FDA posts anthrax briefing docs

FDA posted briefing documents ahead of Tuesday's meeting of the Vaccines and Related Biological Products Advisory Committee to discuss the development of protective-antigen based anthrax vaccines for post-exposure prophylaxis under the agency's Animal Rule. FDA, which said protective antibody levels in animals are likely a good indicator of the immune response of a vaccine candidate in humans, recommended the general use prophylaxis (GUP) study design over two other designs reviewed. In GUP studies, animals are initially immunized with vaccine followed by challenge with Bacillus anthracis spores at a defined interval.

FDA said the two other designs, post-exposure prophylaxis and passive immunization studies, would serve as proof-of-concept but would not be used to estimate a protective antibody level in humans. In post-exposure prophylaxis studies, animals are first challenged with aerosolized B. anthracis and then administered antibiotics with or without vaccine. Animals in passive immunization studies are initially given antitoxin antibodies and are subsequently challenged with aerolized B. anthracis. FDA said that due to the two studies' complexities, each had a high level of uncertainty in estimating protective antibody levels. ...