FDA Grants Breakthrough Therapy Designation to Pfizer’s RSV Vaccine Candidate


The decision is informed by the results of a phase 2b proof-of-concept study that assessed the immunogenicity and safety of the drug in healthy pregnant women and their infants.

The FDA granted breakthrough therapy designation to PF-06928316 (RSVpreF, Pfizer), a respiratory syncytial virus (RSV) vaccine candidate, 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.

The pregnant women were vaccinated between 28 and 36 weeks of gestation.

“If approved by the FDA, this maternal immunization has the potential to be the first vaccine candidate to help protect infants in their vulnerable first months of life from disease caused by this highly contagious virus. We look forward to our ongoing dialogue with the FDA to accelerate the development of our maternal RSV vaccine candidate,” Kathrin Jansen, PhD, senior vice president and head of Vaccine Research & Development at Pfizer, said in a statement.

The vaccination uses a crystal structure of a key from of viral fusion protein (F) that RSV uses to attack human cells.

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.

The study is ongoing, but Pfizer expects the trial to readout in the first half of 2022 and will present and publish the results of the study at a later date.

Additionally, in September 2021, Pfizer announced the initiation of RENOIR, another phase 3 clinical trial, which will evaluate the efficacy, immunogenicity, and safety of a single dose of RSVpreF in individuals aged 60 years 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.

Breakthrough therapy designation expedites the development and review of drugs and vaccines that are intended to prevent or treat serious conditions.

It is based on preliminary clinical evidence that indicates whether the drug or vaccine may demonstrate substantial improvement over available therapy on clinically significant endpoints.

The FDA’s decision follows the previous decision to grant fast track status to RSVpreF in November 2018.

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.


Pfizer granted FDA breakthrough therapy designation for respiratory syncytial virus (RSV) vaccine candidate for the prevention of RSV in infants from birth up to six months of age by active immunization of pregnant women. Pfizer. News release. March 02, 2022. Accessed March 3, 2022. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-granted-fda-breakthrough-therapy-designation

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