Papua New Guinea Institute of Medical Research

In Papua New Guinea, administration of primaquine (PQ) or tafenoquine (TQ) to breastfeeding mothers is contraindicated during the first six months postpartum, when infants are recommended to be exclusively breastfed, because of a lack of comprehensive pharmacokinetic data on PQ/TQ neonatal and infant exposure via breast milk. The therapeutic restriction of PQ/TQ use in lactating women during the first six months postpartum effectively translates into
10% of females being excluded from radical cure in endemic areas at any time. This is because many at risk women live in remote areas, are frequently lost to follow-up, or may have conceived again before they reattend. As a result, radical cure is rarely achieved and women are exposed to recurrent infections and cumulative risk of anaemia. Relapses may occur for years, placing subsequent pregnancies at risk and perpetuating intergenerational failure of fetal growth. They also contribute to malaria transmission, thus household and community exposure to vivax malaria.
The goal of the present study is to determine how much PQ/TQ is transferred to a suckling baby, if a mother receives a treatment course of PQ/TQ at time of delivery. We also want to confirm that this treatment is safe and has no major side effects for babies in Papua New Guinea.
The study Interventions areas follows: Group 1 - Participants receive PNG standard of care; PQ given 6-months postpartum; Group 2 - Participants receive a 14-day treatment regimen of PQ, at the standard dose prescribed in PNG for vivax radical cure (0.5 mg/kg/day for 14 days); Group 3 - Participants receive an accelerated high-dose 7-day treatment regimen of PQ, as per current WHO recommendations (1.0 mg/kg/day for 7 days); Group 4 - Participants receive a single dose of 300mg tafenoquine.
All participants will be monitored for a total duration of 6 months, with the safety, tolerability, pharmacokinetics and preliminary relapse efficacy of PQ/TQ evaluated at standardised time points over this period (Day 0, 1, 3, 6, 8, 15, 20, 28, and Month 2, 3, 4, 5 and 6). At each of these time points, participants will be asked to describe any symptoms they may be experiencing, participate in a medical examination, and provide a blood and breast milk sample for drug analysis and safety (biochemistry and haematology testing). The investigators will also collect a small blood sample (heel prick) from the infant to measure drug concentrations and safety testing.

Plasmodium vivax is the most geographically widespread malaria species and the second largest contributor to symptomatic malaria worldwide. It accounts for half of all malaria cases outside Africa, with an estimated 14.3 million clinical vivax malaria cases reported annually, contributing to an annual cost of US$359 million. Children are most vulnerable to infection, with P. vivax prevalence peaking between 2 to 6 years of age. In Papua New Guinea (PNG), there are >1.5 million suspected P. vivax cases annually, and while P. falciparum infections are the most prevalent, P. vivax transmission is the most intense in the world. P. vivax in PNG provides a unique epidemiological setting in which to assess innovative treatments in children.
The complex biology of P. vivax represents a challenge for malaria control and chemotherapy, especially dormant liver-stage parasites (hypnozoites) which can reactivate (relapse) and cause disease at a time remote from the primary infection. Hypnozoite relapse is the primary cause of vivax malaria in endemic regions and is resistant to most antimalarial drugs. Identifying effective treatments for radical cure, the complete elimination of parasites (both blood- and liver-stage), is therefore a priority. The World Health Organization (WHO) recommends a 14-day radical cure regimen for uncomplicated vivax malaria; comprised of blood stage treatment (chloroquine or artemisinin combination therapy (ACT)) and 14 days of the 8-aminoquinoline drug primaquine (PQ; 0.25-0.5 mg/kg/day) for liver-stage cure. More recently, the 8-aminoquinoline tafenoquine has garnered interest as an alternative radical cure agent to primaquine. However, there is limited data on the pharmacokinetics, tolerability and radical cure efficacy of tafenoquine in children.
The overall aim of the study is to characterise the pharmacokinetic profile of tafenoquine (and primary metabolite) in Papua New Guinean children.

The goal of this clinical trial is to assess the efficacy and safety or a revised weight band tafenoquine dose in vivax malaria patients. The main question[s] it aims to answer are:
* is a revised weight-based TQ regimen (TQRevised: target dose 7.5mg/kg) non-inferior to high dose primaquine (7mg/kg over 7 days)
* is a revised weight-based TQ regimen (TQRevised: target dose 7.5mg/kg) superior to fixed dose tafenoquine (300mg)
* is the tolerability and safety of TQRevised acceptable
* is TQRevised acceptable and feasible Participants will receive a tafenoquine target dose 7.5mg/kg in weight bands. Researchers will compare this to patients receiving a fixed dose tafenoquine and high dose primaquine to see if safe and effective.