A Phase 2 interventional study of ST-246 400 mg and ST-246 600 mg in Orthopoxviral Disease, sponsored by SIGA Technologies. Completed at 3 sites in United States. Open to participants aged 18 Years to 75 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-11.
Sponsored by SIGA Technologies · Phase 2, Interventional, and Other
The purpose of this study was to assess the safety, tolerability, and pharmacokinetics of two clinical doses of the anti-orthopoxvirus drug, ST-246, administered as a single daily oral dose for 14 days to healthy, fed volunteers. The results of this trial determine which dose will be used in expanded pivotal safety trials.
This study is a Phase II, double-blind, randomized, placebo-controlled, multi-center (3 sites) trial to assess the safety, tolerability, and pharmacokinetics of 400 mg and 600 mg Form I ST-246 when administered as a single daily oral dose for 14 days to 107 healthy, fed volunteers between 18 and 74 years of age. Safety parameters included adverse events, vital signs, physical examinations, laboratory tests (hematology, blood chemistry, and urinalysis) and electrocardiograms.
73 studies on the registry are indexed under Smallpox; 5 are open to participants now.
This study's enrollment of 107 is below the median of 150 across 61 interventional studies indexed under Smallpox.
Browse Smallpox studies →SIGA Technologies is the lead sponsor of 9 studies on the registry; none are open to participants now.
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.
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.
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.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
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.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECG (electrocardiogram)
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ST-246 400mg (2 x 200 mg Capsules) Orally Once Daily for 14 days
Drug: ST-246 400 mg
ST-246 600 mg (3 x 200 mg Capsules) Orally Once Daily for 14 days
Drug: ST-246 600 mg
Matching Placebo capsules, Orally Once Daily for 14 days
Drug: Placebo
Capsules, 400 mg daily for 14 days
Also known as: Tecovirimat
Capsules, 600 mg daily for 14 days
Also known as: Tecovirimat
Capsules, once daily for 14 days
Number of Study Participants Who Tolerated a Single Daily Oral ST-246 Dose as Determined by Safety Parameter Changes According to the DAIDS (Division of Acquired Immunodeficiency Syndrome) Adverse Events (AE) Grading Table.
Subjects were administered a single, daily oral dose of ST-246 (400 or 600 mg)and changes in safety parameteres were monitored. Safety parameters included adverse events, vital signs, physical examinations, laboratory tests (hematology, blood chemistry, and urinalysis) and electrocardiograms. The DAIDS AE grading table is a list of common terms and severity (intensity) of parameters used to describe adverse events occurring in NIAID-sponsored clinical studies/trials.
Time frame: Days 1 to 14; then 24, 48, 72, 96 and 120 hours and 4 weeks after final dose
Evaluation of Pharmacokinetic Parameters to Assess Interventions: Cmax
Cmax: Maximum drug concentration in plasma determined directly from individual concentration-time data
Time frame: Day 1 post-dose
Evaluation of Pharmacokinetic Parameters to Assess Interventions: Cmax
Cmax: Maximum drug concentration in plasma determined directly from individual concentration-time data
Time frame: Day 14 post-dose
Evaluation of Pharmacokinetic Parameters to Assess Interventions: Tmax
Tmax: Time to reach maximum drug concentration in plasma calculated from \[plasma\] versus time profiles
Time frame: Day 1 post-dose
Evaluation of Pharmacokinetic Parameters to Assess Interventions: Tmax
Tmax: Time to reach maximum drug concentration in plasma calculated from \[plasma\] versus time profiles
Time frame: Day 14 post-dose
Evaluation of Pharmacokinetic Parameters to Assess Interventions: AUCtau
AUCtau: Area under the plasma concentration-time curve for each dosing interval (from time 0 to 24 hours sample) determined using the linear trapezoidal rule
Time frame: Day 1 post-dose
Evaluation of Pharmacokinetic Parameters to Assess Interventions: AUCtau
AUCtau: Area under the plasma concentration-time curve for each dosing interval (from time 0 to 24 hours sample) determined using the linear trapezoidal rule
Time frame: Day 14 post-dose
Evaluation of Pharmacokinetic Parameters to Assess Interventions: t½
t½: Observed terminal elimination half-life determined after the last dose on Day 14
Time frame: Day 14 post-dose
This study was conducted at three sites: Apex Research Institute, Santa Ana, CA, Hawaii Clinical Research Center, Honolulu, HI, and Orlando Clinical Research Center, Orlando, FL. The study was conducted in male and female volunteers ages 18 - 75 years inclusive from the sites' databases.
| Milestone | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Started | 45 | 46 | 16 |
| Completed | 42 | 43 | 16 |
| Not completed | 3 | 3 | 0 |
| Withdrew: Withdrawal of consent - long commute | 1 | 0 | 0 |
| Withdrew: Adverse event | 2 | 0 | 0 |
| Withdrew: Withdrawal by subject | 0 | 1 | 0 |
| Withdrew: Lost to follow-up | 0 | 1 | 0 |
| Withdrew: Protocol violation | 0 | 1 | 0 |
Subjects were administered a single, daily oral dose of ST-246 (400 or 600 mg)and changes in safety parameteres were monitored. Safety parameters included adverse events, vital signs, physical examinations, laboratory tests (hematology, blood chemistry, and urinalysis) and electrocardiograms. The DAIDS AE grading table is a list of common terms and severity (intensity) of parameters used to describe adverse events occurring in NIAID-sponsored clinical studies/trials.
| Participants | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Number of Study Participants Who Tolerated a Single Daily Oral ST-246 Dose as Determined by Safety Parameter Changes According to the DAIDS (Division of Acquired Immunodeficiency Syndrome) Adverse Events (AE) Grading Table. | 34 | 38 | 15 |
Cmax: Maximum drug concentration in plasma determined directly from individual concentration-time data
| ng/mL | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Evaluation of Pharmacokinetic Parameters to Assess Interventions: Cmax | 1170 ± 429 | 1467 ± 626 | — |
Cmax: Maximum drug concentration in plasma determined directly from individual concentration-time data
| ng/mL | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Evaluation of Pharmacokinetic Parameters to Assess Interventions: Cmax | 1286 ± 449 | 1523 ± 607 | — |
Tmax: Time to reach maximum drug concentration in plasma calculated from \[plasma\] versus time profiles
| hours | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Evaluation of Pharmacokinetic Parameters to Assess Interventions: Tmax | 4 ± 1 | 4 ± 1 | — |
Tmax: Time to reach maximum drug concentration in plasma calculated from \[plasma\] versus time profiles
| hours | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Evaluation of Pharmacokinetic Parameters to Assess Interventions: Tmax | 4 ± 1 | 3 ± 1 | — |
AUCtau: Area under the plasma concentration-time curve for each dosing interval (from time 0 to 24 hours sample) determined using the linear trapezoidal rule
| ng*hr/mL | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Evaluation of Pharmacokinetic Parameters to Assess Interventions: AUCtau | 11329 ± 4945 | 13895 ± 5702 | — |
AUCtau: Area under the plasma concentration-time curve for each dosing interval (from time 0 to 24 hours sample) determined using the linear trapezoidal rule
| ng*hr/mL | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Evaluation of Pharmacokinetic Parameters to Assess Interventions: AUCtau | 12026 ± 4255 | 14791 ± 5712 | — |
t½: Observed terminal elimination half-life determined after the last dose on Day 14
| hours | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| Evaluation of Pharmacokinetic Parameters to Assess Interventions: t½ | 26 ± 11 | 24 ± 15 | — |
Collected over 6 weeks. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| ST-246 400 mg | — | 0/45 (0%) | 11/45 (24.4%) |
| ST-246 600 mg | — | 0/46 (0%) | 8/46 (17.4%) |
| Placebo | — | 0/16 (0%) | 1/16 (6.3%) |
| Event | ST-246 400 mg | ST-246 600 mg | Placebo |
|---|---|---|---|
| HeadacheNervous system disorders | 2/45 | 5/46 | 1/16 |
| NauseaGastrointestinal disorders | 3/45 | 2/46 | 1/16 |
| Dry mouthGastrointestinal disorders | 0/45 | 1/46 | 1/16 |
| PalpitationsCardiac disorders | 0/45 | 0/46 | 1/16 |
| FatigueGeneral disorders and administration site conditions | 1/45 | 2/46 | 0/16 |
| Abdominal distensionGastrointestinal disorders | 1/45 | 0/46 | 0/16 |
| Axillary painGeneral disorders and administration site conditions | 1/45 | 0/46 | 0/16 |
| Back painMusculoskeletal and connective tissue disorders | 1/45 | 0/46 | 0/16 |
| DizzinessNervous system disorders | 1/45 | 1/46 | 0/16 |
| Dry throatRespiratory, thoracic and mediastinal disorders | 1/45 | 0/46 | 0/16 |
| Age, Categorical(Participants) | ST-246 400 mg | ST-246 600 mg | Placebo | Total |
|---|---|---|---|---|
| <=18 years | 2 | 0 | 0 | 2 |
| Between 18 and 65 years | 41 | 40 | 13 | 94 |
| >=65 years | 2 | 6 | 3 | 11 |
| Age, Continuous(years) | ST-246 400 mg | ST-246 600 mg | Placebo | Total |
|---|---|---|---|---|
| Mean | 41.3 ± 15.22 | 43.7 ± 15.81 | 42.5 ± 17.03 | 42.5 ± 15.64 |
| Sex: Female, Male(Participants) | ST-246 400 mg | ST-246 600 mg | Placebo | Total |
|---|---|---|---|---|
| Female | 27 | 22 | 9 | 58 |
| Male | 18 | 24 | 7 | 49 |
| Region of Enrollment(participants) | ST-246 400 mg | ST-246 600 mg | Placebo | Total |
|---|---|---|---|---|
| United States | 45 | 46 | 16 | 107 |
This study is completed, as verified in Sep 2010. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Tecovirimat
SIGA Technologies