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BNT166a

Phase 2

Mpox (Monkeypox) | Monoclonal antibody | Infectious Disease |BioNTech SE|Last Updated: Aug 11, 2026

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC

Total Trials1

Total Enrollment310

FDA Designations

No designations recorded

Clinical trial landscape

BNT166a · 2 trials · 4 indications

Phase 2 1Phase 1 1

Indication

NCT07379580A Randomized Clinical Trial Investigating the Safety, Reactogenicity, and Immunogenicity After Immunization With an mRNA-based Mpox Vaccine Candidate in AfricaMpox (Monkeypox)

RECRUITING310 Analytics

PHASE2RECRUITING

A Randomized Clinical Trial Investigating the Safety, Reactogenicity, and Immunogenicity After Immunization With an mRNA-based Mpox Vaccine Candidate in Africa

Mpox (Monkeypox)

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Study Endpoints

Primary Endpoints

Number (and percentage) of participants with at least one solicited local reaction (pain, erythema/redness, induration/swelling)

For up to 7 days following each dose

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

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)

For up to 7 days following each dose

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

Number (and percentage) of participants with at least one use of antipyretics/analgesics

For up to 7 days following each dose

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

Number (and percentage) of participants with at least one unsolicited adverse event (AE) (post-Dose 1)

From Dose 1 to 28 days post-Dose 1

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

Number (and percentage) of participants with at least one unsolicited AE (post-Dose 2)

From Dose 2 to 28 days post-Dose 2

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

Number (and percentage) of participants with at least one serious adverse event

From Dose 1 until the end of study, i.e., up to ~14 months

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

Number (and percentage) of participants with at least one AE of special interest

From Dose 1 until the end of study, i.e., up to ~14 months

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

Number (and percentage) of participants with at least one medically attended AE

From Dose 1 until the end of study, i.e., up to ~14 months

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

Number (and percentage) of participants with at least one AE leading to a participant's withdrawal from the study

From Dose 1 until the end of study, i.e., up to ~14 months

At each dose level of BNT166a in Orthopoxvirus-naïve (Cohort 1) and Orthopoxvirus-experienced (Cohort 2) adults.

SSA, SSB, and SSD - Proportion (%) of participants reporting solicited local reactions at the injection site (pain, erythema/redness, induration/swelling)

From Dose 1 through Day 7 post-Dose1 inclusive; and from Dose 2 through Day 7 post-Dose 2 inclusive

For each group

SSA, SSB, and SSD - Proportion (%) of participants reporting solicited systemic events (vomiting, diarrhea, headache, fatigue, myalgia, arthralgia, chills, and fever)

From Dose 1 through Day 7 post-Dose1 inclusive; and from Dose 2 through Day 7 post-Dose 2 inclusive

For each group

SSA, SSB, and SSD - Proportion (%) of participants with at least one unsolicited adverse event (AE) occurring from Dose 1 through Day 28 post-Dose 1 inclusive

From Dose 1 through Day 28 post-Dose 1 inclusive

For each group

SSA, SSB, and SSD - Proportion (%) of participants with at least one unsolicited AE occurring from Dose 2 through Day 28 post-Dose 2 inclusive

from Dose 2 through Day 28 post-Dose 2 inclusive

For each group

SSA, SSB, and SSD - Proportion (%) of participants with at least one serious adverse event (SAE) occurring from Dose 1 through Day 201 post-Dose 1 inclusive

From Dose 1 through Day 201 post-Dose 1 inclusive

For each group

SSA, SSB, and SSD - Proportion (%) of participants with at least one adverse event of special interest (AESI) occurring from Dose 1 through Day 201 post-Dose 1 inclusive

From Dose 1 through Day 201 post-Dose 1 inclusive

For each group

Secondary Endpoints

Geometric mean titers (GMT) of BNT166a antigen-specific (A35, B6, H3, and M1) binding antibody titers

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 1 month post-Dose 1 and 1 month post-Dose 2

GMT of MPXV-specific neutralizing antibody titers

At baseline, 1 month post-Dose 1, and 1 month post-Dose 2

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Study Design & Arms

AllocationRANDOMIZED

MaskingQUADRUPLE

ModelPARALLEL

PurposePREVENTION

Treatment Arms

Arm	Type	Description
Cohort 1 - BNT166a Dose Level (DL) 1 (Orthopoxvirus-naïve participants, aged 18-45 years)	EXPERIMENTAL	Two doses of investigational medicinal product (IMP).
Cohort 1 - BNT166a DL 2 (Orthopoxvirus-naïve participants, aged 18-45 years)	EXPERIMENTAL	Two doses of IMP.
Cohort 1 - Placebo (Orthopoxvirus-naïve participants, aged 18-45 years)	PLACEBO_COMPARATOR	0.9% sodium chloride solution. Two doses of IMP.
Cohort 2 - BNT166a DL 1 (Orthopoxvirus-experienced participants, aged 18-64 years)	EXPERIMENTAL	Two doses of IMP.
Cohort 2 - BNT166a DL 2 (Orthopoxvirus-experienced participants, aged 18-64 years)	EXPERIMENTAL	Two doses of IMP.
Cohort 2 - Placebo (Orthopoxvirus-experienced participants, aged 18-64 years)	PLACEBO_COMPARATOR	0.9% sodium chloride solution. Two doses of IMP.
SSA - BNT166a Dose Level (DL)1	EXPERIMENTAL	One dose level
SSA - BNT166a DL2	EXPERIMENTAL	One dose level
SSA - BNT166a DL3	EXPERIMENTAL	One dose level
SSB - BNT166a DL2	EXPERIMENTAL	One dose level
SSD - BNT166a	EXPERIMENTAL	One dose level based on SSA and SSB data

Interventions

Name	Type	Description
BNT166a	BIOLOGICAL	Intramuscular injection. Injections should be given in the deltoid muscle, using the same non-dominant arm for all IMP doses.
Placebo	OTHER	Intramuscular injection. Injections should be given in the deltoid muscle, using the same non-dominant arm for all IMP doses.

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Eligibility Criteria

Age Range18 Years to 64 Years

SexALL

Healthy VolunteersYes

Study Sites6

Key Inclusion Criteria (applicable to all participants unless otherwise specified): * Are male or female individuals ≥18 years of age at the time of giving informed consent: * Cohort 1: ≥18 to ≤45 years of age * Cohort 2: ≥18 to ≤64 years of age * Cohort 1: Participants must be Orthopoxvirus-n...

Countries:Democratic Republic of the CongoSouth AfricaUnited StatesUnited Kingdom

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Recent Changes (Last 90 Days)

LOWAug 11, 2026NCT07379580lastUpdatePostDate: changed

LOWAug 11, 2026NCT07379580lastUpdatePostDate: changed

LOWJul 14, 2026NCT07379580lastUpdatePostDate: changed

LOWJul 14, 2026NCT07379580lastUpdatePostDate: changed

LOWJul 9, 2026NCT07379580lastUpdatePostDate: changed

LOWJul 9, 2026NCT07379580lastUpdatePostDate: changed

Frequently asked questions about BNT166a

What is BNT166a used for?

BNT166a is an investigational mRNA-based vaccine candidate being developed for the prevention of Mpox (monkeypox) and related Orthopoxvirus infections. It is designed to elicit immune responses against the virus. The vaccine is currently in clinical development and is not yet approved by regulatory authorities.

Who makes BNT166a?

BNT166a is being developed by BioNTech SE, a biotechnology company traded on the Nasdaq under the ticker symbol BNTX. BioNTech is conducting clinical trials to evaluate the safety and immunogenicity of this vaccine candidate in healthy adult volunteers.

What phase is BNT166a in?

BNT166a is in clinical development, with a completed Phase 1 trial and an ongoing Phase 2 trial. The Phase 2 study is currently recruiting participants in Africa. BNT166a remains investigational and has not received FDA approval or any other regulatory approval.

What clinical trials is BNT166a in?

BNT166a has been studied in two clinical trials. NCT05988203 was a completed Phase 1 study in the United States and United Kingdom. NCT07379580 is an ongoing Phase 2 trial recruiting in the Democratic Republic of the Congo and South Africa, with an enrollment target of 310 participants.

How does BNT166a work?

BNT166a is an mRNA-based vaccine candidate. It works by delivering genetic instructions that encode for viral antigens, prompting the body's cells to produce these proteins and stimulate an immune response against the Mpox virus. This approach aims to generate protective immunity without using live virus.