Active clinical trials for "Malaria, Vivax"

Plasmodium vivax malaria is difficult to manage because even after taking medicine that kills the infection in the blood, it can continue to hide quietly in the liver, later re-emerging into the blood and causing another episode of malaria illness (relapse). This clinical trial aims to enroll patient with P. vivax infections and try to detect signals in blood, urine and/or saliva coming from the silent liver stages to help identify who could benefit from treatment with primaquine. It also will explore if certain factors of patients negatively impact primaquine efficacy.

The study will be an open-labelled randomized clinical trial to determine therapeutic efficacy. Note that this will not be an Investigational New Drug application, as only World Health Organization (WHO)-approved drugs will be used at dosage and for conditions approved.

This study is designed as a multicentre randomized, open label trial to assess the safety and efficacy of a low dose short course PQ treatment (3.5mg/kg total dose given over 7 days) in glucose-6-phosphate dehydrogenase (G6PD) normal patients with P.vivax and P falciparum to reduce the risk of subsequent P.vivax episodes.

The main determinant of primaquine efficacy is the total dose of primaquine administered, rather than the dosing schedule. Infants and children younger than 4 years of age are at a higher risk of frequent relapses than older age groups, which may lead to severe anaemia. In view of this issue, after Glucose-6-phosphate dehydrogenase (G6PD) testing, WHO recommends the use of a low dose (0·25 mg/kg of bodyweight) of primaquine for 14 days in infants aged 6 months and older, as a follow-up treatment for malaria caused by P. vivax and P. ovale. Nevertheless, previous trials have demonstrated that the standard low dose regimen of primaquine (3.5 mg/kg total) fails to prevent relapses in many different endemic locations. For this reason, the 2010 WHO antimalarial guidelines now recommend a high dose regimen of 7 mg/kg (equivalent to an adult dose of 30mg per day), although many countries still recommend lower doses for fear of causing more serious harm to unscreened G6PD deficiency patients. The pharmacokinetics of several antimalarial drugs are different in children younger than 10 years of age or who are underweight for their age compared with children of 10 years and older and adults.The doses of several antimalarials in children are suboptimal. This oversight is a consequence of designing dosing regimens in a different population (i.e., adults) for the one most affected by the disease and this has led to revisions of some dosing recommendations. The different pharmacokinetic performance of drugs in children might also relate to maturation (e.g., of metabolic processes, particularly in the first 2 years of life). Pharmacogenomic factors affecting drug metabolism are increasingly being studied. Polymorphisms in cytochrome P4502D6 are associated with different primaquine metabolizer phenotypes with resulting differing efficacies for radical cure. Shorter courses of higher daily doses of primaquine have the potential to improve adherence and, thus, effectiveness without compromising efficacy. If the efficacy, tolerability and safety of short-course, high-dose primaquine regimens can be assured across the range of endemic settings, along with reliable point-of-care G6PD deficiency diagnostics, then this would be a major advance in malaria treatment by improving adherence and thus the effectiveness of anti-relapse therapy.

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.

Health care facility based, randomized, controlled, open label, superiority trial with 3 arms

This is an Open label, first-in-human, Phase I/IIa, blood-stage P. vivax malaria vaccine trial to assess the safety, immunogenicity and efficacy of the blood-stage Plasmodium vivax malaria vaccine candidate PvDBPII in Matrix M1 in healthy adults living in the UK.

This study assesses the effectiveness of reactive focal mass drug administration (rfMDA), targeting both village and forest working populations, compared to control for reducing the health promotion hospital-level (sub-district) incidence and prevalence of P. falciparum and P. vivax within five provinces in Thailand.

Significant gains have been made in reducing the overall burden of malaria worldwide, however these have been far greater for Plasmodium falciparum than P. vivax. P. vivax remains a major obstacle to malaria control and elimination efforts, largely due to its ability to form dormant liver stages (hypnozoites) that allows it to escape detection and treatment. Importantly, they are susceptible only to 8 aminoquinolines such as primaquine. However, primaquine is associated with risk of haemolysis in individuals with a genetic condition, called glucose-6-phosphate dehydrogenase (G6PD) deficiency. Additionally, the recommended 14-day prolonged treatment regimen is associated with poor treatment adherence, hence ineffective primaquine treatment. Innovative solutions to the radical cure of both the blood and liver stages of P. vivax are urgently required. The PNG National Department of Health has requested a pragmatic study of the feasibility and cost-effectiveness of implementing point-of-care G6PD testing followed by high-dose, short-course primaquine treatment regimens for patients with P. vivax malaria. This revised case management is to be combined with practicable enhancements to patient education, supervision, malariometric surveillance and pharmacovigilance. This will be a before-after longitudinal health facility-based study implemented at Napapar and Mugil health centres and Baro and Wirui clinics. A staged approach for the implementation of the revised case management strategy will be used, including patient education and counselling, community-based clinical review, with mixed methods evaluation.

This study is a human challenge study to assess the feasibility and safety of controlled human malaria infection (via P. vivax sporozites) in healthy volunteers, and to develop a bank of P. vivax-infected blood for use in future controlled human P. vivax malaria infection studies. Additional objectives are to obtain data on host immune response to P. vivax infection and pre-treatment gametocytaemia. This study is funded by the UK Wellcome Trust. The grant reference number are Oxford/MORU: 212336/Z/18/Z and 212336/Z/18/A, and Mahidol University: 212336/A/18/Z and 212336/A/18/A.