Despite announcing the trial’s success, investors were clearly hoping for more as the company’s stock price fell by more than 45% on the news. Image credit: Shutterstock / GOLDMAN99.
Vaxcyte’s stock has dropped around 45% despite a Phase II trial of its invasive pneumococcal disease (IPD) vaccine meeting all endpoints.
The Nasdaq-listed company saw its stock price, drop from a close of $69.46 on Friday 28 March to a close of $37.76 on Monday 31 March, indicating that investors were expecting more from the Phase II trial.
The Phase II dose-finding study evaluated the safety, tolerability and immunogenicity of VAX-24, a 24-valent pneumococcal conjugate vaccine (PCV) candidate for IPD. Three doses of the vaccine were evaluated – low, mid and mixed.
The vaccine was pitted against Pfizer’s Prevnar 20 (PCV20) in healthy infants and met non-inferiority criteria on relative seroconversion rates after the third injection in the mid-dose cohort.
The mid-dose also met the target Phase II immunoglobulin G (IgG) Geometric Mean Ratio (GMR) point estimate of >0.63 on all currently circulating serotypes contained in VAX-24 and for 22 of 24 serotypes overall. On top of this, the vaccine also generated robust opsonophagocytic assay (OPA) responses, which are correlated with effectiveness against IPD, across all serotypes and doses.
The four serotypes unique to VAX-24 elicited robust immune responses and met all target criteria across all endpoints at all doses evaluated post-dose three.
VAX-24 remained well-tolerated and demonstrated a safety profile similar to PCV20 across all doses studied. Frequently reported local and systemic reactions were mild to moderate, resolving within several days. No serious adverse events (AEs) were related to the study vaccines. Full data from after the fourth booster dose is expected by the end of this year.
The company is also evaluating VAX-31, a 31-valent, carrier-sparing PCV, for the prevention of IPD in both adults and infants. Vaxcyte is now waiting for data from the VAX-31 infant Phase II study, which is expected in mid-2026, before deciding which vaccine to advance, mid-dose VAX-24 or VAX-31, to Phase III trials in infants for IPD. VAX-31 is already advancing to Phase III in adults.
Vaxcyte’s CEO Grant Pickering said: “These results affirm the potential of our carrier-sparing platform to add coverage and maintain robust immune responses, reinforcing our confidence as we advance our PCVs into adult and infant Phase III programmes.
“Building on this momentum, we are announcing VAX-XL, our third-generation PCV candidate designed to provide the broadest coverage PCV currently in development. I am incredibly proud of the entire Vaxcyte team for these achievements.”
GlobalData classifies Pfizer as one of the key players in the IPD space with a patient-based sales forecast for Prevnar 20 of $3.71bn in 2030. Meanwhile, Vaxcyte’s VAX-24 is due to bring in $2.27bn in 2030.
GlobalData is the parent company of Clinical Trials Arena.
IPDs include meningitis and bacteraemia while non-invasive pneumococcal diseases include pneumonia, otitis media and sinusitis. These infections are caused by the Streptococcus pneumoniae bacteria, which is among the World Health Organization’s (WHO) top antibiotic-resistant pathogens that need to be urgently addressed. It is the leading cause of vaccine-preventable deaths in children under five worldwide.
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