GSK503 is primarily utilized in research settings as a potent and selective inhibitor of the EZH2 enzyme, which is part of the Polycomb Repressive Complex 2 (PRC2). This compound is extensively used in studies aimed at understanding the role of EZH2 in gene silencing and its involvement in various cancers, such as lymphoma, breast cancer, and prostate cancer. By inhibiting EZH2, GSK503 helps researchers explore its impact on tumor growth and progression, providing insights into potential therapeutic strategies. Additionally, it is employed in epigenetic research to investigate the mechanisms of histone methylation and its influence on cellular differentiation and development.