GSK Announces Positive Phase I/II Results for Two RSV Vaccine Candidates Targeting Older Adults and Maternal Immunization; Phase III Trials Imminent

GlaxoSmithKline (GSK) announced today that its respiratory syncytial virus (RSV) candidate vaccines for maternal immunization (GSK3888550A) and for older adults (GSK3844766A) demonstrated favorable tolerability and high immunogenicity in Phase 1/2 clinical studies.

RSV is a leading cause of respiratory infections in infants and the elderly, including bronchiolitis (inflammation and congestion of the small airways or bronchioles in the lungs) and pneumonia (an inflammatory condition of the small air sacs or alveoli in the lungs). It is estimated to cause approximately 3 million hospitalizations among children under 5 years of age globally, with 177,000 hospitalizations among older adults in the United States alone.

Both candidate vaccines contain the recombinant prefusion RSV antigen subunit (RSVPreF3), which can trigger an immune response in the immune system. The candidate vaccine for older adults also includes GSK’s proprietary AS01 adjuvant system to enhance the immune response. Both have been granted Fast Track designation by the U.S. FDA.

A trial conducted in 1,005 healthy older adults (aged 60–80 years) receiving varying doses of antigen and adjuvant demonstrated that, one month post-vaccination, the candidate vaccine elicited robust humoral and cellular immune responses compared to baseline. Levels of protective antibodies (RSVPreF3-specific IgG antibodies and RSV-A neutralizing antibodies) induced in the vaccinated groups increased nearly 10-fold.

Importantly, the cellular immune response (RSVPreF3-specific CD4+ T cells) in vaccinated older adults was enhanced to levels comparable to those observed in young adults following vaccination with an unadjuvanted vaccine, despite the lower baseline levels initially observed in older adults compared to young adults.

In 502 healthy non-pregnant women, trial data for the maternal RSV candidate vaccine showed that, compared with baseline:

The investigational vaccine rapidly boosted pre-existing immunity across all dose levels, eliciting high levels of protective neutralizing antibodies. On day 8 post-vaccination, a 14-fold increase in neutralizing antibody titers against RSV-A and RSV-B was observed.

References:

[1] GSK presents positive clinical data on maternal and older adults RSV candidate vaccines. Retrieved October 21, 2020, from https://www.gsk.com/en-gb/media/press-releases/gsk-presents-positive-clinical-data-on-maternal-and-older-adults-rsv-candidate-vaccines/

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