A Phase 2 interventional study of BNT166a and Placebo in Mpox (Monkeypox), Smallpox and Orthopoxvirus Infection, sponsored by BioNTech SE. Recruiting at 6 sites in 2 countries. Open to participants aged 18 Years to 64 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-11.
Sponsored by BioNTech SE · Phase 2, Interventional, and Prevention
This is a randomized, double-blind, placebo-controlled study which aims to assess the safety, reactogenicity, and immunogenicity after one and two doses of BNT166a or placebo in healthy participants.
This study will include the following cohorts:
All participants will receive two doses of BNT166a or placebo at least 28 days apart.
The planned study duration per participant is \~14 months.
72 studies on the registry are indexed under Mpox, Monkeypox; 30 are open to participants now.
This study's planned enrollment of 310 is close to the median of 305 across 36 interventional studies indexed under Mpox, Monkeypox.
Browse Mpox, Monkeypox studies →BioNTech SE is the lead sponsor of 76 studies on the registry; 25 are open to participants now.
Of its 33 completed or terminated interventional studies of FDA-regulated products, 26 (79%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria (applicable to all participants unless otherwise specified):
Are male or female individuals ≥18 years of age at the time of giving :
Key Exclusion Criteria (applicable to all participants unless otherwise specified):
NOTE: Other protocol defined Inclusion/Exclusion criteria apply.
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 reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
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.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
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.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
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.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
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.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
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.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Two doses of investigational medicinal product (IMP).
Biological: BNT166a
Two doses of IMP.
Biological: BNT166a
0.9% sodium chloride solution. Two doses of IMP.
Other: Placebo
Two doses of IMP.
Biological: BNT166a
Two doses of IMP.
Biological: BNT166a
0.9% sodium chloride solution. Two doses of IMP.
Other: Placebo
Intramuscular injection. Injections should be given in the deltoid muscle, using the same non-dominant arm for all IMP doses.
Intramuscular injection. Injections should be given in the deltoid muscle, using the same non-dominant arm for all IMP doses.
Number (and percentage) of participants with at least one solicited local reaction (pain, erythema/redness, induration/swelling)
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: For up to 7 days following each dose
Number (and percentage) of participants with at least one solicited systemic reaction (fever, headache, fatigue/tiredness, muscle pain/myalgia, joint pain/arthralgia, chills, diarrhea, vomiting)
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: For up to 7 days following each dose
Number (and percentage) of participants with at least one use of antipyretics/analgesics
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: For up to 7 days following each dose
Number (and percentage) of participants with at least one unsolicited adverse event (AE) (post-Dose 1)
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: From Dose 1 to 28 days post-Dose 1
Number (and percentage) of participants with at least one unsolicited AE (post-Dose 2)
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: From Dose 2 to 28 days post-Dose 2
Number (and percentage) of participants with at least one serious adverse event
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: From Dose 1 until the end of study, i.e., up to ~14 months
Number (and percentage) of participants with at least one AE of special interest
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: From Dose 1 until the end of study, i.e., up to ~14 months
Number (and percentage) of participants with at least one medically attended AE
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: From Dose 1 until the end of study, i.e., up to ~14 months
Number (and percentage) of participants with at least one AE leading to a participant's withdrawal from the study
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.
Time frame: From Dose 1 until the end of study, i.e., up to ~14 months
Geometric mean titers (GMT) of BNT166a antigen-specific (A35, B6, H3, and M1) binding antibody titers
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults, at the defined timepoints.
Time frame: At baseline, 1 month post-Dose 1, and 1 month post- Dose 2
Geometric mean fold rise (GMFR) of BNT166a antigen-specific (A35, B6, H3, and M1) binding antibody titers
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults. Ratio post-baseline/baseline at the defined timepoints.
Time frame: At 1 month post-Dose 1 and 1 month post-Dose 2
GMT of MPXV-specific neutralizing antibody titers
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults, at the defined timepoints.
Time frame: At baseline, 1 month post-Dose 1, and 1 month post-Dose 2
GMFR of MPXV-specific neutralizing antibody titers
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults. Ratio post-baseline/baseline at the defined timepoints.
Time frame: At 1 month post-Dose 1 and 1 month post-Dose 2
GMT of vaccinia virus (VACV)-specific neutralizing antibody titers
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults, at the defined timepoints.
Time frame: At baseline, 1 month post-Dose 1, and 1 month post-Dose 2
GMFR of VACV-specific neutralizing antibody titers
At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults. Ratio post-baseline/baseline at the defined timepoints.
Time frame: At 1 month post-Dose 1 and 1 month post-Dose 2
Plan to share: No
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