PURPOSE: Genomes of tumors that are deficient in DNA mismatch repair (dMMR) have high microsatellite instability (MSI-H) and harbor hundreds to thousands of somatic mutations that encode potential neoantigens. Such tumors are therefore likely to be immunogenic, triggering upregulation of immune checkpoint proteins. Pembrolizumab, an anti‒programmed death-1 monoclonal antibody, has antitumor activity against MSI-H/dMMR cancer. We report data from the phase II KEYNOTE-158 study of pembrolizumab in patients with previously treated, advanced noncolorectal MSI-H/dMMR cancer. PATIENTS AND METHODS: Eligible patients with histologically/cytologically confirmed MSI-H/dMMR advanced noncolorectal cancer who experienced failure with prior therapy received pembrolizumab 200 mg once every 3 weeks for 2 years or until disease progression, unacceptable toxicity, or patient withdrawal. Radiologic imaging was performed every 9 weeks for the first year of therapy and every 12 weeks thereafter. The primary end point was objective response rate per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, as assessed by independent central radiologic review. RESULTS: Among 233 enrolled patients, 27 tumor types were represented, with endometrial, gastric, cholangiocarcinoma, and pancreatic cancers being the most common. Median follow up was 13.4 months. Objective response rate was 34.3% (95% CI, 28.3% to 40.8%). Median progression-free survival was 4.1 months (95% CI, 2.4 to 4.9 months) and median overall survival was 23.5 months (95% CI, 13.5 months to not reached). Treatment-related adverse events occurred in 151 patients (64.8%). Thirty-four patients (14.6%) had grade 3 to 5 treatment-related adverse events. Grade 5 pneumonia occurred in one patient; there were no other treatment-related fatal adverse events. CONCLUSION: Our study demonstrates the clinical benefit of anti–programmed death-1 therapy with pembrolizumab among patients with previously treated unresectable or metastatic MSI-H/dMMR noncolorectal cancer. Toxicity was consistent with previous experience of pembrolizumab monotherapy.

PURPOSE: KEYNOTE-158 ( ClinicalTrials.gov identifier: NCT02628067) is a phase II basket study investigating the antitumor activity and safety of pembrolizumab in multiple cancer types. We present interim results from patients with previously treated advanced cervical cancer. PATIENTS AND METHODS: Patients received pembrolizumab 200 mg every 3 weeks for 2 years or until progression, intolerable toxicity, or physician or patient decision. Tumor imaging was performed every 9 weeks for the first 12 months and every 12 weeks thereafter. The primary end point was objective response rate (ORR), assessed per Response Evaluation Criteria in Solid Tumors (version 1.1) by independent central radiologic review. Safety was a secondary end point. RESULTS: Ninety-eight patients were treated. Median age was 46.0 years (range, 24 to 75 years), and 65.3% of patients had Eastern Cooperative Oncology Group performance status of 1. Eighty-two patients (83.7%) had programmed death-ligand 1 (PD-L1)–positive tumors (combined positive score ≥ 1), 77 having previously received one or more lines of chemotherapy for recurrent or metastatic disease. Median follow-up was 10.2 months (range, 0.6 to 22.7 months). ORR was 12.2% (95% CI, 6.5% to 20.4%), with three complete and nine partial responses. All 12 responses were in patients with PD-L1–positive tumors, for an ORR of 14.6% (95% CI, 7.8% to 24.2%); 14.3% (95% CI, 7.4% to 24.1%) of these responses were in those who had received one or more lines of chemotherapy for recurrent or metastatic disease. Median duration of response was not reached (range, ≥ 3.7 to ≥ 18.6 months). Treatment-related adverse events occurred in 65.3% of patients, and the most common were hypothyroidism (10.2%), decreased appetite (9.2%), and fatigue (9.2%). Treatment-related grade 3 to 4 adverse events occurred in 12.2% of patients. CONCLUSION: Pembrolizumab monotherapy demonstrated durable antitumor activity and manageable safety in patients with advanced cervical cancer. On the basis of these results, the US Food and Drug Administration granted accelerated approval of pembrolizumab for patients with advanced PD-L1–positive cervical cancer who experienced progression during or after chemotherapy.