In 2002, in the aftermath of the 9/11 attacks, the US introduced the 'animal rule' as a way for the country's regulators to approve medical countermeasures to chemical, biological and radiological weapons in instances where conducting human efficacy studies would be unethical or unfeasible. In the rule's first ten years, the US Food and Drug Administration (FDA) has used the provision to approve vitamin B12 injections for cyanide poisoning, an enzyme-blocking pill for nerve gas exposure and a broad-spectrum antibiotic to treat plague. Notably, in all of these cases the drugs had already received FDA approval for other afflictions or had previously received a green light in other countries for use against deadly chemicals.
Now, in a regulatory first, on 14 December the FDA cleared a completely novel product through the animal rule without any such prior approvals: an antibody drug called raxibacumab for the treatment or prevention of respiratory anthrax, caused by inhalation of the bacterium Bacillus anthracis. In fact, although the safety of raxibacumab was demonstrated in more than 300 healthy human volunteers, the only validated efficacy studies available to the FDA were in monkeys and rabbits.
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