WHO and national treatment guidelines recommend treating both the blood- and liver-stage of P. vivax malaria. However, physicians do not always prescribe primaquine, the only medicine currently available for the treatment of liver-stage infections. Several factors contribute to the low use of primaquine, including: concerns about possible haemolysis in G6PD1-deficient patients, limited access to G6PD tests, and poor compliance with the 14-day course of treatment.
MMV is working with GSK on the development of tafenoquine as a single-dose treatment for the radical cure of liver-stage infections. While tafenoquine shares similar limitations with primaquine regarding use in G6PD-deficient patients, its simplified dosing regimen and single dose (instead of 14 days of primaquine) should improve real-life treatment compliance and drug effectiveness.
The phase III clinical trials of tafenoquine have been completed; top line results were presented at the 6th International Conference on Plasmodium vivax Research in Manaus, Brazil on 12 June 2017, and demonstrated clear superiority of single-dose tafenoquine plus 3-days of chloroquine compared to P. vivax treatment with 3-days of chloroquine alone. The regulatory dossier for tafenoquine was submitted to the US FDA and separately to the Australian TGA in Q4 2017.
Recruitment for the first cohort of a paediatric PK bridging study is complete and the analysis of the data is complete; recruitment of the second cohort started in January 2018.
In parallel, PATH is working with industry partners to develop a point-of-care G6PD test to ensure that only patients with adequate level of G6PD enzymatic activity will receive tafenoquine.