GSK mRNA Flu Vaccine Candidate Delivers Favorable Topline Phase 2 Findings, Ready for Phase 3

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Positive topline phase 2 data reported by GSK today for its seasonal influenza mRNA vaccine support progression of the formulation to phase 3 clinical trials, according to a company news release.¹ The reformulated investigational vaccine, GSK4382276A, produced robust immune responses against both A and B influenza strains in both older and younger adults,¹ having fallen short earlier this year of besting licensed flu vaccines in prompting an immune response against strains of influenza B.² Moderna experienced a similar setback with its mRNA flu candidate in 2023 and also has rebounded.²

The phase II randomized, observer-blind, dose-finding study (NCT06431607) enrolled 250 healthy young adults aged 18 to 64 and 250 healthy older adults aged 65 to 85 years to assess reactogenicity, safety, and immunogenicity of different dose levels of the modified, multivalent GSK vaccine candidate.¹ Dose levels were evaluated in comparison to an age-appropriate licensed comparator vaccine in both age groups.¹ 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 29.³

The interim data also suggests acceptable safety and reactogenicity profiles for all the formulations evaluated, said GSK.¹

“This marks a significant advancement in our mRNA programme and these data support moving into late-stage development,” Tony Wood, PhD, GSK chief scientific officer said in the Sept 12 release.¹ “Ultimately, our goal is to develop a new best-in-class vaccine to bring greater protection to people through the influenza season.”¹

Of the 3 companies currently evaluating mRNA flu vaccine candidates, only Moderna has fully succeeded and last year reported that its influenza reformulation induced higher antibody levels for WHO-recommended influenza B strains compared with GSK’s licensed flu vaccine Fluarix in a phase 3 trial.² Sanofi leaders, after its mRNA flu vaccine candidate also ran into problems neutralizing influenza B strains last year, opined that the “first generation of mRNA vaccines for flu ‘will not win.’”² The Pfizer/BioNTech category entrant was successful against B strains in the company’s phase 3 program but only in study participants younger than 65 years.²

A timeline for the GSK vaccine’s entrance into phase 3 development had not been set as of the current announcement but additional updates will be included at the next quarterly earnings report, according to Fierce Biotech.²

References
1. GSK announces positive headline data from phase II seasonal influenza mRNA vaccine programme. News release. GSK. September 12, 2024. Accessed September 12, 2024. https://www.gsk.com/en-gb/media/press-releases/gsk-announces-positive-headline-data-from-phase-ii-seasonal-influenza-mrna-vaccine-programme/
2. Waldron J. GSK's mRNA flu vaccine finally overcomes tricky B strains in phase 2 trial. Fierce Biotech. September 12, 2024. https://www.fiercebiotech.com/biotech/gsks-mrna-flu-vaccine-finally-overcomes-tricky-b-strains-phase-2
3. Glaxo Smith Kline. A Study to Find the Dose and Assess the Immune Response and Safety of a Vaccine Against Influenza in Healthy Younger and Older Adults. Clinicaltrials.gov. NCT06431607. Updated July 3, 2024. Accessed September 12, 2024. https://clinicaltrials.gov/study/NCT06431607