Efficacy/safety of epacadostat plus pembrolizumab in triple-negative breast cancer and ovarian cancer: Phase I/II ECHO-202 study.

1103Background: Epacadostat is an oral, potent, and selective inhibitor of indoleamine 2,3-dioxygenase 1, a tryptophan-catabolizing enzyme that induces immune tolerance via T-cell suppression and is associated with poor patient (pt) survival when overexpressed in some cancers. The ongoing, open-label, phase 1/2 (P1/2) ECHO-202/KEYNOTE-037 study is evaluating the efficacy, safety, and tolerability of epacadostat plus PD-1 inhibitor pembrolizumab (E + P) in pts with advanced/recurrent cancers. We report P1/2 study outcomes for triple-negative breast cancer (TNBC) pts and P2 outcomes for ovarian cancer (OVC; no P1) pts as of a 29OCT2016 data cutoff. Methods: Eligible pts were ≥18 years old with no prior checkpoint inhibitor treatment (tx); prior platinum/taxane tx was required for OVC pts. As part of P1 dose escalation, TNBC pts received E (300 mg BID) + P (200 mg Q3W). In P2, TNBC and OVC pts received E (100 mg BID) + P (200 mg Q3W). Response (RECIST v1.1) was assessed in evaluable pts. Safety and tolerabil...