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 Inc. (NYSE:PFE) today announced that its respiratory syncytial virus (RSV) vaccine candidate, PF-06928316 or RSVpreF, received Breakthrough Therapy Designation from the US Food and Drug Administration (FDA) for prevention of RSV-associated lower respiratory tract illness in infants from birth up to six months of age by active immunization of pregnant women.

The FDA decision is informed by the results of the Phase 2b proof-of-concept study of RSVpreF (NCT04032093), a global, double-blinded, placebo-controlled study that assessed the safety and immunogenicity of RSVpreF in healthy pregnant women ages 18 through 49 years old, who were vaccinated between 28- and 36-weeks gestation, and their infants. Pfizer will publish outcomes from this clinical trial at a future date.

“Today’s decision is a pivotal next step in our path towards potential regulatory approval for our maternal RSV vaccine candidate and is an important milestone in our efforts to help address the detrimental impact RSV disease has on infants,” said Kathrin U. Jansen, Ph.D., Senior Vice President and Head of Vaccine Research & Development at Pfizer Inc. “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.”

The FDA’s Breakthrough Therapy Designation is designed to expedite the development and review of drugs and vaccines that are intended to treat or prevent serious conditions and preliminary clinical evidence indicates that the drug or vaccine may demonstrate substantial improvement over available therapy on a clinically significant endpoint(s).1 This decision follows the FDA’s November 2018 decision to grant Fast Track status to RSVpreF. Fast Track status is a process designed to facilitate the development and expedite the review of new drugs and vaccines intended to treat or prevent serious conditions and address a medical need.2

Burden of RSV
RSV is a contagious virus and a common cause of respiratory illness.3 The virus can affect the lungs and breathing passages of an infected individual and can be potentially life-threatening for young infants, the immunocompromised, and older adults.4,5,6,7 In the United States alone, approximately 2.1 million outpatient visits and 58,000 hospitalizations occur each year among children younger than five years old.8,9 For older adults in the U.S., RSV infections account for approximately 177,000 hospitalizations and 14,000 deaths each year.10 There is no vaccine to prevent RSV, and the medical community is limited to offering only supportive care for those with the illness.

About RSVpreF
Pfizer’s investigational RSV vaccine candidate builds on foundational basic science discoveries including those made at the National Institutes of Health (NIH), which detailed the crystal structure of a key form of the viral fusion protein (F) that RSV uses to attack human cells, prefusion F. The NIH research showed that antibodies specific to the prefusion form were highly effective at blocking virus infection, suggesting a prefusion F-based vaccine may confer optimal protection against RSV. After this important discovery, Pfizer tested numerous versions of the viral protein, and identified those that elicited a strong anti-viral immune response in pre-clinical evaluation. The vaccine candidate is composed of two preF proteins selected to optimize protection against RSV A and B and is currently being evaluated in ongoing late-stage human trials.

In April 2020, positive top-line results were achieved for a Phase 2b proof-of-concept study of RSVpreF, which evaluated the safety, tolerability and immunogenicity of RSVpreF in vaccinated pregnant women ages 18 through 49 and their infants. Pfizer will publish outcomes from this clinical trial at a future date.

In June 2020, Pfizer announced the initiation of a multicenter, international Phase 3 clinical trial (NCT04424316) evaluating the efficacy, immunogenicity and safety of RSVpreF when administered to pregnant women to help protect their babies from the disease after they are born. This study remains ongoing, but Pfizer expects the trial to readout in the first half of 2022 (1H22) and will seek to present and publish the results of MATISSE (MATernal Immunization Study for Safety and Efficacy) at a later date.

In September 2021, Pfizer announced the initiation of RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease), a Phase 3 clinical trial (NCT05035212) evaluating the efficacy, immunogenicity and safety of a single dose of RSVpreF, in adults ages 60 years or older. Top-line data for the trial are expected in 1H22, and Pfizer will seek to present and publish the results at a later date. The initiation of this trial followed the company’s July 2021 update on a Phase 2a study evaluating the safety, immunogenicity and efficacy of RSVpreF in a virus challenge model in healthy adults 18 to 50 years of age. The results of the study supported proceeding to Phase 3.

About Pfizer: Breakthroughs That Change Patients’ Lives
At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world’s premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For more than 170 years, we have worked to make a difference for all who rely on us.

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