Immune checkpoint inhibitors (CPIs) including anti-programmed cell death 1 (PD-1), anti-PD ligand 1 (PD-L1) and anti-cytotoxic lymphocyte associated protein 4 (CTLA-4) antibodies have shown promising results in several solid cancers including small cell lung cancers. The gene discussed is CTLA4; the disease is small cell lung carcinoma.