The activity of PS-15 in combination with sulfamethoxazole.

PS-15 is a novel biguanide folate antagonist that is metabolized in vivo to WR99210, a metabolite that is extremely active in vitro against multi-drug resistant strains of Plasmodium falciparum. When PS-15 was administered in combination with sulfamethoxazole to healthy Saimiri sciureus monkeys, the serum antimalarial activity was considerably greater than that observed in monkeys that received PS-15 alone. Further studies should be carried out to determine the value of PS-15/sulfonamide combinations in the treatment of human malaria infections and in preventing the emergence of drug-resistant parasites.