Influence of the Gene on In Vitro Sensitivities of Piperaquine in Thai Isolates of .

Piperaquine combined with dihydroartemisinin is one of the artemisinin derivative combination therapies, which can replace artesunate-mefloquine in treating uncomplicated falciparum malaria in Thailand. The aim of this study was to determine the in vitro sensitivity of Thai isolates against piperaquine and the influence of the gene on in vitro response. One hundred and thirty-seven standard laboratory and adapted Thai isolates of were assessed for in vitro piperaquine sensitivity. Polymorphisms of the gene were determined by polymerase chain reaction methods. The mean and standard deviation of the piperaquine IC in Thai isolates of were 16.7 ± 6.3 nM. The parasites exhibiting chloroquine IC of ≥ 100 nM were significantly less sensitive to piperaquine compared with the parasite with chloroquine IC of < 100 nM. No significant association between the copy number and piperaquine IC values was found. In contrast, the parasites containing the 86Y allele exhibited significantly reduced piperaquine sensitivity. Before nationwide implementation of dihydroartemisinin-piperaquine as the first-line treatment in Thailand, in vitro and in vivo evaluations of this combination should be performed especially in areas where parasites containing the 86Y allele are predominant such as the Thai-Malaysian border.