ID Biomedical announced that preliminary results from the first cohort of its Phase II Clinical Trial of the StreptAvax vaccine indicated that the immunogenicity of the vaccine was highly significant. The data showed the subunit vaccine generated antibody responses that were similar to the Phase I results in both magnitude and breadth. The median rate of seropositivity after immunization was 25 of the 26 M serotypes contained in the vaccine. The data will be presented today by Dr. Peter Vink, ID Biomedical's Associate Director of Clinical Research, at the Sixth Annual Conference on Vaccine Research in Arlington, Virginia.
The current Phase II study is evaluating the safety and immunogenicity of StreptAvax in an expanded number of adults. The trial is randomized, blinded, and comparator-controlled, using a licensed hepatitis A vaccine. The current clinical trial is providing data on the performance of StreptAvax given on a schedule identical to that used for the hepatitis A vaccine which will be used as a comparator in future pediatric studies.
Dr. Vink will present data which demonstrates that sera taken from subjects vaccinated with StreptAvax show the capacity to support statistically-significant increases in the killing, by human white blood cells, of group A streptococci belonging to all 26 bacterial serotypes included in the vaccine. These results are important because such killing is believed, since the pioneering work of Dr. Rebecca Lancefield, to be a marker for protection against future group A streptococcal disease.
"The sera from the Phase II subjects show the same broad immunogenicity of StreptAvax as we saw in Phase I, which is impressive for a vaccine targeting 26 different serotypes of bacteria," said Louis Fries, ID Biomedical's Vice President of Clinical Research. "The demonstration of bactericidal, or killing activity, is also impressive," he said. "The enzyme-linked immunosorbent assays (ELISA) that we use routinely to detect vaccine-induced antibodies is the only practical method for making these measurements in large numbers of sera - but it doesn't directly measure a biological activity that is linked to how streptococci are destroyed by the body's immune system. The demonstration of bactericidal activity does that, and has revealed vaccine-induced responses for every serotype in the vaccine." Dr. Fries also noted that StreptAvax yielded equal or greater killing activity against all 26 targeted serotypes when compared to the bactericidal activity generated by an M protein-based group A streptococcal vaccine (against only one serotype) tested in the 1970's. That single serotype vaccine was found to protect humans against challenge with live group A streptococci.