Raxibacumab for the Treatment of Inhalational Anthrax

Background Inhalational anthrax caused by Bacillus anthracis is associated with high mortality primarily due to toxin-mediated injury. Raxibacumab is a human IgG1λ monoclonal antibody directed against protective antigen, a component of the anthrax toxin. Methods We evaluated the efficacy of raxibacumab as a prophylactic agent and after disease onset in a total of four randomized, placebo-controlled studies conducted in rabbits and monkeys. Animals were exposed to an aerosolized target exposure of B. anthracis spores that was approximately 100 times (in the prophylactic studies) and 200 times (in the therapeutic-intervention studies) the median lethal dose. In the therapeutic-intervention studies, animals were monitored for the onset of symptoms. Animals with detectable protective antigen in serum, a significant increase in temperature, or both received a single intravenous bolus of placebo or raxibacumab at a dose of either 20 mg per kilogram of body weight or 40 mg per kilogram. The primary end point was...