A Phase 1/2 interventional study of mRNA-1769 and Placebo in Smallpox and Mpox, sponsored by ModernaTX, Inc.. Completed at 12 sites in United Kingdom. Open to participants aged 18 Years to 49 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-07-16.
Sponsored by ModernaTX, Inc. (part of Moderna, Inc.) · Phase 1/2, Interventional, and Prevention
The goal of this study is to assess the safety, tolerability and immunogenicity of mRNA-1769 in healthy adult participants.
73 studies on the registry are indexed under Smallpox; 5 are open to participants now.
This study's enrollment of 351 is above the median of 150 across 61 interventional studies indexed under Smallpox.
Browse Smallpox studies →ModernaTX, Inc. is the lead sponsor of 119 studies on the registry; 18 are open to participants now.
Of its 64 completed or terminated interventional studies of FDA-regulated products, 35 (55%) 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.
Exclusion Criteria:
Note: Other inclusion and exclusion criteria may 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.
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.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and 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.
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.
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.
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.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
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.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
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.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and 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.
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.
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.
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.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
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.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive intramuscular (IM) injection of mRNA-1769 at Dose A on Day 1 and Day 29.
Biological: mRNA-1769
Participants will receive IM injection of mRNA-1769 at Dose B on Day 1 and Day 29.
Biological: mRNA-1769
Participants will receive IM injection of mRNA-1769 at Dose C on Day 1 and Day 29.
Biological: mRNA-1769
Participants will receive IM injection of placebo matched to mRNA-1769 on Day 1 and Day 29.
Other: Placebo
Sterile liquid for injection
0.9% sodium chloride injection (normal saline)
Number of Solicited Local and Systemic Reactogenicity Adverse Reactions (ARs) Through 7 Days After Each Investigational Medicinal Product (IMP)
Time frame: Up to Day 35
Number of Unsolicited Adverse Events (AEs) Through 7 Days After Each IMP
Time frame: Up to Day 57
Number of Participants with Medically-Attended AEs (MAAEs)
Time frame: Day 1 up to Day 395
Number of Participants with Adverse Events of Special Interest (AESIs)
Time frame: Day 1 up to Day 395
Number of Participants with Serious Adverse Events (SAEs)
Time frame: Day 1 up to Day 395
Number of Participants with AEs Leading to Study and/or Treatment Discontinuation
Time frame: Day 1 up to Day 395
Geometric Mean Titer (GMT) of Neutralising Antibody (nAb) against Mpox Virus (MPXV) by Plaque reduction neutralisation test (PRNT)
Time frame: Days 1 and 43
Percentage of Participants With Seroconversion Based on Neutralising Antibody Responses Against MPXV
Time frame: Days 1 and 43
Geometric Mean Concentration of Binding Antibodies (bAbs) Against MPXV Antigens by Meso Scale Discovery (MSD) Assay
Time frame: Days 1, 29, 43, and 57
Percentage of Participants With Seroconversion Based on Binding Antibodies (bAb) Responses against MPXV
Time frame: Days 1, 29, 43, and 57
Geometric Mean Titer of Neutralising Antibody Against Vaccinia Virus (VACV) by Plaque Reduction Neutralisation Test (PRNT)
Time frame: Days 1 and 43
Percentage of Participants With Seroconversion Based on Neutralising Antibody Responses Against Vaccinia Virus
Time frame: Days 1 and 43
Geometric Mean Concentration of Binding Antibodies Against Vaccinia Virus Antigens by Meso Scale Discovery Assay
Time frame: Days 1, 29, 43, and 57
Percentage of Participants With Seroconversion Based on Binding Antibodies Responses Against Vaccinia Virus
Time frame: Days 1, 29, 43, and 57
Ran from Aug 2023 to primary completion in Jul 2025, 22 months.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Jul 2025. You cannot join it, but the record below documents what was studied.
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