LLY-283 is a potent and selective inhibitor of protein arginine methyltransferase 5 (PRMT5), an enzyme involved in epigenetic regulation through methylation of arginine residues on histone and non-histone proteins. Its primary application lies in cancer research, where it demonstrates antitumor activity by disrupting PRMT5-mediated signaling pathways that are often dysregulated in various malignancies, including hematologic cancers and solid tumors. Due to its ability to induce cell cycle arrest and apoptosis in cancer cells, LLY-283 is widely used as a research tool to study the biological roles of PRMT5 and the therapeutic potential of its inhibition. It has shown efficacy in preclinical models, particularly in cancers with MTAP deletion, which increases dependency on PRMT5 activity. This makes LLY-283 valuable for validating PRMT5 as a drug target and for guiding the development of clinical candidates. Beyond oncology, LLY-283 is also applied in studies of cellular differentiation, RNA splicing, and immune modulation, helping to uncover the broader implications of arginine methylation in cellular function and disease. Its selectivity and pharmacological properties make it a key compound in epigenetic drug discovery and mechanistic biology.