Medarex Inc announced that its fully human antibody against anthrax, MDX-1303, protected against inhalation anthrax at a dose ten-fold lower than previously tested in rabbits treated with the antibody, and that MDX-1303 reduced mortality even when administered 1-2 days after inhalation, once animals displayed signs suggestive of disease.

These results are being presented today at the Biodefense Funding and Development Opportunities on Vaccines, Therapeutics & Diagnostics Conference in Washington, D.C.

The pre-clinical study was conducted by an independent party and was designed to determine the minimal amount of MDX-1303 required to provide protection and to determine the therapeutic activity of the antibody given at the time of anthrax inhalation. The results indicated that all doses tested were protective in rabbits exposed to lethal doses of anthrax spores by inhalation. The results also demonstrated that administration of MDX-1303 to rabbits 24 or 48 hours after exposure to anthrax could result in recovery and survival of the animals without the addition of antibiotics. These results suggest that the MDX-1303 antibody has the potential to be developed both as a prophylactic to protect patients at risk of exposure to anthrax and as a therapeutic for patients already showing signs and symptoms of anthrax infection.

The pre-clinical study, under a Cooperative Research and Development Agreement with the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) and Dartmouth Medical School, was conducted at a separate, specially equipped facility in the Midwest.