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Antifolate Agents Against Wild and Mutant Strains of Plasmodium falciparum.

ABSTRACT: Plasmodium falciparum dihydrofolate reductase is an important target for antimalarial chemotherapy. The emergence of resistance has significantly reduced the efficacy of the classic antifolate drugs cycloguanil and pyrimethamine. In this paper we report new dihydrofolate reductase inhibitors identified using molecular modelling principles with the goal of designing new antifolate agents active against both wild and tetramutant dihydrofolate reductase strains three series of trimethoprim analogues were designed, synthesised and tested for biological activity. Pyrimethamine and cycloguanil have been reported to loose efficacy because of steric repulsion in the active site pocket produced due to mutation in Plasmodium falciparum dihydrofolate reductase. The synthesised molecules have sufficient flexibility to withstand this steric repulsion to counteract the resistance. The molecules have been synthesised by conventional techniques and fully characterised by spectroscopic methods. The potency of these molecules was evaluated by in vitro enzyme specific assays. Some of the molecules were active in micromolar concentrations and can easily be optimised to improve binding and activity.

SUBMITTER: Shaikh MS

PROVIDER: S-EPMC4023280 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Antifolate Agents Against Wild and Mutant Strains of Plasmodium falciparum.

Shaikh M S MS Rana J J Gaikwad D D Leartsakulpanich U U Ambre Premlata K PK Pissurlenkar R R S RR Coutinho E C EC

Indian journal of pharmaceutical sciences 20140301 2

Plasmodium falciparum dihydrofolate reductase is an important target for antimalarial chemotherapy. The emergence of resistance has significantly reduced the efficacy of the classic antifolate drugs cycloguanil and pyrimethamine. In this paper we report new dihydrofolate reductase inhibitors identified using molecular modelling principles with the goal of designing new antifolate agents active against both wild and tetramutant dihydrofolate reductase strains three series of trimethoprim analogue ...[more]

PMID: 24843184

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Project description:BACKGROUND:Artesunate plus sulphadoxine-pyrimethamine (AS+SP) is now first-line treatment for Plasmodium falciparum infection in several south Asian countries, including Afghanistan. Molecular studies provide a sensitive means to investigate the current state of drug susceptibility to the SP component, and can also provide information on the likely efficacy of other potential forms of artemisinin-combination therapy. METHODS:During the years 2007 to 2010, 120 blood spots from patients with P. falciparum malaria were obtained in four provinces of Afghanistan. PCR-based methods were used to detect drug-resistance mutations in dhfr, dhps, pfcrt and pfmdr1, as well as to determine copy number of pfmdr1. RESULTS:The majority (95.5%) of infections had a double mutation in the dhfr gene (C59R, S108N); no mutations at dhfr positions 16, 51 or 164 were seen. Most isolates were wild type across the dhps gene, but five isolates from the provinces of Kunar and Nangarhar in eastern Afghanistan had the triple mutation A437G / K540E / A581G; all five cases were successfully treated with three receiving AS+SP and two receiving dihydroartemisinin-piperaquine. All isolates showed the pfcrt SVNMT chloroquine resistance haplotype. Five of 79 isolates had the pfmdr1 N86Y mutation, while 52 had pfmdr1 Y184F; positions 1034, 1042 and 1246 were wild type in all isolates. The pfmdr1 gene was not amplified in any sample. CONCLUSIONS:This study indicates that shortly after the adoption of AS+SP as first-line treatment in Afghanistan, most parasites had a double mutation haplotype in dhfr, and a small number of isolates from eastern Afghanistan harboured a triple mutation haplotype in dhps. The impact of these mutations on the efficacy of AS+SP remains to be assessed in significant numbers of patients, but these results are clearly concerning since they suggest a higher degree of SP resistance than previously detected. Further focused molecular and clinical studies in this region are urgently required.

Project description:BACKGROUND:Resistance to anti-malarials is a major threat to the control and elimination of malaria. Sulfadoxine-pyrimethamine (SP) anti-malarial treatment was used as a national policy for treatment of uncomplicated falciparum malaria in Thailand from 1973 to 1990. In order to determine whether withdrawal of this antifolate drug has led to restoration of SP sensitivity, the prevalence of genetic markers of SP resistance was assessed in historical Thai samples. METHODS:Plasmodium falciparum DNA was collected from the Thailand-Myanmar, Thailand-Malaysia and Thailand-Cambodia borders during 2008-2016 (N?=?233). Semi-nested PCR and nucleotide sequencing were used to assess mutations in Plasmodium falciparum dihydrofolate reductase (pfdhfr), P. falciparum dihydropteroate synthase (pfdhps). Gene amplification of Plasmodium falcipaurm GTP cyclohydrolase-1 (pfgch1) was assessed by quantitative real-time PCR. The association between pfdhfr/pfdhps mutations and pfgch1 copy numbers were evaluated. RESULTS:Mutations in pfdhfr/pfdhsp and pfgch1 copy number fluctuated overtime through the study period. Altogether, 14 unique pfdhfr-pdfhps haplotypes collectively containing quadruple to octuple mutations were identified. High variation in pfdhfr-pfdhps haplotypes and a high proportion of pfgch1 multiple copy number (51% (73/146)) were observed on the Thailand-Myanmar border compared to other parts of Thailand. Overall, the prevalence of septuple mutations was observed for pfdhfr-pfdhps haplotypes. In particular, the prevalence of pfdhfr-pfdhps, septuple mutation was observed in the Thailand-Myanmar (50%, 73/146) and Thailand-Cambodia (65%, 26/40) border. In Thailand-Malaysia border, majority of the pfdhfr-pfdhps haplotypes transaction from quadruple (90%, 9/10) to quintuple (65%, 24/37) during 2008-2016. Within the pfdhfr-pfdhps haplotypes, during 2008-2013 the pfdhps A/S436F mutation was observed only in Thailand-Myanmar border (9%, 10/107), while it was not identified later. In general, significant correlation was observed between the prevalence of pfdhfr I164L (??= 0.213, p-value?=?0.001) or pfdhps K540E/N (? = 0.399, p-value???0.001) mutations and pfgch1 gene amplification. CONCLUSIONS:Despite withdrawal of SP as anti-malarial treatment for 17 years, the border regions of Thailand continue to display high prevalence of antifolate and anti-sulfonamide resistance markers in falciparum malaria. Significant association between pfgch1 amplification and pfdhfr (I164L) or pfdhps (K540E) resistance markers were observed, suggesting a compensatory mutation.

Dataset Information

Antifolate Agents Against Wild and Mutant Strains of Plasmodium falciparum.

Publications

Antifolate Agents Against Wild and Mutant Strains of Plasmodium falciparum.

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