Moderna's mRNA-based vaccine, mResvia (mRNA-1345), has received FDA approval for the prevention of lower respiratory tract disease (LRTD) caused by respiratory syncytial virus (RSV) in adults aged 60 years and older. This approval marks Moderna's second commercial product and positions it to compete with existing RSV vaccines from GSK (Arexvy) and Pfizer (Abrysvo).
The FDA's decision was based on data from the phase 2/3 ConquerRSV trial, which enrolled over 37,000 adults aged 60 and older. The trial demonstrated that mResvia was 78.7% effective in preventing RSV-LRTD with two or more symptoms at a median follow-up of 3.7 months. However, efficacy decreased to 62.5% at 8.6 months. These findings were initially published in the New England Journal of Medicine.
The prescribing information for mResvia indicates a slightly lower efficacy than initially highlighted, which led to a minor dip in Moderna's stock price upon the announcement, according to William Blair analysts. Despite this, mResvia's efficacy is considered competitive, falling between Arexvy and Abrysvo, although cross-trial comparisons should be interpreted cautiously due to differences in study design.
Clinical Efficacy and Safety Profile
The ConquerRSV trial was divided into two parts: Part A assessed safety and tolerability after a single dose compared to placebo over 12 months, while Part B evaluated the safety, tolerability, and immunogenicity of a booster dose at 24 months. A supplementary analysis showed sustained vaccine efficacy of 63.3% for RSV-LRTD with two symptoms, 74.6% for two or more symptoms including shortness of breath, and 63% for three or more symptoms over a median follow-up of 8.6 months.
The most commonly reported adverse events were injection site pain, fatigue, headache, myalgia, and arthralgia. Notably, no cases of Guillain-Barré syndrome (GBS), a rare side effect observed with both GSK and Pfizer's RSV vaccines, were reported in the mResvia trial.
Market Dynamics and Future Prospects
Following FDA approval, the CDC's Advisory Committee on Immunization Practices (ACIP) recommended mResvia for adults aged 75 and older and for those aged 60 to 74 at increased risk of severe RSV disease. This recommendation is crucial for the vaccine's uptake and integration into routine immunization schedules.
Currently, GSK's Arexvy leads the market with approximately $1.6 billion in sales last year, followed by Pfizer's Abrysvo at $890 million, which is also approved for maternal use to prevent RSV in newborns and infants. William Blair estimates that mResvia could capture around 27% of the US market, potentially generating $1.5 billion in revenue by 2033.
Ongoing Research and Future Studies
Clinical trials are ongoing to evaluate the effects of mResvia in other age groups, including a phase 3 study focused on high-risk individuals aged 18 to 60 years and individuals younger than 18 years who have received a solid organ transplant. These studies aim to broaden the vaccine's applicability and address unmet needs in vulnerable populations.
While mResvia offers the convenience of a prefilled syringe and lacks reported GBS risk, it faces challenges such as a shorter shelf-life and the need for extremely cold storage. Furthermore, delayed ACIP recommendations for adults aged 50 to 59 could impact overall RSV vaccine sales.
Despite these challenges, mResvia holds promise for reducing morbidity, mortality, and hospital burden associated with RSV infection, particularly among older adults and individuals with underlying health conditions.
