WASHINGTON, Aug. 20 (Xinhua) -- Researchers from the U.S. and Canada said Wednesday they have successfully used an experimental drug to save the lives of monkeys with Marburg virus, a deadly virus closely related to Ebola virus that killed over 1,200 in West Africa this year.
The treatment, described in the U.S. journal Science Translational Medicine, was shown to be effective at a point when the animals have detectable levels of the virus in their system and begin to show symptoms of the disease.
Marburg and Ebola viruses belong to the family of filoviruses and often cause fatal hemorrhagic fevers. Currently, no vaccines or drugs have been approved for human use to treat these devastating infections.
Previous studies in non-human primates have been limited to treatment shortly after exposure, before symptoms appear.
In the new study, researchers from the University of Texas and Canada-based Tekmira Pharmaceuticals treated macaques infected with Marburg-Angola, the most severe strain of Marburg virus with a mortality rate of up to 90 percent, over a range of times from shortly after infection up to three days after exposure, when symptoms have already appeared.
Their strategy centered on small interfering RNAs known as siRNAs, which were encapsulated in lipid nanoparticles to aid therapeutic delivery to target cells to block replication of the Marburg virus.
All 16 macaques that received the siRNA drug survived, while all of the control animals died between days seven and nine, the researchers reported.
"We demonstrate the ability to completely protect non-human primates against the lethal Marburg Angola virus challenge even when treatment is delayed until day three at a time when we can detect viremia at the onset of disease, showing real world utility of this technology," said senior author Thomas Geisbert professor of microbiology and immunology at the University of Texas.
"The siRNAs have been designed to protect against all known strains of Marburg virus, meaning that the approach has broad spectrum potential in terms of at least protecting against all of the different strains of Marburg," he added.
The researchers have previously shown this drug's ability to prevent Marburg-infected guinea pigs from dying.
Other studies have shown that siRNAs can confer protection against Ebola virus in monkeys when given up to 48 hours after infection.
"This technology may have potential for combating Ebola," Geisbert said.
The researchers next planned to see how much further they can delay the initiation of treatment for both Marburg hemorrhagic fever and Ebola hemorrhagic fever.