In vitro and in vivo synergistic efficacy of ceritinib combined with PD-L1 inhibitor in ALK-rearranged NSCLC.

Both ceritinib (CER) and PD-1/PD-L1 have brought significant breakthrough for ALK-rearranged non-small-cell lung cancer (NSCLC). However, the overall clinical efficacy of either CER or PD-1/PD-L1 inhibitor monotherapy has been limited to a large extent. Besides, the antitumor effect of combined CER with PD-L1 inhibitor in ALK-rearranged NSCLC are not fully understood. In H2228 cells, we examined the tumor killing effect of CER plus PD-L1 inhibitor in vitro by quantitative RT-PCR, flow cytometry, ELISA, western blotting, peripheral blood mononuclear cells (PBMC) co-culture system, plasmid and transfection experiments. Then, a Ba/F3 (EML4-ALK-WT) xenograft mice model was utilized to further evaluate the synergistic anticancer effects of CER and PD-L1 inhibitor in vivo. Co-culture system of PBMC with H2228 cell promotes the expression of PD-L1 and phospho-ERK, and combination treatments facilitate lymphocyte proliferation and activation, inhibit PD-L1 expression, and enhance lymphocyte cytotoxicity and cell death. In the in vivo NSCLC xenograft model, the tumor volumes of combination were significant smaller than that either CER or PD-L1 treatment. Besides, the relative tumor growth inhibitions were 84.9%, 20.0% and 91.9% for CER, PD-L1 inhibitor and CER plus PD-L1 group, respectively. CER could synergize with PD-1/PD-L1 blockade to yield enhanced anti-tumor responses along with favorable tolerability of adverse effects. CER and PD-L1 inhibitor combined produced a synergistic antineoplastic efficacy in vitro and in vivo, which provide a key insight and proof of principle for evaluating CER plus PD-L1 blockade as combination therapy in clinical therapeutic practice.