Identification of Potential Pteridin Reductase-1 Inhibitors for the Treatment of Leishmaniasis: A Bioinformatics Approach

Abstract

Background/Objectives: Leishmaniasis is an infectious disease caused by digenetic protozoa of the genus Leishmania, transmitted by infected female sandflies of the Phlebotominae subfamily. Current treatments are limited, relying on drugs that were not specifically developed for this disease and are often associated with high toxicity and elevated costs. Among alternative therapeutic strategies, antifolate compounds have been investigated due to their ability to inhibit dihydrofolate reductase (DHFR), an enzyme essential for folate metabolism in the parasite. However, the parasite circumvents DHFR inhibition through the activity of pteridine reductase-1 (PTR-1), which maintains folate reduction and ensures parasite survival. In this context, this study aimed to identify potential PTR-1 inhibitors in Leishmania major through in silico approaches. Methods: The methodology included virtual screening of molecular databases, Tanimoto similarity analysis, pharmacokinetic and toxicological predictions, and biological activity evaluation in silico. The most promising compounds were further analyzed via molecular docking. Results: The virtual screening resulted in 474 molecules, of which 4 structures (M601, M692, M700, and M703) showed high potential as PTR-1 inhibitors in Leishmania major throughout all stages of the methodology employed, especially in the results of molecular docking where they exhibited strong binding affinities and significant interactions with key residues of the target enzymes. Conclusions: This work provides a solid foundation for advancing these molecules into experimental validation, contributing to the development of safer and more effective therapeutic alternatives for the treatment of leishmaniasis.

Keywords: Leishmania major; methotrexate; molecular docking; pteridine reductase-1; virtual screening.

Scheme 1

Main methodological steps.

Figure 1

Pharmacophoric characteristics, obtained from alignment by the Pharmagist online server (yellow sphere: Acc; purple sphere: Aro; white sphere: Don).

Figure 2

Selected hits from pharmacokinetic and toxicological predictions.

Figure 3

RMSD values obtained through validation of the molecular docking method with their respective overlapping of theoretical (green) and computational (red) ligands. (a) MTX-1DLS, (b) MTX-1E7W, and (c) MTX-5X66.

Figure 4

Results of molecular docking assays showing interactions with amino acid residues of the DHFR target site.

Figure 5

Molecular docking results, evidencing the interactions with the amino acid residues of the PTR-1 target site.

Figure 6

Molecular docking results show interactions with amino acid residues of the TS target site.

Figure 7

The heatmap graph of binding affinity values (∆G) of promising structures and the commercial drug MTX, at the active sites of PDBs 1E7W, 1DLS, and 5X66.

Figure 8

Similarity analysis according to the electronic overlap between the M601 molecule (green), the MTX structure (red (a)), and BDB-1 (orange (b)).

Figure 9

Chemical structure of pteridine present in the structure of folic acid, biopterin, and methotrexate.