A phase II multicenter study of enfortumab vedotin with or without pembrolizumab in rare genitourinary tumors (E-VIRTUE).

TPS4628 Background: Enfortumab vedotin (EV) is an antibody-drug conjugate (ADC) targeting nectin-4 with a monomethyl auristatin E (MMAE) payload, a potent microtubule inhibitor. It is standard of care (SOC) in metastatic urothelial carcinoma in combination with pembrolizumab in untreated patients and as monotherapy in post-chemotherapy, post-immune checkpoint blockade (ICB) patients. Nectin-4 expression has been retrospectively observed in 66.7-100% of urinary tract adenocarcinoma, 70-100% of urinary tract squamous cell carcinoma (SCC) (Case et al., 2022; Hoffman-Censits et al., 2021) and 36% of testicular germ cell tumors (GCTs) (The Human Protein Atlas). Metastatic urinary tract adenocarcinoma and SCC, and treatment refractory GCTs do not have an established SOC. Given the known nectin-4 expression, we hypothesize that EV with or without pembrolizumab will be active in these rare GU tumors. Methods: E-VIRTUE is an open-label, non-randomized, Phase 2 multicenter study. Eligible patients must have locally advanced or metastatic urinary tract pure adenocarcinoma, urinary tract pure SCC or refractory GCTs and have measurable disease by RECIST 1.1. Patients may have received any number of lines of prior systemic therapy except EV or other MMAE-based ADCs, and GCT patients must be refractory to all curative SOC treatments. Each histology will have an ICB-naïve and post anti-PD-1/PD-L1 ICB cohort: ICB-naïve patients will be given EV 1.25 mg/kg (maximum 125 mg) on Days 1 and 8 and pembrolizumab 200 mg on Day 1 of 21-day cycles, and post ICB patients will be given EV 1.25 mg/kg (maximum 125 mg) on Days 1, 8 and 15 of 28-day cycles. EV will be given for up to 5 years and pembrolizumab will be given for up to 2 years, or until progressive disease (PD) or unacceptable toxicity. Patients who stop pembrolizumab after achieving a complete response may resume it for 1 year after developing PD. The primary objective is to evaluate the objective response rate (ORR) in all cohorts. Secondary objectives include safety, progression-free survival (PFS) and overall survival (OS). The initial 6 cohorts will each be evaluated with exploratory intent. With 10 patients in each cohort, an exact binomial test with a 10% one-sided significance level will have 85.3% power to detect the difference between a very low (5%) ORR and a higher (30%) ORR. If there are ≥2/10 objective responses in any cohort, activity will be demonstrated. Additional histologies may be added after nectin-4 data emerges to justify their inclusion. Exploratory objectives include estimating the level of nectin-4 expression for each histology, performing DNA and RNA sequencing of tumor and blood samples, and observing changes in levels of circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) with treatment and disease status. Clinical trial registration NCT06041503. Clinical trial information: NCT06041503 .