Pfizer starts Phase 1/2 study of RSV vaccine candidate in healthy adult volunteers

Pfizer Inc. today announced that it has started a Phase 1/2 trial of its respiratory syncytial virus (RSV) vaccine candidate in healthy adult volunteers. RSV is a common respiratory virus that affects the lungs and airways, with significant impact on young children and older adults. The highest risk of severe outcome from RSV occurs in the first months of life.   "A successful RSV vaccine has been an elusive goal for the global health community for decades, but recent scientific achievements have prepared the field to potentially tackle this important pathogen," said Kathrin Jansen, Ph.D., senior vice president and head of Vaccine Research and Development at Pfizer Inc. "By pursuing a vaccine candidate to help protect both infants and older adults, we hope to make an impact for those most at risk for RSV disease."

Currently available prophylactic treatments for RSV are limited for use in high risk young children and infants, including very premature infants. If successful, Pfizer's investigational RSV vaccine could help protect young infants through the immunity created following vaccination of pregnant women. The maternal vaccine candidate is intended to raise RSV neutralizing antibody levels in pregnant women who then pass these protective antibodies to their unborn child and provide immunity during the early months of an infant's life. Pfizer is also advancing a maternal vaccine candidate against Group B streptococcus (GBS), currently in Phase 1/2 trials.

"RSV is the most frequent cause of serious respiratory tract infection in infants and young children, and also significantly impacts older adults and those with a compromised immune system," said Edward E. Walsh, M.D., Principal Investigator, Professor of Medicine at the University of Rochester, and Head of Infectious Diseases at the Rochester General Hospital in New York. "There is an urgent global need to develop a safe and effective vaccine as a preventative option to reduce the incidence and severity of this infection in these populations."

For older adults, RSV is the second leading cause of moderate to severe respiratory illness, following influenza. The risk of serious infection increases with age and for those with chronic heart or lung disease or a weakened immune system. There is no specific treatment for RSV and currently no licensed vaccine to prevent the disease^.

Clinical Development Program

The trial is designed as a Phase 1/2 randomized, placebo-controlled, observer-blind, dose-ranging study with two age groups enrolled in parallel to support both the maternal and older adult indications.

One age group includes males and females 18-49 years of age; the other includes males and females 50-85 years of age. The study's primary endpoints are safety and tolerability, and its secondary endpoint is immunogenicity.

Pfizer's 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 viral protein that RSV uses to attack human cells. They showed that the antibodies that protect humans from RSV target one form of this viral protein. Applying insights from this important work, Pfizer engineered and tested numerous candidates and identified those that elicited a strong and stable immune response in pre-clinical evaluation, which led to the vaccine candidate which Pfizer is evaluating in human trials.

Global Burden of RSV

Globally, there are an estimated 33 million cases of RSV annually in children less than 5 years of age, with about 3 million hospitalized and up to approximately 120,000 dying each year from complications associated with the infection. About half of the pediatric hospitalizations and deaths occur in infants less than 6 months of age.

More than 90% of all RSV-associated deaths occur in low- and middle-income countries (LMIC); the World Health Organization has indicated that the development of an RSV vaccine is a high priority.

It is estimated that in the United States approximately 177,000 older adults are hospitalized annually because of RSV.