Pembrolizumab for myelodysplastic syndromes after failure of hypomethylating agents in the phase 1b KEYNOTE-013 study

The phase 1b multicohort KEYNOTE-013 study assessed the safety and antitumor activity of pembrolizumab given at 10 mg/kg/day every 2 weeks for up to 2 years in hematologic malignancies, including myelodysplastic syndromes (MDS) refractory to a hypomethylating agent (HMA). Primary outcomes were safety and objective response rate per International Working Group 2006 criteria. By June 26, 2020, 28 patients were enrolled; median duration of follow-up was 5.6 months (range, 1-78), and 25 patients (89%) had died. Treatment-related adverse events occurred in 10 patients (36%), including 2 (7%) treatment-related discontinuations. No patient achieved complete or partial response. Five patients (19%) had bone marrow complete response, 12 (44%) stable disease, 10 (37%) progressive disease, 6 (22%) cytogenetic response, and 5 (19%) hematologic improvement. Median overall survival (OS) was 6.0 months (95% CI, 4-12); the overall 2-year OS rate was 17%. Pembrolizumab had manageable safety and clinical activity in patients with HMA-refractory MDS.