They are running out of time. Scientists in the Democratic Republic of the Congo and Uganda are scrambling to trial experimental drugs and vaccines. The target is Ebola Bundibugyo, a rare variant spreading fast. No approved treatments exist for it. No approved vaccines.
As of 17 May, US CDC data shows 336 suspected cases. 88 people have died.
A World Health Organization-sponsored trial is pending. It waits for green lights from the governments of the DRC and Uganda. They want to test two things: treatments, and possibly an existing vaccine meant for a different Ebola species.
Speed over precision
“I think we’re in a really good spot to launch these trials fast,” says Amanda Rojek. She works at the University of Oxford. Part of the WHO team. Working day and night.
Rojek focuses on two investigational therapies. Both aim at filoviruses—the family including Ebola and Marburg.
First is remdesivir. Made by Gilead in California. A broad-acting antiviral. We’ve seen it before. Tested against Zaire Ebola in the 2018-19 outbreak. Used against SARS-CoV-2 with modest results during the pandemic. Not a miracle cure, but familiar ground.
The second is MBP134. From Mapp Biopharmaceuticals. It’s a cocktail of two antibodies. They recognize diverse Ebola strains. This one got attention during the 2022 Sudan Ebola outbreak in Uganda. But then it wasn’t a trial. It was “compassionate use.” Patients dying got the drug outside of standard protocols. Did it work? Hard to say. Too many variables.
Monkeys and hope
Animals tell a different story, though.
Thomas Geisbert is a virologist at UTMB. He looks at the monkey data. MBP134 performed well. In 2019, his team infected six monkeys with Bundibugyo. They showed fever, got sick. Five recovered fully after the treatment. One died.
“It’s a true therapeutic. We’ve used it against Bundibugyu and it works fantastically,” Geisbert says. “You can wait until they’re very sick.”
That matters. In real outbreaks, patients arrive at clinics when they are already terrible. MBP138 mimics that scenario. Plans to test both remdesivir and MBP134 in this ongoing crisis make sense, he adds. Mapp has enough doses for a trial. The US government owns them anyway, through BARDA. Larry Zeitlan, Mapp’s CEO, confirms the supply chain is ready.
The vaccine problem
Vaccines? Not so simple. Options are slim.
Geisbert has an experimental vaccine for Bundibugyo. It protects monkeys before and after exposure. Great theory. Bad timing. It is not available for human trials right now.
So officials look at Ervebo. The only approved Ebola vaccine. It crushed the Zaire strain in West Africa from 2014-16. The Africa Centres for Disease Control is weighing a trial. Will it work here?
“It’s kind of a coin Flip,” says Geisbert.
Maybe. In 2011, Geisbert’s team saw some cross-protection. Three out of four monkeys vaccinated against Zaire resisted Bundibugyu. But there is a catch. The monkeys used in that study aren’t killed completely by Bundibugyu in the lab. The results are murky. Geisbert guesses Ervebo might be 50% effective here. At best.
If this epidemic drags on, trials will enroll enough people to know for sure. But researchers hope it ends soon.
It’s very early. Things change quickly. We just wait for the data, hoping it’s enough, wondering if it arrives before the next case knocks.
