Abstract LB221: Novel peptide linker-based nectin-4 targeting ADC shows improved tolerability with long-lasting anti-tumor efficacy at low doses

Abstract The Araris site-specific and one-step peptide linker conjugation technology generates stable, safe and highly potent ADCs without the need for antibody engineering prior to payload conjugation. We generated an anti-Nectin-4 ADC that shows superior anti-tumor activity and tolerability compared to enfortumab-vedotin (EV) in head-to-head in vitro and in vivo studies. The Araris ADC is based on enfortumab as the targeting antibody and monomethyl auristatin E (MMAE) as payload. Using a peptide linker and site-specific enzymatic conjugation approach, we generated a pure ADC with a drug-to-antibody-ratio (DAR) of approximately 2 and above 98 percent monomeric content. The Araris ADC demonstrated potent cell cytotoxicity similar to the approved enfortumab-vedotin which has a DAR of 4, excellent stability in mouse, cynomolgus and human sera exemplified by the absence of payload deconjugation or linker cleavage while EV showed significant payload deconjugation. Despite high stability, the Araris ADC releases the free active MMAE metabolite at comparable rate to EV in human Cathepsin B or human liver-lysosome (HLL) enzyme cleavage assays. The ADC was also shown to be extremely stable in circulation in pharmacokinetic studies in rodents, leading to an intact ADC exposure profile comparable to the unmodified enfortumab parent antibody. No free payload was detectable in circulation during the 3 week study by LCMS-MRM. In efficacy studies using a SUM-190PT established breast cancer model, a single injection at a dose of 10 ug/kg normalized by payload induced a complete tumor regression lasting for more than 100 days (i.e. a very durable response or tumor eradication). EV administered at the same payload dose showed only a short and transient (until day 20 only) tumor regression with no animal (0/6) reaching a complete response. Despite the higher in vivo exposure and extremely efficient anti-tumor response at low payload doses, there was no increased toxicity but in contrast, overall tolerability was improved, i.e., less neutropenia, skin involvement and signs of toxicity - the skin toxicity being the dose-limiting toxicity of Enfortumab vedotin in humans and rats. Overall, the highest non-severely toxic dose (HNSTD) in 4-week repeat dose rat toxicity studies for the Araris ADC (25 mg/kg) was 5-fold higher compared to the HNSTD (5mg/kg) reported for Enfortumab vedotin. Our data impressively show that the Araris ADC has superior efficacy and durable anti-tumor response even at 3-fold lower payload dose compared to EV. The improved efficacy in mice and tolerability in rates resulted in a 8-fold better TI for the Araris ADC and offers the opportunity to develop a highly efficacious ADC having potentially lower dose-limiting toxicities such as peripheral neuropathy, rashes or neutropenia. Citation Format: Isabella Attinger-Toller, Philipp Probst, Romain Bertrand, Emma Renard, Ramona Stark, Roger Santimaria, Dragan Grabulovski, Bernd Schlereth, Philipp Rene Spycher. Novel peptide linker-based nectin-4 targeting ADC shows improved tolerability with long-lasting anti-tumor efficacy at low doses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB221.