Pfizer’s RSV Vaccine Bags FDA Breakthrough Therapy Status

The US FDA has granted a Breakthrough Therapy Designation to Pfizer’s respiratory syncytial virus (RSV) vaccine candidate RSVpreF. RSVpreF is aimed at 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 Breakthrough Therapy Designation is designed to expedite the development and review of drugs and vaccines that demonstrate substantial improvement over available therapy on a clinically significant endpoint. This decision follows the FDA’s November 2018 decision to grant Fast Track status to RSVpreF. 

Related Article: The Next SuperStar Drug? AbbVie Places its Hope on Skyrizi and Rinvoq

Respiratory Syncytial Virus (RSV) a Global Cause of Concern

Respiratory syncytial virus (RSV) is estimated to cause 3.4 million hospitalizations and 95,000–150,000 deaths globally. RSV has two major antigenic groups of strains, A and B, and multiple genotypes within the two groups. 

Although the disease burden has made RSV a priority for vaccine development for over 50 years, a vaccine is still unavailable and the medical community is limited to offering only supportive care for those with the illness. 

The RSV genome is composed of 10 genes that encode for 11 proteins. All the RSV proteins have played a role in the design of one or more vaccines, though only two RSV proteins, F and G induce in-vitro neutralizing antibodies.

Related Article: EMA Accepts Application for AstraZeneca’s Anti-RSV Antibody Nirsevimab.

RSVpreF and Its Mode of Action

During an RSV infection, the F protein (responsible for viral fusion with cellular membranes) goes from the metastable pre-fusion (pre-F) to a stable post-fusion (post-F) state. Research has shown that most of the neutralizing antibodies in humans react against the pre- and not post-fusion form of protein F.

Pfizer’s RSVpreF is based on research which has shown that antibodies specific to the pre-fusion form were highly effective at blocking virus infection, suggesting a prefusion F-based vaccine may confer optimal protection against RSV.

The decision is being viewed as a pivotal next step in the path towards potential regulatory approval for the maternal RSV vaccine candidate, Kathrin U. Jansen, Ph.D., Senior Vice President and Head of Vaccine Research & Development at Pfizer Inc said “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.”

Author

Arvind C. Shekhar