This led to the FDA approval of nivolumab, a fully humanised PD-1 ICI antibody, as a third-line treatment for recurrent SCLC in 2018; and of atezolizumab, a fully humanised PD-L1 ICI antibody, as first-line treatment in combination with chemotherapy for extensive diseased staged SCLC (ED-SCLC) in 2019 [25,26]. The gene discussed is PDCD1; the disease is small cell lung carcinoma.