In an alternate situation, the combination of CHK1 inhibition using another inhibitor SRA737 and a low dose of gemcitabine (chemotherapeutic drug) was observed to enhance the impact of PD-L1 IC blockade (via the use of an anti-PD-L1 antibody) in an immunocompetent Rb/TP53/p130 (RPP) tumor-bearing SCLC mouse model [20]. Here, TP53 is linked to small cell lung carcinoma.