Anthrax Vaccine Nabs Orphan Drug Status

A drug that was originally approved in 1970 for the prevention of anthrax disease in persons at high risk of exposure to Bacillus anthracis, will, thanks to a newer indication, be protected by an Orphan Drug Designation status until 2022. The use of the drug for post-exposure prophylaxis (PEP) of disease following suspected or confirmed anthrax exposure (in combination with antibacterial drugs) makes the vaccine eligible for orphan drug exclusivity. According to FDA documents, the approval for the vaccine as a PEP occurred on Nov. 23, 2015.

BioThrax is the first vaccine approved through the Animal Rule, which is characterized by the use of animal studies in place of human trials when human trials are not ethically sound. The vaccine was tested in rabbits and monkeys. BioThrax is the only vaccine licensed for immunization and distribution in the United States for the treatment of anthrax exposure, and its Orphan Drug designation is to protect against anthrax disease (i.e., “For post-exposure prophylaxis of anthrax disease resulting from suspected or confirmed Bacillus anthracis exposure”). The Biomedical Advanced Research and Development Authority (BARDA) awarded a contract for the advanced research and development of BioThrax and for its label expansion as a PEP.

The Biomedical Advanced Research and Development Authority (BARDA) is funding other antianthrax drugs in development, including Elusys Therapeutics' monoclonal antibody, Anthim. On March 18, 2016, FDA approved Anthim (obiltoxaximab) injection to treat inhalational anthrax in combination with appropriate antibacterial drugs. It too has Orphan Drug status, and the status will protect the drug until 2023. The main difference between these drugs is that one is a monoclonal antibody, while the other is a vaccine. They would both feasibly be eligible for Orphan Drug status because of this difference, even though they treat the same condition. "Orphan-drug exclusivity protects only the approved indication or use of a designated drug. Exclusivity is not specific to the indication, but is specific to the drug product,” Miko B. Neri, senior director of corporate communications at Emergent BioSolutions, told this publication. "In our case, exclusivity means that no one can develop a biosimilar of BioThrax and get approval before the end of our 7-year exclusivity. Anthim is not a ‘biosimilar’ vaccine to BioThrax, so our products are not comparable."

Even another mAb in existence to treat anthrax disease (made by GlaxoSmithKline) has an orphan designation, according to an Elusys representative. "In terms of monoclonals, both raxibacumab and Anthim have orphan designation and essentially for the same indication. The reason both can have the designation is that we demonstrated that the products are not the 'same'."

Emergent focuses much of its efforts on medical countermeasures for for biological and chemical hazards. Its other biodefense candidates in the pipeline include a vaccine to protect against pandemic flu and another for the treatment of the Dengue virus.

Sources: Emergent BioSolutions, FDA