Vaxcyte, Inc. announced that the first participants were dosed in a Phase 1/2 clinical study for VAX-31, a 31-valent pneumococcal conjugate vaccine (PCV) candidate designed to prevent invasive pneumococcal disease (IPD), in adults. The study, which will evaluate the safety, tolerability and immunogenicity of VAX-31, is expected to enroll approximately 1,000 adults aged 50 and older. The Company expects to announce topline data from the Phase 1/2 study in the second half of 2024.

The Phase 1 portion of the study will evaluate the safety and tolerability of a single injection of VAX-31 at three dose levels (low, middle and high) and compared to PCV20 in approximately 64 healthy adults 50 to 64 years of age. An independent Data Monitoring Committee will conduct an assessment of the Phase 1 safety and tolerability results prior to the study proceeding to Phase 2. Phase 1 participants will also be evaluated for immunogenicity, and the Phase 1 safety, tolerability and immunogenicity data will be pooled with the participants in the Phase 2 portion of the study. Phase 2 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 approximately 936 healthy adults 50 years of age and older.

In both portions of the study, participants will be randomized equally in four separate arms and 30 days after participants are dosed, serology samples will be collected to assess immunogenicity.