Purfalcamine

Purfalcamine is an orally active, selective Plasmodium falciparum calcium-dependent protein kinase 1 (PfCDPK1) inhibitor with an IC50 of 17 nM and an EC50 of 230 nM. Purfalcamine has antimalarial activity and causes malaria parasites developmental arrest at the schizont stage[1][2].

Purfalcamine has low activity against Toxoplasma gondii calcium-dependent protein kinase 3 (TgCDPK3)[1]. Purfalcamine (225, 450 nM) has no effect on the parasitemia in the first 32 hours. After about 40 hours, parasite level remains stable and then begins dropping[1]. Purfalcamine inhibits proliferation with EC50s of 171-259 nM for P. falciparum strains (3D7, Dd2, FCB, HB3 and W2), which indicates effectiveness against drug-resistant parasites[1]. Given that the EC50 value for P. falciparum (3D7) is 230 nM, Purfalcamine shows a therapeutic window ranging from 23-fold to 36-fold (EC50s for CHO=12.33 μM, HEp2=7.235 μM, HeLa=7.029 μM and Huh7=5.476 μM)[1].

Purfalcamine (10 mg/kg; oral gavage; BID; for 6 days) demonstrates a delay in the onset of parasitemia in treated mice[1]. Purfalcamine (20 mg/kg; orally gavage) exhibits a Cmax of 2.6 μM with a half-life of 3.1 hours[1]. Animal Model: Male BALB/c mice, 7 weeks of age with the malaria parasite[1]

[1]. Nobutaka Kato, et al. Gene expression signatures and small-molecule compounds link a protein kinase to Plasmodium falciparum motility. Nat Chem Biol. 2008 Jun;4(6):347-56. [2]. Rajshekhar Y Gaji, et al. Expression of the essential Kinase PfCDPK1 from Plasmodium falciparum in Toxoplasma gondii facilitates the discovery of novel antimalarial drugs. Antimicrob Agents Chemother. 2014 May;58(5):2598-607.