Pfizer Reports Positive Topline Phase 3 Data for Bivalent RSV Vaccine in Older Adults

Pfizer announced on Thursday that the company’s bivalent respiratory syncytial virus (RSV) prefusion F vaccine candidate (RSVpreF) demonstrated 85.7% efficacy in older patients with severe RSV-associated lower respiratory tract illness (LRTI-RSV).

The positive top-line results, from the phase 3 RENOIR clinical trial, reflect the vaccines’ efficacy against the severe disease primary endpoint of LRTI-RSV defined by ≥3 symptoms.

The protection conferred by RSVpreF had been previously assessed in a preplanned interim analysis against less severe disease, LRTI-RSV defined by ≥2 symptoms, where it demonstrated efficacy of 66.7% (96.66% CI: 28.8%-85.8%). The interim data were obtained by an independent external Data Monitoring Committee, according to a Pfizer statement that also notes the vaccine was well tolerated and there were no safety concerns. Pfizer now plans submission of a Biologics License Application to the US Food and Drug Administration this fall.

“We are delighted that this first bivalent RSV vaccine candidate, RSVpreF, was observed to be efficacious in our clinical trial against this disease, which is associated with high levels of morbidity and mortality in older adults,” said Annaliesa Anderson, PhD, Pfizer senior vice president and chief scientific officer, vaccine research and development. “Scientists and researchers have worked to develop RSV vaccines with little success for over half a century.”

“Scientists and researchers have worked to develop RSV vaccines with little success for over half a century.”

RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease) is a global phase 3 trial to assess the efficacy, safety, and immunogenicity of a single RSVpreF dose of 120 µg in adults aged ≥ 60 years. There have been approximately 37 000 of participants enrolled to date and randomized in a 1:1 ratio to RSVpreF or placebo. In anticipation of the first RSV season in the southern hemisphere, enrollment up to approximately 40 000 participants continues.

The bivalent vaccine candidate is composed of equal amounts of recombinant RSVpreF from RSV A and B strains, said Pfizer.

“These findings are an important step in our effort to help protect against RSV disease, and we look forward to working with the FDA and other regulatory agencies to make this vaccine candidate available to help address the substantial burden of RSV disease in older adults," Anderson said.

Pfizer said it will present the results of the RENIOR interim analysis at a future medical meeting and will also submit them for peer review in a scientific journal.