Identification of Three Classes of Heteroaromatic Compounds with Activity against Intracellular Trypanosoma cruzi by Chemical Library Screening

Esther Bettiol,Marie Samanovic,Ana Rodriguez,Frederick Buckner,Andrew S Murkin,Jayne Raper,James H Mckerrow

doi:10.1371/journal.pntd.0000384

Abstract

The development of new drugs against Chagas disease is a priority since the currently available medicines have toxic effects, partial efficacy and are targeted against the acute phase of disease. At present, there is no drug to treat the chronic stage. In this study, we have optimized a whole cell-based assay for high throughput screening of compounds that inhibit infection of mammalian cells by Trypanosoma cruzi trypomastigotes. A 2000-compound chemical library was screened using a recombinant T. cruzi (Tulahuen strain) expressing β-galactosidase. Three hits were selected for their high activity against T. cruzi and low toxicity to host cells in vitro: PCH1, NT1 and CX1 (IC50: 54, 190 and 23 nM, respectively). Each of these three compounds presents a different mechanism of action on intracellular proliferation of T. cruzi amastigotes. CX1 shows strong trypanocidal activity, an essential characteristic for the development of drugs against the chronic stage of Chagas disease where parasites are found intracellular in a quiescent stage. NT1 has a trypanostatic effect, while PCH1 affects parasite division. The three compounds also show high activity against intracellular T. cruzi from the Y strain and against the related kinetoplastid species Leishmania major and L. amazonensis. Characterization of the anti–T. cruzi activity of molecules chemically related to the three library hits allowed the selection of two compounds with IC50 values of 2 nM (PCH6 and CX2). These values are approximately 100 times lower than those of the medicines used in patients against T. cruzi. These results provide new candidate molecules for the development of treatments against Chagas disease and leishmaniasis.

Highlights

Chagas disease or American trypanosomiasis is a devastating disease caused by the trypanosomatid protozoan Trypanosoma cruzi
Chagas disease is caused by infection with the protozoan parasite Trypanosoma cruzi and affects 16 million people in South and Central America
Two drugs with high toxicity exist to treat the acute phase of the disease and no drug is available for treatment of the chronic stage

Summary

Introduction

Chagas disease or American trypanosomiasis is a devastating disease caused by the trypanosomatid protozoan Trypanosoma cruzi It is endemic in 18 countries of Central and South America, putting 120 million of people at risk, with an estimated 16–18 million people currently infected [1]. The disease first manifests itself with an acute phase involving symptoms of swelling near the infection site, fever, fatigue, and enlarged lymphatic organs It can remain asymptomatic or manifest itself in a chronic form leading to cardiac insufficiency and megacolon. The two available drugs used to fight T. cruzi parasites during the acute stage are benznidazole (BZN) (Rochagan, Hoffmann-LaRoche) and nifurtimox (Lampit, Bayer). These drugs have toxic side effects and are not always effective. Though some studies suggest that treatment with either BZN or nifurtimox decreases parasite load and slows disease progression, treatment of the chronic stage with these compounds is not officially recommended [2]

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