Table 3. In vitro antimalarial activity of zaprinast.

Asynchronous P. falciparum Honduras-1 were cultured with final Ht 3% and 0.3% parasitaemia in the absence or presence of PDE inhibitors. After 72 h, more than 1000 erythrocytes stained with Giemsa were examined under microscopy. The ED₅₀ value, which is a dose giving 50% reduction of the increase of infected erythrocytes, was determined by comparison to drug-free controls cultured under the same conditions. Data are expressed as the means±S.E.M. for three independent determinations.

Inhibitors	ED50 (μM)
IBMX	>100
Theophylline	>100
Zaprinast	35±4.2