Abstract
In various malaria-endemic regions, the appearance of resistance has precluded the use of pyrimidine-based antifolate drugs. Here, a three-step fragment screening was used to identify new non-pyrimidine Plasmodium falciparum dihydrofolate reductase (PfDHFR) inhibitors. Starting from a 1163-fragment commercial library, a two-step differential scanning fluorimetry screen identified 75 primary fragment hits. Subsequent enzyme inhibition assay identified 11 fragments displaying IC50 in the 28-695 μM range and selectivity for PfDHFR. In addition to the known pyrimidine, three new anti-PfDHFR chemotypes were identified. Fragments from each chemotype were successfully co-crystallized with PfDHFR, revealing a binding in the active site, in the vicinity of catalytic residues, which was confirmed by molecular docking on all fragment hits. Finally, comparison with similar non-hit fragments provides preliminary input on available growth vectors for future drug development.
Keywords:
Plasmodium falciparum; Malaria; dihydrofolate reductase; fragment-based screening; small molecule inhibitors.
MeSH terms
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Antimalarials / chemical synthesis
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Antimalarials / chemistry
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Antimalarials / pharmacology*
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Crystallography, X-Ray
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Dose-Response Relationship, Drug
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Drug Discovery*
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Drug Evaluation, Preclinical
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Enzyme Inhibitors / chemical synthesis
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Enzyme Inhibitors / chemistry
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Enzyme Inhibitors / pharmacology*
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Models, Molecular
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Molecular Docking Simulation
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Molecular Structure
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Plasmodium falciparum / drug effects*
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Plasmodium falciparum / enzymology
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Proguanil / chemical synthesis
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Proguanil / chemistry
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Proguanil / pharmacology
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Protozoan Proteins / antagonists & inhibitors*
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Protozoan Proteins / isolation & purification
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Protozoan Proteins / metabolism
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Pyrimethamine / chemical synthesis
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Pyrimethamine / chemistry
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Pyrimethamine / pharmacology
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Structure-Activity Relationship
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Tetrahydrofolate Dehydrogenase / isolation & purification
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Tetrahydrofolate Dehydrogenase / metabolism
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Triazines / chemical synthesis
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Triazines / chemistry
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Triazines / pharmacology
Substances
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Antimalarials
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Enzyme Inhibitors
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Protozoan Proteins
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Triazines
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cycloguanil
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DHFR protein, Plasmodium falciparum
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Tetrahydrofolate Dehydrogenase
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Proguanil
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Pyrimethamine
Grants and funding
This research was supported by grants from the Medicines for Malaria Venture (MMV), BIOTEC, NSTDA’s Cluster and Program Management (P1450883) and NSTDA’s Researcher Chair Grant (P1850116).