A Study of mRNA-1345, an mRNA Vaccine Targeting Respiratory Syncytial Virus, in Children 2 to <18 Years of Age at High Risk of Respiratory Syncytial Virus

Study Overview
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Brief Summary
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The purpose of the study is to evaluate the safety, reactogenicity, and immunogenicity of mRNA-1345 in children aged 2 to <5 years of age and in children at high risk of respiratory syncytial virus (RSV) disease 5 to <18 years of age to inform the dose level selection for the next phase of development (Phase 3).

Official Title
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A Phase 2, Randomized, Observer-blind Study to Evaluate the Safety, Reactogenicity, and Immunogenicity of mRNA-1345, an mRNA Vaccine Targeting Respiratory Syncytial Virus, in Children 2 to <18 Years of Age at High Risk of Respiratory Syncytial Virus Disease

Conditions
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Respiratory Syncytial Virus

Intervention / Treatment
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* Biological: mRNA-1345
* Biological: Placebo


Participation Criteria
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Eligibility Criteria
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Key Inclusion Criteria: Cohort 1: 2 to <5 years of age, at the time the informed consent is signed. Healthy, or with stable chronic conditions increasing the risk of RSV disease, per the clinical judgment of the Investigator. Cohort 2: 5 to <18 years of age, at the time the informed consent is signed. Participants with stable chronic conditions increasing the risk of RSV disease. Female participants of child-bearing potential may be enrolled in the study, if the participant: 1) has a negative urine pregnancy test at Screening and on the day of injection (Day 1); 2) has practiced adequate contraception or has abstained from all activities that could lead to pregnancy for 28 days prior to Day 1; 3) has agreed to continue adequate contraception through 90 days following injection; and 4) is not currently breastfeeding. Key Exclusion Criteria: Acutely ill or febrile (temperature ≥38.0°Celsius [100.4°Fahrenheit]) within 72 hours prior to or at the Screening Visit or Day 1. History of a diagnosis or condition that, in the judgment of the Investigator, may affect study assessment or compromise participant safety. Has received or plans to receive any licensed or authorized vaccine ≤14 days prior to the study vaccine injection (Day 1) or plans to receive a licensed or authorized vaccine within 14 days after the study vaccine injection. Receipt of any prior systemic immunosuppressants or immune-modifying drugs. Short courses (<7 days) of oral corticosteroids are allowed if completed at least 3 months prior to enrollment. Receipt of RSV monoclonal antibodies within 6 months prior to enrollment in the study. Participated in an interventional clinical study within 28 days (6 months for a study assessing a product unlicensed in this age group) prior to the day of enrollment or plans to do so while enrolled in this study. Note: Other protocol-defined inclusion and exclusion criteria may apply.

Ages Eligible for Study
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Minimum Age: 2 Years
Maximum Age: 17 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Cohort 1 (2 to <5 Years of Age)<br>Participants 2 to <5 years of age will receive either a single intramuscular (IM) injection of mRNA-1345 or placebo on Day 1. | Biological: mRNA-1345<br>* Sterile liquid for injection<br>Biological: Placebo<br>* 0.9% sodium chloride (normal saline) injection<br>|
| Experimental: Cohort 2 (5 to <18 Years of Age)<br>Participants 5 to <18 years of age will receive either a single IM injection of mRNA-1345 or placebo on Day 1. | Biological: mRNA-1345<br>* Sterile liquid for injection<br>Biological: Placebo<br>* 0.9% sodium chloride (normal saline) injection<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Participants with Solicited Local and Systemic Adverse Reactions (ARs) |  | Up to 7 days postinjection | 
| Number of Participants with Unsolicited Adverse Events (AEs) |  | Up to 28 days postinjection | 
| Number of Participants With Medically Attended AEs (MAAEs) |  | Day 1 through end of study (EOS; Month 6) | 
| Number of Participants With Adverse Events of Special Interest (AESIs) |  | Day 1 through EOS (Month 6) | 
| Number of Participants With Serious Adverse Events (SAEs) |  | Day 1 through EOS (Month 6) | 
| Number of Participants With AEs Leading to Discontinuation |  | Day 1 through EOS (Month 6) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Geometric Mean Titer (GMT) of Serum RSV Neutralizing Antibody |  | Day 1, Day 29, and Month 6 | 
| Geometric Mean Concentration (GMC) of Serum RSV Prefusion F Binding Antibody |  | Day 1, Day 29, and Month 6 | 
| Geometric Mean Fold Rise (GMFR) of Postbaseline/Baseline Neutralizing Antibody Titers and Binding Antibody Concentrations |  | Baseline to Day 29 and Month 6 | 
| Number of Participants With Seroresponse in RSV Neutralizing Antibody | Seroresponse is defined as a postinjection titer >4-fold-rise if Baseline is >lower limit of quantification (LLOQ) or >4 × LLOQ if Baseline titer is <LLOQ in RSV neutralizing antibody titers at Day 29 and Month 6. | Baseline to Day 29 and Month 6 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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mRNA-1345, RSV vaccine, Viral Diseases, Messenger RNA, Moderna