PDE6A and malaria: Another sub-micromolar inhibitor of malaria parasite PDEs, BIPPO, derived from a human PDE9 series, has an EC50 of 0.4 μM against P. falciparum proliferation and an IC50 of 150 nM against recombinant PDEα, but still retains an IC50 of 30 nM against human PDE9.