Discovery of selective CDK9 degraders with anti-AML activity using PROTAC technology

Cyclin-dependent kinase 9 (CDK9) has emerged as a pivotal therapeutic target in oncology, characterized by aberrant overexpression in both hematologic cancers and solid neoplasms. Selective CDK9 inhibition effectively disrupts transcriptional programs in tumor cells and induces apoptosis. Herein, we describe the generation of several proteolysis targeting chimeras (PROTACs) using the CDK9 inhibitor DRB as the core ligand. Compound D6 emerged as the most active degrader in this series, eliciting CDK9 degradation with a D_max value of 45% in acute myeloid leukemia (AML) cells. The cellular activity of D6 was found to be 12 times higher than that of its parental inhibitor DRB, while showing no degradation activity toward other CDK family kinases. This enhanced antiproliferative activity was primarily mediated through increased induction of apoptosis. Furthermore, D6 suppressed tumor growth in vivo, achieving an inhibition rate of 31%, and demonstrated a favorable safety profile. Our findings indicate that D6 is a promising candidate worthy of further investigation, and that CDK9-targeted degradation is a valuable potential therapeutic option for AML.