Trypanosoma cruzi is the etiological agent of Chagas disease, a pathogenesis that affects 6 to 7 million
people worldwide, mainly in Latin America. There is no effective treatment for chronic Chagas disease and
resistant strains to the current frontline treatment have already emerged. There is a growing need for new
pharmacological alternatives to treat this disease.
This proposal exploits a target-based approach to search for lead compounds against Chagas
disease. Trypanosoma cruzi dihydroorotate dehydrogenase (TcDHODH) is a flavin mononucleotide
containing enzyme, which catalyzes the oxidation of L-dihydroorotate to orotate, the fourth step and only
redox reaction in the de novo biosynthesis of pyrimidine nucleotides. TcDHODH was also described as a
soluble fumarate reductase playing a role in connecting succinate/fumarate metabolism to de novo pyrimidine
biosynthesis. DHODH has already been extensively exploited as a drug target for proliferative and parasitic
diseases. Genetic studies have shown that DHODH is essential for T. cruzi survival providing evidence that
this enzyme is an attractive target for the development of antichagasic drugs.
The goal of this project is to chemically validate TcDHODH as a new drug target for Chagas disease
and to provide leads for drug development. Our approach combines multiple techniques including
computational chemistry, enzymology, structural biology, parasitology, and medicinal chemistry to develop
selective and covalent inhibitors of TcDHODH. Initially, we will seek to gain a greater understanding of the
DHODH hot spots by using solvent mapping to characterize the binding pockets with the flexible active-site
loop open and closed. This information will help strengthen the computational modeling, and subsequent
Covalent inhibition of enzymes based on the identification of a set of cysteine targeting covalent
warheads including acrylamides, vinyl sulfones and nitriles, has been shown to be a successful approach in
drug discovery pipelines. In our proposal, an initial set of putative inhibitors that incorporate an acrylamide
warhead have already been rationally designed to target the TcDHODH active-site cysteine. Predicted
inhibitors will be evaluated for inhibitory potency and mechanism of inhibition against TcDHODH, cytotoxicity
and its anti-parasitic effects in cell culture. X-ray crystallography, fragment screening and medicinal chemistry
will be combined to provide the chemical basis for the synthesis of a new generation of potent, selective, and
drug-like inhibitors. The top 3 inhibitors that meet lead criteria (including PK and tolerability) will have their
efficacy evaluated by DNDi via an in-kind contribution to the project.
This proposal represents an unprecedent initiative to significantly contribute to building capacity in the
field of drug discovery in Brazil, a field of research still very incipient in developing countries.