(S)-PFI-2 HCl is primarily used in biochemical research as a potent and selective inhibitor of the SETD7 (SET domain-containing protein 7) methyltransferase enzyme. This enzyme plays a significant role in the methylation of histone and non-histone proteins, which are critical processes in regulating gene expression and cellular functions. By inhibiting SETD7, (S)-PFI-2 HCl helps researchers study the impact of methylation on various biological pathways, including those involved in cancer, inflammation, and cardiovascular diseases. Its application is particularly valuable in understanding epigenetic mechanisms and developing potential therapeutic strategies targeting methylation-related disorders.