Raxibacumab (ABthrax) is a human IgG1 monoclonal antibody against Bacillus anthracis protective antigen. HGS is currently providing stockpiles of the agent to the US government for use in the prevention and treatment of inhalation anthrax. As of May 2009, the candidate was undergoing review by the US Food and Drug Administration. The availability of bioterrorism countermeasures has become more important since the September 2001 anthrax attacks, and development of raxibacumab is a significant advance in this area.