ICIs have emerged as a landmark event for the treatment of lung cancer; among the FDA-approved ICIs, Pembrolizumab and Nivolumab (both anti-PD1), as well as Atezolizumab and Durvalumab (both anti-PD-L1), and Ipilimumab (anti-CTLA-4), alone or in combination with each other, were effective against small cell lung cancer (SCLC), NSCLC, and metastatic lung carcinomas, and improved the prognosis in these patients [153,154,155,156,157,158]. Here, CTLA4 is linked to small cell lung carcinoma.