RO9021 is a potent and selective inhibitor of the bromodomain and extra-terminal (BET) protein BRD4. It is primarily utilized in pharmaceutical research and development, particularly in oncology, for its potential therapeutic applications in treating various cancers, including hematological malignancies and solid tumors. By disrupting epigenetic regulation, RO9021 inhibits the expression of oncogenes and tumor growth. Researchers are exploring its efficacy in preclinical studies, assessing safety, pharmacokinetics, pharmacodynamics, and suitability for clinical trials. Additionally, it is used in biochemical assays to study interactions with bromodomain targets, contributing to the development of novel anticancer therapies. As a specialty chemical, RO9021 serves as a niche research tool in medicinal chemistry.