Lacerda MVG, et al. - Investigators assessed subjects with Plasmodium vivax infection and estimated that single dose of tafenoquine produced a significantly lower risk of P. vivax recurrence (a treatment termed “radical cure”) than placebo in subjects with phenotypically normal glucose-6-phosphate dehydrogenase (G6PD) activity as it caused the clearing of dormant hypnozoites from the liver.

Methods

• In Ethiopia, Peru, Brazil, Cambodia, Thailand, and the Philippines, this multicenter, double-blind, double-dummy, parallel group, randomized, placebo-controlled trial was conducted.
• A sum of 522 subjects with microscopically confirmed P. vivax infection (>100 to <100,000 parasites per microliter) and normal G6PD activity (with normal activity defined as ≥70% of the median value determined at each trial site among 36 healthy male volunteers who were otherwise not involved in the trial) were involved.
• All candidates were given a 3-day course of chloroquine (total dose of 1500 mg).
• Additionally, subjects were categorized to receive a single 300-mg dose of tafenoquine on day 1 or 2 (260 patients), placebo (133 patients), or a 15-mg dose of primaquine once daily for 14 days (129 patients).
• The primary consequence was the Kaplan–Meier estimated percentage of individuals free from recurrence at 6 months (defined as P. vivax clearance without recurrent parasitemia).

Results

• They observed 62.4% of candidates in the tafenoquine group (95% confidence interval [CI], 54.9 to 69.0), 27.7% in the placebo group (95% CI, 19.6 to 36.6), and 69.6% in the primaquine group (95% CI, 60.2 to 77.1) free from recurrence at 6 months in the intention-to-treat population.
• They noted a hazard ratio of 0.30 (95% CI, 0.22 to 0.40) with tafenoquine in comparison to placebo (P < 0.001) and 0.26 (95% CI, 0.18 to 0.39) with primaquine as compared with placebo (P < 0.001) for the risk of recurrence.
• They also noticed asymptomatic reduction in hemoglobin levels with the use of tafenoquine which resolved without intervention.