In a work dedicated on the synthesis of Longamide B analogs, Fujimoto et al. prepared and evaluated C4-substituted pyrazinoindolone 90 as a potential inhibitor of indoleamine 2,3-dioxygenase 1 (IDO1, an enzyme overexpressed in certain cancers such as colon and stomach cancers (Scheme 22) [53]. Here, IDO1 is linked to cancer.