The results of a recent phase II clinical trial reveal that nivolumab, an IgG4 PD-1 immune checkpoint inhibitor is a safe and effective treatment for patients with non-small cell lung cancer (NSCLC). In a single-arm trial, patients, who were refractory to at least two other treatments, received nivolumab. Amongst patients who responded to nivolumab, the majority of responses were still ongoing at the time of publication, serious adverse events ocurred in 17% of patients. These findings support the assesment of nivolumab in phase III clinical trials in patients with advanced, treatment refractory NSCLC.