FDA Approves Inhalational Anthrax Treatment

Anthrax spores (U.S. Food and Drug Administration)

25 March 2015. The U.S. Food and Drug Administration today approved a treatment for inhalational anthrax, a rare but dangerous respiratory condition that can result from a bioterrorist attack. The drug is marketed as Anthrasil by Emergent BioSolutions Inc. in Gaithersburg, Maryland.

Anthrax is caused by Bacillus anthracis, bacteria found naturally in soil and commonly affecting domestic and wild animals. Humans can become ill when exposed to contaminated animals or if anthrax spores are released intentionally. When inhaled, anthrax spores reproduce in the body, producing toxins that can cause widespread and irreversible tissue damage, often leading to death.

The U.S. in recent history experienced a terrorist attack from anthrax spores, making it far from a hypothetical issue. When purified and made into a fine powder or aerosol, anthrax can be distributed and spread easily through the air. Letters with anthrax powder sent through the mail in 2001 caused 22 people to become ill, including 12 mail handlers, leading to 5 deaths.

Anthrasil, previously called Aigiv, is a solution of purified human immune globulin G with antibodies that target the toxins produced by anthrax bacterial spores. The drug is made from plasma collected from healthy donors who were immunized with BioThrax, also produced by Emergent, an FDA-approved vaccine to prevent anthrax.

Emergent tested the drug’s safety and chemical activity in the body in an early-stage clinical trial, but relied on animal studies to test for efficacy. FDA allows for animal studies when human clinical trials are not feasible or ethical. Tests with lethal aerosol doses of anthrax spores on rabbits and monkeys showed much higher survival of animals receiving the drug compared to a placebo, with higher survival rates among animals receiving larger doses.

Anthrasil was developed under a $160 million contract to contract to Biomedical Advanced Research and Development Authority, or Barda, a division of the Department of Health and Human Services. Barda previously stockpiled Anthrasil as an experimental drug, but would have required an emergency authorization from FDA to use the drug before today’s approval. The company says approval by FDA makes it eligible for a $7 million milestone payment from the agency.

The drug also received Orphan Drug designation, and as a result of its approval by FDA, Anthrasil qualifies for 7 years of market exclusivity. In addition, Emergent is collecting anti-anthrax human plasma needed to produce Anthrasil under a $63 million Barda contract awarded in 2013.

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