Study EV-103 Cohort H: Antitumor activity of neoadjuvant treatment with enfortumab vedotin monotherapy in patients with muscle-invasive bladder cancer who are cisplatin-ineligible.

Abstract

4582 Background: Up to 25% of all patients (pts) diagnosed with urothelial cancer present with muscle-invasive disease for whom the risk of progression or metastasis is substantial. Neoadjuvant chemotherapy prior to radical cystectomy and pelvic lymph node dissection (RC+PLND) has been shown to prolong overall survival for patients who are cisplatin (cis) eligible. The standard of care for cis-ineligible pts undergoing surgery does not include neoadjuvant therapy. Therefore, safe and effective neoadjuvant therapies are an unmet need for cis-ineligible pts with muscle invasive bladder cancer (MIBC). Enfortumab vedotin (EV) is an antibody-drug conjugate directed to Nectin-4, which is highly expressed in urothelial cancer, and has been shown to benefit previously treated locally advanced or metastatic urothelial cancer pts in phase 2 and 3 trials, including cis-ineligible pts. Methods: Cohort H of the EV-103 phase 1b/2 trial (NCT03288545) enrolled pts with cis-ineligible cT2-T4aN0M0 MIBC who were eligible for RC+PLND and had an ECOG of 0-2. Pts received 3 cycles of neoadjuvant EV (1.25 mg/kg) on Days 1 and 8 of every 3-week cycle prior to RC+PLND. The primary endpoint of the study was pathological complete response rate (pCRR; ypT0N0) by central review. Key secondary endpoints included pathological downstaging (pDS) rate (ypT0,Tis,Ta,T1,N0) and safety. Results from a preliminary analysis are presented. Results: 22 pts were treated. Pts had cT2 (68.2%), cT3 (27.3%), and cT4 (4.5%) tumors. 68.2% pts had predominant urothelial cancer; 31.8% had a mixed histology. 19 pts completed all 3 cycles of EV. 21 underwent RC+PLND, and 1 had a partial cystectomy. 36.4% pts had a pCR. pDS was seen in 50.0% pts. The most common EV treatment-related adverse events (TRAEs) were fatigue (45.5%), alopecia (36.4%), and dysgeusia (36.4%). 18.2% pts had Grade ≥3 EV TRAEs. No surgeries were delayed due to EV administration. 3 pts had Grade 5 AEs while on study that were unrelated to EV; in 2 pts these AEs occurred > 30 days after RC+PLND. Conclusions: Observed pCRR after neoadjuvant EV showed promising activity in cis-ineligible pts with MIBC who have a high unmet need. Adverse events were consistent with the known safety profile of EV. This first disclosure of data supports the ongoing phase 2 and 3 programs evaluating EV in MIBC. Clinical trial information: NCT03288545.