A Phase 2 interventional study of Tecovirimat Oral Capsule and Placebo in Monkeypox, sponsored by National Institute of Allergy and Infectious Diseases (NIAID). Completed at 2 sites in Democratic Republic of the Congo. Per ClinicalTrials.gov, last updated 2025-10-09.
Sponsored by National Institute of Allergy and Infectious Diseases (NIAID) · Phase 2, Interventional, and Treatment
The purpose of this study is to find out if tecovirimat is a safe and effective drug to treat monkeypox (mpox) in combination with standard of care (SOC). Participants will be randomly assigned to receive oral tecovirimat plus SOC or placebo plus SOC for 14 days.
This is a randomized, placebo-controlled, double-blind study to test the antiviral drug tecovirimat for the treatment of adults and children with laboratory-confirmed monkeypox virus (MPXV) disease at participating sites in the Democratic Republic of Congo. Eligible and consented participants will be randomized 1:1 to receive either oral tecovirimat or placebo, each administered in the hospital with standard-of-care (SOC) treatment for 14 days. Participants will be followed for 28 days with an optional visit at Day 59 for long-term assessment.
If a participant reaches full body lesion resolution but subsequently develops at least one new lesion consistent with mpox after discharge but while still enrolled in the study, they will be eligible to make a sick visit and will be offered standard of care for mpox.
72 studies on the registry are indexed under Mpox, Monkeypox; 30 are open to participants now.
This study's enrollment of 597 is above the median of 305 across 36 interventional studies indexed under Mpox, Monkeypox.
Browse Mpox, Monkeypox studies →National Institute of Allergy and Infectious Diseases (NIAID) is the lead sponsor of 2,446 studies on the registry; 179 are open to participants now.
Of its 405 completed or terminated interventional studies of FDA-regulated products, 302 (75%) have results posted.
Counted across the registry records on this site, refreshed daily.
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.
This study has no age restriction.
Inclusion Criteria:
Men and non-pregnant women of must agree to use effective means of when engaging in sexual activities that can result in pregnancy, from the time of enrollment through the end of study participation. Acceptable methods of contraception include the following:
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.
Able to have children. For women this usually means from the first period until menopause, unless permanently unable to through surgery; for men, unless permanently sterile. Read who the line is about — participants, women, men, or their partners.
Criteria about it usually ask for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
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).
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.
Reproductive potential
Able to have children. For women this usually means from the first period until menopause, unless permanently unable to through surgery; for men, unless permanently sterile. Read who the line is about — participants, women, men, or their partners.
Criteria about it usually ask for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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.
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.
Tecovirimat capsules administered orally to participants for 14 days plus SOC.
Drug: Tecovirimat Oral Capsule
Matching placebo capsules administered orally to participants for 14 days plus SOC.
Drug: Placebo
200 mg capsules Number of capsules and frequency of dosage will be based on participant weight: * ≥120 kg: three capsules three times a day (total daily tecovirimat dose: 1,800 mg) * 40 to \<120 kg: three capsules twice a day (total daily tecovirimat dose: 1,200 mg) * 25 to \<40 kg: two capsules twice a day (total daily tecovirimat dose: 800 mg) * 13 to \<25 kg: one capsule twice a day (total daily tecovirimat dose: 400 mg) * 6 to \<13 kg: ½ the contents of a capsule twice daily (total daily tecovirimat dose: 200 mg) * 3 to \<6 kg: ¼ the contents of a capsule twice daily (total daily tecovirimat dose: 100 mg)
Also known as: TPOXX
Capsules to match tecovirimat
Time to Lesion Resolution
Number of days from randomization to the first day on which all lesions on the total body are scabbed or desquamated or a new layer of epidermis has formed.
Time frame: Up to day 28
Time to Lesion Resolution for Participants With Symptom Onset Less Than or Equal to 7 Days Before Randomization
Number of days to the first day on which all lesions on the total body are scabbed or desquamated or a new layer of epidermis has formed.
Time frame: up to day 28
Time to Lesion Resolution for Participants With Symptom Onset Greater Than 7 Days Before Randomization
Number of days to the first day on which all lesions on the total body are scabbed or desquamated or a new layer of epidermis has formed.
Time frame: up to day 28
Number and Percentage of Participants With Negative Blood PCR Results
Percentage of participants with negative blood sample MPXV PCR results 14 days post-randomization, out of those positive at baseline
Time frame: day 14
Number and Percentage of Participants With Negative Oropharyngeal Swab PCR Results
Number and percentage of participants with negative oropharyngeal swab MPXV PCR results 14 days post-randomization, out of those positive at baseline
Time frame: day 14
Number and Percentage of Participants With Negative Lesion Swab PCR Results
Number and and percentage of participants with negative lesion swab MPXV PCR results 14 days post-randomization, of those positive at baseline
Time frame: day 14
Mortality Within the First 28 Days Post-randomization
Number of deaths post-randomization
Time frame: up to day 28
Incidence of Non-fatal Serious Adverse Events Requiring Permanent Drug Discontinuation
Number of participants with a non-fatal serious adverse event requiring permanent drug discontinuation through the end of the treatment period (14 days)
Time frame: Up to day 14
Incidence of Non-fatal Adverse Events Requiring Permanent Drug Discontinuation
Number of participants with a non-fatal adverse event requiring permanent drug discontinuation through the end of the treatment period (14 days)
Time frame: Up to day 14
Incidence of Adverse Events
Number of participants with an adverse event up to day 28
Time frame: up to day 28
Incidence of Bacterial Infection Adverse Events
Number of participants with a bacterial infection adverse event up to day 28
Time frame: up to day 28
Patients were recruited from the areas surrounding two sites in rural Democratic Republic of the Congo - Tunda and Kole. Patient recruitment took place from October 2022 through July 9, 2024.
| Milestone | Tecovirimat | Placebo |
|---|---|---|
| Started | 295 | 302 |
| Completed | 289 | 295 |
| Not completed | 6 | 7 |
| Withdrew: Death | 5 | 4 |
| Withdrew: Lost to follow-up | 0 | 2 |
| Withdrew: Adverse event | 1 | 1 |
Number of days from randomization to the first day on which all lesions on the total body are scabbed or desquamated or a new layer of epidermis has formed.
| Days | Tecovirimat | Placebo |
|---|---|---|
| Time to Lesion Resolution | 7 (7 to 8) | 8 (7 to 9) |
Number of days to the first day on which all lesions on the total body are scabbed or desquamated or a new layer of epidermis has formed.
| Days | Tecovirimat | Placebo |
|---|---|---|
| Time to Lesion Resolution for Participants With Symptom Onset Less Than or Equal to 7 Days Before Randomization | 7 (7 to 8) | 8 (7 to 8) |
Number of days to the first day on which all lesions on the total body are scabbed or desquamated or a new layer of epidermis has formed.
| Days | Tecovirimat | Placebo |
|---|---|---|
| Time to Lesion Resolution for Participants With Symptom Onset Greater Than 7 Days Before Randomization | 8 (7 to 10) | 8 (7 to 11) |
Percentage of participants with negative blood sample MPXV PCR results 14 days post-randomization, out of those positive at baseline
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Number and Percentage of Participants With Negative Blood PCR Results | 140 | 141 |
Number and percentage of participants with negative oropharyngeal swab MPXV PCR results 14 days post-randomization, out of those positive at baseline
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Number and Percentage of Participants With Negative Oropharyngeal Swab PCR Results | 144 | 136 |
Number and and percentage of participants with negative lesion swab MPXV PCR results 14 days post-randomization, of those positive at baseline
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Number and Percentage of Participants With Negative Lesion Swab PCR Results | 256 | 259 |
Number of deaths post-randomization
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Mortality Within the First 28 Days Post-randomization | 3 | 4 |
Number of participants with a non-fatal serious adverse event requiring permanent drug discontinuation through the end of the treatment period (14 days)
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Incidence of Non-fatal Serious Adverse Events Requiring Permanent Drug Discontinuation | 0 | 2 |
Number of participants with a non-fatal adverse event requiring permanent drug discontinuation through the end of the treatment period (14 days)
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Incidence of Non-fatal Adverse Events Requiring Permanent Drug Discontinuation | 1 | 0 |
Number of participants with an adverse event up to day 28
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Incidence of Adverse Events | 196 | 199 |
Number of participants with a bacterial infection adverse event up to day 28
| Participants | Tecovirimat | Placebo |
|---|---|---|
| Incidence of Bacterial Infection Adverse Events | 23 | 27 |
Collected over From enrollment until the end of follow-up, up to 58 days. Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Tecovirimat | 5/295 (1.7%) | 15/295 (5.1%) | 214/295 (72.5%) |
| Placebo | 5/302 (1.7%) | 15/302 (5%) | 211/302 (69.9%) |
| Event | Tecovirimat | Placebo |
|---|---|---|
| AnaemiaBlood and lymphatic system disorders | 3/295 | 3/302 |
| Complicated malariaInfections and infestations | 2/295 | 1/302 |
| Septic shockInfections and infestations | 2/295 | 1/302 |
| Foetal deathPregnancy, puerperium and perinatal conditions | 2/295 | 2/302 |
| SepsisInfections and infestations | 0/295 | 2/302 |
| Respiratory distressRespiratory, thoracic and mediastinal disorders | 0/295 | 2/302 |
| Gastrointestinal haemorrhageGastrointestinal disorders | 1/295 | 0/302 |
| Hepatic failureHepatobiliary disorders | 1/295 | 0/302 |
| EndometritisInfections and infestations | 1/295 | 0/302 |
| Keratitis viralInfections and infestations | 1/295 | 0/302 |
| Event | Tecovirimat | Placebo |
|---|---|---|
| MalariaInfections and infestations | 34/295 | 54/302 |
| PyrexiaGeneral disorders | 39/295 | 43/302 |
| CoughRespiratory, thoracic and mediastinal disorders | 33/295 | 30/302 |
| Abdominal painGastrointestinal disorders | 31/295 | 26/302 |
| HeadacheNervous system disorders | 20/295 | 28/302 |
| Nasal congestionRespiratory, thoracic and mediastinal disorders | 18/295 | 27/302 |
| Decreased appetiteMetabolism and nutrition disorders | 20/295 | 14/302 |
| AnaemiaBlood and lymphatic system disorders | 16/295 | 19/302 |
| Haemoglobin decreasedInvestigations | 15/295 | 18/302 |
| PruritusSkin and subcutaneous tissue disorders | 14/295 | 18/302 |
Intention-to-treat primary analysis population
| Age, Continuous(Years) | Tecovirimat | Placebo | Total |
|---|---|---|---|
| Mean | 16.4 ± 13.9 | 15.3 ± 13.9 | 15.8 ± 13.9 |
| Sex: Female, Male(Participants) | Tecovirimat | Placebo | Total |
|---|---|---|---|
| Female | 141 | 151 | 292 |
| Male | 154 | 151 | 305 |
| Race and Ethnicity Not Collected(Participants) | Tecovirimat | Placebo | Total |
|---|---|---|---|
| Count of participants | — | — | 0 |
| Days since onset of symptoms(Days) | Tecovirimat | Placebo | Total |
|---|---|---|---|
| Mean | 5.9 ± 2.5 | 5.9 ± 2.8 | 5.9 ± 2.6 |
| Less than or equal to 7 days since onset of symptoms(Participants) | Tecovirimat | Placebo | Total |
|---|---|---|---|
| Count of participants | 234 | 239 | 473 |
| Greater than 7 days since onset of symptoms(Participants) | Tecovirimat | Placebo | Total |
|---|---|---|---|
| Count of participants | 61 | 63 | 124 |
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No
Ran from Oct 2022 to primary completion in Sep 2024, 22 months.
Results were first posted in Oct 2025, 1 year 1 month after primary completion.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Sep 2025. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Studies of the drug tested here: Tecovirimat
National Institute of Allergy and Infectious Diseases (NIAID) →