Discovery of rigid biphenyl Plasmodium falciparum DHFR inhibitors using a fragment linking strategy†
Marie Hoarau,Patpanat Sermmai,Thaveechai Varatthan,Ratthiya Thiabma,Tararat Jantra,Roonglawan Rattanajak,Danoo Vitsupakorn,Jarunee Vanichtanankul,Siriporn Saepua,Yongyuth Yuthavong,Chawanee Thongpanchang,Sumalee Kamchonwongpaisan
RSC Medicinal Chemistry Pub Date : 07/24/2023 00:00:00 , DOI:10.1039/D3MD00242J
Abstract

Plasmodium falciparum dihydrofolate reductase (PfDHFR), a historical target for antimalarials, has been considered compromised due to resistance inducing mutations caused by pyrimethamine (PYR) overexposure. The clinical candidate P218 has demonstrated that inhibitors could efficiently target both PYR-sensitive and PYR-resistant parasites through careful drug design. Yet, P218 clinical development has been limited by its pharmacokinetic profile, incompatible with single dose regimen. Herein, we report the design of new PfDHFR inhibitors using fragment-based design, aiming at improved lipophilicity and overall drug-like properties. Fragment-based screening identified hits binding in the pABA site of the enzyme. Using structure-guided design, hits were elaborated into leads by fragment linking with 2,4-diaminopyrimidine. Resulting compounds display nM range inhibition of both drug-sensitive and resistant PfDHFR, high selectivity against the human isoform, drug-like lipophilicity and metabolic stability. Compound 4 and its ester derivative 3 kill blood stage TM4/8.2 parasite at nM concentrations while showing no toxicity against Vero cells.

Graphical abstract: Discovery of rigid biphenyl Plasmodium falciparum DHFR inhibitors using a fragment linking strategy