Cyclosporin A (CsA) is an immunosuppressive drug widely used in organ transplants. It is also accumulated by the erythrocyte, a site that accommodates one of the stages of malaria parasite. We observe that CsA and its less potent immunosuppressive analogues CsC and CsD were as effective as chloroquine in inhibiting P. berghei malaria parasite development in vivo (when administered orally) and P. falciparum parasite in vitro. They were, however, not inhibitory to the liver stages and the gametocytes. In vivo the minimum effective dose was 10 mg/Kg administered on two consecutive days whereas, in vitro CsA and its analogues inhibited parasite development at concentrations of 10 micrograms/ml and above.
