A Phase 2 interventional study of Chloroquine and Tafenoquine in Plasmodium Vivax Malaria and Vivax Malaria, sponsored by University of Oxford. Not yet recruiting at 2 sites in 2 countries. Open to participants aged 28 Days and older. Per ClinicalTrials.gov, last updated 2026-09-22.
Sponsored by University of Oxford · Phase 2, Interventional, and Treatment
This study is an open label, single arm, pharmacokinetic trial. A total of 20 participants (children ≤12kg and >28 days old) will be enrolled. Enrollment will be competitive between Thailand and Vietnam study sites (each site will enroll as many patients that are eligible until the sample size is reached). Tafenoquine will be given concomitantly with the schizonticidal agent, chloroquine, on the day of enrolment. The participant will be admitted to hospital for observation and until the malaria smear is negative for asexual parasites on 2 consecutive days or until the schizonticidal treatment is completed, which will be approximately 3-7 days. All treatment doses will be supervised. Follow up will continue on days 7, 14, 21, and 28 then every month until month 4. Parent/guardian of participants will be instructed to follow up in between visits if participants are feeling unwell. Participants who are lost to follow up (any missed visit), who require drug re-administration after vomiting, or where at least 3 pharmacokinetic samples are not successfully drawn, will be replaced. Participants being replaced will continue in the study for safety assessments and to ensure the treatment of recurrences. The total blood drawn for this study will be 3.76 mL if the participant has no recurrences.
Objectives:
Primary Objective:
Secondary Objectives:
Recruitment
Potential participants will be recruited from the outpatient setting at the following sites:
This study recruits P. vivax patients who seek treatment at public or local health facilities. The malaria diagnosis will be performed by designated staff (such as the research team or government health care staff) at each facility. The patients who are diagnosed with P. vivax malaria by blood rapid diagnostic test (RDT) or malaria smear will be invited to participate in the study.
The trained study staff will explain the following; 1) The nature of the study; 2) The nature of the data collected; 3) Confidentiality and vulnerability; 4) Safety and alternatives; 5) The potential risks involved; 6) The potential benefits to the participants. A properly signed consent form by the parent/guardian of the patient will be obtained before participation.
Following written informed consent from a parent/guardian, participants will undergo screening with finger-prick haemoglobin and G6PD enzyme activity testing to confirm eligibility. Age-adjusted G6PD activity thresholds, based on 70% of the median activity for children aged 28 days to 4 months, will be applied for participants >28 days to 6 months and ≥6 months to 2 years of age. Eligible participants will be enrolled and undergo venous blood collection (3.14 mL on Day 0) using standard sterile venipuncture procedures. Blood samples will be labelled according to study requirements. Total blood volume collected during the study will be approximately 3.76 mL for participants without recurrence.
All study drug administrations will be directly observed by study staff to ensure adherence. Tafenoquine dosing will be weight-based: \<5 kg, 25 mg; ≥5 kg to \<10 kg, 50 mg; and ≥10 kg to 12 kg, 100 mg. Participants will be observed during dosing and compliance monitored throughout the study. If vomiting occurs within 30 minutes of administration, the full dose will be re-administered; if vomiting occurs 31 to 60 minutes after administration, half the dose will be re-administered. At each observed dosing visit, study staff will record adverse events, vital signs, and the date and time of study drug administration, and review available laboratory results before dosing.
After enrolment, participants will be admitted for observation and supervised treatment until malaria smears are negative on two consecutive days or schizonticidal treatment is completed (approximately 3 to 7 days). Follow-up visits will occur on Days 7, 14, 21, and 28, and Months 2, 3, and 4. Scheduled assessments include medication and concomitant medication review, adverse event monitoring, vital signs, physical examination, collection of protocol-specified blood and urine samples, and review of laboratory results. Visit windows are ±3 days for Days 7, 14, and 21; +2 weeks/-3 days for Day 28; and ±2 weeks for Months 2, 3, and 4.
At Month 4, participants with unresolved adverse events will be referred for appropriate clinical follow-up. Participants experiencing Plasmodium vivax recurrence will be treated according to national guidelines and will repeat study assessments from Day 0, excluding complete blood count and biochemistry testing. Additional assessments will include haemoglobin (Hemocue® Hb 301), malaria smear, methaemoglobin, and chloroquine and tafenoquine drug level measurements. Follow-up will then continue according to the Day 0 schedule, without extending the overall study duration.
The study will end after completion of the last study visit of the last participant.
This project is funded by the National Institutes of Health (NIH), award number U01AI195203.
123 studies on the registry are indexed under Malaria, Vivax; 19 are open to participants now.
This study's planned enrollment of 20 is below the median of 150 across 103 interventional studies indexed under Malaria, Vivax.
Browse Malaria, Vivax studies →University of Oxford is the lead sponsor of 812 studies on the registry; 119 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants with Plasmodium vivax malaria will receive oral chloroquine and tafenoquine under direct observation. Chloroquine tablets (250 mg) will be administered at a total dose of 25 mg/kg base divided over 3 days (Days 0, 1, and 2) as schizonticidal treatment. Tafenoquine will be administered as a single oral dose for radical cure according to body weight: 25 mg for participants weighing \<5 kg, 50 mg for participants weighing ≥5 kg to \<10 kg, and 100 mg for participants weighing ≥10 kg to 12 kg. Participants will be followed for safety, efficacy, pharmacokinetics, and recurrence of P. vivax malaria for 4 months.
Drug: Chloroquine · Drug: Tafenoquine
Oral chloroquine tablets (250 mg). Total dose of 25 mg/kg base divided over 3 days (Days 0, 1, and 2).
Single oral dose administered according to body weight: 25 mg for \<5 kg; 50 mg for ≥5 kg to \<10 kg; 100 mg for ≥10 kg to 12 kg.
Tafenoquine blood concentration-time curve area under the curve from time zero to infinity (AUC[0-∞])
The area under the tafenoquine concentration-time curve from time zero to infinity (AUC\[0-∞\]) will be estimated from the concentration-time data.
Time frame: days 1, 7, 28 and month 4
Maximum observed tafenoquine blood concentration (Cmax)
Maximum observed blood concentration (Cmax) will be estimated from the concentration-time data.
Time frame: days 1, 7, 28 and month 4
Terminal elimination half-life of tafenoquine (t½)
Terminal elimination half-life (t½) will be estimated from the concentration-time data.
Time frame: days 1, 7, 28 and month 4
Number of adverse events and serious adverse events
The number of treatment-emergent adverse events and serious adverse events reported by caregivers, observed by study staff, or identified through clinical assessments will be recorded from treatment initiation through Month 4.
Time frame: up to month 4
Methaemoglobin levels measured by oximetry
Methaemoglobin levels will be measured by oximetry on Day 7 to assess the hematologic safety profile of tafenoquine treatment.
Time frame: day 7
CYP2D6 genotype and associated phenotype as defined by the Clinical Pharmacogenetics Implementation Consortium (CPIC)
CYP2D6 genotype will be determined and translated into predicted metabolizer phenotype according to Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines to evaluate genetic variation in drug metabolism.
Time frame: up to month 4
Plan to share: Yes — Participant's data and results from blood analyses stored in the database may be shared according to the terms defined in the MORU data sharing policy (https://www.tropmedres.ac/units/moru-bangkok/bioethics-engagement/data-sharing/moru-tropical-network-policy-on-sharing-data-and-other-outputs) or other researchers to use in the future. All personal information will be anonymised so that no individual can be identified from their treatment records. The genomic data sharing plan will be shared on a public database and the plan will be kept in the Regulatory Binder (or manual of procedures).
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This study is not yet recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Tafenoquine