Leveraging Affinivax’s Multiple Antigen-Presenting System (MAPS) platform, ASP3772 is meant for B-cell (antibody) and T-cell immune protection against the bacteria.
The vaccine candidate contains 24 pneumococcal polysaccharides and two conserved pneumococcal proteins.
According to data from the Phase II trial, the vaccine candidate was well tolerated and demonstrated an antibody response to all 24 polysaccharides. It had another antibody response to the conserved pneumococcal proteins.
The trial involved 503 adults aged 65 to 85 years, of which 293 were given ASP3772, 97 were given Prevnar13 and 113 who had prior Prevnar13 vaccination were given Pneumovax23.
Safety/tolerability and reactogenicity of ASP3772 versus Prevnar13 was the trial’s main objective.
The secondary objective was the vaccine candidate’s immunogenicity compared with Prevnar13 or Pneumovax23.
Results showed that mild and self-limited injection site and systemic reactions were comparable in the investigational vaccine and Prevnar13 arms. No serious adverse events related to the vaccine were reported.
All three tested dose levels of ASP3772 stimulated a strong immune response to each of its 24 pneumococcal serotypes, as determined by immunoglobulin G (IgG) and opsonophagocytic activity (OPA).
The vaccine candidate showed a similar or better IgG and OPA immune response for the 13 serotypes shared with Prevnar13, when compared to only Prevnar13. ASP3772 had statistically higher immune responses to the remaining 11 serotypes.
Compared to Prevnar13 and Pneumovax23, the vaccine candidate had a similar or better IgG and OPA immune response for the 13 serotypes that are also present in Prevnar13.
Based on these Phase II results, the US Food and Drug Administration granted breakthrough therapy designation for ASP3772 to prevent pneumonia and invasive disease from Streptococcus pneumoniae serotypes included in the vaccine in people aged 50 years and above.
Affinivax CEO Steven Brugger said: “Extending the coverage to 24 Streptococcus pneumoniae strains, we believe that ASP3772 has the potential to offer broader protection than any pneumococcal vaccine currently on the market or in clinical testing today, and we look forward to continuing to advance this important vaccine candidate through clinical trials in both adults and infants.”
Preparations are underway for Phase III registration trials of ASP3772 in adults.
In addition, a Phase II trial in infants will be commenced if positive data is obtained in the ongoing Phase I trial in healthy toddlers aged 12 to 15 months.
This May, Pfizer commenced a new study analysing the co-administration of a booster dose of its Covid-19 vaccine followed by its 20-valent pneumococcal conjugate vaccine (20vPnC) candidate in adults aged 65 years and above.