SY-5609 is a selective and potent oral inhibitor of CDK7 (cyclin-dependent kinase 7), a key regulator of transcription and cell cycle progression. It is primarily investigated for its anticancer properties, especially in the treatment of solid tumors. By inhibiting CDK7, SY-5609 disrupts the transcription of genes involved in tumor growth and survival, including those associated with oncogenic drivers in cancers such as ovarian, lung, and breast cancer. The compound shows strong activity against tumor cells that are dependent on super-enhancer-driven gene expression, making it a promising candidate for treating cancers with high transcriptional addiction. Preclinical studies have demonstrated that SY-5609 induces apoptosis and suppresses tumor proliferation with a favorable pharmacokinetic profile, supporting its advancement into clinical trials. Its oral bioavailability enhances its potential for use in extended treatment regimens, offering a practical option for outpatient cancer therapy. Currently, it is under evaluation in early-phase clinical trials to determine efficacy, optimal dosing, and safety in humans.