FDA Awards Breakthrough Therapy Designation to Vaccine Candidate for RSV

The FDA has awarded Breakthrough Therapy Designation to Pfizer’s vaccine candidate PF-06928316 (RSVpreF) for the prevention of lower respiratory tract disease caused by respiratory syncytial virus (RSV) in individuals 60 years of age or older.

The designation is primarily based on positive results from a proof-of-concept phase 2a study analyzing the safety, immunogenicity, and efficacy of a single dose of 120µg RSVpreF in a human viral challenge model among healthy adults aged 18 to 50 years.

“Today’s decision is a significant step forward in our efforts to help protect vulnerable populations, particularly older adults, against certain potentially serious respiratory illnesses, including RSV,” Kathrin U. Jansen, PhD, senior vice president and head of Vaccine Research & Development at Pfizer Inc, said in a press release. “The clinical and economic burden of RSV represents a critical need, and we look forward to our ongoing dialogue with the FDA to accelerate the development of our RSV vaccine candidate.”

RSV is a contagious virus and a common cause of respiratory illness that can affect the breathing passages and lungs of infected individuals, and it is potentially life-threatening to infants.

According to Pfizer, RSVpreF is based on foundational basic science discoveries, such as findings from the National Institutes of Health (NIH), detailing the crystal structure of prefusion F, a vital form of the viral fusion protein (F) used by RSV to attack human cells. The NIH research found that antibodies specific to the prefusion form had high efficacy preventing viral infection. This indicates that a prefusion F-based vaccine may provide optimal protection against RSV, according to Pfizer.

Based on this discovery, the manufacturer evaluated several versions of the viral protein, identifying candidates that produced a strong antiviral immune response during pre-clinical evaluation. RSVpreF is made of 2 preF proteins selected to optimize protection against RSV A and B, according to Pfizer.

Earlier this month, the FDA granted breakthrough therapy designation to RSVpreF for the prevention of RSV-associated lower respiratory tract illness in infants from birth to 6 months by active immunization of pregnant women.The decision was based on results of the phase 2b proof-of-concept study of RSVpreF in a double-blinded, global, placebo-controlled study that assessed the immunogenicity and safety of the vaccine in healthy pregnant women aged 18 to 49 years and their infants.

In April 2020, positive top-line results were achieved for the study, and Pfizer will publish the outcomes from this clinical trial in the future.

In June 2020, Pfizer announced the initiation of an international, multicenter, phase 3 clinical trial evaluating the efficacy, immunogenicity, and safety of RSVpreF when administered to pregnant women to protect babies from the disease after they are born.

In September 2021, Pfizer initiated the still ongoing phase 3 RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease) clinical trial (NCT05035212), which clinical trial analyzed the efficacy, immunogenicity, and safety of a single dose of RSVpreF in adults 60 years of age and older. Top-line data for the trial are expected in the first half of 2022 with Pfizer presenting and publishing the results at a later date.

Reference

Pfizer Granted FDA Breakthrough Therapy Designation for Respiratory Syncytial Virus Vaccine Candidate for the Prevention of RSV in Older Adults. Pfizer. [news release]. March 24, 2022. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-granted-fda-breakthrough-therapy-designation-0