Experimental Ebola treatments are moving with lightning speed through a regulatory process that, for most drugs, can take years. The urgency of the lethal epidemic in three West African countries - Guinea, Liberia and Sierra Leone - means a number of promising treatments are bypassing the usual hurdles toward approval.
Before a new drug gets the green light from U.S. regulators, researchers are required to conduct in-depth clinical trials on people to demonstrate the experimental compound is both safe and effective. Drug trials typically involve thousands of people and can take many years to complete.
The U.S. Food and Drug Administration’s so-called “animal rule,” however, allows researchers to gain expedited approval when faced with a deadly pathogen like Ebola, according to Thomas Geisbert, a microbiologist at the University of Texas medical branch in Galveston.
Geisbert helped develop what’s known as the VSV Ebola vaccine, which this week moved to human clinical trials in 20 healthy volunteers at Walter Reed Army Institute of Research in Maryland.
The animal rule, according to Geisbert, requires only that scientists demonstrate that a compound is effective in an animal model of human disease, in this case monkeys.
"And then in conjunction with that, you do a conventional phase one trial," Geisbert said. "That’s just a study where you put a vaccine or treatment into a healthy human volunteer just to make sure that you know in normal, healthy people that your vaccine or drug does not cause any disease or serious adverse event."
The United States adopted the animal rule shortly after September 11, 2001, in the event of a bioweapons attack by terrorists. The current Ebola epidemic is the largest, and deadliest, since the virus was identified in the mid-1970s.
An experimental drug, zMapp, went straight from the laboratory to the bedside, even bypassing human safety trials to treat a handful of Ebola patients in the U.S.
Besides the VSV trial being carried out by Canadian researchers, another promising vaccine candidate, manufactured by British drug manufacturer GlaxoSmithKline, is undergoing safety trials in Mali. That country borders Guinea, the epicenter of the Ebola epidemic that has now claimed 4,000 lives in West Africa.
So far, no cases of Ebola have been reported in Mali.
Both vaccines proved to be 100 percent effective in protecting monkeys against infection with the Ebola virus, without side effects.
Expedited clinical trials also mean researchers may dispense with the usual protocol of giving a group of participants a placebo, or inactive substance, so researchers can study a drug’s effectiveness.
The Ebola virus carries a 90 percent mortality rate. Bioethicists say it would be unethical to give a fake drug to people infected with the lethal pathogen.
Double-blind placebo controlled trials, as they are called, are considered the gold standard in determining whether a drug works.
In the case of treatments for Ebola, Geisbert said that is yet to be determined, because what works in animals does not necessarily work in humans.
“I mean, we don’t know if any of these vaccines is going to work in humans, quite honestly,” said Geisbert.
Canadian health officials hope to have initial results of their VSV vaccine trials in Maryland by December and to move to clinical safety trials in Africa shortly after that, most likely in health care workers treating Ebola patients. They are at greatest risk of infection, according to public health officials.
Geisbert said the vaccines, in particular the VSV, not only have the potential to prevent Ebola, but can also be used to treat the disease soon after exposure.