LLY-507 is a selective inhibitor of the protein arginine methyltransferase 5 (PRMT5), an enzyme involved in epigenetic regulation through methylation of arginine residues on histone and non-histone proteins. Due to its role in modulating key cellular processes such as transcription, splicing, and DNA repair, PRMT5 inhibition has emerged as a promising strategy in oncology. LLY-507 is primarily used in preclinical research to study the biological effects of PRMT5 inhibition. It has shown potent anti-proliferative activity in various cancer cell lines, particularly in those with high PRMT5 dependency such as certain hematological malignancies and solid tumors. By disrupting symmetric dimethylation of arginine, LLY-507 induces cell cycle arrest and apoptosis, making it a valuable tool compound for validating PRMT5 as a therapeutic target. Its application extends to combination studies with other anticancer agents, where it has demonstrated synergistic effects, especially with drugs targeting related epigenetic pathways or DNA damage response mechanisms. LLY-507 helps elucidate the therapeutic potential and mechanisms of resistance associated with PRMT5 inhibition, supporting the development of clinical candidates in cancer therapy.