FDA advisers endorsed the safety and efficacy of GSK’s respiratory syncytial virus (RSV) vaccine in older adults, setting up a final mad dash with Pfizer as both companies eye the regulatory finish line with their promising new vaccines.
The advisers spent the day hashing through the risks and benefits of the GSK shot. On the topic of risks, much of the discussion centered on a single case of Guillain-Barré syndrome and serious adverse events within six months of vaccination, which affected 4% of recipients.
For their part, FDA staffers said most of the serious side effects involved nervous system disorders, infections and cardiac disorders.
Ultimately, the majority of advisers on the FDA's Vaccines and Related Biological Products Advisory Committee said available data support an approval for GSK's program. The vote came a day after seven of the members supported the safety of Pfizer’s RSV vaccine and seven supported its efficacy.
Only three members supported both elements of Pfizer’s data package. That compared with 10 for GSK's application.
Still, not all advisers were sold on GSK’s data, with some expressing wariness of relying on postmarket data to uncover additional safety concerns.
“[W]hether or not postmarketing is the way to go, I am struggling with this question,” said Hana El Sahly, M.D. El Sahly voted against the safety profile of the vaccine.
Despite the concerns raised, GSK celebrated the vote. In a statement, global vaccine R&D head Phil Dormitzer, M.D., Ph.D., said the outcome marked “an important step closer to delivering one of the world’s first vaccines for RSV.”
In a phase 3 trial, GSK’s vaccine was found to be 82.6% effective against RSV-confirmed lower respiratory tract disease. Against severe disease, which was marked by at least three or more signs of lower respiratory tract disease, the efficacy jumped to 94.1%. The majority of advisers spoke confidently of the vaccine candidate's efficacy.
“I think they’ve met the bar more than adequately,” said James Hildreth Sr., M.D., Ph.D.
But Amanda Cohn, M.D., chief medical officer for the National Center for Immunizations and Respiratory Diseases at the Centers for Disease Control and Prevention, said the lack of severe disease cases accrued gave her pause when considering the effectiveness in the context of the identified safety signals. Only 18 cases of severe disease were reported among all trial participants. Other advisers also noted that they would’ve appreciated more long-term data.
GSK noted that the company is following trial participants through three RSV seasons, with a re-randomization set to occur before the second season to test the durability and long-term safety of one shot of the vaccine.
The advisers’ endorsement is the latest in a neck-and-neck race between Pfizer and GSK to launch the first RSV vaccine in the world. Pfizer has been granted priority review of its vaccine, and an FDA decision is set for May. GSK has an FDA decision date of May 3. Running third in the race to vaccinate older adults is Moderna, which has yet to apply for approval.