title: Dihydroartemisinin-piperaquine resistance in Plasmodium falciparum malaria in Cambodia: a multisite prospective cohort study.
abstract: BACKGROUND
  Artemisinin resistance in Plasmodium falciparum threatens to reduce the efficacy of artemisinin combination therapies (ACTs), thus compromising global efforts to eliminate malaria. Recent treatment failures with dihydroartemisinin-piperaquine, the current first-line ACT in Cambodia, suggest that piperaquine resistance may be emerging in this country. We explored the relation between artemisinin resistance and dihydroartemisinin-piperaquine failures, and sought to confirm the presence of piperaquine-resistant P falciparum infections in Cambodia.
  
  
  METHODS
  In this prospective cohort study, we enrolled patients aged 2-65 years with uncomplicated P falciparum malaria in three Cambodian provinces: Pursat, Preah Vihear, and Ratanakiri. Participants were given standard 3-day courses of dihydroartemisinin-piperaquine. Peripheral blood parasite densities were measured until parasites cleared and then weekly to 63 days. The primary outcome was recrudescent P falciparum parasitaemia within 63 days. We measured piperaquine plasma concentrations at baseline, 7 days, and day of recrudescence. We assessed phenotypic and genotypic markers of drug resistance in parasite isolates. The study is registered with ClinicalTrials.gov, number NCT01736319.
  
  
  RESULTS
  Between Sept 4, 2012, and Dec 31, 2013, we enrolled 241 participants. In Pursat, where artemisinin resistance is entrenched, 37 (46%) of 81 patients had parasite recrudescence. In Preah Vihear, where artemisinin resistance is emerging, ten (16%) of 63 patients had recrudescence and in Ratanakiri, where artemisinin resistance is rare, one (2%) of 60 patients did. Patients with recrudescent P falciparum infections were more likely to have detectable piperaquine plasma concentrations at baseline compared with non-recrudescent patients, but did not differ significantly in age, initial parasite density, or piperaquine plasma concentrations at 7 days. Recrudescent parasites had a higher prevalence of kelch13 mutations, higher piperaquine 50% inhibitory concentration (IC50) values, and lower mefloquine IC50 values; none had multiple pfmdr1 copies, a genetic marker of mefloquine resistance.
  
  
  CONCLUSIONS
  Dihydroartemisinin-piperaquine failures are caused by both artemisinin and piperaquine resistance, and commonly occur in places where dihydroartemisinin-piperaquine has been used in the private sector. In Cambodia, artesunate plus mefloquine may be a viable option to treat dihydroartemisinin-piperaquine failures, and a more effective first-line ACT in areas where dihydroartemisinin-piperaquine failures are common. The use of single low-dose primaquine to eliminate circulating gametocytes is needed in areas where artemisinin and ACT resistance is prevalent.
  
  
  BACKGROUND
  National Institute of Allergy and Infectious Diseases.
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA.
authors.forename: Chanaki
authors.initials: C
authors.lastname: Amaratunga
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA; National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Pharath
authors.initials: P
authors.lastname: Lim
authors.affiliation: National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Seila
authors.initials: S
authors.lastname: Suon
authors.affiliation: National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Sokunthea
authors.initials: S
authors.lastname: Sreng
authors.affiliation: Sampov Meas Referral Hospital, Pursat, Cambodia.
authors.forename: Sivanna
authors.initials: S
authors.lastname: Mao
authors.affiliation: Makara 16 Referral Hospital, Preah Vihear, Cambodia.
authors.forename: Chantha
authors.initials: C
authors.lastname: Sopha
authors.affiliation: Ratanakiri Referral Hospital, Ratanakiri, Cambodia.
authors.forename: Baramey
authors.initials: B
authors.lastname: Sam
authors.affiliation: National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Dalin
authors.initials: D
authors.lastname: Dek
authors.affiliation: National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Vorleak
authors.initials: V
authors.lastname: Try
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, UK; Medical Research Council Centre for Genomics and Global Health, University of Oxford, Oxford, UK.
authors.forename: Roberto
authors.initials: R
authors.lastname: Amato
authors.affiliation: Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK; Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Daniel
authors.initials: D
authors.lastname: Blessborn
authors.affiliation: Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK; Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Lijiang
authors.initials: L
authors.lastname: Song
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Tullo
authors.affiliation: Biostatistics Research Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Fay
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Anderson
authors.affiliation: Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK; Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Joel
authors.initials: J
authors.lastname: Tarning
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA. Electronic address: rfairhurst@niaid.nih.gov.
authors.forename: Rick M
authors.initials: RM
authors.lastname: Fairhurst
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000962:Antimalarials / Q000494:pharmacology*; D037621:Artemisinins / Q000008:administration & dosage / Q000494:pharmacology*; D002160:Cambodia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004351:Drug Resistance; D004359:Drug Therapy, Combination; D005260:Female; D005838:Genotype; D006801:Humans; D020128:Inhibitory Concentration 50; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology*; D008297:Male; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000187:drug effects*; D011446:Prospective Studies; D011804:Quinolines / Q000008:administration & dosage / Q000494:pharmacology*; D055815:Young Adult; D010879:Piperazines
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D011804:Quinolines; C039060:artenimol; C034759:piperaquine; D010879:Piperazines