Before revision: The FDA animal efficacy rule (also known as animal rule) applies to development and testing of drugs and biologicals to reduce or prevent serious / life-threatening conditions caused by exposure to lethal or permanently disabling toxic agents (chemical, biological, radiological, or nuclear substances), where human efficacy trials are not feasible or ethical.
After revision: The FDA animal efficacy rule (also known as animal rule) applies to development and testing of drugs and biologicals to reduce or prevent serious or life-threatening conditions caused by exposure to lethal or permanently disabling toxic agents (chemical, biological, radiological, or nuclear substances), where human efficacy trials are not feasible or ethical.