AZ5576

AZ5576 is a potent, highly selective, and orally bioavailable small molecule inhibitor of Cyclin-dependent kinase 9 (CDK9), developed by AstraZeneca. CDK9 is a serine/threonine kinase that regulates the elongation phase of transcription by phosphorylating RNA polymerase II at serine 2 (pSer2-RNAPII). By inhibiting CDK9, AZ5576 indirectly modulates the expression of short-lived proteins such as the anti-apoptotic factor Mcl1, which is frequently linked to tumor survival and chemotherapy resistance. In preclinical models, AZ5576 has demonstrated the ability to induce rapid, dose-dependent decreases in pSer2-RNAPII, leading to the loss of Mcl1 mRNA and protein, subsequent activation of caspase-3, and induction of apoptosis. The compound has shown efficacy in various hematological malignancy models, including acute myeloid leukemia (AML), multiple myeloma (MM), and diffuse large B-cell lymphoma (DLBCL), even in the presence of protective cytokines or bone marrow stromal cells.