title: Rational drug design approach for overcoming drug resistance: application to pyrimethamine resistance in malaria.
abstract: Pyrimethamine acts by selectively inhibiting malarial dihydrofolate reductase-thymidylate synthase (DHFR-TS). Resistance in the most important human parasite, Plasmodium falciparum, initially results from an S108N mutation in the DHFR domain, with additional mutation (most commonly C59R or N51I or both) imparting much greater resistance. From a homology model of the 3-D structure of DHFR-TS, rational drug design techniques have been used to design and subsequently synthesize inhibitors able to overcome malarial pyrimethamine resistance. Compared to pyrimethamine (Ki 1.5 nM) with purified recombinant DHFR fromP. falciparum, the Ki value of the m-methoxy analogue of pyrimethamine was 1.07 nM, but against the DHFR bearing the double mutation (C59R + S108N), the Ki values for pyrimethamine and the m-methoxy analogue were 71.7 and 14.0 nM, respectively. The m-chloro analogue of pyrimethamine was a stronger inhibitor of both wild-type DHFR (with Ki 0.30 nM) and the doubly mutant (C59R +S108N) purified enzyme (with Ki 2.40 nM). Growth of parasite cultures of P. falciparum in vitro was also strongly inhibited by these compounds with 50% inhibition of growth occurring at 3.7 microM for the m-methoxy and 0.6 microM for the m-chloro compounds with the K1 parasite line bearing the double mutation (S108N + C59R), compared to 10.2 microM for pyrimethamine. These inhibitors were also found in preliminary studies to retain antimalarial activity in vivo in P. berghei-infected mice.
authors.affiliation: School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Manchester M13 9PL, U.K.
authors.forename: J H
authors.initials: JH
authors.lastname: McKie
authors.forename: K T
authors.initials: KT
authors.lastname: Douglas
authors.forename: C
authors.initials: C
authors.lastname: Chan
authors.forename: S A
authors.initials: SA
authors.lastname: Roser
authors.forename: R
authors.initials: R
authors.lastname: Yates
authors.forename: M
authors.initials: M
authors.lastname: Read
authors.forename: J E
authors.initials: JE
authors.lastname: Hyde
authors.forename: M J
authors.initials: MJ
authors.lastname: Dascombe
authors.forename: Y
authors.initials: Y
authors.lastname: Yuthavong
authors.forename: W
authors.initials: W
authors.lastname: Sirawaraporn
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D015195:Drug Design; D004351:Drug Resistance; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D008288:Malaria / Q000188:drug therapy; D008297:Male; D051379:Mice; D009097:Multienzyme Complexes / Q000235:genetics / Q000494:pharmacology; D009154:Mutation; D010962:Plasmodium berghei; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D011739:Pyrimethamine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics / Q000494:pharmacology; D013940:Thymidylate Synthase / Q000235:genetics / Q000494:pharmacology
chemical_list: C111907:2,6-diamino-4-ethyl-5-(3-chlorophenyl)pyrimidine; D000962:Antimalarials; C111906:CC 83; D005493:Folic Acid Antagonists; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; C056930:thymidylate synthase-dihydrofolate reductase; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; D011739:Pyrimethamine