Tafenoquine, a new drug to prevent relapse of vivax malaria

A new drug, tafenoquine was approved this year by US FDA as a single-dose treatment to prevent relapse (radical cure) of Plasmodium vivax malaria.

Tafenoquine is a new 8-aminoquinoline antimalarial drug. It is a synthetic analog of primaquine with an elimination half-life of 15 days. It acts on all stages of malaria (Antimicrob Agents Chemother. 2007 Aug;51(8):2709-15), including the quiescent liver stage, the hypnozoite. Hence, it is used for the radical cure or prevention of relapse of Plasmodium vivax infections.

The effectiveness of tafenoquine as an anti-relapse agent has been demonstrated in two studies published in the New England Journal of Medicine this year.

In a trial conducted in Ethiopia, Peru, Brazil, Cambodia, Thailand and the Philippines, single-dose tafenoquine significantly reduced the risk of P. vivax recurrence in patients with phenotypically normal G6PD activity. The percentage of patients who were free from recurrence at 6 months was 62.4% in the tafenoquine group, 27.7% in the placebo group and 69.6% in the primaquine group (N Engl J Med. 2019 Jan 17;380(3):215-22).

 In another trial of patients with confirmed P. vivax parasitemia, which compared compared tafenoquine with primaquine, tafenoquine (single 300 mg dose) was shown to be not inferior to primaquine (15 mg once daily x 14 days). In the patient-level meta-analysis, the percentage of patients who were free from recurrence at 6 months was 67.0% in the tafenoquine-treated group and 72.8% in the primaquine-treated group. Among patients with normal G6PD enzyme activity, the decline in hemoglobin level with tafenoquine was not significantly different from that with primaquine. (N Engl J Med. 2019 Jan 17;380(3):229-241).

These trials show tafenoquine as an effective and convenient alternative to primaquine as anti-relapse therapy for adult patient with P. vivax infection. A word of caution, the patient must be tested for G6PD deficiency as tafenoquine can cause hemolysis in individuals with G6PD enzyme activity less than 70%.

                  

Dr KK Aggarwal

Padma Shri Awardee

President Elect Confederation of Medical Associations in Asia and Oceania   (CMAAO)

Group Editor-in-Chief IJCP Publications

President Heart Care Foundation of India

Past National President IMA