Pfizer has announced positive topline results from a pivotal late-stage study of its respiratory syncytial virus (RSV) vaccine, Abrysvo, in adults who are immunocompromised and at risk of developing severe RSV-associated lower respiratory tract disease (LRTD).

As per the 12 August press release, Abrysvo was found to be well tolerated in the substudy B portion of the pivotal Phase III MONeT study (NCT05842967). While substudy B evaluated two 120 µg dose doses of Abrysvo, Pfizer reported that a single 120 µg dose of the vaccine led to “strong neutralizing” responses against RSV-A and RSV-B. The safety profile of Abrysvo was consistent with that of previous studies.

“Immunocompromised adults, such as patients with cancer or autoimmune disorders, have a substantially increased risk of experiencing severe complications from RSV, yet there are currently no vaccines approved for those aged 18 to 59 in the U.S.,” said senior vice president and CSO, Vaccine Research and Development, Annaliesa Anderson, PhD.

RSV is a highly contagious respiratory virus that often presents as a common cold. However, infants, older adults, and individuals with certain underlying chronic conditions can face a higher risk for severe illness and complications. As a subunit vaccine delivering an inactivated, recombinant RSV F protein antigen, Abrysvo is designed to induce an immune response against RSV prefusion conformation (pre-F) and provide immunity against RSV LRTD.

Abrysvo was first approved in May 2023 for the prevention of RSV-associated LRTD in adults aged 60 years of older, and later for the vaccination of pregnant women to offer protection for their babies in August 2023.

MONeT was composed of two sub-studies evaluating two different cohorts of patients. The double-blind, randomised substudy A assessed a single dose of Abrysvo against placebo in adult participants with certain underlying chronic conditions. The open label substudy B evaluated two doses of the vaccine—administered one month apart—in adult participants who were immunocompromised.

In April, Pfizer shared that the pivotal study met its co-primary endpoints of immunogenicity and safety, reporting that vaccinated patients demonstrated a minimum of a four-fold increase in serum-neutralizing titers for the two subtypes of RSV one month after vaccination.

GlobalData’s consensus forecasts estimates that Abrysvo will generate global sales of $2.6bn in 2030. Comparatively, GSK’s RSV vaccine Arexvy is anticipated to generate global sales of $3.9bn in 2030.

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