The US Food and Drug Administration (FDA) on Wednesday finalized guidance on developing drugs to protect against inhalation anthrax.
The guidance finalizes a draft released in 2016 and has been updated to revise the indication of prophylaxis of inhalation anthrax to cover both the pre- and post-exposure settings.
The indication now reads "to reduce the risk of disease in persons who have inhaled, or are likely to imminently inhale, aerosolized B. anthracis
spores, but who do not yet have the established disease."
FDA says the change in the indication was made to reduce the risk of illness and death for first responders and others who may come into contact with anthrax spores as part of an emergency response to an attack or outbreak.
"We now know that a comprehensive preparedness plan for potential anthrax threats must account for both pre- and post-exposure scenarios. That's why the FDA has taken steps to modernize its guidance on inhalational anthrax to advance the development of new drugs for prophylaxis prior to exposure," said FDA Commissioner Scott Gottlieb.
Previously, FDA approved
products to treat anthrax and provide post-exposure prophylaxis for inhalation anthrax, but those products were not labeled for pre-exposure use.
However, FDA says that most drugs being considered for prophylactic use against anthrax are existing antibiotics that have been tested and approved for other indications and that it is unlikely that an investigational drug being developed solely to treat anthrax will be approved for prophylactic use.
"An indication for prophylaxis of inhalational anthrax is likely to be reserved almost exclusively for antibacterial drugs that have established uses and safety data in other infectious diseases," FDA writes.
The final guidance also clarifies that drugs developed for prophylactic use against anthrax will be considered for approval under the animal rule, which allows the agency to approve products based on studies done in relevant animal models when studies in humans would be unethical or infeasible to conduct.
"Definitive human efficacy studies cannot be conducted because naturally occurring inhalational anthrax is extremely rare and it would be unethical to deliberately expose healthy human volunteers to B. anthracis
spores; thus, as previously noted, drugs developed for prophylaxis of inhalational anthrax should be developed for approval consideration under the animal rule," FDA writes.
FDA also says the guidance has been updated for consistency with its 2015 guidance Product Development Under the Animal Rule
The guidance goes on to detail the agency's specific expectations for conducting animal studies, as well as considerations for safety studies, clinical pharmacology and microbiology testing.