Science
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Since March, the Ebola virus has killed at least 932 people in West Africa, the deadliest ever outbreak of the disease, and as the lethal hemorrhagic fever continues its spread, governments are taking drastic measures — from quarantining villages to closing schools — to stem the epidemic.
But perhaps there could have been another option to fight the virus. More than four years ago, a team of U.S. government scientists developed vaccine candidates that shielded monkeys from multiple strains of Ebola. Those vaccines, however, were never tested in human clinical trials — and not because the science wasn’t promising. One small trial on the monkeys, for example, had a 100 percent success rate of protecting the animals from the disease.
The factor preventing such trials in humans, though, has been cost, said Dr. Daniel Bausch, an associate professor of tropical medicine at the Tulane University School of Public Health who is currently stationed at the U.S. Naval Medical Research Unit 6 in Lima, Peru.
That’s because, while the National Institutes of Health and the U.S. government often fund the early animal safety and efficacy testing of a vaccine, pharmaceutical companies typically fund the human clinical trials to take a drug or vaccine to market.
“When you have a population or situation with Ebola where it only sporadically occurs, and it occurs really in the world’s poorest populations, it’s not exactly an attractive candidate for the pharmaceutical industry on the economic side,” Bausch said. “We have good vaccine candidates, and some good drug candidates that have gone through fairly extensive testing for Ebola, and at least reduce the mortality rate in monkeys.”
With this latest outbreak, the development of one experimental Ebola vaccine is being fast-tracked, according to National Institute of Allergy and Infectious Diseases director Anthony Fauci, and human clinical trials are slated to kick off in September. Nonetheless, it could be years before its safety and effectiveness in humans is firmly established.
Another challenge of coming up with a vaccine to treat a deadly virus like Ebola is that researchers can’t easily — or ethically — test it on humans, according to Nancy Sullivan, chief of the Biodefense Research Section of NIAID’s Vaccine Research Center, and who in 2010 led the team that created an experimental vaccine that protected monkeys against two lethal strains of Ebola.
“We obviously can’t expose people to the Ebola virus” in order to know whether a vaccine is effective, Sullivan said. The alternative is to vaccinate high-risk human populations as a means of testing such a drug. But that’s also problematic because Ebola outbreaks are so sporadic and hard to predict — “unless we vaccinate all of Africa, which isn’t feasible,” she said.
Instead, scientists use what's known as the FDA's "animal rule," in which the efficacy of a vaccine is tested on animals, and that data is used to prove it could be safely used in humans. So far, just a few treatments have been approved using that rule, such as treatments for botulism and anthrax exposure.
In terms of the experimental Ebola treatment taken by two U.S. aid workers who contracted the virus caring for Ebola patients in Liberia, normally the U.S. Food and Drug Administration (FDA) would have to sign off on administering a drug it hasn’t approved for human use.
But this treatment, which is called ZMapp — a cocktail of two drugs that showed promise treating monkeys infected with Ebola — was given to Dr. Kent Brantly and missionary aid worker Nancy Writebol while they were still in Liberia. Samaritan’s Purse, the international aid organization Brantly was working with, contacted the Centers for Disease Control and Prevention (CDC) seeking experimental drugs, after which an NIH scientist in Liberia directed the group to the biotechnology companies currently developing treatments, according to NIAID. Both Brantly and Writebol gave their informed consent that they understood the risks of taking a treatment that had never been used in humans, CNN reported Monday.
ZMapp is a cocktail of what are called monoclonal antibodies, which bind to the virus to inactivate it. The antibodies were developed in the cells of tobacco plants by Kentucky Bioprocessing, which is owned by tobacco giant Reynolds American.
Mapp Biopharmaceutical said in a statement that "very little of the drug is currently available" because its safety has yet to be tested in humans, but the company's commercialization arm is reportedly working to produce more of the experimental serum.
On Wednesday, three of the world's top Ebola specialists — including Peter Piot, one of the scientists who discovered the virus back in 1976 — called for experimental drugs and vaccines to be offered to people in West Africa, too.
"African governments should be allowed to make informed decisions about whether or not to use these products — for example to protect and treat healthcare workers who run especially high risks of infection," wrote Piot, director of the London School of Hygiene and Tropical Medicine; Jeremy Farrar, a tropical medicine and global health professor at Oxford University; and David Heymann, head of the Center on Global Health Security at the U.K.-based Chatham House, in a joint statement.
And in a sign of the urgency to contain Ebola in West Africa, the World Health Organization said Wednesday afternoon that it would convene a panel of medical ethicists next week to explore the use of the experimental treatment in Guinea, Sierra Leone, Liberia and Nigeria.
Brantly and Writebol aside, Bausch said it's rare that any patient would be given a drug that had never been tested in humans.
There are a few precedents of circumventing the FDA approvals process, which normally requires extensive human clinical trials.
For example, in what’s known as compassionate use, the FDA considers the individual cases of patients who are terminally ill but haven’t been able to qualify for access to an experimental drug through a clinical trial.
And in some other instances, the FDA has approved certain uses of medicines to combat threats of bioterrorism, according to Jonathan Moreno, a bioethics expert and professor at University of Pennsylvania’s Perelman School of Medicine. For example, he helped the FDA weigh in on the approval of the use of ciprofloxacin hydrochloride — commonly referred to as Cipro — for cases of inhalation anthrax. Even though the drug hadn’t been tested in humans for that use, the government wanted it available in case of bioterrorism threats — and in 2001, it was prescribed to the people who worked for the news agencies and government officials whose offices were mailed anthrax-laced letters following the Sept. 11 attacks.
There was also the anthrax vaccine, which was given to approximately 150,000 U.S. soldiers departing for the first Gulf War to protect them from inhalation anthrax from Saddam Hussein's alleged weaponized arsenal. The FDA, however, had only approved it for use against anthrax acquired through contact with the skin. After Iraq war veterans complained of long-lasting fatigue and joint paint, some researchers blamed the FDA for poorly reviewing the vaccine’s safety.
The process of testing experimental treatments during epidemics or other public health threats can be dicey, Moreno said, and involves careful government collaboration with health and community advocates who can help orchestrate trials where participants are well-informed.
“You have to go where the disease is, and often that’s in poorer communities,” he said. “And there’s no magic bullet for a problem like that.”
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Governments have ordered quarantines but dense geography and fear of health care workers has hampered efforts
The deadly virus with no known cure has been infecting mainly Africans in several outbreaks since 1976
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