On July 2, 2026, the first patient was enrolled in the first-ever treatment trial for Bundibugyo ebolavirus disease, a milestone that has been nearly two decades in the making and arrives as the current outbreak in the Democratic Republic of Congo and Uganda has surpassed 1,400 cases and 440 deaths.
The trial, called PARTNERS (Platform Adaptive Randomised Trial for New and Repurposed Filovirus TreatmentS), represents a structural innovation in outbreak response: a pre-designed platform protocol, first deployed during Rwanda’s 2024 Marburg outbreak, that can be activated within days of a new filovirus emergency. Sponsored by the World Health Organization and operated by the DRC’s Institut National de Recherche Biomédicale, the Institute of Tropical Medicine (Antwerp), and the University of Oxford’s Pandemic Sciences Institute, the trial is now enrolling at a treatment unit near Bunia, Ituri Province.
The drugs
The trial is testing two investigational agents against Bundibugyo ebolavirus, a distinct viral species (Orthoebolavirus bundibugyoense) for which there are currently no approved treatments or vaccines.
MPB-134 is an antibody cocktail consisting of two monoclonal antibodies developed by Mapp Biopharmaceutical. The antibodies were isolated from a survivor of the 2014–2016 West Africa Ebola outbreak (caused by Zaire ebolavirus, a different species) and have shown “very strong” preclinical activity against Bundibugyo, according to Thomas Geisbert, a virologist at the University of Texas Medical Branch. The U.S. government has donated 400 doses, covering the entire target enrollment.
Remdesivir is the nucleotide analog antiviral developed by Gilead Sciences. While it was found to be less effective than antibody-based treatments in the 2018–2020 PALM trial for Zaire ebolavirus, laboratory data suggest it has greater potency against Bundibugyo specifically, enough to warrant a dedicated evaluation.
Patients are randomly assigned to one of four arms: MPB-134 alone, remdesivir alone, both drugs combined, or supportive care only as a control. A third antibody, maftivimab, may be added to the trial later if preliminary results support it.
A parallel trial
Alongside PARTNERS, a second trial called EBO-PEP will begin within weeks, testing the oral antiviral obeldesevir (an oral counterpart of remdesivir) as post-exposure prophylaxis for close contacts of confirmed cases. The drug is already in the country; preparations for enrollment are underway.
The outbreak context
The current outbreak was first detected on May 5, 2026, in the Mongbwalu Health Zone of Ituri Province, DRC. The World Health Organization declared it a Public Health Emergency of International Concern on May 17. It is only the third known outbreak of Bundibugyo virus, the species was first identified in Uganda in 2007, with a second outbreak in DRC in 2012. Historical case fatality rates range from 30% to 50%.
As of July 2, the DRC has reported more than 1,400 cases, including 438 deaths, with 20 additional cases and 2 deaths in neighboring Uganda.
Why now
The absence of treatment trials for Bundibugyo has not been for lack of need, but for lack of preparation. The 2013–2016 West Africa outbreak, caused by Zaire ebolavirus, prompted an unprecedented investment in filovirus research and the development of drugs and vaccines that are now approved for Zaire but not for other Ebola species. When the current Bundibugyo outbreak began, the research infrastructure was theoretically in place, but no trial had been designed specifically for this species.
The PARTNERS platform protocol was designed to solve exactly this problem: a pre-written, ethics-approved, adaptable trial framework that can be operationalized for any filovirus at any location. This is the third activation of the platform, following its use in Rwanda’s Marburg outbreak in 2024.
What to watch
The trial targets enrollment of up to 1,200 patients, and initial results are expected later this year. The key endpoints will be mortality reduction compared with supportive care; the trial’s adaptive design allows for arms to be dropped or added as data accumulate.
The scientific community will also be watching whether the drugs that were effective against Zaire ebolavirus (such as the REGN-EB3 and mAb114 antibodies that dominated the PALM trial) show cross-species efficacy against Bundibugyo, or whether the viral differences are great enough that species-specific treatments will be needed.
Funding: Wellcome, UK Foreign Commonwealth and Development Office, Medical Research Council/UKRI.
Source
Kupferschmidt, K. “First-ever treatment trial for Ebola Bundibugyo kicks off in Congo.” Science (2 July 2026). DOI: 10.1126/science.zyvmn4t