PFI-4 is primarily used in biomedical research as a selective inhibitor of the protein-protein interaction between the bromodomain of the BET family proteins and acetylated histones. It is particularly valuable in studying epigenetic regulation of gene expression. Researchers use PFI-4 to probe the role of BET bromodomains in cellular processes such as transcription, cell cycle progression, and inflammation. Due to its ability to cross cell membranes effectively, it is employed in cell-based assays to assess the effects of bromodomain inhibition on cancer cell proliferation, making it a tool compound in oncology drug discovery. PFI-4 also helps in understanding the therapeutic potential of targeting epigenetic readers in diseases like leukemia and other malignancies.