Estudo in silico de novos compostos contra inosina monofosfato desidrogenase de Cryptosporidium parvum

Abstract

Cryptosporidiosis is a zoonotic disease caused by protozoa of the genus Cryptosporidium, with C. parvum being of particular interest for public and animal health. It is a diarrheal disease affecting various hosts, including humans (especially children and immunocompromised individuals) and livestock. The commercially available drug for the treatment of cryptosporidiosis is nitazoxanide (NTZ), which has moderate efficacy in individuals infected with the human immunodeficiency virus (HIV). In this context, the aim of the present study was to assess the potential inhibitory activity of compounds from a Brazilian public library (BraCoLi) against the target biomacromolecule inosine monophosphate dehydrogenase (IMPDH) of C. parvum, in an effort to discover new, effective, and safe drug candidates for the treatment of cryptosporidiosis. The methodological approach used was virtual screening of 1,176 compounds against the parasite's IMPDH enzyme. Comparative modeling was performed between an amino acid sequence of C. parvum IMPDH and orthologous sequences to construct a complete three-dimensional model. Molecular docking was carried out to assess the interactions between the compounds and two distinct enzyme sites (the inosine monophosphate [IMP] ligand site and the nicotinamide adenine dinucleotide [NAD+] cofactor site), using AutoDock Vina and DockThor software. Three parameters were evaluated: (i) binding affinity (Kcal/mol); (ii) theoretical inhibition constant (cKi); and (iii) Z-score. In silico analysis were performed on the physicochemical and pharmacokinetic parameters, antiparasitic and/or antiprotozoal biological activity, and selectivity against mammalian enzymes. Based on the molecular docking results and interactions between the ligands and the protein, three compounds were selected for the IMP catalytic site (BR010017, BR020113, and BR020128), and two (BR010304 and BR010518) for the NAD+ cofactor site. Regarding physicochemical properties, all compounds met Lipinski's "Rule of Five." The promising compounds for the NAD+ catalytic site exhibited antiprotozoal biological activity. In the toxicity profile, only the compound BR010518 was found to be safe. Regarding pharmacokinetic parameters, BR020128 was the only compound to exhibit a negative Clearance value. Despite these in silico violations, it is crucial to validate these results through in vitro and in vivo tests to confirm the efficacy and safety of the promising compounds.