Abstract 1565: Design and development of biparatopic antibody-drug conjugates against protein tyrosine kinase 7

Abstract Background: Biparatopic antibodies and antibody-drug conjugates (ADCs) can provide many functional benefits over their traditional monoparatopic counterparts including increased binding, greater cell surface decoration, superior receptor blockade, and enhanced internalization and payload delivery; however, not all antigens are amenable to biparatopic targeting. We sought to leverage our prior knowledge of biparatopic antibody development and our AzymetricTM technology to develop a novel biparatopic ADC against protein tyrosine kinase 7 (PTK7) that could provide a functional enhancement over monoparatopic ADCs. PTK7 is an attractive ADC target due to preliminary clinical activity demonstrated with cofetuzumab peledotin in non-small cell lung cancer, ovarian cancer, and metastatic breast cancer and evidence that PTK7 is overexpressed in other solid tumor indications including esophageal cancer, colorectal cancer, head and neck cancer, and cervical cancer. Materials and Methods: Twenty-nine PTK7-targeting paratopes were isolated from a mouse antibody discovery campaign and paratope pairs were combined into a panel of biparatopic antibodies using AzymetricTM Het_Fc mutations. A high-throughput screen was used to assess the functional properties of these antibodies and to identify the top paratope combinations. ADCs were produced by conjugating the top biparatopic and monoparatopic antibodies to ZD06519, a topoisomerase 1 inhibitor payload used in ZW191, an ADC targeting FRα under evaluation in a phase 1 clinical trial (NCT06555744). ADC activity was investigated in a series of in vitro and in vivo experiments using ovarian, lung, and breast cancer models. Results: Across multiple cancer cell lines with varying PTK7 expression we compared a lead monoparatopic antibody and cofetuzumab with the top biparatopic antibody which demonstrated greater cell surface decoration and better internalization. At clinically relevant doses, the biparatopic ZD06519 ADC was more efficacious than cofetuzumab pelidotin in triple negative breast cancer and lung cancer cell line derived xenograft models. Additional studies of the PTK7 biparatopic ADC in patient-derived xenograft models and a non-human primate tolerability study are planned. Citation Format: Luying Yang, Vincent Fung, Alex Wu, Dunja Urosev, Saki Konomura, Tik Nga Tong, Katina Mak, Elizabeth M. Porter, Diego A. Alonzo, Catrina M. Kim, Janice P. Tsui, Linglan Fu, Lemlem Degefie, Kaylee Wu, Matthew Bonderud, Jamie R. Rich, Stuart D. Barnscher. Design and development of biparatopic antibody-drug conjugates against protein tyrosine kinase 7 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1565.