Tuesday, Vaxcyte, Inc. ( PCVX ) released topline results from the Phase 1/2 study evaluating the safety, tolerability and immunogenicity of VAX-31, the company's 31-valent pneumococcal conjugate vaccine (PCV) candidate designed to prevent invasive pneumococcal disease.

VAX-31 was well tolerated and demonstrated a safety profile at all doses studied through the full six-month evaluation period, similar to Pfizer Inc's ( PFE ) Prevnar 20 (PCV20).

VAX-31 showed robust opsonophagocytic activity (OPA) immune responses for all 31 serotypes at all doses studied.

Also Read: Vaccine Player Vaxcyte Has Advantage Over Pfizer, Merck's Pneumococcal Shots – Analyst Says.

At the middle and high doses, VAX-31 met or exceeded the OPA response non-inferiority criteria for all 20 serotypes common with PCV20.

At the VAX-31 high dose, average OPA immune responses were greater for 18 of 20 serotypes than PCV20 (geometric mean ratio (GMR) greater than 1.0), with seven of these serotypes achieving statistically higher immune responses than PCV20.

At the middle dose, 13 of 20 serotypes had a GMR greater than 1.0, and five serotypes achieved statistically higher immune responses compared to PCV20.

For all 11 incremental serotypes unique to VAX-31, all three doses met the superiority criteria.

The study compared VAX-31 to PCV20 in 1,015 healthy adults aged 50 and older.

The company has selected VAX-31 to advance to an adult Phase 3 program.

Following an FDA End-of-Phase 2 meeting, Vaxcyte ( PCVX ) plans to initiate a Phase 3 pivotal, non-inferiority study by mid-2025 and announce topline safety, tolerability, and immunogenicity data in 2026.

The FDA recently approved Merck & Co Inc's Capvaxive (Pneumococcal 21-valent Conjugate Vaccine) as the first pneumococcal conjugate vaccine designed to protect adults.

For pediatric indication, in parallel with ongoing VAX-24 study, the company plans to initiate VAX-31 infant Phase 2 study in first quarter of 2025 following IND application submission and clearance.

Price Action: PCVX stock is trading 42.3% higher at $114.91 at the last check on Tuesday.

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