Stealthy enemy. vivax malaria, shown here in the bloodstream, can hide-undetectable in liver cells.
CDC
The first new drug in half a century to target malaria parasites in one of their best hiding showing encouraging results. Researchers in drug development, called tafenoquine, said today that data from a recently completed phase II trial were promising enough that they will soon begin a III-final stage Phase before seeking drug regulatory approval.
tafenoquine kills the malaria parasite when it hides in the liver cells, in a form called hypnozoite, or "dormant parasite." hypnozoites not cause any symptoms and are impossible to detect by blood tests. But when it is triggered by signals that are not fully understood, they can reactivate to cause another bout of malaria, which can then be picked up by mosquitoes and transmitted to new victims. Five species of Plasmodium can cause malaria in humans. Two of them- Plasmodium vivax , which is widespread, and relatively rare P -Can hypnozoites oval shape. This ability to hide is one of the things that makes P. vivax so hard to eliminate a region.
Now, the only treatment that can cure malaria parasites hiding vivax and everything is within 14 days of a drug called primaquine, which was developed in the 1940s works well enough, but it is difficult for people who do not feel ill to complete 2 full weeks. "Compliance with the current regime is really a problem," said JP Kleim, director of clinical development for the pharmaceutical company GlaxoSmithKline (GSK). "The acute malaria disappeared after a few days [of treatment]," so motivation patients continue to take medication is low. that is why GSK has decided to develop tafenoquine and the medicines for Malaria Venture, a nonprofit based in Geneva. the partners launched a lawsuit in 2011 to test whether a single dose of tafenoquine might work as well as the 2-week course of primaquine.
the data, presented today at the American Society of Tropical Medicine and Hygiene annual Meeting in Washington, DC, suggest that a single dose works fine. the trial involved 329 patients in Brazil, India, Thailand and Peru. in patients who received either 300 mg or 0 mg dose of the drug, 0% had no relapses after 4 month. The partners will now move forward with a Phase III trial testing the safety and efficacy of 300 mg in 0 patients, said Marcus Lacerda of Fundação de Medicina Tropical Dr. Heitor Vieira Dourado in Manaus, Brazil, who helped coordinate the study and presented the results at the meeting today.
a single-dose drug would be a huge advantage in the fight against vivax malaria, said Ric Price from the Menzies School of Health Research in Darwin, Australia, and the University of Oxford UK. "One of the biggest challenges we face is how do we deal adequately and reliably hypnozoite stage."
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