Cyclin-dependent kinase 9 (CDK9) plays a critical role in regulating transcriptional elongation and is essential for the expression of short-lived oncogenic and antiapoptotic mRNAs. Targeting CDK9 has emerged as a promising therapeutic strategy, particularly in hematological malignancies and MYC-driven cancers. However, its clinical application remains limited by several challenges, which may be overcome through the development of more selective and potent inhibitors.