Kittiya MahotornPeerapan Tan-AriyaThunyapit ThitaToon Ruang-AreerateNaruemon SittichotNantana SuwandittakulMathirut MungthinMahidol UniversityPhramongkutklao College of Medicine2019-08-232019-08-232018-01-01American Journal of Tropical Medicine and Hygiene. Vol.98, No.1 (2018), 51-56000296372-s2.0-85040519450https://repository.li.mahidol.ac.th/handle/20.500.14594/46062© 2018 by The American Society of Tropical Medicine and Hygiene. Pyronaridine, a Mannich base antimalarial agent with a high activity against chloroquine-resistant Plasmodium falciparum, has been combined with artesunate as a new artemisinin based combination therapy (ACT). Pyronaridine-artesunate combination could be one of the choices for the treatment of uncomplicated falciparum malaria in multidrug-resistant areas including Thailand. The aim of this study was to determine in vitro sensitivity and crossresistance pattern of pyronaridine in Thai isolates of P. falciparum. In addition, the influence of resistant genes concerning in vitro pyronaridine sensitivity was determined. The mean pyronaridine 50% inhibitory concentration (IC50) of 118 parasite isolates was 5.6±3.1 nM (range = 0.2-15.4 nM) with a significant positive correlation with artesunate IC50 (r = 0.246, P = 0.008) and amodiaquine IC50 (r = 0.220, P = 0.042) and a significant negative correlation with quinine IC50 (r =-0.185, P = 0.047). Parasites containing the pfmdr1 86Y allele exhibited significantly reduced pyronaridine sensitivity compared with those with the pfmdr1 N86 allele (7.6±3.3nMand 5.4±3.0 nM, respectively,P= 0.032, independent t test); however, the difference may not be clinically relevant. Pyronaridine-artesunate could be the candidate ACT to treat multidrug-resistant falciparum malaria in Thailand with careful monitoring.Mahidol UniversityImmunology and MicrobiologyMedicineArticleSCOPUS10.4269/ajtmh.17-0286