CDK4/6 inhibition overcomes venetoclax resistance mechanisms with enhanced combination activity in acute myeloid leukemia

Venetoclax (ven) combined with azacytadine is a widely used therapy for acute myeloid leukemia (AML). However, most patients develop resistance. To identify more effective combinations, we analyze 302 AML patient samples and find ven plus palbociclib (ven+palbo), a cyclin dependent kinase (CDK)4/6 inhibitor, to be highly effective. Ven+palbo shows synergistic activity in AML cell lines and patient-derived xenograft mouse models. Patient samples exhibiting a synergistic response to ven+palbo show downregulation of genes involved in protein synthesis. Genome-wide (CRISPR) screening shows that loss of translational genes uniquely confers sensitivity to ven but not to ven+palbo. AML cells exposed to ven exhibit an adaptive increase of protein synthesis that is overcome by ven+palbo through regulation of translational machinery. Additionally, ven+palbo mitigates resistance mechanisms observed with single-agent ven (BAX loss) and palbo (RB1 loss). Finally, we identify the loss of IKZF1 as a mechanism of resistance to ven+palbo and show that targeting AXL is effective in IKZF1-mutated AML.