Vaxcyte, Inc. (PCVX) has announced promising results from its Phase 1/2 clinical trial for VAX-31, its 31-valent pneumococcal conjugate vaccine (PCV) candidate. The trial assessed the safety, tolerability, and immunogenicity of VAX-31 in 1,015 healthy adults aged 50 and older.
The results indicate that VAX-31 was well-tolerated and demonstrated a favorable safety profile, similar to Pfizer Inc’s Prevnar 20 (PCV20), across all doses and throughout the six-month evaluation period. Furthermore, the vaccine showed robust immune responses, as measured by opsonophagocytic activity (OPA), against all 31 serotypes included in the vaccine at all doses tested.
Importantly, VAX-31 met or exceeded the non-inferiority criteria for OPA responses for all 20 serotypes shared with PCV20 at both the middle and high doses. In fact, at the high dose, VAX-31 achieved greater average OPA immune responses for 18 of these 20 serotypes compared to PCV20. Seven of these serotypes even demonstrated statistically higher immune responses than PCV20. Similar trends were observed at the middle dose, with 13 of 20 serotypes showing greater OPA responses than PCV20.
For the 11 serotypes unique to VAX-31, all three doses met the superiority criteria, signifying a significant advantage over existing pneumococcal vaccines. This is a crucial point, as these additional serotypes represent emerging strains that are increasingly contributing to invasive pneumococcal disease.
Following the positive Phase 1/2 results, Vaxcyte has selected VAX-31 to advance to an adult Phase 3 program. The company plans to initiate a pivotal, non-inferiority Phase 3 study by mid-2025, with topline data expected in 2026. This follows an FDA End-of-Phase 2 meeting to discuss the next steps for VAX-31’s development.
In parallel with the ongoing Phase 3 program, Vaxcyte is also planning to initiate a Phase 2 study for VAX-31 in infants in the first quarter of 2025, pending IND application submission and approval. This will be done in conjunction with their existing VAX-24 study for a 24-valent PCV candidate.
The positive results from the Phase 1/2 trial represent a significant milestone for Vaxcyte and demonstrate the potential of VAX-31 to become a leading option for pneumococcal vaccine prevention. The company’s plans to advance VAX-31 to Phase 3 trials in both adults and infants highlight their commitment to addressing the global burden of pneumococcal disease.
The news of Vaxcyte’s successful Phase 1/2 trial has led to a significant surge in PCVX stock price, which was trading 42.3% higher at $114.91 at the last check on Tuesday.
