Repurposing of antimalarial drugs in the treatment of schistosomiasis based on the selective inhibition of the enzyme dihydroorotate dehydrogenase.

Author(s)

Felipe Antunes Calil

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2019-02-08

Examining board members

Maria Cristina Nonato; Rafael Victório Carvalho Guido; Otavio Henrique Thiemann; Daniela Barretto Barbosa Trivella

• Advisor: Maria Cristina Nonato

Abstract

compounds which display antimalarial activity as potential leads for the discovery of new therapeutics for schistosomiasis. The compounds were selected based on their ability to inhibit the enzyme dihydroorotate dehydrogenase (DHODH). DHODH enzyme participates in the de novo synthesis of pyrimidine nucleotides and it is a validated therapeutic target for many diseases. Our studies identified several compounds as potent inhibitors of Schistosoma mansoni dihydroorotate dehydrogenase (SmDHODH). A total of 34 compounds were identified as inhibitors and mechanistic studies allowed us to sort them into three classes: competitive, non-competitive and mixed-type inhibitors. The inhibitory studies together with thermal stability assays suggest that not only chemical and steric distribution of the binding pocket is important but dynamics of the N-terminal helical domain plays an important role in ligand binding. The selectivity index (SI) was estimated by evaluating the best hits against the human homologue enzyme (HsDHODH). The results identified compound 17 (2-hydroxy-3-isopentylnaphthalene-1,4-dione) as the best compound for SmDHODH selective inhibition (IC50 = 23 ± 4 nM, SI 30.83). In vitro studies using adult S. mansoni worms were used to identify the impact of selected compounds on the morphology and schistosomicidal activity. Results show a potent activity against the parasites, especially for the compound atovaquone, an antimalarial drug. Plasmodium falciparum DHODH (PfDHODH), a validated target against malaria, was also focus of the present work. We developed a pipeline to evaluate potency, selectivity and mechanism of inhibition. In our work, different classes of compounds were assayed and identified ligands had their mechanism of inhibition determined. Crystallization of PfDHODH?loop (where the flexible loop from Gly285 to Lys294 was removed) was successfully achieved and will provide the structural basis to understand potency and selectivity of ligands. Our results support our original proposal of repurposing compounds and/or its analogues, originally developed against PfDHODH, to search for alternative strategies to treat schistosomiasis. (AU)

• FAPESP's process: 15/25099-5 - Antimalarial drug repositioning in the schistosomiasis treatment based on the selective inhibition of the enzyme dihydroorotate dehydrogenase
• Grantee: Felipe Antunes Calil
• Support Opportunities: Scholarships in Brazil - Doctorate