Vaxcyte Advances Study of New Vaccine for Pneumococcal Disease in Infants, Pegtibatinase Maintained Significant Reductions in Toxic Metabolites

Author: Benzinga Newsdesk | September 03, 2025 07:33am

Vaxcyte, Inc. (NASDAQ:PCVX), a clinical-stage vaccine innovation company engineering high-fidelity vaccines to protect humankind from the consequences of bacterial diseases, today announced advancement of the modified VAX-31 infant Phase 2 randomized, dose-finding study to the third and final stage. This study is evaluating the safety, tolerability and immunogenicity of VAX-31, a 31-valent pneumococcal conjugate vaccine (PCV) candidate designed to prevent invasive pneumococcal disease (IPD), compared to today's standard-of-care, Prevnar 20 (PCV20), in healthy infants.

The study advanced to the third and final stage following modifications to the protocol to add a new dose arm to evaluate the VAX-31 Optimized Dose (majority of serotypes dosed at 4.4mcg and the balance dosed at 3.3mcg) and discontinue enrollment in the Low Dose arm. The Middle and High Dose arms are continuing as planned. The randomized, double-blind, active-controlled, dose-finding study will enroll approximately 900 total participants. The Company intends to deliver topline safety, tolerability and immunogenicity data from the primary immunization series and the booster dose either sequentially or together by the end of the first half of 2027.

"Advancing our modified VAX-31 infant study with the addition of the new VAX-31 Optimized Dose arm represents an important milestone for the program," said Grant Pickering, Chief Executive Officer and Co-Founder of Vaxcyte. "We leveraged key insights from the robust VAX-24 and VAX-31 data announced to date and designed the Optimized Dose with the majority of serotypes dosed at 4.4mcg and the balance dosed at 3.3mcg to elicit even stronger immune responses in infants. We believe this approach best positions VAX-31, which offers the potential to become the most broad-spectrum PCV covering ~92% of IPD and ~93% of acute otitis in U.S. children under five, for long-term success in the infant population."

"Streptococcus pneumoniae remains a leading cause of vaccine-preventable deaths among children under five," said Jim Wassil, Executive Vice President and Chief Operating Officer of Vaxcyte. "The public health community has clearly signaled a need for a pneumococcal vaccine with a broader spectrum of coverage to provide greater protection against this disease. As the broadest-spectrum PCV candidate currently in the clinic, VAX-31 has the potential to significantly reduce the burden of disease in infants by expanding coverage against currently and historically circulating strains while maintaining robust immune responses."

About the VAX-31 Infant Phase 2 Dose-Finding Study

The VAX-31 infant Phase 2 dose-finding, three-stage study is a randomized, double-blind, active-controlled, clinical study evaluating the safety, tolerability and immunogenicity of VAX-31 compared to PCV20.

• Stage 1 (safety review; completed): The safety and tolerability of VAX-31 was evaluated at three dose levels (Low, Middle and High) and compared to PCV20 in 48 infants in a dose-escalation approach.
• Stage 2 (modified and incorporated into Stage 3): This stage is evaluating the safety, tolerability and immunogenicity of VAX-31 at the same three dose levels and compared to PCV20. The study includes a primary immunization series with doses given at two, four and six months of age, followed by a booster dose at 12-15 months of age. On August 6, 2025, the Company announced modifications to the ongoing study to add the new VAX-31 Optimized Dose arm, with the majority of serotypes dosed at 4.4mcg and the balance dosed at 3.3mcg, and discontinue enrollment in the Low Dose arm.
• Stage 3 (initiated): The modified study, including the VAX-31 Optimized Dose arm, has proceeded into the third and final stage. The Middle and High Dose arms are continuing in Stage 3 as planned. All participants will be evaluated for safety through six months after the booster dose.
• Study enrollment: The modified study will comprise approximately 900 total participants, including the 100 participants previously enrolled in the Low Dose arm.
• Key prespecified immunogenicity endpoints: Immune responses for each VAX-31 dose level will be compared to PCV20 for the 20 common and the 11 unique serotypes in VAX-31. The key endpoint post-primary series (post-dose 3) will assess immune responses based on serotype-specific immunoglobulin G (IgG) seroconversion rates (proportion of participants achieving the accepted IgG threshold value of ≥0.35mcg/mL). The key endpoint post-booster dose (post-dose 4) will assess IgG geometric mean concentrations. Other key immunogenicity endpoints will also be assessed post-dose 3 and post-dose 4.
• Additional information: Further details about the study can be found at www.clinicaltrials.gov under the identifier NCT06720038. The VAX-31 Optimized Dose is listed in the study protocol as High-Pre-Filled Syringe (High-PFS).

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