Both PC9 and HCC827 cell lines have an exon 19 deletion in the EGFR gene....we tested the efficacy of the CDK4/6 inhibitor abemaciclib in the cell clones, combining a fixed dose (500 nM) of this drug with increasing concentrations of osimertinib....a short-term combined treatment inhibited cell proliferation more strongly than osimertinib alone in both PC9 and HCC827 Cyclin D1-overexpressing cells.