This is a little humorous in stating clinical trials are not possible for humans, of course not for a drug like this. There were over 300 volunteers who took the drug that did not have Anthrax exposure to test the safety of the drug with side effects, etc. BD
For the first time, the agency has approved a monoclonal antibody to treat an infection under the FDA's Animal Efficacy Rule. A monoclonal antibody is a protein that resembles a human antibody that identifies and neutralizes foreign bodies like bacteria and viruses.
The approval came after controlled studies were conducted on animals. This is because anthrax is a rare, lethal disease and it is not possible to conduct drug trials on human test subjects.