Rithea LeangWalter R.J. TaylorDenis Mey BouthLijiang SongJoel TarningMeng Chuor CharSaorin KimBenoit WitkowskiValentine DuruAnais DomergueNimol KhimPascal RingwaldDidier MenardNational Centre for Parasitology, Entomology and Malaria ControlHopitaux universitaires de GeneveOrganisation Mondiale de la SanteMahidol UniversityUniversity of OxfordInstitut Pasteur du Cambodge2018-11-232018-11-232015-08-01Antimicrobial Agents and Chemotherapy. Vol.59, No.8 (2015), 4719-472610986596006648042-s2.0-84939832774https://repository.li.mahidol.ac.th/handle/20.500.14594/36367Copyright © 2015, American Society for Microbiology. All Rights Reserved. Western Cambodia is recognized as the epicenter of Plasmodium falciparum multidrug resistance. Recent reports of the efficacy of dihydroartemisinin (DHA)-piperaquine (PP), the latest of the artemisinin-based combination therapies (ACTs) recommended by the WHO, have prompted further investigations. The clinical efficacy of dihydroartemisinin-piperaquine in uncomplicated falciparum malaria was assessed in western and eastern Cambodia over 42 days. Day 7 plasma piperaquine concentrations were measured and day 0 isolates tested for in vitro susceptibilities to piperaquine and mefloquine, polymorphisms in the K13 gene, and the copy number of the Pfmdr-1 gene. A total of 425 patients were recruited in 2011 to 2013. The proportion of patients with recrudescent infections was significantly higher in western (15.4%) than in eastern (2.5%) Cambodia (P <10-3). Day 7 plasma PP concentrations and median 50% inhibitory concentrations (IC50) of PP were independent of treatment outcomes, in contrast to median mefloquine IC50, which were found to be lower for isolates from patients with recrudescent infections (18.7 versus 39.7 nM; P = 0.005). The most significant risk factor associated with DHA-PP treatment failure was infection by parasites carrying the K13 mutant allele (odds ratio [OR], 17.5; 95% confidence interval [CI], 1 to 308; P = 0.04). Our data show evidence of P. falciparum resistance to PP in western Cambodia, an area of widespread artemisinin resistance. New therapeutic strategies, such as the use of triple ACTs, are urgently needed and must be tested. (This study has been registered at the Australian New Zealand Clinical Trials Registry under registration no. ACTRN12614000344695.)Mahidol UniversityMedicineArticleSCOPUS10.1128/AAC.00835-15