Pembrolizumab in advanced endometrial cancer: Preliminary results from the phase Ib KEYNOTE-028 study.

5581Background: There are currently no treatment options for pts with endometrial cancer who progress on chemotherapy. Pembrolizumab is an anti–PD-1 antibody that blocks interaction between PD-1 and its ligands, PD-L1/PD-L2. The safety and efficacy of pembrolizumab were evaluated in advanced solid tumors in the KEYNOTE-028 study (NCT02054806). Preliminary results from the endometrial carcinoma cohort are presented. Methods: Key inclusion criteria were advanced endometrial carcinoma (excluded sarcomas, mesenchymal tumors), failure of prior systemic therapy, ECOG PS 0-1, and PD-L1 expression in ≥ 1% of tumor or stroma cells by IHC. Pembrolizumab 10 mg/kg every 2 wk was given for up to 24 mo or until confirmed progression, intolerable toxicity, death, or consent withdrawal. Response was assessed every 8 wk for the first 6 mo and every 12 wk thereafter. The primary end point was ORR per RECIST v1.1 by investigator assessment. Results: In the 24 pts enrolled, median age was 67.0 y; 66.7% had an ECOG PS of 1; 6...