Table 2.

Susceptibility of P. knowlesi and P. falciparum to three DHODH inhibitors assessed using the SYBR Green I assay

DHODH inhibitor	EC50 (nM), single life cycle			EC50 (nM), two life cycles
	P. knowlesi, 27 h	P. falciparum, 48 h	fold difference	P. knowlesi, 54 h	P. falciparum, 96 h	fold difference
DSM1	509 ± 11	149 ± 5	3.4	417 ± 2	91 ± 10	4.6
DSM265	303 ± 15	37 ± 3	8.2	186 ± 11	21 ± 1	8.9
DSM421	194 ± 23	72 ± 5	2.7	123 ± 10	42 ± 4	2.9

All inhibitors were tested in duplicate on three separate occasions from a starting parasitaemia and haematocrit of 1%. The EC₅₀ values are reported as the mean ± SEM. The fold difference is calculated by dividing the P. knowlesi EC₅₀ value by the P. falciparum EC₅₀ value. For each DSM compound, the mean P. falciparum EC₅₀ value was significantly lower than the mean P. knowlesi EC₅₀ value when compared over either a single parasite life cycle or over two life cycles (P ≤ 0.0018).