Ex Vivo Phenotypic Screening of Two Small Repurposing Drug Collections Identifies Nifuratel as a Potential New Treatment against Visceral and Cutaneous Leishmaniasis

Abstract

Leishmaniases are vector-borne neglected diseases caused by single-celled parasites. The search for new antileishmanial drugs has experienced a strong boost thanks to the application of bioimaging to phenotypic screenings based on intracellular amastigotes. Mouse splenic explants infected with fluorescent strains of <i>Leishmania</i> are proven tools of drug discovery, where hits can be easily transferred to preclinical in vivo models. We have developed a two-staged platform for antileishmanial drugs. First, we screened two commercial collections of repurposing drugs with a total of 1769 compounds in ex vivo mouse splenocytes infected with an infrared emitting <i>Leishmania infantum</i> strain. The most active and safest compounds were scaled-up to in vivo models of chronic <i>Leishmania donovani</i> visceral leishmaniasis and <i>Leishmania major</i> cutaneous leishmaniasis. From the total of 1769 compounds, 12 hits with selective indices >35 were identified, and 4 of them were tested in vivo in a model of <i>L. donovani</i> visceral leishmaniasis. Nifuratel, a repurposed synthetic nitrofuran, when administered orally at 50 mg/kg bw once or twice a day for 10 days, caused >80% reduction in the parasitic load. Furthermore, the intralesional administration of nifuratel in a model of cutaneous leishmaniasis by <i>L. major</i> produced the parasitological cure. From the previous results we have deduced the great capacity of mouse splenic explants to identify new hits, a model which could be easily transferred to in vivo models, as well as the potential use of nifuratel as an alternative to the current treatment of cutaneous leishmaniasis.