In a recent phase 2 trial assessing the intracranial activity of pembrolizumab monotherapy (PD-1 inhibitor) in patients with NSCLC presenting with asymptomatic, untreated, or progressing intracranial metastases measuring 5–20 mm in size, the intracranial ORR was 30% in patients with PD-L1 expression ≥1%.37 In comparison, no responses were seen in a second, smaller cohort of patients whose tumors were negative or not evaluable for PD-L1. The gene discussed is CD274; the disease is non-small cell lung carcinoma.