Targeting Plasmodium falciparum Single-Stranded DNA-Binding Protein: Discovery of New Scaffold Compounds Effective against Drug-Sensitive and Artemisinin-Resistant Strains.

Abstract

Resistance to frontline antimalarials by malaria parasites is a major concern, prompting the search for novel antimalarial compounds targeting new drug targets. One promising target is the single-stranded DNA-binding protein (PfSSB) of Plasmodium falciparum, crucial for DNA replication process in apicoplast, an essential organelle. Using an integrative approach, PPG and 9-HPF are identified, which inhibit the DNA binding property of PfSSB and exhibit antimalarial activity. Computational analyses reveal that both compounds possess strong binding affinity and favorable drug-like properties. Biolayer interferometry assay and the gel retardation assays demonstrate that they have a stronger binding affinity and disrupt PfSSB's ssDNA binding ability. PPG and 9-HPF show antimalarial activity against drug-sensitive P. falciparum (3D7) with IC₅₀ values of 54.95 and 9.13 μM, respectively, and they can also effectively inhibit artemisinin-resistant P. falciparum (C580Y) with a resistance index of 0.79 and 1.26, respectively. MTT cytotoxicity assays confirm that both compounds are nontoxic, and structural similarity analysis indicates that they are distinct from existing antimalarials, reducing cross-resistance risk. Additionally, virtual screening of 59,807 compounds with similar structures to PPG and 9-HPF identifies candidates with higher affinities for PfSSB. This study identifies PPG and 9-HPF as structurally distinct antimalarials with the potential to combat drug-resistant P. falciparum.