Locked in a closely watched respiratory syncytial virus (RSV) vaccine competition, Pfizer aims to expand the reach of its offering Abrysvo.
Monday, Pfizer said Abrysvo elicited a strong response in adults of various ages with compromised immune systems.
A single dose of the vaccine generated strong neutralizing antibodies against both subtypes of RSV across all cohorts, Pfizer said, even though the phase 3 study, coded MONeT, tested Abrysvo in two doses given one month apart.
Based on the positive readout, Pfizer said it plans to submit the data to regulators for review and share the full details at an upcoming scientific conference.
“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.,” Annaliesa Anderson, Ph.D., Pfizer’s chief scientific officer for vaccine R&D, said in a statement.
Before the latest trial win, Abrysvo gained FDA approval as a single-dose injection to prevent lower respiratory tract disease caused by RSV in individuals 60 years of age and older and in infants via maternal vaccination.
The latest immune response findings came from 203 adults enrolled in four cohorts of substudy B of the MONeT trial—those with non-small cell lung cancer, end-stage kidney disease, autoimmune disease and solid organ transplant recipients. About half of the participants were younger than 60, for whom Abrysvo is not currently approved.
Pfizer previously shared results from substudy A of the trial, which tested the shot in 681 adults below the age of 60 with chronic conditions. Neutralizing antibody responses were found to be similar to those seen in the phase 3 RENOIR study, which enabled Abrysvo's original FDA go-ahead in adults age 60 and older.
Besides Abrysvo, GSK’s Arexvy is approved in adults age 60 and older as well as in those ages 50 to 59 at increased risk of severe illness. Moderna’s mRESVIA received its green light in the 60-and-above age group in May.
Despite the vaccines’ broad FDA labels, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) in June surprisingly only backed RSV immunization in adults age 75 and above and in high-risk people ages 60 to 74.
Following the restricted recommendation, GSK has trimmed its 2024 vaccines sales projection, whereas Pfizer CEO Albert Bourla, Ph.D., said during an investor call in July that the company remains confident in Abrysvo’s full-year performance.
Many healthcare providers and pharmacies prefer the simplicity of having one vaccine for both adult vaccinations and maternal vaccination, which only Abrysvo can offer, Pfizer’s chief U.S. commercial officer, Aamir Malik, said on the call. As for the limited ACIP policy, Malik said the guidance offers clarity and “strengthens the directive for those who are eligible for a vaccine.”
Previously, RSV vaccination was recommended for all adults ages 60 and older but only after consultation with a healthcare provider.
So far, for the 2024-25 RSV season for the vaccines, GSK said it remains the market leader based on existing contracts. Malik, without offering many specifics, said Pfizer has also strengthened its contracting position.
Moderna’s mRESVIA is currently viewed as the weakest RSV shot of the three. And GSK’s Arexvy looks unlikely to tap into the maternal vaccination market.
GSK and Pfizer are continually building their respective cases for their shots. In younger adults, Pfizer recently submitted applications for Abrysvo in adults ages 18 to 59 in both the U.S. and Europe. GSK recently started a phase 3b trial for Arexvy in adults ages 18 to 49 who are at increased risk of RSV disease, and a phase 2b conducted in lung and kidney transplant recipients age 50 and above is expected to read out this year.
GSK also has an extensive clinical program evaluating Arexvy co-administered with other vaccines, including for flu, pneumococcal disease and shingles.