Study Protocol: Phase-Ib Trial of Nivolumab Combined With Metformin for Refractory/Recurrent Solid Tumors

Although immune checkpoint inhibitors have shown significant survival benefits in the treatment of several cancers, optimal outcomes have been limited to certain subsets of patients. In a previous study, we found that the addition of metformin to nivolumab, an anti-programmed cell death protein 1 (PD-1) antibody, yielded substantial tumor regression in mouse models. Further analysis revealed that the number of tumor-infiltrating CD8 T cells had increased markedly. Based on this result, we have launched an investigator-initiated open-label phase-Ib clinical trial. The objectives of this trial are to investigate the safety, efficacy, and pharmacokinetics of a metformin-nivolumab combination treatment. This study consists of 2 parts. The recommended dose of metformin combined with nivolumab is determined in part 1. The safety and efficacy of the optimal dose of metformin to be delivered in conjunction with nivolumab are examined in part 2. Patient eligibility is based on the following criteria: pathologic diagnosis of refractory/recurrent solid tumor (part 1), and non-small-cell lung cancer or pancreatic cancer refractory to standard primary treatment (part 2); no prior use of immune checkpoint inhibitor; performance status 0 or 1; age ≥ 20 years; and adequate organ function. The primary endpoints are safety in part 1 and safety and pharmacokinetics in part 2. The maximum tolerated dose and recommended dose are determined in part 1 by the 3 + 3 cohort method, and the dose-limiting toxicity evaluation period for each patient is 4 weeks from the start of administration. In part 2, metformin is administered at the optimal dose determined in part 1. Total enrollment is 9 to 18 patients for part 1 and 30 patients for part 2. Enrollment began in 2017, and will be completed by 2019. The University Hospital Medical Information Network registration number for this study is 000028405.