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.

Immune checkpoint inhibitor (ICI) monoclonal antibodies (mAbs) targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed cell death protein 1 (PD-1) or its ligand (PD-L1) produce unique toxicity profiles. The objective of this review was to identify patterns and incidence of immune-related adverse events (irAE) based on tumour type and ICI class. Medline, EMBASE and COCHRANE databases were searched to identify prospective monotherapy trials of ICIs from 2003 to November 2015. Paired reviewers selected studies for inclusion and extracted data. Odds ratio (OR), χ² tests and multivariable regression models were used to analyse for effect size and associations. We identified 48 trials (6938 patients), including 26 CTLA-4, 17 PD-1, 2 PD-L1 trials, and 3 studies tested both CTLA-4 and PD-1. Grade 3/4 irAE were more common with CTLA-4 mAbs compared with PD-1 (31% versus 10%). All grades colitis (OR 8.7, 95% CI 5.8–12.9), hypophysitis (OR 6.5, 95% CI 3.0–14.3) and rash (OR 2.0, 95% CI 1.8–2.3) were more frequent with CTLA-4 mAbs; whereas pneumonitis (OR 6.4, 95% CI 3.2–12.7), hypothyroidism (OR 4.3, 95% CI 2.9–6.3), arthralgia (OR 3.5, 95% CI 2.6–4.8) and vitiligo (OR 3.5, 95% CI 2.3–5.3) were more common with PD-1 mAbs. Comparison of irAE from the three most studied tumour types in PD-1 mAbs trials [melanoma (n = 2048), non-small-cell lung cancer (n = 1030) and renal cell carcinoma (n = 573)] showed melanoma patients had a higher frequency of gastrointestinal and skin irAE and lower frequency of pneumonitis. CTLA-4 and PD-1 mAbs have distinct irAE profiles. Different immune microenvironments may drive histology-specific irAE patterns. Other tumour-dependent irAE profiles may be identified as data emerge from ICI trials.

PURPOSE: Pembrolizumab demonstrated durable antitumor activity in patients with previously treated, advanced microsatellite instability–high or mismatch repair–deficient (MSI-H/dMMR) tumors, including endometrial cancer, in the nonrandomized, open-label, multicohort, phase II KEYNOTE-158 study ( NCT02628067 ). We report efficacy and safety outcomes for patients with MSI-H/dMMR endometrial cancer enrolled in KEYNOTE-158. METHODS: Eligible patients from cohorts D (endometrial cancer, regardless of MSI-H/dMMR status) and K (any MSI-H/dMMR solid tumor, except colorectal) with previously treated, advanced MSI-H/dMMR endometrial cancer received pembrolizumab 200 mg once every 3 weeks for 35 cycles. The primary end point was objective response rate per RECIST version 1.1 by independent central radiologic review. Secondary end points included duration of response, progression-free survival, overall survival, and safety. RESULTS: As of October 5, 2020, 18 of 90 treated patients (20%) had completed 35 cycles of pembrolizumab and 52 (58%) had discontinued treatment. In the efficacy population (patients who received ≥ 1 dose of pembrolizumab and had ≥ 26 weeks of follow-up; N = 79), the median time from first dose to data cutoff was 42.6 (range, 6.4-56.1) months. The objective response rate was 48% (95% CI, 37 to 60), and median duration of response was not reached (2.9-49.7+ months). Median progression-free survival was 13.1 (95% CI, 4.3 to 34.4) months, and median overall survival was not reached (95% CI, 27.2 months to not reached). Among all treated patients, 76% had ≥ 1 treatment-related adverse event (grades 3-4, 12%). There were no fatal treatment-related events. Immune-mediated adverse events or infusion reactions occurred in 28% of patients (grades 3-4, 7%; no fatal events). CONCLUSION: Pembrolizumab demonstrated robust and durable antitumor activity and encouraging survival outcomes with manageable toxicity in patients with previously treated, advanced MSI-H/dMMR endometrial cancer.

Purpose: To establish the safety profile and antitumor activity of the anti–programmed death 1 receptor monoclonal antibody, pembrolizumab, in patients with recurrent or metastatic nasopharyngeal carcinoma (RM-NPC) that expressed programmed death-ligand 1 (PD-L1). Patients and Methods: KEYNOTE-028 (NCT02054806) is a nonrandomized, multicohort, phase Ib trial of pembrolizumab in patients with PD-L1–positive advanced solid tumors. Key eligibility criteria for the NPC cohort included unresectable or metastatic disease, failure on prior standard therapy, and PD-L1 expression in 1% or more of tumor cells or tumor-infiltrating lymphocytes. Patients received pembrolizumab 10 mg/kg every 2 weeks up to 2 years or until disease progression or unacceptable toxicity. Primary end point was objective response rate (ORR) per investigator review. Tumor response was assessed according to Response Evaluation Criteria in Solid Tumors (RECIST; version 1.1) every 8 weeks for the first 6 months and every 12 weeks thereafter. Results: Twenty-seven patients received pembrolizumab. Median age was 52.0 years (range, 18 to 68 years); 92.6% received prior therapies for RM-NPC; 70.4% had received three or more therapies. Partial response and stable disease were observed in seven and 14 patients, respectively, for an ORR of 25.9% (95% CI, 11.1 to 46.3) over a median follow-up of 20 months. ORR by central review was similar (26.3%). Drug-related adverse events that occurred in 15% or more of patients included rash (25.9%), pruritus (25.9%), pain (22.2%), hypothyroidism (18.5%), and fatigue (18.5%). Grade ≥ 3 drug-related adverse events occurred in eight patients (29.6%), and there was one drug-related death (sepsis). As of the data cutoff (June 20, 2016), two patients remained on pembrolizumab treatment. Conclusion: Pembrolizumab demonstrated antitumor activity and a manageable safety profile in patients with RM-NPC.