PDCD1 and small cell lung carcinoma: Novel immunomodulatory agents beyond PD-1/PD-L1 inhibitors have also been intensively evaluated preclinically and clinically in SCLC, among which delta-like ligand 3 (DLL3)-targeted bispecific T-cell engagers (BiTEs) have garnered the most extensive research and demonstrated promising clinical efficacy [14–17].