In Vitro Activity of Antifolate and Polymorphism in Dihydrofolate Reductase of<i>Plasmodium falciparum</i>Isolates from the Kenyan Coast: Emergence of Parasites with Ile-164-Leu Mutation

Kiara, Steven M.; Okombo, John; Masseno, Victor; Mwai, Leah; Ochola, Isabella; Borrmann, Steffen; Nzila, Alexis

doi:10.1128/aac.00308-09

Cited by 45 publications

(35 citation statements)

References 58 publications

(64 reference statements)

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“…For pyrimethamine, the IC 50 value of 12 nM lies within the range of reported inhibitory concentrations (< 10 to 480 nM) in different assay types [39][40][41][42][43][44]. Also for WR99210, the IC 50 of 0.039 nM was very near to those previously reported for different parasite lines (0.075-0.21 nM) [45][46][47]. Trimethoprim IC 50 concentrations that have been reported to range from 130 nM to 30 lM in different assay types of chloroquine sensitive and resistant strains in medium depleted of folic acid and pABA are in harmony with our observation (1.2 lM) [47][48][49].…”

Section: Discussionsupporting

confidence: 81%

MRP1 mediates folate transport and antifolate sensitivity in Plasmodium falciparum

et al. 2016

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Edited by Ned ManteiMultidrug resistance-associated proteins (MRP) of Plasmodium falciparum have been associated with altered drug sensitivity. Knowledge on MRP substrate specificity is indispensible for the characterization of resistance mechanisms and identifying its physiological roles. An untargeted metabolomics approach detected decreased folate concentrations in red blood cells infected with schizont stage parasites lacking expression of MRP1. Furthermore, a tenfold decrease in sensitivity toward the folate analog methotrexate was detected for parasites lacking MRP1. PfMRP1 is involved in the export of folate from parasites into red blood cells and is therefore a relevant factor for efficient malaria treatment through the folate pathway.

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Section: Discussionsupporting

confidence: 81%

MRP1 mediates folate transport and antifolate sensitivity in Plasmodium falciparum

et al. 2016

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“…In agreement with these data, and as discussed in our previous report, no WT isolates were found, and more than 72% of the tested isolates carried triple mutations in Pfdhfr (S108N, N51I, and C59R). Interestingly, one isolate carried the four mutations (S108N, N51I, C59R, and I164L), mutations present in the V1S form (19). In sharp contrast to the results obtained with PM, QN254 was potent against all isolates, with a median IC 50 of 9.55 nM.…”

Section: Resultscontrasting

confidence: 47%

“…To further demonstrate that QN254 is active against P. falciparum even in areas of widespread PM drug (19). For comparison purposes, in Table 2, we report again the data pertaining to PM along with the previously published results obtained with QN254 (19).…”

Section: Resultsmentioning

confidence: 72%

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Preclinical Evaluation of the Antifolate QN254, 5-Chloro-N′6′-(2,5-Dimethoxy-Benzyl)-Quinazoline-2,4,6-Triamine, as an Antimalarial Drug Candidate

Nzila

Rottmann

Chitnumsub

et al. 2010

Antimicrob Agents Chemother

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Drug resistance against dihydrofolate reductase (DHFR) inhibitors-such as pyrimethamine (PM)-hasnow spread to almost all regions where malaria is endemic, rendering antifolate-based malaria treatments highly ineffective. We have previously shown that the di-amino quinazoline QN254 [5-chloro-N6-(2,5-dimethoxy-benzyl)-quinazoline-2,4,6-triamine] is active against the highly PM-resistant Plasmodium falciparum V1S strain, suggesting that QN254 could be used to treat malaria in regions with a high prevalence of antifolate resistance. Here, we further demonstrate that QN254 is highly active against Plasmodium falciparum clinical isolates, displaying various levels of antifolate drug resistance, and we provide biochemical and structural evidence that QN254 binds and inhibits the function of both the wild-type and the quadruple-mutant (V1S) forms of the DHFR enzyme. In addition, we have assessed QN254 oral bioavailability, efficacy, and safety in vivo. The compound displays favorable pharmacokinetic properties after oral administration in rodents. The drug was remarkably efficacious against Plasmodium berghei and could fully cure infected mice with three daily oral doses of 30 mg/kg. In the course of these efficacy studies, we have uncovered some dose limiting toxicity at higher doses that was confirmed in rats. Thus, despite its relative in vitro selectivity toward the Plasmodium DHFR enzyme, QN254 does not show the adequate therapeutic index to justify its further development as a single agent.

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“…Parasites with the triple mutant allele (N51I C59R S108N) have markedly reduced in vitro susceptibility to pyrimethamine, and the presence of this allele in a P. falciparum-infected patient increases the risk of SP therapeutic failure (15). The additional mutation I164L confers on the quadruple mutant a high level of resistance to pyrimethamine (22) and abrogates the clinical efficacy of SP, as observed in Southeast Asia, South America (31), and Africa (25). Although P. vivax and P. malariae infections are not usually treated directly with SP, the high frequency of mixed infections, such as P. falciparum-P. vivax or P. falciparum-P. malariae infections, that are not detected by microscopy examination (27) has inevitably exposed a large number of non-P. falciparum parasites to antifolate therapy in many areas.…”

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confidence: 99%

Reduced Impact of Pyrimethamine Drug Pressure on Plasmodium malariae Dihydrofolate Reductase Gene

Khim

Kim

Bouchier

et al. 2012

Antimicrob Agents Chemother

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Molecular investigations performed following the emergence of sulfadoxine-pyrimethamine (SP) resistance in Plasmodium falciparum have allowed the identification of the dihydrofolate reductase (DHFR) enzyme as the target of pyrimethamine. Although clinical cases of Plasmodium malariae are not usually treated with antifolate therapy, incorrect diagnosis and the high frequency of undetected mixed infections has probably exposed non-P. falciparum parasites to antifolate therapy in many areas. In this context, we aimed to assess the worldwide genetic diversity of the P. malariae dhfr gene in 123 samples collected in Africa and Asia, areas with different histories of SP use. Among the 10 polymorphic sites found, we have observed 7 new mutations (K55E, S58R, S59A, F168S, N194S, D207G, and T221A), which led us to describe 6 new DHFR proteins. All isolates from African countries were classified as wild type, while new mutations and haplotypes were recognized as exclusive to Madagascar (except for the double mutations at nucleotides 341 and 342 [S114N] found in one Cambodian isolate). Among these nonsynonymous mutations, two were likely related to pyrimethamine resistance: S58R (corresponding to C59R in P. falciparum and S58R in Plasmodium vivax; observed in one Malagasy sample) and S114N (corresponding to S108N in P. falciparum and S117N in P. vivax; observed in three Cambodian samples). Currently, in many parts of the globe, the emergence and spread of malaria parasites resistant to various antimalarial drugs recommended by the international organizations remain major factors threatening control efforts (41). Among the five Plasmodium species that affect humans (40), resistant Plasmodium falciparum parasites were first selected by chloroquine (CQ), a highly effective, fast-acting, and inexpensive 4-aminoquinoline widely used for several decades, in Southeast Asia or South America (29,44) in the 1960s. CQ-resistant parasites of the other Plasmodium species emerged much later: in 1989 for Plasmodium vivax (Papua New Guinea) (32) and in 2002 for Plasmodium malariae (Indonesia) (26). Following the introduction of the sulfadoxinepyrimethamine combination (SP) to replace CQ as the first-line treatment for uncomplicated P. falciparum malaria, the same scenario was observed. SP-resistant P. falciparum parasites were first detected in the 1980s (9, 19). Molecular investigations, based on laboratory and field isolates, demonstrated later that the resistance of P. falciparum to pyrimethamine was mediated by specific point mutations in the dihydrofolate reductase gene (dhfr) (30, 31). Currently, it is assumed that pyrimethamine resistance is conferred by the stepwise selection of a series of nonsynonymous point mutations (codons 50, 51, 59, and 164) from the S108N single mutant allele (24). Parasites with the triple mutant allele (N51I C59R S108N) have markedly reduced in vitro susceptibility to pyrimethamine, and the presence of this allele in a P. falciparum-infected patient increases the risk of SP therapeutic failure (15). The ...

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In Vitro Activity of Antifolate and Polymorphism in Dihydrofolate Reductase ofPlasmodium falciparumIsolates from the Kenyan Coast: Emergence of Parasites with Ile-164-Leu Mutation

Cited by 45 publications

References 58 publications

MRP1 mediates folate transport and antifolate sensitivity in Plasmodium falciparum

MRP1 mediates folate transport and antifolate sensitivity in Plasmodium falciparum

Preclinical Evaluation of the Antifolate QN254, 5-Chloro-N′6′-(2,5-Dimethoxy-Benzyl)-Quinazoline-2,4,6-Triamine, as an Antimalarial Drug Candidate

Reduced Impact of Pyrimethamine Drug Pressure on Plasmodium malariae Dihydrofolate Reductase Gene

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