A Phase 3 interventional study of Tecovirimat and Placebo in Monkeypox and Mpox, sponsored by ANRS, Emerging Infectious Diseases. Active, not recruiting at 12 sites in 3 countries. Open to participants aged 14 Years and older. Per ClinicalTrials.gov, last updated 2026-05-26.
Sponsored by ANRS, Emerging Infectious Diseases · Phase 3, Interventional, and Treatment
The overall purpose of this study is to evaluate whether tecovirimat is an efficient and safe antiviral in the treatment of monkeypox in adults and adolescents (14 years old and older).
The primary objective is to evaluate the clinical efficacy, as assessed by time to all visible lesion(s) resolution, of tecovirimat treatment + Standard of Care (SOC) compared to placebo + SOC for patients with monkeypox.
The secondary objective is to evaluate the clinical efficacy, as assessed by mortality, hospitalization, complications, duration of symptoms and virological shedding, and the safety of tecovirimat treatment + SOC compared to placebo + SOC in patients with monkeypox.
The study presented here is the Swiss-Brazil co-sponsored adaptation of the UNITY trial based on the WHO core protocol. It has an original governance to better respond to public health priorities, each country being its own sponsor, allowing for an easier scale-up of the trial and local adaptations of the protocol.
Background and rationale:
Monkeypox is an emerging viral zoonosis caused by a virus of the same name that is closely related to smallpox. It is usually endemic in central and West Africa but since May 2022, the virus has rapidly disseminated to Europe, North and South America, Africa and Australia, and has predominantly affected gay, bisexual and other men who have sex with men (MSM) with multiple partners. On 23 July 2022, the World Health Organization (WHO) declared that the monkeypox outbreak was an international public health emergency. In particular, the WHO called for the use of antivirals for the treatment of monkeypox cases. This declaration must therefore be translated not only into extraordinary public health measures but also as a call for greater investment in research.
This study proposal is a national adaptation for Switzerland and Brazil based on the 'CORE protocol' developed by the WHO. The research team would like to emphasize that this randomized trial is international in scope. Thus, they are joining forces to achieve a more effective and rapid response to important questions, with a harmonized follow-up and in a time frame that can be useful to the patients the medical staff have been caring for since the very beginning of this epidemic. Candidate antivirals are already available for testing in monkeypox. The first studied treatment in this adaptative trial is the antiviral tecovirimat. Tecovirimat (TPOXX®, SIGA Technologies Inc.) is a treatment for smallpox, monkeypox and cowpox. Tecovirimat is approved by the European Medicine Agency (EMA) for this indication for adults and children weighing at least 13 kg, as well as by the United States Food and Drugs Administration (FDA) under expanded access investigational new drug protocol, but it is not yet approved in Switzerland and Brazil.
Objectives:
This study aims to evaluate whether tecovirimat is an efficient and safe antiviral in the treatment of monkeypox in adults and adolescents (14 years old and over).
The primary objective is to evaluate the clinical efficacy of tecovirimat treatment + standard of care (SOC) compared to placebo + SOC for patients with monkeypox as assessed by time to visible lesion(s) resolution. The secondary objectives are to evaluate the clinical efficacy and safety of tecovirimat treatment + SOC compared to placebo + SOC in patients with monkeypox as assessed by mortality, hospitalization, complications, duration of symptoms and virological shedding.
Methods:
This study will include adult and adolescent patients aged ≥14 years with a confirmed or highly suspected monkeypox virus infection and with at least one visible active skin or mucosal lesion. Individuals with a known hypersensitivity to tecovirimat, who are taking medications which cannot be interrupted and for which a major interaction has been described or who, in the judgement of the investigator, will be at significantly increased risk as a result of participation in the study will not be included. Randomization will be in a ratio of 1:1 to either tecovirimat treatment combined with SOC or to placebo combined with SOC. All participants will be followed-up until day 29 and additionally at day 60 for those who accept this last optional follow-up visit.
Outcome:
The primary outcome is the time for all visible lesions (skin, mucosal) to heal with a new fresh layer of skin re-epithelialization (i.e. resurfacing of a wound with a new epithelium layer).
Expected results:
The hypothesis is that prompt oral treatment with tecovirimat will result in a reduction of the duration of illness in patients with monkeypox that may correlate with the duration of contagiousness. It is expected that tecovirimat will be well tolerated and acceptable for these patients.
72 studies on the registry are indexed under Mpox, Monkeypox; 30 are open to participants now.
This study's planned enrollment of 480 is above the median of 305 across 36 interventional studies indexed under Mpox, Monkeypox.
Browse Mpox, Monkeypox studies →ANRS, Emerging Infectious Diseases is the lead sponsor of 215 studies on the registry; 38 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.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
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.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Drug: Tecovirimat
Drug: Placebo
The experimental intervention is tecovirimat, available as immediate-release capsules containing tecovirimat monohydrate, equivalent to 200 mg of tecovirimat. The route of administration of tecovirimat is oral. Tecovirimat treatment will be initiated as soon as possible after diagnosis. The international recommended doses will be followed: * 25 kg to less than 40 kg: 400 mg (two tecovirimat 200 mg capsules) every 12 hours for 14 consecutive days. * 40 kg and above: 600 mg (three tecovirimat 200 mg capsules) every 12 hours for 14 consecutive days.
The control intervention is a placebo and its route of administration will be identical to the experimental intervention administration to allow treatment arm blinding.
Time to all visible lesion(s) resolution
Time for all visible lesions (skin, mucosal) to heal with a new fresh layer of skin re-epithelialization (i.e resurfacing of a wound with a new epithelium layer). For skin lesions, typically this means the lesion has scabbed, desquamated and new layer of skin has been formed. For mucosal lesions, the phase of scabbing and desquamation is absent, and healing with new layer of skin ensues.
Time frame: 28 days
All-cause mortality within the first 28 days (applied to all patients)
All-cause mortality is more reliably measured than monkeypox-specific mortality. It is easy to measure and is reliable.
Time frame: 28 days
All-cause unplanned admission to hospital within first 28 days (applies to outpatients)
Most patients will be managed at home or in community and this outcome is an important patient-centered and health system outcome. All-cause is easier to measure than monkeypox specific and will ease data burden.
Time frame: 28 days
Occurrence of patients with a complication within first 28 days (applies to all patients who did not already have a complication at baseline)
Complications include secondary bacterial skin infection (cellulitis, abscess, necrotizing fasciitis, need for antibiotics), severe pain, ocular impairment (e.g. keratitis), neurologic impairment (e.g. encephalitis) or mental health disturbance, confusion, cardiac impairment (e.g. cardiomyopathy, myocarditis), severe dehydration, and genitourinary complications as urinary retention. Progression to complications is an important patient-centered outcome and an important health system outcome to prepare and anticipate clinical services for monkeypox cases. It is easy to measure, as long as definitions are clear, and the relevant staff is trained. Complications will be differentiated based on drug-related complications and disease-related complications.
Time frame: 28 days
Time to resolution of symptoms and signs within first 28 days (applies to all patients)
Symptoms include fatigue, malaise, nausea, vomiting, abdominal pain, anorexia, cough, dysphagia, odynophagia, fever, headache, oral pain, pain with urination, rectal/anal pain. Signs include lymphadenopathy, ocular lesions, pharyngitis, urethritis, and proctitis. Collection of symptoms and signs can be useful to understand the clinical characterization.
Time frame: 28 days
Viral clearance up to 28 days after randomization
Occurrence of negative oropharyngeal , rectal swab, and skin swab PCR results, respectively, 7, 14, 21 days and 28 days after randomization. Viral clearance assessment is important to evaluate whether treatment is also a route for reducing transmission.
Time frame: 28 days
Frequency of adverse events (AEs) and serious adverse events (SAEs) for specific therapeutics (applies to all patients)
The collection of standardized data of adverse events is of importance in order to increase the understanding of safety and tolerability of the treatment.
Time frame: 60 days
This study is active, not recruiting, as verified in May 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Tecovirimat
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