Vaxcyte Begins Phase 2 Trial of VAX-31 to Prevent Infant Pneumococcal Disease

Vaxcyte, Inc. has initiated a Phase 2 study of VAX-31, a 31-valent pneumococcal conjugate vaccine candidate, in healthy infants. The participants of this study have begun receiving doses. This trial aims to assess the safety, tolerability, and immunogenicity of VAX-31, which is designed to protect against invasive pneumococcal disease (IPD). Vaxcyte anticipates releasing topline data from the primary immunization series in mid-2026, followed by data from a booster dose around nine months later.

Grant Pickering, CEO and Co-founder of Vaxcyte, highlighted the significance of this milestone in advancing their pneumococcal conjugate vaccine (PCV) clinical programs, including the ongoing VAX-24 Phase 2 infant study. He emphasized that PCVs are crucial in combating Streptococcus pneumoniae, especially with rising antimicrobial resistance. VAX-31, being the broadest-spectrum PCV candidate in clinical trials, aims to extend coverage and provide protection against various serotypes. Pickering expressed enthusiasm for sharing the forthcoming data on VAX-31's safety, tolerability, and immunogenicity.

Jim Wassil, Executive Vice President and COO of Vaxcyte, noted that despite the effectiveness of current vaccines, Streptococcus pneumoniae remains the leading cause of vaccine-preventable deaths among children under five. He pointed out the necessity for a broader-spectrum vaccine to enhance protection against this disease. VAX-31 is intended to cover approximately 94% of IPD and about 93% of acute otitis media in U.S. children under five, potentially offering greater coverage compared to current standard-of-care PCVs.

The VAX-31 Phase 2 infant study is a randomized, double-blind, active controlled, dose-finding, two-stage clinical trial. It compares the safety, tolerability, and immunogenicity of VAX-31 to Prevnar 20 (PCV20) in healthy infants.

Pneumococcal disease, caused by Streptococcus pneumoniae, can lead to serious conditions such as meningitis and bacteremia (invasive pneumococcal disease, IPD), as well as pneumonia, otitis media, and sinusitis (non-invasive pneumococcal disease). In the U.S., pneumococcal pneumonia leads to approximately 150,000 hospitalizations annually. Streptococcus pneumoniae is recognized by the World Health Organization and the U.S. CDC as a significant antibiotic-resistant pathogen posing a serious threat. In children under five, it is the foremost cause of vaccine-preventable deaths globally and responsible for over half of all bacterial meningitis cases in the U.S. Although antibiotics are used to treat pneumococcal disease, some bacterial strains have become resistant, highlighting the urgent need for a more comprehensive vaccine.

VAX-31, now advancing to a Phase 3 adult clinical program and undergoing Phase 2 infant trials, is designed to prevent IPD. This condition is particularly severe in infants, young children, older adults, and individuals with immune deficiencies or chronic health conditions. VAX-31 aims to offer broad protection against both current and historically prevalent serotypes, covering over 95% of IPD in U.S. adults aged 50 and older and offering significant incremental coverage over existing adult PCVs. For infants, it targets approximately 94% coverage of IPD and 93% of acute otitis media caused by Streptococcus pneumoniae in children under five.

In November 2024, the FDA granted VAX-31 Breakthrough Therapy designation for preventing IPD in adults, aiming to expedite the development and review of treatments for serious conditions.

Vaxcyte is committed to developing high-fidelity vaccines using advanced synthetic techniques and the XpressCF™ cell-free protein synthesis platform from Sutro Biopharma, Inc. This innovative approach aims to efficiently create and deliver complex vaccines with enhanced immunological benefits. Vaxcyte's pipeline includes vaccines targeting Group A Strep, periodontal disease, and Shigella, underscoring their mission to combat serious bacterial infections.