Epacadostat plus pembrolizumab in patients with advanced urothelial carcinoma: Preliminary phase I/II results of ECHO-202/KEYNOTE-037.

Abstract

4503 Background: Pembrolizumab (P), a PD-1 inhibitor, is active and well tolerated in platinum-treated, advanced urothelial carcinoma (UC). Epacadostat (E) potently and selectively inhibits indoleamine 2,3-dioxygenase 1 (IDO1), a tryptophan-catabolizing enzyme that suppresses T-cell–mediated immune surveillance. IDO1 overexpression is associated with tumor progression and shortened patient (pt) survival. ECHO-202/KEYNOTE-037 is an open-label, phase I/II study of E + P in pts with advanced tumors. We report phase I/II efficacy and safety outcomes for the UC cohort at an October 29, 2016 data cutoff. Methods: Adult pts with advanced UC, prior platinum therapy (adjuvant or advanced disease setting) or alternative therapy (if platinum was not appropriate), and no prior checkpoint inhibitor therapy were eligible to participate. In phase I, pts received E (25, 50, 100, or 300 mg PO BID) + P (2 mg/kg or 200 mg IV Q3W); MTD was not exceeded. E (100 mg BID) + P (200 mg Q3W) dosing was selected for phase II. Response was assessed in RECIST 1.1–evaluable pts. Safety was assessed in pts receiving ≥1 E + P dose. Results: A total of 40 pts (phase I, n = 5; phase II, n = 35) were evaluated. Median age was 67 years, 75% were men, 88% were white, 100% had prior platinum therapy, and 75% had 0–1 prior line of therapy for advanced disease. Preliminary ORR (CR+PR) and DCR (CR+PR+SD) for all efficacy-evaluable pts were 35% (13/37; all PR) and 57% (21/37; 13 PR, 8 SD), respectively; for pts with 0–1 prior line of therapy for advanced disease, ORR and DCR were 37% (10/27) and 63% (17/27). At data cutoff, 12/13 responses were ongoing (range, 1+ to 652+ days). PFS and biomarker analyses are ongoing. The most common TRAEs (≥10% of 40 pts) were fatigue (28%), rash (18%), and increased amylase (10%; asymptomatic). Grade ≥3 TRAEs occurred in 20% of pts (rash was the only grade ≥3 TRAE to occur in > 1 pt [n = 3]). Three pts discontinued due to TRAEs (grade 3 rash [n = 1]; grade 3 COPD exacerbation [n = 1], grade 2 diarrhea [n = 1]). Conclusions: E + P was generally well tolerated and associated with increased response compared with previously reported PD-1 inhibitor monotherapy in pts with advanced UC. A phase III UC study is planned. Clinical trial information: NCT02178722.