Vaxcyte Plans To Drop Developing One Pneumococcal Conjugate Vaccine

Vaxcyte Inc. PCVX on Monday released topline results from its Phase 2 dose-finding study evaluating the safety, tolerability and immunogenicity of VAX-24, a 24-valent pneumococcal conjugate vaccine (PCV) candidate designed to prevent invasive pneumococcal disease (IPD), compared to Pfizer Inc’s PFE Prevnar 20 (PCV20) in healthy infants.

The company has selected the VAX-24 Mid-dose as the basis for advancing an optimized dose formulation to a potential Phase 3 program.

Pending the VAX-31 infant Phase 2 study topline data results anticipated in mid-2026, it plans to initiate an infant Phase 3 study with either VAX-24 or VAX-31.

In this Phase 2 study, VAX-24 was well-tolerated and demonstrated a safety profile similar to PCV20 across all doses studied.

Frequently reported local and systemic reactions were generally mild to moderate, resolving within several days of vaccination, with no meaningful differences observed across the cohorts.

No serious adverse events were considered to be related to the study vaccines.

Post-dose 3, the VAX-24 Mid dose met target precedent Phase 2 non-inferiority (NI) criteria on relative seroconversion rates, particularly for the highest circulating serotypes2 contained in VAX-24 and for 20 of 24 serotypes overall.

The Mid dose also met the target Phase 2 IgG Geometric Mean Ratio (GMR) point estimate of >0.63 on all currently circulating serotypes contained in VAX-24 and for 22 of 24 serotypes overall.

Post-dose 3, VAX-24 generated robust OPA responses, which are correlated with effectiveness against IPD across all serotypes and doses.

The four serotypes unique to VAX-24 elicited immune responses and met all target criteria across all endpoints at all doses evaluated post-dose 3 (primary immunization series).

Dose-dependent immune responses were consistently demonstrated at 1.1mcg, 2.2mcg, and 4.4mcg doses. Little to no carrier suppression was observed.

Full post-dose 4 booster data is expected by the end of 2025.

An interim assessment of the IgG results was performed with currently available study samples and demonstrated:

The Mid dose met the company’s historical target Phase 2 IgG GMR point estimate of >0.6 for the highest circulating serotypes contained in VAX-24 and for 19 of 24 serotypes overall.
VAX-24 elicited memory responses across all doses for all serotypes.

Price Action: PCVX stock is down 29.5% at $48.99 during the premarket session at the last check Monday.

Read Next: