Vaxcyte Doses First Participants in OPUS-3 Phase 3 Trial Evaluating VAX-31; Company Expects To Report Topline Data From OPUS-3 Trial And OPUS-2 Phase 3 Trial Evaluating Concomitant Administration Of VAX-31 And A Seasonal Influenza Vaccine In First Half Of 2027

Vaxcyte, Inc. (NASDAQ:PCVX), a clinical-stage vaccine innovation company, today announced that the first participants were dosed in the OPUS-3 Phase 3 trial evaluating VAX-31, the Company's next-generation 31-valent pneumococcal conjugate vaccine (PCV) candidate, in adults who have previously received pneumococcal vaccination. This trial is evaluating the safety, tolerability and immunogenicity of VAX-31, including whether VAX-31 can boost serotype-specific immune responses, while providing the broadest coverage in a single vaccine in this adult population.

Vaxcyte is advancing a comprehensive Phase 3 adult clinical program for VAX-31 to support a planned Biologics License Application (BLA) submission. The announced Phase 3 clinical studies, which were finalized in consultation and alignment with the U.S. Food and Drug Administration (FDA), include the pivotal, noninferiority trial evaluating VAX-31 for the prevention of invasive pneumococcal disease (IPD) and pneumonia in adults (OPUS-1, enrolling); a trial evaluating VAX-31 when administered concomitantly with a licensed seasonal influenza vaccine in pneumococcal-naïve1 adults (OPUS-2, enrolling); and a trial in adults who have previously received a pneumococcal vaccine (OPUS-3, enrolling). Across these three studies, approximately 6,000 adults are expected to be enrolled in total, of whom approximately 3,400 will receive VAX-31, with the intent to generate a broad and robust safety, tolerability and immunogenicity dataset. Vaxcyte is also planning to conduct a manufacturing consistency study (e.g., a lot-to-lot study) to support the planned BLA filing.

"The initiation of our Phase 3 study evaluating VAX-31 administered to adults with prior pneumococcal vaccination marks continued progress for the program as we work toward delivering a best-in-class, next-generation PCV with the potential to set a new standard-of-care for adults," said Grant Pickering, Chief Executive Officer and Co-founder of Vaxcyte. "Given the potential for VAX-31 to significantly expand protection and provide substantial incremental coverage of approximately 19-31% against pneumococcal pneumonia relative to current standard-of-care vaccines, it is important to understand how VAX-31 may boost immune responses in adults who previously received lower-valency pneumococcal vaccines and broaden serotype coverage."

About OPUS-3, the VAX-31 Adult Phase 3 Trial in Subjects Who Have Previously Received a Pneumococcal Vaccine (n~720)

This Phase 3 study is a randomized, double-blind, active-controlled, descriptive clinical trial designed to evaluate the safety, tolerability and immunogenicity of a single dose of VAX-31 in approximately 720 healthy U.S. adults aged 50 years and older with a history of prior pneumococcal vaccination at least six months prior. The study is being conducted at approximately 30 sites in the United States.