WHO Recommends Regeneron's Maftivimab for Clinical Trials Against Bundibugyo Ebolavirus Outbreak
Key Insights
The World Health Organization's Therapeutics Advisory Group has recommended maftivimab, the most potent neutralizing antibody in Regeneron's Inmazeb treatment, for prioritized evaluation in clinical trials against the current Bundibugyo ebolavirus (search) outbreak in the Democratic Republic of the Congo and Uganda.
Maftivimab has demonstrated broad neutralizing activity in laboratory studies against multiple Ebola (search) species, including Bundibugyo ebolavirus (search), though it has not yet been tested in vivo as a monotherapy against this specific virus strain.
The recommendation comes as WHO declared the current Bundibugyo ebolavirus (search) outbreak a public health emergency of international concern, with Regeneron working to prepare existing maftivimab supply for potential clinical trials.
The World Health Organization's Therapeutics Advisory Group has recommended maftivimab, a monoclonal antibody developed by Regeneron Pharmaceuticals, for prioritized evaluation in clinical trials as an investigational treatment for the current Bundibugyo ebolavirus (search) outbreak. The recommendation addresses the WHO's recent declaration that the ongoing outbreak in the Democratic Republic of the Congo and Uganda constitutes a public health emergency of international concern.
Maftivimab represents the most potent neutralizing antibody component of Regeneron's FDA-approved Ebola (search) treatment Inmazeb, a three-antibody cocktail that also includes atoltivimab and odesivimab-ebgn. While Inmazeb is specifically indicated for Orthoebolavirus zairense (search) (Zaire ebolavirus (search)) infections, maftivimab has demonstrated broad neutralizing activity in laboratory studies against multiple Ebola species, including Bundibugyo ebolavirus (search).
Clinical Development and Safety Profile
The antibody has been administered to hundreds of patients as a component of Inmazeb, which has demonstrated an acceptable safety profile in clinical use. However, maftivimab has not yet been tested in vivo as a monotherapy against Bundibugyo ebolavirus (search), making the upcoming clinical trials critical for establishing its efficacy against this distinct viral strain.
Inmazeb's safety and efficacy were established through the 681-patient PALM Trial, independently conducted by WHO, the National Institutes of Health, and the Institut National de Recherche Biomédicale during the 2018 DRC outbreak. The trial was stopped early in 2019 following a pre-specified interim analysis that demonstrated Inmazeb's superiority in preventing death compared to two other investigational treatments, as reported in the New England Journal of Medicine.
Regulatory Status and Global Access
Inmazeb became the first Ebola (search) treatment approved by the U.S. FDA in 2020, followed by WHO prequalification in November 2023 as the first and only Ebola treatment to meet WHO's standards for quality, safety, and efficacy. The treatment is considered "essential" under WHO guidelines published in 2022, which strongly recommend its use for Zaire ebolavirus (search) infections.
"We are closely coordinating our efforts with the U.S. Department of Health and Human Services and look forward to working with the World Health Organization and others as clinical evaluation moves ahead," said Leonard S. Schleifer, M.D., Ph.D., Board co-Chair, President and Chief Executive Officer of Regeneron.
Emergency Response Efforts
Regeneron is working to prepare existing maftivimab supply for potential clinical trials, while Inmazeb supply is already positioned in the DRC for immediate use if needed. In September 2025, the company donated 500 doses of Inmazeb to WHO for exclusive use by governments of low- and lower-middle income countries most at risk for Ebola (search) outbreaks.
The company has also delivered Inmazeb stockpiles to the U.S. Government as part of HHS efforts to enhance national preparedness for public health emergencies. Since 2018, Regeneron has offered Inmazeb at no cost under compassionate use protocols to infected individuals in countries experiencing Orthoebolavirus zairense (search) outbreaks, including the DRC and Guinea.
Technology Platform and Mechanism of Action
Inmazeb was developed using Regeneron's VelocImmune platform and associated VelociSuite technologies, which produce optimized fully human antibodies. The treatment consists of three monoclonal antibodies that neutralize the Ebola virus (search) by blocking its ability to invade patient cells and enlisting immune cells to target and remove infected cells from the body.
"Regeneron's prior work in Ebola (search) has shown how innovative science and groundbreaking technology platforms can be rapidly translated into life-saving medicines for people facing some of the world's most dangerous infectious diseases," said George D. Yancopoulos, M.D., Ph.D., Board co-Chair, President and Chief Scientific Officer of Regeneron.
WHO is now working closely with the governments of DRC and Uganda to facilitate implementation of research evaluations of the prioritized treatments, with Regeneron supporting the Afya Foundation's emergency response efforts to safeguard frontline healthcare workers during the current outbreak.