Vaxcyte stock tumbles following Phase 2 study results

Investing.com -- Shares of Vaxcyte, Inc. (Nasdaq: PCVX) fell 26% today after the company announced topline results from its Phase 2 dose-finding study of VAX-24 in infants, which compared the safety, tolerability, and immunogenicity of their vaccine candidate against Prevnar 20®. Despite the company’s positive portrayal of the study outcomes, the stock’s downturn reflects investor concerns.

The clinical-stage vaccine company, which aims to protect against bacterial diseases, highlighted that VAX-24 was well-tolerated and demonstrated a safety profile comparable to PCV20 across all doses studied. The vaccine candidate elicited substantial immune responses following the initial three-dose immunization series and interim booster dose IgG data showed robust memory responses. The company has chosen the VAX-24 Mid dose (2.2mcg) for an optimized dose formulation to advance to a potential Phase 3 program.

Vaxcyte also announced the development of VAX-XL, their third-generation PCV candidate, which is intended to expand the spectrum of coverage even further. The complete VAX-24 data set is expected by the end of 2025, with the VAX-31 Phase 2 study topline data anticipated in mid-2026. For the adult indication, the Phase 3 non-inferiority study for VAX-31 is expected to start in mid-2025 with topline data following in 2026.

The study found that post-dose 3, the VAX-24 Mid dose met target Phase 2 non-inferiority criteria on relative seroconversion rates and Geometric Mean Ratio (GMR) point estimates for the highest circulating serotypes. Additionally, all doses of VAX-24 generated robust opsonophagocytic assay (OPA) responses, which are correlated with effectiveness against invasive pneumococcal disease (IPD), across all serotypes.

Despite these findings, the immediate market reaction has been negative, with the company’s stock experiencing a significant drop. This movement may indicate investor skepticism or concerns about the vaccine’s commercial prospects or competitive position in the market. The company remains focused on its commitment to advancing the broadest-spectrum PCVs to address the invasive pneumococcal disease burden in infants and strengthen community immunity.

Vaxcyte’s CEO, Grant Pickering, expressed pride in the team’s achievements and reinforced the potential of the company’s carrier-sparing platform to maintain robust immune responses while adding coverage. Jim Wassil, Executive Vice President and COO, emphasized the ongoing effort to reduce the impact of Streptococcus pneumoniae, particularly in children under five.

The VAX-24 infant Phase 2 clinical study is an ongoing randomized, observer-blind, dose-finding study that has enrolled 802 participants. It aims to evaluate the immunogenicity of VAX-24 post-dose 4 and safety through six months post-dose 4. The study compared VAX-24 at three dose levels to PCV20, currently the broadest-spectrum PCV available.

Vaxcyte will continue to provide updates on their PCV programs, with several key milestones anticipated for both adult and infant indications. The webcast and conference call held today aimed to discuss the results from the VAX-24 infant Phase 2 study further.

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