WHO Launches Clinical Trial for Bundibugyo Ebola Treatments in DRC

The World Health Organization has begun a clinical trial testing experimental treatments for Bundibugyo virus disease in the Democratic Republic of the Congo, while advisers recommend that all candidate Ebola drugs be limited to clinical trials. The outbreak of the Bundibugyo strain of Ebola, declared a public health emergency of international concern, has led to 1,792 confirmed cases and 625 deaths as of July 9.

The Platform Adaptive Randomised Trial for New and Repurposed Filovirus Treatments (PARTNERS) will evaluate whether two antiviral therapies, the monoclonal antibody MBP134 and remdesivir, can improve survival among patients with confirmed Bundibugyo virus disease. Researchers will also assess whether combining the two treatments provides greater clinical benefit. Remdesivir, an antiviral drug made by Gilead Sciences, and MBP134, a monoclonal antibody developed by Mapp Biopharmaceutical, are both administered intravenously — MBP134 as a one-off infusion and remdesivir over 10 days of intravenous therapy.

The trial is sponsored by WHO and coordinated by the Institut National de Recherche Biomédicale (INRB) in the DRC, the Institute of Tropical Medicine in Belgium, and the University of Oxford, in collaboration with international research, clinical and humanitarian partners, with support from the Africa Centres for Disease Control and Prevention. The trial design allows for the addition of other potential treatments if they become available. A result is likely to need between 700 and 1,000 patients to be enrolled, and WHO officials have said enough remdesivir and MBP134 have been donated for 1,200 patients.

Patients enrolled in the trial will receive standard supportive care, including fluid replacement, oxygen therapy, blood pressure management and pain relief, and close medical monitoring for at least 28 days. The randomized controlled trial is open to patients of all ages with confirmed Bundibugyo virus disease.

WHO convened several expert advisory groups to assess potential medicines for the Bundibugyo strain. They recommended that all identified candidate products be used exclusively within clinical trials to generate robust data and ensure safe, ethical, and effective research. For treatment, experts recommended prioritising three candidate therapeutics: the monoclonal antibodies MBP134 and Maftivimab, and the antiviral remdesivir. The use of combination therapy involving a monoclonal antibody and remdesivir is also being considered for evaluation.

Maftivimab, developed by Regeneron, is the most potent neutralizing antibody included in Inmazeb, a three-antibody cocktail approved by the U.S. Food and Drug Administration for the treatment of Zaire ebolavirus. Maftivimab has demonstrated broad activity in vitro against multiple Ebola species, including Bundibugyo, but has not yet been tested in vivo as a monotherapy against this distinct virus. In September 2025, Regeneron donated 500 doses of Inmazeb to the WHO for exclusive use by governments of low- and lower-middle income countries most at-risk for Ebola outbreaks. Supply of Inmazeb is already on the ground in the DRC.

For prevention, the oral antiviral obeldesivir has been prioritised for post-exposure prophylaxis among contacts of confirmed and probable cases. The most promising vaccine candidate is the single-dose rVSV Bundibugyo vaccine, which may take seven to nine months before it is ready for clinical trials. Another vaccine candidate, ChAdOx1 Bundibugyo, being developed by the University of Oxford and the Serum Institute of India, could be available for evaluation within two to three months. US biotech company Moderna is also working on an mRNA-based vaccine against Bundibugyo.

The only approved immunization for Ebola is Merck & Co.'s Ervebo, which targets the most common Zaire strain of the virus. WHO stated that Ervebo is not approved for the Bundibugyo strain and that evidence of its effectiveness against this variant remains limited and inconclusive. WHO recommended that Ervebo should only be used within carefully designed research settings to assess its potential effectiveness.

The recommendation that drugs be limited to trials could run into resistance. The US already plans to make monoclonal antibodies available to Americans who become infected, with treatments available at a facility in Kenya to treat Americans exposed to the virus, according to a White House official.