GlaxoSmithKline (GSK) and Medicines for Malaria Venture (MMV) today announced positive results from two phase III studies of tafenoquine, an investigational 8-aminoquinoline, for the prevention of relapse of Plasmodium vivax (P.vivax) malaria.

Mature Plasmodium vivax schizont/CDC
Mature Plasmodium vivax schizont/CDC

The headline results, presented today at the International Conference on Plasmodium vivax Research (ICPVR) in Manaus, Brazil, show that a single-dose of 300mg tafenoquine, when given with a 3-day blood-stage chloroquine treatment, reduced the risk of relapse in patients with P.vivax malaria significantly more than placebo when given with chloroquine.

P. vivax is one of several species of Plasmodium parasite known to cause malaria. After an infected mosquito bite, the parasite has the ability to lie dormant in the liver and periodically reactivate causing relapses of P. vivax malaria. These relapses can occur weeks or even years after the initial infection. The disease is estimated to cause around 8.5 million clinical infections every year. Each of these infections keeps a child or adult from school or work for at least 3 days. Studies have shown that beyond lost time, malaria can also have adverse effects on cognitive ability.

Since 2008, GSK and MMV have been working together to develop single-dose tafenoquine as an alternative to the existing standard of care, primaquine, which must be taken for 14 days for patients with the relapsing form of malaria. The two phase III randomized, double-blind studies, “DETECTIVE” and “GATHER”, were conducted in malaria-endemic countries covering South America, Asia, and Africa.