Abstract 1140: Enfortumab vedotin, a Nectin-4 directed ADC, demonstrates compelling tolerability and anti-tumor activity with intravesical instillation in preclinical models of non-muscle invasive bladder cancer

Abstract Enfortumab vedotin (EV) is a monomethyl auristatin E (MMAE) containing antibody-drug conjugate directed to Nectin-4, which is highly expressed in bladder cancers. Preclinically, EV has demonstrated tumor cell-killing by direct cytotoxicity, bystander toxicity, and induction of the hallmarks of immunogenic cell death. In EV-301, a phase 3 clinical study, EV monotherapy showed an overall survival (OS) benefit vs chemotherapy in patients with locally advanced or metastatic urothelial carcinoma (la/mUC) who had previously received platinum-based therapy and a PD-1 or PD-L1 inhibitor (Powles 2021). EV also has encouraging activity in combination with pembrolizumab in previously untreated la/mUC (73% ORR)(Friedlander 2021). Most newly diagnosed bladder cancer cases are non-muscle invasive (Chang 2016; Woldu 2017; Kates 2020; Li 2020). Standard treatment of high risk NMIBC involves transurethral resection of the bladder tumor followed by intravesical (IVES) Bacillus Calmette-Guerin (BCG) or chemotherapy. Although response to BCG is high, many patients recur within 1-5 years (Matulay 2021). For patients unresponsive to BCG, treatment options are limited; radical cystectomy remains the standard of care. Due to the morbidity associated with radical cystectomy there remains a significant unmet need for a safe and effective therapy. We demonstrate that NMIBC have a high Nectin-4 expression pattern by RNA analyses and immunohistochemistry (IHC) similar to la/mUC, using an anti-Nectin-4 antibody (clone M22-321b41.1). The anti-tumor activity of EV was demonstrated in vitro and in vivo in human bladder cancer cells overexpressing Nectin-4. The superiority of EV vs MMAE alone was shown via in vitro pulsed (2hr) exposure cytotoxicity assays mimicking IVES administration. In a luciferase expressing orthotopic xenograft mouse model of NMIBC, EV-mediated anti-tumor activity was confirmed by both bioluminescence imaging of tumor burden and IHC for h-Nectin-4 expressing cancer cells. Tumor uptake of EV was further confirmed by IHC detection of EV in the engrafted tumor cells. Repeat-dose IVES administration of EV was well tolerated in a GLP study with minimal local and no systemic toxicities at doses up to 6-fold the intravenous maximum tolerated dose. Consistent with the lack of systemic toxicities, IVES administration was associated with low systemic absorption (<1% of the dose-normalized ADC Cmax observed in intravenous toxicity studies) and undetectable systemic MMAE. In this preclinical model, increased levels of MMAE in the targeted bladder tissue were associated with increasing the total dose and concentration of EV more than changing either the volume instilled or dwell time. These findings provide evidence to support further investigation of intravesical EV in NMIBC patients. Citation Format: Christopher Carosino, Devra Olson, Katie Snead, Anthony Lee, Lauren Farr, Amit Garg, Christine O'Day, Esther Trueblood, Jennifer Wright, Mark Bieda, Charles Caldwell, Kelly Hensley, Sean Allred, Bernard Liu, Masashi Shimazaki, Sharsti Sandall. Enfortumab vedotin, a Nectin-4 directed ADC, demonstrates compelling tolerability and anti-tumor activity with intravesical instillation in preclinical models of non-muscle invasive bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1140.