With respiratory virus season approaching, GSK is preparing to begin a Phase 3 clinical trial evaluating its experimental messenger RNA vaccine for seasonal influenza.
The vaccine maker revealed the plans for the pivotal study after reporting Phase 2 results showing its shot led to higher immune responses against all influenza strains compared to currently available vaccines. These results in both younger and older adults were presented Tuesday at the OPTIONS XIII Conference for the Control of Influenza in Washington, D.C.
Currently available flu vaccines spark an immune response to hemagglutinin (HA), a protein on the surface of the pathogen that helps it bind to a cell. GSK said growing evidence suggests targeting both HA and a second protein called neuraminidase (NA) could improve on protection, illness severity, and virus transmission. GSK’s seasonal vaccine is a multivalent candidate that addresses both HA and NA. In addition to the role of NA in seasonal flu transmission, GSK said previous studies highlighted the need to improve the ability to prompt an immune response to HA protein from the influenza B strain.
The Phase 2 test in 971 adults assessed two similar mRNA vaccines: FLUm3HA.b-3NA was designed to encode an optimized B-strain HA while FLUm3HA-3NA encodes non-optimized B/HA. According to GSK, both vaccines demonstrated robust immune responses to HA and NA from influenza A and B strains, results that were observed in both younger and older adults.
GSK described its vaccine’s side effect profile and safety as acceptable. Based on the Phase 2 results, GSK has selected the optimized B-strain HA vaccine candidate for Phase 3 testing. This pivotal trial is expected to begin later this month.
“These promising data support the potential to better protect people from flu with a vaccine designed to target both HA and NA,” Sanjay Gurunathan, GSK Head of Vaccines and Infectious Diseases Research and Development, said in a prepared statement. “With one billion flu cases worldwide each year and up to 650,000 deaths there is a need for next generation vaccine approaches.”
The first mRNA vaccine for seasonal flu is on its way to the market following the FDA’s August approval of Moderna’s mFLUSIVA. Like the currently available flu vaccines, Moderna’s shot addresses only the HA protein.
GSK’s mRNA vaccine candidates were acquired from former partner CureVac in 2024 for €400 million (about $431.4 million) up front. With that deal, CureVac pivoted away from infectious disease vaccines and turned its focus to cancer vaccines. CureVac is now a subsidiary of BioNTech following a $1.25 billion all-stock acquisition last year.
