An experimental Canadian-made Ebola drug used to treat monkeys has been shown to reverse the virus in the infected primates.
The research paper published online in the journal on Friday shows the drug, called ZMapp, resulted in 100 per cent recovery in the 18 monkeys tested.
The drug, developed at the Public Health Agency of Canada's National Microbiology Laboratory in Winnipeg, was credited with helping two American aid workers who were infected with Ebola in Liberia. They both have since recovered from the virus.
The experimental drug requires safety testing in humans, but the researchers said the drug could be a promising option for treating the ongoing Ebola outbreak that has killed more than 1,500 people in Western Africa.
"We of course expected an improvement. We were at least hoping for it. But the level of improvement was at least beyond my own expectations," lead Canadian researcher Dr. Gary Kobingera said in teleconference Friday.
The researchers reported that three doses of ZMapp, administered at three-day intervals beginning on the third, fourth or fifth day after monkeys were infected with Ebola, resulted in the survival of all 18 animals.
The treatment reversed severe Ebola symptoms such as excessive bleeding and rashes.
The three monkeys that did not receive ZMapp all died of the Ebola virus by day eight.
Scientists have been working for years on drugs to prevent or treat Ebola. But most of the work to date has focused on giving the therapy almost immediately after monkeys are injected with the virus.
That scenario mirrors what happens in humans when there is a laboratory accident involving Ebola. But during Ebola outbreaks, people do not seek care until they are sick, and that is typically days into an infection.
"Early studies were relatively artificial and oriented more towards laboratory accidents where you injected a monkey with a bunch of Ebola virus and then 30 minutes later you gave it a vaccine or a compound. And of course it has very little replicating virus so it's not that hard at that point to inactivate that," explained Dr. Daniel Bausch, an Ebola expert at Tulane University School of Public Health and Tropical Medicine in New Orleans, La.
"And so this is the study so far when they've been able to push it out to the farthest time point when an animal is sick and has a high level of viremia (virus in the blood). ... And so that's a very promising result."
The Ebola virus strain used to infect monkeys in the experiment is different than the strain in the current West Africa outbreak. However, the authors noted that they studied the two strains and concluded that ZMapp can prevent replication of the Ebola strain in Africa.
Currently, there are no more doses of ZMapp available.
Kobinger said he believes 20 to 40 doses of the drug can be made in a month, when production is up and running. The antibodies are grown in tobacco plants.
Kobinger said a phase 1 clinical trial -- which is designed to show that the drug is safe for use in humans -- will begin in early 2015. That work will be led by Mapp BioPharmaceuticals, which has licensed the drug and will push it through the regulatory process.
