FDA approves raxibacumab injection for treatment of inhalational anthrax

The U.S. Food and Drug Administration approved the raxibacumab injection on Friday for the treatment of inhalational anthrax, making it the first monoclonal antibody approved under the administration's Animal Efficacy Rule.

Raxibacumab neutralizes toxins produced by Bacillus anthracis bacteria that can lead to tissue damage and death. The FDA gave raxibacumab fast track designation, orphan product designation and priority review after it demonstrated the ability to satisfy an unmet medical need, treat a rare disease and provide treatment where no there is no satisfactory alternative.

The Animal Efficacy Rule allows the FDA to approve a countermeasure when efficacy findings from animal studies support approval and when it is not ethical or feasible to conduct human trials.

"In addition to antibiotics, raxibacumab will be a useful treatment to have available should an anthrax bioterrorism event occur," Edward Cox, the director of the FDA's Office of Antimicrobial Products, said. "Although antibiotics are approved to prevent and treat anthrax infection, raxibacumab is the first approved agent that acts by neutralizing the toxins produced by B. anthracis."

Researchers demonstrated the effectiveness of raxibacumab in three rabbit studies and one study involving monkeys. In the monkey study, the antibody allowed 64 percent of animals to survive exposure to anthrax. One rabbit study demonstrated that 82 percent of animals treated with the antibody and antibiotics survived anthrax exposure compared to 65 percent who received antibodies alone. The safety of the antibody was also evaluated in a human trial.

Raxibacumab was developed by the Biomedical Advanced Research and Development Authority and Human Genome Sciences, a Rockville, Md.-based company that has since been acquired by GlaxoSmithKline.