We may have just found an easy-to-swallow cure for one of the deadliest diseases out there. In research released this month, scientists report that a single dose of an experimental pill dramatically reduced the high fatality rate of Ebola infection, at least in nonhuman primates.
Researchers at the University of Texas Medical Branch led the study, published Friday in the journal Science Advances. The treatment, an oral antiviral called obeldesivir, prevented up to 100% of deaths in monkeys given a high dose of the deadliest species of Ebola. These findings and others suggest that obeldesivir can become a highly effective measure against Ebola and similar infections that can quickly lead to massive bleeding and death, the researchers say.
Ebola is caused by several related strains of viruses (formally called orthoebolaviruses). The most commonly seen and deadliest version of Ebola is caused by the Zaire ebolavirus (named after where it was first discovered), which can have a fatality rate as high as 90% if untreated.
Symptoms of Ebola initially include fever, aches, and other flu-like symptoms, but the infection can rapidly progress and cause widespread organ damage and heavy internal bleeding that seeps out of people’s bodies, which is known as hemorrhagic fever.
Ebola is a zoonotic disease, meaning outbreaks typically begin when a person is exposed to infected animals (African fruit bats are thought to be a primary reservoir). But it can also spread between people through close contact with bodily fluids, including blood and semen. While the rapid progression of symptoms and high lethality of Ebola often prevent the infection from spreading widely, it has occasionally sparked large-scale outbreaks. During 2014 to 2016, for instance, a Zaire ebolavirus outbreak in West Africa infected almost 30,000 people and killed more than 11,000. No outbreaks since have reached that level of destruction, but Ebola and related hemorrhagic viruses continue to be a grave public health threat in the countries where they’re natively found.
Nowadays, there are effective approved vaccines and treatments for some species of Ebola. But the vaccine supply is limited and the current antibody-based treatments have to be stored in cold conditions and taken intravenously, limiting their availability and usefulness. So the UTMB researchers believe that obeldesivir—an oral version of the antiviral remdesivir, originally developed to treat covid-19—can represent a pivotal step forward in Ebola treatment.
In their new study, they gave cynomolgus and rhesus macaques a lethal dose of a variant of Zaire ebolavirus, then gave them obeldesivir a day after infection. Incredibly, 100% of rhesus macaques given obeldesivir survived their infection, while 80% of cynomolgus macaques did as well. The treatment delayed the virus’ ability to replicate and even seemed to promote the monkeys’ adaptive, or antibody-based, immune response to it.
The team’s earlier work with monkeys has already found that obeldesivir might be effective against Sudan virus, the second most commonly encountered species of Ebola. Earlier this January, the researchers also found that obeldesivir could protect monkeys from Marburg, another deadly cousin of Ebola (a recently ended outbreak of Marburg killed at least 10 people in Tanzania this year).
More research will be needed to validate the drug’s potential against Ebola in humans, of course. But the researchers are hopeful that obeldesivir can become a broadly applied and more convenient weapon against these deadly infections.
“For outbreak response, oral antivirals might present substantial advantages over now approved intravenous drugs, such as easy supply, storage, distribution, and administration,” they wrote in their paper.