IDO1 and Alzheimer disease: By employing structure–activity relationship (SAR) studies, computational docking simulations and BBB score calculations, they designed multiple brain-penetrant compounds that interacted favorably with a proximal Ser167 residue in IDO (See Figure 4), as well as one representative analog within this series and demonstrated strong IDO1 inhibitory activity (IC50 = 0.16 μM, EC50 = 0.3 μM)—this compound has yet to progress to additional biological testing in AD models.