Vaxcyte, Inc. announced the completion of enrollment in its Phase 1/2 clinical study evaluating VAX-31, a 31-valent pneumococcal conjugate vaccine (PCV) candidate designed to prevent invasive pneumococcal disease (IPD), in healthy adults aged 50 and older. Vaxcyte expects to announce topline safety, tolerability and immunogenicity data from the Phase 1/2 study in the third quarter of 2024. The VAX-31 Phase 1/2 clinical study, which is now fully enrolled, is a randomized, observer-blind, active-controlled, dose-finding clinical study designed to evaluate the safety, tolerability and immunogenicity of VAX-31 at three dose levels (low, middle and high) and compared to Prevnar 20® (PCV20) in 1,015 healthy adults aged 50 and older.

The Phase 1 portion of the study evaluated the safety and tolerability of a single injection of VAX-31 at three dose levels and compared to PCV20 in 64 healthy adults 50 to 64 years of age. An independent Data Monitoring Committee conducted an assessment of the Phase 1 safety and tolerability results and recommended that the study proceed as planned to Phase 2. Phase 1 participants will also be evaluated for immunogenicity, and the data will be pooled with the participants in the Phase 2 portion of the study. The Phase 2 portion of the study will evaluate the safety, tolerability and immunogenicity of a single injection of VAX-31 at the same three dose levels and compared to PCV20 in 951 healthy adults 50 years of age and older.

The immunogenicity objectives of the study include an assessment of the induction of antibody responses, using opsonophagocytic activity (OPA) and immunoglobulin G (IgG), at each of the three VAX-31 doses and compared to PCV20 for the 20 serotypes in common, as well as for the additional 11 serotypes contained in VAX-31, but not in PCV20. Participants in the study are being evaluated for safety through six months after vaccination. The study is being conducted in approximately 25 sites in the United States.