Identifican 600 compuestos contra la leishmaniasis, la enfermedad de Chagas y el mal del sueño

New Compound Sets Identified from High Throughput Phenotypic Screening Against Three Kinetoplastid Parasites: An Open Resource

Abstract

Using whole-cell phenotypic assays, the GlaxoSmithKline high-throughput screening (HTS) diversity set of 1.8 million compounds was screened against the three kinetoplastids most relevant to human disease, i.e. Leishmania donovani, Trypanosoma cruzi and Trypanosoma brucei. Secondary confirmatory and orthogonal intracellular anti-parasiticidal assays were conducted, and the potential for non-specific cytotoxicity determined. Hit compounds were chemically clustered and triaged for desirable physicochemical properties. The hypothetical biological target space covered by these diversity sets was investigated through bioinformatics methodologies. Consequently, three anti-kinetoplastid chemical boxes of ~200 compounds each were assembled. Functional analyses of these compounds suggest a wide array of potential modes of action against kinetoplastid kinases, proteases and cytochromes as well as potential host–pathogen targets. This is the first published parallel high throughput screening of a pharma compound collection against kinetoplastids. The compound sets are provided as an open resource for future lead discovery programs, and to address important research questions.

Introduction

Half a billion people are at risk of contracting diseases caused by kinetoplastid parasites of the genera Leishmania and Trypanosoma1. This group of flagellated protozoans causes African trypanosomiasis (T. brucei), Chagas disease (T. cruzi) and various clinical manifestations of leishmaniasis (Leishmania spp.). In particular, L. donovani and L. infantum are responsible for life-threatening visceral leishmaniasis. An estimated 20 million individuals are infected with kinetoplastid pathogens, resulting in extensive suffering and around 95,000 deaths per year1. Despite this considerable disease burden, effective drug treatments for these parasites are lacking or inadequate and new therapies are required2,3.

Although these protozoans are transmitted by different insects and the human diseases they cause are clinically distinctive, much of their molecular and cellular biology is similar1. They are defined by the presence of a DNA-containing region, the ‘kinetoplast’, in their single large mitochondrion; have similar genomic organization and cellular structures (e.g. a single flagellum for motion, and glycosomes); and undergo morphological changes during their life cycles in the insect and vertebrate hosts. The genome of each parasite exceeds 8,000 genes, more than 6,000 being common orthologs4. Analysis of the genomes of L. major, T. cruzi and T. brucei (known as TriTryp) has revealed many common core metabolic functions as well as pathways that might reflect specific adaptations to environments within their insect and vertebrate hosts4. Strikingly, approximately 50% of these genomes encode for hypothetical proteins that do not resemble orthologs in the human genome1. In addition, several human protein classes are not represented in kinetoplastid genomes, e.g. no orthologs have been found for tyrosine kinases5. These differences suggest that there may be essential proteins that can be exploited as selective targets for chemotherapy.

This paper reports the application of whole-cell phenotypic assays against L. donovani, T. cruzi and T. brucei to screen the GlaxoSmithKline HTS diversity set of 1.8 million compounds. This is the first parallel HTS program which has been disclosed for any pharma compound set against the three kinetoplastids most relevant to human disease. Three kinetoplastid chemical boxes have been assembled and all data are publically available to encourage research and drug discovery efforts in combating these devastating infections.