BACKGROUND: An open-label, non-comparative study assessed the efficacy and safety of nivolumab in Japanese patients with first recurrence glioblastoma. METHODS: Patients with first recurrence of histologically confirmed World Health Organization Grade IV glioma, after treatment with temozolomide and radiotherapy, received nivolumab 3 mg/kg every 2 weeks until confirmed disease progression (Response Assessment in Neuro-Oncology criteria) or toxicity. Primary endpoint was 1-year overall survival rate assessed by Bayesian approach. The prespecified efficacy criterion was that the Bayesian posterior probability threshold for exceeding the 1-year overall survival of bevacizumab (34.5%) from the Japanese phase 2 study (JO22506) would be 93%. RESULTS: Of the 50 enrolled patients, 44 (88.0%) had recurrent malignant glioma (glioblastoma, gliosarcoma), and of these, 26 (59.1%) had at least one measurable lesion at baseline. The Bayesian posterior mean 1-year overall survival (90% Bayesian credible intervals) with nivolumab was 54.4% (42.27-66.21), and the Bayesian posterior probability of exceeding the threshold of the 1-year overall survival rate of bevacizumab (34.5%) was 99.7%. Median (90% confidence interval) overall and progression-free survival was 13.1 (10.4-17.7) and 1.5 (1.4-1.5) months, respectively. One partial response was observed (objective response rate 1/26 evaluable patients [3.8%]). Treatment-related adverse event rates were 14.0% for Grade 3-4 and 2.0% for Grade 5; most adverse events resolved and were manageable. CONCLUSIONS: The 1-year overall survival with nivolumab monotherapy in Japanese patients with glioblastoma met the prespecified efficacy criterion. The safety profile of nivolumab was consistent with that observed in other tumor types. CLINICAL TRIAL REGISTRATION: JapicCTI-152967.