Pfizer Inc has reported encouraging top-line results from its Phase 3 clinical trial of ABRYSVO. The trial demonstrates that Abrysvo is well-tolerated and elicits strong neutralizing responses against RSV in immunocompromised adults. A single 120 µg dose of Abrysvo effectively targets both RSV-A and RSV-B, offering substantial protection for this vulnerable population. Pfizer plans to present these findings at an upcoming scientific conference and publish them in a peer-reviewed journal.
The results are from substudy B of the MONeT trial (NCT05842967), which assessed the vaccine in 203 adults with conditions such as non-small cell lung cancer, end-stage renal disease on hemodialysis, autoimmune inflammatory disorders, and solid organ transplant recipients. While both one and two-dose regimens were evaluated, the single-dose regimen showed particularly promising results. The safety profile of Abrysvo was consistent with previous studies.
Additionally, Pfizer has secured US FDA approval for the ACT-O-VIAL® presentation of ABRYSVO, a dual-component vial system intended to streamline vaccine reconstitution and enhance storage efficiency. These findings build on earlier data presented to the Advisory Committee on Immunization Practices (ACIP) and reinforce Abrysvo’s use for older adults and maternal immunization to protect infants from RSV. Pfizer has also obtained various international approvals for ABRYSVO, including from the European Medicines Agency, Argentina’s ANMAT, the UK’s MHRA, Health Canada, and others.
Main Takeaways
- Pfizer's Phase 3 MONeT trial demonstrated that Abrysvo is well-tolerated and effective in generating strong neutralizing responses against RSV in immunocompromised adults.
- Pfizer has secured U.S. FDA approval for the ACT-O-VIAL presentation of Abrysvo, which enhances vaccine reconstitution and storage efficiency.
- Pfizer plans to present the trial results at a scientific conference, seek regulatory review for use in adults aged 18 to 59, and start trials for Abrysvo in children aged 2 to less than 18 years.
How Did We Get Here?
In August 2023, the FDA approved Pfizer’s bivalent RSV preF vaccine, marking the first maternal vaccine aimed at preventing lower respiratory tract disease caused by RSV in infants from birth to 6 months. Administered to pregnant women between 32 and 36 weeks of gestation, the unadjuvanted vaccine targets both RSV A and B strains.
The approval followed results from the MATISSE Phase 3 trial (NCT04424316), which demonstrated an 81.8% efficacy in preventing severe RSV-associated illness in infants. Conducted across 18 countries, the trial involved 7,358 participants and showed a significant reduction in severe RSV cases among vaccinated mothers’ infants compared to those receiving a placebo.
More recently, in April 2024, Pfizer’s Phase 3 MONeT trial of its Abrysvo vaccine in adults aged 18 to 59 at high risk for severe RSV-associated lower respiratory tract disease (LRTD) met its co-primary immunogenicity and safety endpoints. The trial included two substudies: one for adults with chronic conditions (RSV-A) and another for immunocompromised adults (RSV-B). Results indicated that Abrysvo produced neutralizing responses comparable to those observed in Pfizer’s earlier RENOIR study involving adults aged 60 and older. The vaccine showed a significant increase in serum neutralizing titers against RSV-A and RSV-B and was well-tolerated, with a safety profile consistent with previous studies.
About ABRYSVO
ABRYSVO is a bivalent vaccine designed to prevent lower respiratory tract disease caused by RSV in individuals aged 60 years and older and to protect infants through maternal immunization. RSV is a common and potentially severe respiratory virus that can lead to significant illness, especially in older adults and those with chronic health conditions.
Future direction for Pfizer will be to advance Abrysvo by sharing the positive MONeT trial results at a scientific conference and seeking regulatory review for immunocompromised adults aged 18 to 59. The company will also use its new ACT-O-VIAL presentation to improve vaccine access and is starting trials for Abrysvo in children aged 2 to less than 18 years. These steps aim to expand vaccine availability and impact across various high-risk groups.
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