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 (6Suppl): Abstract nr 1901.