The Food and Drug Administration (FDA) has approved Anthim (obiltoxaximab; Elusys) injection for the treatment of inhalational anthrax due to Bacillus anthracis in combination with appropriate antibacterial agents, and for the prevention of inhalational anthrax when alternative therapies are not available or not appropriate.

Anthim is a monoclonal antibody that binds to the protective antigen (PA) portion of the anthrax toxin. Its toxin neutralizing activity blocks entry of anthrax toxin into susceptible cells, diminishing further spread of the toxin throughout the body.

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Anthim was approved under the FDA’s Animal Rule that allows efficacy data from adequate and well-controlled animal studies to support the approval when it is neither feasible nor ethical to conduct human efficacy trials. Its efficacy for prophylaxis and treatment of inhalational anthrax was shown in cynomolgus macaque and NZW rabbit model studies based on survival at the end of the studies. More animals in the Anthim treatment arm lived vs. animals in the placebo arm. Higher survival outcomes were seen when Anthim was given in combination with antibacterial agents (eg, levofloxacin, ciprofloxacin, doxycycline) vs. antibacterial therapy alone.

Anthim administered as a prophylactic led to higher survival outcomes vs. placebo in multiple studies when treatment was given at various doses and times.

The safety of Anthim was assessed in 320 healthy human volunteers and the most frequent adverse effects were headache, pruritus, upper respiratory tract infections, cough, nasal congestion, hives, bruising, and swelling and pain at the injection site.

Anthim was developed in conjunction with the U.S. Department of Health and Human Services’ Biomedical Advanced Research and Development Authority. It is available as single-dose vials intended for intravenous infusion.

“As preparedness is a cornerstone of any bioterrorism response, we are pleased to see continued efforts to develop treatments for anthrax,” said Edward Cox, M.D., M.P.H, director of the Office of Antimicrobial Products in FDA’s Center for Drug Evaluation and Research.

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