CCT128930 is a selective inhibitor of cyclin-dependent kinase 7 (CDK7), which plays a critical role in transcription regulation and cell cycle progression. It is primarily used in research settings to study the function of CDK7 in cancer and transcriptional control. The compound has shown potential in suppressing the growth of cancer cells, particularly in models of transcriptionally addicted cancers such as small cell lung cancer and certain leukemias. By inhibiting CDK7, CCT128930 reduces the phosphorylation of RNA polymerase II, leading to downregulation of key oncogenes like MYC. This makes it a valuable tool for probing transcriptional dependencies in tumor cells and evaluating CDK7 as a therapeutic target. Due to its potency and selectivity, it is also used in preclinical studies to assess the effects of CDK7 inhibition on gene expression and cell viability.