Vaxcyte Progresses to Phase 2 Study's Second Stage on VAX-31 for Infant Pneumococcal Disease Prevention

On February 5, 2025, Vaxcyte, Inc., a clinical-stage company devoted to vaccine innovation, announced the commencement of Stage 2 of their Phase 2 clinical trial involving VAX-31 in healthy infants. This progression follows a careful blinded evaluation of safety and tolerability data from Stage 1. VAX-31 is a 31-valent pneumococcal conjugate vaccine (PCV) candidate aimed at preventing invasive pneumococcal disease (IPD) in infants. The company anticipates releasing initial data concerning the vaccine's safety, tolerability, and immunogenicity from the primary immunization series by mid-2026, with booster dose data to follow approximately nine months later.

Grant Pickering, CEO and Co-Founder of Vaxcyte, highlighted the advancement to Stage 2 as a crucial milestone in assessing what he described as the most comprehensive vaccine candidate currently available for this vulnerable demographic. Pneumococcal conjugate vaccines have been integral to public health, offering essential protection against invasive pneumococcal diseases. Vaxcyte's PCV initiatives, including both VAX-24 and VAX-31, aim to extend protection against both contemporary and historical strains while ensuring robust immune responses. The company looks forward to sharing data on the safety and immune response efficacy of VAX-31 in infants.

Jim Wassil, Vaxcyte's Executive Vice President and Chief Operating Officer, emphasized the company's commitment to delivering best-in-class PCVs with broader coverage for infants and adults, backed by positive evidence from VAX-31 and VAX-24 adult trials. He believes their carrier-sparing platform could pioneer a new standard in disease coverage.

The Phase 2 infant study for VAX-31 is a randomized, double-blind, active-controlled, dose-finding investigation comparing VAX-31 to Prevnar 20 (PCV20) in healthy infants. Stage 1 examined safety and tolerability across three ascending dose levels, involving 48 infants divided into three cohorts. Doses varied for different serotypes, with participants continuing their dosing regimen into Stage 2, which includes an expanded group of approximately 750 infants. The study design aligns with the Advisory Committee on Immunization Practices (ACIP) recommendations, involving a primary immunization series at two, four, and six months, followed by a booster at 12-15 months.

The study's immunogenicity endpoints will assess immune responses to VAX-31 against PCV20 for its common and unique serotypes. A key focus will be on serotype-specific immunoglobulin G (IgG) seroconversion rates and geometric mean titers post-primary series and booster.

Pneumococcal disease, caused by the Streptococcus pneumoniae bacterium, can lead to severe conditions like meningitis and bacteremia. In the U.S., pneumococcal pneumonia causes significant hospitalizations, with the pathogen listed as a major antibiotic-resistant threat by global health authorities. The need for broader-spectrum vaccines is highlighted by the morbidity and mortality associated with pneumococcal disease, particularly in young children and older adults.

VAX-31 aims to address these challenges, offering extensive protection against a wide array of serotypes, potentially covering 94% of IPD and 93% of acute otitis media in U.S. children under five. The vaccine is also being evaluated for adults, boasting a design that could incrementally enhance coverage over existing standard-of-care vaccines.

In November 2024, Vaxcyte's VAX-31 received Breakthrough Therapy designation from the FDA for adult IPD prevention, a move intended to expedite its development and review. Vaxcyte continues to forge advancements in vaccine development, leveraging modern synthetic techniques and platforms like XpressCF™ to produce complex vaccines efficiently. The company’s pipeline includes candidates targeting Group A Strep infections and periodontal diseases, underlining its mission to combat bacterial infections with severe health consequences.