Novel phenotypic resistance to artemisinin results in reduced exposure to drug at the most sensitive stage of intraerythrocytic development in Plasmodium falciparum

Materials and methods In this study we culture adapted and characterized a series of P. falciparum clones from Cambodia; these included parasites from cases with reduced parasite clearance rates in vivo. In vitro artemisinin resistance phenotypes were assessed by using T0 H-hypoxanthine assays, a novel parasite clearance assay, microscopy and flow cytometry to characterize intraerythrocytic development, and limiting dilution to assess parasite viability.