Pembrolizumab in patients (pts) with PD-L1–positive (PD-L1+) advanced ovarian cancer: Updated analysis of KEYNOTE-028.

5513 Background: Overexpression of the PD-1 ligand PD-L1 has been demonstrated in ovarian cancer and may hinder an effective antitumor immune response. A preliminary analysis of the ovarian cancer cohort of the KEYNOTE-028 study (NCT02054806) suggested that the PD-1 inhibitor pembrolizumab has promising antitumor activity in pts with PD-L1 + advanced ovarian cancer. An updated analysis of the ovarian cancer cohort based on 15.5 months of follow-up is presented. Methods: Key eligibility criteria for the ovarian cohort of this nonrandomized, multicohort phase Ib trial were advanced ovarian epithelial, fallopian tube, or primary peritoneal carcinoma; failure of prior therapy; PD-L1 positivity defined as membranous staining on ≥1% of tumor and associated inflammatory cells or positive staining in stroma; and ECOG PS 0/1. Pembrolizumab (10 mg/kg every 2 wk) was given for ≤2 y or until confirmed progression/unacceptable toxicity. Response was assessed per RECIST v1.1 by investigators every 8 wk for the first 6 mo and every 12 wk thereafter. Primary end points were safety, tolerability, and confirmed ORR. Results: 26 pts (median age, 57.5 y) were enrolled; 61.5% were white, 38.5% received ≥5 therapies for recurrent/metastatic disease, and 53.8% received prior neoadjuvant/adjuvant therapies. As of the October 10, 2016, data cutoff, the median follow-up duration was 15.5 mo (range, 2.4-30.8 mo). 1 pt had a complete response and 2 had partial responses; 6 pts had stable disease as best response. ORR was 11.5% (95% CI, 2.4%-30.2%). Tumor reduction was observed in 6/26 (23.1%); all 3 patients who responded completed 2 years of treatment. Median duration of response was not reached (range, 24.9+ to 26.5+ mo). Median (95% CI) PFS and OS were 1.9 mo (1.8-3.2 mo) and 13.1 mo (6.7-17.5 mo) respectively. Treatment-related AEs occurred in 73.1% of pts, and the most common were arthralgia (19.2%), nausea (15.4%), pruritus (15.4%), rash (11.5%), and diarrhea (11.5%). 1 patient had a grade 3 drug-related adverse event (transaminase increased). Conclusions: With 15.5 mo of follow-up, pembrolizumab continued to be well tolerated and demonstrated durable antitumor activity in pts with advanced ovarian cancer. Clinical trial information: NCT02054806.