Vaxcyte, Inc. (Nasdaq: PCVX), a clinical-stage vaccine company, said OPUS-1, the pivotal adult Phase III trial of its 31-valent pneumococcal conjugate vaccine candidate VAX-31, produced positive topline results, with VAX-31 meeting all prespecified primary endpoints across the age groups studied.
OPUS-1 dosed 4,047 participants at approximately 30 US sites, including 3,572 healthy, pneumococcal-naïve adults aged 50 and older randomized 1:1:1 to Vaxcyte's 31-valent pneumococcal conjugate vaccine candidate VAX-31, Prevnar 20 (PCV20) or Capvaxive (PCV21), plus a separate cohort of 475 adults aged 18-49; Vaxcyte reported that all 28 serotypes shared with PCV20 and/or PCV21 met the prespecified noninferiority criterion, that the three serotypes unique to VAX-31 and cross-reactive serotype 20B met the superiority criterion, and that in the immunobridging analysis VAX-31 met the noninferiority criterion across all 32 serotype comparisons in adults aged 18-49 versus adults aged 50-64.
Vaxcyte said that in prespecified individual comparator analyses, VAX-31 met the noninferiority criterion (lower bound of the 95% confidence interval above 0.667) for 20 of 20 serotypes shared with PCV20 and 17 of 19 shared with Capvaxive (PCV21), while serotypes 3 and 12F missed that criterion against Capvaxive and met only the historical threshold of above 0.5.
VAX-31 was well tolerated, with a safety profile similar to both comparators.
VAX-31 holds an FDA Breakthrough Therapy designation, expanded in May 2025 to include prevention of pneumococcal pneumonia in addition to invasive pneumococcal disease (IPD). The Phase III program builds on a Phase I/II study published in The Lancet Infectious Diseases, in which VAX-31 met noninferiority for all 20 serotypes shared with PCV20 and superiority for all 11 unique serotypes.