Christine Latour

Polymorphism of Plasmodium falciparum Na+/H+ exchanger is indicative of a low in vitro quinine susceptibility in isolates from Viet Nam

BackgroundThe Plasmodium falciparum NA+/H+ exchanger (pfnhe1, gene PF13_0019) has recently been proposed to influence quinine (QN) susceptibility. However, its contribution to QN resistance seems to vary geographically depending on the genetic background of the parasites. Here, the role of this gene was investigated in in vitro QN susceptibility of isolates from Viet Nam.MethodNinety-eight isolates were obtained from three different regions of the Binh Phuoc and Dak Nong bordering Cambodia provinces during 2006-2008. Among these, 79 were identified as monoclonal infection and were genotyped at the microsatellite pfnhe1 ms4760 locus and in vitro QN sensitivity data were obtained for 51 isolates. Parasite growth was assessed in the field using the HRP2 immunodetection assay.ResultsSignificant associations were found between polymorphisms at pfnhe1 microsatellite ms4760 and susceptibility to QN. Isolates with two or more DNNND exhibited much lower susceptibility to QN than those harbouring zero or one DNNND repeats (median IC50 of 682 nM versus median IC50 of 300 nM; p = 0.0146) while isolates with one NHNDNHNNDDD repeat presented significantly reduced QN susceptibility than those who had two (median IC50 of 704 nM versus median IC50 of 375 nM; p < 0.01). These QNR associated genotype features were mainly due to the over representation of profile 7 among isolates (76.5%). The majority of parasites had pfcrt76T and wild-type pfmdr1 (> 95%) thus preventing analysis of associations with these mutations. Interestingly, area with the highest median QN IC50 showed also the highest percentage of isolates carrying the pfnhe1 haplotype 7.ConclusionsThe haplotype 7 which is the typical Asian profile is likely well-adapted to high drug pressure in this area and may constitute a good genetic marker to evaluate the dissemination of QNR in this part of the world.

Diastereoselective synthesis of potent antimalarial cis-β-lactam agents through a [2 + 2] cycloaddition of chiral imines with a chiral ketene

The effect of double asymmetric induction for the synthesis of new cis-β-lactams by [2 + 2] cycloaddition reactions of chiral imines with a chiral ketene was investigated. The cycloaddition reaction was found to be totally diastereoselective leading exclusively to the formation of the cis-β-lactam derivatives. The newly synthesized cycloadducts were evaluated for their antimalarial activities against Plasmodium falciparum K14 resistant strain with moderate to excellent IC50 values varying from 8 to 50 μM. Of the fifteen β-lactams tested, four showed IC50 ≤ 11 μM.

Synthesis and biological evaluation of some novel diastereoselective benzothiazole β-lactam conjugates

Highly diastereoselective synthesis of some novel benzothiazole-substituted β-lactam hybrids was achieved starting from (benzo[d]thiazol-2-yl)phenol as an available precursor. This is the first time (benzo[d]thiazol-2-yl)phenoxyacetic acid has been used as ketene source in synthesizing monocyclic 2-azetidinones. These compounds were evaluated for their antimicrobial activities against a large panel of Gram-positive and Gram-negative bacterial strains and moderate activities were encountered. Antimalarial data revealed that adding methoxyphenyl or ethoxyphenyl group on the β-lactam ring makes compounds that are more potent. Moreover, hemolytic activity and mammalian cell toxicity survey of the compounds showed their potential as a medicine.

Synthesis and antimicrobial/antimalarial activities of novel naphthalimido trans-β-lactam derivatives

This paper describes for the first time the synthesis and microbiological assessment of some new β-lactam derivatives containing a 1,8-naphthalimide functional group. These compounds were obtained through a [2 + 2] cyclocondensation (Staudinger reaction) of a ketene derived from 2-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl) acetic acid (Alrestatin) and various N-arylimines. The reaction was totally diastereoselective leading exclusively to the formation of trans-β-lactam adducts 3a–l, which were characterized by FT-Infra Red, 1H NMR, 13C NMR, mass spectrometry, elemental analyses, and X-ray crystallography, and then individually evaluated for antibacterial and antimalarial activities. Two of the β-lactams, 3c and 3l, afforded IC50 values of 3 and 5 µM, respectively, against Plasmodium falciparum K1 resistant strain.

Synthesis of an organo-ruthenium aminoquinoline-trioxane hybrid and evaluation of its activity against Plasmodium falciparum and its toxicity toward normal mammalian cells

A new hybrid compound 5 containing a ruthenocene, a 4-aminoquinoline, and a 1,2,4-trioxane within a single molecular structure has been synthesized and evaluated for antimalarial potential. In order to ascertain the role of each component of hybrid 5, its antimalarial activity has been measured against chloroquine-resistant and chloroquine-sensitive strains of Plasmodium falciparum in comparison with those of chloroquine, artemisinin, a ruthenocene-trioxane compound 9 not containing an aminoquinoline, the precursor trioxane ketone 4, and a trioxane dimer 10. Hybrid 5 displays high antimalarial activity, in the mid to low nanomolar IC50 range, and low cytotoxicity toward healthy mammalian cells, which translates into good selectivity indexes. The potency of 5 is consistently higher than those of chloroquine, the parent metal-free trioxane, and compound 9, the structural intermediate featuring a ruthenocene moiety bound to the trioxane but lacking the aminoquinoline. These results validate our hypothesis that it is the combination of the aminoquinoline, the ruthenocenyl moiety, and the trioxane in a single molecule that provides the enhanced antiplasmodial activity, and highlight the concept of hybrid compounds as a strategy that deserves further attention.Graphical Abstract

Prevalence of Plasmodium falciparum parasites resistant to sulfadoxine/pyrimethamine in the Democratic Republic of the Congo: emergence of highly resistant pfdhfr/pfdhps alleles

Background In 2005, the Democratic Republic of the Congo (DRC) switched to artesunate/amodiaquine as the first-line antimalarial in response to increasing sulfadoxine/pyrimethamine resistance and adopted intermittent preventive treatment using sulfadoxine/pyrimethamine in pregnancy. Objectives To determine the prevalence of molecular markers of sulfadoxine/pyrimethamine resistance in southwestern DRC 10 years after the new policy was instituted. Methods From March 2014 to December 2015, blood samples were collected from symptomatic patients presenting to outpatient centres in urban and rural areas. A total of 2030 confirmed Plasmodium falciparum isolates were genotyped at codons associated with sulfadoxine/pyrimethamine resistance. Results The prevalence of pfdhfr-N51I, C59R and S108N and pfdhps-A437G mutations was consistently high; the prevalence of the pfdhps-K540E mutation was low but increased since its first report in 2008 in the same region, reaching 17.6% by 2015. The pfdhps-A581G mutation increased from ∼4.5% in 2014 to ∼14.0% in 2015 at urban sites while in rural areas it remained low (∼4.0%). The mutations pfdhfr-I164L and pfdhps-A613S were detected for the first time in DRC. Also, 11 (0.8%) isolates revealed the presence of the newly described pfdhps-I431V mutation. Combining pfdhfr and pfdhps alleles, quintuple and sextuple mutations were observed, with the emergence of septuple (IRNI/IAGEGA)- and octuple (IRNI/VAGKGS)-mutant genotypes. Conclusions Intermittent preventive treatment using sulfadoxine/pyrimethamine during pregnancy remains warranted in southwestern DRC. However, the expansion of pfdhps-K540E mutation and emergence of mutants that cause higher levels of sulfadoxine/pyrimethamine resistance is concerning and may present a challenge for future preventive interventions in the country.

Synthesis of New 4-Aminoquinolines and Evaluation of Their In Vitro Activity against Chloroquine-Sensitive and Chloroquine-Resistant Plasmodium falciparum

The efficacy of chloroquine, once the drug of choice in the fight against Plasmodium falciparum, is now severely limited due to widespread resistance. Amodiaquine is one of the most potent antimalarial 4-aminoquinolines known and remains effective against chloroquine-resistant parasites, but toxicity issues linked to a quinone-imine metabolite limit its clinical use. In search of new compounds able to retain the antimalarial activity of amodiaquine while circumventing quinone-imine metabolite toxicity, we have synthesized five 4-aminoquinolines that feature rings lacking hydroxyl groups in the side chain of the molecules and are thus incapable of generating toxic quinone-imines. The new compounds displayed high in vitro potency (low nanomolar IC50), markedly superior to chloroquine and comparable to amodiaquine, against chloroquine-sensitive and chloroquine-resistant strains of P. falciparum, accompanied by low toxicity to L6 rat fibroblasts and MRC5 human lung cells, and metabolic stability comparable or higher than that of amodiaquine. Computational studies indicate a unique mode of binding of compound 4 to heme through the HOMO located on a biphenyl moeity, which may partly explain the high antiplasmodial activity observed for this compound.