Efficient neutralization of antibody-resistant forms of anthrax toxin by a soluble receptor decoy inhibitor.

A soluble receptor decoy inhibitor (RDI), comprised of the extracellular I domain of ANTXR2, is a candidate anthrax therapeutic. Here we show that RDI can effectively neutralize altered forms of the protective antigen toxin subunit that are resistant to 14B7 monoclonal antibody neutralization. These data highlight the potential of RDI to act as an adjunct to existing antibody-based therapies and indicate that inhibitors based on RDI might be useful as a stand-alone treatment against specifically engineered strains of Bacillus anthracis.