By Salma El-Sakka
Global health authorities are racing to develop medical interventions for an Ebola outbreak in eastern Democratic Republic of Congo caused by the Bundibugyo strain, which currently has no approved vaccines or treatments. Unlike the Zaire strain, for which vaccines and therapies exist, the Bundibugyo ebolavirus (BDBV) carries a fatality rate of up to 40 percent. As of Sunday, the Congolese Ministry of Health reported 782 confirmed cases and 181 deaths.
Experimental vaccines under evaluation
The World Health Organization (WHO) has prioritized two vaccine candidates. The most promising is a single-dose rVSV Bundibugyo vaccine developed by the International AIDS Vaccine Initiative (IAVI), using technology similar to Merck's approved Ervebo vaccine for the Zaire strain. A 2023 study in non-human primates showed survival benefits, but the WHO estimates seven to nine months before clinical trial readiness. IAVI is advancing manufacturing under Good Manufacturing Practices.
A second candidate, ChAdOx1 Bundibugyo, is being developed by Oxford University and the Serum Institute of India using the same viral vector technology as the Oxford/AstraZeneca COVID-19 vaccine. The Serum Institute began production under an emergency framework last month, with doses potentially ready in two to three months for efficacy assessment, though additional animal studies are pending. The WHO suggests a single dose for contacts of cases and a two-dose regimen for high-risk groups such as healthcare workers. The Coalition for Epidemic Preparedness Innovations (CEPI) is in talks to accelerate both candidates.
Antibody therapies in development
The WHO also recommended prioritizing Mapp Biopharmaceutical's pan-ebolavirus antibody drug MBP134, a combination of two human monoclonal antibodies initially studied for the Sudan strain. Early trials found it safe and well tolerated. The U.S. Biomedical Advanced Research and Development Authority (BARDA) is coordinating shipments for potential use in high-risk Americans. Mapp says the drug shows activity against all known ebolaviruses.
Regeneron Pharmaceuticals' antibody candidate maftivimab has shown laboratory activity against the Bundibugyo virus. The FDA has already approved a combination of maftivimab with two other antibodies (atoltivimab and odesivimab) as Inmazeb for Zaire Ebolavirus. Regeneron recently donated 500 doses of Inmazeb to the WHO, with supply already in DRC for potential immediate use or study inclusion.
Researchers have also isolated human monoclonal antibodies from Bundibugyo survivors. One candidate, BDBV289-N, provided up to 100 percent protection in monkeys even when administered eight days post-infection, according to a 2018 study supported by the U.S. National Institutes of Health.
Antiviral drugs considered for post-exposure prevention
Gilead Sciences' experimental oral antiviral obeldesivir is being evaluated as a potential post-exposure treatment. In monkeys, a 10-day course starting 24 hours after exposure gave up to 100 percent protection against Zaire and Sudan strains, and preclinical data suggest activity against Bundibugyo. Gilead's intravenous antiviral remdesivir has also shown laboratory activity against BDBV, possibly stronger than against the Zaire strain. The WHO recommended evaluating a combination of a monoclonal antibody and remdesivir.
Diagnostic capacity expanded
Limited testing capacity has slowed the outbreak response. BioFire Defense, a bioMérieux affiliate, produces an FDA-cleared panel that detects multiple Ebola species including Bundibugyo, and is increasing production. Germany's Altona Diagnostics has ramped up production of its RealStar Filovirus Screen RT-PCR Kit 1.0, which is being used to detect the outbreak in Congo.
