GSK’s respiratory syncytial virus (RSV) vaccine has hit the mark in a phase 3 trial in older adults, teeing the company up to file for approval by the end of the year. But the data-devoid statement leaves unanswered the big question of how the vaccine will fare in a competitive, blockbuster market.
The top-line readout is positive for GSK, giving the company a boost after the setbacks to its maternal RSV vaccine program. At the interim analysis, the 25,000-subject clinical trial linked a single dose of GSK's adjuvanted RSVPreF3 OA investigational vaccine to statistically significant and clinically meaningful reductions in cases of lower respiratory tract disease caused by RSV in adults aged 60 years and older.
Exactly how significant the reduction was remains a mystery, with GSK holding off on sharing the results until a peer-reviewed publication and an upcoming scientific meeting. GSK has previously discussed what success would look like for the program.
Talking to investors on a quarterly results conference call in April, Hal Barron, M.D., GSK’s soon-to-depart chief scientific officer, said the company is “pretty confident” that an effect of 50% or more would be clinically meaningful. The wording of the top-line data release suggests GSK cleared that bar but leaves the question of whether it hit Barron’s yardstick for a “very good response”—70%—unanswered.
The level of competition for the RSV opportunity means the efficacy figure may be vital to GSK’s chances of seizing a significant slice of the blockbuster sales that are on offer. Johnson & Johnson, Moderna and Pfizer have rival vaccines in phase 3. A lot is resting on the RSV vaccine, with GSK citing the jab as a reason its R&D costs rose 7% in the first quarter.
While GSK is holding off on sharing any numbers, it has provided some details beyond the hit on the primary endpoint. The magnitude of effect was consistent across RSV A and B strains, key secondary endpoints and in people aged 70 years and above, according to GSK. The Big Pharma observed “no unexpected safety concerns.”
Armed with the phase 3 data, GSK plans to enter talks with regulators with a view to submitting filings for approval in the second half of the year. In parallel, GSK will continue to track patients in the phase 3 to evaluate an annual revaccination schedule and assess the protection provided by a single dose over multiple RSV seasons.