Protease-cleavable Linker Research Articles

A phase 1, first-in-human study of CUSP06, a cadherin-6 (CDH6) -directed antibody-drug conjugate, in patients with platinum-refractory/resistant ovarian cancer and other advanced solid tumors.

TPS3166 Background: Cadherin-6 (CDH6) is a transmembrane glycoprotein involved in cancer metastasis and invasion expressed in various tumor types including ovarian cancer (OC), renal cell carcinoma (RCC), papillary thyroid cancer, cholangiocarcinoma, hepatocellular cancer, glioma, uterine serous carcinoma and non-small cell lung cancer. CUSP06 is an antibody-drug conjugate composed of a human IgG1 monoclonal antibody against CDH6 conjugated with a protease-cleavable linker, T1000, to exatecan, a topoisomerase I inhibitor payload. In preclinical studies, CUSP06 showed CDH6-dependent cell growth inhibition in ovarian cancer cell lines. High CDH6-expressing ovarian and renal CDX and PDX models demonstrated tumor regression after treatment with CUSP06, as did low CDH6-expressing PDX models of other solid tumors. Methods: This is a Phase 1a/1b, open-label, multicenter dose escalation and expansion study to evaluate safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), recommended Phase 2 dose (RP2D), and preliminary efficacy of CUSP06 in patients with platinum-refractory/resistant ovarian cancer (PRROC), advanced RCC and other advanced CDH6-positive solid tumors. Patients with advanced solid tumors previously treated with standard of care systemic therapy, or for whom no standard therapy is available are eligible for enrollment. Prescreening for CDH6 expression will be required for those patients with solid tumors other than PRROC or RCC. CUSP06 will be administered intravenously every 21 days. Phase 1a will follow a standard 3+3 dose escalation design. Phase 1a also includes up to 3 dose enrichment cohorts at doses that have demonstrated safety, each with a maximum of 18 patients, to generate additional safety, PK, PD, and preliminary efficacy data to support an optimized dose for expansion. Phase 1b consists of several dose expansion cohorts including PRROC, RCC, and other CDH6-positive solid tumors, to be enrolled according to Simon's 2-stage design. Mandatory pre- and on-study biopsies in dose expansion cohorts will support a robust exploratory biomarker plan that may include correlation of CDH6 levels with response, and other RNA and protein markers of sensitivity and resistance. The study is currently enrolling in Phase 1a dose-escalation. Clinical trial information: NCT06234423 .

Phase 3 study of disitamab vedotin with pembrolizumab vs chemotherapy in patients with previously untreated locally advanced or metastatic urothelial carcinoma that expresses HER2 (DV-001).

TPS4616 Background: Platinum-based chemotherapy (chemo) has been the standard first-line (1L) therapy for locally advanced or metastatic urothelial carcinoma (la/mUC). Recently, enfortumab vedotin, a nectin-4-directed antibody-drug conjugate (ADC) with a monomethyl auristatin E (MMAE) payload, plus pembrolizumab (pembro) showed improved survival over chemo. Human epidermal growth factor receptor 2 (HER2) expression (immunohistochemistry [IHC] 1+-3+) has been reported in approximately half of all patients (pts) across tumor types, including UC, and is a biomarker that may be associated with poor outcomes. Disitamab vedotin (DV; RC48-ADC) is an investigational ADC comprising a fully humanized HER2-directed monoclonal antibody, disitamab, conjugated to MMAE via a protease-cleavable mc-vc linker. DV elicits antitumor activity through multimodal mechanisms of action, including MMAE-mediated direct cytotoxicity, bystander effect, and immunogenic cell death. DV has shown encouraging activity with a manageable safety profile in pts with la/mUC—as a single agent in a HER2-expressing post-platinum setting (IHC 3+/2+; ORR, 50.5%; median [m]PFS, 5.9 months; mOS, 14.2 months) and in combination with a programmed cell death protein 1 (PD-1) inhibitor in all comers (ORR, 76.0% in treatment-naive pts; 83.3%, 64.3%, and 33.3% in HER2 IHC 3+/2+, IHC 1+, and IHC 0 subgroups, respectively). Improved outcomes observed with an MMAE payload plus PD-1 inhibition across the ADC landscape, along with DV data, provide a robust rationale for this phase 3 trial of DV with pembro in the 1L setting for HER2-expressing la/mUC. Methods: DV-001 (NCT05911295) is an open-label, randomized, multicenter, controlled phase 3 trial evaluating DV with pembro vs chemo in pts with previously untreated HER2-expressing la/mUC. Pts will be randomized 1:1 to Arm A or B. Pts in Arm A will receive DV IV every 2 weeks and pembro IV every 6 weeks. Treatment will continue until disease progression or intolerable toxicity; pembro will be administered for a maximum of 18 6-weekly infusions (approximately 2 years). Pts in Arm B will receive platinum-based chemo with gemcitabine IV on Days 1 and 8 of every 3-week cycle, and either cisplatin or carboplatin on Day 1 of every 3-week cycle for 4-6 cycles. Maintenance therapy with avelumab after completion of chemo may be given to eligible pts where approved and available. Pts must have previously untreated la/mUC, measurable disease per RECIST v1.1, ECOG PS of 0-2 and must be eligible for platinum-based chemo. HER2 expression must be determined using the VENTANA 4B5 HER2 IHC Assay centrally and using the most recent archival or fresh tumor sample. Primary endpoints include PFS per blinded independent central review and OS. Enrollment is ongoing in the US, Canada, and Australia and is planned globally. Clinical trial information: NCT05911295 .

Adjuvant or rescue disitamab vedotin (RC48-ADC) for high-risk non-muscle invasive bladder cancer with HER2 overexpression: A phase II multi-center study.

TPS4625 Background: Non-muscle invasive bladder cancer (NMIBC) comprises approximately three-quarters of newly diagnosed cases of bladder cancer. Based on the risk of disease progression, NMIBC is categorized into low, intermediate, and high risk, with high-risk NMIBC patients facing a 5-year disease progression rate of up to 40%. The current standard treatment for high-risk NMIBC involves transurethral resection of the bladder tumor (TURBT) combined with intravesical Bacillus Calmette-Guérin (BCG) instillation as adjuvant therapy. In cases of BCG instillation treatment failure, the standard approach is radical cystectomy. Multiple studies have reported HER2 positivity in 20-44% of NMIBC cases, and HER2 overexpression (immunohistochemistry ≥2+) is closely linked to the progression and adverse prognosis of bladder cancer. Consequently, HER2 may serve as a novel therapeutic target for bladder cancer. Disitamab Vedotin (DV; RC48-ADC) is an antibody-drug conjugate (ADC) comprising a fully humanized HER2-directed monoclonal antibody conjugated to monomethyl auristatin E (MMAE) via a protease-cleavable mc-vc linker. Results from a Phase II clinical trial (NCT03507166) suggest that Disitamab Vedotin exhibits favorable efficacy and safety in HER2-positive metastatic urothelial carcinoma patients who have previously failed chemotherapy. This clinical trial aims to investigate the efficacy and safety of RC48-ADC as adjuvant or rescue therapy for high-risk NMIBC with HER2 overexpression and to explore molecular biomarkers predicting the efficacy of RC48-ADC. Methods: This multicenter, Phase II clinical trial will enroll two cohorts: Cohort A, consisting of 52 patients undergoing first-line adjuvant therapy, and Cohort B, with 25 patients receiving rescue therapy after BCG instillation failure, both exhibiting HER2 overexpression in high-risk NMIBC. Following the Simon two-stage optimal design, the first stage will involve enrolling 19 patients in Cohort A and 12 patients in Cohort B. After safety and baseline assessments, both cohorts will undergo six cycles of treatment with RC48-ADC (120 mg intravenous infusion every two weeks), totaling 12 weeks of treatment. Primary endpoints include safety, 12-month recurrence-free rate (Cohort A), and 3-month clinical complete response rate (Cohort B). Secondary endpoints encompass the 6-month recurrence-free rate (Cohort A), duration of response (Cohort B), recurrence-free survival, progression-free survival, overall survival, and quality of life (assessed through eEuroQoL EQ-5D and FACT-BI). Additionally, exploratory endpoints will investigate the relationship between biomarkers in tumor tissues, blood, and urine, and treatment efficacy. Clinical trial information: NCT05996952 .

Phase 1 study of ZV0203, a first in class pertuzumab ADC, in patients with HER2 positive advanced solid tumors.

e15004 Background: ZV0203, a first in class (FIC) pertuzumab antibody-drug conjugate (ADC), targets HER2 positive tumor cells with tubulin inhibitor DUO5 as its payload via a stable and protease-cleavable valine-citrulline linker. In preclinical studies, ZV0203 demonstrated superior antitumor activity compared to Kadcyla in multiple tumor cell line xenograft models with no noticeable toxicity. GLP toxicity studies indicated that ZV0203 was well tolerated with an estimated therapeutic index of 35. Methods: This was an open-label, multicenter, phase 1, dose-escalation study in patients (pts) with HER2+ advanced solid tumors. Primary objectives were safety, tolerability and RP2D. Secondary objectives included PK, immunogenicity and preliminary clinical efficacy. ZV0203 was administered intravenously Q3W on a 21-day cycle. An accelerated titration design was used for the 0.3 and 0.6 mg/kg doses, followed by a 3+3 design for 1.2, 1.8, 2.7 and 3.6 mg/kg dose levels. Results: As of January 18, 2024, 15 pts with solid tumors (breast [11], colorectal [2], gastric [1], lung [1]) were enrolled across doses of 0.3-3.6 mg/kg with a median age of 52 years old (range 35-65), of which 9 pts received prior HER2-targeted therapy (trastuzumab ± pertuzumab) and 14 pts completed 21-day DLT assessment (0.3 mg/kg and 0.6 mg/kg [1 each], 1.2 mg/kg, 1.8 mg/kg, 2.7 mg/kg and 3.6mg/kg [3 each]) with no DLT incidence. Treatment-related adverse events (TRAE) occurred in 14 (93.3%) pts. The most frequent TRAEs were corneal epitheliopathy [9], elevated liver enzymes [6], dry eyes [6], neutropenia [4], anemia [4], leukopenia [3], and proteinuria [3], and most were grade 1-2 in severity. 5 pts experienced grade 3 TRAEs: lymphocytopenia (1.8mg/kg [1]) , corneal epitheliopathy (3.6 mg/kg [1]) and blurred vision (2.7 mg/kg [2], 3.6 mg/kg [1]), which were manageable during treatment. No unexpected safety signals were reported. TRAEs led to 13.3% (2/15) treatment discontinuation. Among 14 pts evaluated, 5 pts achieved a best tumor response of PR; 4 pts had SD; 1 pt had Non-CR/Non-PD per RECIST v1.1. Thus, disease control rate was 71.4% (10/14). PK results demonstrated that the PK profile of total antibody was similar to that of ZV0203 ADC, whose systematic exposure increased in a dose-dependent manner and remained stable after repeated administration. Concentration of DUO5 remained scarce, suggesting good stability of ZV0203. Conclusions: ZV0203 was well tolerated and showed clinically encouraging anti-tumor activity in heavily pretreated pts with HER2 positive cancer. Clinical trial information: NCT05423977 .

CLARITY-PanTumor01: A phase 2 trial of the claudin 18.2-specific antibody-drug conjugate AZD0901 (CMG901) in patients with CLDN18.2-expressing advanced solid tumors.

TPS3163 Background: Gastric/gastroesophageal junction (G/GEJ) and pancreatic cancer are associated with poor outcomes and high unmet need. Claudin 18.2 (CLDN18.2) is highly expressed in gastric, esophageal, and pancreatic ductal adenocarcinoma (PDAC), and is a clinically validated target. AZD0901 is a potential first-in-class antibody-drug conjugate (ADC) comprising a humanized anti-CLDN18.2 IgG1 antibody conjugated via a protease-cleavable linker to monomethyl auristatin E (MMAE), a cytotoxic microtubule-disrupting agent. Interim results from the ongoing, first-in-human, Phase 1 trial of AZD0901 monotherapy in patients with G/GEJ cancer (NCT04805307) who were refractory to and/or intolerant of standard therapies demonstrated promising efficacy and a manageable safety profile. Here we describe an ongoing, Phase 2 study of AZD0901 in patients with CLDN18.2-expressing advanced solid tumors, including G/GEJ cancer and PDAC. Methods: This open-label, multicenter study (NCT06219941) comprises multiple substudies. Substudy 1 is recruiting patients with human epidermal growth factor receptor 2 (HER2)-negative, CLDN18.2-expressing G/GEJ cancer with ≤2 prior lines of therapy for unresectable or metastatic disease, who are randomized 1:1 to receive AZD0901 1.8 or 2.2 mg/kg intravenous (IV) every 3 weeks (Q3W). Substudy 2 is recruiting patients with previously untreated CLDN18.2-expressing metastatic PDAC to receive AZD0901 (up to 2.2 mg/kg IV Q3W) and either a combination of 5-fluorouracil 2400 mg/m2 IV on Days 1 and 2 Q2W, leucovorin 400 mg/m2 or l-leucovorin 200 mg/m2 IV on Days 1 and 2 Q2W, and irinotecan 150 or 180 mg/m2 or nanoliposomal irinotecan 50 mg/m2 IV on Day 1 Q2W (Arm 1), or gemcitabine 1000 mg/m2 IV on Days 1 and 8 Q3W (Arm 2), per investigator’s choice. Treatment continues until disease progression, unacceptable toxicity, or withdrawal of consent. Eligible patients are aged ≥18 years with histologically confirmed, unresectable or metastatic disease, ≥1 measurable lesion per Response Evaluation Criteria in Solid Tumours (RECIST) v1.1, and Eastern Cooperative Oncology Group performance status 0–1. Key exclusion criteria include unstable and/or active peptic ulcer disease or digestive tract bleeding, ascites requiring drainage, central nervous system metastases, and prior exposure to an MMAE-based ADC or CLDN-18.2-targeted agents other than an anti-CLDN18.2 targeted monoclonal antibody. Primary endpoints include safety, tolerability, and objective response rate per RECIST v1.1. Secondary endpoints include overall survival, progression-free survival, duration of response, disease control rate, best change in target lesion size, pharmacokinetics, immunogenicity, and pharmacodynamics. Recruitment began in December 2023, and sites across Australia, Asia, Europe, and North America will enroll patients. Clinical trial information: NCT06219941 .

Targeting CD19-positive lymphomas with the antibodydrug conjugate loncastuximab tesirine: preclinical evidence of activity as a single agent and in combination therapy.

Antibody-drug conjugates (ADC) represent one of the most successful therapeutic approaches introduced into clinical practice in the last few years. Loncastuximab tesirine (ADCT-402) is a CD19-targeting ADC in which the antibody is conjugated through a protease cleavable dipeptide linker to a pyrrolobenzodiazepine dimer warhead (SG3199). Based on the results of a phase II study, loncastuximab tesirine was recently approved for adult patients with relapsed/refractory large B-cell lymphoma. We assessed the activity of loncastuximab tesirine using in vitro and in vivo models of lymphomas, correlated its activity with levels of CD19 expression, and identified combination partners providing synergy with the ADC. Loncastuximab tesirine was tested across 60 lymphoma cell lines. It had strong cytotoxic activity in B-cell lymphoma cell lines. The in vitro activity was correlated with the level of CD19 expression and intrinsic sensitivity of cell lines to the ADC's warhead. Loncastuximab tesirine was more potent than other anti-CD19 ADC (coltuximab ravtansine, huB4-DGN462), although the pattern of activity across cell lines was correlated. The activity of loncastuximab tesirine was also largely correlated with cell line sensitivity to R-CHOP. Combinatorial in vitro and in vivo experiments identified the benefit of adding loncastuximab tesirine to other agents, especially BCL2 and PI3K inhibitors. Our data support the further development of loncastuximab tesirine for use as a single agent and in combination for patients affected by mature B-cell neoplasms. The results also highlight the importance of CD19 expression and the existence of lymphoma populations characterized by resistance to multiple therapies.

Abstract PO4-18-11: Phase 1 study of the tissue factor-targeting antibody-drug conjugate XB002 in patients with advanced solid tumors (JEWEL-101): Design of the triple-negative and hormone receptor-positive breast cancer expansion cohorts

Abstract Background: Tissue factor (TF) is a transmembrane protein that functions as a factor VIIa receptor, initiating the extrinsic coagulation cascade. TF is aberrantly expressed in multiple solid tumors, including breast cancer (BC), and its expression is associated with disease progression and poor prognosis (van den Berg et al. Blood 2012). Microtubule-targeting agents are a cornerstone of treatment for metastatic BC. XB002 is a novel antibody-drug conjugate (ADC) composed of a high-affinity TF-directed human monoclonal antibody conjugated to the zovodotin linker-payload. Zovodotin consists of an auristatin-based payload and a protease-cleavable linker and is designed to lower off-target deconjugation and improve tolerability compared with other microtubule inhibitor linker-payloads. In preclinical studies, XB002 did not interfere with coagulation and demonstrated antitumor activity with an encouraging safety profile. XB002 is being evaluated in JEWEL-101, an ongoing trial in patients (pts) with advanced solid tumors, including BC. Preliminary results from the dose-escalation stage of JEWEL-101 showed XB002 was well tolerated at multiple dose levels with no bleeding events or treatment-related peripheral neuropathy (PN) and low-grade ocular toxicity (Ulahannan et al. ENA 2022). Presented here is the study design of the tumor-specific expansion stage, including triple-negative BC (TNBC) and hormone receptor-positive BC (HR+ BC) cohorts. Trial design and statistical methods: JEWEL-101 (NCT04925284) is a multicenter, open-label, phase 1 trial evaluating the safety, tolerability, pharmacokinetics (PK), and antitumor activity of XB002 in advanced solid tumors. Single-agent XB002 at the recommended dose will be assessed in the BC expansion cohorts utilizing Simon’s Two-Stage design. Eligibility criteria: The trial will enroll adult pts with TNBC (ER-/PR-/HER-2-negative or low) and HR+ BC (ER+ and/or PR+ and HER-2-negative or low) into 2 separate cohorts. HER-2 negativity is defined as either HER-2 negative or low by local ISH or IHC assessment. For both cohorts, pts must have received 1–3 lines of prior systemic anticancer therapies for locally advanced or metastatic disease. Pts in the HR+ BC cohort must have received prior endocrine therapy and CDK4/6 inhibitor. All pts must have cytologically or histologically and radiologically confirmed BC that is inoperable, locally advanced, metastatic, or recurrent. Documented radiographic progression during or following their last systemic anticancer therapy is required. All pts must also have measurable disease per RECIST 1.1 by investigator assessment, archival (< 2 years) or fresh tumor tissue, ECOG PS 0 or 1, and adequate organ and marrow function. Pts with grade 1 PN are allowed. Concomitant anticoagulation therapy while receiving XB002 is permitted if clinically indicated. Key exclusions are prior use of TF-targeting or auristatin derivate-based ADC; uncontrolled, significant intercurrent or recent illness, including acute or chronic significant ocular disorders; major surgery within 4 weeks; and corrected QT interval calculated by the Fridericia formula >480 ms per ECG. Specific aims: The primary objective of the expansion stage is to evaluate the preliminary efficacy of XB002 by estimating the objective response rate per RECIST 1.1 as assessed by the investigator. Secondary objectives include safety and tolerability, PK, immunogenicity, progression-free survival, duration of response, and overall survival. Accrual: Up to 28 pts will be enrolled into each BC cohort. Enrollment is planned across sites in the US, Europe, and Asia-Pacific. Contact information: Exelixis Clinical Trials, druginfo@exelixis.com, 1-888-393-5494 Citation Format: Susanna Ulahannan, Melissa Johnson, Mia Weiss, Andrae Vandross, Sofia Vidal-Cardenas, Mustafa Syed, Anthony Tolcher. Phase 1 study of the tissue factor-targeting antibody-drug conjugate XB002 in patients with advanced solid tumors (JEWEL-101): Design of the triple-negative and hormone receptor-positive breast cancer expansion cohorts [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-18-11.

Abstract CT155: Trial in progress: A phase Ia/Ib, an open-label, multicenter study of ZL-1310 to evaluate the safety, tolerability, and pharmacokinetics in subjects with small cell lung cancer

Abstract Background: ZL-1310, a novel antibody-drug conjugate (ADC) targeting delta-like protein 3 (DLL3) with a camptothecin derivative as its payload via a protease-cleavable linker, employs TMALIN® (Tumor Microenvironment Activable LINker-payload) ADC technology platform. DLL3, an inhibitory Notch pathway ligand and a validated target for directed therapy, is highly expressed in more than 80% of patients with small cell lung cancer (SCLC) and also has variable expression in other neuroendocrine (NE) tumors. There remains an unmet medical need for 2nd-line SCLC, as the standard of care chemotherapy has a modest response rate of ~25%. ZL-1310 is designed to minimize payload toxicity and improve anti-tumor effectiveness. Methods: This is an open-label, multiple-dose, phase 1 study of ZL-1310 administered to subjects with relapsed/refractory (r/r) metastatic SCLC who have progressed after at least one platinum-based chemotherapy regimen. The study consists of two parts: Part 1 (dose escalation) and Part 2 (dose expansion). In Part 1, the Bayesian optimal interval (BOIN) design is employed for dose escalation, while in Part 2, patients will be randomized into two cohorts with different doses of ZL-1310 to further define safety and preliminary antitumor activity. The major inclusion criteria are as follows: (1) Subjects must have histologically or cytologically confirmed metastatic or extensive-stage SCLC with no more than 3 prior regimens in the r/r setting. (2) Subjects must have at least one measurable target lesion as defined by RECIST v1.1. (3) Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. The major exclusion criteria include: (1) Prior exposure to DLL3-targeted therapy. (2) Subjects with symptomatic or uncontrolled brain metastasis requiring concurrent treatment, impaired major organ functions, active autoimmune disease, or active infections.Part 1 Dose Escalation is recruiting subjects in the US and China. Citation Format: Afshin Dowlati, Alexander Spira, Xiaodong Shen, Yinjia Fu, Yiyuan Pan, Linda Liu, Renke Zhou, Yi-Long Wu. Trial in progress: A phase Ia/Ib, an open-label, multicenter study of ZL-1310 to evaluate the safety, tolerability, and pharmacokinetics in subjects with small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT155.

Abstract 3128: HRA00184-C004, preclinical characterization of a novel tissue factor-targeted antibody-drug conjugate

Abstract The physiological function of tissue factor (TF) is to initiate coagulation cascade by forming complex with plasma Factor VII after vascular injury. For Tisotumab vedotin (Tivdak), a TF targeting antibody-drug conjugate (ADC) approved for the treatment of cervical cancer, bleeding events were prespecified as adverse effects (AEs) of interest, besides ocular toxicity and peripheral neuropathy (known MMAE payload related AE). In order to mitigate the bleeding risk, a next generation of TF-targeting ADC is developed by Hengrui Pharmaceuticals. HRA00184-C004 is a novel ADC comprising a differentiated TF-targeted antibody (HRP07132) conjugated to a proprietary topoisomerase I inhibitor (Dxh, an exatecan derivative) via a protease-cleavable linker. In contrast to most TF-targeting antibodies, the naked HRP07132 does not interfere the interaction between TF and Factor VII or Factor X, has no impact on coagulation function in prothrombin time and thrombin generation assay, therefore reduced bleeding incidence is expected for HRA00184-C004. Meanwhile, HRA00184-C004 exhibited not only potent growth inhibition against multiple TF-expressing cancer cell lines but also bystander-killing effect in vitro. HRA00184-C004 also displayed robust and sustained anti-tumor activities in the PDAC HPAFII (TF high), TNBC MDA-MB-231 (TF moderate) and NSCLC H358 (TF low) TF-expressing xenograft models. Furthermore, in cynomolgus monkey, HRA00184-C004 is well-tolerated over a 6-week period with 12 mg/kg dosing every 3 weeks with acceptable PK profile. Notably, neither coagulation disorder nor skin rash was observed, which are superior to the historical NHP data reported by Tivdak. In conclusion, with the encouraging efficacy in preclinical study and promising safety profiles in NHPs, HRA00184-C004 has demonstrated the best-in-class potential and is scheduled to advance into clinical development. Citation Format: Hanxiao Ying, Lingfeng You, Ning He, Shaoyu Xu, Pu Pu, Sophie Lin, Jun Feng, Zhe Zhang, Xin Ye, Min Hu, Feng He. HRA00184-C004, preclinical characterization of a novel tissue factor-targeted antibody-drug conjugate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3128.

Abstract 1351: Preclinical characterization of BMS-986288, a novel non-fucosylated (NF) anti-cytotoxic T lymphocyte antigen-4 (anti-CTLA-4) Probody® therapeutic

Abstract Introduction: Blockade of the CTLA-4 pathway with ipilimumab (IPI), alone and in combination with nivolumab (anti-programmed death-1 antibody), has shown clinical benefit in multiple tumor types. However, not all tumors respond to IPI ± nivolumab, and peripheral effects can lead to immune-related adverse events. To enhance the therapeutic index of CTLA-4-directed therapy, a proprietary Probody® therapeutics technology platform was used to develop a modified version of IPI. BMS-986288 is an anti-CTLA-4 antibody that combines a Probody® therapeutic masking peptide and protease-cleavable linker, designed to localize anti-CTLA-4 activity to the tumor microenvironment, with an NF Fc region hypothesized to enhance antigen-presenting cell (APC)-mediated T-cell priming and regulatory T cell (Treg) modulation via increased binding to the FcγRIIIA (CD16) receptor. Here, we present the characterization of the mechanism of action and pharmacodynamic (PD) response of BMS-986288 in preclinical models. Methods: APC-mediated T-cell priming and antigen-specific responses were evaluated in a superantigen model using peripheral blood mononuclear cells (PBMCs) and human CTLA-4 knock-in (KI) mice. Antitumor activity and immune cell population changes were assessed in an MC38 tumor model implanted in human CTLA-4 KI mice. Intratumoral Treg depletion was further investigated using patient-derived dissociated tumor samples as a physiologically relevant model. Peripheral PD effects and tolerability of BMS-986288 were evaluated in a non-human primate (NHP) Ad5 vaccine model. Results: Protease-cleaved BMS-986288 demonstrated enhanced APC-mediated T-cell priming compared with IPI in superantigen-stimulated PBMCs. Similarly, administration of superantigen staphylococcal enterotoxin B (SEB) peptide elicited an increased antigen-specific T-cell receptor (Vβ8+) T-cell response after treatment with cleaved BMS-986288 vs IPI in human CTLA-4 KI mice. In the MC38 tumor-bearing mouse model, BMS-986288 showed enhanced antitumor activity as compared to IPI, with tumor clearance in all mice. Although BMS-986288 enhanced intratumoral CTLA-4+ Treg depletion in the MC38 model, limited Treg depletion was observed in the patient-derived dissociated tumor model with an NF anti-CTLA-4 antibody without the masking peptide, potentially reflecting differences in CTLA-4 expression on human vs mouse Tregs. BMS-986288 reduced PD effects in the peripheral blood compartment and increased tolerability in NHP relative to IPI. Conclusion: BMS-986288 leverages unique characteristics to differentiate it from IPI, enhancing APC-mediated T-cell priming and anti-tumor activity while also reducing peripheral activity in preclinical models. These data support an ongoing phase 1/2 clinical trial of BMS-986288 (NCT03994601) in patients with advanced solid tumors. Citation Format: Amy Jhatakia, Mohammed Nasser, Anandaroop Mukhopadhyay, Kyeongah Kang, Courtni Newsome, Neha Gupta, Remie Gail Z. Mandawe, Felix Findeisen, Jack A. Lohre, Leslie Leung, Yun Wei, Joshua Dobroff, Karen Price, John Engelhardt, Mark Selby, Alan J. Korman, Nicholas Wilson. Preclinical characterization of BMS-986288, a novel non-fucosylated (NF) anti-cytotoxic T lymphocyte antigen-4 (anti-CTLA-4) Probody® therapeutic [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1351.

Abstract 4708: Potency and selectivity of ERBB2-targeting antibody drug conjugates in vitro

Abstract Previously we have reported on the relevance of the joint ProLiFiler and Cancer DataMiner platforms when studying the antitumor efficacy of novel antibody-drug conjugates (ADCs), such as Sacituzumab govitecan. In this study, we use our platforms to investigate and compare the selectivity of two FDA-approved Trastuzumab-based ADCs targeting ERBB2: Kadcyla, the first-in-class ADC employing a microtubule inhibitor bound via a non-cleavable linker, and Enhertu, which combines a topoisomerase inhibitor with a protease-cleavable linker. We performed a cell proliferation and survival assay using the ProLiFilerTM (Reaction Biology) to characterize the in vitro antitumor effects of Enhertu, Kadcyla, and their individual cytotoxins, deruxtecan & mertansine on 160 human cancer cell lines (CLs). The resulting data were uploaded to 4HF´s Cancer DataMiner platform for data analysis. First, we confirmed high potency and limited selectivity of mertansine, as it displayed an IC50 < 250 nM (mean: 27.3 nM) in 95% of cell lines (CLs). A COMPARE analysis confirmed that mertansine data correlated best with those of other microtubule inhibitors in our drug databases (e.g., MMAE, Spearman rho = 0.79, p=9.6E-27). Conversely, a paired analysis showed that CLs were less sensitive to Kadcyla than to mertansine except for CLs overexpressing ERBB2. The 160-CL panel included a total of nine CLs (six mammary, two gastric, one ovarian) with strong ERBB2 overexpression (Affymetrix data >10), mostly associated with ERBB2 gene amplification; seven of them were the most sensitive CLs to Kadcyla (IC50 < 6 nM). Focusing solely on breast cancer cell lines (breast cancer is the approved indication for Kadcyla), we observed a strong correlation between sensitivity to Kadcyla and ERBB2 expression (Spearman r = -0.78, p = 0.003). Interestingly, in line with published data, the ERBB2-overexpressing cell lines SNU-216 (stomach cancer) and JIM-T1 (breast cancer) were less sensitive to Kadcyla. In non-ERBB2-amplified CLs, Kadcyla sensitivity did not correlate with ERBB2 expression levels. Focusing on ERBB2-negative CLs such as hematological CLs, we unexpectedly observed consistent cell inhibition (mean IC50 =33 nM) with Kadcyla, suggesting that the ADC was cleaved, and the payload released into the medium. Overall, this study has demonstrated the relevance of our platforms to study and compare newly developed ADCs. Cytotoxic activities recorded for conjugates and free payloads, along with molecular data for the test cell lines, provides insight in the mode of action of conjugates and their target cell populations and hence can support the development of ADCs. Investigations are underway with Enhertu and its payload deruxtecan, and results will be compared with those obtained for Kadcyla and mertansine. Citation Format: Anne-Lise Peille, Kaja Holtorf, Pablo Anton Garcia, Nadine Obier, Daniel Feger, Thomas Metz, Sebastian Dempe, Heinz-Herbert Fiebig, Jan Ehlert, Vincent Vuaroqueaux. Potency and selectivity of ERBB2-targeting antibody drug conjugates in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4708.

Abstract 1901: Disitamab vedotin, a clinical stage HER2-directed antibody-drug conjugate, shows potent antitumor activity as a monotherapy in preclinical urothelial cancer models

Abstract Disitamab vedotin (DV, RC48-ADC) is an antibody-drug conjugate (ADC) that selectively delivers cytotoxic drug to HER2-expressing cancer cells. DV is composed of disitamab, a HER2-directed monoclonal antibody, and a vedotin linker-payload system, which enables conjugation of the microtubule-disrupting agent monomethyl auristatin E (MMAE) to the antibody via a protease-cleavable linker. The proposed mechanism of action (MOA) of DV occurs through direct cytotoxicity of HER2-expressing tumor cells following internalization of DV and intracellular release of MMAE. DV may also induce antitumor activity through bystander-mediated cytotoxicity of neighboring cells and via the inhibition of HER2 signaling pathways. Moreover, cellular response to MMAE includes the induction of immunogenic cell death and recruitment of immune cells to the tumor site. DV is currently being evaluated globally in subjects with HER2-expressing locally advanced or metastatic urothelial carcinoma (la/mUC) and has gained conditional approval in China following an overall response rate of 50.5% (pooled analysis from studies NCT03507166 and NCT03809013). RNA sequencing data from a large cohort of urothelial cancer patient tumors revealed expression of HER2 in many urothelial tumors; however, the relationship between HER2 expression and efficacy of DV is not well understood. Here, we sought to evaluate the antitumor activity of DV monotherapy in preclinical urothelial cancer models with varying levels of HER2 expression. Multiple patient-derived xenografts (PDX) and patient-derived 3D in vitro urothelial cancer models showed potent antitumor response to DV monotherapy in tumors with varying HER2 expression levels including HER2-low tumors. Overall, these findings support ongoing clinical trials in subjects with HER2-expressing la/mUC and provide scientific rationale to further explore DV monotherapy in HER2-positive and HER2-low urothelial cancer clinical settings. Citation Format: Renee Hein, Kelsi Willis, Gina LoMastro, Suhas Vasaikar, Vinita Gupta, Katie Snead, Sharsti Sandall, Anita Kulukian. Disitamab vedotin, a clinical stage HER2-directed antibody-drug conjugate, shows potent antitumor activity as a monotherapy in preclinical urothelial cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1901.

Abstract 2615: Preclinical development of a next generation antibody drug conjugate (ADC) targeting cMET for treatment of solid tumors

Abstract cMET (mesenchymal-epithelial transition factor), which belongs to the MET family, is a type of receptor tyrosine kinase that is expressed on the surfaces of various epithelial cells. The elevation of cMET can promote the development and progression of multiple cancers. cMET- ADCs have shown promising clinical activity with highest cMET levels, indicating tumor cMET levels may be limited for efficacy. YL211, a novel cMET-ADC was developed by leveraging on MediLink’s tumor microenvironment activable linker-payload platform (TMALIN platform), which could release the payload both in the tumor cell and in the tumor microenvironment. YL211 is comprised of an anti-cMET humanized monoclonal antibody conjugated to a novel topoisomerase 1 inhibitor via a protease-cleavable linker. The novel linker-payload and site-specific conjugation of YL211 results in a homogeneous product with a DAR (Drug-to-Antibody Ratio) of 8. Furthermore, the advancement in linker-payload design has facilitated the development of more hydrophilic ADCs, which exhibit minimal impact on the antibody's characteristics while being less prone to aggregation and showcasing lower systematic clearance. Along with release of the payload in the tumor microenvironment extracellularly, upon binding to cMET on tumor cell surfaces, the antigen-ADC complexes are internalized to lysosomal vesicles and subsequently release the toxic payload. The cytotoxic features drive cell cycle arrest, apoptosis, elevation of PARP/caspase 7 expression, as well as cell death and bystander effect. These findings translated in vivo where YL211 showed superior efficacy in causing tumor regressions and good tolerability in both cell lines and patient-derived xenograft (CDX and PDX) mouse models with both low to high cMET expression levels (H358, CR5088, ect.). The in vivo pharmacokinetics in monkeys showed that YL211 is highly stable with less than 0.1% (molar ratio) payload released in circulation. GLP safety evaluations demonstrated good safety profiles and no off-target toxicity in monkeys. These non-clinical data suggest the stability of the linker in circulation as well as efficient release of the payload in tumors with improved therapeutic window. Taken together, preclinical data suggest that YL211 could be a promising treatment strategy for cMET positive cancer patients. Citation Format: Liang Xiao, Wei Lian, Shuai Song, Qigang Liu, Qing Zong, Sasha Stann, Jiaqiang Cai, Tongtong Xue. Preclinical development of a next generation antibody drug conjugate (ADC) targeting cMET for treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2615.

Abstract 1894: Preclinical development of YL205, a novel NaPi2b-targeting antibody-drug conjugate (ADC) with novel topoisomerase I inhibitor-based linker-payload for treatment of solid tumors

Abstract MediLink’s TMALIN (Tumor Microenvironment Activable LINker-payload) platform incorporates the proprietary protease-cleavable tripeptide linker and novel DNA topoisomerase I inhibitor, enables the release payload both in the tumor cell intracellularly and in the tumor microenvironment extracellularly. YL205 is built on the TMALIN platform, which is comprised of an anti-NaPi2b humanized monoclonal antibody and conjugated in a site-specific manner to yield a uniform DAR 8 product. NaPi2b, encoded by the SLC34A2 gene, is a cell surface sodium-dependent phosphate transporter that is highly expressed in certain cancers, including ovarian, lung, thyroid, and breast cancers, with limited expression in normal tissues. This study evaluated the drug properties, efficacy, safety and pharmacokinetic profiles of YL205 in nonclinical studies. YL205 achieved a high drug-to-antibody ratio through homogeneous conjugation with hydrophilic TMALIN linker-payload, which showed limited impact on the hydrophilicity of the antibody, prolonged the retention time in vivo and eventually enhanced the in vivo potency of ADC. Additionally, YL205 exhibited strong potency, high internalization, potent cytotoxicity and bystander-mediated cell killing toward tumor cells. Significant dose-dependent antitumor activities, including complete tumor regressions with no observable toxicity, were noted in NaPi2b low to high expression ovarian and NSCLC tumor xenograft mouse models. YL205 showed a favorable PK profile evidenced by the overlapping ADC and TAb curves in SD rat and cynomolgus monkey studies. Despite high levels of expression in normal lungs of non-human primates, YL205 exhibited a good safety profile with toxic findings unrelated to normal tissue target expression. Toxicity studies using cynomolgus monkeys showed that YL205 is well tolerated with calculated therapeutic index (TI, HNSTD versus MED) of ﹥80 for repeat dosing. No drug-related adverse findings were found in the lungs, liver or kidneys when tested in all doses. The highly stable nature of TMALIN linker, together with the high potency of the payload, likely mitigates the potential liability of this normal tissue expression. Based on these results, it demonstrates that YL205’s advanced ADC design results in an increased therapeutic margin, and YL205 may help address unmet medical need in patients with NaPi2b-expressing tumors. Citation Format: Liang Xiao, Wei Lian, Qigang Liu, Qing Zong, Shuai Song, Sasha Stann, Jiaqiang Cai, Tongtong Xue. Preclinical development of YL205, a novel NaPi2b-targeting antibody-drug conjugate (ADC) with novel topoisomerase I inhibitor-based linker-payload for treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1894.

Abstract 2601: Potent antitumor activity of anti-HER2 antibody-topoisomerase I inhibitor conjugate based on self-immolative dendritic dimeric-linker

Abstract Antibody-drug conjugates (ADCs) are a rapidly expanding class of anticancer therapeutics, with 14 ADCs already approved worldwide. We developed unique linker technologies for the bioconjugation of drug molecules with controlled-release applications. We synthesized cathepsin-cleavable ADCs using a dimeric prodrug system based on a self-immolative dendritic scaffold, resulting in a high drug-antibody ratio (DAR) with the potential to reach 16 payloads due to its dendritic structure, increased stability in the circulation and efficient release profile of a highly cytotoxic payload at the targeted site. Using our novel cleavable linker technologies, we conjugated the anti-human epidermal growth factor receptor 2 (anti-HER2) antibody, trastuzumab, with topoisomerase I inhibitors, exatecan or belotecan. The newly synthesized ADCs were tested in vitro on mammary carcinoma cells overexpressing human HER2, demonstrating a substantial inhibitory effect on the proliferation of HER2-positive cells. Importantly, a single dose of our trastuzumab-based ADCs administered in vivo to mice bearing HER2-positive tumors, showed a dose-dependent inhibition of tumor growth and survival benefit, with the most potent antitumor effects observed at 10 mg/kg, which resulted in complete tumor regression and survival of 100% of the mice. Overall, our novel dendritic technologies using the protease-cleavable Val-Cit linker present an opportunity for the development of highly selective and potent controlled-released therapeutic payloads. This strategy could potentially lead to the development of novel and effective ADC technologies for patients diagnosed with HER2-positive cancers. Moreover, our proposed ADC linker technology can be implemented in additional medical conditions such as other malignancies as well as autoimmune diseases that overexpress targets, other than HER2. Citation Format: Yulia Liubomirski, Galia Tiram, Anna Scomparin, Samer Gnaim, Sayantan Das, Sachin Gholap, Liang Ge, Eilam Yeini, Omri Shelef, Arie Zauberman, Nir Berger, Doron Kalimi, Mira Toister-Achituv, Christian Schröter, Stephan Dickgiesser, Jason Tonillo, Min Shan, Carl Deutsch, Stanley Sweeney-Lasch, Doron Shabat, Ronit Satchi-Fainaro. Potent antitumor activity of anti-HER2 antibody-topoisomerase I inhibitor conjugate based on self-immolative dendritic dimeric-linker [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2601.

Abstract 3131: Novel CDH17-targeting antibody-drug conjugate exhibits anti-tumor efficacy in preclinical models of gastrointestinal cancers

Abstract Antibody-drug conjugates (ADC) for oncology indications have been developed, however, only few of them are approved for the treatment of gastrointestinal (GI) cancers, which represent as a huge unmet medical need. As such, we developed a novel ADC of which monomethyl auristatin E (MMAE), an antimitotic agent, was conjugated to a cadherin-17 (CDH17)-targeting monoclonal antibody via protease-cleavable peptide valine-citrulline linker. CDH17 is highly restricted to the intestinal adherent junctions which is not accessible in healthy individuals. In contrast, it is overexpressed and becomes reachable in over half of the gastric and pancreatic cancer patients and in more than 95% of patients with colorectal cancer, making it a perfect target for ADC. Our ADC is designed to deliver MMAE specifically to CDH17-expressing tumors to exert the cytotoxic effect of MMAE on cancer cell, mitigating the undesired off-target cytotoxicity. LC/MS analysis revealed that MMAE was conjugated in a drug-to-antibody ratio of 4 with a yield of higher than 75%. ELISA showed that the binding of naked antibody and ADC to CDH17 was comparable (EC50, 0.17 nM & 0.3 nM, respectively), indicating the conjugation process did not affect antigen binding. This ADC also bound to different CDH17-expressing cell lines, including pancreatic AsPC1 and gastric AGS (EC50, 2.1 nM & 1.53 nM, respectively). By labelling the ADC with pH-sensitive fluorescent indicator, we illustrated that ADC internalization only occurred in CDH17+ but not CDH17- cells, suggesting the high specificity of the ADC. Similarly, the ADC showed selective killing on CDH17+ cells (EC50, 0.02-0.5 nM), and the data together proposed a positive correlation between ADC internalization level and its cytotoxicity (R2 = 0.4307). This supported the specificity and safety of the ADC in killing CDH17+ cancer cells only without affecting normal cells. Furthermore, a preliminary in-vivo study on subcutaneous AsPC1 xenograft model demonstrated that the ADC significantly suppressed tumor growth without causing any changes in body weight. Our ADC would potentially be a “First-in-class” ADC for the treatment of GI cancers with minimal adverse systemic toxicity. Further pharmacokinetics, safety, and other IND-enabling studies are underway. Citation Format: Po Yee Wong, Lin He, Kronos Chow, Kwan Wa Wong, Chui Yee O, Dennis Wong, John Moon Luk, Pui-Chi Lo, Kwong Fai Wong. Novel CDH17-targeting antibody-drug conjugate exhibits anti-tumor efficacy in preclinical models of gastrointestinal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3131.

Abstract 3137: Development of AT2604, a highly efficacious ADC targeting alkaline phosphatases ALPP and ALPPL2​

Abstract Placental alkaline phosphatases, ALPP and ALPPL2, are highly homologous, membrane-bound proteins involved in fetal development. Despite having limited expression in normal tissues, they are highly differentiated in tumor cells making them ideal targets for antibody drug conjugate (ADC) development. AT2604 is an ADC that consists of a humanized IgG1 anti-ALPP/ALPPL2 antibody that displays specificity over other human alkaline phosphatases and is cross reactive to NHP ALPPL2 but not to murine ALPPL2. The anti-ALPP/ALPPL2 antibody shows high target binding affinity and internalization into ALPP and ALPPL2 positive cells.​ AT2604 utilizes AxcynCYSTM technology for site-specific conjugation to achieve a highly homogeneous (>97%) DAR4 ADC product. The payload is the clinically validated microtubule disrupting agent monomethyl auristatin E (MMAE) conjugated to the antibody via a protease-cleavable peptide linker approved for ADC use. When evaluated in mouse xenograft models of gastric (NCI-N87) and pancreatic (HPAC) cancer, AT2604 displayed strong tumor growth inhibition (>90%) at 1 mg/kg (QW3 × 2 dosing) in both models. Furthermore, a pre-tox study in non-human primates concluded AT2604 has a HNSTD of 10 mg/kg (QW3 × 3 dosing) and did not exhibit any non-reversible adverse effects; implying that AT2604 possesses an improved safety profile over other vedotin-based ADCs. Taken together, the data supports the continued development of AT2604 towards evaluation in human trials.​ Citation Format: Bryan K. Yeung, Xiao Hui Koh, Wei Li Ling, Weiqi Tan, You Xue Wu, Xi Yun Zhang, Hong Yee Tan, Shao Jun Liu, Chen Zhong, Bin Zou. Development of AT2604, a highly efficacious ADC targeting alkaline phosphatases ALPP and ALPPL2​ [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3137.

Abstract 2616: BCG033, a novel bispecific antibody-drug conjugate targeting PTK7 and TROP2, demonstrates preclinical efficacy against triple-negative breast cancer and other solid tumor xenografts

Abstract Metastatic triple-negative breast cancer (TNBC) patients have poor overall survival, highlighting the need for novel treatments. Although the TROP2-targeting ADC sacituzumab govitecan recently received accelerated approval from the FDA for the treatment of patients with metastatic TNBC, the on-target toxicity of this single-target agent has limited clinical efficacy. We sought to improve the specificity and efficacy of future TNBC-targeted therapies by generating a bispecific antibody-drug conjugate (bsADC) targeting TROP2 and PTK7, another tumor-associated antigen (TAA) that is highly expressed in TNBC and correlates with poor prognosis and metastatic disease. We previously generated fully human antibodies targeting PTK7 and TROP2 from Biocytogen’s fully human, common light chain antibody transgenic RenLite® mice, which were selected such that their monovalent antibodies exhibited reduced internalization profiles for improved tumor selectivity. These antibodies were then constructed into a bispecific antibody targeting PTK7 × TROP2, which demonstrated reactivity to human and cynomolgus monkey antigens and binding to multiple cancer cell lines, including TNBC, with high affinity. PTK7 × TROP2 bsAb also showed enhanced internalization in vitro compared with parental monovalent antibodies. Next, the PTK7 x TROP2 bsAb was conjugated to vcMMAE with a drug-to-antibody ratio (DAR) of 4 to generate a bsADC (BCG033). BCG033-vcMMAE demonstrated superior activity to benchmark and parental ADCs in a cell line-derived xenograft (CDX) TNBC model with low PTK7 expression. Here, we demonstrate that BCG033-vcMMAE ADCs also exhibited superior efficacy to benchmark ADCs in PDX models, including TNBC xenografts and NSCLC xenografts. We next tested the efficacy of the PTK7 x TROP2 bsAb conjugated to BLD1102, Biocytogen’s novel, proprietary linker/payload composed of a DNA Topo I inhibitor payload and a highly hydrophilic protease-cleavable linker, with a DAR of 8. BCG033-BLD1102 showed potent activity in a colorectal cancer PDX model in which benchmark ADCs were inactive, even at high doses. In summary, BCG033 conjugates demonstrate promising preclinical efficacy in vivo, which ultimately could provide a new treatment option for TNBC and other solid tumors expressing PTK7 and TROP2. Citation Format: Sufei Yao, Chengzhang Shang, Gao An, Chaoshe Guo, W. Frk an, Yi Yang. BCG033, a novel bispecific antibody-drug conjugate targeting PTK7 and TROP2, demonstrates preclinical efficacy against triple-negative breast cancer and other solid tumor xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2616.

Abstract 2617: BCG022, a novel HER3 × MET bispecific antibody-drug conjugate (bsADC), demonstrates promising anti-tumor efficacy

Abstract HER3 and MET expression act as bypass resistance mechanisms, conferring resistance to multiple therapeutic agents, such as EGFR TKI treatment. HER3 and MET are also co-expressed at high prevalence in multiple tumor types, including gastric, colorectal, breast, and non-small-cell lung cancer (NSCLC). In addition, HER3 and MET are frequently overexpressed in liver metastases from patients with colorectal cancer, indicating that targeting both targets may provide clinical benefit. We previously reported generation of a fully human bispecific antibody (bsAb) targeting HER3 and MET using RenLite® mice, which contain the full human heavy chain variable domain with a common human kappa light chain to facilitate bispecific antibody assembly. This bsAb demonstrated reactivity to human and cynomolgus monkey antigens and binding to multiple cancer cell lines, including NSCLC, gastric, colorectal, and hepatocellular cancer cell lines. The bsAb also showed enhanced internalization activity compared to parental monovalent antibodies in the NUGC-4 cell line expressing HER3 and MET. Here, we evaluated the efficacy of the bsAb when conjugated to two distinct payloads: vcMMAE and BLD1102, Biocytogen’s novel, proprietary linker/payload system composed of a DNA Topo I inhibitor payload (BCPT02) and a highly hydrophilic protease-cleavable linker. The in vivo efficacy of BCG022-vcMMAE and BCG022-BLD1102 was evaluated in cell-derived NSCLC and gastric cancer xenografts, and in patient-derived gastric and pancreatic xenograft models. Both demonstrated strong anti-tumor activity, with efficacy greater than or comparable to benchmark ADCs. Taken together, these promising preclinical results suggest that the BCG022 bsADC could be a novel treatment for HER3 and MET co-expressing tumors. Citation Format: Zhuolin Li, Chengzhang Shang, Zhenyan Han, Gao An, Chaoshe Guo, W. Frank An, Yi Yang. BCG022, a novel HER3 × MET bispecific antibody-drug conjugate (bsADC), demonstrates promising anti-tumor efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2617.

Abstract 2619: A novel EGFR × HER3-targeting bispecific antibody drug-conjugate, BCG019, demonstrates robust anti-tumor efficacy in preclinical evaluation

Abstract EGFR and HER3 are receptor tyrosine kinases that are highly expressed in multiple epithelial tumors. EGFR point mutations and small insertions within the kinase domain are common in lung cancer. HER3 is overexpressed in patients who are resistant to EGFR-TKI therapy, and is one of the common resistance mechanisms of EGFR and HER2-targeted therapy. We hypothesize that simultaneous targeting of EGFR and HER3 with a bispecific ADC will have the potential to overcome the resistance caused by HER3 after EGFR-targeted therapy and obtain better efficacy than the combination of EGFR monotherapy and HER3 monotherapy. We first generated fully human bispecific antibodies (bsAbs) targeting EGFR and HER3 using RenLite® mice, which contain the full human heavy chain variable domain with a common human kappa light chain to facilitate bispecific antibody assembly. The anti-EGFR × HER3 bsAb demonstrated reactivity to human and cynomolgus monkey antigens and binding to multiple cancer cell lines, including NSCLC, gastric, pancreatic, colorectal, and breast cancer cell lines. The anti-EGFR × HER3 bsAb also showed high internalization activity in cell lines expressing EGFR and HER3. The anti-EGFR × HER3 bsAb was then conjugated with vc-MMAE (valine-citrulline-monomethyl auristatin E) for proof-of-concept studies, as well as BLD1102, Biocytogen’s novel, proprietary linker/payload system composed of a DNA Topo I inhibitor payload (BCPT02) and highly hydrophilic protease-cleavable linker, to generate EGFR- and HER3-targeting bispecific ADC candidates BCG019. In vivo efficacy of the bsADC candidates were evaluated in cell-derived NSCLC and gastric cancer xenografts and in patient-derived gastric and colorectal xenograft models. Both bsADCs showed superior anti-tumor activity when compared to benchmark ADCs. Collectively, these results suggest that our novel anti-EGFR × HER3 bsADC has therapeutic potential for EGFR and HER3 co-expressing tumors. Citation Format: Zhuolin Li, Chengzhang Shang, Gao An, Chaoshe Guo, W. Frank An, Yi Yang. A novel EGFR × HER3-targeting bispecific antibody drug-conjugate, BCG019, demonstrates robust anti-tumor efficacy in preclinical evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2619.