytotoxic T lymphocyte antigen 4 (CTLA-4), CD80, CD86, programmed cell death 1 (PD-1), programmed cell death ligand 1 (PD-L1), programmed cell death ligand 2 (PD-L2), lymphocyte activation gene-3 (LAG-3; also known as CD223), galectin-3, B and T lymphocyte attenuator (BTLA), T-cell membrane protein 3 (TIM3), galectin-9 (GAL9), B7-H1, B7-H3, B7-H4, T cell immunoreceptor with Ig and ITIM domains (TIGIT / Vstm3 / WUCAM / VSIG9), V-domain suppressor of T cell activation (VISTA), glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR), viral entry mediator. herpes (HVEM), OX40, CD27, CD28, CD137.CGEN-15001T, CGEN15022, CGEN-15027, CGEN-15049, CGEN-15052 and CGEN-15092.

[0077] Methods for producing multispecific antibodies are known in the art, for example, by the co-expression of two immunoglobulin heavy-light chain pairs, where the two heavy chains have different specificities (see, for example, Milstein and Cuello, 1983, Nature 305:537-40). In order to obtain more details on antibody generation Petition 870250084316, dated 09 / 18 / 2025, p. 236 / 503 41 / 203 multispecific (e.g., bispecific antibodies), see, for example, Bispecific Antibodies (Kontermann ed., 2011).

[0078] This disclosure provides humanized antibodies that bind to DLL3. Several methods for humanizing non-human antibodies are known in the art. For example, a humanized antibody may have one or more amino acid residues introduced from a non-human source. These non-human amino acid residues are often referred to as “import” residues, which are typically taken from a variable “import” domain. Humanized antibodies that bind to DLL3 can be produced using techniques known to those skilled in the art (e.g., Zhang et al., Molecular Immunology, 42(12): 1445-1451, 2005; Hwang et al., Methods, 36(1): 35-42, 2005; Dall'Acqua et al., Methods, 36(1): 4360, 2005; Clark, Immunology Today, 21(8): 397-402, 2000, and US Patents Nos. 6,180,370; 6,054,927; 5,869,619; 5,861,155; 5,712,120 and 4,816,567).

[0079] The term identity, as used in this document, refers to a relationship between the sequences of two or more polypeptide molecules or two or more nucleic acid molecules, as determined by the alignment and comparison of the sequences. “Percentage of identity” means the percentage of identical residues between amino acids or nucleotides in the compared molecules and is calculated based on the size of the smallest of the molecules being compared. For these calculations, gaps in the alignments (if any) are preferably addressed by a specific mathematical model or computer program (e.g., an “algorithm”). Methods that can be used to calculate the identity of aligned nucleic acids or polypeptides include those described in Computational Molecular Biology, (Lesk, AM, ed.), 1988, New York: Oxford University Press; Biocomputing Informatics and Genome Projects, (Smith, DW, ed.), 1993, New York: Academic Press; Computer Analysis of Sequence Data, Part I, (Griffin, AM, and Griffin, HG, eds.), 1994, New Jersey: Humana Press; von Heinje, G., 1987, Sequence Analysis in Molecular Biology, New York:. Petition 870250084316, dated 09 / 18 / 2025, p. 237 / 503 42 / 203 Academic Press; Sequence Analysis Primer, (Gribskov, M. and Devereux, J., eds.), 1991, New York: M. Stockton Press; and Carillo et al., 1988 SIAMJ. Applied Math. 48:1073. Alignment methods are available for a specialist in the field, such as BLAST, as disclosed here, and / or Clustal Omega.

[0080] Polynucleotide or nucleic acid, as used interchangeably herein, refers to polymers of nucleotides of any length and includes DNA and RNA. Nucleotides may be deoxyribonucleotides, ribonucleotides, modified nucleotides or bases, and / or their analogues or any substrate that can be incorporated into a polymer by DNA or RNA polymerase or by a synthetic reaction. A polynucleotide may comprise modified nucleotides, such as methylated nucleotides and their analogues. A cell producing a binding molecule of the present disclosure may include a parental hybridoma cell as well as bacterial and eukaryotic host cells into which nucleic acids encoding antibodies have been introduced.Unless otherwise specified, the left end of any single-stranded polynucleotide sequence disclosed in this document is the 5' end; the leftward direction of double-stranded polynucleotide sequences is referred to as the 5' direction. The direction of addition from 5' to 3' of nascent RNA transcripts is referred to as the direction of transcription; sequence regions in the DNA strand having the same sequence as the RNA transcript that are 5' to the 5' end of the RNA transcript are referred to as upstream sequences; sequence regions in the DNA strand with the same sequence as the RNA transcript that are 3' to the 3' end of the RNA transcript are referred to as downstream sequences.

[0081] The term vector, as used in this document, refers to a nucleic acid carrier that may have a polynucleotide inserted into it. When the vector allows the expression of the protein encoded by the inserted polynucleotide, the vector is called an expression vector. The vector may carry elements of genetic material expressed in a host cell by Petition 870250084316, dated 09 / 18 / 2025, page 238 / 503 43 / 203 transformation, transduction, or transfection in the host cell. Vectors are well known to a person skilled in the art, including, but not limited to, plasmids, phages, cosmids, artificial chromosomes such as yeast artificial chromosome (YAC), bacterial artificial chromosome (BAC), or P1-derived artificial chromosome (PAC); phages such as phage λ or phage M13; and animal viruses. Animal viruses that can be used as vectors include, but are not limited to, retroviruses (including lentiviruses), adenoviruses, adeno-associated viruses, herpes viruses (such as herpes simplex virus), poxviruses, baculoviruses, papillomaviruses, papova viruses (such as SV40). A vector may comprise multiple elements to control expression, including, but not limited to, a promoter sequence, a transcription initiation sequence, an enhancer sequence, a selection element, and a reporter gene. In addition, a vector may comprise an origin of replication.

[0082] The term host cell, as used in this document, refers to a cell into which a vector can be introduced, including, but not limited to, a prokaryotic cell such as E. coli or Bacillus subtilis, a fungal cell such as a yeast or Aspergillus cell, an insect cell such as Drosophila S2 or Sf9 cells, and an animal cell such as a fibroblast, CHO cell, COS cell, NSO cell, HeLa cell, BHK cell, HEK 293 cell or human cell.

[0083] The term transfection or transfection, as used herein, refers to a process by which nucleic acids are introduced into eukaryotic cells, particularly mammalian cells. Protocols and techniques for transfection include, but are not limited to, lipid transfection and chemical and physical methods such as electroporation. Several transfection techniques are well known in the art and are disclosed in this document. See, for example, Graham et al., 1973, Virology 52:456; Sambrook et al., 2001, Molecular Cloning: A Laboratory Manual, supra; Davis et al., 1986, Basic Methods in Molecular Biology, Elsevier; Chu et al., 1981, Gene 13:197. Petition 870250084316, dated 09 / 18 / 2025, p. 239 / 503 44 / 203

[0084] The DLL3-ADCs disclosed herein comprise a DLL3 antibody. “DLL3 antibodies” includes, but is not limited to, a chimeric antibody, a humanized antibody, a human antibody, or a single-domain antibody.

[0085] Disclosure DLL3 antibodies, including, for example, antibodies comprising at least one VHH domain, are characterized by specific antibody functional features or properties. In some embodiments, the antibodies have one or more of the following properties: (a) bind to human DLL3, cyno DLL3 and mouse DLL3 with EC50 in nM scale, as measured by ELISA or FACS; (b) exhibit dose-dependent internalization potency in human cells engineered to express DLL3; and (c) bind to a human DLL3 extracellular domain (ECD) with a Kd of at most 0.1 nM, as measured by SPR.

[0086] A DLL3-ADC disclosed herein comprises a DLL3 antibody that binds to the cell surface DLL3 with high affinity. The binding of an antibody, and therefore of the DLL3-ADC of which the antibody is a part, can be assessed using one or more well-established techniques in the art, for example, ELISA. The binding specificity of a DLL3-ADC can also be determined by monitoring the binding of the DLL3-ADC to cells expressing a DLL3 protein, for example, by flow cytometry. For example, an antibody can be tested by a flow cytometry assay (e.g., FACS) in which the DLL3-ADC reacts with a cell line expressing human DLL3, such as CHO cells and 293 cells that have been transfected to express DLL3 on their cell surfaces. Additionally or alternatively, the binding of the DLL3-ADC, including the binding kinetics (e.g., Kd value), can be tested in BIAcore binding assays.Other suitable binding assays include ELISA assays, for example, using a recombinant DLL3 protein. For instance, a DLL3-ADC disclosed in this document can bind to a cell surface DLL3 protein (e.g. Petition 870250084316, dated 09 / 18 / 2025, pp. 240 / 503 45 / 203 example, DLL3 ECD human) with a Kd of 1 x 10-7M or less, 5 x 10-8M or less, 2 x 10-8M or less, 5 x 10-9M or less, 4 x 10-9M or less, 3 x 10-9M or less, 2 x 10-9M or less, 1 x 10-9M or less, 5 x 10-10M or less or 1 x 10-10M or less.

[0087] The term “fluorescence-activated cell sorting” or “FACS,” as used in this document, refers to a specialized type of flow cytometry. The term provides a method for sorting a heterogeneous mixture of biological cells into two or more containers, one cell at a time, based on the specific light scattering and fluorescent characteristics of each cell (FlowMetric. “Fluorescence-Activated Flow Cytometry Sorting.” Retrieved 2017-11-09). Instruments for performing FACS are known to those skilled in the art and are commercially available to the public. Examples of such instruments include the FACS Star Plus, FACScan, and FACSort instruments from Becton Dickinson (Foster City, California), the Epics C from Coulter Epics Division (Hialeah, Florida), and the MoFlo from Cytomation (Colorado Springs, Colorado).

[0088] The term SPR or surface plasmon resonance, as used in this document, refers to and includes an optical phenomenon that allows for real-time analysis of biospecific interactions through the detection of changes in protein concentrations within a biosensor array, for example, with the use of the BIAcore System (Pharmacia Biosensor AB, Uppsala, Sweden and Piscataway, NJ). For more detailed descriptions, see Jonsson, U., et al. (1993) Ann. Biol. Clin. 51:19-26; Jonsson, U., et al. (1991) Biotechniques 11:620-627; Johnsson, B., et al. (1995) J. Mol. Recognit. 8:125-131; and Johnsson, B., et al. (1991) Anal. Biochem. 198:268-277.

[0089] The term “EC50”, as used in this document, is also referred to as “half the maximum effective concentration”, and refers to the concentration of a drug, antibody or toxicant that induces a response the furthest from baseline to maximum after a given exposure time. Petition 870250084316, dated 09 / 18 / 2025, pp. 241 / 503 46 / 203 specified. In the context of this disclosure, EC50 is expressed in nM. In some embodiments, the disclosure antibodies bind to cynomolgus monkey or DLL3 mouse at an EC50 not exceeding or about 10 nM, 9 nM, 8 nM, 7 nM, 6 nM, 5 nM, 4 nM, 3 nM, 2 nM, 1 nM, 0.9 nM, 0.8 nM, 0.7 nM, 0.6 nM, 0.5 nM, 0.4 nM, 0.3 nM, 0.2 nM, 0.1 nM, 0.09 nM, 0.08 nM, 0.07 nM, 0.06 nM, 0.05 nM, 0.04 nM, 0.03 nM, 0.02 nM, or 0.01 nM, as measured by FACS. DLL3 antibodies comprising VHH CDRs

[0090] In some embodiments, a DLL3-ADC, as disclosed herein, comprises a DLL3 antibody comprising a variable heavy chain domain (VH, such as a VHH), wherein the VH comprises CDR1, CDR2, and CDR3, such as a VHH or a VHH conjugated to an Fc. In other embodiments, CDR1 comprises an amino acid sequence as set forth in SEQ ID NO:1 or 7, CDR2 comprises an amino acid sequence as set forth in SEQ ID NO:2 or 8, and CDR3 comprises an amino acid sequence as set forth in SEQ ID NO:3 or 9. In some embodiments, the numbering of the CDRs follows a combination of Kabat and AbM numbering. The extent of the structural region and CDRs can be accurately identified using methodologies known in the art, for example, the Kabat definition, the Chothia definition, the AbM definition, the contact definition, the IMGT definition (all of which are well known in the art), and any combination thereof.See, for example, Kabat, EA, et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, US Department of Health and Human Services, NIH Publication No. 91-3242, Chothia et al., (1989) Nature 342:877; Chothia, C. et al. (1987) J. Mol. Biol. 196:901-917, Al-lazikani et al (1997) J. Molec. Biol. 273:927-948; Edelman et al., Proc Natl Acad Sci US A. 1969 May, 63(1):78-85; and Martin and Allen, in “Handbook of Therapeutic Antibodies”, chapter 5, 2007. See also hgmp.mrc.ac.uk and bioinf.org.uk / abs. Correspondence or alignment between numbering according to different definitions may occur. Petition 870250084316, dated 09 / 18 / 2025, pp. 242 / 503 47 / 203 can be found, for example, at www.imgt.org / (see also Giudicelli V et al. IMGT, the international database ImMunoGeneTics. Nucleic Acids Res. (1997) 25:206-11; and Lefranc MP et al., the unique IMGT numbering for immunoglobulin variable domains and T-cell receptor and Ig superfamily V-type domains. Dev Comp Immunol. (2003) 27:55-77).

[0091] As will be observed by those skilled in the art, the exact numbering and placement of the CDRs may differ between different numbering systems. However, it should be understood that the disclosure of a variable heavy sequence, a variable light sequence, and / or a VHH sequence includes the disclosure of the associated (inherent) CDRs. Thus, the disclosure of each variable region is a disclosure of the CDRs (e.g., CDR1, CDR2, and CDR3). Two antibodies that have the same VH, VL, or VHH CDRs mean that their CDRs are identical when determined by the same approach (e.g., the Kabat, AbM, Chothia, Contact, and IMGT numbering approaches, as known in the art).

[0092] Variable regions and CDRs in an antibody sequence can be identified according to general rules that have been developed in the technique (e.g., the Kabat, AbM, Chothia, Contact, and IMGT numbering systems) or by aligning the sequences by comparing them to a database of variable regions. Methods for identifying these regions are described in Kontermann and Dubel, eds., Antibody Engineering, Springer, New York, NY, 2001 and Dinarello et al., Current Protocols in Immunology, John Wiley and Sons Inc., Hoboken, NJ, 2000. Exemplary antibody sequence databases are described and can be consulted via the Abysis website at www.bioinf.org.uk / abs (maintained by AC Martin in the Department of Biochemistry & Molecular Biology, University College London, London, England) and the VBASE2 website at www.vbase2.org, as described in Retter et al., Nucl. Acids Res., 33 (Database issue): D671-D674 (2005).Preferably, the sequences are analyzed using the Abysis database, which integrates Kabat sequence data, IMGT data, and the Database of... Petition 870250084316, dated 09 / 18 / 2025, pp. 243 / 503 48 / 203 Protein (PDB) with PDB structural data. See chapter of the book by Dr. Andrew CR Martin, Protein Sequence and Structure Analysis of Antibody Variable Domains. In: Antibody Engineering Lab Manual (Ed.: Duebel, S. and Kontermann, R., Springer-Verlag, Heidelberg, ISBN-13: 978-3540413547, also available at bioinforg.uk / abs). The Abysis database website additionally includes general rules that have been developed for identifying CDRs that can be used in accordance with the teachings contained in this document. Unless otherwise indicated, all CDRs presented here are derived according to the Abysis database website as per Kabat, except for CDRs from Chothia (see, for example, Chothia & Lesk (1987) J. Mol. Biol. 196:901-917).

[0093] In some embodiments, the DLL3 antibody (such as a VHH or a VHH conjugated to an Fc, for example, a VHH-Fc fusion) comprises at least one VH comprising one, two and / or three heavy chain CDRs, as described in Table 1 or Table 2. Petition 870250084316, dated 09 / 18 / 2025, pp. 244 / 503 49 / 203

[0094] Table 1: mAb300 and mAb301 antibodies Exemplificativo IMGT Kabat Chothia Contact AbM Seq. da CDR of VHH CDR1 of VHH GLTFSTATVG (SEQ ID NO: 1) GLTFSTAT (SEQ ID NO:20) TATVG (SEQ ID NO:23) GLTFSTA (SEQ ID NO:24) STATVG (SEQ ID NO:27) GLTFSTATVG (SEQ ID NO: 1) CDR2 of VHH AIPAYYSTYYAS SVKG (SEQ ID NO: 2) IPAYYST (SEQ ID NO:21) AIPAYYSTYYA SSVKG (SEQ ID NO: 2) AYY (SEQ ID NO:25) LIAAIPAYYSTY (SEQ ID NO:28); NO:3) AADDTPSPSR SPFYKH (SEQ ID NO:22) DDTPSPSRSPF YKH (SEQ ID NO:3) DTPSPSRSP FYK (SEQ ID NO:26) AADDTPSPSRS PFYK (SEQ ID NO:29) DDTPSPSRSPF YKH (SEQ ID NO:3) Sequência VHH mAb300 EVQLVESGGGLVQPGGSLRLSCAASGLTFSTATVGWFRQAPGKGRELIAAIPAYYSTYYASSVKGRFTISRDNAKNSLYLQMNSLRPED TAVYYCAADDTPSPSRSPFYKHRGQGTMVTVSS (SEQ ID NO: 14) Fusão VHH-Fc Sequência VHH mAb300 Petition: 870250084316, on September 18, 2025, page. 245 / 503 50 / 203 EVQLVESGGGLVQPGGSLRLSCAASGLTFSTATVGWFRQAPGKGRELIAAIPAYYSTYYASSVKGRFTISRDNAKNSLYLQMNSLRPED TAVYYCAADDTPSPSRSPFYKHRGQGTMVTVSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKF NWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK (SEQ ID NO: 4) Sequência VHH mAb301 EVQLVESGGGLVQPGGSLRLSCAASGLTFSTATVGWFRQAPGKGRELVAAIPAYYSTYYASSVKGRFTISRDNAKNSLYLQMNSLRPE DTAVYYCAADDTPSPSRSPFYKHRGQGTMVTVSS (SEQ ID NO:15) Fusão VHH-Fc Sequência VHH mAb301 EVQLVESGGGLVQPGGSLRLSCAASGLTFSTATVGWFRQAPGKGRELVAAIPAYYSTYYASSVKGRFTISRDNAKNSLYLQMNSLRPE DTAVYYCAADDTPSPSRSPFYKHRGQGTMVTVSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVK FNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQ VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK (SEQ ID NO:5)

[0095] Tabela 2: Anticorpo mAb302 Petition: 870250084316, on September 18, 2025, page. 246 / 503 51 / 203 Exemplificative IMGT Kabat Chethia Contact AbM Seq. da CDR of VHH CDR1 of VHH GRTFRSYAMG (SEQ ID NO:7) GRTFRSYA (SEQ ID NO:42) SYAMG (SEQ ID NO:45) GRTFRSY (SEQ ID NO:46) RSYAMG (SEQ ID NO: 49) GRTFRSYAM G (SEQ ID NO:7) CDR2 of VHH AISWIGGGTYY ADSVKG (SEQ ID NO:8) ISWIGGGT (SEQ ID NO:43) AISWIGGGTY YADSVKG (SEQ ID NO:8) WIGG (SEQ ID NO:47) FVAAISWIGG GTY (SEQ ID NO:50) AISWIGGGTY (SEQ ID NO:52) CDR3 of VHH SSLLRHGHMF EESDY (SEQ ID NO:9) AASSLLRHG HMFEESDY (SEQ ID NO:44) SSLLRHGHM FEESDY (SEQ ID NO:9) SLLRHGHMF EESD (SEQ ID NO:48) AASSLLRHG HMFEESD (SEQ ID NO:51) SSLLRHGHM FEESDY (SEQ ID NO:9) Sequência VHH mAb302 QVQLVESGGGVVQPGGSLRLSCAASGRTFRSYAMGWFRQAPGKEREFVAAISWIGGGTYYADSVKGRFTISGDNSKNTL YLQMNSLRAEDTAVYYCAASSLLRHGHMFEESDYWGQGTMVTVSS (SEQ ID NO: 16) Petition: 870250084316, on September 18, 2025, page. 247 / 503 52 / 203 VHH-Fc Fusion Sequence VHH mAb302 QVQLVESGGGVVQPGGSLRLSCAASGRTFRSYAMGWFRQAPGKEREFVAAISWIGGGTYYADSVKGRFTISGDNSKNTL YLQMNSLRAEDTAVYYCAASSLLRHGHMFEESDYWGQGTMVTVSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISR TPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTI SKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK (SEQ ID NO:10) Petition 870250084316, dated 09 / 18 / 2025, pp. 248 / 503 53 / 203

[0096] In some embodiments, a DLL3-ADC disclosed in this document comprises a DLL3 antibody containing a variable heavy chain (VH) domain, such as a VHH or an Fc-conjugated VHH, wherein the VH comprises FRW1-CDR1-FRW2-CDR2-FRW3-CDR3-FRW4, and wherein CDR1 comprises an amino acid sequence as set forth in SEQ ID NO:1 or 7, CDR2 comprises an amino acid sequence as set forth in SEQ ID NO:2 or 8, and CDR3 comprises an amino acid sequence as set forth in SEQ ID NO:3 or 9. In some embodiments, the FRW1 and FRW4 at the N- and C-terminal ends of the VHH comprised in a DLL3 antibody may be truncated so that they comprise only a partial FRW1 and / or FRW4, or the VHH may lack one or both of these structural regions, provided that the VHH substantially maintains antigen binding and specificity.

[0097] In some embodiments, a DLL3-ADC disclosed in this document comprises a DLL3 antibody (such as an anti-DLL3 single-domain antibody, a VHH, or an Fc-conjugated VHH) containing one, two, or all three CDRs of the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, a DLL3-ADC comprises a DLL3 antibody (such as an anti-DLL3 single-domain antibody, a VHH, or an Fc-conjugated VHH) that includes one, two, or all three CDRs of the amino acid sequence as set forth in SEQ ID NO:15. In some embodiments, a DLL3-ADC comprises a DLL3 antibody (such as an anti-DLL3 single-domain antibody, a VHH, or an Fc-conjugated VHH) that includes one, two, or all three CDRs of the amino acid sequence as set forth in SEQ ID NO:16. In some embodiments, a DLL3ADC, as disclosed herein, comprises a DLL3 antibody that comprises a camelid VHH.In some embodiments, a DLL3-ADC, as disclosed herein, comprises a humanized DLL3 antibody. In some embodiments, a DLL3-ADC, as described herein, comprises a DLL3 antibody that comprises a human acceptor scaffold, for example. Petition 870250084316, dated 09 / 18 / 2025, pp. 249 / 503 54 / 203 a human immunoglobulin framework or a human consensus framework.

[0098] In some embodiments, a DLL3-ADC, as disclosed herein, comprises a DLL3 antibody comprising a CDR1 with an amino acid sequence of CDR1, as set forth in SEQ ID NO: 1. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a CDR2 with an amino acid sequence of CDR2, as set forth in SEQ ID NO: 2. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a CDR3 with an amino acid sequence of CDR3, as set forth in SEQ ID NO: 3. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a CDR1 and a CDR2 with amino acid sequences of CDR1 and CDR2, as set forth in SEQ ID NO: 1 and 2, respectively. In some embodiments, a DLL3-ADC comprises a DLL3 antibody containing a CDR1 and a CDR3, whose amino acid sequences are established in SEQ ID NO:1 and 3, respectively.In some embodiments, a DLL3-ADC comprises a DLL3 antibody that includes a CDR2 and a CDR3 with the amino acid sequences of CDR2 and CDR3 as set forth in SEQ ID NO:2 and 3, respectively. In some embodiments, a DLL3-ADC comprises a DLL3 antibody that includes a CDR1, a CDR2, and a CDR3 with the amino acid sequences of CDR1, CDR2, and CDR3 as set forth in SEQ ID NO:1, 2, and 3, respectively. In some embodiments, a DLL3-ADC comprises a DLL3 antibody (such as a single-domain anti-DLL3 antibody, a VHH, or an Fc-conjugated VHH) that includes one, two, or all three CDRs of the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, a DLL3-ADC comprises a DLL3 antibody (such as an anti-DLL3 single-domain antibody, a VHH, or an Fc-conjugated VHH) that includes one, two, or all three CDRs of the amino acid sequence as set forth in SEQ ID NO:15. The CDR sequences may be... Petition 870250084316, dated 09 / 18 / 2025, pp. 250 / 503 55 / 203 determined according to well-known numbering systems. In some embodiments, CDRs are in accordance with IMGT numbering. In some embodiments, CDRs are in accordance with Kabat numbering. In other embodiments, CDRs are in accordance with Chothia numbering. In other embodiments, CDRs are in accordance with Contato numbering. In some embodiments, CDRs are in accordance with AbM numbering. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a camelid VHH. In some embodiments, a DLL3-ADC comprises a humanized DLL3 antibody. In some embodiments, a DLL3-ADC comprises a DLL3 antibody that includes a human acceptor scaffold, for example, a human immunoglobulin scaffold or a human consensus scaffold.

[0099] In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a CDR1 with an amino acid sequence of CDR1, as set forth in SEQ ID NO: 7. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a CDR2 with an amino acid sequence of CDR2, as set forth in SEQ ID NO: 8. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a CDR3 with an amino acid sequence of CDR3, as set forth in SEQ ID NO: 9. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a CDR1 and a CDR2 with amino acid sequences of CDR1 and CDR2, as set forth in SEQ ID NO: 7 and 8, respectively. In some embodiments, a DLL3-ADC comprises a DLL3 antibody that includes a CDR1 and a CDR3 with the amino acid sequences of CDR1 and CDR3 as set forth in SEQ ID NO:7 and 9, respectively.In some embodiments, a DLL3-ADC comprises a DLL3 antibody that includes a CDR2 and a CDR3 with the amino acid sequences of CDR2 and CDR3 as set forth in SEQ ID NO:8 and 9, respectively. In some embodiments, a DLL3-ADC comprises a DLL3 antibody that includes a... Petition 870250084316, dated 09 / 18 / 2025, pp. 251 / 503 56 / 203 CDR1, CDR2, and CDR3 with the amino acid sequences of CDR1, CDR2, and CDR3 as set forth in SEQ IDs NO:7, 8, and 9, respectively. In some embodiments, a DLL3-ADC comprises a DLL3 antibody (such as a single-domain anti-DLL3 antibody, a VHH, or a VHH conjugated to an Fc) that includes one, two, or all three CDRs of the amino acid sequence as set forth in SEQ ID NO:16. The CDR sequences can be determined according to well-known numbering systems. In some embodiments, the CDRs conform to IMGT numbering. In some embodiments, the CDRs conform to Kabat numbering. In other embodiments, the CDRs conform to Chothia numbering. In other embodiments, the CDRs conform to Contato numbering. In some embodiments, the CDRs conform to AbM numbering. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a camelid VHH.In some embodiments, a DLL3-ADC comprises a humanized DLL3 antibody. In some embodiments, a DLL3-ADC comprises a DLL3 antibody that includes a human acceptor scaffold, for example, a human immunoglobulin scaffold or a human consensus scaffold.

[0100] In some embodiments, a DLL3ADC comprising a DLL3 antibody containing the following structure is provided in this document: FRW1CDR1-FRW2-CDR2-FRW3-CDR3-FRW4, wherein (i) CDR1 comprises an amino acid sequence as set forth in any of SEQ ID NO:1, SEQ ID NO:4, SEQ ID NO:20, SEQ ID NO:23, SEQ ID NO:24 or SEQ ID NO:27; (ii) CDR2 comprises an amino acid sequence as set forth in any of SEQ ID NO:2, SEQ ID NO:21, SEQ ID NO:25, SEQ ID NO:28, SEQ ID NO:56 or SEQ ID NO:30; and / or (iii) CDR3 comprises an amino acid sequence as set forth in any of SEQ ID NO:3, SEQ ID NO:22, SEQ ID NO:26 or SEQ ID NO:29. In some embodiments, a DLL3-ADC, as disclosed herein, comprises a DLL3 antibody that comprises a camelid VHH. In some Petition 870250084316, dated 09 / 18 / 2025, pp. 252 / 503 57 / 203 embodiments, a DLL3-ADC, as disclosed herein, comprises a humanized DLL3 antibody. In some embodiments, a DLL3-ADC, as described herein, comprises a DLL3 antibody that comprises a human acceptor scaffold, for example, a human immunoglobulin scaffold or a human consensus scaffold.

[0101] In some embodiments, the CDR1 of the DLL3 antibody of the DLL3ADC comprises the exemplary amino acid sequences as set forth in SEQ ID NO: 1; the CDR2 comprises the exemplary amino acid sequences as set forth in SEQ ID NO: 2; and the CDR3 comprises the exemplary amino acid sequences as set forth in SEQ ID NO: 3. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to the IMGT numbering that comprises the amino acid sequence as set forth in SEQ ID NO: 20; the CDR2 conforms to the IMGT numbering that comprises the amino acid sequence as set forth in SEQ ID NO: 21; and the CDR3 conforms to the IMGT numbering that comprises the amino acid sequence as set forth in SEQ ID NO: 22.In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to the Kabat numbering, which comprises the amino acid sequence as set forth in SEQ ID NO:23; the CDR2 conforms to the Kabat numbering, which comprises the amino acid sequence as set forth in SEQ ID NO:2; and the CDR3 conforms to the Kabat numbering, which comprises the amino acid sequence as set forth in SEQ ID NO:3. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to the Chothia numbering, which comprises the amino acid sequence as set forth in SEQ ID NO:24; the CDR2 conforms to the Chothia numbering, which comprises the amino acid sequence as set forth in SEQ ID NO:25; and the CDR3 conforms to the Chothia numbering, which comprises the amino acid sequence as set forth in SEQ ID NO:26. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to... Petition 870250084316, dated 09 / 18 / 2025, pp. 253 / 503 58 / 203 Contact numbering comprising the amino acid sequence as set forth in SEQ ID NO: 27; CDR2 conforms to Contact numbering comprising the amino acid sequence as set forth in SEQ ID NO: 28 or 56; and CDR3 conforms to Contact numbering comprising the amino acid sequence as set forth in SEQ ID NO: 29. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to AbM numbering, comprising the amino acid sequence set forth in SEQ ID NO:1; CDR2 conforms to AbM numbering, comprising the amino acid sequence set forth in SEQ ID NO:30; and CDR3 conforms to AbM numbering, comprising the amino acid sequence set forth in SEQ ID NO:3. In some embodiments, a DLL3-ADC as disclosed herein comprises a DLL3 antibody containing a camel VHH. In some embodiments, DLL3-ADC comprises a DLL3 antibody that is humanized.In some embodiments, a DLL3-ADC, as described herein, comprises a DLL3 antibody comprising a human acceptor scaffold, for example, a human immunoglobulin scaffold or a human consensus scaffold.

[0102] In some embodiments, the CDR1 of the DLL3 antibody of the DLL3ADC comprises the exemplary amino acid sequences as set forth in SEQ ID NO: 7; the CDR2 comprises the exemplary amino acid sequences as set forth in SEQ ID NO: 8; and the CDR3 comprises the exemplary amino acid sequences as set forth in SEQ ID NO: 9. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to the IMGT numbering which comprises the amino acid sequence as set forth in SEQ ID NO: 42; the CDR2 conforms to the IMGT numbering which comprises the amino acid sequence as set forth in SEQ ID NO: 43; and the CDR3 conforms to the IMGT numbering which comprises the amino acid sequence as set forth in SEQ ID NO: 44. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to the Kabat numbering, which comprises Petition 870250084316, dated 09 / 18 / 2025, pp. 254 / 503 59 / 203 the amino acid sequence as established in SEQ ID NO:45; CDR2 conforms to the Kabat numbering, which comprises the amino acid sequence as established in SEQ ID NO:8; and CDR3 conforms to the Kabat numbering, which comprises the amino acid sequence as established in SEQ ID NO:9. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to the Chothia numbering, which comprises the amino acid sequence as established in SEQ ID NO:46; CDR2 conforms to the Chothia numbering, which comprises the amino acid sequence as established in SEQ ID NO:47; and CDR3 conforms to the Chothia numbering, which comprises the amino acid sequence as established in SEQ ID NO:48.In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to Contact numbering comprising the amino acid sequence as set forth in SEQ ID NO: 49; CDR2 conforms to Contact numbering comprising the amino acid sequence as set forth in SEQ ID NO: 50; and CDR3 conforms to Contact numbering comprising the amino acid sequence as set forth in SEQ ID NO: 51. In some embodiments, the CDR1 of the DLL3 antibody of the DLL3-ADC conforms to AbM numbering comprising the amino acid sequence set forth in SEQ ID NO: 7; CDR2 conforms to AbM numbering comprising the amino acid sequence set forth in SEQ ID NO: 52; and CDR3 conforms to AbM numbering comprising the amino acid sequence set forth in SEQ ID NO: 9. In some embodiments, a DLL3-ADC as disclosed in this document comprises a DLL3 antibody containing a camel VHH.In some embodiments, DLL3-ADC as disclosed herein comprises a DLL3 antibody that is humanized. In some embodiments, a DLL3-ADC, as described herein, comprises a DLL3 antibody that comprises a human acceptor scaffold, for example, a human immunoglobulin scaffold or a human consensus scaffold.

[0103] In some embodiments, the DLL3-ADC comprises a DLL3 Petition 870250084316, dated 09 / 18 / 2025, pages 255 / 503 60 / 203 comprising a single-domain antibody comprising one or more structures derived from a VHH domain comprising the sequence set forth in SEQ ID NO: 14. In some embodiments, the DLL3-ADC comprises a DLL3 antibody comprising a single-domain antibody comprising one or more structures derived from a VHH domain comprising the sequence set forth in SEQ ID NO: 15. In some embodiments, the DLL3-ADC comprises a DLL3 antibody comprising a single-domain antibody comprising one or more structures derived from a VHH domain comprising the sequence set forth in SEQ ID NO: 16.

[0104] In some embodiments, the DLL3-ADC provided herein comprises a single domain that is a humanized single-domain antibody. The structural regions described herein are determined based on the boundaries of the CDR numbering system. In other words, if the CDRs are determined, for example, by IMGT, Kabat, Chothia, Contact, or AbM, then the structural regions are the amino acid residues surrounding the CDRs in the variable-shape region, from the N-terminus to the C-terminus: FRW1-CDR1-FRW2-CDR2-FRW3-CDR3FRW4.For example, FRW1 is defined as the amino acid residues N-terminal to CDR1 amino acid residues, as defined, for example, by the IMGT numbering system, the Kabat numbering system, the Chothia numbering system, the Contact numbering system, or the AbM numbering system; FRW2 is defined as the amino acid residues between CDR1 and CDR2 amino acid residues, as defined, for example, by the IMGT numbering system, the Kabat numbering system, the Chothia numbering system, the Contact numbering system, or the AbM numbering system; FRW3 is defined as the amino acid residues between CDR2 and CDR3 amino acid residues, as defined, for example, by the IMGT numbering system, the Kabat numbering system, the Chothia numbering system, the Contact numbering system, or the AbM numbering system; and FRW4 is defined as the C-terminal amino acid residues. Petition 870250084316, dated 09 / 18 / 2025, pp. 256 / 503 61 / 203 to the amino acid residues of CDR3 as defined, for example, by the IMGT numbering system, the Kabat numbering system, the Chothia numbering system, the Contact numbering system or the AbM numbering system.

[0105] In some embodiments, the present disclosure provides a DLL3-ADC comprising an isolated DLL3 antibody that includes a VHH domain with the amino acid sequence as set forth in SEQ ID NO:14. In some embodiments, the present disclosure provides a DLL3-ADC comprising a polypeptide that comprises the amino acid sequence of SEQ ID NO:14. In some embodiments, the present disclosure provides a DLL3-ADC comprising an isolated DLL3 antibody that includes a VHH domain with the amino acid sequence as set forth in SEQ ID NO:15. In some embodiments, the present disclosure provides a DLL3-ADC comprising a polypeptide that comprises the amino acid sequence of SEQ ID NO:15. In some embodiments, the present disclosure provides a DLL3-ADC comprising an isolated DLL3 antibody that includes a VHH domain with the amino acid sequence as set forth in SEQ ID NO:16.In some embodiments, the present invention discloses a DLL3-ADC comprising a polypeptide comprising the amino acid sequence SEQ ID NO: 16. DLL3 antibodies comprising VHH sequences

[0106] In some embodiments, a DLL3-ADC, as disclosed herein, comprises a DLL3 antibody comprising a variable heavy chain domain (VH, such as a VHH), wherein VH comprises or consists of: (a) an amino acid sequence as set forth in any of the SEQ ID NOs: 14-16; (b) an amino acid sequence that is at least 85%, at least 90%, or at least 95% identical to any of the SEQ ID NOs: 14-16; or (c) an amino acid sequence with the addition, deletion, and / or substitution of one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10) amino acids compared to any of the SEQ ID NOs: 14-16. Petition 870250084316, dated 09 / 18 / 2025, pp. 257 / 503 62 / 203

[0107] The percentage of identity between two amino acid sequences can be determined using the algorithm of E. Meyers and W. Miller (Comput. Appl. Biosci., 4:11-17 (1988)) which was incorporated into the ALIGN program (version 2.0), using a PAM120 weight residue table, a gap length penalty of 12 and a gap penalty of 4. Additionally, the percentage of identity between two amino acid sequences can be determined by the Needleman and Wunsch algorithm (J. Mol. Biol. 48:444-453 (1970)) which was incorporated into the GAP program in the GCG software package (available at www.gcg.com), using a Blossum 62 matrix or a PAM250 matrix and a gap weight of 16, 14, 12, 10, 8, 6 or 4 and a length weight of 1, 2, 3, 4, 5 or 6.

[0108] Additionally or alternatively, the protein sequences (e.g., antibodies) of this disclosure may also be used as a “query sequence” to perform a search in public databases to, for example, identify related sequences. Such searches can be performed using the XBLAST program (version 2.0) from Altschul, et al. (1990) J. Mol. Biol. 215:403-10. Protein BLAST searches can be performed with the XBLAST program, score = 50, word length = 3 to obtain amino acid sequences homologous to the antibody molecules of the disclosure. In order to obtain gap alignments for comparison purposes, Gapped BLAST can be used as described in Altschul et al, (1997) Nucleic Acids Res. 25(17):3389-3402. When using the BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g., XBLAST and NBLAST) can be used. See www.ncbi.nlm.nih.gov.

[0109] In some embodiments, the amino acid sequence of a VH (such as VHH) may be at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to any of the SEQ ID NOs: 14-16.

[0110] In some other modalities, DLL3 antibodies may Petition 870250084316, dated 09 / 18 / 2025, pp. 258 / 503 63 / 203 contain substitution or conservative modification of amino acids in variable regions of the heavy and / or light chain, such as VH or VHH. It is understood in the art that certain conservative sequence modifications can be made without removing the antigen linkage. See, for example, Brummell et al. (1993) Biochem 32:1180-8; de Wildt et al. (1997) Prot. Eng. 10:835-41; Komissarov et al. (1997) J. Biol. Chem. 272:26864-26870; Hall et al. (1992) J. Immunol. 149:1605-12; Kelley and O'Connell (1993) Biochem. 32:6862-35; Adib-Conquy et al. (1998) Int. Immunol. 10:341-6 and Beers et al. (2000) Clin. Can. Resolution 6:2835-43.

[0111] As described above, the term conservative substitution, as used in this document, refers to an amino acid substitution that would not adversely affect or alter the essential properties of a protein / polypeptide comprising the amino acid sequence. For example, a conservative substitution can be introduced by standard techniques known in the art, such as site-directed mutagenesis and PCR-mediated mutagenesis. Conservative amino acid substitutions include substitutions in which one amino acid residue is replaced by another amino acid residue that has a similar side chain, for example, a physically or functionally similar residue (such as, having similar size, shape, charge, chemical properties, including the ability to form covalent bonds or hydrogen bonds, etc.) to the corresponding amino acid residue.Families of amino acid residues with similar side chains have been defined in the technique. These families include amino acids with alkaline side chains (e.g., lysine, arginine, and histidine), amino acids with acidic side chains (e.g., aspartic acid and glutamic acid), amino acids with uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine, tryptophan), amino acids with nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine), amino acids with β-branched side chains (such as threonine, valine, isoleucine), and... Petition 870250084316, dated 09 / 18 / 2025, pp. 259 / 503 64 / 203 amino acids possessing aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Therefore, a corresponding amino acid residue is preferentially substituted by another amino acid residue from the same side chain family. Methods for identifying conservative amino acid substitutions are well known in the art (see, for example, Brummell et al., Biochem. 32: 1180-1187 (1993); Kobayashi et al., Protein Eng. 12(10): 879-884 (1999) and Burks et al., Proc. Natl. Acad. Sci. USA 94: 412-417 (1997), incorporated herein by reference in their entirety).

[0112] In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising at least one VHH, and the VHH comprises an amino acid sequence as set forth in any of the SEQ ID NOs: 14-16. In some embodiments, a DLL3-ADC comprises a DLL3 antibody comprising a VHH that has an amino acid sequence as set forth in any of the SEQ ID NOs: 14-16.

[0113] In some embodiments, a DLL3-ADC comprises a DLL3 antibody containing a VHH fused to a human IgG1 or IgG4 Fc region (referred to herein as VHH-Fc fusion), wherein the VHH comprises an amino acid sequence as set forth in any of the SEQ ID NOs: 14-16. In some embodiments, a DLL3-ADC comprises a DLL3 antibody containing a VHH and a human IgG1 Fc region. In some additional embodiments, a DLL3-ADC comprises a DLL3 antibody that is a humanized antibody comprising a VHH and a human IgG1 Fc region. In some embodiments, an antibody or an antigen-binding portion thereof comprises a VHH domain containing an amino acid sequence as set forth in any of the SEQ ID NOs: 14-16, and an Fc region containing an amino acid sequence as set forth in SEQ ID NO: 17.In some embodiments, a DLL3ADC comprises a DLL3 antibody containing a polypeptide with an amino acid sequence as set forth in any of the SEQ IDs. Petition 870250084316, dated 09 / 18 / 2025, pp. 260 / 503 65 / 203 NO:4, 5 or 10. In other embodiments, a DLL3-ADC comprises a DLL3 antibody containing a homodimer of a polypeptide with an amino acid sequence as set forth in any of the SEQ IDs NO:4, 5 or 10.

[0114] In some embodiments, the addition, deletion and / or substitution of at least one of the amino acids in the VHH region does not occur in any of the CDR sequences, but rather in the structural sequences (FRW). For example, an antibody or its antigen-binding portion, as described above, may comprise one or more amino acid substitutions in the structural sequences, for example, FRW1, FRW2, FRW3 and / or FRW4 of the VHH region.

[0115] In some embodiments, an antibody or antigen-binding portion thereof, as provided herein, comprises any suitable structural region (FRW) sequences, provided that the antigen-binding domains can specifically bind to DLL3.

[0116] As described above, an antibody or its antigen-binding portion may contain modifications of one or more amino acids in the variable and / or constant regions, including where the modification is a conservative substitution. It is understood in the art that certain conservative modifications may be made to the sequence that do not remove the antigen binding. See, for example, Brummell et al. (1993) Biochem 32:1180-8; de Wildt et al. (1997) Prot. Eng. 10:835-41; Komissarov et al. (1997) J. Biol. Chem. 272:26864-26870; Hall et al. (1992) J. Immunol. 149:1605-12; Kelley and O'Connell (1993) Biochem. 32:6862-35; Adib-Conquy et al. (1998) Int. Immunol. 10:341-6 and Beers et al. (2000) Clin. Can. Resolution 6:2835-43.

[0117] An antigen-binding domain of a DLL3 antibody of a DLL3-ADC is not limited to the VHH form and may adopt several other formats, such as, but not limited to, a Fab, a Fab', an F(ab')2, an Fv fragment, a single-chain antibody molecule (scFv). In some embodiments, an antigen-binding domain is an Fv fragment with a VH region and a VL region on separate chains held together by close interactions and not Petition 870250084316, dated 09 / 18 / 2025, page 261 / 503 66 / 203 covalent bonds. Fc region comprising constant IgG domains

[0118] A DLL3-ADC as disclosed herein comprises a DLL3 antibody further comprising an Fc region comprising one or more human IgG constant domains. A human IgG constant domain may be a human IgG1, IgG2, IgG3, or IgG4 constant domain, preferably a human IgG1 constant domain. An example of the amino acid sequence of an Fc region comprising human IgG1 constant regions is set forth in SEQ ID NO: 17. In some embodiments, the DLL3ADC comprises a DLL3 antibody comprising an amino acid sequence as set forth in any of the SEQ ID NOs: 4, 5, and 10. In some embodiments, the Fc region is a human IgG1 Fc region, such as a wild-type Fc region or an Fc variant comprising one or more amino acid modifications (Leu234Ala / Leu235Ala or LALA) that alters antibody-dependent cellular cytotoxicity (ADCC) or other effector functions.

[0119] In some embodiments, the Fc modification comprises an LALA mutation, for example, L234A and L235A mutations, according to the EU numbering as in Kabat et al. The Kabat numbering system is generally used when referring to a residue in the variable domain (approximately residues 1-107 of the light chain and residues 1-113 of the heavy chain) (e.g., Kabat et al., Sequences of Immunological Interest, 5th Ed., Public Health Service, National Institutes of Health, Bethesda, Md. (1991)). The EU numbering system or EU index is generally used when referring to a residue in a constant region of the immunoglobulin heavy chain (e.g., the EU index reported in Kabat et al., supra). See www.imgt.org / IMGTScientificChart / Numbering / Hu_IGHGnber.html. The “EU numbering as in Kabat” or “EU index as in Kabat” refers to the EU numbering of human IgG1 antibody residues. Unless otherwise indicated herein, references to the numbers of Petition 870250084316, dated 09 / 18 / 2025, pp. 262 / 503 67 / 203 residues in the antibody constant domain mean residue numbering according to the EU numbering system.

[0120] Antibody modifications are included within the scope of this disclosure. Covalent modifications include reacting targeted amino acid residues of an antibody with an organic derivatizing agent that is capable of reacting with selected side chains, or the N- or C-terminal residues of the antibody, such as those disclosed herein. Other modifications include deamidation of glutaminyl and asparaginyl residues to the corresponding glutamyl and aspartyl residues, respectively, hydroxylation of proline and lysine, phosphorylation of hydroxyl groups of seryl or threonyl residues, methylation of α-amino groups of lysine, arginine, and histidine side chains (see, for example, Creighton, Proteins: Structure and Molecular Properties 79-86 (1983)), glycosylation (as N-linked glycosylation), Asp isomerization, oxidation, N-terminal amine acetylation, and amidation of any C-terminal carboxyl group. Nucleic Acid Molecules Encoding DLL3 Antibodies

[0121] A nucleic acid molecule encoding a DLL3 antibody, as disclosed herein, can be readily selected by a specialist in the field. In one aspect, the DLL3 antibody of the DLL3-ADC provided herein can be generated using a nucleic acid molecule comprising a nucleic acid sequence encoding the amino acid sequence as set forth in SEQ ID NO: 14. In one aspect, the DLL3 antibody of the DLL3ADC provided herein can be generated using a nucleic acid molecule comprising a nucleic acid sequence encoding the amino acid sequence as set forth in SEQ ID NO: 15. In one aspect, the DLL3 antibody of the DLL3-ADC provided herein can be generated using a nucleic acid molecule comprising a nucleic acid sequence encoding the amino acid sequence as set forth in SEQ ID NO: 16.

[0122] In some forms, the percentage of identity is derived Petition 870250084316, dated 09 / 18 / 2025, pp. 263 / 503 68 / 203 of the degeneration of the genetic code, and the encoded protein sequences remain unchanged. Host Cells

[0123] The host cells, as disclosed in this disclosure, may be any cell that is suitable for expressing the antibodies of this disclosure, for example, yeast, bacterial, plant and mammalian cells. Mammalian host cells for expressing the antibodies of this disclosure include Chinese Hamster Ovary (CHO cells) (including CHO dhfr cells, described in Urlaub and Chasin, (1980) Proc. Natl. Acad. ScL USA 77:4216-4220, used with a selectable DHFR marker, for example, as described in RJ Kaufman and PA Sharp (1982) J. Mol. Biol. 159:601-621), 293F cells, NSO myeloma cells, COS cells and SP2 cells. In particular, for use with NSO myeloma cells, another expression system is the GS gene expression system disclosed in document no. WO 87 / 04462, document no. WO 89 / 01036 and document no. EP 338,841.Also included are SV4010-transformed monkey kidney CV1 cell lines (COS-7, ATCC CRL 1651); human embryonic kidney cell line (293 or 293 subcloned cells for growth in suspension culture, Graham et al., J. Gen Virol. 36:59 (1977)); baby hamster kidney cells (BHK, ATCC CCL); Chinese hamster ovary / -DHFR cells (CHO, Urlaub et al., 1980, Proc. Natl. Acad. Sci. USA 77:4216); murine Sertoli cells (TM4, Mather, 1980, Biol. Reprod. 23:243-251); monkey kidney cells (CV1 ATCC CCL 70); African green monkey kidney cells (VERO76, ATCC CRL-1587); Human cervical carcinoma cells (HELA, ATCC CCL 2); canine renal cells (MDCK, ATCC CCL 34); buffalo rat liver cells (BRL 3A, ATCC CRL 1442); human lung cells (W138, ATCC CCL 75); human liver cells (Hep G2, HB 8065); mouse mammary tumor (MMT 060562, ATCC CCL51); TRI cells (Mather et al., 1982, Annals NY Acad. Sci.383:44-68); MRC 5 cells; FS4 cells; mouse myeloma cells, such as NSO (e.g., RCB0213, 1992,). Petition 870250084316, dated 09 / 18 / 2025, pp. 264 / 503 69 / 203 Bio / Technology 10:169) and SP2 / 0 cells (e.g., SP2 / 0-Ag14 cells, ATCC CRL 1581); mouse myeloma cells, such as YB2 / 0 cells (e.g., YB2 / 3HL.P2.G11.16Ag.20 cells, ATCC CRL 1662); PER.C6 cells; and a human hepatoma cell line (Hep G2). CHO cells are one of the cell lines that can be used in this document, where CHO-K1, DUK-B11, CHO-DP12, CHO-DG44 (Somatic Cell and Molecular Genetics 12:555 (1986)) and Lec13 are exemplary host cell lines. In the case of CHO-K1, DUK-B11, DG44, or CHO-DP12 host cells, these can be altered so that they are deficient in their ability to fucosylate proteins expressed on them. In some embodiments, the host cells are selected from among CHO, CHO-S, HEK, HEK293, HEK-293F, Expi293F, PER.C6, or NSO cells, or lymphocytic cells.

[0124] Prokaryotes suitable for this purpose include eubacteria, such as Gram-negative or Gram-positive organisms, for example, Enterobacteriaceae such as Escherichia, for example, E. coli, Enterobacter, Erwinia, Klebsiella, Proteus, Salmonella, for example, Salmonella typhimurium, Serratia, for example, Serratia marcescans Shigella, as well as Bacilli such as B. subtilis and B. licheniformis, Pseudomonas such as P. aeruginosae Streptomyces.

[0125] In addition to prokaryotes, eukaryotic microbes, such as filamentous fungi or yeasts, are also suitable hosts for cloning or expression of antibody-encoding vectors. Saccharomyces cerevisiae, or common baker's yeast, is the most commonly used among lower eukaryotic host microorganisms. However, several genera, species, and strains in the present document are commonly available and useful, such as Schizosaccharomyces pombe; Kluyveromyces hosts, such as, for example, K. lactis, K. fragilis (ATCC 12,424), K. bulgaricus (ATCC 16,045), K. wickerhamii (ATCC 24,178), K. waltii (ATCC 56,500), K. drosophilarum (ATCC 36,906), K. thermotolerans, and K. Marxianus; yarrowia (EP 5 402,226); Pichia pastoris (EP 183.070); Candida; Trichoderma reesia (EP 244,234); Neurosporacrassa; Schwanniomyces, such as Petition 870250084316, dated 09 / 18 / 2025, pp. 265 / 503 70 / 203 Schwanniomycesoccidentalis; and filamentous fungi, such as, for example, Neurospora, Penicillium, Tolypocladium, and Aspergillus hosts, such as A. nidulans and A. niger.

[0126] When recombinant expression vectors encoding an antibody are introduced into mammalian host cells, the antibody is produced by culturing the host cells for a period of time sufficient to allow expression of the antibody on the host cells or secretion of the antibody into the culture medium in which the host cells are grown. Antibodies can be recovered from the culture medium using standard protein purification methods. Drug-Linking Conjugates

[0127] DLL3-ADCs comprise a DLL3 antibody conjugated to a drug via a ligand. The ligand and the drug may be collectively referred to herein as a “drug ligand”.

[0128] In one modality, the linker structure is: HCl / I or a salt thereof, where the wavy line represents the drug binding point. In other embodiments, the linking structure is an (R)-epimer of the above linking structure or a salt thereof. Consequently, the linker structure is Petition 870250084316, dated 09 / 18 / 2025, pp. 266 / 503 71 / 203 or a salt thereof. In other embodiments, the linking structure is an (S)-epimer of the linking structure above or a salt thereof. Consequently, the ligand structure is or a salt of it.

[0129] In one embodiment, the drug is an auristatin, for example, MMAE. The structure of MMAE is provided below: Petition 870250084316, dated 09 / 18 / 2025, pp. 267 / 503 72 / 203 MMAE is also known as (2S)-N-[(2S)-1-[[(3R,4S,5S)-1-[(2S)-2[(1 R,2R)-3-[[(1 S,2R)-1 -hydroxy-1 -phenylpropan-2-yl]amino]-1 -methoxy-2-methyl-3oxopropyl]pyrrolid in-1 -yl]-3-methoxy-5-methyl-1 -oxoheptan-4-yl]-methylamino]-3-methyl-1 oxobutan-2-yl]-3-methyl-2-(methylamino)butanamide.

[0130] In one embodiment, the drug is a topoisomerase inhibitor, for example, camptothecin or a derivative thereof, such as Exatecan. The structure of Exatecan is provided below: which is also known as (1S,9S)-1-amino-9-ethyl-5-fluoro-9-hydroxy-4-methyl-1,2,3,9,12,15-hexahydro-1OH,13Hbenzo[de]pyrano[3',4':6,7]indolizino[1,2-b]quinoline-10,13-dione.

[0131] In one embodiment, the binding drug is the binding drug (1): Petition 870250084316, dated 09 / 18 / 2025, pp. 268 / 503 73 / 203 B.C' (1), or a salt thereof, where “Ab” is an acetyl group. The binding drug (1) (or a salt thereof) comprises a ligand conjugated to monomethyl auristatin E (MMAE). In further embodiments, the binding drug is an (R)-epimer of the binding drug (1) or a salt thereof. Consequently, the binding drug is OH (which is also referred to herein as Binding Drug (1) Form A or Binding Drug (1-A)) or a salt thereof. In other embodiments, the binding drug is an (S)-epimer of binding drug (1) or a salt thereof. Consequently, the drug Petition 870250084316, dated 09 / 18 / 2025, p. 269 / 503 74 / 203 binder is OH (which is also referred to herein as Binding Drug (1) Form B or Binding Drug (1-B)) or a salt thereof.

[0132] In one embodiment, the binding drug is the binding drug (2): THE or a salt thereof, where “Ab” is an acetyl group. The binding drug (2) (or Petition 870250084316, dated 09 / 18 / 2025, pp. 270 / 503 75 / 203 a salt thereof) comprises a ligand conjugated to Exatecan. In further embodiments, the ligand drug is an (R)-epimer of the ligand drug (2) or a salt thereof. Consequently, the ligand drug is (which is also referred to herein as Binding Drug (2) Form A or Binding Drug (2-A)) or a salt thereof. In other embodiments, the binding drug is an (S)-epimer of Binding Drug (2) or a salt thereof. Consequently, the binding drug is Petition 870250084316, dated 09 / 18 / 2025, pp. 271 / 503 76 / 203 (which is also referred to here as Binding Drug (2) Form B or Binding Drug (2-B)) or a salt thereof.

[0133] Other suitable binding medicinal products can be found in international patent applications PCT Nos. PCT / JP2021 / 162299, PCT / JP2022 / 036852 (international patent application publication No. WO2023054714 published on April 6, 2023) and PCT / JP2022 / 036835 (international patent application publication No. WO2023054706 published on April 6, 2023), each of which is incorporated herein by reference in its entirety.

[0134] As used herein, the term “salt” includes, for example, salts of inorganic acids, salts of organic acids, salts of inorganic bases, salts of organic bases, and salts of amino acids. Examples of salts of inorganic acids include salts of hydrogen chloride, hydrogen bromide, phosphoric acid, sulfuric acid, and nitric acid. Examples of salts of organic acids include salts of formic acid, acetic acid, trifluoroacetic acid, lactic acid, tartaric acid, fumaric acid, oxalic acid, maleic acid, citric acid, succinic acid, malic acid, benzenesulfonic acid, and p-toluenesulfonic acid. Examples of salts of inorganic bases include salts of alkali metals (for Petition 870250084316, dated 09 / 18 / 2025, pp. 272 / 503 77 / 203 example, sodium, potassium), alkaline earth metals (e.g., calcium, magnesium), other metals such as zinc and aluminum, and ammonium. Examples of salts of organic bases include salts of trimethylamine, triethylamine, propylenediamine, ethylenediamine, pyridine, ethanolamine, monoalkyl ethanolamines, dialkyl ethanolamines, diethanolamine, and triethanolamine. Examples of amino acid salts include salts of basic amino acids (e.g., arginine, histidine, lysine, ornithine) and acidic amino acids (e.g., aspartic acid, glutamic acid). The salt is preferably a salt of an inorganic acid (e.g., hydrogen chloride) or a salt of an organic acid (e.g., trifluoroacetic acid). Antibody-Drug Binding Conjugation

[0135] In some embodiments, the antibody may be modified prior to conjugation to the ligand drug. Modification of the antibody may produce a modified antibody containing one or more reactive groups suitable for conjugation to the ligand drug.

[0136] In some embodiments, the antibody may be modified at one or more amino acid residues to provide one or more reactive groups suitable for conjugation to the ligand drug. For example, amino acid residues and their side chains in the antibody may be chemically modified, as described below, and conjugated to a ligand drug. In certain embodiments, the binding site of the ligand drug (e.g., the conjugated portion of the drug) to the antibody occurs through a cysteine ​​or lysine residue of the DLL3 antibody, as described below.

[0137] Chemical Conjugation in Lysine Residue

[0138] In some embodiments, the antibody may be conjugated to a ligand drug using chemical affinity peptide conjugation (CCAP) methods disclosed in U.S. Patent Application Publication No. 20210139549A1 (Ajinomoto Co. Inc.), which is incorporated herein by reference in its entirety. In particular, a lysine residue of a DLL3 antibody, as disclosed herein, may be chemically modified. Petition 870250084316, dated 09 / 18 / 2025, pp. 273 / 503 78 / 203 by contacting the DLL3 antibody with an affinity peptide conjugated to a thiophenol activation moiety to react the thiophenol with the lysine residue in the antibody to conjugate the affinity peptide to lysine via a peptide bond, as shown below in SCHEMES 1 and 2: SCHEME 1

[0139] The bond between the carboxyl (C=O) and the sulfur can then be cleaved to produce a modified lysine residue with a terminal sulfhydryl group, as shown below in SCHEME 2: Petition 870250084316, dated 09 / 18 / 2025, pp. 274 / 503 79 / 203 Cleavage between -CO- and -S- SCHEME 2

[0140] The modification can occur at a lysine in each antibody chain (e.g., K246 or K248 according to EU numbering), resulting in two conjugation sites, as shown in SCHEME 3 below: Petition 870250084316, dated 09 / 18 / 2025, pp. 275 / 503 80 / 203 SCHEME 3

[0141] In some embodiments, the lysine residue being modified is at one or more of the headings 246, 248, 288, 290 or 317 according to the EU numbering (also referred to in this document as K246, K248, K288, K290 or K317, respectively). In other embodiments, the lysine residue is K246 and / or K248 according to the EU numbering. In still additional embodiments, the lysine residue is K248 according to the EU numbering.

[0142] As used herein, K246, K248, K288, K290, or K317 refer to amino acid residues (lysine, Lys, K) of an immunoglobulin identified according to EU numbering. As would be understood by a specialist in the field, such numbering represents amino acid residues of a polypeptide aligned with those identified in an immunoglobulin, such as that shown at www.imgt.org / IMGTScientificChart / Numbering / Hu_IGHGnber.html. For example, in some embodiments, K246 refers to the 150th residue of Petition 870250084316, dated 09 / 18 / 2025, pp. 276 / 503 81 / 203 amino acid of SEQ ID NO:10, which is lysine; K248 refers to the 152nd amino acid residue of SEQ ID NO:10, which is also lysine; K288 refers to the 192nd amino acid residue of SEQ ID NO:10; K290 refers to the 194th amino acid residue of SEQ ID NO:10; and K317 refers to the 221st amino acid residue of SEQ ID NO:10. In another embodiment, K246 refers to the 148th amino acid residue of SEQ ID NO:4 or 5, which is lysine; K248 refers to the 150th amino acid residue of SEQ ID NO:4 or 5, which is also lysine; K288 refers to the 190th amino acid residue of SEQ ID NO:4 or 5; K290 refers to the 192nd amino acid residue of SEQ ID NO:4 or 5; and K317 refers to the 219th amino acid residue of SEQ ID NO:4 or 5.

[0143] Consequently, a DLL3 antibody having a lysyl side chain (-(CH2)4NH2) of one or more of its lysine residues modified to -(CH2)4NHCO(CH2)2SH, for example, as illustrated in SCHEME 3, is provided herein. In some embodiments, the DLL3 antibody comprises a VHH comprising a CDR1, CDR2, and CDR3, as disclosed herein. In other embodiments, the DLL3 antibody comprises a VHH as disclosed herein. In further embodiments, the DLL3 antibody comprises a VHH-Fc fusion as disclosed in this document, for example, containing an amino acid sequence according to any of the SEQ ID NO: 4, 5, or 10. Additionally or alternatively, the modified lysine residue is selected from one or more of the following: K246, K248, K288, K290, or K317. In further embodiments, the modified lysine residue is K246 and / or K248. In further variations, the lysine residue is K248.These modified DLL3 antibodies of the present invention are useful, for example, as synthetic intermediates in the production of a DLL3 ADC as disclosed herein.

[0144] The terminal sulfhydryl group can react with a maleimide moiety in a binding drug, such as the maleimide moiety in binding drug (1) (or a salt thereof), binding drug (1-A) (or a salt thereof), binding drug (1-B) (or a salt thereof), binding drug (2) (or a salt thereof), binding drug (2-A) (or a salt thereof) or binding drug (2-B) (or a salt thereof) to conjugate the binding drug to it. Petition 870250084316, dated 09 / 18 / 2025, page 277 / 503 82 / 203 as follows, according to SCHEME 4: SCHEME 4

[0145] In one embodiment, the present disclosure provides a method for producing a Formula (I) DLL3-ADC or a salt thereof, as disclosed herein, comprising the steps of: a) provide a solution comprising the DLL3 antibody; b) bring the solution from a) into contact with an affinity peptide conjugated to a thiophenol activation moiety; c) bring the solution from b) into contact with a solution comprising the binding drug (1) or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 278 / 503 83 / 203 (1), where the ADC is made. In some embodiments, the binding drug (1) is the binding drug (1-A): In some embodiments, the binding drug (1-A) is the binding drug (1-B): In some embodiments, the binding drug (1) is a mixture of the binding drug (1-A) and the binding drug (1-B)

[0146] In another embodiment, the present disclosure provides a method for producing a Formula (II) DLL3-ADC or a salt thereof, as disclosed herein, comprising the steps of: a) provide a solution comprising the DLL3 antibody; b) bring the solution from a) into contact with an affinity peptide conjugated to a thiophenol activation moiety; c) bring the solution from b) into contact with a solution comprising the binding drug (2) or a salt thereof: THE 0(2), where the ADC is made. In some embodiments, the binding drug (2) is the Petition 870250084316, dated 09 / 18 / 2025, page 279 / 503 84 / 203 binding drug (2-A): In some embodiments, the binding drug (2) is the binding drug (2-B): In some embodiments, the binding drug (2) is a mixture of the binding drug (2-A) and the binding drug (2-B)

[0147] In one embodiment, the affinity peptide is a peptide with SEQ ID NO: 6. In another embodiment, the affinity peptide conjugated to a thiophenol activation moiety is: THE Ac-RGNCAYHKGQIIWCTYH-NH? (SEQ ID NO: 6) , where Ac is an acetyl moiety and the lines linking the sulfurs of the cysteine ​​residues represent a disulfide bridge. Other affinity peptides and suitable thiophenol activation moieties can be found, for example, in U.S. Patent Application Publication No. 20210139549A1.

[0148] Stochastic conjugation of reduced interchain disulfide bonds

[0149] In some embodiments, the DLL3 antibody is conjugated to a ligand drug via stochastic conjugation to reduce interchain disulfide bonds in the antibody. For example, an IgG1 antibody consists of four polypeptide chains, two heavy chains comprising VH, CH1, and Fc domains (e.g., hinge, CH2 and CH3) and two light chains comprising VL and CL domains, connected by interchain cysteine ​​disulfide (-SS-) bonds (e.g., two heavy chain-light chain interchain disulfide bonds and two heavy chain-heavy chain interchain disulfide bonds). In certain embodiments, when these disulfide bonds are broken under reducing conditions, eight (8) reactive cysteine ​​sulfhydryl groups are produced. In certain embodiments, each of the eight sulfhydryl moieties Petition 870250084316, dated 09 / 18 / 2025, pages 280 / 503 85 / 203 of reactive cystine is a binding site for a ligand drug, so that a maximum of eight (n = 8) ligand drugs can be linked to the reduced antibody. For a VHH-Fc fusion antibody, the antibody may comprise two chains comprising VHH domains fused to an Fc (e.g., hinge, CH2 and CH3), where the two chains are linked via two hinge interchain disulfide bonds (see, for example, Figure 1A). In certain embodiments, when these disulfide bonds are broken under reducing conditions, four (4) reactive cysteine ​​sulfhydryl groups are produced. In certain embodiments, each of the four reactive cystine sulfhydryl moieties is a binding site for a ligand drug, so that a maximum of four (n = 4) ligand drugs can be linked to the reduced antibody.

[0150] In some embodiments, the interchain disulfide bond is between two cysteine ​​residues and is broken under reducing conditions, resulting in two reactive cysteine ​​sulfhydryl moieties. In other embodiments, the interchain disulfide bridge in a DLL3 antibody lies between a heavy chain and a light chain. Additionally, or alternatively, the interchain disulfide bridge in a DLL3 antibody lies between two heavy chains. In some embodiments, the interchain disulfide bridge in a DLL3 antibody lies between two VHH chains. In some embodiments, the interchain disulfide bridge in a DLL3 antibody lies between two VHH-Fc chains. In some embodiments, the cysteine ​​residues are in the hinge region of the DLL3 antibody. In some embodiments, the cysteine ​​residue is at one or more of the 226 or 229 positions according to the EU numbering (also referred to herein as C226 or C229, respectively).

[0151] As used in this document, C226 and C229 refer to amino acid residues (cysteine, Cys, C) of an immunoglobulin identified according to EU numbering. As would be understood by a specialist in the field, such numbering represents amino acid residues of a polypeptide aligned with those identified in an immunoglobulin, such as Petition 870250084316, dated 09 / 18 / 2025, pp. 281 / 503 86 / 203 shown at www.imgt.org / IMGTScientificChart / Numbering / Hu_IGHGnber.html. in For example, in some embodiments, C226 refers to the 130th amino acid residue of SEQ ID NO:10, which is cysteine, and C229 refers to the 133rd amino acid residue of SEQ ID NO:10, which is also cysteine. In another embodiment, C226 refers to the 128th amino acid residue of SEQ ID NO:4 or 5, which is cysteine, and C229 refers to the 131st amino acid residue of SEQ ID NO:4 or 5, which is also cysteine.

[0152] In certain embodiments, the DLL3 antibodies disclosed herein comprise two interchain disulfide bonds in the hinge region that can be reduced, thereby breaking the bond and revealing a reactive sulfhydryl moiety that can be conjugated with a maleimide moiety in a binding drug, such as the maleimide moiety in binding drug (1) (or a salt thereof) or in binding drug (2) (or a salt thereof).

[0153] In one embodiment, the present disclosure provides a method for producing a Formula (I) DLL3-ADC or a salt thereof, comprising the steps of: a) provide a solution comprising the DLL3 antibody; b) bring the solution from a) into contact with a reducing agent; c) bring the solution from b) into contact with a solution comprising the binding drug (1) or a salt thereof: CK,OH o oh (1) where the ADC is made. In some embodiments, the binding drug (1) is the binding drug (1-A): In some embodiments, the binding drug (1) is the drug Petition 870250084316, dated 09 / 18 / 2025, pp. 282 / 503 87 / 203 ligand (1-B): In some embodiments, the ligand drug (1) is a mixture of the ligand drug (1-A) and the ligand drug (1-B).

[0154] In one embodiment, the present disclosure provides a method for producing a Formula (II) DLL3-ADC or a salt thereof, as disclosed herein, comprising the steps of: a) provide a solution comprising the DLL3 antibody; b) bring the solution from a) into contact with a reducing agent; c) bring the solution from b) into contact with a solution comprising the binding drug (2) or a salt thereof: O 0(2), where the ADC is made. In some embodiments, the binding drug (2) is the binding drug (2-A): In some embodiments, the binding drug (2) is the binding drug (2-B): In some embodiments, the binding drug (2) is a mixture of the binding drug (2-A) and the binding drug (2-B).

[0155] In one embodiment, the reducing agent is tris(2-carboxyethyl)phosphine (TCEP). DLL3-ADCS

[0156] Any of the DLL3 antibodies described herein and any of the drug binders or salts thereof, as described herein, may be conjugated to generate a DLL3-ADC.

[0157] In one embodiment, the present disclosure provides an ADC of Petition 870250084316, dated 09 / 18 / 2025, pp. 283 / 503 88 / 203 Formula (I): or its salt, characterized by the fact that: (I), n is an integer from 1 to 8, and Ab represents an antibody that binds to DLL3 (“DLL3 antibody”). In some embodiments, the ADC is an epimer (R) of Formula (I) or a salt thereof. Thus, the ADC is Formula (IA): Petition 870250084316, dated 09 / 18 / 2025, pp. 284 / 503 89 / 203 or a salt thereof. In other embodiments, ADC is an epimer (S) of Formula (I) or a salt thereof. Thus, ADC is Formula (IB): Petition 870250084316, dated 09 / 18 / 2025, pp. 285 / 503 90 / 203

[0158] In one embodiment, the DLL3-ADC of Formula (I), (lA), (lB) or a salt thereof comprises a DLL3 antibody comprising: (1) a CDR1, CDR2 and CDR3 of a VHH, wherein the VHH comprises an amino acid sequence as set forth in SEQ ID NO: 14, 15 or 16; or (2) at least one VHH, wherein the at least one VHH comprises CDR1, CDR2 and CDR3, and wherein: (i) CDR1 comprises an amino acid sequence as set forth in SEQ ID NO: 1 or 7; (ii) CDR2 comprises an amino acid sequence as set forth in SEQ ID NO: 2 or 8; and (iii) CDR3 comprises an amino acid sequence as set forth in SEQ ID NO: 3 or 9.

[0159] In one embodiment, the DLL3-ADC of Formula (I), (lA), (lB), or a salt of any of them, comprises a DLL3 antibody comprising: Petition 870250084316, dated 09 / 18 / 2025, pp. 286 / 503 91 / 203 (a) a CDR1 as set forth in SEQ ID NO:1; a CDR2 as set forth in SEQ ID NO:2; and a CDR3 as set forth in SEQ ID NO:3; or (b) a CDR1 as set forth in SEQ ID NO:7; a CDR2 as set forth in SEQ ID NO:8; and a CDR3 as set forth in SEQ ID NO:9. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt thereof, comprises a DLL3 antibody comprising a VHH comprising an amino acid sequence as set forth in any of the SEQ ID NOS: 14-16. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB) or a salt thereof comprises a DLL3 antibody further comprising a human IgG constant domain. In one embodiment, the human IgG is a human IgG1. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB) or a salt thereof comprises a DLL3 antibody further comprising an Fc fragment.In one embodiment, the Fc fragment comprises a homodimer of an amino acid sequence as set forth in SEQ ID NO:17. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB) or a salt thereof comprises a DLL3 antibody further comprising a VHH domain. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt thereof comprises a DLL3 antibody containing two VHH domains, each of which is conjugated to a chain of an Fc fragment. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB) or a salt thereof comprises a homodimer of an amino acid sequence as set forth in any of the SEQ ID NOS: 4, 5 or 10.

[0160] In one embodiment, n is 1 in Formula (I), (IA) or (IB) (or any of these). In one embodiment, n is 2. In one embodiment, n is 3. In one embodiment, n is 4. In one embodiment, n is 5. In one embodiment, n is 6. In one embodiment, n is 7. In one embodiment, n is 8.

[0161] In certain modalities, this disclosure provides Formula (II) ADC: Petition 870250084316, dated 09 / 18 / 2025, pp. 287 / 503 92 / 203 (II), or a salt thereof, characterized by the fact that: n is an integer from 1 to 8, and Ab represents an antibody that binds to DLL3 (“DLL3 antibody”). In other embodiments, the ADC is an epimer (R) of Formula (II) or a salt thereof. Thus, the ADC is Formula (II-A): (ll-A) or a salt thereof. In other embodiments, ADC is an epimer (S) Petition 870250084316, dated 09 / 18 / 2025, pp. 288 / 503 93 / 203 of Formula (II) or a salt thereof. Thus, the ADC is Formula (ll-B): (ll-B) or a salt of it.

[0162] In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B) or a salt thereof comprises a DLL3 antibody comprising: (1) a CDR1, CDR2 and CDR3 of a VHH, wherein the VHH comprises an amino acid sequence as set forth in SEQ ID NO:14, 15 or 16; or (2) at least one VHH, wherein the at least one VHH comprises CDR1, CDR2 and CDR3, and wherein: (i) the CDR1 comprises an amino acid sequence as set forth in SEQ ID NO:1 or 7; (ii) the CDR2 comprises an amino acid sequence as set forth in SEQ ID NO:2 or 8; and (iii) the CDR3 comprises an amino acid sequence as set forth in SEQ ID NO:3 or 9.

[0163] In one embodiment, the Formula (II), (II-A), (II-B) DLL3-ADC, or a salt thereof, comprises a DLL3 antibody comprising: (a) a CDR1 as set forth in SEQ ID NO:1; a CDR2 as set forth in SEQ ID NO:2; and a CDR3 as set forth in SEQ ID NO:3; or (b) a CDR1 as set forth in SEQ ID NO:7; a CDR2 Petition 870250084316, dated 09 / 18 / 2025, pp. 289 / 503 94 / 203 as set forth in SEQ ID NO:8; and a CDR3 as set forth in SEQ ID NO:9. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B)(IA)(IB), or a salt thereof, comprises a DLL3 antibody comprising a VHH, as set forth in any of the SEQ ID NOS: 14-16. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B) or a salt thereof comprises a DLL3 antibody further comprising a human IgG constant domain. In one embodiment, the human IgG is a human IgG1. In one embodiment, the DLL3ADC of Formula (II), (II-A), (II-B) or a salt thereof comprises a DLL3 antibody further comprising an Fc fragment. In one embodiment, the Fc fragment comprises a homodimer of an amino acid sequence as set forth in SEQ ID NO:17. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B) or a salt thereof comprises a DLL3 antibody further comprising a VHH domain.In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B) or a salt thereof comprises a DLL3 antibody comprising two VHH domains, each of which is conjugated to a chain of an Fc fragment. In another embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B) or a salt thereof comprises a homodimer of an amino acid sequence as set forth in any of the SEQ ID NOS: 4, 5 or 10.

[0164] In one modality, n is 1 in Formula (II), (II-A) or (II-B) (or a salt thereof). In one modality, n is 2. In one modality, n is 3. In one modality, n is 4. In one modality, n is 5. In one modality, n is 6. In one modality, n is 7. In one modality, n is 8.

[0165] In one embodiment, the DLL3-ADC is of the following Formula (A): Petition 870250084316, dated 09 / 18 / 2025, pp. 290 / 503 95 / 203 (A), where each thick shaded line represents a chain of an antibody that binds to DLL3 (the DLL3 antibody), the sulfurs shown are cysteine ​​residues of the DLL3 antibody and X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 291 / 503 96 / 203 HO where the wavy line represents the connection point for the remainder of the ADC of Formula (A). In some embodiments, the cysteine ​​residues are in the hinge region of the DLL3 antibody. In other embodiments, the cysteine ​​residues form an interchain disulfide bridge in a DLL3 antibody not directly or indirectly conjugated to X, for example, between two heavy chains, between a heavy chain and a light chain, between two VHH chains, or between two VHH-Fc chains. In other embodiments, the cysteine ​​residue is at one or more of the 226 or 229 positions according to the EU numbering (also referred to herein as C226 or C229, respectively). In other embodiments, X is an epimer (R) of the structure or a salt thereof. Thus, X represents: Petition 870250084316, dated 09 / 18 / 2025, pp. 292 / 503 97 / 203 OH or a salt thereof, where the wavy line represents the point of attachment to the remainder of the ADC of Formula (A). In other embodiments, X is an epimer (S) of the structure or a salt thereof. Thus, X represents: Petition 870250084316, dated 09 / 18 / 2025, pp. 293 / 503 98 / 203 OH or a salt of this, where the wavy line represents the point of connection to the rest of the ADC of Formula (A).

[0166] In one embodiment, the DLL3-ADC is of the following Formula (B): Petition 870250084316, dated 09 / 18 / 2025, pp. 294 / 503 99 / 203 (B), where each thick shaded line represents a chain of an antibody that binds to DLL3 (the DLL3 antibody), the CH2CH2CH2CH2NH cluster shown comes from a lysine residue of the CH2 domain of the DLL3 antibody, and X represents the structure below: Petition 870250084316, dated 09 / 18 / 2025, pp. 295 / 503 100 / 203 where the wavy line represents the connection point for the remainder of the ADC of Formula (B). In some embodiments, the lysine residue is at one or more of the positions 246, 248, 288, 290 or 317 according to the EU numbering (also referred to in this document as K246, K248, K288, K290 or K317, respectively). In other embodiments, X is an epimer (R) of the structure or a salt thereof. Thus, X represents: Petition 870250084316, dated 09 / 18 / 2025, pp. 296 / 503 101 / 203 or a salt thereof, where the wavy line represents the point of attachment to the remainder of the ADC of Formula (B). In other embodiments, X is an epimer (S) of the structure or a salt thereof. Thus, X represents: Petition 870250084316, dated 09 / 18 / 2025, pp. 297 / 503 102 / 203 OH or a salt of this, where the wavy line represents the point of connection to the rest of the ADC of Formula (B).

[0167] In one embodiment, DLL3-ADC is of Formula (A), or a salt thereof, as represented above, wherein each thick shaded line represents a chain of an antibody that binds to DLL3 (the DLL3 antibody), the sulfurs represented are cysteine ​​residues of the DLL3 antibody, and X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pages 298 / 503 103 / 203 H Ch / O where the wavy line represents the attachment point to each maleimide moiety represented in Formula (A). In some embodiments, the cysteine ​​residues are in the hinge region of the DLL3 antibody. In other embodiments, the cysteine ​​residues form an interchain disulfide bridge in a DLL3 antibody not directly or indirectly conjugated to X, for example, between two heavy chains, between a heavy chain and a light chain, between two VHH chains, or between two VHH-Fc chains. In other embodiments, the cysteine ​​residue is at one or more of the 226 or 229 positions according to the EU numbering (also referred to herein as C226 or C229, respectively). In other embodiments, X is an epimer (R) of the structure or a salt thereof. Thus, X represents: Petition 870250084316, dated 09 / 18 / 2025, pp. 299 / 503 104 / 203 or a salt thereof, where the wavy line represents the point of attachment to the remainder of the ADC of Formula (A). In other embodiments, X is an epimer (S) of the structure or a salt thereof. Thus, X represents: or a salt of this, where the wavy line represents the point of connection to the rest of the ADC of Formula (A).

[0168] In one embodiment, the DLL3-ADC is of Formula (B), or a salt thereof, as represented above, where each thick shaded line Petition 870250084316, dated 09 / 18 / 2025, pp. 300 / 503 105 / 203 represents a chain of an antibody that binds to DLL3 (DLL3 antibody), the CH2CH2CH2CH2NH cluster shown comes from a lysine residue of the CH2 domain of the DLL3 antibody, and X represents the structure below: where the wavy line represents the attachment point to each maleimide group represented in Formula (B). In some embodiments, the lysine residue is found at any one or more of the positions 246, 248, 288, 290 or 317, according to the EU numbering (also referred to in this document as K246, K248, K288, K290 or K317, respectively). In other embodiments, X is an epimer (F?) of the structure or a salt thereof. Thus, X represents: Petition 870250084316, dated 09 / 18 / 2025, pp. 301 / 503 106 / 203 or a salt thereof, where the wavy line represents the connection point for the remainder of the ADC of Formula (B). In other embodiments, X is an epimer (S) of the structure or a salt thereof. Thus, X represents: CT OH or a salt thereof, where the wavy line represents the point of attachment to the remainder of the ADC of Formula (B).

[0169] In some embodiments, the DLL3 antibody of Formula (A) or Formula (B) comprises an amino acid sequence as set forth in SEQ ID NO:4, wherein the lysine residue is K248 of the DLL3 antibody, for example, the 150th amino acid residue of SEQ ID NO:4. In some embodiments, the DLL3 antibody of Formula (A) or Formula (B) or a salt thereof comprises an amino acid sequence as set forth in SEQ ID NO:5, wherein the lysine residue is K248 of the DLL3 antibody, for example, the 150th amino acid residue of SEQ ID NO:5. In some embodiments, the DLL3 antibody of Formula (A) or Formula (B) or a salt thereof comprises an amino acid sequence as set forth in SEQ ID NO:10, wherein the lysine residue is K248 of the DLL3 antibody, for example, the 152nd amino acid residue of SEQ ID NO:10.

[0170] Additionally or alternatively, Formula (A) DLL3 antibody or Petition 870250084316, dated 09 / 18 / 2025, pp. 302 / 503 107 / 203 Formula (B) comprises an amino acid sequence as set forth in SEQ ID NO:4, wherein the lysine residue is K246 of the DLL3 antibody, for example, the 148th amino acid residue of SEQ ID NO:4. In some embodiments, the DLL3 antibody of Formula (A) or Formula (B) or a salt thereof comprises an amino acid sequence as set forth in SEQ ID NO:5, wherein the lysine residue is K246 of the DLL3 antibody, for example, the 148th amino acid residue of SEQ ID NO:5. In some embodiments, the DLL3 antibody of Formula (A) or Formula (B) or a salt thereof comprises an amino acid sequence as set forth in SEQ ID NO:10, wherein the lysine residue is K246 of the DLL3 antibody, for example, the 150th amino acid residue of SEQ ID NO:10.

[0171] In one embodiment, the DLL3-ADC is of the following Formula (C): (C) or a salt thereof, where each thick shaded line represents a chain of an antibody that binds to DLL3 (the DLL3 antibody), the CH2CH2CH2CH2NH cluster shown is derived from a lysine residue of the CH2 domain of the DLL3 antibody. In other embodiments, DLL3-ADC is an epimer (F?) of Formula (C) or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 303 / 503 108 / 203 VV (CA) In some embodiments, DLL3-ADC is an epimer (S) of Formula (C), for example, Formula (CB), or a salt thereof: V \J (CB)

[0172] In one embodiment, the DLL3-ADC is of the following Formula (D): Petition 870250084316, dated 09 / 18 / 2025, pp. 304 / 503 109 / 203 (D) or a salt thereof, where each thick shaded line represents a chain of an antibody that binds to DLL3 (the DLL3 antibody), the CH2CH2CH2CH2NH cluster shown is derived from a lysine residue of the CH2 domain of the DLL3 antibody. In other embodiments, DLL3-ADC is an epimer (R) of Formula (D), for example, Formula (DA), or a salt thereof: V u (DA) In some embodiments, DLL3-ADC is an epimer (S) of Formula (D), for example, Formula (DB), or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, pp. 305 / 503 110 / 203 UU (DB)

[0173] In some embodiments, the Formula (C) or Formula (D) DLL3 antibody or any salt thereof comprises an amino acid sequence as set forth in SEQ ID NO:4, wherein the lysine residue is K248 of the DLL3 antibody, for example, the 150th amino acid residue of SEQ ID NO:4. In some embodiments, the Formula (C) or Formula (D) DLL3 antibody or a salt thereof comprises an amino acid sequence as set forth in SEQ ID NO:5, wherein the lysine residue is K248 of the DLL3 antibody, for example, the 150th amino acid residue of SEQ ID NO:5. In some embodiments, the Formula (C) or Formula (D) DLL3 antibody or a salt of either comprises an amino acid sequence as set forth in SEQ ID NO: 10, wherein the lysine residue is K152 of the DLL3 antibody, for example, the 152nd amino acid residue of SEQ ID NO: 10.

[0174] Additionally or alternatively, the DLL3 antibody of Formula (C), (CA), (CB), (D), (DA), (DB) or a salt of any of them, comprises an amino acid sequence as set forth in SEQ ID NO:4, wherein the lysine residue is K246 of the DLL3 antibody, for example, the 148th amino acid residue of SEQ ID NO:4. In some embodiments, the DLL3 antibody of Formula (C), (CA), (CB), (D), (DA), (DB) or a salt of any of them comprises an amino acid sequence as set forth in SEQ ID NO:5, wherein the lysine residue is K246 of the DLL3 antibody, for example, the 148th Petition 870250084316, dated 09 / 18 / 2025, pp. 306 / 503 111 / 203 amino acid residue of SEQ ID NO:5. In some embodiments, the DLL3 antibody of Formula (C), (CA), (CB), (D), (DA), (DB) or a salt of any of them comprises an amino acid sequence as set forth in SEQ ID NO:10, wherein the lysine residue is K246 of the DLL3 antibody, for example, the 150th amino acid residue of SEQ ID NO:10.

[0175] In some embodiments, DLL3-ADC is represented by Formula (I), (IA), (IB), (II), (II-A), (II-B) or a salt of any of them, wherein Ab is DLL3 antibody comprising a VHH comprising one or more CDRs comprising an amino acid sequence identical or substantially identical to one or more of the SEQ ID NOs: 1-3 and 7-9.

[0176] In some embodiments, DLL3-ADC is represented by Formula (I), (IA), (IB), (II), (II-A), (II-B) or a salt of any of them, wherein Ab is DLL3 antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to one or more of the SEQ ID NOs: 14-16.

[0177] In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 14 en 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 14 en 4. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises the Binding Drug (1), the Binding Drug (1-A), the Binding Drug (1-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them, through the K248 residue of each chain of the DLL3 antibody, wherein the DLL3 antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:14.Thus, n is 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any one. Petition 870250084316, dated 09 / 18 / 2025, pp. 307 / 503 112 / 203 of them, comprises the Binding Drug (1), the Binding Drug (1-A), the Binding Drug (1-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them by means of one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:14. In some embodiments, one or more disulfide bridges prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0178] In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 15 en 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 15 en 4. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises the Binding Drug (1), the Binding Drug (1-A), the Binding Drug (1-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them, through the K248 residue of each chain of the DLL3 antibody, wherein the DLL3 antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:15.Thus, n is 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises the Binding Drug (1), the Binding Drug (1-A), the Binding Drug (1-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them by means of one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the. Petition 870250084316, dated 09 / 18 / 2025, pp. 308 / 503 113 / 203 antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:15. In some embodiments, one or more disulfide bridges before reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0179] In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 16 en 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 16 en 4. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises the Binding Drug (1), the Binding Drug (1-A), the Binding Drug (1-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them, through the K248 residue of each chain of the DLL3 antibody, wherein the DLL3 antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:16.Thus, n is 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them, comprises the Binding Drug (1), the Binding Drug (1-A), the Binding Drug (1-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them by means of one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:16. In some embodiments, one or more disulfide bridges prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Petition 870250084316, dated 09 / 18 / 2025, pp. 309 / 503 114 / 203 Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0180] In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 14 en 2. In another embodiment, the DLL3ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 14 en 4.In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them, through the K248 residue of each DLL3 antibody chain, wherein the DLL3 antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:14. Then, n is 2.In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them by means of one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:14. In some embodiments, one or more disulfide bridges prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0181] In one embodiment, the Formula (II), (II-A), (II-B), or DLL3-ADC Petition 870250084316, dated 09 / 18 / 2025, pp. 310 / 503 115 / 203 a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 15 en 2. In one embodiment, the DLL3ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 15 en 4. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them, through the K248 residue of each chain of the DLL3 antibody, wherein the DLL3 antibody comprises a VHH comprising a The amino acid sequence is identical or substantially identical to SEQ ID NO:15. Therefore, n is 2.In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them by means of one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:15. In some embodiments, one or more disulfide bridges prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0182] In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO: 16 en e 2. In one embodiment, the DLL3ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises Petition 870250084316, dated 09 / 18 / 2025, pp. 311 / 503 116 / 203 an antibody comprising a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:16 and n is 4. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them, through the K248 residue of each chain of the DLL3 antibody, wherein the DLL3 antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:16. Then, n is 2.In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them by means of one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody comprises a VHH comprising an amino acid sequence identical or substantially identical to SEQ ID NO:16. In some embodiments, one or more disulfide bridges prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0183] In some embodiments, DLL3-ADC is represented by Formula (I), (IA), (IB), (II), (II-A), (II-B) or a salt of any of them, wherein Ab is DLL3 antibody comprising an amino acid sequence identical or substantially identical to one of the SEQ ID NOs: 4, 5 and 10. In some embodiments, a cysteine ​​or lysine residue of the DLL3 antibody is modified as disclosed herein and conjugated to a drug linker as disclosed herein.

[0184] In one embodiment, the DLL3-ADC comprises a DLL3 antibody and two or more Drug-Ligator (1), or a salt thereof, conjugated to it. In a Petition 870250084316, dated 09 / 18 / 2025, pp. 312 / 503 In embodiment 117 / 203, DLL3-ADC comprises a DLL3 antibody and two or more Drug-Ligator (1-A) conjugates, or a salt thereof. In another embodiment, DLL3-ADC comprises a DLL3 antibody and two or more Drug-Ligator (1B) conjugates, or a salt thereof.

[0185] In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises a DLL3 antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:4, wherein n is 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises a DLL3 antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:4, wherein n is 4. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises Binding Drug (1), Binding Drug (1-A), Binding Drug (1-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them via the K248 residue of each chain of the DLL3 antibody, wherein the antibody contains an amino acid sequence identical or substantially identical to SEQ ID NO:4. Consequently, n is 2.In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises Binding Drug (1), Binding Drug (1-A), Binding Drug (1-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them via one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody contains an amino acid sequence identical or substantially identical to SEQ ID NO:4. In some embodiments, the disulfide bridge(s) prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0186] In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises a DLL3 antibody containing a Petition 870250084316, dated 09 / 18 / 2025, pages 313 / 503 118 / 203 amino acid sequence identical or substantially identical to SEQ ID NO:5, where n is 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises a DLL3 antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:5, where n is 4. In another embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises Binding Drug (1), Binding Drug (1-A), Binding Drug (1-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them via residue K248 of each chain of the DLL3 antibody, wherein the antibody contains an amino acid sequence identical or substantially identical to SEQ ID NO:5. Consequently, n is 2.In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of any of them comprises Binding Drug (1), Binding Drug (1-A), Binding Drug (1-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (I), (IA), (IB), or a salt of any of them via one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody contains an amino acid sequence identical or substantially identical to SEQ ID NO:5. In some embodiments, the disulfide bridge(s) prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0187] In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt thereof, comprises a DLL3 antibody comprising an amino acid sequence identical or substantially identical to SEQ ID NO:10, wherein n is 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt thereof, comprises a DLL3 antibody comprising an amino acid sequence identical or substantially identical to SEQ ID NO:10, wherein n is 4. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt thereof, comprises the Drug Petition 870250084316, dated 09 / 18 / 2025, pp. 314 / 503 119 / 203 Ligand (1), Ligand Drug (1-A), Ligand Drug (1-B), or a salt of either, which is conjugated to DLL3 antibody of Formula (I), (IA), (IB), or a salt of either, through the K248 residue of each DLL3 antibody chain, wherein the antibody comprises an amino acid sequence identical or substantially identical to SEQ ID NO:10. Thus, n is 2. In one embodiment, the DLL3-ADC of Formula (I), (IA), (IB), or a salt of either, comprises Ligand Drug (1), Ligand Drug (1-A), Ligand Drug (1-B), or a salt of either, which is conjugated to DLL3 antibody of Formula (I), (IA), (IB), or a salt of either through one or more reduced disulfide bridges of each DLL3 antibody chain, wherein the antibody comprises an amino acid sequence identical or substantially identical to SEQ ID NO:10.In some embodiments, one or more disulfide bridges prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0188] In one embodiment, the DLL3-ADC comprises a DLL3 antibody and two or more Drug-Ligator (2), or a salt thereof, conjugated to it.

[0189] In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises a DLL3 antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:4, wherein n is 2. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises a DLL3 antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:4, wherein n is 4. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises Binding Drug (2), Binding Drug (2-A), Binding Drug (2-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them via the K248 residue of each chain of the DLL3 antibody, and the antibody Petition 870250084316, dated 09 / 18 / 2025, pp. 315 / 503 120 / 203 contains an amino acid sequence identical or substantially identical to SEQ ID NO:4. Consequently, n is 2. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises Binding Drug (2), Binding Drug (2-A), Binding Drug (2-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them via one or more reduced disulfide bridges of each chain of the DLL3 antibody, with the antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:4. In some embodiments, the disulfide bridge(s) prior to reduction are selected from those formed between C226 and C229 of two chains of the antibody. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0190] In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises a DLL3 antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:5, wherein n is 2. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises a DLL3 antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:5, wherein n is 4. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises Binding Drug (2), Binding Drug (2-A), Binding Drug (2-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them via the K248 residue of each chain of the DLL3 antibody, with the antibody containing a sequence of amino acids identical or substantially identical to SEQ ID NO:5. Consequently, n is 2.In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them comprises Binding Drug (2), Binding Drug (2-A), Binding Drug (2-B), or a salt of any of them, conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them via one or more reduced disulfide bridges of each. Petition 870250084316, dated 09 / 18 / 2025, pp. 316 / 503 121 / 203 antibody chain DLL3, with the antibody containing an amino acid sequence identical or substantially identical to SEQ ID NO:5. In some embodiments, the disulfide bridge(s) before reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both antibody chains are modified to conjugate directly or indirectly to a binding drug, as disclosed herein, and thus n is 4.

[0191] In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises a DLL3 antibody comprising an amino acid sequence identical or substantially identical to SEQ ID NO:10, wherein n is 2. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises a DLL3 antibody comprising an amino acid sequence identical or substantially identical to SEQ ID NO:10, wherein n is 4. In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them, via residue K248. of each chain of the DLL3 antibody, where the antibody comprises an amino acid sequence identical or substantially identical to SEQ ID NO:10. Therefore, n is 2.In one embodiment, the DLL3-ADC of Formula (II), (II-A), (II-B), or a salt of any of them, comprises the Binding Drug (2), the Binding Drug (2-A), the Binding Drug (2-B), or a salt of any of them, which is conjugated to the DLL3 antibody of Formula (II), (II-A), (II-B), or a salt of any of them by means of one or more reduced disulfide bridges of each chain of the DLL3 antibody, wherein the antibody comprises an amino acid sequence identical or substantially identical to SEQ ID NO:10. In some embodiments, one or more disulfide bridges prior to reduction are selected from those formed between C226 and C229 of two antibody chains. Thus, n is 2 or 4. In some embodiments, both C226 and C229 of both chains are included. Petition 870250084316, dated 09 / 18 / 2025, pp. 317 / 503 122 / 203 antibodies are modified to conjugate directly or indirectly to a binding drug, as disclosed here, and thus n is 4.

[0192] The DLL3-ADC of the present invention may have superior properties, such as long retention time in the body, high monomer ratio (low aggregation rate), high capacity for releasing functional substance in human cells, high stability (e.g., in mouse plasma) and desirable cytotoxicity for target cells (such as cancer cells that express or overexpress DLL3). COMPOSITIONS

[0193] In another embodiment, the present disclosure provides a composition comprising DLL3-ADCs as disclosed herein. A composition may comprise a plurality of DLL3-ADCs, as disclosed herein, wherein each DLL3-ADC in the composition independently comprises a binding drug, as shown in Formula (I), (IA), (IB), (II), (II-A), (II-B), or a salt of any of them, wherein n is independently 1, 2, 3, or 4. In other words, each antibody molecule in the composition may be conjugated to 1, 2, 3, or 4 binding drugs. Therefore, a composition may be characterized by a “drug-to-antibody” ratio (DAR) ranging from about 1 to about 4. Methods for determining DAR are well known to the expert and include methods using reverse-phase chromatography, or HPLC-MS.

[0194] For example, in any given embodiment, a composition comprising a plurality of DLL3-ADCs may exhibit a DAR of about 1 to about 4, about 1 to about 3, about 1 to about 2, about 2 to about 4, about 2 to about 3, about 3 to about 4, about 1.5 to about 2, about 1.8 to about 2, about 1.9 to about 2, about 3.5 to about 4, about 3.6 to about 4, about 3.7 to about 4, about 3.8 to about 4, about 3.9 to about 4, about 3.5 to about 3.9, about 3.6 to about 3.9, about 3.7 to about 3.9, about 3.8 to about 3.9, about 3.5 to about 3.8, about 3.6 to about 3.8, about 3.7 to about 3.8, about Petition 870250084316, dated 09 / 18 / 2025, pages 318 / 503 123 / 203 3.5 to about 3.7, about 3.6 to about 3.7, or about 3.5 to about 3.6. In one modality, the DAR is approximately 1 to approximately 2. In one modality, the DAR is approximately 1.1, approximately 1.2, approximately 1.3, approximately 1.4, approximately 1.5, approximately 1.6, approximately 1.7, approximately 1.8, approximately 1.9, or approximately 2. In one modality, the DAR is approximately 2 to approximately 4. In one modality, the DAR is approximately 2, approximately 2.1, approximately 2.2, approximately 2.4, approximately 2.4, approximately 2.5, approximately 2.6, approximately 2.7, approximately 2.8, approximately 2.9, approximately 3, approximately 3.1, approximately 3.2, approximately 3.3, approximately 3.4, approximately 3.5, approximately 3.6, approximately 3.7, approximately 3.8, approximately 3.9, or approximately 4.

[0195] In some embodiments, DLL3-ADC comprises a DLL3 antibody, as disclosed herein, conjugated to a binding drug, as disclosed herein, via a lysine residue of the antibody, as disclosed herein, such as K246, K248, K288, K290, or K317. Consequently, a composition comprising DLL3-ADC is provided herein. In some embodiments, a composition comprising DLL3-ADC exhibits a DAR of about 1.5 to about 2.5. In some embodiments, the composition exhibits a DAR of 1.5 or greater, 1.6 or greater, 1.7 or greater, 1.8 or greater, or 1.9 or greater. Additionally, or alternatively, the composition exhibits a DAR of 2.5 or less, 2.4 or less, 2.3 or less, 2.2 or less, or 2.1 or less. In some embodiments, the composition exhibits a DAR of 1.6 to 2.4, 1.7 to 2.3, 1.8 to 2.2, or 1.9 to 2.1. In some embodiments, a composition comprising DLL3-ADC exhibits a DAR of approximately 1.9 to approximately 2.1.

[0196] In one embodiment, a composition comprising DLL3ADCs, as disclosed herein, may exhibit a DAR of about 2, wherein the binding drugs are conjugated via site-specific conjugation, as described herein, to a DLL3 antibody lysine of the DLL3-ADC (e.g., K246, K248, K288, K290, or K317 in the CH2 domain). In another embodiment, a composition comprising DLL3-ADCs, as disclosed herein, may exhibit a DAR of about 4, wherein the binding drugs are conjugated to reduced cysteine ​​moieties of a disulfide bridge. Petition 870250084316, dated 09 / 18 / 2025, pp. 319 / 503 124 / 203 interstrand, for example, in the hinge region of the DLL3 antibody of the DLL3ADC. USES, FORMULATION AND DOSAGE

[0197] In another aspect, the present disclosure provides a pharmaceutical composition comprising a DLL3-ADC, as disclosed herein, and a pharmaceutically acceptable carrier. In another aspect, the present disclosure provides a pharmaceutical composition comprising a composition of disclosed DLL3-ADCs or a pharmaceutically acceptable salt and a pharmaceutically acceptable carrier (a DLL3-ADC pharmaceutical composition). A DLL3-ADC pharmaceutical composition may comprise a plurality of DLL3-ADCs, as disclosed herein, wherein each DLL3-ADC in the pharmaceutical composition independently comprises a linker drug, as shown in Formula (I), (IA), (IB), (II), (II-A), (II-B), or a salt of any of them, wherein n is independently 1, 2, 3 or 4. In other words, each antibody molecule in the DLL3-ADC pharmaceutical composition may be conjugated to 1, 2, 3 or 4 linker drugs.Therefore, a DLL3-ADC pharmaceutical composition can be characterized by a DAR ranging from about 1 to about 4.

[0198] In one embodiment, a DLL3-ADC pharmaceutical composition may exhibit a DAR of about 2, wherein the binding drugs are conjugated via site-specific conjugation, as described herein, to a DLL3 antibody lysine (e.g., K246, K248, K288, K290, or K317 of the CH2 domain) of the DLL3-ADC. In another embodiment, a DLL3-ADC pharmaceutical composition may exhibit a DAR of about 4, wherein the binding drugs are conjugated to reduced cysteine ​​moieties of an interchain disulfide bridge, for example, in the hinge region, of the DLL3 antibody.

[0199] In other embodiments, a DLL3-ADC pharmaceutical composition comprises 20 mM histidine. Additionally or alternatively, a DLL3-ADC pharmaceutical composition comprises 5% trehalose. Petition 870250084316, dated 09 / 18 / 2025, pp. 320 / 503 125 / 203 Additionally or alternatively, a DLL3-ADC pharmaceutical composition has a pH of about 5 to about 6, such as 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, or 6.0. In other embodiments, a DLL3-ADC pharmaceutical composition comprises 20 mM histidine and 5% trehalose, and has a pH of approximately 5 to approximately 6, such as 5.1; 5.2; 5.3; 5.4; 5.5; 5.6; 5.7; 5.8; 5.9; or 6.0. In further embodiments, a DLL3-ADC pharmaceutical composition comprises 20 mM histidine and 5% trehalose and has a pH of 6.0.

[0200] A pharmaceutical composition of the disclosure may be administered to a subject in need thereof by various routes, including, but not limited to, oral, intravenous, intra-arterial, subcutaneous, parenteral, intranasal, intramuscular, intracranial, intracardiac, intraventricular, intratracheal, buccal, rectal, intraperitoneal, intradermal, topical, transdermal and intrathecal, or otherwise by implantation or inhalation. The compositions in question may be formulated in solid, semi-solid, liquid or gaseous preparations; including, but not limited to, tablets, capsules, powders, granules, ointments, solutions, suppositories, enemas, injections, inhalants and aerosols. The appropriate formulation and route of administration may be selected according to the intended application and therapeutic regimen.

[0201] Suitable formulations for enteric administration include hard or soft gelatin capsules, pills, tablets, including coated tablets, elixirs, suspensions, syrups or inhalations and their controlled-release forms.

[0202] Suitable formulations for parenteral administration (e.g., by injection) include sterile aqueous or non-aqueous, isotonic, pyrogen-free liquids (e.g., solutions, suspensions) in which the active ingredient is dissolved, suspended, or otherwise delivered (e.g., in a liposome or other microparticulate). Such liquids may additionally contain other pharmaceutically acceptable ingredients, such as antioxidants, buffers, preservatives, stabilizers, bacteriostatics, suspending agents, thickening agents, and solutes that make the formulation Petition 870250084316, dated 09 / 18 / 2025, pp. 321 / 503 126 / 203 isotonic with the blood (or other relevant body fluid) of the intended recipient. Examples of excipients include, for example, water, alcohols, polyols, glycerol, vegetable oils, and the like. Examples of isotonic carriers suitable for use in these formulations include sodium chloride injection, Ringer's solution, or Ringer's lactate injection. Similarly, the specific dosing regimen, including dose, timing, and repetition, will depend on the specific individual and that individual's medical history, as well as empirical considerations such as pharmacokinetics (e.g., half-life, clearance rate, etc.).

[0203] The frequency of administration can be determined and adjusted throughout therapy and is based on the reduction in the number of proliferative or tumorigenic cells, the maintenance of the reduction of such neoplastic cells, the reduction in the proliferation of neoplastic cells, or the delay in the development of metastases. In some modalities, the administered dosage may be adjusted or attenuated to control potential side effects and / or toxicity. Alternatively, sustained-release formulations of a therapeutic composition in question may be appropriate.

[0204] It will be appreciated by a person skilled in the art that appropriate dosages may vary from patient to patient. In general, determining the ideal dosage will involve balancing the level of therapeutic benefit and any risk or deleterious side effects. The dosage level selected will depend on a variety of factors including, but not limited to, the activity of the specific compound, the route of administration, the time of administration, the rate of excretion of the compound, the duration of treatment, other drugs, compounds and / or materials used in combination, the severity of the condition, and the species, sex, age, weight, condition, general health and previous medical history of the patient. The amount of compound and the route of administration will ultimately be at the discretion of the physician, veterinarian or clinician, although generally the dosage is selected to achieve local concentrations at the site of action that achieve the desired effect without Petition 870250084316, dated 09 / 18 / 2025, pp. 322 / 503 127 / 203 cause substantial damage or deleterious side effects.

[0205] In general, a DLL3-ADC from the disclosure can be administered in several ranges. These ranges include approximately 5 μg / kg of body weight to approximately 100 mg / kg of body weight per dose, approximately 50 μg / kg of body weight to approximately 5 mg / kg of body weight per dose, approximately 100 μg / kg of body weight to approximately 10 mg / kg of body weight per dose, and any values ​​within these ranges. Other ranges include approximately 100 μg / kg of body weight to approximately 20 mg / kg of body weight per dose and approximately 0.5 mg / kg of body weight to approximately 20 mg / kg of body weight per dose. In some forms, the dosage is at least about 100 μg / kg of body weight, at least about 250 μg / kg of body weight, at least about 750 μg / kg of body weight, at least about 3 mg / kg of body weight, at least about 5 mg / kg of body weight, at least about 10 mg / kg of body weight.

[0206] In any case, an antibody or antigen-binding portion of the same from the disclosure is administered, preferably as needed, to subjects (or a subject) who require it. The frequency of administration may be determined by persons skilled in the art, such as an attending physician, based on considerations of the condition to be treated, the age of the subject to be treated, the severity of the condition to be treated, the general health status of the subject being treated, and so forth.

[0207] In some embodiments, the course of treatment involving a DLL3-ADC of the present disclosure will comprise multiple doses of the selected drug over a period of weeks or months. For example, a DLL3ADC of the present disclosure may be administered once daily, every other day, every four days, every week, every ten days, every two weeks, every three weeks, every month, every six weeks, every two months, every ten weeks, or every three months. In this regard, it will be noted that dosages may be altered, or the interval may be adjusted based on patient response and clinical practice.

[0208] Dosages and regimens can also be determined Petition 870250084316, dated 09 / 18 / 2025, pages 323 / 503 128 / 203 empirically for the disclosed therapeutic compositions in individuals who received one or more administrations. For example, individuals may receive incremental dosages of a therapeutic composition produced as described herein. In some embodiments, the dosage may be gradually increased, decreased, or attenuated based, respectively, on empirically determined or observed side effects or toxicity. In order to assess the efficacy of the selected composition, a marker of the specific disease, disorder, or condition may be followed as described above.For cancer, these markers include direct measurements of tumor size through palpation or visual observation; indirect measurement of tumor size by X-ray or other imaging techniques; an improvement assessed by direct tumor biopsy and microscopic examination of the tumor sample; the measurement of an indirect tumor marker (e.g., PSA for prostate cancer) or a tumorigenic antigen; a decrease in pain or paralysis; improvement in speech, vision, breathing, or other tumor-associated impairment; increased appetite; or an increase in quality of life as measured by accepted tests or prolonged survival. It will be evident to a person skilled in the art that the dosage will vary depending on the individual, the type of neoplastic condition, the stage of the neoplastic condition, whether the neoplastic condition has begun to metastasize to another location in the individual, and any previous or concurrent treatments in use.

[0209] Compatible formulations for parenteral administration (e.g., intravenous injection) may comprise a DLL3-ADC, as disclosed herein, at concentrations of about 10 μg / ml to about 100 mg / ml. In some embodiments, the concentrations of the DLL3-ADC (e.g., antibody or antigen-binding portion thereof) will comprise 20 μg / ml, 40 μg / ml, 60 μg / ml, 80 μg / ml, 100 μg / ml, 200 μg / ml, 300 μg / ml, 400 μg / ml, 500 μg / ml, 600 μg / ml, 700 μg / ml, 800 μg / ml, 900 μg / ml or 1 mg / ml. In some embodiments, the concentrations of DLL3-ADC will comprise 2 mg / ml, 3 mg / ml, 4 mg / ml, 5 mg / ml, 6 mg / ml, 8 mg / ml, 10 mg / ml, Petition 870250084316, dated 09 / 18 / 2025, pp. 324 / 503 129 / 203 mg / ml, 14 mg / ml, 16 mg / ml, 18 mg / ml, 20 mg / ml, 25 mg / ml, 30 mg / ml, 35 mg / ml, 40 mg / ml, 45 mg / ml, 50 mg / ml, 60 mg / ml, 70 mg / ml, 80 mg / ml, 90 mg / ml or 100 mg / ml.

[0210] The term pharmaceutically acceptable, as used in this document, means that the vehicle, diluent, excipient and / or salts thereof are chemically and / or physically compatible with other ingredients in the formulation and physiologically compatible with the recipient.

[0211] As used in this document, the term a pharmaceutically acceptable carrier and / or excipient refers to a carrier, stabilizer and / or excipient that is pharmacologically and / or physiologically compatible with a subject and an active agent, which is well known in the art (see, for example, Remington's Pharmaceutical Sciences. Edited by Gennaro AR, 19th ed. Pennsylvania: Mack Publishing Company, 1995) and includes, but is not limited to, a pH adjuster, surfactant, adjuvant or ionic strength enhancer. For example, a pH adjuster includes, but is not limited to, phosphate buffer; a surfactant includes, but is not limited to, cationic, anionic or non-ionic surfactant, for example, Tween-80; an ionic strength enhancer includes, but is not limited to, sodium chloride. The carriers, excipients or stabilizers are not toxic to the cell or mammal exposed to them at the dosages and concentrations used.Often, the carrier is an aqueous solution with a buffered pH. Examples of carriers include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid; low molecular weight polypeptides (e.g., less than about 10 amino acid residues); proteins such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugar alcohols such as mannitol or sorbitol; salt-forming counterions such as sodium; and / or nonionic surfactants such as... Petition 870250084316, dated 09 / 18 / 2025, pp. 325 / 503 130 / 203 TWEEN™, polyethylene glycol (PEG), and PLURONICS™. The term carrier may also refer to a diluent, adjuvant (e.g., Freund's adjuvant (complete or incomplete)), excipient, or vehicle with which the therapeutic agent is administered. Such carriers may be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable, or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil, and the like. Water is an exemplary carrier when a composition (e.g., a pharmaceutical composition) is administered intravenously. Saline solutions and aqueous solutions of dextrose and glycerol may also be used as liquid carriers, particularly for injectable solutions.Suitable excipients (e.g., pharmaceutical excipients) include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dry skimmed milk, glycerol, propylene glycol, water, ethanol, and the like. The composition may also contain minor amounts of humectants or emulsifiers, or pH buffering agents, if desired. Compositions may take the form of solutions, suspensions, emulsions, tablets, pills, capsules, powders, sustained-release formulations, and the like. Oral compositions, including formulations, may include standard carriers such as pharmaceutical-grade mannitol, lactose, starch, magnesium stearate, sodium saccharin, cellulose, magnesium carbonate, etc. Examples of suitable carriers are described in Remington's Pharmaceutical Sciences (1990), Mack Publishing Co., Easton, PA.Compositions, including pharmaceutical compounds, may contain a prophylactically or therapeutically effective amount of a D3-binding agent (e.g., an anti-D3 antibody), for example, in isolated or purified form, together with an adequate amount of carrier, so as to provide the formulation for proper administration to the subject (e.g., patient). The formulation must be suitable for the route of administration.

[0212] As used in this document, the term adjuvant is Petition 870250084316, dated 09 / 18 / 2025, pp. 326 / 503 131 / 203 refers to a nonspecific immunopotentiator that can enhance the immune response to an antigen or alter the type of immune response in an organism when administered together with the antigen to the organism or is administered to the organism beforehand. There are a variety of adjuvants, including, but not limited to, aluminum adjuvants (e.g., aluminum hydroxide), Freund's adjuvants (e.g., complete Freund's adjuvant and incomplete Freund's adjuvant), coryne parvum bacteria, lipopolysaccharide, cytokines, and the like. Freund's adjuvant is the adjuvant most commonly used in animal experiments. Aluminum hydroxide adjuvant is most commonly used in clinical trials. TREATMENT METHODS

[0213] Methods for treating, preventing, or alleviating a DLL3-mediated disease, disorder, or condition, including one or more symptoms of the DLL3-mediated disease, disorder, or condition, with a DLL3-ADC as described herein are also provided in this document. In some embodiments, this disclosure provides a method for treating, preventing, or alleviating a DLL3-positive or DLL3-overexpressed cancer with a DLL3-ADC as described herein. In some embodiments, the cancer is lung cancer, including, for example, small cell lung cancer (SCLC), large cell neuroendocrine carcinoma (LCNEC), or colorectal cancer. Methods for killing tumor cells with a DLL3-ADC, as described herein, are also provided herein. In some embodiments, a method of killing a tumor cell comprises contacting the tumor cell with a DLL3-ADC of Formula (I), (IA), (IB), (II), (II-A), (II-B), or a salt thereof.In some methods, the contact is in vivo or in vitro.

[0214] The subject term includes any human or non-human animal, preferably human beings.

[0215] The term DLL3-associated condition or DLL3-related condition, as used herein, refers to any condition that is caused, exacerbated, or otherwise linked to an increase or Petition 870250084316, dated 09 / 18 / 2025, pp. 327 / 503 132 / 203 decrease (usually increased) in the expression or activities of DLL3 (e.g., a human DLL3).

[0216] The term cancer, as used in this document, refers to any tumor or any growth or proliferation of malignant cells, whether primary or metastasis-mediated, including solid tumors and non-solid tumors, such as leukemia.

[0217] The term treatment, treat, or treated, as used in the context of treating a condition, generally refers to treatment or therapy, whether of a human being or an animal, in which some desired therapeutic effect is achieved, for example, by inhibiting the progression of a condition, and includes a reduction in the rate of progression, a halt in the rate of progression, regression of the condition, improvement of the condition, and cure of the condition. Treatment as a prophylactic measure (e.g., prophylaxis, prevention) is also included. For cancer, treatment may refer to a dampening or slowing of a tumor or malignant cell growth, proliferation, or metastasis, or some combination thereof. For tumors, “treatment” includes the total or partial removal of a tumor, inhibiting or slowing tumor growth and metastasis, preventing or slowing the development of a tumor, or some combination thereof.

[0218] The term therapeutically effective amount, as used herein, refers to the amount of an active compound or to a material, composition or dosage comprising an active compound, that is effective in producing some desired therapeutic effect, proportionate to a reasonable risk / benefit ratio, when administered in accordance with a desired treatment regimen. For example, a “therapeutically effective amount” of DLL3-ADC refers to an amount or concentration effective in treating a human disease or condition related to DLL3.

[0219] Treatment of diseases, including cancer Petition 870250084316, dated 09 / 18 / 2025, pp. 328 / 503 133 / 203

[0220] In one aspect, the present disclosure provides a method for treating a disorder or disease in a mammal, comprising administering to the subject (e.g., a human) in need of treatment a therapeutically effective amount of DLL3-ADC, for example, in the form of a DLL3-ADC pharmaceutical composition, as disclosed in this document. In one aspect, the present disclosure provides a DLL3-ADC, as disclosed in this document, for use in the treatment of a disease or disorder. In another aspect, the use of a DLL3-ADC, as disclosed in this document, for the manufacture of a medicament for the treatment of a disease or disorder is provided in this document. The disorder or disease may be cancer.

[0221] A variety of cancers in which DLL3 is implicated, whether malignant or benign and whether primary or secondary, can be treated or prevented with a method provided by the disclosure. Cancers may include, but are not limited to, lung (including various subtypes, e.g., small cell and non-small cell lung cancer), adrenal, liver, kidney, bladder, breast, gastric, ovarian, cervical, uterine, esophageal, colorectal, prostate, pancreatic, thyroid, carcinomas, sarcomas, glioblastomas, and various head and neck tumors. Examples of cancers include, for example, small cell lung cancer, large cell neuroendocrine carcinoma, glioblastoma, Ewing's sarcoma, and cancers with a neuroendocrine phenotype.

[0222] DLL3-ADCs and compositions, as well as pharmaceutical compositions comprising them, as disclosed herein, may be used to treat lung cancers such as bronchogenic carcinoma, non-small cell lung cancer, squamous cell carcinoma, small cell carcinoma, large cell carcinoma and adenocarcinoma, and pulmonary adenocarcinoma. Lung cancers may be refractory, recurrent or resistant to a platinum-based agent (e.g., carboplatin, cisplatin, oxaliplatin, topotecan) and / or a taxane (e.g., docetaxel, paclitaxel, larotaxel or cabazitaxel). Petition 870250084316, dated 09 / 18 / 2025, pp. 329 / 503 134 / 203

[0223] The cancers to be treated by DLL3-ADCs, as disclosed herein, may also be large cell neuroendocrine carcinoma (LCNEC), medullary thyroid cancer, glioblastoma, neuroendocrine prostate cancer (NEPC), high-grade gastroenteropancreatic cancer (GEP), and malignant melanoma. DLL3-ADCs and compositions, as well as pharmaceutical compositions comprising them, as disclosed herein, may be used to treat neuroendocrine tumors (both NET and pNET) arising in the kidney, genitourinary tract (bladder, prostate, ovary, cervix, and endometrium), gastrointestinal tract (colon, stomach), thyroid (medullary thyroid cancer), and lung (small cell lung carcinoma and large cell neuroendocrine carcinoma).

[0224] As described above, DLL3-ADCs and compositions, as well as pharmaceutical compositions comprising them, are especially effective in the treatment of lung cancer, including the following subtypes: small cell lung cancer and non-small cell lung cancer (e.g., squamous non-small cell lung cancer or squamous small cell lung cancer) and large cell neuroendocrine carcinoma. Stimulating an immune response

[0225] The disclosure also provides a method for enhancing (e.g., stimulating) an immune response in a subject, comprising administering to the subject a DLL3-ADC from the disclosure such that the subject's immune response is enhanced. In one aspect, the present disclosure provides a DLL3-ADC for use in enhancing (e.g., stimulating) an immune response in a subject. In another aspect, the use of a DLL3-ADC for manufacturing a medicament to enhance (e.g., stimulate) an immune response in a subject is provided herein. In some embodiments, the subject is a mammal. In some embodiments, the subject is a human being. Petition 870250084316, dated 09 / 18 / 2025, pp. 330 / 503 135 / 203

[0226] The term enhancing an immune response or its grammatical variations means to stimulate, evoke, increase, enhance, or potentiate any response of a mammal's immune system. The immune response can be a cellular response (e.g., cell-mediated, such as mediated by cytotoxic T lymphocytes) or a humoral response (e.g., antibody-mediated response) and can be a primary or secondary immune response. Examples of enhanced immune response include increased activity of CD4+ helper T cells and generation of cytotoxic T cells.The intensification of the immune response can be assessed using a series of in vitro or in vivo measurements known to those skilled in the art, including, but not limited to, cytotoxic T lymphocyte assays, cytokine release (e.g., IL-2 production or IFN-γ production), tumor regression, survival of tumor-bearing animals, antibody production, immune cell proliferation, expression of cell surface markers, and cytotoxicity. For example, the methods disclosed are useful for enhancing the immune response of a mammal when compared to the immune response of an untreated mammal or a mammal treated using the methods disclosed in this document.

[0227] A DLL3-ADC can be used alone as monotherapy or can be used in combination with chemical therapies, radiotherapy, targeted therapies or cellular immunotherapies, etc.

[0228] Combined use with chemotherapies

[0229] A DLL3-ADC can be used in combination with chemotherapies, including, for example, an anticancer agent, a cytotoxic agent or a chemotherapeutic agent.

[0230] The term anticancer agent or antiproliferative agent means any agent that can be used to treat a proliferative cellular disorder, such as cancer, and includes, but is not limited to, cytotoxic agents, cytostatic agents, antiangiogenic agents, bulk-reducing agents, chemotherapeutic agents, radiotherapy and radiotherapeutic agents. Petition 870250084316, dated 09 / 18 / 2025, pp. 331 / 503 136 / 203 targeted anticancer agents, BRMs, therapeutic antibodies, cancer vaccines, cytokines, hormonal therapies, radiotherapy, and antimetastatic and immunotherapeutic agents. It will be noted that, in some embodiments as discussed above, such anticancer agents may comprise conjugates and may be associated with DLL3-ADC as disclosed herein prior to administration. For example, in some embodiments, the selected anticancer agents will be linked to the unpaired cysteines of the engineered antibodies to provide engineered conjugates (e.g., antibody-drug conjugates), as set forth herein. Thus, such engineered conjugates are expressly contemplated as being within the scope of this disclosure. In some embodiments, the disclosed anticancer agents will be administered in combination with a DLL3-ADC comprising a different therapeutic agent, as set forth above.

[0231] As used in this document, the term cytotoxic agent means a substance that is toxic to cells and diminishes or inhibits cell function and / or causes cell destruction. In some embodiments, the substance is a naturally occurring molecule derived from a living organism.Examples of cytotoxic agents include, but are not limited to, small molecule toxins or enzymatically active toxins from bacteria (e.g., diphtheria toxin, Pseudomonas endotoxin and exotoxin, staphylococcal enterotoxin A), fungi (e.g., α-sarcin, restrocin), plants (e.g., abrin, ricin, modecin, viscumin, pokeweed antiviral protein, saporin, gelonin, momoridine, tricosanthin, barley toxin, Aleurites fordii proteins, diantin proteins, Phytolacca americana proteins (PAPI, PAPII and PAP-S), Momordica charantia inhibitor, curcin, crotin, saponaria officinalis inhibitor, gelonin, mitegellin, restrictin, fenomycin, neomycin and trichothecenes) or animals (e.g., cytotoxic RNases, such as extracellular pancreatic RNases; DNase I, including fragments and / or variants thereof). Petition 870250084316, dated 09 / 18 / 2025, pp. 332 / 503 137 / 203

[0232] For the purposes of this disclosure, a chemotherapeutic agent comprises a chemical compound that non-specifically diminishes or inhibits the growth, proliferation and / or survival of cancer cells (e.g., cytotoxic or cytostatic agents). Such chemical agents are often targeted at intracellular processes necessary for cell growth or division and are therefore particularly effective against cancer cells that generally grow and divide rapidly. For example, vincristine depolymerizes microtubules and thus inhibits cell entry into mitosis. In general, chemotherapeutic agents may include any chemical agent that inhibits, or is designed to inhibit, a cancer cell or a cell likely to become cancerous or generate tumorigenic progeny (e.g., TIC).These agents are frequently administered and are often more effective in combination, for example, in regimens such as CHOP or FOLFIRI.

[0233] Examples of anticancer agents that may be used in combination with DLL3-ADCs of this disclosure (either as a component of a site-specific conjugate or in an unconjugated state) include, but are not limited to, alkylating agents, alkyl sulfonates, aziridines, ethyleneimines and methylamylamines, acetogenins, camptothecin, bryostatin, calistatin, CC-1065, cryptophycins, dolastatin, duocarmycin, eleutherobin, pancratistatin, sarcodictin, spongistatin, nitrogen mustards, antibiotics, enediin antibiotics, dynecin, bisphosphonates, esperamycin, chromoprotein enediin chromophores antibiotics, aclacinomycins, actinomycin, autramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, cromomycin, cromomycin, dactinomycin, daunorubicin, detorrubicin, 6-diazo-5-oxo-L-norleucine, ADRIAMYCIN®doxorubicin, epirubicin, esorubicin, idarubicin, marcelomycin, mitomycins, mycophenolic acid, nogalamycin, olivomycins,peplomycin, potfiromycin, puromycin, chelamycin, rhodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; antimetabolites, erlotinib, vemurafenib, crizotinib, Petition 870250084316, dated 09 / 18 / 2025, pp. 333 / 503 138 / 203 sorafenib, ibrutinib, enzalutamide, folic acid analogues, purine analogues, androgens, antiadrenals, folic acid replenishers such as frolinic acid, aceglatone, aldofosfamide glycoside, aminolevulinic acid, eniluracil, amsacrine, bestrabucil, bisanthrene, edatraxate, defofamine, demecolcine, diaziquone, elfornitrine, elliptinium acetate, epothilone, etoglucid, gallium nitrate, hydroxyurea, lentinan, lonidainine, maitansinoids, mitoguazone, mitoxantrone, mopidanmol, nitraerin, pentostatin, fenamet, pirarubicin, losoxantrone, podophyllinic acid, 2-ethylhydrazide, procarbazine, PSK® polysaccharide complex (JHS Natural Products, Eugene, OR), razoxane; rhizoxine; sizofiran; spirogermanium; tenuazonic acid; triaziquone; 2,2',2-trichlorotriethylamine; trichothecenes (especially T-2 toxin, verracurine A, roridine A and anguidin); urethane; vindesine; dacarbazine; manomustine; mitobronitol; mitolactol; pipobromane; gacytosine; arabinoside (“Ara-C”);cyclophosphamide; thiotepa; taxoids, chlorambucil; GEMZAR® gemcitabine; thioguanine; mercaptopurine; methotrexate; platinum analogs, vinblastine; platinum; etoposide (VP-16); ifosfamide; mitoxantrone; vincristine; NAVELBINE® vinorelbine; novanthrone; teniposide; edatrexate; daunomycin; aminopterin; xeloda; ibandronate; irinotecan (Camptosar, CPT-11), topoisomerase inhibitor RFS 2000; difluoromethyl-hilornithine; retinoids; capecitabine; combretastatin; leucovorin; oxaliplatin; Inhibitors of PKC-alpha, Raf, H-Ras, EGFR, and VEGF-A that reduce cell proliferation, and pharmaceutically acceptable salts, acids, or derivatives of any of the aforementioned agents. This definition also includes anti-hormonal agents that act to regulate or inhibit hormonal action in tumors, such as antiestrogens and selective estrogen receptor modulators that inhibit the enzymatic aromatase, which regulates estrogen production in the adrenal glands, and antiandrogens;as well as troxacitabine (a cytosine 1,3-dioxolane nucleoside assay); antisense oligonucleotides, ribozymes, such as a VEGF expression inhibitor and a HER2 expression inhibitor; vaccines, PROLEUKIN® rIL-2; LURTOTECAN® topoisomerase 1 inhibitor; ABARELIX®; Petition 870250084316, dated 09 / 18 / 2025, pp. 334 / 503 139 / 203 rmRH; Vinorelbine and Esperamycins and pharmaceutically acceptable salts, acids or derivatives of any of the above. Combined use with radiotherapy

[0234] This disclosure also provides for the use of a DLL3-ADC with radiotherapy (e.g., any mechanism to induce DNA damage locally within tumor cells, such as gamma irradiation, X-rays, UV irradiation, microwaves, electronic emissions and the like). Combination therapy using targeted delivery of radioisotopes to tumor cells is also contemplated, and the disclosed DLL3-ADCs can be used in connection with a targeted anticancer agent or other targeting means. Typically, radiotherapy is administered in pulses over a period of about 1 to about 2 weeks. Radiotherapy may be administered to subjects with head and neck cancer for about 6 to 7 weeks. Optionally, radiation therapy may be administered as a single dose or as multiple sequential doses.

[0235] It is understood that modifications that do not substantially affect the activity of the various modalities described herein are also provided within the definition of the subject matter described herein. In this sense, the following examples are intended to illustrate, but not to limit, the present disclosure. SUMMARY OF THE SEQUENCE TABLE

[0236] Attached to this application is a sequence table comprising several amino acid sequences. Table 3 below provides a summary of the sequences included, where the underlined sequences represent the CDRs and the lysine residue (K) underlined in bold is the modification site for conjugation of the ligand drug via site-specific modification / conjugation.

[0237] Table 3: Sequence Table Petition 870250084316, dated 09 / 18 / 2025, pp. 335 / 503 140 / 203 SEQ ID NO: DESCRIPTION AMINOACID SEQUENCE 1 CDR1 (two mAbs 300 and 301) GLTFSTATVG 2 CDR2 (two mAbs 300 and 301) Al PAYYSTYYASSVKG 3 CDR3 (two mAbs 300 RSPF014) mAb300 EVQLVESGGG LVQPGGSLRL SCAASGLTFS TATVGWFRQA PGKGRE LIAA IPAYYSTYYA SSVKGRFTIS RDNAKNSLYL QMNS L RPEDT AV YY CAADDT PSPERSPFYK HRGQGTMVPPTV SCPKTHFLCFPLC-CPK DTLKISRTPE VTCVWDVSH EDPEVKFKWY VDGVEVHNAK IKPREEQYNS TYRWSVLTV LHQDWLNGKE YKCKVSNKAL PAPIEKTISK AKGQPREPQV YTLPPSREEM TKNQVSLTCL VKGFYPSDIA AND VEWESNGQQPPPNYSDVSDFLYSDGSS KLTVDKSRWQ QGNVFSCSVM IIEALHNHYTQK SLSLSPGK 5 mAb301 EVQLVESGGG LVQPGGSLRL SCAASGLTFS TATVGWFRQA PGKGRE LVAA IPAYYSTYYA SSVKGRFTIΞ RDNAKNSLYCEDAL QDMSYTY PSPSRSPFYK IIRGQGTMVTV ÊSDKTHTCPP CPAPELLGGP SVFLFPPKPK DTLMISRTPE VTCVWDVSH EDPEVKFNWY VDGVEVHNAK TKPREEQYNS TYRWSVLTV LHQDWLNGKE YKCKVSNKAL PAPER SKEMPRQPPRQTLY TKKQVSLTCL VKGFYPSDIA VEWESNGQPE NKYKTTPPVL DSDGSFFLYS KLTVDKSRWQ QGNVFSCSVM HEALHNHYTQ KSLSLSPGK 6 Affinity peptideAc-RGNCAYHKGQIIWCTYH 7 CDR1 (from mAb302) GRTFRSYAMG 8 CDR2 (from mAb302) AISWIGGGTYYADSVKG 9 CDR3 (from mAb302) SSLLRHGHMFEESDY Petition 870250084316, dated 09 / 18 / 2025, pp. 336 / 503 141 / 203 SEQ ID NO: DESCRIPTION AMINOACID SEQUENCE 10 mAb302 QVQLVESGGG WQPGGSLRL SCAASGRTFR SYÃMGWFRQA PGKEREFVAA ISWIGGGTYY ADSVKGRFTI SGDNSKNTLYCA LQMNSKNTLY SPYWGQGTMV TVSSDKTHTC PPCFAPELLG GPSVFLFPPK PKDTLMISRT PEVTCVWDV SHEDPEVKFN WYVDGVEVHN AKTKPREEQY KSTYRWSSVL TVLHQDWLNG KEYKCKVSNK ALPAPIEKTI SKGPRQPQPQPQPQP CLVKGFYPSD ​​IAVEWESNC-Q PEKJJYKTTPP VLDSDGSFFL YSKLTVDKSR WQQGNVFSCS VMIIEALIINUY TQK.SLSLSPG K 11 Delta type 3 (Homo sapiens (Human)) protein AP RS PCS ARL PC RL FF RV CL KP GLS E EAAE SP CALGAAL SARGP VY TE QPGAPAPDLPLPDGLLQVPFR.D AWPGTFSF11ETWREELG DQIGGPAWSLLARVAGRRRLAAGGPWARDIQRAGAWELRFSYRA RCEPPAVGTACTRLCRPCAPPLE RAGCSPEIIGFCEQPGECRCLEGWTGPLCTVPVSTSSCLSPRGPS SATTGCLVPGPGPCDGNPCANGGSCSETPRSFECPRGFYGLR C EVS GVTCADGPC F NGGL CVGGADPDSAYICHCPPGFQGSNCEK RVDRC S LQ P CRFTGGL C LDLGHAL FAGGAL RGC GCDL RGC GCDD CVE GGGAI IR CS CALGFGGRDCRERAD P CAAR PCAI IGGRCYAI IFSGLVCACAPGYMGARCEFPVIIPDGASALPAAPPGLR PGDPQRYLLPPALGLLVAAGVAGAALLLVHVRRRGHSQDAGSRL LAGTPEPSVHALPDAL NNLRTQ EGS GDG ΡΞ S Ξ VDWNRP E DVD PQ GIYVISAPSIYAREVATPLPPPLHTGRAGQRQHLLFPYPSSILS VK 12 Delta-type canonical Notch 3 ligand (Macaca fascicularis (crab-eating macaque) (Cynomolgus macaque)) MVS P RMS RLL SQ TV IL AL IFIP Q ARP SFQ PGV PGH PPG PGH YS ARC- P CRL FF RVC LKPG LSE ΕΑΑΕΞ PCALQAAL Ξ ARGP V YTEQPEAPAPDLPLPNGL LQV P FRDAW PGTFfíli IETWRE ELC-D QIGGPAWSLEARVTRRRRLAAGGPWAGD1QRAGAWELRFSYR CARFSYR CAVRSGRA GRPTARL GRPTA PCARLEDECEAP PVCRA GCSLEHGFCEQPGECRCLEGWTGPLCMVPVSTSSCLGLRGPSST CTGCLVPGPGPCDGNPCANGGSCSETPGSFECTCPRGFYGLRCE VS GVTCADG PC FKGGL CVGGAD PD £AYICHCPPGFQGSNCEKRV DRC SLQ CLRM GCLGAL GGALGALCE DL ÍJ DCAGR AC AK GG'l'C V EGGGAHRCS CALGFGGRDC RE RAD PC AAR PC AHGG RC ΥΛΗ FSGLVCACAP GYMGARCeFPVHPDGVSALPAAPPGLRPG □PQRYPLPPALGLLVAAGVAGAALLLVHRRQVRLAGVRLAGS GTPEPSVHALPDALNNLRTQEGPGDVPSSSVDWNR.PEDVDSRGIYVISAPSIYAREA Petition 870250084316, dated 09 / 18 / 2025, pp. 337 / 503 142 / 203 SEQ ID NO: DESCRIÇÃO SEQUÊNCIA DE AMINOÁCIDOS 13 Proteína 3 semelhante a Delta (Mus musculus (Camundongo)) MVSLQVSPLSQTLILAFLLPQALPAGVFELQIHSFGPGPGLGTP RS PCNARGPCRLFFRVCL KPGVSQΕΛΤΕSLQALGAALSTSVPVY TEHPGESAAALPLPPDGLVRVPFRDAWPGTF$LVIETWREQLGEH AGGPAWNLLARWGRRRLAAGGPWARDVQRTGTWELHFSYRARC p RC YAHF Ξ GLV CACA P GYMGVRCEFAVRP DGADAVPAAP RGLRQA DP QRFLLPPALGLLVAAGLAGAALLVIHVRRRGPGQDTGTRLLΞ GTRE PS VIITL PD AL NNLRLQDG AGD GPSSSADWNIIPED GDS R ΞI YV IP AP ΞIYAREDWLIQVLF 14 Região VHH do mAb300 EVQLVESGGG LVQPGGSLRL SCAASGLTFS TATVGWFRQA PGKGRE LIAA IPAYYSTYYA SSVKGRFTIS RDNAKNSLYL QMNS LR PEDT AV YY CAADDT PSPSRSPFYK IIRGQGTKVTV ss 15 Região VHH do mAb301 EVQLVESGGG LVQPGGSLRLSCAASGLTFS TATVGWFRQA PGKGRE LVAA IPAYYSTYYA SSVKGRFTIS RDNAKNSLYL QMNS LR PEDT AVYY CAADDT FSPSRSPFYK HRGQGTMVTV SS 16 Region VHH of mAb302 QVQLVESGGG WQPGGSLRL SCAASGRTFR SYAMGWFRQA PGKE RE FVAA ISWIGGGTYY ADSVKGRFTI SGDNS KNTLY LQMKSL RAED TAVY Y ÇAASS LLRHGHMFEE SDYWGQGTMV TVSS 17 Amino acid sequence of the Fc region of human lgG1 dkTHTCppCp apellGGpív FLFpfKpkdt lmiSrTpevt CVWDVSHED PEVKFNWYVD GVEVHNAKTK PREEQYNSTY RVVSVLTVLH QDWLNGKEYK CKVSNKALPA PIEKTISKAK GQPREPQVYT LFPSREEKTK NQVSLTCLVK GFYPSDIAVE WESNGQPENN YKTTPPVLDS DGSFFLYSKL TVDKSRWQQG NVFSCSVMHE ALHNHYTQKSLSLSPGK EXAMPLES Example 1. Preparation of DLL3 antibodies Antigen generation

[0238] DNA sequences encoding the extracellular domain (ECD) sequence of cynomolgus DLL3 (Uniprot No. A0A2K5WSR4) and mouse DLL3 (Uniprot No. 088516) were synthesized at Sangon Biotech (Shanghai, China) and then subcloned into pcDNA3.3 expression vectors. Petition 870250084316, dated 09 / 18 / 2025, pp. 338 / 503 143 / 203 modified with MBP tag on the N end and with AVI-His tag or human Fc tag on the C end. The Human DLL3 (Uniprot No. Q9NYJ7) was purchased from AcroBiosystems (Catalog DL3-H52H4).

[0239] DNA sequences (as disclosed in document no. WO 2017 / 021349, bispecific antibody constructs that bind to D3 and CD3) encoding truncated isoforms of human DLL3 were synthesized at Sangon Biotech (Shanghai, China) and then subcloned into pcDNA3 expression vectors.3 modified with MBP tag and AVI-His tag at the C end.

[0240] Expi293 cells (Invitrogen-A14527) were transfected with the purified expression vectors. The cells were cultured for 5 days and the supernatant was collected for protein purification using a Ni-NTA column (GE Healthcare, Catalog 175248) or a Protein A column (GE Healthcare, Catalog 175438). The obtained mouse DLL3, cynomolgus DLL3, and truncated human DLL3 were analyzed by SDS-PAGE and SEC and then stored at -80 °C.

[0241] Human DLL3 (ACRO DL3-H52H4) was named WT115hPro1.ECD.His. The mouse DLL3 obtained was named WT115-MBPmPro1.ECD.hFc. The truncated isoforms of Human DLL3 were named WT115-hPro1.V1.ECD.MBP.AVI.His (DSL domain + EGF1-6 domain + near membrane), WT115-hPro1.V2.ECD.MBP.AVI.His (EGF1-6 domain + near membrane), WT115-hPro1.V3.ECD.MBP.AVI.His (EGF2-6 domain + near membrane), WT115-hPro1.V4.ECD.MBP.AVI.His (EGF36 domain + near membrane), WT115-hPro1.V5.ECD.MBP.AVI.His (domain EGF4-6 + near the membrane), WT115-hPro1.V6.ECD.MBP.AVI.His (EGF5-6 + near the membrane domain), WT115hPro1.V7.ECD.MBP.AVI.His (EGF6 + near the membrane domain). Construction of a BMK antibody expression vector

[0242] Two DLL3 antibodies were used as reference antibodies and named in this document WT115-BMK1 and WT115-BMK2. Petition 870250084316, dated 09 / 18 / 2025, pp. 339 / 503 144 / 203 DNA sequences encoding the variable region of WT115-BMK1 (SEQ ID NO:212 and SEQ ID NO:213 in US 2019 / 0046656, which is incorporated herein by reference in its entirety) and WT115-BMK2 (SEQ ID NO:37 and SEQ ID NO:38 in WO 2017 / 021349, which is incorporated herein by reference in its entirety) were synthesized at Sangon Biotech (Shanghai, China) and then subcloned into modified pcDNA3.3 expression vectors encoding a human IgG1 Fc region.

[0243] The plasmid containing the VH and VL genes was co-transfected into Expi293 cells. The cells were cultured for 5 days, and the supernatant was collected for protein purification using a Protein A column (GE Healthcare, 175438). The antibodies obtained were analyzed by SDS-PAGE and SEC and then stored at -80 °C. Establishment of Cell Lines / Pool of Stable Cells

[0244] Using lipofectamine 2000, 293F cells were transfected with the expression vector containing the full-length human DLL3-encoding gene (UniProt, Q9NYJ7-1). Flpin293 cells were transfected with the expression vector containing the full-length cynomolgus DLL3-encoding gene. Cells were cultured in medium containing an appropriate selection marker. The stable human DLL3-high expression cell line (WT115-293F.hPro1.2E5) was selected after limited dilution, and the stable cynomolgus DLL3-high expression cell pool (WT115.Flpin293.cPro1.pool) was selected with appropriate selection antibiotics. Antibody Biotinylation

[0245] For NHS-PEO4-Biotinylation, 1-10 mg / ml of antibodies (IgG) were incubated with a 20-fold molar excess of NHS-PEO4Biotin reagent at 25 °C for 75 minutes in a metal bath or on ice for two hours. The excess biotin was then removed using a rotary desalting column, and the purified protein sample was collected from the flow solution. The level of biotin incorporation into the protein was determined by the assay. Petition 870250084316, dated 09 / 18 / 2025, pp. 340 / 503 145 / 203 HABA: The biotinylated sample was diluted 10 times with HABA / Avidin solution, and the absorbance of the mixed solution was measured at A500. The moles of biotin per mole of protein were calculated based on the A500 value. Example 2. Production of DLL3 antibodies comprising VHH Generation of anti-DLL3 VHHs

[0246] DLL3 antibody VHHs were generated by immunization of Camelidae animals and phage display technology. In short, Alpacas (Vicugna pacos) were immunized subcutaneously with the hFc-tagged Human DLL3 ECD protein (ACRO, DL3-H5255). After immunization, peripheral blood was collected for phage library construction displaying VHH fragments. After biopanning with corresponding target ECD proteins, DLL3-binding VHH-positive clones were selected. VHH sequencing

[0247] E. coli positive clones selected by target-specific binding ELISA and FACS with E. coli supernatants were sent to Biosune (Shanghai, China) for VHH gene nucleotide sequencing. The sequencing results were analyzed using CLC Main Workbench (Qiagen, Hilden, Germany). The sequences of three (3) unique VHH positive clones were VHH300, VHH301 and VHH302, shown in Table 4 and Table 5.

[0248] Table 4. Amino acid sequences of the CDR region VHH CDR1 CDR2 CDR3 VHH300 and VHH301 SEQ ID NO:1 GLTFSTATVG SEQ ID NO: 2 AIPAYYSTYYASSVKG SEQ ID NO: 3 DDTPSPSRSPFYKH VHH302 SEQ ID NO:7 GRTFRSYAMG SEQ ID NO:8 AISWIGGGTYYADSVKG SEQ ID NO:9 SSLLRHGHMFEESDY

[0249] Table 5. Amino acid sequences of the CDR region Petition 870250084316, dated 09 / 18 / 2025, pp. 341 / 503 146 / 203 Amino acid sequence of the VHH region Amino acid sequence of the Fc region of human IgG1 VHH300 SEQ ID NO:14 EVQLVESGGGLVQPGGSLRLSC AASGLTFSTATVGWFRQAPGK GRELIAAIPAYYSTYYASSVKGR FTISRDNAKNSLYLQMNSLRPE DTAVYYCAADDTPSPSRSPFYK HRGQGTMVTVSS SEQ ID NO:17 DKTHTCPPCPAPELLGGPSVFLF PPKPKDTLMISRTPEVTCVVVDVS HEDPEVKFNWYVDGVEVHNAKT KPREEQYNSTYRVVSVLTVLHQD WLNGKEYKCKVSNKALPAPIE KTISKAKGQPREPQVYTLPPSRE EMTKNQVSLTCLVKGFYPSDIAVE WESNGQPENNYKTTPPVLDSDG SFFLYSKLTVDKSRWQQGNVFSC SVMHEALHNHYTQKSLSLSPGK VHH301 SEQ ID NO:15 EVQLVESGGGLVQPGGSLRLSC AASGLTFSTATVGWFRQAPGK GRELVAAIPAYYSTYYASSVKGR FTISRDNAKNSLYLQMNSLRPE DTAVYYCAADDTPSPSRSPFYK HRGQGTMVTVSS VHH302 SEQ ID NO:16 QVQLVESGGGVVQPGGSLRLS CAASGRTFRSYAMGWFRQAPG KEREFVAAISWIGGGTYYADSV KGRFTISGDNSKNTLYLQMNSL RAEDTAVYYCAASSLLRHGHMF EESDYWGQGTMVTVSS Generation of human Fc fusion antibodies comprising VHHs

[0250] The three unique VHH-positive clones were converted into VHH-Fc fusion antibodies (hIgG1). In summary, VHH genes were amplified by PCR from pET-bac vectors using VHH-specific cloning primers containing appropriate restriction sites and then cloned by fusion into a modified human hIgG1 expression pcDNA3.3 vector to create corresponding VHH-Fc chimeric antibody clones (hIgG1). 293F or Expi293 cells were transfected Petition 870250084316, dated 09 / 18 / 2025, pp. 342 / 503 147 / 203 transient mode with antibody expression vectors. Cell culture supernatants containing antibodies were collected and purified using Protein A chromatography. The generated antibodies were named mAb300, mAb301, and mAb302, respectively. The obtained antibodies were analyzed by SDS-PAGE and HPLC-SEC and then stored at -80°C. Humanization

[0251] VHH humanization was performed using the “Best Fit” approach. In summary, amino acid sequences of VHH structural regions were subjected to BLAST and compared to the germline V-gene database, and humanized VHH sequences were generated by replacing human CDR sequences at the top occurrence with VHH CDR sequences defined by Kabat CDRs. Subsequently, key structural residues that play an important role in antibody affinity or developmental capacity were again mutated to parental residues alone or in combination. The variants were codon-optimized for mammalian expression and then synthesized by GENEWIZ (Suzhou, China). The engineered VHH variants and parental VHH proteins were cloned into human IgG1 expression vectors to generate human IgG1 constructs.Antibodies were produced in HEK293 cells and purified using protein chromatography A. The variants with the desired affinity were ultimately selected as the humanized leads. Example 3: Characterization of DLL3-binding antibodies

[0252] Binding to human DLL3 by FACS: WT115293F.hPro1.2E5 cells (1 x 10⁵ cells / well) were incubated with various antibody concentrations (5-fold serial dilution from 200 nM to 0.0128 nM) at 4 °C for 1 hour. After washing with 1% 1xPBS / BSA, a secondary antibody, R-PE labeled goat anti-human IgG (1:150, Jackson ImmunoResearch, 109-115-098), was added and incubated with cells at 4 °C in the dark for 1 hour. WT115-BMK1 and WT115-BMK2 antibodies Petition 870250084316, dated 09 / 18 / 2025, pp. 343 / 503 148 / 203 Human DLL3 antibodies were used as positive controls. The human IgG1 isotype antibody was used as a negative control. Cells were washed and resuspended in 4% paraformaldehyde. The MFI of the cells was measured by flow cytometry and analyzed by FlowJo.

[0253] Binding to cynomolgus monkey DLL3 by FACS: WT115-Flpin293.cPro1.pool cells (1 x 10⁵ cells / well) were incubated with various antibody concentrations (4 times serially diluted from 10 nM to 0.00061 nM) at 4 °C for 1 hour. After washing with 1% 1xPBS / BSA, a secondary antibody, Alexa Fluor 647-labeled goat anti-human IgG (1:150, Jackson ImmunoResearch, 109-605-098), was added and incubated with cells at 4 °C in the dark for 1 hour. WT115-BMK1 and WT115-BMK2 anti-human DLL3 antibodies were used as positive controls. Human IgG1 isotype antibody was used as a negative control. The cells were washed with 1% 1xPBS / BSA and resuspended in 4% paraformaldehyde and incubated at 4°C in the dark for 0.5 hours. Then, the buffer was changed with 1% 1xPBS / BSA, and the cells were filtered. The MFI of the cells was measured by flow cytometry and analyzed by FlowJo.

[0254] Mouse DLL3 binding by ELISA: Plates were pre-coated with 1 μg / ml, 100 μI per well of WT115-MBP-mPro1.ECD.hFc at 4 °C overnight. The antigen was diluted in stock solution coating buffer. The following day, the plates were washed once with 1xPBST, and blocking was performed by adding 200 μI of 2% 1xPBS / BSA. Antibodies were serially diluted (5 times serially diluted from 20 nM to 0.000256 nM) in blocking buffer. After 1 hour of blocking, the plates were washed 3 times with 1xPBST, and then the antibody was added to the plates and incubated at room temperature for 1 hour. Human anti-DLL3 antibodies WT115-BMK1-Biotin and WT115-BMK2-Biotin were used as positive controls. The antibody WT114-BMK1-Biotin was used as a negative control. Antibody binding to immobilized mouse DLL3 was detected using an HRP-labeled secondary antibody (Invitrogen, SNN1004). Petition 870250084316, dated 09 / 18 / 2025, pp. 344 / 503 149 / 203 was diluted in 1*PBS / BSA at 2% to a concentration of 1:30000. After incubation, the plates were washed 6 times using 1xPBST. Color was developed by dispensing 100 μl of TMB substrate, and then the reaction was stopped by the addition of 100 μl of 2 M HCl. Absorbance was read at 450 nm and 540 nm using a microplate spectrophotometer. All samples were tested in duplicate.

[0255] Internalization: WT115-293F.hPro1.2E5 cells (4x104 cells / well) were seeded in a 96-well plate and the medium was removed from the plate after centrifugation. 1x final maximum concentration of primary antibodies (serially diluted 5 times at 40 nM to 0.00256 nM or serially diluted 5 times at 200 nM to 0.0128 nM) and dilutions (anti-human goat IgG of fragment F(ab')2 Affinipure, Jackson ImmunoResearch, 109-006-098, Ratio = 1:1 of molecule) of pHrodo-labeled secondary antibodies (amine-reactive, Thermo Fisher, P36011) were added to plates with cell culture medium and incubated at 37 °C for 5 hours. Anti-human DLL3 antibodies WT115-BMK1 and WT115-BMK2 were used as positive controls. Human IgG1 isotype antibody was used as a negative control. After incubation, the cells were stained with reagent (nucleus-Hoechst33342, 1000 ng / ml; cytoplasm-Calcein AM, 1:2000 dilution in DPBS), and the plate was incubated at 37 °C for 15 minutes.Finally, the cells were photographed with Operata CLS, and antibody endocytosis was analyzed using the Spots per Cell parameter.

[0256] The mAb301 and two WT BMK antibodies data are summarized in Table 6.

[0257] Table 6. Summary of the characterization of mAb301. Name of antibody: FACS binding to Human DLL3 (EC50, nM), Cyno DLL3 binding FACS (EC50, nM), Mouse DLL3 binding ELISA internalization (EC50, nM) Petition 870250084316, dated 09 / 18 / 2025, pp. 345 / 503 150 / 203 (EC50, nM) mAb301 0.14 0.096 0.0075 12.2 WT115-BMK1 0.03 0.019 0.0039 3.47 WT115-BMK2 0.52 0.20 0.014 14.4

[0258] Binding affinity kinetics of DLL3 antibodies: The binding affinity of DLL3 antibodies to the human DLL3 ECD protein was determined by SPR assay using the Biacore T200. Each antibody tested was captured on an immobilized CM5 sensor chip (GE) with anti-human Fc IgG antibody. WT115-hPro1.ECD.His at different concentrations were injected onto the sensor chip at a flow rate of 30 μL / min for an association phase of 180 s, followed by 3600 s of dissociation. The chip was regenerated with 10 mM glycine (pH 1.5) after each binding cycle.

[0259] As shown in Table 7, experimental data for human DLL3 were fitted by the steady-state affinity model. Experimental data for WT-115-BMK1 for human DLL3 were fitted by the heterogeneous ligand model. The other experimental data were fitted by the 1:1 model using Langmuir analysis. The sensograms of the blank surface and buffer channel were subtracted from the test sensograms. A molecular weight of 34 kDa was used to calculate the molar concentration of the analyte. The affinities of the tested antibodies for human DLL3 are shown in Table 7.

[0260] Table 7. Binding kinetics of DLL3 antibodies. Antibody Name ka(1 / Ms) kd (1 / s) KD (M) mAb301 1.85E+05 3.06E-05 1.65E-10 mAb302 8.02E+04 1.74E-05 2.17E-10 WT115-BMK1 (heterogeneous ligand) 2.10E+06 2.65E-03 1.26E-09 1.73E+06 1.50E-04 8.67E-11 WT115-BMK2 4.04E+05 3.98E-05 9.87E-11 Stability of Human Serum Petition 870250084316, dated 09 / 18 / 2025, pp. 346 / 503 151 / 203

[0261] Human serum was recently isolated from healthy donors by centrifugation. Samples were diluted in serum, and the serum volume represents more than 90% of the total volume. Five aliquots of the sample were incubated at 37 °C. Then, samples were collected on day 0, day 1, day 4, day 7, and day 14, respectively, and flash-frozen until analyzed in combination.

[0262] Sample stability was tested by binding to human DLL3 using ELISA. In summary, plates were pre-coated with 100 μL / well of 1 μg / ml WT115-hPro1.ECD.his at 4 °C overnight. The following day, plates were washed once with 1xPBST (PBS containing tween-20 at 0.05%), and blocking was performed by adding 200 μL of 1xPBS / BSA at 2% per well. During blocking, test antibodies were added to the plates at various concentrations (4 times serially diluted from 3 nM to 0.00018 nM). Plates were incubated at room temperature for 1 hour. Antibody binding to immobilized human DLL3 was detected by HRP of Goat IgG-Fc Fragment Cross-Adsorption Antibody (Betila, A80304P) and HRP of Mouse IgG-Fc Fragment Cross-Adsorption Antibody (Betila, A90-231P) which were diluted in 1*PBS / BSA at 2% at 1:5000. After incubation, the plates were washed 6 times using 1 xPBST.The color was developed by dispensing 100 µl of TMB substrate, and then the reaction was stopped by the addition of 100 µl of 2 M HCl. Absorbance was read at 450 nm and 540 nm using a microplate spectrophotometer. Human IgG1 isotype antibody was used as a negative control. All samples were tested in duplicate. After incubation in human serum at 37 °C for up to 14 days, the binding profile of mAb301 to the human DLL3 protein showed no changes (data not shown). Example 4. Synthesis of a Ligand Drug (1)

[0263] The binding drug (1) was prepared according to the following procedures: Synthesis of the intermediate (2) Petition 870250084316, dated 09 / 18 / 2025, pp. 347 / 503 152 / 203

[0264] Ac-Glu(OtBu)-Val-Cit-OH (19.9 mg, 39.7 pmol) was dissolved in N,N-dimethylformamide (400 pmol); 1-[bis(dimethylamino)methylene]-1H-1,2,3triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (18.1 mg, 47.6 pmol) and 2,4,6-trimethylpyridine (6.27 pmol, 47.6 pmol) were added; and the mixture was stirred at room temperature for 10 minutes. Then, methyl 4-aminomandelate (8.63 mg, 47.6 pmol) was added, and the mixture was stirred at room temperature for 21.5 hours, and then purified by reverse-phase fractional chromatography. The fraction containing the product was recovered, concentrated under vacuum to remove acetonitrile and lyophilized to obtain the alcohol (2) (28.5 mg, quantity).1H RMN (400 MHz, DMSO-d6) 09,95 (s, 1H), 8,07 (d, J = 7,4 Hz, 1H), 7,99 (d, J = 8,0 Hz, 1H), 7,66 (d, J = 8,4 Hz, 1H), 7,50 (d, J = 8,4 Hz, 2H), 7,25 (d, J = 8,4 Hz, 2H), 5,92 (s / s, 1H), 5,36 (s / s, 2H), 5,01 (s, 1H), 4,344,29 (m, 1H), 4,26-4,20 (m, 1H), 4,14-4,10 (m, 1H), 3,53 (s, 3H), 3,00-2,83 (m, 2H), 2,18-2,13 (m, 2H), 1,94-1,89 (m, 2H), 1,84-1,23 (m, 17H), 0,79 (d, J = 6,8 Hz, 3H), 0,75 (d, J = 6,8 Hz, 3H). MS (ESI) m / z: 665,30 [M+H]+.

[0265] Ac-Glu(t-Bu)-Glu(t-Bu)-Val-Cit-OH (50,0 mg, 72,8 pmol) foi Petição 870250084316, de 18 / 09 / 2025, pág. 348 / 503 153 / 203 dissolved in N,N-dimethylformamide (800 pL), 1[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (33.2 mg, 87.4 pmol) and 2,4,6-th-methylpyridine (11.5 pL, 87.4 pmol) were added, and the mixture was stirred at room temperature for 10 minutes. Then, methyl 4-aminomandelate (15.8 mg, 87.4 pmol) was added, and the mixture was stirred at room temperature for 16 hours, then purified by reverse-phase fractional chromatography. A fraction containing the product was recovered, concentrated under vacuum to remove acetonite, and lyophilized to obtain alcohol (12) (54.0 mg, 63.5 pmol).

[0266] 1H RMN (400 MHz, DMSO-d6) 010,00 (s, 1H), 8,26-7,88 (m, 3H), 7,68-7,60 (m, 1H), 7,57 (d, J = 8,4 Hz, 2H), 7,32 (d, J = 8,4 Hz, 2H), 6,00-5,97 (m, 1H), 5,43 (brs, 2H), 5,08 (s, 1H), 4,40-4,37 (m, 1H), 4,32-4,19 (m, 3H), 3,60 (s, 3H), 3,09-2,90 (m, 2H), 2,25-2,18 (m, 4H), 2,03-1,53 (m, 10H), 1,46-1,36 (m, 20H), 0,86 (d, J = 6,8 Hz, 3H), 0,82 (d, J = 6,8 Hz, 3H).

[0267] MS (ESI) m / z: 850,40 [M+H]+ Síntese do intermediário (43)

[0268] The intermediate (2) (140 mg, 0.165 mmol) was dissolved in N,N-dimethylformamide (4 mL), and the mixture was stirred while being cooled on ice for five minutes, after which bis(4-nitrophenyl) carbonate (108 mg, 0.355 mmol) and N,N-diisopropylethylamine (100 µL, 0.574 mmol) were added to it, and the mixture was stirred for 18 hours in a nitrogen atmosphere at room temperature. The organic solvent was removed by means of an evaporator, after which a 1:1 solution of acetonitrile and water was added, and the mixture was purified by reverse-phase fractional chromatography. A fraction containing the Petition 870250084316, dated 09 / 18 / 2025, pp. 349 / 503 154 / 203 product was recovered, concentrated under vacuum to remove acetonitrile and lyophilized to obtain intermediate (43) (130 mg, 0.128 mmol). MS (ESI) m / z: 1015.6 [M+H]+ Synthesis of the intermediate (44)

[0269] The intermediate (43) (85 mg, 0.084 mmol) was dissolved in N,N-dimethylformamide (2 mL), and 1-hydroxybenzotriazole (20 mg, 0.13 mmol) and commercially available monomethyl auristatin E (MMAE, 63 mg, 0.088 mmol) were added to it at room temperature. Then, diisopropylethylamine (75 μL, 0.43 mmol) was added, after which the mixture was stirred for 23 hours in a nitrogen atmosphere at room temperature. The organic solvent was removed by means of an evaporator, after which a 1:1 solution of acetonitrile and water was added, and the mixture was purified by chromatography. Petition 870250084316, dated 09 / 18 / 2025, pages 350 / 503 155 / 203 reverse phase fractionation. A fraction containing the product was recovered, concentrated under vacuum to remove acetonitrile and lyophilized to obtain intermediate (44) (94 mg, 0.059 mmol). MS (ESI) m / z: 1593.6 [M+H]+ Synthesis of the intermediate (45)

[0270] The intermediate (44) (94 mg, 0.059 mmol) was dissolved in tetrahydrofuran (5 mL) and water (2 mL), lithium hydroxide (1.0 M, 0.6 mL, 0.6 mmol) was added while the mixture was being cooled on ice, and the mixture was stirred in this state for 1 hour. Hydrochloric acid was added to the reaction solution to adjust the pH to 5, after which a 1:1 mixture of acetonitrile and water was added to it, and the mixture was purified by reverse-phase fractional chromatography. A fraction containing the product was recovered, Petition 870250084316, dated 09 / 18 / 2025, pp. 351 / 503 156 / 203 concentrated under vacuum to remove acetonitrile and lyophilized to obtain intermediate (45) (77 mg, 0.049 mmol). MS (ESI) m / z: 1579.7 [M+H]+ Synthesis of the intermediate (46)

[0271] The intermediate (45) (77 mg, 0.049 mmol) was dissolved in N,N-dimethylformamide (3 mL), then cooled on ice, and N,N-diisopropylethylamine (50 μL, 0.29 mmol) and 1H-benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (87 mg, 0.17 mmol) were added to it. Then, N-(5-aminopentyl)maleimide hydrochloride (35 mg, 0.16 mmol) was added and the mixture was returned to room temperature and stirred for 20 hours. Once the reaction was complete, purification was performed by phase-disease fractionation chromatography. Petition 870250084316, dated 09 / 18 / 2025, pp. 352 / 503 157 / 203 reverse. A fraction containing the product was recovered, concentrated under vacuum to remove acetonitrile and lyophilized to obtain intermediate (46) (65 mg, 0.037 mmol). MS (ESI, m / z): 1744.7 (M + H)+. Conversion of Intermediate (46) into Binding Drug (1) (1)

[0272] Acetonitrile (2 mL) and an 85 wt% aqueous phosphoric acid solution (1.00 mL, 14.6 mmol) were sequentially added to compound (46) (65 mg, 0.037 mmol) and the mixture was stirred at room temperature for 6 hours. After the reaction was complete, water (2 mL) was added, the reaction solution was purified by reverse-phase fractional chromatography and a fraction containing the product was recovered and concentrated under vacuum to remove the acetonitrile and then lyophilized to obtain the binding drug (1) (49 mg, 0.030 mmol). MS (ESI, m / z): 1631.6 (M + H)+. Petition 870250084316, dated 09 / 18 / 2025, pages 353 / 503 158 / 203 Example 5. Synthesis of Binding Drug (2) Synthesis of the intermediate (43)

[0273] The intermediate (2) (140 mg, 0.165 mmol) prepared as described in Example 1 was dissolved in N,N-dimethylformamide (4 mL), and the mixture was stirred while being cooled on ice for five minutes, after which bis(4-nitrophenyl)carbonate (108 mg, 0.355 mmol) and N,N-diisopropylethylamine (100 pL, 0.574 mmol) were added to it, and the mixture was stirred for 18 hours in a nitrogen atmosphere at room temperature. The organic solvent was removed by means of an evaporator, after which a 1:1 solution of acetonitrile and water was added, and the mixture was purified by reverse-phase fractional chromatography. A fraction containing the product was recovered, concentrated under vacuum to remove the acetonitrile, and lyophilized to obtain compound (43) (130 mg, 0.128 mmol). MS (ESI) m / z: 1015.6 [M+H]+ Synthesis of the intermediate (48) Petition 870250084316, dated 09 / 18 / 2025, pp. 354 / 503 159 / 203

[0274] The intermediate (43) (67 mg, 0.066 mmol) was dissolved in N,N-dimethylformamide (2 mL), and 1-hydroxybenzotriazole (17 mg, 0.11 mmol) and commercially available Exatecan mesylate (CAS: 169869-90-3, 35 mg, 0.066 mmol) were added to the mixture at room temperature. Then, diisopropylethylamine (50 μL, 0.29 mmol) was added, after which the mixture was stirred for 4 hours in a nitrogen atmosphere at room temperature. The organic solvent was removed by means of an evaporator, after which a 1:1 solution of acetonitrile and water was added, and the mixture was purified by reverse-phase fractional chromatography. A fraction containing the product was recovered, concentrated under vacuum to remove acetonitrile, and lyophilized to obtain compound 48 (57 mg, 0.043 mmol). MS (ESI, m / z): 1311.7 (M + H)+ Synthesis of the intermediate (49) Petition 870250084316, dated 09 / 18 / 2025, pages 355 / 503 160 / 203

[0275] The intermediate (48) (57 mg, 0.043 mmol) was dissolved in tetrahydrofuran (3 mL) and water (1.5 mL), lithium hydroxide (1.0 M, 0.5 mL, 0.5 mmol) was added while the mixture was being cooled on ice, and the mixture was stirred in this state for 1 hour. Hydrochloric acid was added to the reaction solution to adjust the pH to 5, after which a 1:1 mixture of acetonitrile and water was added to it, and the mixture was purified by reverse-phase fractional chromatography. A fraction containing the product was recovered, concentrated under vacuum to remove the acetonitrile, and lyophilized to obtain compound 49 (45 mg, 0.035 mmol). MS (ESI, m / z): 1297.6 (M + H)+ Petition 870250084316, dated 09 / 18 / 2025, pp. 356 / 503 161 / 203 Synthesis of the intermediate (50)

[0276] The intermediate (49) (45 mg, 0.035 mmol) was dissolved in N,N-dimethylformamide (3 mL), then cooled on ice, and N,N-diisopropylethylamine (30 μL, 0.17 mmol) and 1H-benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (55 mg, 0.11 mmol) were added to it. Then, N-(5-aminopentyl)maleimide hydrochloride (22 mg, 0.10 mmol) was added and the mixture was returned to room temperature and stirred for 18 hours. Once the reaction was complete, purification was performed by phase-division fractionation chromatography. Petition 870250084316, dated 09 / 18 / 2025, pp. 357 / 503 162 / 203 reverse. A fraction containing the product was recovered, concentrated under vacuum to remove acetonitrile, and lyophilized to obtain compound 50 (22 mg, 0.015 mmol). MS (ESI, m / z): 1462.7 (M + H)+. Conversion of Intermediate (50) into Binding Drug (2) (2)

[0277] Acetonitrile (1 mL) and an 85% by weight aqueous solution of phosphoric acid (1.0 mL, 14.6 mmol) were added sequentially to compound (50) (22 mg, 0.015 mmol) and the mixture was stirred at room temperature for 1.5 hours. After the reaction was complete, water (1 mL) was added, the solution of Petition 870250084316, dated 09 / 18 / 2025, pp. 358 / 503 163 / 203 reaction was purified by reverse-phase fractional chromatography and a fraction containing the product was recovered and concentrated under vacuum to remove acetonitrile and then lyophilized to obtain the ligand drug (2) (18.8 mg, 0.0139 mmol).1H NMR (300 MHz; DMSO-d6) δ10.04 (s, 1H), 8.10-8.05 (m, 4H), 7.80-7.77 (m, 2H), 7.59-7.55 (m, 2H), 7.35-7.30 (m, 3H), 6.99 (d, J = 8.8 Hz, 2H), 6.54-6.53 (m, 1H), 6.01 (solids, 1H), 5.74 (d, J = 9.0 Hz, 1H), 5.43 (solids, 4H), 5.33-5.28 (m, 2H), 4.29-4.15 (m, 4H), 3.19-2.98 (m, 5H), 2.43-2.38 (m, 5H), 2.272.20 (m, 7H), 1.95-1.83 (m, 8H), 1.73-1.62 (m, 4H), 1.42-1.30 (m, 7H), 1.23-1.13 (m, 3H), 0.84 (m, 9H). MS (ESI, m / z): 1349.2 (M + H)+ Example 6: Chromatographic separation of the binding drug (1) Form A and Form B

[0278] The binding drug (1) is purified by reversed-phase fractional chromatography on a C18 silica gel column (20X 150 mm, 5 pm) under gradient conditions (mobile phase A: 0.1% TFA and 99.9% water, mobile phase B: 0.1% TFA and 99.9% MeCN). Each fraction containing the product (Form A of the binding drug (1), which is also referred to herein as binding drug (1-A); and Form B of the binding drug (1), which is also referred to herein as binding drug (1B)) is recovered and concentrated under vacuum to remove acetonitrile, then lyophilized to obtain the binding drug (1-A) and the binding drug (1-B), respectively.

[0279] RP-HPLC is subsequently performed to analyze the produced drug binders. Briefly, the analysis is conducted using an XBridge Shield RP 18, 4.6 x 150 mm, 3.5 µm (Waters catalog no. 186003045), in an Agilent 1260 HPLC system. This system is equipped with a binary gradient pump, a temperature-controlled column compartment, an autosampler, and a diode array detector. The operating conditions are defined as follows: a flow rate of 1.0 mL / min at 50 °C, with mobile phase A (MPA) comprising 0.1% trifluoroacetic acid (TFA) in water and mobile phase B (MPB) containing 0.1% TFA in acetonitrile. Other elution conditions can be found in Table 8. Petition 870250084316, dated 09 / 18 / 2025, pp. 359 / 503 164 / 203 below. UV at 215 nm, 252 nm and 280 nm are used to detect the sample signals. Example 7: Chromatographic Separation of Drug Binder (2) (mixture) into Drug Binder (2) Form A and Form B Binding drug 2 Exatecan RPHPLC Separation Exatecan 2-A binding drug Exatecan 2-B binding drug

[0280] The binding drug (2) (75 mg) is purified by reverse-phase fractional chromatography on a C18 silica gel column (20X 150 mm, 5 µm) under gradient conditions (mobile phase A: 0.1% TFA and 99.9% water, mobile phase B: 0.1% TFA and 99.9% MeCN). Each fraction containing the product (Form A of the binding drug (2), which is also referred to herein as binding drug (2-A); and Form B of the binding drug (2), which is also referred to herein as Petition 870250084316, dated 09 / 18 / 2025, pp. 360 / 503 165 / 203 as binding drug (2-B)) is recovered and concentrated under vacuum to remove acetonitrile, then lyophilized to obtain binding drug (2-A) (40 mg) and binding drug (2-B) (23 mg), respectively.

[0281] Binding Drug (2-A): MS (ESI) m / Z: 1349.5 [M=H]+

[0282] Binding Drug (2-B): MS (ESI) m / Z: 1349.5 [M=H]+

[0283] RP-HPLC was subsequently performed to analyze the produced ligand drugs. Briefly, the analysis was conducted using an XBridge Shield RP 18, 4.6 x 150 mm, 3.5 µm (Waters catalog no. 186003045), on an Agilent 1260 HPLC system. This system was equipped with a binary gradient pump, a temperature-controlled column compartment, an autosampler, and a diode array detector. The operating conditions were defined as follows: a flow rate of 1.0 mL / min at 50 °C, with mobile phase A (MPA) comprising 0.1% trifluoroacetic acid (TFA) in water and mobile phase B (MPB) containing 0.1% TFA in acetonitrile. Other elution conditions can be found in Table 8 below. UV wavelengths of 215 nm, 252 nm, and 280 nm were used to detect the sample signals.

[0284] Table 8. RP-HPLC elution conditions Time (min) A (%) B (%) 0.0 95 5 5.0 60 40 15.0 60 40 20.0 10 90 25.0 10 90 25.1 95 5 31.0 95 5

[0285] An exemplary result is presented in Figure 2, showing the separation of the two overlapping drug-ligand diastereomers in the chromatogram of the diastereomeric mixture. Petition 870250084316, dated 09 / 18 / 2025, pp. 361 / 503 166 / 203 Example 8. Synthesis of Ligand Drug (2) Form B

[0286] The ligand drug (2-B) (the epimer (S)) as illustrated in Figure 3 was also produced. The ligand drug (2-B) is a synthetic derivative of Exatecan, a cytotoxic agent of the camptothecin family, containing a cleavable peptide linker (EEVC) and a Maleimide-Csamine antibody conjugation site that are linked to the p-amino mandelic acid fragment. The ligand drug (2-B) was synthesized (e.g., as described here in Example 5) using stereospecific intermediates. The ligand drug (2-B) was obtained (0.54 g, 86% yield). MS (ESI, pos.): Calculated for C65H77FN12O19 [M+H]: 1350.37, Found: 1350.30. NMR was subsequently performed using the obtained Ligand Drug (2-B) (in DMSO) (data not shown). Example 9: Stochastic conjugation via disulfide reduction to produce DLL3-ADCs (see, for example, Jackson, David, Organic Process Research & Development 2016, 20, 852-866, incorporated herein by reference in its entirety, and Tsuchikama, K. et al., Protein & Cell 2018, 9(1), 33-46, incorporated herein by reference in its entirety)

[0287] This example provides an exemplary protocol for reducing the disulfide groups of the antibodies disclosed herein, and conjugating the reduced antibodies to the Drug-Binder conjugates, for example, Drug-Binder (1), (1-A), (1-B), (2), (2-A) or (2-B), described herein. Step 1: Antibody disulfide reduction a) Dilute the antibody to 15 mg / mL (0.1 mM IgG) in PBS (pH 7.4); b) Prepare a fresh stock solution of 20 mM (5.7 mg / mL) of tris(2-carboxyethyl)phosphine (TCEP) in H2O; c) Add 25 µL of TCEP stock solution to 1 mL of 1a antibody (final TCEP concentration of 0.5 mM); d) Incubate at 37 °C for 2 hours (check for the presence of free thiols using the 5,5'-dithiobis-(2-nitrobenzoic) acid (DTNB) test); and e) Aliquot the reduced antibody into 4 tubes (250 pL each). Step 2: Conjugation of the drug-binding agent to the antibody. Petition 870250084316, dated 09 / 18 / 2025, pp. 362 / 503 167 / 203 a) Prepare a 10 mM stock solution of cytotoxin ligand conjugate in DMSO (DMA, DMF, or CH3CN are also acceptable); b) Add 5 equivalents of 12.5 pL of stock solution to each tube of reduced antibody (ligand-cytotoxin conjugate stock solution with a final concentration of 0.5 mM); c) Incubate overnight at 4°C for 4 hours at room temperature; check for the presence of free thiols using the DTNB test; and d) Run analytical HIC to determine DAR and homogeneity. Example 10: Stochastic conjugation via disulfide reduction to produce DLL3-ADCs (see, for example, Jackson, David, Organic Process Research & Development 2016, 20, 852-866, incorporated herein by reference in its entirety, and Tsuchikama, K. et al., Protein & Cell 2018, 9(1), 33-46, incorporated herein by reference in its entirety)

[0288] This example provides an additional exemplary protocol for the reduction and purification of a DLL3 antibody for conjugation to ligand-cytotoxic conjugates, for example, Ligand Drug (1), (1-A), (1-B), (2), (2-A) or (2-B), described in this document. All DMSO buffers and stock solutions are purged with argon for 1 hour before use. 1) Aliquot 1 mL of 10 mg / mL stock antibody into a tube. 2 mL Eppendorf tube. 2) Dilute with 1 mL of 100 mM borate (pH 8.4) to obtain a stock solution of 10 mg / mL (67 pM). 3) Prepare a 50 mM stock solution of TCEP in water. 4) Add 20 mL of TCEP to 2 mL of antibody and incubate at 37 °C for 3 hours. 5) Aliquot into 4 Eppendorf tubes of 0.5 mL and place 3 tubes in storage at 20 °C. 6) Purify a 0.5 mL aliquot (approximately 5 mg) via SEC in Bio-Rad using degassed PBS. 7) Collect the monomeric antibody peak in a sealed tube (volume Petition 870250084316, dated 09 / 18 / 2025, pp. 363 / 503 168 / 203 total of approximately 4 mL) at 4 °C. 8) Aliquot into 4 identical 1 mL Eppendorf tubes (1 mg / mL). 9) Add 6 equivalents of the drug binder from mM stock solutions in DMSO to each tube. 10) Incubate at 4 °C for 48 hours. 11) Analyze using HIC, SDS-PAGE, and LC / MS and compare with the control. Example 11: Site-specific conjugation on lysine to form DLL3-ADC. Synthesis of thioester ligand

[0289] 3,3'-Dithiopropionic acid (1.0 g, 5.0 mmol) was dissolved in 10 mL Petition 870250084316, dated 09 / 18 / 2025, pp. 364 / 503 169 / 203 THF and 100 μL DMF, pyridine (4.0 mL, 50 mmol) and oxalyl chloride (1.5 mL, 15.0 mmol) were added dropwise under ice cooling, and the resulting mixture was stirred at room temperature for two hours. After two hours, thiophenol (1.53 mL, 15.0 mmol) was added dropwise, and the resulting mixture was stirred again at room temperature for two hours. The reaction solution was concentrated under reduced pressure and purified by normal-phase chromatography with hexane / ethyl acetate to obtain S-phenyl 3[(3-oxo-3-phenylsulfanyl-propyl)disulfanyl]propanethioate (1.77 g, 4.5 mmol) as the target product. MS(ESI)m / z: 395.1[M+H]+

[0290] S-phenyl 3-[(3-oxo-3-phenylsulfanyl-propyl)disulfanyl]propanethioate (1.77 g, 4.5 mmol) was dissolved in 5.0 mL of H2O and 1.0 mL of DMSO, tris(2-carboxyethyl)phosphine hydrochloride (1.93 g, 6.75 mmol) was added to it, and the resulting mixture was stirred at room temperature for two hours. After 2 hours, the solution was extracted with ethyl acetate to obtain S-phenyl 3-sulfanylpropanethioate (1.29 g, 6.5 mmol) as the target product. MS(ESI)m / z:199.2[M+H]+ Petition 870250084316, dated 09 / 18 / 2025, pp. 365 / 503 170 / 203

[0291] 2.7 mL of acetonitrile and 0.3 mL of pyridine were added and dissolved in S-phenyl 3-sulfanyl propanethioate (1.29 g, 6.5 mmol). Then, succinic anhydride (0.65 g, 6.5 mmol) and 4-dimethylaminopyridine (12.2 mg, 0.1 mmol) were added, and the resulting mixture was stirred for one hour. 20 mL of 1 M aqueous hydrochloric acid solution were added, and the resulting mixture was extracted with ethyl acetate. The solution was concentrated under reduced pressure to obtain (4-oxo-4-(3-oxo-3-phenylsulfanylpropyl)sulfanylbutanoic acid (1.25 g, 4.2 mmol). MS(ESI)m / z:299.0[M+H]+ Thioester Ligand and Peptide Coupling Petition 870250084316, dated 09 / 18 / 2025, pp. 366 / 503 171 / 203 Ac-RGNCAYHKGQIIWCTYH-NH (SEQ ID NO: 6)

[0292] Ac-RGNCAYHKGQIIWCTYH-NH2 (SEQ ID NO:6) (30 mg, 14.4 μmol, where 4 and 14 cysteines form a disulfide bond in the molecule) was dissolved in 1 mL of N,N'-dimethylformamide and ((4-oxo-4-(3-oxo-3-phenylsulfanylpropyl)sulfanylbutanoic acid (64 mg, 0.22 mmol)) and WSC^HCl (41 mg, 0.22 mmol) were added to it. The solution was stirred at room temperature for 12 hours, a 0.1% trifluoroacetic acid solution was added, and the fractions were eluted by preparative reverse-phase chromatography. lyophilized to obtain the thiophenol activation compound coupled to the peptide and ligand (22.3 mg, Petition 870250084316, dated 09 / 18 / 2025, pp. 367 / 503 172 / 203 9.4 μπΊΟΐ). MS (ESI)m / z:z=3 790 [M+3H]3+, z=4 593[M+4H]4+Specific modification of the DLL3 antibody site

[0293] The thiophenol activating compound coupled to the peptide and ligand is dissolved in N,N'-dimethylformamide. DLL3 antibody is dissolved in sodium acetate buffer (pH 4.7), peptide reagent (30 equivalents relative to the antibody) is added, and the solution is stirred at room temperature for one hour. The reaction solution is replaced with 100 mM sodium citrate buffer (pH 2.9) to stop the reaction and is subsequently replaced with 20 mM PBS buffer to generate a DLL3 antibody-peptide conjugate.

[0294] The mass of the DLL3-antibody-peptide conjugate is measured by ESITOFMS by adding tris(2-carboxyethyl)phosphine hydrochloride solution (one equivalent relative to the antibody) to the DLL3-antibody-peptide conjugate and stirring the solution at room temperature. Samples are then analyzed by ESI-TOFMS.

[0295] The DLL3 antibody-peptide conjugate formed above and the unconjugated DLL3 antibody are also analyzed by HIC using a detector with a wavelength of 280 nm. Cleavage of the DLL3-antibody-peptide conjured lysate Petition 870250084316, dated 09 / 18 / 2025, pp. 368 / 503 173 / 203 Cleavage between -CO- and

[0296] The DLL3-antibody-peptide conjugate solution (20 mM PBS buffer) obtained above is replaced with a 0.5 M hydroxylamine, 10 mM EDTA (pH 5.5) solution (Amicon 3K) and left to stand at room temperature for two hours. After two hours, the solution is replaced with 20 mM PBS buffer, 10 mM EDTA (pH 7.4) to obtain a thiol-introduced DLL3 antibody.

[0297] The mass of the DLL3-antibody-peptide conjugate is measured by ESITOFMS by adding tris(2-carboxyethyl)phosphine hydrochloride solution (one equivalent relative to the antibody) and the solution is stirred at room temperature. The samples are then analyzed by ESI-TOFMS. Conjugation of the drug-binding agent with a DLL3-antibody-modified peptide conjugate (thiol-introduced)

[0298] This example provides two exemplary protocols for conjugation of the modified DLL3 antibody to the Drug-Binder conjugates, for example, Drug-Binder (1), (1-A), (1-B), (2), (2-A) or (2-B), described in this Petition 870250084316, dated 09 / 18 / 2025, pp. 369 / 503 174 / 203 document:

[0299] Protocol 1 (see, for example, Jackson, David, Organic Process Research & Development 2016, 20, 852-866, incorporated herein by reference in its entirety, and Tsuchikama, K. et al., Protein & Cell 2018, 9(1), 33-46, incorporated herein by reference in its entirety) a) Prepare a 10 mM stock solution of ligand-cytotoxin conjugate in DMSO (DMA, DMF, or CH3CN are also acceptable); b) Add 5 equivalents of 12.5 pL of stock solution to each tube of DLL3 antibody peptide conjugate (ligand-cytotoxin conjugate stock solution with a final concentration of 0.5 mM); c) Incubate overnight at 4°C for 4 hours at room temperature under reducing conditions; and d) Perform analytical HIC to determine DAR and homogeneity.

[0300] Protocol 2: (see, for example, Matsuda et al., ACS Omega 2019, 4, 24, 20564-20570, incorporated here by full reference) (e) Dimethylacetamide (DMA) and a 10 mM DMA solution of ligand-cytotoxin conjugate (10 equiv) are added to a solution of DLL3-antibody-peptide conjugate in conjugation buffer, and the mixture is incubated at 20 °C. f) After 2 h, a small amount of the reaction mixture (0.5 mL) is collected for IPC analysis. g) After verification of the IPC analysis, the reaction mixture is tempered with an excess amount of a 50 mM aqueous solution of N-acetylcysteine ​​and incubated at 25 °C for 15 min. h) This reaction mixture is purified by a TFF system using a Sartocon Slice 200 ECO Hydrosart membrane (30 kDa; Sartorius) and conjugation buffer as DF buffer at an antibody concentration of 20 mg / mL. i) Next, buffer exchange of this solution is conducted by a TFF system using a Sartocon Slice 200 ECO Hydrosart membrane (30 kDa; Sartorius) and formulation buffer as DF buffer to provide ADC in Petition 870250084316, dated 09 / 18 / 2025, pages 370 / 503 175 / 203 formulation buffer. Example 12: Alternative synthesis of thiol-introduced DLL3 antibody by the One-Pot method

[0301] The thiophenol activating compound coupled to the peptide and ligand is dissolved in N,N'-dimethylformamide. DLL3 antibody (e.g., 500 μg) is dissolved in sodium acetate buffer (pH 5.5), and the peptide reagent (30 equivalents relative to the antibody) is added to the mixture. The solution is stirred at room temperature for 1 hour. Then, a solution of 0.5 M hydroxylamine and 10 mM EDTA (pH 5.5) is added in the same amount as sodium acetate, and the resulting mixture is left at room temperature for two hours. After two hours, the solution is replaced with 20 mM PBS buffer, 10 mM EDTA (pH 7.4) to obtain thiol-introduced DLL3 antibody. Example 13: Alternative Conjugation Method (see, for example, Matsuda et al., ACS Omega 2019, 4, 24, 20564-20570, incorporated here by full reference)

[0302] Step 1: Conjugation of the affinity peptide to the antibody A solution of antibody in AcONa buffer (pH 5.5) is added to a dimethylformamide (DMF) solution of peptide reagent 1 (9 equiv.) and stirred at 25 °C using the Chemglass system. After 1 h, a small amount of the reaction mixture is taken for IPC analysis. After verification of the IPC analysis, the reaction mixture is purified by a TFF system using a Sartocon®Slice 200 ECO Hydrosart® membrane (30 kDa; Sartorius) and AcONa buffer (pH 5.5) as diafiltration (DF) buffer. Next, the buffer exchange of this solution is performed by a TFF system using a Sartocon® Slice 200 ECO Hydrosart® membrane (30 kDa; Sartorius) and formulation buffer (20 mM histidine containing 5% trehalose, pH 5.2) as DF buffer, at an antibody concentration of 6.9 mg / mL, to provide the antibody-peptide conjugate 2 in the formulation buffer.

[0303] Step 2: Cleavage of the Ligand A to a conjugate solution Petition 870250084316, dated 09 / 18 / 2025, pp. 371 / 503 A 176 / 203 antibody-peptide buffer formulation is added to 0.25 M aqueous ethylenediaminetetraacetic acid (EDTA) solution (12 equiv., pH 7.4), polysorbate 20 (0.0265 mL), and 0.5 M aqueous TCEP solution (20 equiv.) at 37 °C. The resulting mixture is measured with a pH meter, showing a final pH of 5.2. After 1 h at 37 °C, a small amount of the reaction mixture (e.g., 0.5 mL) is collected for IPC analysis. After verification of the IPC analysis, the reaction mixture is purified by a TFF system using a Sartocon® Slice 200 ECO Hydrosart® membrane (30 kDa; Sartorius) and 10 mM AcONa buffer (pH 5.5) as DF buffer. Next, the buffer exchange of this solution is performed by a TFF system using a Sartocon® Slice 200 ECO Hydrosart® membrane (30 kDa; Sartorius) and conjugation buffer (50 mM PBS, 10 mM EDTA, pH 7.4) as DF buffer, to provide a ligand cleavage product in the conjugation buffer.

[0304] Step 3: Reoxidation A solution of ligand cleavage product in conjugation buffer is added to a 50 mM solution of DHAA dimethyl sulfoxide (40 equiv), and the mixture is incubated at room temperature. After 3 h, a small amount of the reaction mixture (e.g., 0.5 mL) is collected for IPC analysis. After verification of the IPC analysis, the reaction mixture is purified by a TFF system using a Sartocon®Slice 200 ECO Hydrosart® membrane (30 kDa; Sartorius) and conjugation buffer as DF buffer, to provide the ligand reoxidation product in the conjugation buffer.

[0305] Step 4: Drug Conjugation To a solution of the reoxidation product in conjugation buffer, dimethylacetamide (DMA) and a 10 mM DMA solution of the Binding Drug (10 equivalents) are added, and the mixture is incubated at 20 °C. After 2 h, a small amount of the reaction mixture (e.g., 0.5 mL) is collected for IPC analysis. After verification of the IPC analysis, the reaction mixture is tempered with an excess of 50 mM aqueous N-acetylcysteine ​​solution and incubated at 25 °C for 15 min. This reaction mixture is purified by a TFF system using a Sartocon Slice 200 membrane. Petition 870250084316, dated 09 / 18 / 2025, pp. 372 / 503 177 / 203 ECO Hydrosart® (30 kDa; Sartorius) and conjugation buffer as DF buffer. Subsequently, buffer exchange of this solution is conducted by a TFF system using a Sartocon Slice 200 membrane. ECO Hydrosart® (30 kDa; Sartorius) and formulation buffer as DF buffer to provide ADC in the formulation buffer. Example 14: ADC Production

[0306] The ADCs described in Table 9 below were produced using a method as described in the Examples above. All ADCs produced have < 3% high molecular weight species aggregates (% HMW). Each of the ADCs was then prepared in a formulation buffer (20 mM histidine, 5% (w / v) trehalose, pH 5 to 6, such as 5.2, 5.5 or 6.0).

[0307] Table 9. ADCs produced Reference number of the ADC Antibody DLL3 Ligand-Drug (Drug) Conjugation Site DAR ADC-009 or ADC-009M (used interchangeably here) mAb300 Binding drug (2) (Exatecan) K248 2 ADC-009-A mAb300 Binding drug (2) (Exatecan) Form A K248 2 ADC-009-B mAb300 Binding drug (2) (Exatecan) Form B K248 2 ADC-013 or ADC-013M (used interchangeably here) mAb302 Binding drug (2) (Exatecan) K248 2 ADC-013-A mAb302 Binding drug (2) (Exatecan) Form A K248 2 Petition 870250084316, dated 09 / 18 / 2025, pp. 373 / 503 178 / 203 Reference number of the ADC DLL3 Antibody Ligand-Drug (Drug) Conjugation Site DAR ADC-013-B mAb302 Binding drug (2) (Exatecan) Form B K248 2 ADC-015 or ADC-015M (used interchangeably here) mAb301 Binding drug (2) (Exatecan) K248 2 ADC-015-A mAb301 Binding drug (2) (Exatecan) Form A K248 2 ADC-015-B mAb301 Binding drug (2) (Exatecan) Form B K248 2 ADC-010 mAb300 Binding drug (1) (MMAE) K248 2 ADC-014 mAb302 Binding drug (1) (MMAE) K248 2 ADC-018 or ADC-018M (used interchangeably here) mAb300 Binding drug (2) (Exatecan) Interchain 4 ADC-018-A mAb300 Binding drug (2) (Exatecan) Form A Interchain 4 ADC-018-B mAb300 Binding drug (2) (Exatecan) Form B Interchain 4 ADC-020 or ADC-020- mAb302 Binding drug (2) Interchain 4 Petition 870250084316, dated 09 / 18 / 2025, pp. 374 / 503 179 / 203 Reference number of the ADC Antibody DLL3 Ligand-Drug (Drug) Conjugation Site DAR M (used interchangeably here) (Exatecan) ADC-020-A mAb302 Binding drug (2) (Exatecan) Form A Interchain 4 ADC-020-B mAb302 Binding drug (2) (Exatecan) Form B Interchain 4 ADC-016 or ADC-016M (used interchangeably here) mAb301 Binding drug (2) (Exatecan) Interchain 4 ADC-016-A mAb301 Binding drug (2) (Exatecan) Form A Interchain 4 ADC-016-B mAb301 Binding drug (2) (Exatecan) Form B Interchain 4 ADC-019 or ADC-019M (used interchangeably here) mAb300 Binding drug (1) (MMAE) Interchain 4 ADC-017 mAb301 Binding drug (1) (MMAE) Interchain 4 Example 15: Development capacity

[0308] Size exclusion chromatography (SEC) analysis was performed using a 4.6 mm ID x 300 mm AdvanceBio column (SEC 300A, 2.7 µm, Agilent, catalog # PL1580-5301) on an HPLC. The maximum column pressure was 400 bar. The running buffer was 1 x PBS (HyClone) + 10% IPA. A Petition 870250084316, dated 09 / 18 / 2025, pp. 375 / 503 A 180 / 203 sample was loaded and the flow rate was 0.2 mL / minute. The isocratic gradient length was 27 min. Absorbance was monitored at 280 nm. Chromatographic peaks were integrated to determine the percentage of homogeneity and retention time. The stationary phase of the column, along with the choice of mobile phase, supports hydrophobic and electrostatic interactions, in addition to molecular scaling (much milder secondary interactions compared to SMAC).

[0309] Hydrophobic interaction chromatography (HIC) analysis was performed using a 4.6 mm internal diameter x 3.5 cm TSKgel Butyl-NPR column (2.5 µm particle size, Tosoh Bioscience LLC, PN 14947) on an HPLC. The maximum column pressure was 200 bar. The column was equilibrated with 100% mobile phase buffer A (50 mM sodium phosphate, pH 7 with 1.5 M ammonium sulfate) at a flow rate of 0.5 mL / minute at room temperature. The sample was loaded and eluted using a gradient from 100% mobile phase buffer A to 100% mobile phase buffer B (50 mM sodium phosphate, pH 7 with 20% (v / v) isopropanol) at 0.5 mL / minute. The elution time and buffer are specified in Table 10 below, and the duration of the linear gradient was 20 min. Absorbance was monitored at 280 nm.The sample retention time was calculated and compared to a set of standard controls to identify antibodies with longer retention times (greater hydrophobicity) and the presence of multiple species.

[0310] Table 10. HIC elution conditions Time (min) A (%) B (%) 0 100 0 2 100 0 22 0 100 24 0 100 24.1 100 0 27 100 0 Petition 870250084316, dated 09 / 18 / 2025, pp. 376 / 503 181 / 203

[0311] Reversed-phase liquid chromatography (RP-HPLC) was also performed to analyze DLL3 antibodies and produced ADCs. Briefly, samples were analyzed on an Agilent instrument equipped with a 4.6 mm x 100 mm column (Agilent AdvanceBio RP-mAb Diphenyl, 3.5 µm particle size, Agilent catalog no. 795975-944). The column temperature was 70 °C and the maximum column pressure was 600 bar. Buffer A used was water + 0.1% TFA, while buffer B used was acetonitrile + 0.1% TFA. The flow rate was set to 0.4 mL / minute and the linear gradient duration was 27 minutes. Other elution conditions can be found in Table 11 below. UV at 215 nm, 252 nm, and 280 nm were used to detect sample signals.

[0312] Table 11. RP-HPLC elution conditions Time (min) A (%) B (%) 0 70 30 2 70 30 24 52 48 24.1 5 95 27 5 95 27.1 70 30 35 70 30

[0313] Representative results are provided here as Figures 4A-4D. Figure 4A showed SEC results indicating that mAb302 had <3% HMW aggregates, which was higher than mAb300, and conjugation had very little effect on aggregation. Figure 4B compared mAb300 and mAb302 using HIC and showed that mAb302 was more hydrophobic than mAb300. mAb300 was compared with mAb301 (data not shown), indicating that mAb300 and mAb301 had similar hydrophobicity profiles. SEC was also performed to compare mAb300 and mAb301 (data not shown), and mAb300 and mAb301 demonstrated similar elution times. Petition 870250084316, dated 09 / 18 / 2025, pp. 377 / 503 182 / 203

[0314] Figure 4C showed that the mAb300 conjugates (ADC-009 and ADC-010) were more hydrophobic than the antibody, and the MMAE conjugate was more hydrophobic than the Exatecan conjugate. Similarly, Figure 4D showed that the mAb302 conjugates (ADC-013 and ADC-014) were more hydrophobic than the antibody, and the MMAE conjugate was more hydrophobic than the Exatecan conjugate. Example 16: Linkage characterization (Biacore™)

[0315] Kinetic measurements were performed using a Cytiva Biacore T200 instrument in HBS-EP+ buffer. A human anti-Fc antibody was covalently coupled to a CM5 Series S chip (Cytiva) using EDC / NHS chemistry and deactivated with ethanolamine prior to use. After equilibration in the running buffer, anti-DLL3 antibodies were captured in channels 2, 3, and 4, while channel 1 was used as a reference. Human, cino, mouse, and rat (Acro) DLL3 antigens were tested at a 4-fold serial dilution of 100 nM to 0.02 with a blank buffer included. After each antigen cycle, the chip surface was regenerated using 10 mM glycine, which facilitated the removal of both antibody and antigen. Data were processed using a 1:1 linkage model in the Biacore T200 evaluation software.

[0316] Figure 5 provides exemplary Biacore sensorgrams of the tested antibodies (mAb300, mAb301, mAb302 and a DLL3 IgG1a (having a heavy chain disclosed as SEQ ID NO:71 in WO2022153195A1 and a light chain disclosed as SEQ ID NO:72 in WO2022153195A1) as a positive control) binding to cine, human, mouse and rat DLL3. The calculated affinity data are provided in Table 12 below, indicating that mAb300 and mAb301 have similar binding characteristics compared to mAb302. Petition 870250084316, dated 09 / 18 / 2025, pp. 378 / 503 183 / 203

[0317] Table 12. Biacore™ Affinity Analysis KD (nM) ka (M-1s-1) kd (s-1) mAb300 mAb301 mAb302 DLL3 lgG1a mAb300 mAb301 mAb302 DLL3 lgG1a mAb300 mAb301 mAb302 DLL3 lgG1a Human 0.012 0.022** < 0.01 0.044 1.8x106 2.0x106 5.4x105 2.7x107 2.1x105 4.5x105 < IO5 1.2x10-3 Cino 2.3 2.2 1.6 0.32* 4.7x105 3.2x105 1.2x105 3.8x106 1.1x10-3 7.0x104 1.9x10⁴ 1.2x10⁻³ Mouse < 0.05 < 0.25 37* 0.86 1.6x10⁵ 1.7x10⁵ 2.2x10⁴ 7.1x10⁵ < 10⁻⁵ <4x10⁻⁵ 8.1x10⁴ 6.1x10⁴ Rat < 0.01 < 0.08 3.2* 0.56* 5.5x10⁵ 4.8x10⁵ 1.4x10⁵ 2.1x10⁶ < 10⁻⁵ <4x10⁻⁵ 4.5x10⁴ 1.2x10⁻³ *Large contributions **50 nM excluded from the analysis due to biphasic decay Petition 870250084316, dated 09 / 18 / 2025, pp. 379 / 503 184 / 203 Example 17: Determination of DAR (HIC and RP-HPLC)

[0318] Experiments were carried out to evaluate DARs of the produced ADC compositions, using HIC and RP-HPLC, both described above in Example 15.

[0319] Representative results are presented in Figure 6. In summary, good conjugation efficiency was observed for ADCs DAR 2 and DAR 4, and the HIC data aligned with the RP-HPLC results: the ADC-016 composition exhibited a DAR of 3.9 using HIC and 3.6 using RP-HPLC; the ADC-017 composition exhibited a DAR of 4.0 using HIC and 3.9 using RP-HPLC; and the ADC-015 composition exhibited a DAR of 1.8 using HIC and 1.7 using RP-HPLC. Example 18: Characterization of ADC-015-M, ADC-015-A, ADC-015-B, ADC-016-M, ADC-016-A and ADC-016-B.

[0320] The ADCs, including ADC-015-M, ADC-015-A, ADC-015-B, ADC016-M, ADC-016-A and ADC-016-B, were produced as described in the previous Examples, formulated in 20 mM histidine, 5% trehalose, pH 6.0, and subjected to further analyses regarding their aggregation percentages, DARs, endotoxins and yield percentages following the methods below.

[0321] Aggregation Determination: ADCs (25 pg) were injected into an AdvanceBio SEC 300A size exclusion chromatography column (2.7 µm, 4.6 x 300 mm, Agilent PN PL1580-5301) at room temperature by isocratic elution in 1 x PBS (Cytiva Life Sciences PN SH30258.01) with 10% (v / v) isopropanol at a flow rate of 0.2 mL / minute. Samples were monitored at 280 nm and 254 nm on an Agilent 1260 Infinity II Bio-Inert HPLC system equipped with a multi-wavelength detector. ChemStation software was used to quantify each sample chromatography to determine aggregation.

[0322] DAR Determination: ADCs (50 pg) were injected into a TSKgel Butyl-NPR hydrophobic interaction chromatography column (2.5 µm, 4.6 x 35 mm, Tosoh Bioscience PN 14947) at room temperature and eluted with Petition 870250084316, dated 09 / 18 / 2025, pages 380 / 503 A 20-minute linear gradient from 0 to 100% B was performed using Mobile Phase A: 50 mM sodium phosphate, 1.5 M ammonium sulfate, pH 7, and Mobile Phase B: 50 mM sodium phosphate, 20% (v / v) isopropanol, pH 7. Samples were monitored at 280 nm and 254 nm on an Agilent 1260 Infinity II Bio-Inert HPLC system equipped with a multi-wavelength detector. ChemStation software was used to quantify each sample chromatography, allowing the determination of DAR.

[0323] Endotoxin determination: ADCs diluted (1:10) with LAL reagent water (Associates of Cape Cod Inc. P / N W020P) were loaded into LAL Endosafe endotoxin test cartridges (FDA licensed), 0.01 EU / mL (Charles River P / N PTS2001F) according to the User Guide and analyzed for endotoxin on the Endosafe nexgen MCS (Charles River).

[0324] Yield determination: The absorbances of conjugated and unconjugated antibodies were quantified at 280 nm using a NanoDrop One microvolume UV-Vis spectrophotometer (Thermo Scientific). The resulting measurements were used to calculate concentrations using the extinction coefficient of the unconjugated antibody. Total quantities were determined by multiplying the volume by the calculated concentration, with the overall yield calculated by subtracting the final quantity from the initial quantity.

[0325] HIC analysis was performed using a Tosoh TSKgel Butyl-NPR column, 4.6 x 35 mm, 2.5 µm in an HPLC. The column was equilibrated with 100% of the mobile phase Buffer A (1.5 M (NH4)2SO4, 50 mM Na2HPO4 / NaH2PO4, pH 7.0) at a flow rate of 0.5 mL / minute at room temperature. The sample (20 μL, 1 mg / mL) was loaded and eluted using a gradient from 100% of the mobile phase buffer A to 100% of the mobile phase buffer B (50 mM Na2HPO4 / NaH2PO4, 25% v / v IPA, pH 7.0) at 0.5 mL / minute. The elution time and buffer are specified in Table 13 below. Absorbance was monitored at 280 nm.

[0326] Table 13. HIC elution conditions Petition 870250084316, dated 09 / 18 / 2025, pages 381 / 503 186 / 203 Time (min) A (%) B (%) 0.00 100.0 0.0 2.00 100.0 0.0 22.00 0.0 100.0 24.00 0.0 100.0 24.20 100.0 0.0 27.00 100.0 0.0

[0327] Size exclusion chromatography (SEC) analysis was performed using a 4.6 mm ID x 300 mm AdvanceBio column (SEC 300A, 2.7 µm, Agilent, catalog # PL1580-5301) on an HPLC. The maximum column pressure was 400 bar. The running buffer was 1 x PBS (HyClone) + 10% IPA. The sample was loaded and the flow rate was 0.2 mL / minute. The isocratic gradient length was 27 min. Absorbance was monitored at 280 nm. Chromatographic peaks were integrated to determine the percentage of homogeneity and retention time. The stationary phase of the column, along with the choice of mobile phase, supports hydrophobic and electrostatic interactions, in addition to molecular scaling (much milder secondary interactions compared to SMAC).

[0328] Exemplary results are provided in Table 14 below, as well as in Figures 7A-7R and 8A-8R. SEC data showed less than 3% of aggregates observed for all ADCs tested. The HIC chromatogram showed that the ADC with Form B exhibited a shorter retention time, suggesting that Form B is less hydrophobic than Form A.

[0329] Table 14. Analytical results. Reference ADC. No. % of aggregation DAR Endotoxin (EU / mg) % yield ADC-015-A < 1% 1.1 0.02 86% ADC-015-B < 1% 1.9 < 0.03 60% Petition 870250084316, dated 09 / 18 / 2025, pp. 382 / 503 187 / 203 ADC-015-M < 1% 1.9 < 0.02 81% ADC-016-A 1.2 3.8 — — ADC-016-B < 1% 4 < 0.05 50% ADC-016-M 1.6% 3.6 < 0.03 31% Example 19: Cytotoxicity assays (hDLL3 B16F10 cell line)

[0330] The manufactured ADCs were evaluated for their cytotoxicity effects on the B16F10 mouse melanoma cell line engineered to express human DLL3 (referred to herein as hDLL3 B16F10). Briefly, hDLL3 B16F10 cells were seeded per well on Day -1 (referred to herein as D-1) and cultured under 5% CO2 at 37°C. The following day (e.g., Day 0 or D0), the test compounds were added to each well in a series of dilutions. At the end of the observation period, cells were harvested and cell viability was assessed using the CellTiter-Glo® Luminescent Cell Viability (CTG) assay following the manufacturing protocols.

[0331] A representative result is provided in Figures 9A-9C. 1,000 cells were seeded per well on Day -1. The compound tested was ADC017 comprising mAb301 and MMAE and having a target DAR of 4. MMAE (NJ Bio stock - lot no. NJBP-75-184-002) and Exatecan (NJ Bio stock - lot no. NJBP-75-184-001) were also evaluated in parallel, serving as controls. The DPBS dilution series were 500 - 0.008 nM (9 concentrations, 4x dilution). The endpoints were selected as 72 hours of incubation and 96 hours of incubation, and the corresponding cell survival curves were plotted in Figure 9A and Figure 9B, respectively. The IC50 and maximum inhibition percentages were then calculated using Prism, and the result is shown in Figure 9C.

[0332] An additional experiment was conducted to test additional mAb301 ADCs. 1,500 cells were seeded per well on Day -1. The compounds Petition 870250084316, dated 09 / 18 / 2025, pages 383 / 503 188 / 203 tested included ADC-015 (comprising mAb301 and Exatecan, and having a target DAR of 2), ADC-016 (comprising mAb301 and Exatecan, and having a target DAR of 4), and ADC-017 (comprising mAb301 and MMAE, and having a target DAR of 4). MMAE (NJ Bio stock - lot no. NJBP-75-184-002) and Exatecan (NJ Bio stock - lot no. NJBP-75-184-001) were also evaluated in parallel, serving as controls. Additional controls were used, including a drug-binding isotype control (1) (MMAE) having a target DAR of 4, as well as a drug-binding isotype control (2) (Exatecan) having a target DAR of 4. The DPBS dilution series was 500 - 0.008 nM (9 concentrations, 4x dilution). Each compound at each concentration was tested in triplicate. The endpoint was selected as 72 hours of incubation, and the corresponding cell survival curve was plotted in Figure 9D.The IC50 and maximum inhibition percentages were then calculated using Prism, and the result is shown in Figure 9E. These results suggest that MMAE conjugates showed better activity than Exatecan conjugates. Additional endpoints, such as 96 hours and 120 hours of incubation, are under investigation. Additionally or alternatively, an initial seeding of 1,000 cells is also evaluated. Example 20: Cytotoxicity assays (Human DLL3 high expression stable cell line (WT115-293F.hPro1.2E5))

[0333] The produced ADCs (ADC-015-A, ADC-015-B, ADC-015-M, ADC016-A, ADC-016-B and ADC-016-M) were evaluated for their cytotoxicity effects on the HEK293F tumor cell line engineered to overexpress hDLL3 as described above (WT115-293F.hPro1.2E5). Exatecan and an ADC isotype (anti-HEWL VHH-Fc isotype conjugated to Drug Ligand (2), a mixture of Form A and Form B, having a target DAR of 4) were tested in parallel and served as controls.

[0334] In summary, on day -1, cells were seeded in a 96-well plate at a density of 3,000 cells / well, diluting 1 million cells in 30 mL of pre-warmed FreeStyle 293 expression medium. Petition 870250084316, dated 09 / 18 / 2025, pp. 384 / 503 189 / 203 (ThermoFisher 12338018) supplemented with 6 μg / mL of Blasticidin (Thermo Scientific J67216.XF). The cells used for these assays were between passages 5 and 13 and their viability was verified as > 90%. The test compounds (ADC-015-A, ADC-015-B, ADC-015-M, ADC-016-A, ADC-016-B, ADC-016M, Exatecan and ADC isotype) were added on day 0 as 10x concentrated working stocks, serially diluted in PBS from a maximum concentration of 500 nM after a series of 3 or 4-fold dilutions. Each concentration was tested in triplicate. The test plates were incubated in a humidified incubator at 37°C with 5% CO2 for 96 hours. The endpoint was measured using the Cell Titer Glow reagent, and the protocol and luminescence were recorded on the SpectraMax i3x. The cell survival rate in each well was determined using the following calculation: Survival rate (%) = (LumTest article - LumMedium control) / (LumVehicle control - LumMedium control) * 100%

[0335] A dose-response curve using a nonlinear regression model with a variable slope log(inhibitor) vs response-response was fitted to the data using GraphPad Prism 9 to calculate the relative IC50. The maximum response was defined as “100 - minimum survival rate”.

[0336] Exemplary results are presented in Figures 10A-10E and Tables 15-19 below. Figures 10A and 10B provide data from an exemplary experiment, and the signal variation obtained from day 0 in the PBS control was 6.9. Figures 10C and 10D provide data from another exemplary experiment, and the signal variation obtained relative to day 0 in the PBS control was 13. Regarding the data in Figure 10E, the signal variation obtained relative to day 0 in the PBS control was also 13. Furthermore, Figure 10A, Figure 10C, and Figure 10E represent the concentration of ADCs (or Exatecan for the Exatecan-treated group) on the x-axis, while Figure 10B and Figure 10D represent the concentration of the binding drug (2) (Form A, or Form B, or a mixture thereof) (or Exatecan for the Exatecan-treated group) on the x-axis. Petition 870250084316, dated 09 / 18 / 2025, pages 385 / 503 190 / 203

[0337] As shown in Figures 10A-10D and Tables 15-18, similar cytotoxicity was observed for ADC-015-B and ADC-015-M. As shown in Figure 10E and Table 19, similar cytotoxicity was observed for ADC-016-M, ADC-016-A, and ADC-016-B.

[0338] Table 15. IC50 and other calculations corresponding to Figure 10A. Compound DAR IC50 (nM)* 95% CI 50% inhibition (nM)# Maximum inhibition Exatecan 2.7 2.8 96% Isotype ADC 4 201 157 75% ADC-015-A 1.1 10.3 8.4 to 12.8 14.8 85% ADC-015-B 1.9 5.5 4.9 to 6.2 5.9 91% ADC-015-M 1.9 5.8 4.8 to 7.1 6.9 92% ADC-016-M 3.6 4.9 4.5 to 5.4 5.0 92% * Prisma, og (inhibitor) vs response - Variable slope # Prisma, interpolated mean values

[0339] Table 16. IC50 and other calculations corresponding to Figure 10B. Compound IC50 (nM)* Exatecan 2.7 ADC-015-A 11.4 ADC-015-B 10.5 ADC-015-M 11 ADC-016-M 17.4 Prisma, log (inhibitor) vs response - Variable slope

[0340] Table 17. IC50 and other calculations corresponding to Figure 10C. Compound DAR IC50 (nM)* 95% CI 50% inhibition (nM)# Maximum inhibition Exatecan 3.5 2.8 95% Isotype ADC 4 191 199 76% Petition 870250084316, dated 09 / 18 / 2025, pp. 386 / 503 191 / 203 ADC-015-A 1.1 18 14.2 to 23.6 32 81% ADC-015-B 1.9 5.7 4.9 to 6.5 7.0 91% ADC-015-M 1.9 5.1 4.2 to 6.3 6.1 91% ADC-016-M 3.6 4.8 3.6 to 6.2 5.3 90% * Prisma, log (inhibitor) vs response - Variable slope # Prisma, interpolated mean values

[0341] Table 18. IC50 and other calculations corresponding to Figure 10D. Compound IC50 (nM)* Exatecan 3.5 ADC-015-A 19.8 ADC-015-B 10.8 ADC-015-M 9.8 ADC-016-M 17.2 Prisma, log (inhibitor) vs response - Variable slope

[0342] Table 19. IC50 and other calculations corresponding to Figure 10E. Compound DAR IC50 (nM)* 50% inhibition (nM)# Maximum inhibition ADC-016-M 3.6 4.8 5.3 90% ADC-016-A 3.8 4.1 92% ADC-016-B 3.8 5.2 93% Prisma, log (inhibitor) vs response - Variable slope # Prisma, interpolated mean values Example 21: Cytotoxicity assays (ADC-015, ADC-016 and ADC017 in H69, CORL279, SHP77 and H460 cells)

[0343] The produced ADCs were subsequently evaluated for their cytotoxic effects on endogenously DLL3-expressing human SCLC cell lines, such as H69, CORL279, and SHP77. H460, which is a DLL-negative non-small cell lung cancer cell line, was also tested in parallel, serving as a control.

[0344] In summary, the cells were seeded by well on Day -1 Petition 870250084316, dated 09 / 18 / 2025, pp. 387 / 503 192 / 203 (referred to here as D-1) and cultured under 5% CO2 at 37°C. For CORL279 and SHP77, the seeding density was 3,000 cells per well. For H69, the seeding density was 9,000 cells per well. And, for H460, the seeding density was 1,000 cells per well. The following day (e.g., Day 0 or D0), the tested compounds were added to each well in a series of dilutions, including ADC-015 (comprising mAb301 and Exatecan, and having a target DAR of 2), ADC-016 (comprising mAb301 and Exatecan, and having a target DAR of 4), and ADC-017 (comprising mAb301 and MMAE, and having a target DAR of 4). MMAE (NJ Bio stock - batch no. NJBP-75184-002) and Exatecan (NJ Bio stock - batch no. NJBP-75-184-001) were also evaluated in parallel, serving as controls.Additional controls were used, including a drug-binding isotype control (1) (MMAE) having a target DAR of 4, as well as a drug-binding isotype control (2) (Exatecan) having a target DAR of 4. The DPBS dilution series was 500 - 0.008 nM (9 concentrations, 4x dilution). At the end of the observation period (120 hours of incubation), cells were harvested and cell viability was assessed using the CellTiter-Glo® Luminescent Cell Viability (CTG) assay following manufacturing protocols.

[0345] Relevant H69 data are provided in Figures 11A-11F. Three representative cell survival curves were plotted in Figures 11A, 11C, and 11E. The IC50 and maximum inhibition percentages were then calculated using Prism, and the results are shown in Figures 11B, 11D, and 11F, respectively.

[0346] Relevant data for CORL279 are provided in Figures 12A-12D. Two representative cell survival curves were plotted in Figures 12A and 12C. The IC50 and maximum inhibition percentages were then calculated using Prism and the result is shown in Figures 12B and 12D, respectively.

[0347] Relevant data from SHP77 are provided in Figures 13A-13B. A representative cell survival curve has been plotted in Figure Petition 870250084316, dated 09 / 18 / 2025, pages 388 / 503 193 / 203 13A. The IC50 and maximum inhibition percentages were then calculated using Prism and the result is shown in Figure 13B.

[0348] Relevant H460 data are provided in Figures 14A-14B. A representative cell survival curve was plotted in Figure 14A. The IC50 and maximum inhibition percentages were then calculated using Prism, and the result is shown in Figure 14B. Lower sensitivity to MMAE (and the MMAE conjugate) was observed. In some modalities, such data may suggest that IC50 > 150 nM for the Exatecan conjugate may reflect non-specific DLL3 activity. Example 22: Cytotoxicity assays (ADC-009 and ADC-010 on H69, CORL279, SHP77, and DMS79)

[0349] The produced ADCs were subsequently evaluated for their cytotoxic effects on human SCLC cell lines endogenously expressing DLL3, such as H69, CORL279, SHP77 and DMS79.

[0350] In summary, cells were seeded per well on Day -1 (referred to here as D-1) at a density of 9,000 cells per well and cultured under 5% CO2 at 37°C. The following day (e.g., Day 0 or D0), the tested compounds were added to each well in a series of dilutions, including ADC-009 (containing Exatecan) and ADC-010 (containing MMAE). MMAE (NJ Bio stock - lot no. NJBP-75-184-002) was also evaluated in parallel, serving as a control. The dilution series in DPBS was 500 - 0.008 nM (9 concentrations, 4x dilution). At the end of the observation period (96 hours of incubation), the cells were harvested and cell viability was assessed using the CellTiter-Glo® Luminescent Cell Viability (CTG) assay following the manufacturing protocols.

[0351] Relevant data are provided in Figures 15A-15E. Representative cell survival curves of SHP77, DMS79, H69 and CORL279 were plotted in Figures 15A, 15B, 15C and 15D, respectively. The IC50 and maximum inhibition percentages were then calculated using Prism and the result is shown in Figure 15E. Petition 870250084316, dated 09 / 18 / 2025, pp. 389 / 503 194 / 203 Example 23: Antitumor effects in cell line-derived xenograft (CDX) models

[0352] Briefly, 5-8 week old female CB17.SCID mice were subcutaneously implanted with 5x10⁶ SHP77 (surface expression of ~5,000 DLL3) or 7x10⁶ H69 (surface expression of ~2,000 DLL3) at a cell:Matrigel ratio of 1:1. Upon reaching a mean tumor volume of 200 mm³, animals were randomized into treatment groups. The tested compounds were administered intravenously (iv). Animals were removed from the study when they reached human endpoints, including tumor volume greater than 2000 mm³ and body weight loss. Tumor growth inhibition (TGI) was calculated as follows: TGI = (1-(ΔTν [treatment group]^TV [vehicle group]) * 100

[0353] In an initial study, ADC-015-B and ADC-016-B were tested using the SHP77 CDX model, as described herein. The compounds tested at various dosages (1 mg / kg or 3 mg / kg) were administered intravenously (iv) on Day 1. The vehicle, DAR 2 Isotype ADC (anti-HEWL VHH-Fc isotype conjugated to Drug Ligand (2), mixture of Form A and Form B, having a target DAR of 2) and DAR 4 Isotype ADC (anti-HEWL VHH-Fc isotype conjugated to Drug Ligand (2), mixture of Form A and Form B, having a target DAR of 4) were also tested in parallel as controls. Tumor volumes and body weights were monitored throughout the study.

[0354] The corresponding results can be found in Figure 16A (the graph of the mean tumor volume (TV) of the group for when 1 animal reached the TV endpoint and was removed from the study or on Day 31), Figure 16B and Table 20. The result indicated that the mAb301 Exatecan ADCs (DAR 2 and DAR 4) showed inhibition of tumor growth with a single dose; both the DAR 2 and DAR 4 ADCs showed retarded tumor growth compared to the non-DLL3-bound ADCs (isotype controls) at 3 mg / kg and 1 mg / kg (and vehicle); and no significant change in effect was observed in body weight (<10%). Petition 870250084316, dated 09 / 18 / 2025, pages 390 / 503 195 / 203

[0355] Table 20. TGI of the Treatment Groups. TGI Treatment Group (%) 1 mg / kg DAR 2 Isotype ADC 49 1 mg / kg DAR 4 Isotype ADC 43 3 mg / kg ADC-015-B 94 1 mg / kg ADC-015-B 87 3 mg / kg ADC-016-B 96 1 mg / kg ADC-016-B 99

[0356] In a subsequent study, the antitumor activity of ADC-015-M, ADC-015-B, ADC-016-M and ADC-016-B was investigated in two CDX models of small cell lung cancer (SCL) SHP77 and H69, implanted subcutaneously in female CB17 SCID mice. DLL3 expression in these cell lines was confirmed by flow cytometry using a control anti-DLL3 antibody (with a heavy chain as established in CAS Registry Number: 2897724-56-8 and a light chain as established in CAS Registry Number: 2897724-55-7).

[0357] The compounds tested (including ADC-015-B, ADC-015-M, ADC016-B, and ADC-016-M) were administered intravenously (iv), in a single dose or in a repeated-dose regimen, depending on the studies. Vehicle, mAb301, DAR 2 Isotype ADC (anti-HEWL VHH-Fc isotype conjugated to Drug Ligand (2), mixture of Form A and Form B, having a target DAR of 2) and DAR 4 Isotype ADC (anti-HEWL VHH-Fc isotype conjugated to Drug Ligand (2), mixture of Form A and Form B, having a target DAR of 4) were also tested in parallel as controls. Tumor volumes and body weights were monitored twice weekly for up to 56 days after initial treatment. Dose levels and dosing regimens are described in Table 21 below.

[0358] Table 21. Dosage levels and schedules Petition 870250084316, dated 09 / 18 / 2025, pp. 391 / 503 196 / 203 Group No. Target Compound DAR Dose Level (mg / kg) Dosing Day(s) Route Vehicle n= 1 Vehicle NA NA D1 iv PBS 9 2 ADC-015-B 2 3 D1 iv PBS 9 3 ADC-015-B 2 1 D1 iv PBS 9 4 ADC-015-B 2 0.3 D1, D8, D15 iv PBS 9 5 ADC-015-M 2 1 D1 iv PBS 9 6 ADC-016-B 4 3 D1 iv PBS 9 7 ADC-016-B 4 1 D1 iv PBS 9 8 ADC-016-B 4 0.3 D1, D8, D15 iv PBS 7 * 9 ADC-016-M 4 1 D1 iv PBS 9 10 DAR 4 Isotype ADC 4 1 D1 iv PBS 9 11 DAR 2 Isotype ADC 2 1 D1 iv PBS 9 Animals were removed from the study, regardless of dosage or disease.

[0359] The SHP77 CDX results were obtained and are provided in Figures 16A-17K and Table 22 below. In Figure 16A, the graph of the group mean tumor volume (TV) was stopped when the first animal reached the TV endpoint and was removed from the study.

[0360] Table 22. Data analysis of SHP77 CDX results. Petition 870250084316, dated 09 / 18 / 2025, pages 392 / 503 197 / 203 Treatment Group Day 28 TV (Mean ± SEM, mm3) One-way ANOVA (Dunnett's post-hoc test vs. Vehicle) Day 28 Percentage of tumor growth inhibition (%TGI) (vs. vehicle) Vehicle 1277 ±125 DAR 2 ADC isotype, 1 mg / kg 815 ± 88 <0.0001 49% DAR 4 ADC isotype, 1 mg / kg 757±103 <0.0001 43% ADC-015-B, 3 mg / kg 267 ± 19 <0.0001 94% ADC-015-B, 1 mg / kg 340 ± 23 <0.0001 87% ADC-015-B, 0.3 mg / kg x 3 378 ± 83 <0.0001 84% ADC-015-M, 1 mg / kg 272 ± 31 <0.0001 93% ADC-016-B, 3 mg / kg 244 ± 19 <0.0001 96% ADC-016-B, 1 mg / kg 221 ± 18 <0.0001 99% ADC-016-B, 0.3 mg / kg x 3 239 ± 14 <0.0001 97% ADC-016-M, 1 mg / kg 257 ± 9 <0.0001 96%

[0361] The results indicate that all groups treated with ADC They exhibited delayed tumor growth compared to the vehicle control; all mAb301 ADCs exhibited delayed tumor growth compared to the isotype control ADCs; a dose-dependent efficacy was apparent in the ADC-015-B treatment groups; and ADC-015-B and ADC016-B showed similar efficacy to ADC-015-M and ADC-016-M, respectively (1 mg / kg).

[0362] In a third study, mAb300 and the ADCs that compose it Petition 870250084316, dated 09 / 18 / 2025, pages 393 / 503 Tumors 198 / 203 were tested using the SHP77 CDX model, as described herein. The compounds tested at various dosages (including 5 mg / kg ADC-009-M, 10 mg / kg ADC-009-M, 5 mg / kg ADC-018-M, 2.5 mg / kg ADC-018-M, 5 mg / kg ADC-019-M, 2.5 mg / kg ADC-019-M) were administered intravenously (iv) on Day 1, Day 4, and Day 8. Vehicle and 5 mg / kg mAb300 were also tested in parallel as controls. Tumor volumes and body weights were monitored throughout the study.

[0363] The corresponding results can be found in Figure 16E (the graph of the mean tumor volume (TV) of the group for when 1 animal reached the TV endpoint and was removed from the study or on Day 31), Figure 16F and Table 23. The result indicated that all mAb300 Exatecan ADC dosage groups tested showed tumor regression; the inhibition of tumor growth for mAb300 MMAE ADC was similar to the unconjugated antibody group; and no significant effect was observed on body weight with any treatment.

[0364] Table 23. Inhibition of tumor growth (TGI) of the treatment groups. TGI Treatment Group (%) 5 mg / kg mAb300 57 5 mg / kg ADC-009-M (mAb300 Exatecan ADC DAR 2) 113 10 mg / kg ADC-009-M (mAb300 Exatecan ADC DAR 2) 114 5 mg / kg ADC-018-M (mAb300 Exatecan ADC DAR 4) 110 2.5 mg / kg ADC-018-M (mAb300 Exatecan ADC DAR 4) 109 5 mg / kg ADC-019-M (mAb300 MMAE ADC DAR 4) 45 2.5 mg / kg ADC-019-M (mAb300 MMAE ADC DAR 4) 77 Example 24: Antitumor effects in cell line-derived xenograft (PDX) models Petition 870250084316, dated 09 / 18 / 2025, pages 394 / 503 199 / 203

[0365] To investigate the antitumor activity of ADCs, as described herein, in monotherapy, xenograft models derived from small cell lung cancer (SCLC) patients LXFS 538, LXFS573 and LXFS 2156, as well as colon cancer models CXF 94 and CXF 742 implanted subcutaneously in nude NMRI female mice were established.

[0366] These PDX models were selected based on DLL3 expression data, confirmed by immunohistochemistry (IHC) in formalin-fixed paraffin-embedded (FFPE) tumor samples (rabbit anti-human DLL3 monoclonal antibody clone E3J5R; Cell Signaling Technology cat # 71804 / 3) and related model metadata.

[0367] Female NMRI nude / nu mice (from Charles River Laboratories), aged 5 to 8 weeks, were subcutaneously implanted with tumor fragments of LXFS 538 (SCLC, IHC scores: 152 (membranous); 212 (cytoplasmic)), LXFS573 (SCLC, IHC scores: 42 (membranous); 51 (cytoplasmic)), LXFS 2156 (SCLC, IHC scores: 8 (membranous); 16 (cytoplasmic)), CXF 94 (SCLC, IHC scores: 5 (membranous); 9 (cytoplasmic)) or CXF 742 (colorectal, IHC scores: 142 (membranous); 168 (cytoplasmic)). Upon reaching individual tumor volumes of 50-250 mm3, mice were assigned to treatment groups based on tumor volumes targeting mean / median tumor volumes comparable to the control group and were subsequently treated according to Table 24 below. Dosing began within 24 hours of randomization. The observation period was a maximum of 5 weeks after the last treatment.

[0368] Table 24. Group and Therapy Assignment Schedule Group No. Compound Single Dose* (mg / kg) Dose Volume* (mL / kg) Dosing Days Route Vehicle No. 1 Vehicle NA 5 D1, D8 iv PBS 8 2 ADC-016-M 5 5 D1 iv PBS 8 Petition 870250084316, dated 09 / 18 / 2025, pages 395 / 503 200 / 203 3 ADC-016-M 5 5 D1, D8 iv PBS 8 4 ADC-015-M 5 5 D1 iv PBS 8 Total number of mice: 32 *based on the last body weight measurement

[0369] In summary, the efficacy experiments comprised 4 groups with 8 animals / group. All treatments were administered intravenously (iv) at a dose of 5 mg / kg. ADC-015-M was tested as a single dose and ADC-016-M as a single and repeated dose on day 1 (D1) and day 8 (D8). As a reference, a control vehicle was included and dosed in a repeated schedule on day 1 and day 8. Tumor volume and body weight were monitored twice weekly for 6 weeks after initial treatment. Tumor volumes were determined by two-dimensional measurement with a digital caliper and calculated according to the formula Tumor volume = (1 χ w2) χ 0.5, where 1 = tumor length and w = tumor width. Animals were removed from the study when they reached human endpoints, including tumor volume greater than 2000 mm3 and body weight loss endpoint.

[0370] The results obtained from the CXF 742 PDX model are provided in Figures 18A-18I and Table 25 below, indicating that TGI was observed with ADC016-M and ADC-015-M. The animals removed from the study due to the outcome of TV (TV>2000mm3) are listed below: Vehicle: 1 on Day 17, 1 on Day 45 and 1 on Day 49; ADC-016-M, 5 mg / kg χ 1: 1 on Day 38; and ADC-015-M, 5 mg / kg χ 1: 2 on Day 49.

[0371] Table 25. TV and TGI of the treatment groups in the CXF 742 PDX model. Group / ADC TV Average (mm3) TGI (%) Vehicle 1,655 ADC-016-M; 5 mg / kg χ 1 476 76 ADC-016-M; 5 mg / kg χ 2 457 78 Petition 870250084316, dated 09 / 18 / 2025, pages 396 / 503 201 / 203 ADC-015-M; 5 mg / kg χ 1 806 56

[0372] The results obtained from the LXFS 2156 PDX model are provided in Figures 19A-19I and Tables 26 below, indicating that TGI was observed with ADC-016-M, with a 2-dose treatment regimen. Animals removed from the study due to TV endpoint (TV > 2000 mm3) are listed below: Vehicle: 1 on Day 24, 1 on Day 27, 2 on Day 38, 2 on Day 42; ADC-016-M, 5 mg / kg χ 1: 2 on Day 31, 1 on Day 35, 1 on Day 38, 2 on Day 42; ADC-016-M, 5 mg / kg χ 2: 1 on Day 24; and ADC-015-M, 5 mg / kg χ 1:1 on Day 27, 3 on Day 35, and 4 on Day 38.

[0373] Table 26. TV and TGI of the treatment groups in the LXFS 2156 PDX model. Group / ADC TV Average (mm3) TGI (%) Vehicle 1,344 ADC-016-M; 5 mg / kg χ 1 1.127 20 ADC-016-M; 5 mg / kg χ 2 318 85 ADC-015-M; 5 mg / kg χ 1 1.350 1

[0374] The results obtained from the PDX LXFS 573 model are provided in Figures 20A-20I and Table 27 below, showing that a delay in tumor growth was observed with ADC-016-M.

[0375] Table 27. TV and TGI of the treatment groups in the LXFS 573 PDX model. Group / ADC TV Average (mm3) TGI (%) Vehicle 1,505 ADC-016-M; 5 mg / kg χ 1 711 57 ADC-016-M; 5 mg / kg χ 2 788 51 Petition 870250084316, dated 09 / 18 / 2025, pages 397 / 503 202 / 203 ADC-015-M; 5 mg / kg χ 1 1.318 13

[0376] The results obtained from the CXF 94 PDX model are provided in Figures 21A-211 and Table 28 below, indicating that TGI was observed with ADC016-M and ADC-015-M. Animals removed from the study due to the outcome of TV (TV > 2000 mm3) are listed below: Vehicle: 2 on Day 31 and 1 on Day 38; ADC-016-M, 5 mg / kg χ 1: 1 on Day 38; ADC-016-M, 5 mg / kg χ 2: 1 on Day 31 (due to accessory tumor size); and ADC-015-M, 5 mg / kg χ 1: 2 on Day 31.

[0377] Table 28. TV and TGI of the treatment groups in the CXF 94 PDX model. Group / ADC Average TV (mm3) TGI (%) Vehicle 1,280 ADC-016-M; 5 mg / kg χ 1,825 38 ADC-016-M; 5 mg / kg χ 2,748 46 ADC-015-M; 5 mg / kg χ 1,1214 1

[0378] The results obtained from the LXFS 538 PDX model are provided in Figures 22A-22J and Tables 29-30 below, indicating that TGI was observed with ADC-015-M and ADC-016-M and ADC-016-M with a 2-dose regimen showed prolonged tumor regression. The results showed that tumor regression was observed in all dosed groups from day 7 post-dose; regrowth was observed in single-treatment groups (with ADC-015-M and ADC-016-M) from day 18 post-dose; and marginal tumor regrowth was observed in the group treated with ADC-016-M twice (day 1 and day 8) until day 46 post-dose, and 3 complete responders (> 3 consecutive TV measurements=0 mm3) were observed. Animals removed from the study due to TV endpoint (TV > 2000 mm3) are listed below: Vehicle: 1 on Day 35; and ADC-015-M, 5 mg / kg χ 1: 1 found dead on Day 25. Petition 870250084316, dated 09 / 18 / 2025, pages 398 / 503 203 / 203

[0379] Table 29. TV and TGI of treatment groups on Day 35 (D35) in the LXFS 538 PDX model. Group / ADC TV Average (mm3) TGI (%) Vehicle 1,108 ADC-016-M; 5 mg / kg χ 1 208 92 ADC-016-M; 5 mg / kg χ 2 5 114 ADC-015-M; 5 mg / kg χ 1 500 69

[0380] Table 30. TV and TGI of treatment groups on Day 42 (D42) in the LXFS 538 PDX model. Group / ADC TV Average (mm3) TGI (%) Vehicle 1,422 ADC-016-M; 5 mg / kg χ 1 376 79 ADC-016-M; 5 mg / kg χ 2 9 110 ADC-015-M; 5 mg / kg χ 1 897 49

[0381] Other ADCs, as disclosed here, are also studied using the established PDX models.

[0382] Throughout this application, various publications, patents, patent applications, and other documents have been referenced. Disclosures of these publications, patents, patent applications, and other documents in their entirety are incorporated herein by reference for all purposes, including to describe more fully the state of the art to which the subject matter disclosed herein belongs. Although the subject matter disclosed has been described with reference to the examples provided above, it should be understood that various modifications could be made without departing from the spirit of the subject matter disclosed. Many variations will become apparent to those skilled in the art upon review of this descriptive report.

Claims

1. Antibody-drug conjugate (ADC) of Formula (I): (I) or a salt thereof, characterized in that: n is an integer from 1 to 8, and Ab represents an antibody that binds to DLL3 (“DLL3 antibody”).

2. ADC according to claim 1, characterized in that the ADC is Formula (IA): Petition 870250084316, dated 09 / 18 / 2025, p. 400 / 503 2 / 21 η 3. ADC according to claim 1, characterized in that the ADC is Formula (IB): Petition 870250084316, dated 09 / 18 / 2025, p. 401 / 503 3 / 21 or a salt thereof.

4. Antibody-drug conjugate (ADC) of Formula (A): Petition 870250084316, dated 09 / 18 / 2025, p. 402 / 503 4 / 21 (A), characterized in that each thick shaded line represents a chain of an antibody that binds to DLL3 (the DLL3 antibody), the sulfurs represented are cysteine ​​residues (optionally C226 and / or C229) of the DLL3 antibody and X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, p.403 / 503 5 / 21 where the wavy line represents the connection point to the remainder of the ADC of Formula (A).

5. Antibody-drug conjugate (ADC) of Formula (B): Petition 870250084316, dated 09 / 18 / 2025, p. 404 / 503 6 / 21 characterized in that each thick shaded line represents a chain of an antibody that binds to DLL3 (DLL3 antibody), the CH2CH2CH2CH2NH group represented is derived from a lysine residue (optionally any one or more of K246, K248, K288, K290 or K317 according to EU numbering) of the DLL3 antibody, and X represents the structure below or a salt thereof: HCk Λ3 where the wavy line represents the connection point to the remainder of the ADC of Formula (B).

6. ADC, according to claim 5, characterized in that the DLL3 antibody comprises an amino acid sequence as set forth in SEQ ID NO:4 and in which the lysine residue is the 150th amino acid residue of SEQ ID NO:4 (e.g., K248 according to EU numbering). 7.ADC, according to claim 5, characterized in that the DLL3 antibody comprises an amino acid sequence as set forth in SEQ ID NO:5 and in that the lysine residue is the 150th amino acid residue of SEQ ID NO:5 (e.g., K248 according to EU numbering).

8. ADC, according to claim 5, characterized in that the DLL3 antibody comprises an amino acid sequence as set forth in SEQ ID NO:10 and in that the lysine residue is the 152nd amino acid residue of SEQ ID NO:10 (e.g., K248 according to EU numbering).

9. ADC, according to any one of claims 4 to 8, characterized in that X represents the structure below or a salt thereof: wherein the wavy line represents the point of attachment to the remainder of the ADC of Formula (A) or (B). 10.ADC, according to any one of claims 4 to 8, characterized in that X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, p. 406 / 503 8 / 21 OH where the wavy line represents the connection point for the remainder of the ADC of Formula (A) or (B).

11. ADC, according to any one of claims 1 to 10, characterized in that the DLL3 antibody comprises: (1) a CDR1, CDR2 and CDR3 of a (VHH), wherein the VHH comprises an amino acid sequence as set forth in SEQ ID NO: 14, 15 or 16; or (2) at least one VH, wherein the at least one VH comprises CDR1, CDR2 and CDR3, and wherein: (i) CDR1 comprises an amino acid sequence as set forth in SEQ ID NO:1 or 7; (ii) CDR2 comprises an amino acid sequence as set forth in SEQ ID NO:2 or 8; and (iii) CDR3 comprises an amino acid sequence as set forth in SEQ ID NO:3 or 9. 12.ADC, according to any one of claims 1 to 11, characterized in that DLL3 comprises: Petition 870250084316, dated 09 / 18 / 2025, page 407 / 503 9 / 21 (a) a CDR1 as set forth in SEQ ID NO: 1; a CDR2 as set forth in SEQ ID NO: 2; and a CDR3 as set forth in SEQ ID NO: 3; or (b) a CDR1 as set forth in SEQ ID NO: 7; a CDR2 as set forth in SEQ ID NO: 8; and a CDR3 as set forth in SEQ ID NO:

9.

13. ADC, according to any one of claims 1 to 12, characterized in that the DLL3 antibody comprises a VHH comprising the amino acid sequence as set forth in any one of SEQ ID NOs: 14-16.

14. ADC, according to any one of claims 1 to 13, characterized in that the DLL3 antibody further comprises a constant domain of human IgG. 15.ADC, according to any one of claims 1 to 14, characterized in that the DLL3 antibody further comprises an Fc fragment.

16. ADC, according to claim 14, characterized in that the human IgG is a human IgG1.

17. ADC, according to claim 15, characterized in that the Fc fragment comprises a homodimer of an amino acid sequence as set forth in SEQ ID NO:

17.

18. ADC, according to any one of claims 1 to 17, characterized in that the DLL3 antibody comprises at least one unique VHH domain.

19. ADC, according to any one of claims 1 to 18, characterized in that the DLL3 antibody comprises two unique VHH domains, each of which is conjugated to a chain of an Fc fragment. 20.ADC, according to any one of claims 1 to 19, characterized in that the DLL3 antibody comprises a homodimer of an amino acid sequence as set forth in any one of Petition 870250084316, dated 09 / 18 / 2025, p. 408 / 503 10 / 21 SEQ ID NO:4, 5 or 10.

21. ADC, according to any one of claims 1 to 3 and 11 to 20, characterized in that n is 1.

22. ADC, according to any one of claims 1 to 20, characterized in that n is 2.

23. ADC, according to any one of claims 1 to 3 and 11 to 20, characterized in that n is 3.

24. ADC, according to any one of claims 1 to 4 and 9 to 20, characterized in that n is 4.

25. Antibody-drug conjugate (ADC) of Formula (II): hcx (II) or a salt thereof, characterized in that: n is an integer from 1 to 8, and Ab represents an antibody that binds to DLL3 (“DLL3 antibody”). 26.ADC, according to claim 25, characterized in that ADC is Formula (II-A) Petition 870250084316, dated 09 / 18 / 2025, p. 409 / 503 11 / 21 (HA) or a salt thereof.

27. ADC, according to claim 25, characterized in that ADC is Formula (II-B) (HB) or a salt thereof.

28. Antibody-drug conjugate (ADC) of Formula (A): Petition 870250084316, dated 09 / 18 / 2025, p. 410 / 503 12 / 21 characterized in that each thick shaded line represents a chain of an antibody that binds to DLL3 (the DLL3 antibody), the sulfurs represented are cysteine ​​residues (optionally C226 and / or C229) of the DLL3 antibody and X represents the structure below or a salt thereof: where the wavy line represents the point of attachment to the remainder of the ADC Petition 870250084316, dated 09 / 18 / 2025, p. 411 / 503 13 / 21 of Formula (A). 29.Antibody-drug conjugate (ADC) of Formula (B): the VV (B), characterized in that wherein each thick shaded line represents a chain of an antibody that binds to DLL3 (DLL3 antibody), the CH2CH2CH2CH2NH cluster represented is derived from a lysine residue (optionally any one or more of K246, K248, K288, K290 or K317 according to EU numbering) of the CH2 domain of the DLL3 antibody, and X represents the structure below or a salt thereof: Petition 870250084316, 18 / 09 / 2025, p. 412 / 503 14 / 21 HO. ^0 where the wavy line represents the connection point for the remainder of the ADC of Formula (B).

30. ADC, according to claim 29, characterized in that the DLL3 antibody comprises an amino acid sequence as set forth in SEQ ID NO:4 and in which the lysine residue is the 150th amino acid residue of SEQ ID NO:4 (e.g., K248 according to EU numbering). 31.ADC, according to claim 29, characterized in that the DLL3 antibody comprises an amino acid sequence as set forth in SEQ ID NO:5 and in that the lysine residue is the 150th amino acid residue of SEQ ID NO:5 (e.g., K248 according to EU numbering).

32. ADC, according to claim 29, characterized in that the DLL3 antibody comprises an amino acid sequence as set forth in SEQ ID NO:10 and in that the lysine residue is the 152nd amino acid residue of SEQ ID NO:10 (e.g., K248 according to EU numbering).

33. ADC, according to any one of claims 28 to 32, characterized in that X represents the structure below or a salt thereof: Petition 870250084316, dated 09 / 18 / 2025, p. 413 / 503 15 / 21 where the wavy line represents the connection point to the rest of the ADC of Formula (A) or (B). 34.ADC, according to any one of claims 28 to 32, characterized in that X represents the structure below or a salt thereof: wherein the wavy line represents the point of attachment to the remainder of the ADC of Formula (A) or (B).

35. ADC, according to any one of claims 25 to 34, Petition 870250084316, dated 09 / 18 / 2025, p. 414 / 503 16 / 21 characterized in that the DLL3 antibody comprises: (1) a CDR1, CDR2 and CDR3 of a variable heavy chain (VHH) antibody-only domain, wherein the VHH comprises an amino acid sequence as set forth in SEQ ID NO:14, 15 or 16; or (2) at least one VH, wherein the at least one VH comprises CDR1, CDR2 and CDR3, and wherein: (i) CDR1 comprises an amino acid sequence as set forth in SEQ ID NO:1 or 7; (ii) CDR2 comprises an amino acid sequence as set forth in SEQ ID NO:2 or 8; and (iii) CDR3 comprises an amino acid sequence as set forth in SEQ ID NO:3 or 9. 36.A DC, according to any one of claims 25 to 35, characterized in that the DLL3 antibody comprises: (a) a CDR1 as set forth in SEQ ID NO: 1; a CDR2 as set forth in SEQ ID NO: 2; and a CDR3 as set forth in SEQ ID NO: 3; or (b) a CDR1 as set forth in SEQ ID NO: 7; a CDR2 as set forth in SEQ ID NO: 8; and a CDR3 as set forth in SEQ ID NO:

9.

37. A DC, according to any one of claims 25 to 36, characterized in that the DLL3 antibody comprises a VH comprising the amino acid sequence as set forth in any one of SEQ ID NOs: 14-16.

38. A DC, according to any one of claims 25 to 37, characterized in that the DLL3 antibody further comprises a constant domain of human IgG.

39. ADC, according to any one of claims 25 to 38, characterized in that the DLL3 antibody further comprises an Fc fragment. 40.ADC, according to claim 38, characterized in that a human IgG is a human IgG1.

41. ADC, according to claim 39, characterized in that the Fc fragment comprises a homodimer of an amino acid sequence as set forth in SEQ ID NO:

17.

42. ADC, according to any one of claims 25 to 41, characterized in that the DLL3 antibody comprises at least one unique VHH domain.

43. ADC, according to any one of claims 25 to 42, characterized in that the DLL3 antibody comprises two unique VHH domains, each of which is conjugated to a chain of an Fc fragment.

44. ADC, according to any one of claims 25 to 43, characterized in that the DLL3 antibody comprises a homodimer of an amino acid sequence as set forth in any one of SEQ ID NO: 4, 5 or 10. 45.ADC, according to any one of claims 25 to 27 and 35 to 44, characterized in that n is 1.

46. ADC, according to any one of claims 25 to 44, characterized in that n is 2.

47. ADC, according to any one of claims 25 to 27 and 35 to 44, characterized in that n is 3.

48. ADC, according to any one of claims 25 to 28 and 35 to 44, characterized in that n is 4.

49. Pharmaceutical composition characterized in that it comprises one or more ADCs, as defined in any one of claims 1 to 48, and a pharmaceutically acceptable carrier.

50. Pharmaceutical composition according to claim 49, characterized in that the composition is characterized by a drug-antibody ratio (“DAR”) of about 1 to about 8.

51. Pharmaceutical composition according to claim 50, characterized in that the DAR is about 1 to about 2. 52.Pharmaceutical composition, according to claim 50 or 51, characterized in that the DAR is about 1.1, about 1.2, about Petition 870250084316, dated 09 / 18 / 2025, p. 416 / 503 18 / 21 of 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9 or about 2.

53. Pharmaceutical composition, according to claim 50, characterized in that the DAR is from about 2 to about 4.

54. Pharmaceutical composition, according to claim 50 or 53, characterized in that the DAR is about 2, about 2.1, about 2.2, about 2.4, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, about 2.9, about 3, about 3.1, about 3.2, about 3.3, about 3.4, about 3.5, about 3.6, approximately 3.7, approximately 3.8, approximately 3.9, or approximately 4.55.A method for modulating a DLL3-related immune response in a subject, characterized in that it comprises administering to the subject the ADC, as defined in any one of claims 1 to 48, or the pharmaceutical composition, as defined in any one of claims 49 to 54, such that an immune response is modulated in the subject.

56. A method for treating cancer in a subject, characterized in that it comprises administering to the subject the ADC, as defined in any one of claims 1 to 48, or the pharmaceutical composition, as defined in any one of claims 49 to 54, wherein the cancer is DLL3-positive or overexpressed.

57. A method according to claim 56, characterized in that the cancer is selected from lung cancer, neuroendocrine carcinoma, and colorectal cancer.

58. A method according to claim 56 or 57, characterized in that the cancer is SCLC or LCNEC. 59.Use of ADC, according to any one of claims 1 to 48 or pharmaceutical composition, according to any one of claims 49 to 54, characterized in that it is in the manufacture of a medicament for the diagnosis or treatment of a DLL3-positive cancer. Petition 870250084316, dated 09 / 18 / 2025, pp. 417 / 503 19 / 21 60. ADC, according to any one of claims 1 to 48 or pharmaceutical composition, according to any one of claims 49 to 54, characterized in that it is for use in the treatment of a DLL3-positive cancer.

61. Method for producing ADC, according to any one of claims 1 to 24, characterized in that it comprises the steps of: a) providing a solution comprising the DLL3 antibody; b) bringing the solution of a) into contact with a reducing agent; c) place the solution of b) in contact with a solution comprising the binding drug (1) or a salt thereof: MeO \ , N\ O OH (1) where the ADC is made. 62.Method for producing the ADC, according to any one of claims 25 to 48, characterized in that it comprises the steps of: a) providing a solution comprising the DLL3 antibody; b) bringing the solution of a) into contact with a reducing agent; c) bringing the solution of b) into contact with a solution comprising the binding drug (2): Petition 870250084316, dated 09 / 18 / 2025, pp. 418 / 503 20 / 21. (2), where the ADC is made.

63. Method according to claim 61 or 62, characterized in that the reducing agent is tris(2-carboxyethyl)phosphine (TCEP).

64. Method for producing ADC according to any one of claims 1 to 24, characterized in that it comprises the steps of: a) providing a solution comprising the antibody DLL3; b) bringing the solution of a) into contact with an affinity peptide conjugated to a thiophenol activation moiety; c) bringing the solution of b) into contact with a solution comprising the ligand drug (1) or a salt thereof: where the ADC is made.

65. Method for producing the ADC according to any one of claims 25 to 48, characterized in that it comprises the steps Petition 870250084316, dated 09 / 18 / 2025, p.419 / 503 21 / 21 of: a) providing a solution comprising the antibody DLL3; b) placing the solution of a) in contact with an affinity peptide conjugated to a thiophenol activation fraction; c) placing the solution of b) in contact with a solution comprising the ligand drug (2): where the ADC is made.

66. Method according to claim 64 or 65, characterized in that the affinity peptide is a peptide of SEQ ID NO:

6.

67. Method according to any one of claims 64 to 66, characterized in that the affinity peptide conjugated to a thiophenol activation fraction is:

Images