Efficacy and safety of epacadostat plus pembrolizumab treatment of NSCLC: Preliminary phase I/II results of ECHO-202/KEYNOTE-037.

Abstract

9014 Background: ECHO-202/KEYNOTE-037 is an open-label, phase 1/2 study of epacadostat (a potent and selective oral inhibitor of the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1) plus pembrolizumab (E + P) in patients (pts) with advanced tumors. We report preliminary efficacy and safety outcomes for the phase 1/2 NSCLC cohort. Methods: Adult pts with prior platinum-based therapy (tx) and no prior checkpoint inhibitor tx were eligible. Phase 1 dose-escalation tx was E (25, 50, 100, 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) tx doses were selected for phase 2 cohort expansion. Efficacy was evaluated by tumor proportion score (TPS [% viable tumor cells, PD-L1 staining]: < 50% and ≥50%) and by prior lines of tx in RECIST 1.1 evaluable pts. Safety was assessed in pts receiving ≥1 E + P dose. Results: As of 29OCT2016,43 pts (phase 1, n = 12; phase 2, n = 31) were evaluated. Median age was 65 years, 58% of pts were women, 12% were EGFR-positive, and 23% were KRAS-positive. Most pts had a history of smoking (84%), ≤2 prior lines of tx (84%), and no prior TKI tx (93%). For the 40 efficacy-evaluable pts, ORR (CR+PR) and DCR (CR+PR+SD) were 35% (14/40; 14 PR) and 60% (24/40; 10 SD), respectively. PD-L1 TPS test results were available in 28/40 efficacy-evaluable pts. ORR and DCR for pts with TPS ≥50% and ≤2 prior tx were 43% (3/7; all PR) and 57% (4/7; 1 SD), respectively; for pts with TPS < 50% and ≤2 prior tx, ORR and DCR were 35% (6/17; all PR) and 53% (9/17; 3 SD). Among the 40 efficacy-evaluable pts, 12/14 responses were ongoing (range, 1+ to 519 days) at data cutoff. PFS and biomarker analyses are ongoing. Across all 43 pts, most frequent TRAEs were fatigue (19%), arthralgia (9%), and increased AST (9%); 16% of pts had grade ≥3 TRAEs, and increased lipase (asymptomatic) was the only grade ≥3 TRAE that occurred in > 1 pt (n = 2). Two pts discontinued due to TRAEs (grade 3 increased AST, grade 2 increased ALT [n = 1]; grade 2 brain edema [n = 1]). Conclusions: E + P was generally well tolerated and associated with promising responses in pts with NSCLC. A phase 3 NSCLC study is planned. Clinical trial information: NCT02178722.