The World Health Organization (WHO) identified three experimental treatments as priority candidates for the Bundibugyo strain of Ebola virus disease.

WHO is recommending they be urgently evaluated in clinical trials as an outbreak continues to spread across the Democratic Republic of the Congo and into Uganda.

What drugs were identified as leading candidates?

The WHO named Mapp Biopharmaceutical's MBP134, Regeneron's maftivimab, and Gilead Sciences' antiviral remdesivir as the leading therapeutic candidates.¹ The agency, working alongside outside experts, has been engaged in a broader effort to identify viable candidates for both treatment and prevention, a pressing task given that there are currently no approved vaccines or therapies specifically targeting Bundibugyo virus disease.¹

What is Bundibugyo virus?

Bundibugyo virus disease is a distinct strain of Ebola, and unlike the more widely studied Zaire strain, it remains without a licensed treatment or vaccine. WHO's recommendation to generate clinical trial data reflects the urgency of an evolving public health emergency in central and east Africa, where cases have been confirmed in both the DRC and Uganda.¹

Regeneron noted that supply of maftivimab is already on the ground in the DRC, positioning the monoclonal antibody therapy for potential immediate deployment as either a treatment option or as part of a formal study arm should WHO choose to activate it. Additionally, WHO advisors are also recommending evaluations of a combination approach, pairing a monoclonal antibody with remdesivir, as a potential treatment strategy.¹

For individuals exposed to confirmed cases, Gilead's experimental oral antiviral obeldesivir was flagged as a priority candidate for post-exposure prophylaxis. WHO noted, however, that its effectiveness would be contingent on robust contact tracing, a significant operational challenge in the affected regions.

What is WHO doing to prevent the disease?

On the prevention side, WHO has reviewed several vaccine candidates at varying stages of development, including a single-dose candidate known as rVSV Bundibugyo which is being developed by the International AIDS Vaccine Initiative and was considered the most promising of those reviewed.² However, the agency also cautioned that it is unlikely to be ready for clinical trials for another seven to nine months.

A second candidate, ChAdOx1 Bundibugyo, developed by Oxford University in collaboration with the Serum Institute of India, could potentially be available for testing within two to three months, though additional animal data are still required before human trials can proceed.²

WHO also assessed Merck's Ervebo, the only licensed Ebola vaccine, but concluded it should not be deployed outside of research settings as evidence of its protective efficacy against the Bundibugyo strain remains limited and inconclusive, according to the agency.²

What is WHO’s Priority?

WHO emphasized that all candidate interventions, both therapeutic and preventive, must be evaluated through rigorously designed clinical trials conducted under strict ethical standards. The agency says it is actively working with health authorities in Congo and Uganda, alongside partners including Africa CDC, to design and implement those trials.¹

Sources

1. WHO identifies Ebola treatments, vaccines to be tested in trials amid outbreak Reuters May 28, 2025 https://www.reuters.com/business/healthcare-pharmaceuticals/who-urges-ebola-treatments-vaccines-be-tested-only-trials-amid-bundibugyo-2026-05-28/
2. Experimental treatments could help US Ebola patient Reuters May 22, 2026 https://www.reuters.com/legal/litigation/experimental-treatments-could-help-us-ebola-patient-2026-05-22/