Background: Patients (pts) with mUC are in need of novel therapies. Enfortumab vedotin (EV) is an antibody–drug conjugate that delivers a microtubule-disrupting agent to tumors expressing Nectin-4, a protein overexpressed in most urothelial cancers. Preliminary results of the EV-101 study (NCT02091999) suggest EV is active and tolerable at the RP2D of 1.25mg/kg; updated results from pts with mUC treated at RP2D are reported. Methods: Patients with mUC treated with ≥1 prior chemotherapy or who were ineligible for cisplatin received a 30-min infusion of EV on Day 1, 8, and 15 of each 28-day cycle. The primary objective was tolerability; antitumor activity (per RECIST v1.1), assessed by investigators every 8 wk, was a secondary objective. Results: As of 11 Jan 2018, 155 pts with mUC have been enrolled; 112 received EV at RP2D (median age 67 yr [range 24–86]). Bladder was the primary tumor site in 84 pts (75%) and 32 (29%) had liver metastases (LM). Ninety-one pts (81%) received prior platinum chemotherapy; 67 (60%) received ≥2 prior therapies in the metastatic setting, including 84 (75%) who had a checkpoint inhibitor (CPI). Consistent with previous reports, EV was generally well tolerated. Grade ≤2 fatigue (50%) was the most commonly reported treatment-related AE (TRAE). The most common Grade ≥3 AEs, regardless of attribution, were anemia (7%), hyponatremia (6%), urinary tract infection (6%), and hyperglycemia (5%). Four pts experienced a fatal TRAE (respiratory failure, urinary tract obstruction, diabetic ketoacidosis, multi-organ failure). Confirmed CR and PRs were observed in 3 and 34 pts, respectively; ORR = 33% (95% CI 24.7–42.9). Eight unconfirmed PRs were pending assessment. Additionally, ORRs in study subpopulations were 32% (prior CPI, n = 84), 37% (CPI naïve, n = 27), and 26% (LM/prior CPI, n = 23). Overall median DOR was 24.3 wk (95% CI 16.3–47.3) and PFS was 23.1 wk (95% CI 20.1–24.1). Median OS was 12.5 mo (95% CI 8.1–14.8) with 76 pts (68%) censored and OS at 6 mo was 75.1%. However, time-to-event endpoints continue to evolve. Conclusions: Enfortumab vedotin has encouraging ORR and PFS in heavily pretreated pts with mUC, including pts with LM and prior CPI treatment. Survival data awaits maturity. Clinical trial information: NCT02091999