Vaxcyte reports VAX‑31 met all OPUS‑1 primary immune endpoints
The vaccine met the stricter direct test for 17 of 19 serotypes shared with Capvaxive, with two meeting an older threshold.
Adrian Kessler
All prespecified primary immune-response endpoints were met in a pivotal adult pneumococcal vaccine trial as Vaxcyte, Inc. NASDAQPCVX reported its OPUS-1 results on Monday. All 28 serotypes VAX-31 shares with one or both comparator vaccines met the trial's planned noninferiority test, according to Vaxcyte's Oct. 5 release.
The result supplies the central immunogenicity evidence for a planned U.S. biologics licence application in the first half of 2028, after two other adult trials report. OPUS-1 measured immune responses one month after vaccination; the company did not report a comparison of disease cases between vaccine groups.
Vaxcyte is a clinical-stage vaccine developer in California building pneumococcal products for adults and infants.
Shares closed at US$56.48 on Oct. 2 at 4:00 p.m. EDT, according to the NASDAQPCVX quote page. That regular-session price preceded Monday's readout and does not measure its market reaction.
Two Serotypes Missed The Stricter Direct Comparison
The Oct. 5 trial description says OPUS-1 dosed 4,047 adults at U.S. sites. In the older cohort, 3,572 people aged at least 50 were assigned equally to VAX-31, Prevnar 20 or Capvaxive. A separate 475-person younger cohort received VAX-31 or Prevnar 20, the safety comparator. Those participants were aged 18 to 49 and were assigned in a three-to-one allocation.
For the primary shared-serotype analyses in older adults, noninferiority required the lower bound of the 95 per cent confidence interval for the immune-response ratio to exceed 0.667. The three serotypes unique to VAX-31 and cross-reactive serotype 20B met a separate superiority criterion requiring that bound to exceed 2.0. The younger cohort met the planned immunobridging threshold on all 32 serotype comparisons. Those comparisons used responses in adults aged 50 to 64.
The direct comparisons were less uniform than the combined primary result. VAX-31 met the stricter threshold for all 20 serotypes shared with Prevnar 20. It did so for 17 of 19 shared with Capvaxive. Serotypes 3 and 12F missed that stricter Capvaxive comparison, though both met the historical lower-bound threshold of 0.5, Vaxcyte said in its Oct. 5 release. The company reported a safety profile similar to both comparator vaccines across the ages studied; follow-up for safety runs for six months after vaccination.
"We believe these positive OPUS-1 results provide clinical validation of our site-specific, carrier-sparing platform's potential to deliver broader-spectrum pneumococcal vaccines while maintaining the magnitude of immune responses," Vaxcyte chief executive Grant Pickering said in the release.
Read more: Genmab A/S reports 45.9 per cent Rina-S response in ovarian cancer trial
Further Adult Data Precede The FDA Filing
Merck & Co., Inc. NYSEMRK sells Capvaxive, the 21-valent vaccine used as one OPUS-1 comparator. Its prescribing information says the adult pneumonia indication has accelerated approval based on immune responses, with clinical benefit still subject to confirmation. The distinction keeps Vaxcyte's immunogenicity result separate from a demonstrated reduction in pneumococcal pneumonia cases.
The iShares Biotechnology ETF NASDAQIBB stood at US$205.29 just after 4 p.m. EDT on Oct. 2, according to its linked quote page. That sector price, like Vaxcyte's last regular-session quote, predates the OPUS-1 announcement.
Vaxcyte said in a Jan. 22 program update that its adult Phase 3 studies were finalized in consultation and alignment with the U.S. Food and Drug Administration. The company expects OPUS-2, which tests administration alongside an influenza vaccine, and OPUS-3, which tests previously vaccinated adults, to report in the first half of 2027. Those results and a subsequent manufacturing consistency study will precede the planned first-half 2028 application.
Read more: Evaxion schedules November immune update after 2025 melanoma readout
The first-half 2027 OPUS-2 and OPUS-3 readouts are the next dated tests of VAX-31's adult program before Vaxcyte seeks FDA review.
