 Compulsory commencement of treatment with Riamet artemether-lumefantrine will occur on study day 16 3 days post OZ439 and DSM265 treatment unless required earlier. Early standard anti-malarial drug intervention can occur if either poor responses or fast responses are seen following OZ439 and DSM265 treatment. This is to ensure participant safety and to avoid participant inconvenience if useful data cannot be obtained. A poor response is defined as a decrease in parasitaemia of less than 20 from baseline by 3 days post OZ439 and DSM265 treatment. A fast response occurs when, within the seven day period following the treatment, two consecutive PCR assessments in 48 hours are negative. However, pre-emptive treatment with Riamet can commence whenever deemed necessary by the investigator. Participants will be monitored, either in clinic, or by telephone for three days to ensure adherence to Riamet therapy. 