Abstract 1891: Preclinical characterization of ADRX-0706: A next-generation anti-Nectin-4 antibody-drug conjugate with improved therapeutic window

Abstract Nectin-4 is a well validated tumor target, which is highly expressed in several solid cancers such as urothelial, head-and-neck, breast, lung, pancreatic, ovarian, and cervical cancer, while expression in normal tissues is limited. A first-generation antibody-drug conjugate targeting Nectin-4, called enfortumab vedotin-ejfv (EV), was granted accelerated FDA approval in 2019 for urothelial cancers, and is currently approved for frontline therapy in cisplatin-ineligible patients with locally advanced or metastatic urothelial carcinoma, providing groundbreaking improvement in patient survival. However, clinical use of EV has also revealed safety-driven limitations, which result in reduced and/or interrupted drug exposures impacting efficacy. To overcome these limitations in therapeutic window and to maximize on the potential of Nectin-4 as a tumor target beyond urothelial cancers, Adcentrx has developed ADRX-0706, a Nectin-4-targeting next-generation ADC with a drug-antibody ratio of 8. ADRX-0706 is comprised of a novel fully human IgG1k monoclonal antibody linked to an optimized tubulin inhibitor payload AP052 through a proprietary cleavable linker. ADRX-0706 has strong binding affinity and selectively induces cytotoxicity in Nectin-4-expressing tumor cells. Importantly, ADRX-0706 is designed to have improved bystander effect, which allows tumor regression even in cases of heterogeneous Nectin-4 expression. This translates to superior in vivo efficacy of ADRX-0706 over EV in multiple mouse xenograft models of other indications beyond bladder cancer. In a mouse clinical trial of patient-derived cervical cancers with a range of Nectin-4 expression levels, ADRX-0706 reaches a 73% ORR. Since peripheral neuropathy is a main platform toxicity for this payload class, ADRX-0706 is assessed in an in vitro co-culture model to evaluate its neurotoxic potential. While EV displays a 75% decrease in neurite outgrowth, ADRX-0706 strikingly has no impact at concentrations up to 1mg/ml, suggesting a lower risk of peripheral neuropathy in humans for ADRX-0706. In preclinical repeat dose toxicology study, ADRX-0706 reaches an HNSTD of 18mg/kg in NHPs well above therapeutic exposures in mouse pharmacology studies, indicating a tremendous increase in the therapeutic index compared to EV. In summary, the highly selective and potent anti-tumor activity in multiple tumor types and wide preclinical therapeutic index of ADRX-0706 support clinical evaluation of this next generation anti-Nectin-4 ADC. ADRX-0706 is currently in a phase 1a/b study (NCT06036121). Citation Format: Andrew M. Hau, Maria Shahmoradgoli, Dong Jun Lee, Wes Sisson, Anna Wang, Peter P. Challita, Erin Nye, Mario M. Kuo, Alexis Mahloch, Monica Leung, Oscar Betancourt, Alexander Chu-Kung, Maojun Guo, Hui Li, Sabine Rottmann, Pia M. Challita-Eid. Preclinical characterization of ADRX-0706: A next-generation anti-Nectin-4 antibody-drug conjugate with improved therapeutic window 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 1891.