"Clobbering parasites at two places is greater insurance that you clean them out."
A chemical ranked with the second-string players in the world's continuing contest with malaria has reappeared as a new drug, apparently capable of preventing the disease. Paired with an older, standard drug, it provides protection with an unusually small risk of drug resistance.
In a study in the September American Journal of Tropical Medicine and Hygiene, researchers at Johns Hopkins describe how the drug atovaquone was 100 percent effective in keeping volunteers bitten by mosquitoes carrying Plasmodium falciparum, the parasite responsible for fatal forms of malaria, from developing the disease.
"Atovaquone attacks the parasite at a different point in its life cycle from other drugs -- one that reaches the parasite sooner," says Theresa A. Shapiro, M.D., Ph.D., the clinical pharmacologist who led the Hopkins team. Further, pairing atovaquone with proguanil, an older malaria-fighting drug, "should greatly raise our chances of preventing malaria while avoiding the drug resistance that now plagues its treatment. Clobbering parasites at two places," Shapiro says, "is greater insurance that you clean them out."
Drug resistance occurs when a few parasites in their human hosts manage to survive therapy. The parasites then prosper and dominate as causes of disease. Malaria researchers report that drug-resistant forms of the parasite infest 80 percent of countries with the disease.
Atovaquone's different approach may skirt another stumbling block in malaria prevention: keeping patients on the drugs. With current preventives, travelers must take them weeks after a visit to a malaria-carrying country. "With atovaquone, travelers should be able to take their last dose as they leave," says Shapiro.
In the study, 12 volunteers were started on atovaquone -- at either a
high or a low dose -- while
Contact: Marjorie Centofanti
Johns Hopkins Medical Institutions