With FDA decision penciled in for May, GSK powers ahead in RSV race with Pfizer

The last few weeks have seen GSK and Pfizer locked in a neck-and-neck race to see which company can get their respiratory syncytial virus (RSV) vaccine to market first. Now, it looks like the British Big Pharma may have the edge in the U.S., securing priority review status from the FDA and an estimated decision date of May 3.

The company backed up its approval application with data from the AReSVi-006 phase 3 trial, which showed high overall vaccine efficacy against RSV lower respiratory tract disease in adults aged 60 years and older. The study of 25,000 people linked a single dose of the vaccine candidate to overall efficacy of 82.6%.

“The world has been waiting more than 50 years for an RSV vaccine, so this is a very significant scientific achievement,” GSK CEO Emma Walmsley said on a third-quarter earnings call this morning.

GSK’s regulatory announcement this morning comes just a day after Pfizer revealed that a trial of its RSV candidate has been halted early for efficacy. Unlike GSK’s vaccine, the Pfizer shot in question is targeting pregnant women, opening up a potentially different market. GSK halted enrollment in studies of its own maternal RSV vaccine candidate back in February—although that was due to a concerning safety signal in the trial. 

When asked on the earnings call whether GSK expects to beat Pfizer in the RSV race, Walmsley said the company is “incredibly confident in the profile” of the shot.

“Over 90% of the hospitalization burden in the market is for those that carry comorbidities, and that's where we've got this really high efficacy and lots of consistent data across the different profiles,” the CEO said. “So [we're] feeling ambitious for that one.”

It’s a crowded field for RSV prospects, with AstraZeneca and Sanofi developing a long-acting antibody that is administered to infants. In a phase 3 trial, the Big Pharma partners linked the vaccine, called nirsevimab, to 74.5% efficacy against medically attended RSV-associated lower respiratory tract infection.

When asked on an earnings call yesterday how Pfizer’s candidate could stack up to AstraZeneca and Sanofi’s RSV antibody for infants, Angela Hwang, Pfizer’s chief commercial officer and president of its global biopharmaceuticals business, pointed out Pfizer is the only company that has both an adult vaccine as well as the maternal vaccine in development.