Pfizer Announces Top-Line Results of ABRYSVO for RSV in Immunocompromised Adults

Pfizer Inc. announced positive top-line safety and immunogenicity results from substudy B of the ongoing pivotal Phase 3 clinical trial ( NCT05842967 ) MONeT (RSV I Mmunizati ONStudy for Adul Ts at Higher Risk of Severe Illness), evaluating two doses of ABRYSVO vaccine in immunocompromised adults aged 18 and older at risk of developing severe respiratory syncytial virus (RSV)-associated lower respiratory tract disease (LRTD).

Adults with immunocompromising conditions have an increased risk of developing RSV-LRTD. Substudy B of the MONeT trial was conducted to assess the safety and immunogenicity of two doses of ABRYSVO, administered one month apart, in four groups of immunocompromised adults: those with non-small cell lung cancer, those on hemodialysis due to end-stage renal disease, those with autoimmune inflammatory disorder receiving active immunomodulator therapy, and solid organ transplant recipients. Of the 203 adults enrolled in the substudy, approximately half were between the ages of 18 to 59, and approximately half were 60 years or older.

ABRYSVO was well-tolerated during the trial, showing a safety profile consistent with findings from other studies of the vaccine. While the company evaluated two doses, a single 120 µg dose of ABRYSVO generated a strong neutralizing response against both subtypes of RSV, RSV-A and RSV-B, across all cohorts and age groups in the study. Pfizer plans to share these findings at an upcoming scientific conference and publish them in a peer-reviewed scientific journal, as well as submit these data to the regulatory agencies for review.

“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 Annaliesa Anderson, Ph.D., Senior Vice President and Chief Scientific Officer, Vaccine Research and Development, Pfizer. “We are encouraged by the positive top-line data from this study, which provide important evidence that ABRYSVO has the potential to address a significant unmet need in this vulnerable population.”

These most recent data in immunocompromised adults build on the body of evidence supporting the profile of ABRYSVO in high-risk adults. In June of 2024 at the meeting of the Advisory Committee on Immunization Practices ( ACIP ), Pfizer presented results from a cohort of adults aged 18-59 with certain chronic medical conditions. In the double-blinded study, 681 adults aged 18 to 59 with chronic conditions were randomized 2:1 to receive a single dose of ABRYSVO or placebo. Participants demonstrated RSV-A and RSV-B subgroup neutralizing responses non-inferior to the response seen in the Phase 3 (NCT05035212) RENOIR study of ABRYSVO, which previously demonstrated ABRYSVO’s efficacy in a population of adults aged 60 or older. These results support previous data presented at the ACIP showing high ABRYSVO clinical effectiveness against lower respiratory tract disease among a population of adults age 60 years and older that included a substantial proportion of immunocompromised persons.