Combined pembrolizumab and pegylated liposomal doxorubicin in platinum resistant ovarian cancer: A phase 2 clinical trial.

OBJECTIVE: Pegylated liposomal doxorubicin (PLD) in vitro may have immunomodulatory abilities and preclinical evidence suggests it synergizes with immune checkpoint blockade. We hypothesized that combining PLD and pembrolizumab would be active in patients with platinum-resistant ovarian cancer (PROC). METHODS: This was a single-arm, multi-center phase II trial. Eligible patients had PROC with ≤2 prior lines of cytotoxic therapy for recurrent or persistent disease. Twenty-six patients were enrolled and given pembrolizumab 200 mg intravenously (IV) every 3 weeks and PLD 40 mg/m2 IV every 4 weeks. Patients were assessed radiographically every 8 weeks. The primary endpoint was clinical benefit rate (CBR), defined as complete response (CR) + partial response (PR) + stable disease (SD) ≥24 weeks. The study was powered to detect an improvement in CBR from 25% to 50%, with rejection of the null hypothesis if at least 10 patients achieved clinical benefit. T-cell inflamed gene expression profiles (GEP) and PD-L1 were assessed and correlated with clinical outcome. RESULTS: Twenty-three patients were evaluable for best overall response. The study satisfied its primary endpoint, with 12 patients achieving clinical benefit for a CBR of 52.2% (95% CI 30.6-73.2%). There were 5 PRs (21.7%) and 1 CR (4.3%), for an overall response rate (ORR) of 26.1%. Six patients had SD lasting at least 24 weeks. Combination therapy was well tolerated without unexpected toxicities. CONCLUSIONS: The combination of pembrolizumab and PLD was manageable, without unexpected toxicities, and showed preliminary evidence of clinical benefit in the treatment of platinum resistant ovarian cancer. ORR and median PFS of combination therapy in this study was higher than historical comparisons of PLD alone or anti-PD-1/PD-L1 agents alone. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT02865811.