Repurposing FDA-Approved Anticancer Drugs Offers a Strategy to Target Mutant-Type Malaria by Inhibiting Parasite DHFR Without Affecting Human DHFR

Abstract

Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) is a well-defined antimalarial target of antifolate drugs. However, the emergence of parasite resistance to antifolate medications is the primary reason for the unsuccessful treatment of malaria. In this work, repurposing of anticancer drugs through virtual screening was conducted to identify critical interactions with quadruple type (qmPfDHFR-TS) and hDHFR (human dihydrofolate reductase). Three anticancer drugs-pralatrexate (PRA), pemetrexed (PME), and dasatinib (DAS) - exhibited significant binding interactions with qmPfDHFR-TS and hDHFR. The binding stability of PRA and the reference compound, P218, was determined using principal component analysis (PCA) and free energy landscape (FEL) analyses. Additionally, the key binding interaction patterns of qmPfDHFR-TS and hDHFR was further investigated through quantum chemical calculations. The PRA complex and P218 complex display meaningful H-bond interactions with Asp54, Arg59, and Arg122, as well as a π–π interaction with Phe58, in the qmPfDHFR-TS structure. For hDHFR, it was found that P218 and PRA do not establish H-bond interactions with Arg70, which is the conserved residue in hDHFR. Furthermore, this discovery was validated by conducting enzyme inhibition tests, which demonstrated the capacity of these compounds to inhibit PfDHFR enzymes. As a result, pralatrexate shows potential as an effective inhibitor against the mutant type of the PfDHFR enzyme.