Vaxcyte (PCVX) Study Result summary

Study highlights

• Phase 1/2 study of VAX-31, a 31-valent pneumococcal conjugate vaccine, in adults aged 50+ showed robust safety, tolerability, and immunogenicity, supporting advancement to phase III.

• VAX-31 demonstrated a safety profile similar to PCV20 across all doses, with most adverse events mild or moderate and no related serious adverse events reported.

• Immunogenicity data showed VAX-31 met or exceeded regulatory criteria for all 31 serotypes at high and middle doses, with strong dose-dependent responses and superiority for all 11 incremental serotypes not covered by PCV20.

• The study enrolled 1,015 adults, with high retention and well-balanced demographics; over 96% completed immunogenicity follow-up.

• IgG data were consistent with OPA results, confirming robust immune responses.

Next steps and strategic plans

• VAX-31 will advance to a phase III pivotal non-inferiority study in adults, targeted to start by mid-2025, with top-line data expected in 2026.

• Pediatric phase II study is planned for Q1 2025, with topline data expected in mid-2026.

• Manufacturing scale-up is underway, with a dedicated facility being built to support anticipated demand in both adult and infant markets.

• The company is prepared to meet potential increased demand if a preferred recommendation is granted and is considering international expansion strategies.

• Additional pipeline opportunities are being explored, including next-generation PCVs and a Group A strep conjugate vaccine.

Competitive and regulatory considerations

• VAX-31’s broad serotype coverage and strong immune responses may support a preferred recommendation by ACIP if phase III results are consistent.

• Dose selection for phase III will weigh immunogenicity, safety, and cost, with both mid and high doses showing strong profiles.

• The platform’s site-specific conjugation technology is credited for the strong immunogenicity, with potential advantages in infants due to lower carrier burden.

• Regulatory strategy includes discussions with the FDA on dose selection and potential cross-protection claims for additional serotypes.

• The company is monitoring market and regulatory developments, including possible lowering of adult vaccination age recommendations.