Abstract 2618: BCG017, a bispecific ADC targeting PTK7 and EGFR exhibits anti-tumor efficacy in PDX models

Abstract EGFR is a favored target in various cancer therapies. However, EGFR-based treatments have been challenged by drug resistance and cytotoxicity. Targeting EGFR with an antibody-drug conjugate (ADC) is a promising new therapeutic strategy to address the drug resistance, due to the potent killing effects of the payload. Furthermore, we hypothesized that development of a bispecific ADC (bsADC) targeting EGFR and another tumor-associated antigen (TAA) might improve the tumor selectivity, thereby limiting the on-target off-tumor toxicity. One such TAA candidate is PTK7, which belongs to the same receptor tyrosine kinase family as EGFR, and is co-expressed with EGFR in multiple types of solid tumors, including lung, esophageal, head and neck, and colon cancers. Herein, we developed a fully human anti-human PTK7 EGFR bsAb using our proprietary common light chain RenLite® mouse platform and knobs-into-holes technology. The anti-PTK7 EGFR bsAb demonstrates good purity by SEC-HPLC, and can cross-react with human and cynomolgus monkey antigens with favorable affinity. The PTK7 x EGFR bsAb demonstrated higher binding to various types of cancer cell lines, as well as enhanced internalization in vitro compared with PTK7 parental antibody. Next, the bsAb was conjugated with monomethyl auristatin E (MMAE) to generate an anti-PTK7 x EGFR bsADC, BCG017, with a drug-to-antibody ratio of approximately 4. BCG017 demonstrated superior anti-tumor activity compared to benchmarks and its PTK7 parental ADC in cell-derived non-small-cell lung cancer (NSCLC) xenografts, and showed enhanced anti-tumoractivity when compared to benchmark ADCs and parental ADCs in patient-derived breast and pancreatic ductal adenocarcinoma xenograft models. These results suggest that BCG017 have the potential to be a novel therapeutic alternative for PTK7 and EGFR co-expressing tumors. Citation Format: Sufei Yao, Chengzhang Shang, Zhuolin Li, Gao An, Chaoshe Guo, W. Frank An, Yi Yang. BCG017, a bispecific ADC targeting PTK7 and EGFR exhibits anti-tumor efficacy in PDX 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 2618.