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Previous analyses of the phase 2 KEYNOTE-087 (NCT02453594) trial of pembrolizumab monotherapy demonstrated effective antitumor activity with acceptable safety in patients with relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL). However, long-term response durability and outcome of patients who receive a second course after treatment discontinuation after complete response (CR) remain of clinical interest. We present KEYNOTE-087 data after >5 years of median follow-up. Patients with R/R cHL and progressive disease (PD) after autologous stem cell transplantation (ASCT) and brentuximab vedotin (BV; cohort 1), salvage chemotherapy and BV without ASCT (cohort 2), or ASCT without subsequent BV (cohort 3), received pembrolizumab for <= 2 years. Patients in CR who discontinued treatment and subsequently experienced PD were eligible for second-course pembrolizumab. Primary end points were the objective response rate (ORR) using blinded central review and safety. The median follow-up was 63.7 months. ORR was 71.4% (95% confidence interval [CI], 64.8-77.4; CR, 27.6%; partial response, 43.8%). Median duration of response (DOR) was 16.6 months; median progression-free survival was 13.7 months. A quarter of responders, including half of complete responders, maintained a response for >= 4 years. Median overall survival was not achieved. Among 20 patients receiving second-course pembrolizumab, ORR for 19 evaluable patients was 73.7% (95% CI, 48.8-90.8); median DOR was 15.2 months. Any-grade treatment-related adverse events occurred in 72.9% of patients and grade 3 or 4 adverse events occurred in 12.9% of patients; no treatment-related deaths occurred. Single-agent pembrolizumab can induce durable responses, particularly in patients achieving CR. Second-course pembrolizumab frequently reinduced sustained responses after relapse from initial CR.