FRIDAY, Aug. 29, 2014 (HealthDay News) -- An experimental Ebola drug previously given to two American aid workers successfully cured a group of monkeys infected with the deadly virus in laboratory tests, researchers report.
The drug, ZMapp, prompted recovery in all 18 monkeys who received it, even if they didn't get the medication until five days after infection.
ZMapp even cured monkeys with advanced cases of Ebola who were days or even hours away from death, said study senior author Gary Kobinger, chief of special pathogens for the Public Health Agency of Canada.
"The level of improvement was beyond my own expectations," Kobinger said, noting that the drug cleared the liver damage, excessive bleeding and horrible rashes that are the hallmarks of Ebola infection.
This study provides some scientific evidence for the effectiveness of ZMapp, which aid workers Dr. Kent Brantly and Nancy Writebol both received under "compassionate use" guidelines after contracting Ebola while in Liberia fighting the current outbreak in West Africa.
Brantly and Writebol successfully fended off the virus. They were flown home for treatment in the United States, and last week were released from hospital care in Atlanta.
The results of the monkey trial were published Aug. 29 in the journal Nature.
Because Brantly and Writebol were given ZMapp outside of a clinical trial, physicians and public health officials have been reluctant to fully credit the drug with their recovery. Further clouding the picture, a Liberian doctor and a Spanish priest subsequently died from Ebola despite receiving the drug.
"We hope that initial safety testing in humans will be undertaken soon, preferably within the next few months, to enable the compassionate use of ZMapp as soon as possible," the researchers concluded in their paper.
The West Africa outbreak is the largest ever for Ebola, with 3,069 infected and 1,552 dead. The World Health Organization (WHO) estimates that more than 20,000 people could become infected before the end of the outbreak.
In the face of this health-care crisis, a WHO expert panel ruled earlier this month that it would be ethical to treat Ebola patients with experimental medications like ZMapp.
"Given the severity of this condition and the fact that there's nothing else available, this is as good as it gets," Dr. Ambreen Khalil, an infectious disease specialist with Staten Island University Hospital in New York City, said of the results from the ZMapp monkey trial. "Our focus should be now on the people who are rapidly dying in Africa. In those patients, ZMapp should be used, based on this study."
ZMapp is a cocktail of three laboratory-produced antibodies, which have been derived from two previous antibody cocktails for Ebola, Kobinger said.
In the study, researchers infected 21 rhesus monkeys with an Ebola strain similar to the one raging through West Africa. Then they administered ZMapp to 18 of the monkeys starting on days three, four or five after infection. The monkeys received three doses of the drug at three-day intervals.
All 18 animals treated with ZMapp survived, regardless of how sick they had become. The three monkeys not treated with ZMapp all died by day eight.
Because the Ebola virus strain used to infect monkeys in this experiment is different to the strain in the current West African outbreak, the researchers also performed lab tests that showed that ZMapp does bind to the new virus strain and would likely be as effective against it, Kobinger said.
ZMapp is the only experimental treatment that has been deployed against Ebola during this outbreak, but others could be on the way.
The U.S. National Institutes of Health and drug manufacturer GlaxoSmithKline are expected to announce that they are starting the first human trials of a potential Ebola vaccine, NBC News reported Wednesday.
For more on the Ebola virus, visit the U.S. Centers for Disease Control and Prevention.