Abstract LB246: Enfortumab vedotin, a nectin-4-directed antibody-drug conjugate, demonstrates compelling antitumor activity in non-muscle invasive bladder cancer models which predicts minimal systemic exposure when administered by intravesical instillation in patients
Authors: Olson Devra , Chia Yen Lin , Iboi Enaharo , Farr Lauren , Burcher Maddy , Lee Anthony , Hensley Kelly , Allred Sean , Wong Abbie , Shimazaki Masashi , Mori Masamichi , Sandall Sharsti , Carosino Christopher 
Published: April 2023

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 and bystander effect and can induce the hallmarks of immunogenic cell death. EV improves survival in adults with previously treated locally advanced or metastatic urothelial carcinoma (la/mUC) and is approved in the US, Europe, Japan, and others. Most newly diagnosed bladder cancer cases are non-muscle invasive (NMIBC). Standard treatment of high-risk NMIBC involves transurethral resection followed by intravesical Bacillus Calmette-Guerin (BCG) or chemotherapy. Although response to BCG is high, recurrence is common, and treatment options for patients with BCG-unresponsive tumors are limited, underscoring the significant unmet need. Previously, we demonstrated compelling preclinical antitumor activity of EV in NMIBC models with a favorable safety profile and minimal systemic exposure. EV-mediated antitumor activity was confirmed in a mouse model of NMIBC by both bioluminescence imaging and IHC for hNectin-4-expressing cancer cells. Following intravesical administration of EV, tumor growth inhibition ranged 46-96% across the dose range tested. Colocalization of EV to Nectin-4-positive tumor tissues was confirmed by IHC in the engrafted tumor cells. Systemic EV exposure in tumor-bearing mice was low, consistent with previous nonclinical studies, supporting that the antitumor activity is driven by local exposure within the bladder. In a repeat-dose GLP toxicology study in rats, no systemic toxicities were observed at intravesical doses up to 6-fold higher than the maximum tolerated IV dose. This lack of systemic toxicities that can occur with IV administration in rats was likely due to minimal systemic exposure of both EV and unconjugated MMAE. Currently, the safety, tolerability, and antitumor activity of intravesical EV are being evaluated in a Phase 1 study in adults with high-risk, BCG-unresponsive NMIBC (EV-104, NCT05014139). The initial dose level for EV-104 was selected to be active and predicted to have minimal systemic absorption based on preclinical and known clinical IV data. Here, we present confirmatory clinical data demonstrating that EV and unconjugated MMAE are undetectable in the bloodstream at the starting dose. These findings confirm the translatability of our nonclinical models and provide evidence that intravesical administration of EV in NMIBC is a promising approach that limits systemic exposure. These data support the potential for a favorable safety and activity profile and warrant continued investigation of intravesical EV in patients with NMIBC.
Citation Format: Devra Olson, Yen Lin Chia, Enaharo Iboi, Lauren Farr, Maddy Burcher, Anthony Lee, Kelly Hensley, Sean Allred, Abbie Wong, Masashi Shimazaki, Masamichi Mori, Sharsti Sandall, Christopher Carosino. Enfortumab vedotin, a nectin-4-directed antibody-drug conjugate, demonstrates compelling antitumor activity in non-muscle invasive bladder cancer models which predicts minimal systemic exposure when administered by intravesical instillation in patients [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 LB246.