Identification of Leishmania donovani inhibitors from pathogen box compounds of Medicine for Malaria Venture

Abstract

Leishmaniasis is a collective term used to describe various pathological conditions caused by an obligate intracellular protozoan of the genus Leishmania. It is one of the neglected diseases and has been given low attention in drug discovery researches to narrow the existing gap in safety and efficacy of the currently used drugs to treat leishmaniasis. The challenge is further exacerbated by the emergence of drug resistance by the parasites. Aiming to look for potential anti-leishmanial hits and leads, we screened MMV Pathogen Box against clinically isolated L. donovani strain. Compounds were screened against promastigote, and then against amastigote stages; of which, 35 compounds showed >50% inhibition on promastigotes in the initial screen (1 μM). Out of these compounds, 9 compounds showed >70% inhibition with median inhibitory concentration (IC 50 ) ranges from 12 nM to 491 nM on anti-promastigote assay and 53 to 704 nM on intracellular amastigote assay. Identified compounds demonstrated good safety on THP-1 cell lines and sheep RBCs, and appropriate physico-chemical property suitable for further drug development. Two compounds (MMV690102 and MMV688262) were identified as lead compounds. Among these compounds, anti-tubercular agent MMV688262 (delamanid) showed synergistic effect with amphotericin B, indicating the prospect of this compound for combination therapy. The current study indicates the presence of additional hits which may hold promise as starting points for anti-leishmanial drug discovery and in-depth structure activity relationship studies. Future works also needs to investigate antiamastigotes activity of remaining 'hits', which were not covered in the present study. | P a g e Authors summaryVisceral leishmaniasis is a major public health problem in endemic regions. Different drugs have been used to treat visceral leishmaniasis. However, the available drugs are either toxic, noncompliance to the patient, painful upon administration, low in efficacy, or costly. New chemical entities that overcome the limitations of existing drugs are therefore desperately needed.Screening of 400 pathogen box compounds against of Leishmania donovani clinical isolate resulted in identification of 35 compounds with >50% inhibition against promastigotes at 1 μM.Out of these compounds, 9 showed >70% inhibition with median inhibitory concentration ranges from 12 nM to 491 nM on anti-promastigote assay, and 53 to 704 nM on intracellular amastigote assay. Our work identified new compounds which hold promise for further drug development.

Antileishmanial Chemotherapy through Clemastine Fumarate Mediated Inhibition of the Leishmania Inositol Phosphorylceramide Synthase

“…As such, it is perhaps not surprising that clemastine fumarate has been identified in other repurposing studies for NTDs, 62 − 68 including those looking for new antileishmanial applications. 69 However, significant antiparasitic activity has not been reported nor has a putative mode-of-action been identified. The discovery of antileishmanial efficacy as a selective inhibitor of the parasite enzyme (IPCS) that catalyzes the formation of the primary complex sphingolipid in Leishmania spp.…”

“…As a licensed medicine, clemastine fumarate has proven pharmacokinetic exposure and the high volume of distribution (9.5 ± 3.8 L kg –1 ) could be contributing to the enhanced perfusion of parasite infected cells. As such, it is perhaps not surprising that clemastine fumarate has been identified in other repurposing studies for NTDs, − including those looking for new antileishmanial applications . However, significant antiparasitic activity has not been reported nor has a putative mode-of-action been identified.…”