Phase 2
N=315
Dose-Finding Trial to Evaluate the Safety and Immunogenicity of Cytomegalovirus (CMV) Vaccine mRNA-1647 in Healthy Adults
Cytomegalovirus Infection
Bottom Line
View on ClinicalTrials.gov: NCT04232280 ↗Enrolled (actual)
315
Serious AEs
0.6%
Results posted
May 2026
Primary outcome: Primary: Number of Participants With Solicited Local and Systemic Adverse Reactions (ARs) — 33; 59; 40; 12 Participants
Study Design & Population
- Study type
- Interventional
- Phase
- Phase 2
- Interventions
- mRNA-1647 (Biological); Placebo (Other)
- Age
- Adult · 18+ yrs
- Sex
- All
- Sponsor
- ModernaTX, Inc.
- Primary completion
- Jan 2023
Outcome Measures
| Outcome | Result | p-value |
|---|---|---|
| PRIMARY Number of Participants With Solicited Local and Systemic Adverse Reactions (ARs) |
33; 59; 40; 12; 15; 33 | — |
| PRIMARY Number of Participants With Unsolicited Adverse Events (AEs) |
16; 31; 18; 21; 10; 16 | — |
| PRIMARY Number of Participants With Medically Attended Adverse Events (MAAEs) |
13; 24; 14; 19; 5; 11 | — |
| PRIMARY Number of Participants With Serious Adverse Events (SAEs) |
0; 1; 0; 0; 0; 1 | — |
| PRIMARY Geometric Mean Titer (GMT) of Serum Neutralizing Anti-CMV Antibodies Against Epithelial Cell Infection and Against Fibroblast Infection |
8.0; 8.0; 8.0; 8.0; 2250.0; 4571.9 | — |
| PRIMARY Geometric Mean Ratio (GMR) of Serum Neutralizing Anti-CMV Antibodies Against Epithelial Cell Infection and Against Fibroblast Infection |
140.06; 207.99; 475.24; 1.11; 12.03; 17.13 | — |
| PRIMARY Percentage of Participants With ≥2-Fold, 3-Fold, and 4-Fold Increases in Neutralizing Antibodies (nAb) Over Baseline Against Epithelial Cell Infection and Against Fibroblast Infection |
95.5; 93.8; 100; 2.0; 100.0; 93.9 | — |
| SECONDARY GMT of Anti-Glycoprotein B (gB)-Specific Immunoglobulin G (IgG) and Anti-Pentamer-specific IgG as Measured by Enzyme-Linked Immunosorbent Assay (ELISA) of Post-Baseline/Baseline Titers |
17.50; 18.20; 17.50; 17.50; 1146.61; 2631.32 | — |
| SECONDARY GMR of Anti-gB-specific IgG and Anti-Pentamer-specific IgG as Measured by ELISA of Post-Baseline/Baseline Titers |
1.088; 1.194; 1.123; 1.000; 1.850; 1.873 | — |
| SECONDARY GMT of Serum nAb Against Epithelial Cell Infection and Against Fibroblast Infection at Each Timepoint, in the CMV-Seropositive Group and in the CMV-Seronegative Group |
8.0; 4320.2; 1831.4; 63523.6; 1012.5; 49108.9 | — |
| SECONDARY GMR of Serum nAb Against Epithelial Cell Infection and Against Fibroblast Infection at Each Timepoint, in the CMV-Seropositive Group and in the CMV-Seronegative Group |
228.93; 14.76; 126.56; 13.63; 6207.16; 25.47 | — |
| SECONDARY Percentage of Participants With ≥2-Fold, 3-Fold, and 4-Fold Increases Over Baseline of Serum nAb Against Epithelial Cell Infection and Against Fibroblast Infection in the CMV-Seropositive and CMV-Seronegative Groups |
95.9; 93.4; 95.2; 88.5; 95.2; 85.2 | — |
| SECONDARY GMT of Antigen-Specific IgG (ELISA) at Each Timepoint in the CMV-Seropositive and CMV-Seronegative Groups |
17.79; 2230.11; 20.35; 4246.74; 20.43; 3710.50 | — |
| SECONDARY GMR of Antigen-Specific IgG (ELISA) at Each Timepoint in the CMV-Seropositive and CMV-Seronegative Groups |
1.143; 1.919; 1.144; 1.788; 22.533; 2.442 | — |
Summary
This clinical study will assess the safety and immunogenicity of 3 dose levels of mRNA-1647 cytomegalovirus vaccine in CMV-seronegative and CMV-seropositive healthy adults 18-40 years of age.
Eligibility Criteria
Inclusion Criteria
- Male or female 18-40 years of age (Part 1); Female 18-40 years of age (Part 2)
- Understands and agrees to comply with the trial procedures and provides written informed consent
- According to the assessment of the Investigator, is in good general health and is capable of complying with trial procedures
- Body mass index (BMI) 18-35 kilograms/meter (kg/m^2)
- Female participants must either be of non-childbearing potential or use acceptable methods of contraception from at least 28 days prior to the first vaccination and through 3 months following last vaccination and is not breastfeeding.
- Male participants must agree to practice adequate contraception from the time of the first vaccination and through 3 months after the last vaccination.
Exclusion Criteria
- Acutely ill or febrile on the day of the first vaccination
- Prior receipt of any CMV vaccine
- Abnormal screening safety laboratory test results
- Diagnosis or condition that, in the judgment of Investigator, is clinically unstable or may affect participant safety, assessment of safety endpoints, assessment of immune response, or adherence to trial procedures
- Has received or plans to receive a vaccine ≤28 days prior to the first vaccination or plans to receive a non-study vaccine within 28 days prior to or after any study vaccination, except for any licensed influenza vaccine which can be administered >14 days before or after any study vaccination. COVID-19 vaccines (regardless of manufacturer) may be administered >7 days but preferably >14 days before or after any study vaccination, with the intention of prioritizing COVID-19 vaccination over all other considerations.
- Prior receipt of chronic systemic immunosuppressants or immune-modifying drugs
- Receipt of intravenous immunoglobulins or plasma products within 3 months prior to the day of the first study vaccination
- Previous receipt of medications in lipid nanoparticle (LNP) formulation (Part 1 participants only)
- Has donated ≥450 milliliters (mL) of blood products within 28 days of the Screening visit
- Participated in an interventional clinical trial within 28 days prior to the day of enrollment
- Is an immediate family member or household member of trial personnel
Data sourced from ClinicalTrials.gov (NCT04232280). Outcome figures and adverse-event rates are extracted automatically from the registry's posted results and are provided for clinician reference, not as a substitute for the primary publication.