Figure 3

In vitro resistance selection assessment. (a) A standard in vitro protocol for resistance selection frequency measurement uses defined starting inocula of a P. falciparum strain pressured with a constant level of drug nearing the IC₉₀. Parasitemia falls below detection limits but eventual resistant parasites are able to recrudesce and to be cloned for subsequent determination of the IC₅₀ fold increase. The minimal inoculum for resistance (MIR) is a measure of the resistance selection frequency, while the IC₅₀ fold increase measures the level of resistance. (b) These two endpoints are used to classify anti-malarial compounds according to risk levels (see main text). It is advisable to run control experiments in parallel with compounds known to select resistance readily, such as atovaquone.