Abstract #15 Drug Repurposing for Human Visceral Leishmaniasis: Screening Marketed Antifungal Azoles for Inhibition of Leishmanial CYP5122A1 and CYP51 Enzymes Yiru Jin1, Mei Feng1, Michael Zhuo Wang1 1Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS, USA CYP5122A1 is a novel cytochrome P450 (CYP) enzyme that is essential for the survival of Leishmania donovani, a major causative agent for human visceral leishmaniasis. Recent studies suggest that CYP5122A1 plays an important role as sterol 4-demethylase in ergosterol biosynthesis by Leishmania. Thus, CYP5122A1 inhibitors may represent a new therapeutic approach against the devastating infectious disease. To evaluate the effects of antifungal azoles on CYP5122A1, a panel of twenty marketed antifungal azoles (bifonazole, butoconazole, clotrimazole, econazole, efinaconazole, fenticonazole, fluconazole, isavuconazole, isoconazole, itraconazole, ketoconazole, miconazole, oxiconazole, posaconazole, ravuconazole, sertaconazole, sulconazole, terconazole, tioconazole, voriconazole) were screened for inhibition of CYP5122A1, as well as the lanosterol 14α-demethylase CYP51, using a fluorescence-based inhibition assay. All twenty azoles were potent inhibitors of leishmanial CYP51 with IC50 ranging from 0.031 to 0.084 M, whereas their inhibitory potencies against CYP5122A1 were much lower (0.25 to 12 M). Ravuconazole was identified as a selective CYP51 inhibitor with an IC50 value of 0.048 M and selectivity index of 250 against CYP5122A1. Interestingly, the imidazole class of antifungal azoles showed stronger inhibition against CYP5122A1 compared with the triazole class. These results can provide insights toward rational drug design of CYP5122A1 inhibitors. Future studies will attempt to obtain X-ray crystal structures of several select protein-ligand complexes and confirm the proposed biochemical roles of CYP5122A1 and CYP51 by treating parasites with selective inhibitors, followed by HPLC-MS/MS-based sterol analysis. Grant support: NIH P20GM113117, COBRE-CBID Pilot Project (MZW) NIH R01 AI139198 (MZW) .