In another preclinical study of SCLC, the combination of the CHK1 inhibitor SRA737 with anti-PD-L1 increased the M1 subtype macrophage population, decreased the expression of the immunosuppressive myeloid suppressor cell (MDSC) population, and greatly improved the immune microenvironment of tumor cells, further enhancing the therapeutic efficacy of ICB therapy (Sen et al., 2019b). This evidence concerns the gene CHEK1 and small cell lung carcinoma.