Pfizer announces positive results for RSV vaccine Abrysvo

Pfizer has revealed promising top-line results from a critical late-stage trial of its respiratory syncytial virus (RSV) vaccine, Abrysvo. This study focused on adults who are immunocompromised and thus at elevated risk for severe RSV-associated lower respiratory tract disease (LRTD).

According to the announcement made on August 12, Abrysvo demonstrated good tolerability in the substudy B segment of the pivotal Phase III MONeT study (NCT05842967). Substudy B looked at the effects of two 120 µg doses of Abrysvo. Pfizer reported that even a single 120 µg dose produced "strong neutralizing" antibodies against both RSV-A and RSV-B. The vaccine’s safety profile aligned with previous studies.

Dr. Annaliesa Anderson, Pfizer’s Senior Vice President and Chief Scientific Officer of Vaccine Research and Development, highlighted the heightened risk of severe RSV complications among immunocompromised adults, such as cancer patients or those with autoimmune disorders. She noted the absence of approved vaccines for individuals aged 18 to 59 in the U.S., emphasizing the importance of Abrysvo in filling this gap.

RSV is a highly contagious respiratory virus that often manifests as a common cold. However, it poses a significant risk for severe illness and complications in infants, older adults, and those with specific chronic conditions. Abrysvo, a subunit vaccine, employs an inactivated, recombinant RSV F protein antigen to trigger an immune response against the RSV prefusion conformation (pre-F), thereby providing immunity against RSV LRTD.

Abrysvo first received approval in May 2023 for preventing RSV-associated LRTD in adults aged 60 and older. Subsequently, in August 2023, it was approved for vaccinating pregnant women to protect their newborns.

The global pharmaceutical leader intends to present these positive results at an upcoming scientific conference. They also plan to publish the findings and submit the data to regulatory agencies for approval.

The MONeT study comprised two sub-studies targeting different patient cohorts. Substudy A, which was double-blind and randomized, compared a single dose of Abrysvo to a placebo in adults with certain chronic conditions. Meanwhile, substudy B was open-label and focused on evaluating the safety and efficacy of two doses of the vaccine, administered a month apart, in immunocompromised adults.

In April, Pfizer disclosed that the pivotal study achieved its co-primary endpoints of immunogenicity and safety. Vaccinated participants exhibited at least a four-fold increase in serum-neutralizing titers for the two RSV subtypes a month after vaccination.

Abrysvo’s financial prospects appear robust. According to GlobalData’s consensus forecasts, the vaccine is projected to generate global sales of $2.6 billion by 2030. In comparison, GSK’s RSV vaccine, Arexvy, is expected to achieve global sales of $3.9 billion in the same year.

Overall, the successful trial results bolster Abrysvo's potential as a critical vaccine for preventing severe RSV-related illnesses in vulnerable populations, particularly those who are immunocompromised. This development marks another significant step in Pfizer’s ongoing efforts to address unmet medical needs in infectious disease prevention.