GSK's mRNA Flu Vaccine Succeeds Against B Strains in Phase 2 Trial

GSK has made significant progress in its development of an mRNA flu vaccine, particularly in addressing the historically challenging B strains of influenza. After an initial setback, the British pharmaceutical giant has returned with a reformulated candidate that has shown promising results in older adults. This marks a noteworthy advancement for the company, especially in the competitive landscape of mRNA flu vaccine development.

In a previous phase 2 trial conducted in April, GSK demonstrated that its vaccine candidate could outperform licensed flu vaccines in generating an immune response against influenza A strains. However, the vaccine initially failed to achieve similar success against B strains. CureVac, which collaborated with GSK on the vaccine's development, announced that they would focus on "targeted optimizations" to enhance the vaccine's efficacy against B strains. These efforts appear to have paid off, as newly released phase 2 data indicate that the reformulated vaccine successfully elicited immune responses to both A and B strains in younger and older adults.

The recent study involved 500 healthy adults, with 250 participants aged 18 to 64 years and another 250 aged 65 to 85 years. Various mRNA formulations and dose levels of the vaccine were tested against age-appropriate, approved flu shots. The results demonstrated that GSK’s candidate induced acceptable immune responses for both A and B strains. Interim data also suggest that the different formulations had an "acceptable safety and reactogenicity profile," according to GSK.

In July, GSK acquired full rights to CureVac's flu and COVID mRNA candidates for $430 million. The latest phase 2 results reaffirm the strength of the mRNA platform in producing strong antibody responses with an acceptable safety profile. GSK is now preparing to move its vaccine into phase 3 of development. Tony Wood, GSK’s Chief Scientific Officer, stated that this progress marks a significant step forward in their mRNA program. He emphasized that the ultimate goal is to develop a best-in-class vaccine to offer enhanced protection during the influenza season.

Despite the promising results, GSK has not yet set a timeline for when the vaccine will enter phase 3, according to a spokesperson. Updates are expected to be provided during the company's next quarterly earnings report. It’s worth noting that GSK is not alone in facing challenges with B strains. Competitors in the race to bring the first mRNA flu vaccine to market have also struggled with this issue.

Moderna is the only other company to have fully succeeded in this area, showing a year ago that its reformulated candidate induced higher antibody levels for major B strains compared to GSK’s approved flu vaccine, Fluarix, in a phase 3 trial. On the other hand, Sanofi faced significant setbacks with its mRNA flu vaccine candidate, leading executives to assert that the first generation of mRNA flu vaccines would not be effective.

Pfizer and BioNTech have managed to overcome the challenge of B strains in a phase 3 study but only in participants under 65 years old. Their combined COVID-flu mRNA vaccine failed to neutralize B strains in older adults. Like Pfizer, GSK also has plans to develop a COVID-flu combination vaccine, and the recent positive results could facilitate this endeavor.

In summary, GSK's reformulated mRNA flu vaccine has shown promising phase 2 results in both younger and older adults, particularly against the challenging B strains. This development marks a significant step forward for the company and sets the stage for upcoming phase 3 trials.