GSK plc has announced positive headline results from its Phase II trial of an mRNA-based seasonal influenza vaccine, marking a significant step towards Phase III clinical trials. The study (NCT06431607) evaluated various mRNA formulations in both younger (18-64 years) and older (65-85 years) adults, assessing the vaccine's ability to improve immune responses against influenza A and B strains compared to the current standard of care.
The Phase II trial met its pre-defined success criteria in both younger and older adults. Interim data indicated an acceptable safety and reactogenicity profile across all mRNA formulations tested. The vaccine candidate demonstrated positive immune responses against both influenza A and B strains relative to the standard of care.
Tony Wood, GSK’s Chief Scientific Officer, stated, "This marks a significant advancement in our mRNA programme and these data support moving into late-stage development. Ultimately, our goal is to develop a new best-in-class vaccine to bring greater protection to people through the influenza season."
Study Design and Results
The Phase II study enrolled 250 healthy younger adults and 250 healthy older adults. It assessed the reactogenicity, safety, and immunogenicity of different dose levels of a modified, multivalent vaccine candidate encoding antigens matched to all three WHO-recommended influenza strains. The trial compared different dose levels of the vaccine candidate with an age-appropriate, licensed comparator vaccine.
The primary outcome measures included geometric mean titer (GMT) of antigen 1 antibody after 29 days; GMT increase of antigen 1 antibody from study day 1 to day 29; percentage of participants with antigen 1 seroconversion rate (SCR) from day 1 to day 29; and the percentage of participants with antigen 1 titer greater than or equal to the cut off value at day 1 and at day 29.
The results confirmed that the mRNA platform elicits strong overall antibody titers with an acceptable safety profile. This builds upon previous Phase II trial data and supports the progression of the GSK mRNA seasonal influenza vaccine program into late-stage clinical development.
GSK's Broader mRNA Strategy
GSK recently signed a licensing agreement with CureVac to assume full control of developing and manufacturing influenza and COVID-19 candidate vaccines. The company is also investing in AI/ML-based sequence optimization, nanoparticle design, and manufacturing to enhance its mRNA capabilities.
