DHA-PPQ vs CHQ With Tafenoquine for P. Vivax Mono-infection

Study Overview
=================
Brief Summary
-----------------
In this area of Greater Mekong Subregion (GMS), vivax malaria is the most common kind of malaria. It can stay very long in the liver, and come out later to make another episode of illness. This can happen many times even without a mosquito bite. Only 8-aminoquinoline drugs can kill the liver forms of the malaria parasite. One of these drugs is called primaquine, and it has been used all over the world for a long time. There is now a new formulation of this 8-aminoquinoline drug called tafenoquine that can also treat the malaria in the liver. The main benefit of this drug is that it is a single dose, which makes much convenient for the patients as well as for the malaria control program than conventional 14 days of primaquine. Recent research suggests that ACT (Artemisinin Combination Therapy) may antagonise the efficacy of tafenoquine (Baird et al. 2020) . This could prevent the use of tafenoquine in areas with chloroquine resistant P. vivax parasites where national malaria programmes recommend ACTs for vivax malaria. Also, currently recommended tafenoquine dose is sub-optimal: 300 mg dose proved significantly inferior to low dose primaquine in a meta-analysis of the phase 3 studies when restricted to the Southeast Asian region (Llanos-Cuentas et al. 2019; Watson et al. 2022). A tafenoquine dose of 450mg is predicted to provide >90% of the maximal effect. The objective of this research is to find out whether 450 mg dose of tafenoquine can be combined effectively with ACT providing a short course treatment for P. vivax malaria.

Detailed Description
-----------------
Plasmodium vivax malaria is a major cause of morbidity and is a significant contributor to mortality in tropical regions (Battle et al. 2019). Relapses are the major cause of illness and in higher transmission settings contribute to severe anaemia and death in young children as well as pregnancy loss. SE Asia has the highest proportion of the estimated global burden of P. vivax malaria burden 51.2% (7.2 million of 14.3 million) in 2017. In SE Asia over half of the patients treated for an acute P. vivax blood stage infection will develop at least one relapse (Betuela et al. 2012; Chu et al. 2018; Commons et al. 2019; Luxemburger et al. 1999; Poespoprodjo et al. 2009; Sutanto et al. 2013) if an anti-relapse drug is not given. The only widely available drug to prevent relapses (radical cure) currently is the 8-aminoquinoline primaquine. The doses of primaquine required to prevent relapses in Southeast Asia and the Western Pacific region are higher than elsewhere. P. vivax relapses more in these regions where with large populations over 80% of the global P. vivax burden occurs so it is likely that most of the world's relapses occur in East Asia and thus the benefits of effective radical cure are greatest in this area. Adherence to the currently recommended 14-day primaquine regimen is variable and this compromises widespread primaquine use and efficacy (Cheoymang et al. 2015; Grietens et al. 2010; Leslie et al. 2004; Maneeboonyang et al. 2011) . Recently a slowly eliminated 8-aminoquinoline, tafenoquine, has become available and has been registered in several countries. Tafenoquine can be given in a single dose (Lacerda et al. 2019; Llanos-Cuentas et al. 2014a; Llanos-Cuentas et al. 2019) which allows supervised dosing. However, tafenoquine is contraindicated in persons with G6PD activity below 70% as it may cause significant haemolysis in G6PD deficiency (including in female heterozygotes who may test as normal with current qualitative screens). Thus, quantitative G6PD deficiency testing is required to identify individuals with intermediate G6PD activity to ensure that female G6PD deficiency heterozygotes are not enrolled. Near patient quantitative G6PD tests (G6PD Biosensor) (Bancone et al. 2018; Pal et al. 2019; Zobrist et al. 2021) which provide a quantitative result will be used before tafenoquine is prescribed. The currently recommended tafenoquine dose is sub-optimal. The 300 mg dose proved significantly inferior to low dose primaquine in a meta-analysis of the phase 3 studies when restricted to the Southeast Asian region (Llanos-Cuentas et al. 2019; Watson et al. 2022). These data and an individual patient data meta-analysis of all (>1000) patients in the pre-registration studies (Watson et al. 2022) suggest that a 450mg adult dose of tafenoquine is needed in the Southeast Asian and Western Pacific regions (Figures 2-3). Doses up to 1200mg have proved safe and well tolerated in G6PD normal individuals. However a recent study suggests that ACTs may antagonize the curative efficacy of tafenoquine. If true this would complicate current treatment of both falciparum and vivax malaria with a single blood stage drug. The results from the INSPECTOR trial in Indonesian soldiers returning to non-endemic areas showed very low radical curative efficacy with tafenoquine in combination with DHA-PPQ (21%) - an efficacy which was similar to DHA-PPQ alone (11%) (Baird et al. 2020). This has prompted a product label update for Krintafel® (the branded form of tafenoquine in the USA) that tafenoquine should be combined only with chloroquine and not with other antimalarials such as artemisinin-based combination therapies (ACT)(CDC 2020). This now prevents the use of tafenoquine in areas with chloroquine resistant P. vivax parasites where national malaria programmes recommend ACTs for vivax malaria. As chloroquine resistance in P. vivax is increasing this poses a serious challenge to the potential use of this new radical cure antimalarial. However, this result is at variance with our earlier studies with the structurally and mechanistically similar primaquine, where radical curative efficacies were similar with DHA-PPQ and chloroquine combinations (Chu et al. 2019) . Whether DHA-PPQ can be combined effectively with tafenoquine needs to be resolved quickly to guide deployment. Tafenoquine could be particularly valuable in conflict-torn Myanmar where vivax malaria is now out of control and health services have broken down. This clinical trial and operational assessment will be performed within the established network of village health workers (VHW) in Eastern Myanmar. Scientific Rationale Tafenoquine, as a single dose regimen, has a tremendous advantage over the longer courses of primaquine needed for radical cure. Its use will be progressively restricted if it cannot be used in combination with ACTs. This trial will assess whether or not DHA-PPQ significantly reduces tafenoquine radical curative efficacy in comparison with chloroquine.

Official Title
-----------------
Does Artemisinin Combination Treatment Reduce the Radical Curative Efficacy of High Dose Tafenoquine for Plasmodium Vivax Malaria?

Conditions
-----------------
Malaria, Malaria, Vivax, Plasmodium Vivax Malaria

Intervention / Treatment
-----------------
* Drug: Dihydroartemisinin-piperaquine plus tafenoquine (450 mg adult dose)
* Drug: Chloroquine plus Tafenoquine (450 mg adult dose)


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Patients with P. vivax mono-infection as diagnosed by Rapid Diagnostic Test Fever or history of fever in the previous 7 days Quantitative G6PD activity ≥70% of the population median i.e., ≥6.1U/gHb Age > 18 years, Weight >35 kg Ability to understand the study instructions and provide informed consent Willing to be followed for 4 months and likely to adhere to the study protocol. Exclusion Criteria: Coincident P. falciparum malaria or other infections Pregnancy Lactation Hb < 8 g/dL Quantitative G6PD activity <70% of the population median i.e., <6.1U/gHb Severe malaria (as per WHO guideline) History of allergic or haemolytic response to any of the study drugs

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Randomised open label non-inferiority trial
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Dihydroartemisinin-piperaquine plus tafenoquine (450 mg adult dose)<br>Dihydroartemisinin-Piperaquine will be purchased as Duo-Cotecxin® Beijing Holley-Cotec Pharmaceuticals Co., Ltd, China). One tablet contains 40 mg of dihydroartemisinin and 320 mg piperaquine (i.e. a 1:8 ratio). A weight-based regimen containing a total dose of approximately 7 mg/kg DHA and 55 mg/kg piperaquine given in 3 divided doses once daily. Tafenoquine KOZENIS® 150 mg film-coated tablets will be purchased from GSK (Glaxo Smith Kline Pharmaceutical industry), 450 mg (3 tablets) will be given. | Drug: Dihydroartemisinin-piperaquine plus tafenoquine (450 mg adult dose)<br>* Dihydroartemisinin-Piperaquine will be purchased as Duo-Cotecxin® Beijing Holley-Cotec Pharmaceuticals Co., Ltd, China). One tablet contains 40 mg of dihydroartemisinin and 320 mg piperaquine (i.e. a 1:8 ratio). A weight-based regimen containing a total dose of approximately 7 mg/kg DHA and 55 mg/kg piperaquine given in 3 divided doses once daily. Tafenoquine KOZENIS® 150 mg film-coated tablets will be purchased from GSK (Glaxo Smith Kline Pharmaceutical industry), 450 mg (3 tablets) will be given.<br>|
| Experimental: Chloroquine plus Tafenoquine (450 mg adult dose)<br>Chloroquine will be dosed as a 25 mg/kg base given in divided doses of 10 mg/kg orally on days 0 and 1, and in 5 mg/kg dose on day 2. Tablets will be obtained from Government Pharmaceutical Organization (GPO) in Bangkok, Thailand and supplied as 250 mg tablets (155.3 mg base). Tafenoquine KOZENIS® 150 mg film-coated tablets will be purchased from GSK (Glaxo Smith Kline Pharmaceutical industry), 450 mg (3 tablets) will be given. | Drug: Chloroquine plus Tafenoquine (450 mg adult dose)<br>* Chloroquine will be dosed as a 25 mg/kg base given in divided doses of 10 mg/kg orally on days 0 and 1, and in 5 mg/kg dose on day 2. Tablets will be obtained from Government Pharmaceutical Organization (GPO) in Bangkok, Thailand and supplied as 250 mg tablets (155.3 mg base). Tafenoquine KOZENIS® 150 mg film-coated tablets will be purchased from GSK (Glaxo Smith Kline Pharmaceutical industry), 450 mg (3 tablets) will be given.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Determine whether DHA-PPQ plus TQ is non-inferior to CQ plus TQ | Number of participants with relapse-free efficacy (measured by PCR) | Month-4 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Characterise the safety and tolerability of both regimens | Number of participants with drop in hemoglobin ≥2 g/dL and/or hematocrit by ≥10% from baseline Number of participants with Non-serious Adverse Events (Non-SAEs) and Serious Adverse Events (SAEs) | Day3, Day7, Month1, Month2, Month3, Month4 | 
| Characterise population pharmacokinetics of tafenoquine in both DHA-PPQ and CQ regimens | Area Under the Curve From Time-0 Extrapolated to Infinite Time (AUC0-infinite time) of Tafenoquine | Day3, Day7, Month1, Month2, Month3, Month4 | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
artemisinin combination treatment, tafenoquine, Plasmodium vivax malaria, Malaria