FDA Advisory Committee Votes in Support of Safety, Efficacy of GSK Adult RSV Vaccine Candidate

The US Food and Drug Administration (FDA) Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted on March 1, 2023, that that the data supplied by biopharmaceutical company GSK support the safety and effectiveness of the company’s respiratory syncytial virus (RSV) older adult vaccine candidate for the prevention of lower respiratory tract disease (LRTD) caused by RSV in adults aged ≥60 years.

The Committee voted unanimously 12-0 on effectiveness and 10-2 on safety, according to a GSK press statement.

The VRBPAC vote is based on a compendium of data that includes results from the pivotal phase 3 AReSVi-006 (Adult Respiratory Syncytial Virus) clinical trial. That study, subsequently published in the New England Journal of Medicine, demonstrated overall vaccine efficacy of 82.6% against RSV-lower respiratory tract disease (LRTD) in adults aged ≥60 years, satisfying the trial’s primary endpoint, according to GSK.

A range of prespecified secondary endpoints for the trial also were consistently positive with efficacy of 94.1% in patients with severe RSV-LRTD, 94.6% in participants with comorbidities, and 93.8% in adults aged 70-79 years. Efficacy of the vaccine against RSV-LRTD was consistent across RSV A and B subtypes (84.6% and 80.9%, respectively), findings consistent with the significant neutralizing antibody response seen against both variants, according to the company.

“Today’s vote brings us an important step closer to delivering one of the world’s first vaccines for RSV, a respiratory virus that causes potentially debilitating disease and imposes a major burden on healthcare systems,” said Phil Dormitzer, GSK global head of R&D, in the statement. “Thousands of older adults in the US are impacted by RSV and those with underlying health conditions, like respiratory and heart diseases and diabetes, are at increased risk of severe complications.

“We’re delighted that the Advisory Committee recognised [sic] the strength of our vaccine’s data and its potential to make a positive public health impact with a unanimous vote on the effectiveness of the vaccine.”

Safety discussion

VRBPAC’s decision did not come without discussion regarding the potential for rare nervous system disorders related to the vaccine. During clinical trials there was 1 case of Guillain-Barre syndrome and 2 cases of acute disseminated encephalomyelitis (ADEM) diagnosed, according to details from the advisory committee meeting February 28-March 1, 2023.

Regarding the former, GSK has said data were not sufficient to confirm a diagnosis. The FDA, however, considers the case to be related to the vaccine. The 2 cases of ADEM were observed in a trial where the GSK influenza vaccine Fluarix Quadrivalent was coadministered with the RSV shot. At the meeting’s conclusion it was expected that post-marketing surveillance data would help inform adverse events and safety.

It should be noted that there were also 2 cases of Guillain-Barre syndrome diagnosed during clinical trials of the Pfizer RSV vaccine candidate which was also under review at the 2-day meeting. Marie Griffin, MD, MPH, professor of health policy and medicine at Vanderbilt University a VRBPAC member, said in an interview with CNBC that “the fact that such a rare disorder occurred in both companies’ trials is troubling.”

In November 2022, the FDA accepted the Biologics License Application (BLA) for GSK’s RSV older adult vaccine candidate under Priority Review and assigned a Prescription Drug User Fee Act action date of May 3, 2023.