Pharmacokinetic and in Vitro Transmission Blocking Activities Study of Primaquine Compare to Methylene Blue in Healthy Volunteer Both G6PD Normal and G6PD Deficiency

• Status: Completed
• Trial end date: 2014-10-01

Summary

The emergence of partial artemisinin resistance in Plasmodium falciparum on the Cambodia-Thai border and more recently on the Myanmar-Thai border jeopardizes the renewed global efforts of control and elimination of malaria. Containment of this severe threat requires reduction of transmission of the resistant phenotype by adding gametocytocidal drugs to the treatment of falciparum malaria. Mathematical models also predict that transmission blocking will be required if the goal of malaria elimination is to be achieved. The only drug currently available with strong gametocytocidal properties against the more mature gametocytes is primaquine. However, the oxidative properties of primaquine readily causes acute haemolysis in glucose 6 phosphate dehydrogenase (G6PD) deficiency, the degree of which appears to be inversely related to G6PD enzyme activity. Because of these safety concerns, primaquine is not widely deployed in treatment regimens for falciparum malaria, even in areas with documented artemisinin resistance. Methylene blue, which does not exert its action through an oxidative mechanism, is a promising alternative as a gametocytocidal adjuvant to artemisinin combination therapies (ACTs). Paul Ehrlich discovered methylene blue as the first synthetic drug ever to treat malaria. In contrast with primaquine, the thiazine dye methylene blue asserts its properties as an oxidizing agent only at very high doses, whereas at pharmacologic doses it has reducing agent properties and is for this reason used as a medication for the treatment of methemoglobinemia. A recent laboratory study identified methylene blue as a potent inhibitor of gametocyte development across all stages, almost fully abolishing P. falciparum transmission to mosquitoes at concentrations readily achievable in humans. In addition, a recent clinical study in 180 children with uncomplicated falciparum malaria in Burkina Faso showed that, compared to artesunate-amodiaquine alone, addition of the cheap drug methylene blue to either artesunate or amodiaquine importantly reduced gametocyte carrier rates measured at days 3, 7, and 14 of follow-up. This effect was seen both in patients with and without P. falciparum gametocytaemia at baseline. The current series of studies will investigate further methylene blue as a potential gametocytocidal drug in the treatment of uncomplicated falciparum malaria.

• Phase: Phase 1

Details

• Lead Sponsor: University of Oxford
• Treatments: Methylene Blue; Primaquine