Phase IB study of pembrolizumab (Pembro) and pegylated-interferon alfa-2b (Peg-IFN) in advanced melanoma (MEL).

9539Background: Overall responses (OR) are reported in 34% of patients (pts) with advanced MEL treated with Pembro. Landmark survival is 66%/49% at 1-/2- years respectively. Pre-existing CD8+ T-cell infiltrates and IFN gene signature at tumor sites correlate with response to PD-1 blockade. To evaluate synergy between PD-1 blockade and Peg-IFN, we implemented a phase Ib study of Pembro/Peg-IFN combination with dose-seeking and dose-expansion phases in stage IV MEL. Methods: Pts with IV MEL were enrolled. Peg-IFN was dose-escalated using modified toxicity probability interval (mTPI) design in 3 cohorts (4 pts each) at 1,2 and 3 mcg/kg SC while Pembrolizumab was dosed at 2mg/kg q3weeks in all pts. Primary endpoints were safety and incidence of dose-limiting toxicities (DLTs). Secondary endpoints were OR rate (ORR), progression free and overall survival. Response was assessed every 12 weeks (RECIST 1.1). Sequential blood draws and tumor biopsies were collected. Here, we report on response observed in 24 pts t...