Licensure under the FDA Animal Rule: A Path to Success

By HyunJung (Henry) Kim

Michael Merchlinsky, a subject matter expert from BARDA/CBRN, was the first speaker in this ASM Biothreats 2017 plenary session, overviewing history of the Animal Rule in the US. The Animal Rule is well-known as an innovative policy forming the foundation of U.S. biodefense policies. When no alternatives are available, the Animal Rule provides an investigational mechanism for figuring out “predictive” responses from new medical countermeasures (MCMs) relevant to calculating a dose in humans. Under the Animal Rule, licensure is a legal status awarded by FDA that assures the public that studies to demonstrate safety and efficacy have been performed. According to Merchlinsky’s presentation, it is worthy to note that the Animal Rule was born in the basis of national security purposes, increasingly apparent from Gulf War to 9/11. The primary purpose of the Animal Rule is to increase preparedness and provide means to confidently respond to a public health emergency. Based on the national security perspective at the state-level, Michael Merchlinsky reviews the pros and cons of the Animal Rule. He notes that the Animal Rule is the best course of action for assuring ‘safety’ and ‘efficacy’ where no other alternative is available. Moreover, MCMs under the Animal Rule can attain pre-EUA status during developmental path-MCMs saved in the Strategic National Stockpile (SNS). On the other hand, a critical limitation is that the Animal Rule is inherently longer, harder, and less predictive than traditional pathways.

Next, Dr. Mario Skiadopoulos and Christine Hall represented Emergent BioSolutions and spoke to the regulatory pathway for anthrax and botulism medical countermeasures. BioSolutions applies animal models based on the subject of rabbits as well as non-human primate (NHP) to develop vaccines against anthrax and botulism. It was very interesting to know that there are three types of experiments in animal modeling; Post-Exposure Prophylaxis (PEP), Pre-Exposure Prophylaxis (PrEP) and Passive Transfer. The PEP type demonstrates added value of vaccine over antibiotics alone, in post-exposure settings, whereas the PrEP type established correlation between pre-challenge TNA tilter and probability of survival. The Passive Transfer type demonstrates that neutralizing antibody alone is capable of protection. Compared with the speaker from government sector, speakers from the private sector point to more practical challenges that field researchers are facing under the Animal Rule. They argue that there is no regulatory precedent for licensing a vaccine under the Animal Rule. Technically speaking, it is not clear which time points or which kind of animal models can bridge animal-to-human data. For instance, we have never known which animal model is akin to human trials between rabbits and NHP, as well as which time point is appropriate to apply to humans among the 80%, 90% or 100% survival points from the result of animal models. Consequently, the Animal Rule is essential not only in MCMs development and the realm of national security, but also carries with it many challenges both in government and private sectors. Overall, the inclusion of both government and private sector viewpoints presented the full spectrum of the Animal Rule and its complexities regarding MCM development.

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