Mesotheliomas express PD-L1 in a minority of patients.5, 6 Promising clinical activity of nivolumab, a fully humanised, IgG4, PD-1-immune checkpoint inhibitor antibody, has been reported in phase 2 trials of patients with malignant pleural mesothelioma.7, 8, 9 In the MERIT trial,7 nivolumab was associated with a median overall survival of 17·3 months (95% CI 11·5–not reached), median progression-free survival of 6·1 months (95% CI 2·9–9·9), and a response rate of 26% in patients with advanced or metastatic malignant pleural mesothelioma, leading to its approval in Japan. The gene discussed is CD274; the disease is mesothelioma.