Abstract 5737: Evaluation of the relationship between target expression and in vivo anti-tumor efficacy of AZD9592, an EGFR/c-MET targeted bispecific antibody drug conjugate

Abstract AZD9592 is a bispecific antibody drug conjugate (ADC) designed to deliver a topoisomerase 1 inhibitor (TOP1i) cytotoxic payload (AZ14170133) to tumor cells. AZD9592 selectively binds to epidermal growth factor receptor (EGFR) and c-MET, two cell surface receptors highly expressed in solid tumors including non-small-cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC). Here we evaluate the pharmacodynamic activity of the TOP1i payload delivery by AZD9592 in an NSCLC-derived xenograft model using immunohistochemistry (IHC) approaches. Treatment-induced DNA double-strand breaks (DSB) and apoptotic cell death were measured using γH2AX, phospho-RAD-50 (pRAD50), and cleaved-caspase-3 (CC3) across increasing exposure to AZD9592. Furthermore, we report in vivo antitumor efficacy of AZD9592 in a panel of NSCLC and HNSCC patient-derived xenograft (PDX) models that were characterized for somatic tumor alterations, including oncogenic driver mutations in EGFR, tumor cell expression of EGFR and c-MET by IHC and deep-learning based image analysis, and targeted proteomics by mass spectrometry. Results demonstrate dose-dependent increases in pRAD50 and γH2AX upon treatment with AZD9592, signifying induction of DNA damage. Increased CC3 and reduced tumor volume (TV) in all treatment groups compared with control groups supports that AZD9592 induces tumor cell death due to formation of DNA DSB. In PDX experiments, tumor growth inhibition (TGI), defined as ≥30% reduction in TV from baseline after a single dose of AZD9592 8 mg/kg, was observed in 73% (16/22) of EGFR mutant NSCLC models. The models evaluated included tumors with or without prior exposure to EGFR tyrosine kinase inhibitors, and harboring diverse mutational profiles and heterogeneous expression levels of EGFR and c-MET. In EGFR wildtype NSCLC and HNSCC PDX, TGI was observed in 60% (12/20) and 44% (4/9) of models, respectively. IHC demonstrated an association of target expression and response to treatment, suggesting a potential predictive feature of response in tumors with elevated antigen expression. Targeted proteomics demonstrated an association between the expression of SLFN11, a known TOP1i sensitivity marker, and treatment response. Collectively, these results support the hypothesized mechanism of action of AZD9592: TOP1i induced tumor cell death due to formation of DNA DSB, and suggest opportunities in the treatment of tumors with a range of molecular features. AZD9592 is currently in a Phase 1 clinical trial in advanced solid malignancies. Citation Format: Lara McGrath, Ying Zheng, Simon Christ, Christian C. Sachs, Sihem Khelifa, Claudia Windmüller, Steve Sweet, Yeoun Jin Kim, Daniel Sutton, Michal Sulikowski, Arthur Lewis, Ivan Inigo, Nicolas Floch, Edward Rosfjord, Fernanda Arnaldez, Frank Comer. Evaluation of the relationship between target expression and in vivo anti-tumor efficacy of AZD9592, an EGFR/c-MET targeted bispecific antibody drug conjugate. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5737.