Ebola drugs should be limited to trials, WHO advisers say

Michelle Fay Cortez and Gerry Smith, Bloomberg News on May 28, 2026

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Drugs in development to treat and prevent infections caused by the Ebola virus that’s circulating in the Democratic Republic of Congo and Uganda should be given only as part of clinical trials, advisers to the World Health Organization said.

That means people who are sick now, or are at risk of becoming sick after being exposed to them, may not get access. It has been extraordinarily difficult to develop Ebola drugs, given that the outbreaks emerge sporadically, often in remote areas, and kill patients so quickly.

WHO convened several expert advisory groups to assess potential medicines for the Bundibugyo strain currently circulating. They recommended all the products “be used exclusively within clinical trials to generate robust data and ensure safe, ethical, and effective research,” the organization said.

That recommendation could run into some resistance. The U.S. already plans to make monoclonal antibodies available to Americans who become infected, according to a White House official. The treatments would be available at a facility in Kenya to treat Americans exposed to the virus, the official said on a call with reporters Thursday.

The public health advisers called out treatments in development from Mapp Biopharmaceutical Inc., Regeneron Pharmaceuticals Inc. and Gilead Sciences Inc. as “promising enough to warrant prioritization for evaluation in clinical trials,” the WHO said in an email.

Regeneron said it’s “working as quickly as possible” to prepare the supply of its antibody drug, maftivimab, for use in potential upcoming clinical trials. The drug “has demonstrated broad neutralizing activity” in laboratory studies against the Bundibugyo strain, the company said in a statement.

Mapp, which also is developing a monoclonal antibody, declined to comment.

The monoclonal antibodies also may be beneficial when given with Gilead’s antiviral pill Veklury, known as remdesivir, and the combinations should be evaluated, WHO said.

Gilead “is exploring potential ways to support response efforts with relevant health and regulatory authorities,” the company said in a statement. “Any decisions regarding participation in clinical research or potential support for trials would be guided by public health needs, scientific evidence, and coordination with appropriate authorities.”

Preventing infection

Other medicines that may help prevent infection include a vaccine candidate in development from the International AIDS Vaccine Initiative. The immunization will likely take seven to nine months before it’s ready to start a clinical trial, WHO said in the statement.

Another shot, ChAdOx1, being developed by Oxford University and Serum Institute of India, may be ready for testing in as little as two months, though additional animal data are needed to confirm that, the global health agency said.

The only approved immunization for the viral infection is Merck & Co.’s Ervebo, which targets the most common Zaire strain of the virus. Evidence about its benefits for use against the Bundibugyo strain is “limited and inconclusive,” WHO said. It recommends that Ervebo shouldn’t be given outside of research settings so its safety and effectiveness can be determined.

Regeneron’s treatment is one part of a three-antibody cocktail, called Inmazeb, that was approved by U.S. regulators to treat a different strain of the Ebola virus and has been given to hundreds of patients. Supplies of Inmazeb are already on the ground in the Congo if the WHO wants to use it for immediate treatment, Regeneron said.

The company has a history of developing treatments for a public health crisis. In one famous example, President Donald Trump got the company’s antibody treatment when he contracted Covid-19 during his first term in office.

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