In a newly published article, the Winnipeg-based scientists reported that their combination therapy saved three of four cynomolgus macaques and four of four rhesus macaques when it was given three days after the animals were infected with Ebola Zaire, the deadliest strain.
The scientists hope to test the drug cocktail in humans beginning in late 2014 or early 2015, if they can get approval from Canadian and U.S. drug regulators.
The work builds on earlier research which showed a cocktail of three cloned antibodies saved four of four primates when given 24 hours after infection and two of four treated 48 hours after infection.
This time the researchers added interferon-alpha, a chemical made by the immune system, to the treatment regime.
Two of four primates survived when they were given the chemical one day after infection, and then the antibody cocktail four days later.
In order for a treatment to be useful against the five types of Ebola viruses or their cousin, the Marburg virus, it must be something that can enhance survival when given days after infection, which is when cases would typically come to light.
"The concept of combining different treatments to improve efficacy and extend the treatment window is certainly interesting and the data look promising," Tom Geisbert, an expert in viral hemorrhagic fevers, said of the work. Geisbert is a researcher at the University of Texas Medical Branch in Galveston.
The senior author of the study is Gary Kobinger, head of the special pathogens program at the Winnipeg lab. The laboratory is part of the Public Health Agency of Canada.
He said in an interview that the aim of this work is to find a way to put a lid on the infection, to give the immune system a chance to fight it off.
"The immune system is very efficient. It will clear the virus — it just never has the time to do it," Kobinger said.
He said in conjunction with two biotech companies — Defyrus, a Canadian firm, and Mapp Biopharmaceuticals from the U.S. — the group hopes to conduct a Phase I trial in people. That type of study doesn't determine if the treatment can cure infection; it simply shows that the therapy can be safely given to people.
Kobinger said the World Health Organization would like to be able to stockpile drugs for Ebola and Marburg infections so they could deploy them when one of the rare but deadly outbreaks of these diseases emerge.