Shots - Health News
Wed August 21, 2013
Ebola Treatment Works In Monkeys, Even After Symptoms Appear
Originally published on Wed August 21, 2013 8:58 pm
Ebola, your days as one of the world's scariest diseases may be numbered.
A team of U.S. government researchers has shown that deadly Ebola hemorrhagic fever can be vanquished in monkeys by an experimental drug given up to five days after infection — even when symptoms have already developed.
An antibody cocktail aimed at Ebola's outer surface rescued three of seven macaques infected with lethal doses of the hemorrhagic virus in the U.S. Army's high-security labs at Fort Detrick, Md.
Looked at the other way, Ebola killed nearly 60 percent of the monkeys despite the experimental treatment. So there's still a long way to go before the infection can be reliably treated — in monkeys or humans.
Still, this experiment, whose results were published Wednesday in the journal Science Translational Medicine, marks the first time researchers have shown that Ebola can be successfully treated after the infection is well underway.
Earlier studies have shown that experimental drugs can prevent Ebola deaths when given a day or two after infection, before the onset of illness. Those experiments used either the same antibody cocktail or snippets of RNA that "silence," or turn off, the virus's replication machinery.
But that approach would be useful only in rare instances, such as when a lab accident exposes a researcher to Ebola and the time of the infection is known.
In the chaos of an Ebola outbreak — almost always deep in the jungles of countries, such as Uganda or the Democratic Republic of Congo — caregivers rarely know how many hours or days have passed since a person with fever or other early symptoms got the virus.
"You have a patient who walks into the clinic. He has a fever. You may know there's an Ebola outbreak," says microbiologist Gene Olinger, of the U.S. Army Medical Research Institute of Infectious Diseases, senior author of the report. "There's very little to rely on other than supportive care. Now we have demonstrated that we can provide protection — that our antibodies do provide protection."
Olinger says he is confident that the success rate with the monoclonal antibody cocktail, called MB-003, can be boosted by giving it in daily high doses after a fast, simple test has shown that a patient is infected with Ebola. In the current experiment, the antibody cocktail was infused in the monkeys three times over nine days at a relative low dose.
Unlike the rigorous laboratory test with macaques, caregivers in the midst of a human Ebola outbreak wouldn't necessarily wait until patients developed fever or other symptoms. They'd give the antibody drug as soon as a lab test revealed Ebola infection.
James Pettitt, the study's first author, says the next step will be to work with Canadian researchers, who have devised a different antibody cocktail, to work out the most effective recipe to test in additional monkeys, along with the best dose.
"The next step after that is to prove that the treatment is safe in humans," Pettitt tells Shots. "That phase can take anywhere from five to 10 years."
Also further downstream are projects to determine whether combinations of Ebola treatments might be more protective. Olinger says those might include one of several Ebola vaccines, now in development, which have been shown to prevent lethal disease in monkeys when given after virus exposure.
"Over the past decade [researchers] have developed three, four, maybe five vaccines that are now moving into preclinical and even clinical studies in humans," Olinger says.
Meanwhile, the MB-003 antibody cocktail could be used under a "dire emergency" exception if a laboratory worker got accidentally infected with Ebola.
There's another potentially important aspect about MB-003: It can be produced quickly and cheaply — for somewhere between $10 and $100 a dose — by putting the antibody genes into tobacco plants. This process has already been worked out by Mapp Biopharmaceutical, a San Diego company.
"In seven days, they can turn around hundreds of doses very effectively," Olinger says. That could come in handy when public health workers have a sudden, urgent need for a drug that will never have a big market.