The experimental drug ZMapp cured the animals even when administered five days after infection – by which time they were displaying severe symptoms.
What did these tests involve?
The drug was given to 18 rhesus macaques which had been infected with the Ebola virus. All of these monkeys made a complete recovery. However, three other macaques which were left untreated as a control became seriously ill and soon died.
The treated monkeys were exposed to a lethal level of Ebola virus before receiving three doses of ZMapp starting three, four and five days after infection.
The treatment reversed Ebola symptoms including excessive bleeding, rashes, and liver damage. Three weeks after they were infected, no trace of the virus could be detected in the animals’ blood.
The untreated monkeys all succumbed to the virus by day eight after infection.
“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,” wrote a team of scientists led by Dr Gary Kobinger, from the Public Health Agency of Canada.
When can we use it on humans?
The drug has already been used on humans, though until now we had even less idea about how effective it was.
Two US doctors given the drug after they were infected with Ebola while working in Liberia subsequently recovered.
But it is not known whether they were saved by the drug or just lucky. About 45% of those infected in the current outbreak have survived without treatment.
At least two other patients treated with ZMapp have since died. Experts are hoping that this was because help got to them too late, and not because the drug doesn’t work that well.
One drawback of the research was that it used a version of the virus different from the strain responsible for the current outbreak, which was first identified in Guinea in March. This particular strain was not available for testing at the time.
However, scientists have since gone on to show that ZMapp blocks replication of the Guinea strain in laboratory tests.
What’s so special about ZMapp?
Well to begin with there’s nothing else out there that comes close to controlling Ebola. ZMapp is a blend of three laboratory-made antibodies designed to neutralise the virus.
The scientists involved in the studies agreed that the drug is the best bet we’ve got: “ZMapp exceeds the efficacy of any other therapeutics described so far, and results warrant further development of this cocktail for clinical use .”
What kind of scenario are we facing without an effective drug?
The news follows a warning from the World Health Organisation (WHO) that the Ebola outbreak in West Africa could eventually claim more than 20,000 victims.
Latest figures show 1,552 deaths from the 3,069 cases reported so far.
Ebola – which belongs to the family of “filoviruses” – ranks alongside Marburg virus as one of the world’s deadliest infections. And although this strain seems to claim around 45% of its victims, fatality rates in previous outbreaks have been as high as 90%.
How have experts reacted to ZMapp?
Professor Martin Hibberd, from the London School of Hygiene & Tropical Medicine, said: ”This looks to be a very well designed study with better than expected results, which give great hope for future clinical trials.
“I hope the team can receive sufficient funding to undertake these clinical trials straight away as this is by far the most advanced potential treatment option available to my knowledge.”