CDKI-73 is a potent and selective inhibitor of cyclin-dependent kinases (CDKs), particularly CDK9, which plays a key role in transcriptional regulation. It is primarily used in cancer research due to its ability to suppress the expression of short-lived oncoproteins such as Mcl-1, which are critical for tumor cell survival. By inhibiting CDK9, CDKI-73 disrupts RNA polymerase II activity, leading to reduced transcription of pro-survival genes and inducing apoptosis in cancer cells. It has shown promising activity in hematological malignancies, including leukemia and lymphoma, where dysregulation of transcription is a hallmark. CDKI-73 is valued in preclinical studies for its high selectivity and potency, making it a useful tool compound for probing CDK9-dependent pathways and evaluating therapeutic strategies targeting transcriptional addiction in cancer. Its application is mainly confined to in vitro and in vivo research settings, aiding the development of novel anticancer agents.