This article is inter alia a brief, first-stop guide to possible adverse events (AEs) associated with tafenoquine (TQ) intake. Safety and efficacy findings for TQ in Plasmodium vivax malaria prophylaxis and radical cure are summarized and some of the latest TQ-related studies (published in 2020 and 2021) are highlighted.
In this issue of the Journal of Travel Medicine, Islam et al.1 examine what the US Army developers of tafenoquine envisioned as its most useful application—a single dose providing sustained protection from malaria. Informally, they referred to that vision as ‘fire-and-forget’ chemoprophylaxis. The relatively prolonged elimination half-life of tafenoquine (about 18 days) was selected from among competing preclinical 8-aminoquinolines for this purpose.
Plasmodium vivax is the most widespread human malaria parasite, with 2.5 billion people at risk of infection worlwide. P. vivax forms liver hypnozoites which trigger further symptomatic episodes (relapses) weeks or months after the initial episode. Radical cure of vivax malaria requires hypnozoitocide therapy to prevent relapses. The two FDA-approved hypnozoiticides for human use, primaquine and tafenoquine, are pro-drugs, that require in vivo conversion into metabolites with redox activity. This mini-review focuses on the association between CYP2D6-mediated hydroxylation and hypnozoiticide efficacy of primaquine and tafenoquine.
Due to drug resistance, commonly used anti-Babesia drugs have limited efficacy against babesiosis, and inflict severe side effects. Tafenoquine (TAF) was approved by the U.S. Food and Drug Administration in 2018 for the radical cure of Plasmodium vivax infection and for malaria prophylaxis. Here, we evaluated the efficacy of TAF for the treatment of Babesia infection and elucidated the suspected mechanisms of TAF activity against Babesia parasites. Parasitemia and survival rates of B. rodhaini-infected BALB/c and SCID mice were used to explore the role of the immune response in Babesia infection after TAF treatment.
Accurate measurement of glucose-6-phosphate dehydrogenase (G6PD) activity is critical for malaria treatment as misclassification of G6PD deficiency could cause serious harm to patients. G6PD activity should be assessed in blood samples on the day of collection. Otherwise, specimens should be stored under suitable conditions to prevent loss of G6PD activity.
Despite recent intensification of control measures, Plasmodium vivax poses a major challenge for malaria elimination efforts. Liver-stage hypnozoite parasites that cause relapsing infections can be cleared with primaquine; however, poor treatment adherence undermines drug effectiveness. Tafenoquine, a new single-dose treatment, offers an alternative option for preventing relapses and reducing transmission. In 2018, over 237,000 cases of malaria were reported to the Brazilian health system, of which 91.5% were due to P. vivax.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common enzymopathy in humans, is prevalent in tropical and subtropical areas where malaria is endemic. Anti-malarial drugs, such as primaquine and tafenoquine, can cause haemolysis in G6PD-deficient individuals. Hence, G6PD testing is recommended before radical treatment against vivax malaria. Phenotypic assays have been widely used for screening G6PD deficiency, but in heterozygous females, the random lyonization causes difficulty in interpreting the results. Over 200 G6PD variants have been identified, which form genotypes associated with differences in the degree of G6PD deficiency and vulnerability to haemolysis. This study aimed to assess the frequency of G6PD mutations using a newly developed molecular genotyping test.
Chemoprophylaxis with weekly doses of tafenoquine (200 mg/day for 3 days before departure [loading dose], 200 mg/week during travel and one-week post-travel [maintenance doses]) is effective in preventing malaria. Effectiveness of malaria chemoprophylaxis drugs in travellers is often compromised by poor compliance. Shorter schedules that can be completed before travel, allowing ‘drug-free holidays’, could increase compliance and thus reduce travel-related malaria. In this meta-analysis, we examined if a loading dose of tafenoquine alone is effective in preventing malaria in short-term travellers.
A century long history in 8-aminoquinolines, the only anti-malaria drug class preventing malaria relapse, has resulted in the approval of tafenoquine by the U.S. Food and Drug Administration (FDA) and the Australian Therapeutic Goods Administration (TGA) and to date registration in Brazil and Thailand. Tafenoquine is an alternative anti-relapse treatment for vivax malaria and malaria prophylaxis. It should not be given in pregnancy, during lactation of infants with glucose-6-phosphate dehydrogenase (G6PD) unknown or deficient status, and in those with G6PD deficiency or psychiatric illness.
In 2018, tafenoquine was approved for malaria chemoprophylaxis. We evaluated all available data on the safety and efficacy of tafenoquine chemoprophylaxis.