Primary results of EV-301: A phase III trial of enfortumab vedotin versus chemotherapy in patients with previously treated locally advanced or metastatic urothelial carcinoma.

393 Background: Patients with locally advanced or metastatic urothelial carcinoma (la/mUC) have poor survival following progression after platinum-containing chemotherapy and PD-1/L1 inhibitor regimens. Enfortumab vedotin (EV) is an antibody-drug conjugate directed to Nectin-4, a cell adhesion molecule highly expressed in urothelial carcinoma, with remarkable efficacy observed in a single-arm trial in this setting. This randomized phase III study (EV-301) was performed to confirm these findings. Methods: EV-301 (NCT03474107) is a global, open-label phase III study of EV vs chemotherapy conducted in patients with la/mUC who had received a prior platinum-containing chemotherapy and had disease progression during or after PD-1/L1 inhibitor treatment. Patients were randomized 1:1 to receive EV (1.25 mg/kg) on Days 1, 8, and 15 of each 28-day cycle or investigator choice of standard docetaxel, paclitaxel, or vinflunine chemotherapy. The primary endpoint was overall survival (OS); secondary endpoints included investigator-assessed progression-free survival (PFS), objective response rate (ORR), and disease control rate (DCR) per RECIST v1.1, as well as safety/tolerability. A prespecified interim analysis, which tested OS at an adjusted 1-sided significance level of P = 0.00679, was performed when ≥285 deaths had occurred. The results of this interim analysis are presented here. Results: Overall, 608 patients with la/mUC were randomly assigned to EV (n=301) or chemotherapy (n=307). As of July 15, 2020, 301 deaths had occurred (EV, n=134; chemotherapy, n=167). After an 11.1 mo follow-up, median OS was significantly prolonged by 3.9 mo with EV compared with chemotherapy (median OS: 12.9 vs 9.0 mo, respectively; HR=0.70 [95% CI: 0.56-0.89], 1-sided P =0.001). Additionally, the OS benefit of EV was retained in the majority of prespecified subgroups. Progression-free survival also was improved with EV (5.6 mo) vs chemotherapy (3.7 mo) (HR=0.61 [95% CI: 0.50-0.75]; 1-sided P <0.00001). Both ORR and DCR were significantly higher with EV vs chemotherapy (40.6% vs 17.9% and 71.9% vs 53.4%, respectively; 1-sided P <0.001 each). Rates of treatment-related adverse events (TRAEs; 93.9% vs 91.8%), including serious TRAEs (22.6% vs 23.4%), were comparable between the EV and chemotherapy groups. Rates of grade ≥3 TRAEs were ~50% in both groups; decreased neutrophil count (13.4%) and white blood cell count (6.9%) were more common in the chemotherapy group, and maculo-papular rash (7.4%) was more common in the EV group. Conclusions: EV is the first therapy to show significant survival advantage over standard chemotherapy in patients with treatment-experienced la/mUC. With robust clinical benefit and a tolerable safety profile, EV is a new standard of care for this aggressive disease. Clinical trial information: NCT03474107.