FDA OKs Anthrasil for Inhalational Anthrax

Megan Brooks


March 25, 2015

The US Food and Drug Administration (FDA) has approved anthrax immune globulin intravenous (Anthrasil, Emergent BioSolutions) for treatment of inhalational anthrax in combination with appropriate antibacterial drugs.

Anthrasil is made from the plasma of individuals who have been immunized with Emergent's BioThrax (Anthrax Vaccine Adsorbed) vaccine, the only FDA-licensed vaccine for the prevention of anthrax disease, the company says in a news release.

Anthrasil was developed with support from the US Department of Health and Human Services' Biomedical Advanced Research and Development Authority (BARDA).

"Today's approval provides an important additional treatment to other FDA-approved therapies for inhalational anthrax, a life-threatening disease," Karen Midthun, MD, director of the FDA's Center for Biologics Evaluation and Research, said in a news release. "This product will be stored in US Strategic National Stockpile to facilitate its availability in response to an anthrax emergency."

Inhalational anthrax is a rare disease caused by exposure to infected animals or contaminated animal products or by an intentional release of anthrax spores. When inhaled, the anthrax bacteria replicate in the body and produce toxins that can cause massive and irreversible tissue injury and death, the FDA says.

To support the nation's preparedness against a possible anthrax attack, BARDA purchased Anthrasil under Project BioShield in 2011 as an experimental drug for the US Strategic National Stockpile. Because Anthrasil was not approved, its use before FDA approval would have required an emergency use authorization from the agency.

In animal tests, rabbits and monkeys were exposed to a lethal aerosolized dose of Bacillus anthracis spores, then treated with Anthrasil or a placebo. Survival in anthrax-infected monkeys treated with Anthrasil ranged from 36% to 70% compared with 0% survival in the placebo group, with a trend toward increased survival at higher doses of Anthrasil, the FDA said.

Rabbits treated with a moderate dose of Anthrasil after infection exhibited 26% survival compared with 2% survival with placebo. In a separate study in rabbits, the combination of Anthrasil and antibiotics resulted in 71% survival compared with 25% survival in animals treated with antibiotics alone.

"The results of studies in research animals provided sufficient evidence that Anthrasil is reasonably likely to benefit humans with inhalational anthrax," the FDA said. The safety of Anthrasil was tested in 74 healthy human volunteers. The most common adverse effects were headache, back pain, nausea, and infusion site pain and swelling.


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