Tafenoquine - a potential medicine to prevent P. vivax relapse

Dr Justin Green, Director, Clinical Development, GlaxoSmithKline

Tafenoquine is an investigational medicine that has completed phase III studies. If approved, it would be the first new medicine for relapsing malaria in over 60 years. Tafenoquine will potentially offer a single-dose cure for the liver-stage of P. vivax infections and will be administered alongside a standard 3-day chloroquine or potentially an ACT treatment regimen. 

Tafenoquine is a member of the same chemical family as primaquine; both are associated with a risk of haemolytic side-effects in a subset of patients lacking adequate levels of the enzyme glucose-6-phosphate dehydrogenase (G6PD) (on average 8% of people in malaria-endemic countries).1 To reduce the risk of haemolysis, GSK is working with PATH on the development of a quantitative G6PD point-of-care diagnostic test so that patients’ G6PD status can be tested to determine if tafenoquine or primaquine can be safely administered. The goal is for this field-ready diagnostic test to be available at the same time as the potential launch of tafenoquine in malaria-endemic countries.

Dr Justin Green leads the clinical and paediatric teams responsible for the development of tafenoquine. He explains how the work is gathering pace.

1. How is the phase III programme progressing?

We have just completed the two studies, DETECTIVE and GATHER, which respectively looked at efficacy and safety. We plan to present the headline results in June 2017 at the 6th International Conference on Plasmodium vivax Research in Manaus, Brazil.

2. Why is a paediatric formulation of tafenoquine so important?

From our perspective, an adult indication is only part of the package. Without a paediatric formulation, I think it's going to be incredibly challenging for malaria control programmes to have a real impact, particularly in areas of Peru and Brazil, where a lot of children are suffering from relapsing malaria. Thankfully, there is less mortality from P. vivax in children, but morbidity can be high. Persistent infections combined with a poor diet and anaemia lead to children regularly missing school, which in turn results in diminished educational attainment and an additional burden of care on families.

3. How is the development of tafenoquine paediatric progressing?

We recruited the first patient into the TEACH paediatric phase IIb study in early 2017, which was an incredibly exciting milestone for the project. To date, we have recruited the first cohort of 16 patients and recruitment for the second cohort will begin towards the end of 2017.

4. As a pharmaceutical company, how does GSK benefit from collaborating with MMV?

Collaboration is key in our efforts to tackle malaria, with each organization bringing different expertise and perspectives. The support and advice we receive from the MMV team and ESAC, as well as access to MMV’s network, is key to the success of the tafenoquine project, particularly given the global nature of the challenge of P. vivax malaria. The expertise that MMV has provided, including the routine checkpoints from ESAC and through the integration of MMV staff into GSK’s core teams, has helped guide the study design and interpretation of data. Such collaborations help advance our research and increase our understanding of new areas of science, while sharing the risks of development.

  1. Howes RE et al. “G6PD deficiency prevalence and estimates of affected populations in malaria endemic countries: a geostatistical modelbased map.” PLoS Med. 9(11):e1001339 (2012).