PDCD1 and small cell lung carcinoma: Whereas dual blockade of TIGIT and PD-1/PD-L1 shows promising results in some experimental tumor models (63–65) and in multiple trials (35–39), combination of the anti-TIGIT antibody tiragolumab and the PD-L1 inhibitor atezolizumab failed to improve progression-free survival in a phase III extensive-stage small cell lung cancer trial (ClinicalTrials.gov NCT04256421).