Used in pharmaceutical research as a potent and selective inhibitor of indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme involved in immune regulation. It modulates the immune response by blocking the metabolism of tryptophan along the kynurenine pathway, thereby preventing immunosuppression in the tumor microenvironment. This makes it a candidate for investigation in cancer immunotherapy, particularly in combination with other immune checkpoint inhibitors. Its (S)-stereochemistry is critical for optimal binding and inhibitory activity. Also employed as a reference compound in biochemical assays to study IDO1 enzyme kinetics and inhibition mechanisms.