Blocking <i>Plasmodium</i> Merozoite Invasion of Red Blood Cells: Molecular Docking Analysis of Small Molecule Inhibitors of the RH5-CyRPA-RIPR Complex

Abstract

Malaria, caused by Plasmodium parasites, remains life-threatening, with Plasmodium falciparum responsible for severe cases. The parasite’s invasion of Red Blood Cells (RBCs) is critical for infection. The interaction between Reticulocyte Binding Protein Homologue 5 (RH5), Basigin, monoclonal antibodies and Cysteine-Rich Protective Antigen (CyRPA) with glycan on RBCs is essential for this process. This study aims to identify small molecules inhibiting the RH5-CyRPA-RIPr invasion complex. A library of 2299 compounds from FDA-approved drugs and African natural products in the ZINC database was screened using molecular docking. Binding sites for Basigin, monoclonal antibodies and glycans on RH5 and CyRPA were targeted, with binding affinity cutoffs of −8.5 kcal/mol for monoclonal antibodies and −7.0 kcal/mol for CyRPA and Basigin. Compounds were assessed for pharmacokinetics, solubility, drug-likeness, lead-likeness and biological activity using the PASS online server. Molecular dynamics simulations and free energy calculations evaluated stability and binding efficiency. Nine hits for RH5 and three for CyRPA showed favorable stability and anti-protozoal activity (up to 0.65). African natural products exhibited similarities with drugs like Nequinate and Cyanidin, supporting further research. Promising small molecules were identified as potential inhibitors of P. falciparum invasion, laying a foundation for experimental validation and drug development.