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Single-dose malaria drug eliminates parasite from liver

Tafenoquine signifies 'one of the most significant advances in malaria treatment in the past 60 years'

Louise Prime

Monday, 23 July 2018

A first-in-class drug that eliminates the malaria parasite Plasmodium vivax (P.vivax) from the liver in a single dose has been approved by the US Food and Drug Administration (FDA). Malaria experts have hailed the approval of tafenoquine (Krintafel) as “one of the most significant advances in malaria treatment in the past 60 years”.

The dormant liver stage of P. vivax infection causes malaria relapses, without the need for another infected mosquito bite. The FDA pointed out that until now, primaquine has been the only medicine to inactivate this dormant liver stage and prevent relapse – but the 14-day treatment and compliance with primaquine, which has just a six-hour half-life, can be difficult.

Tafenoquine, whose half-life in contrast is 15 days, is given to adults with P. vivax infection as a single 300mg dose, in addition to the appropriate antimalarial therapy (e.g. chloroquine).

In the approval documentation, the FDA noted that 13 studies support the “radical cure indication” for tafenoquine, which has high rates of compliance and a similar safety profile to that of primaquine. The FDA described tafenoquine as the “first new treatment for prevention of relapse in more than 60 years”.

Professor Ric Price, of the University of Oxford’s Nuffield Department of Medicine, was involved in genetics research* published two years ago that showed how P. vivax is evolving rapidly to adapt to conditions in different geographical locations, in particular to defend itself against widely-used antimalarial drugs.

He commented to the BBC this morning: “The ability to get rid of the parasite in the liver with a single dose of tafenoquine is a phenomenal achievement and in my mind it represents one of the most significant advances in malaria treatment in the last 60 years.”

However, because of the risk of haemolytic anaemia, the drug is contraindicated in people with glucose-6-phosphate dehydrogenase (G6PD) deficiency or unknown G6PD status; and in breastfeeding by a lactating woman whose baby is found to be G6PD deficient or if G6PD status is unknown. The approved drug label points out that all patients must be tested for G6PD deficiency prior to prescribing tafenoquine, and pregnancy testing is recommended before females of reproductive potential start treatment; it adds that patients should be monitored patients for clinical signs or symptoms of haemolysis.

*Pearson RD, Amato R, Kwiatkowski DP, et al. Genomic analysis of local variation and recent evolution in Plasmodium vivax. Nature Genetics volume 48, pages 959–964 (2016)

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