title: Failure of artesunate-mefloquine combination therapy for uncomplicated Plasmodium falciparum malaria in southern Cambodia.
abstract: BACKGROUND
  Resistance to anti-malarial drugs hampers control efforts and increases the risk of morbidity and mortality from malaria. The efficacy of standard therapies for uncomplicated Plasmodium falciparum and Plasmodium vivax malaria was assessed in Chumkiri, Kampot Province, Cambodia.
  
  
  METHODS
  One hundred fifty-one subjects with uncomplicated falciparum malaria received directly observed therapy with 12 mg/kg artesunate (over three days) and 25 mg/kg mefloquine, up to a maximum dose of 600 mg artesunate/1,000 mg mefloquine. One hundred nine subjects with uncomplicated vivax malaria received a total of 25 mg/kg chloroquine, up to a maximum dose of 1,500 mg, over three days. Subjects were followed for 42 days or until recurrent parasitaemia was observed. For P. falciparum infected subjects, PCR genotyping of msp1, msp2, and glurp was used to distinguish treatment failures from new infections. Treatment failure rates at days 28 and 42 were analyzed using both per protocol and Kaplan-Meier survival analysis. Real Time PCR was used to measure the copy number of the pfmdr1 gene and standard 48-hour isotopic hypoxanthine incorporation assays were used to measure IC50 for anti-malarial drugs.
  
  
  RESULTS
  Among P. falciparum infected subjects, 47.0% were still parasitemic on day 2 and 11.3% on day 3. The PCR corrected treatment failure rates determined by survival analysis at 28 and 42 days were 13.1% and 18.8%, respectively. Treatment failure was associated with increased pfmdr1 copy number, higher initial parasitaemia, higher mefloquine IC50, and longer time to parasite clearance. One P. falciparum isolate, from a treatment failure, had markedly elevated IC50 for both mefloquine (130 nM) and artesunate (6.7 nM). Among P. vivax infected subjects, 42.1% suffered recurrent P. vivax parasitaemia. None acquired new P. falciparum infection.
  
  
  CONCLUSIONS
  The results suggest that artesunate-mefloquine combination therapy is beginning to fail in southern Cambodia and that resistance is not confined to the provinces at the Thai-Cambodian border. It is unclear whether the treatment failures are due solely to mefloquine resistance or to artesunate resistance as well. The findings of delayed clearance times and elevated artesunate IC50 suggest that artesunate resistance may be emerging on a background of mefloquine resistance.
authors.affiliation: Naval Medical Research Unit #2, Komp, P2P/PLP-LITBANGKES, Jl, Percetakan Negara No, 29, Jakarta 10560, Indonesia. rogerswo@namrutwo.org
authors.forename: William O
authors.initials: WO
authors.lastname: Rogers
authors.forename: Rithy
authors.initials: R
authors.lastname: Sem
authors.forename: Thong
authors.initials: T
authors.lastname: Tero
authors.forename: Pheaktra
authors.initials: P
authors.lastname: Chim
authors.forename: Pharath
authors.initials: P
authors.lastname: Lim
authors.forename: Sinuon
authors.initials: S
authors.lastname: Muth
authors.forename: Duong
authors.initials: D
authors.lastname: Socheat
authors.forename: Frédéric
authors.initials: F
authors.lastname: Ariey
authors.forename: Chansuda
authors.initials: C
authors.lastname: Wongsrichanalai
mesh_terms: D000328:Adult; D000818:Animals; D000962:Antimalarials / Q000008:administration & dosage / Q000627:therapeutic use*; D037621:Artemisinins / Q000008:administration & dosage / Q000627:therapeutic use*; D000077332:Artesunate; D002160:Cambodia; D002648:Child; D002738:Chloroquine / Q000008:administration & dosage / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D020128:Inhibitory Concentration 50; D016778:Malaria, Falciparum / Q000188:drug therapy*; D016780:Malaria, Vivax / Q000188:drug therapy; D008297:Male; D015767:Mefloquine / Q000008:administration & dosage / Q000627:therapeutic use*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D018512:Parasitemia; D010963:Plasmodium falciparum / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D016133:Polymerase Chain Reaction / Q000379:methods; D016019:Survival Analysis; D017211:Treatment Failure
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D000077332:Artesunate; D002738:Chloroquine; D015767:Mefloquine; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C513498:Mdr1 protein, Plasmodium falciparum