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

Current chemotherapeutics for leishmaniasis have multiple deficiencies, and there is a need for new safe, efficacious, and affordable medicines. This study describes a successful drug repurposing approach that identifies the over-the-counter antihistamine, clemastine fumarate, as a potential antileishmanial drug candidate. The screening for inhibitors of the sphingolipid synthase (inositol phosphorylceramide synthase, IPCS) afforded, following secondary screening against (Lmj) promastigotes, 16 active compounds. Further refinement through the dose response against IPCS and intramacrophage amastigotes identified clemastine fumarate with good activity and selectivity with respect to the host macrophage. On target engagement was supported by diminished sensitivity in a sphingolipid-deficient mutant (ΔLCB2) and altered phospholipid and sphingolipid profiles upon treatment with clemastine fumarate. The drug also induced an enhanced host cell response to infection indicative of polypharmacology. The activity was sustained across a panel of Old and New World species, displaying an activity equivalent to the currently used drug, glucantime, in a mouse model of infection. Overall, these data validate IPCS as an antileishmanial drug target and indicate that clemastine fumarate is a candidate for repurposing for the treatment of leishmaniasis.