Pfizer's GBS6 Vaccine Candidate Showcases Promising Protection for Infants Against Invasive GBS Disease: Phase 2 Study Reveals

Pfizer Inc PFE announced data from a Phase 2 study investigating its hexavalent capsular polysaccharide (CPS) conjugate Group B Streptococcus (GBS) vaccine candidate, GBS6, being developed for maternal administration to protect infants against invasive GBS disease. 

The data come from the second of a three-part study, which enrolled 360 healthy pregnant individuals in South Africa who received a dose of either 5, 10, or 20 µg/serotype. 

GBS6 generated robust maternal antibody responses against the six GBS CPS serotypes included in the vaccine.

Based on a parallel natural history study conducted in South Africa, the Phase 2 study immunogenicity data suggest that GBS6 may offer meaningful protection against invasive GBS disease in newborns and young infants. 

These antibodies were “efficiently transferred to infants at approximate ratios of 0.4 and 1.3, dependent on the serotype. The highest antibody responses were generally observed with the 20 µg dose.

Pfizer then compared this immunogenicity data to a parallel study of anti-CPS immunoglobulin antibody concentrations conducted in South Africa among 18,000 unvaccinated pregnant individuals and their infants, which suggested that GBS6 did offer protection. 

The safety profile in both mothers and infants was similar between the two studies.

Pfizer noted that most solicited systemic events were classed as mild or moderate.

Depending on the dose received, 45% to 70% of participants in the GBS6 trial experienced adverse events, compared to 61% of the placebo group. The most common and serious adverse events were conditions related to pregnancy.

Among the infants, adverse events occurred in 62% to 75% of the GBS6 groups and 74% of those in the placebo group. None of the serious adverse events were considered to be related to the vaccine.

As well as publishing the results in The New England Journal of Medicine, Pfizer said the data will now inform a phase 3 program. 

 A final formulation is being evaluated in 216 healthy pregnant individuals and their infants in South Africa, the U.S., and the U.K.

Price Action: PFE shares are up 0.22% at $36.52 during the premarket session on the last check Thursday.