Vaxcyte announced in September 2024 that its Phase I/II study of VAX-31, the 31-valent pneumococcal conjugate vaccine (PCV), has produced positive topline results. The study evaluates the safety, tolerability, and immunogenicity of the vaccine in healthy adults aged 50 and older. With strong results from the study, the company will take VAX-31 forward to an adult Phase III programme.
VAX-31 in trial
VAX-31 is Vaxcyte’s 31-valent PCV candidate for the prevention of invasive pneumococcal disease (IPD). IPD is “especially serious” in infants, young children, older adults, and people with immune deficiencies or some chronic health conditions. The vaccine candidate is the “broadest-spectrum PCV in the clinic” and offers the potential to protect against serotypes in circulation and historically prevalent serotypes.
The Phase I/II study was a randomised, observer-blind, active-controlled, dose-finding clinical study to evaluate the safety, tolerability, and immunogenicity of a single injection of VAX-31 at three dose levels and compared to PCV20 in 1,015 healthy adults aged 50 and older.
Making progress
The following results were released:
- Full six-month safety data show that VAX-31 was well tolerated and demonstrated a similar safety profile to PCV20 at all doses studied.
- Frequently reported local and systemic reactions were “generally mild-to-moderate” and no serious adverse events were linked to study vaccines.
- The vaccine candidate showed “robust” opsonophagocytic activity (OPA) immune responses for all 31 serotypes at all doses studied.
- At high and middle doses, VAX-31 met or exceeded regulatory immunogenicity criteria for all 31 serotypes. At the low dose it met or exceeded regulatory immunogenicity criteria for 29 of the 31 serotypes.
- For the 20 serotypes shared with PCV20:
- At high dose all 20 met the OPA response non-inferiority criteria, 18 out of 20 had a geometric mean ratio (GMR) greater than 1.0, and seven serotypes achieved statistically higher immune responses.
- At middle dose all 20 met the OPA response non-inferiority criteria, 13 of 20 had a GMR greater than 1.0, and five serotypes achieved statistically higher immune responses.
- At low dose, 18 of 20 met the OPA response non-inferiority criteria, 8 of 20 had a GMR greater than 1.0, and three serotypes achieved statistically higher immune responses.
- For the 11 serotypes exclusive to VAX-31 all three doses met superiority criteria.
Potential as best-in-class
CEO and Co-Founder of Vaxcyte, Grant Pickering, believes the positive results “affirm the potential” of the “site-specific, carrier-sparing platform to deliver the broadest-spectrum PCVs”.
“Based on the strength and clarity of these data, we have selected VAX-31 for the adult indication and plan to initiate the pivotal, non-inferiority Phase III study by mid-2025 and announce topline data in 2026.”
Mr Pickering shared that the company intends to initiate the remaining VAX-31 Phase III studies in 2025 and 2026 and submit a Biologics License Application (BLA) “subject to the results of these studies”. Vaxcyte’s Executive Vice President and Chief Operating Officer Jim Wassil is “exceptionally proud to share these results”, which “validate VAX-31’s potential as a best-in-class pneumococcal vaccine”. VAX-31 is capable of “raising the bar for immunogenicity standards”.
“The public health community continues to highlight the need for broader-protection vaccines to prevent IPD, which is associated with high case-fatality rates, antibiotic resistance, and meningitis. To address this need, VAX-31 was designed to increase coverage to more than 95% of IPD circulating in adults 50 and older in the US.”
Mr Wassil suggested that VAX-31 has “potential to provide significantly greater coverage relative to today’s standard-of-care adult PCVs”. He extended “sincere gratitude to everyone involved in the programme”, particularly participants, trial investigators and sites, and the team at Vaxcyte.
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