Two Ebola treatments prove highly effective in a clinical trial

The ongoing field experiment in Congo will now focus on only the top-performing therapies


In the Congolese city of Beni, a doctor dons protective gear prior to seeing patients with possible Ebola infections. Early reports from a clinical trial in Congo are now in. They found that two drugs were highly effective at preventing death from the disease.

Vincent Tremeau/World Bank/Flickr (CC BY-NC-ND 2.0)

Doctors and scientists have been testing four treatments for Ebola in a clinical trial. That trial has taken place amid an ongoing outbreak in the Democratic Republic of Congo. Two of those treatments have proven to be effective in preventing death, preliminary data now suggest.

The recent Ebola outbreak began August 1, 2018, in the central African nation of Congo. The drug trial began in November. Participants were randomly given one of four experimental treatments. Three were antibody treatments: mAb114, REGN-EB3 and ZMapp. (Antibodies are proteins that the immune system harnesses to help fight germs and other “foreign” materials.) The other treatment was an antiviral drug, remdesivir.

Researchers reviewed data from 499 treated patients on August 9. That review suggests that those people taking mAb114 or REGN-EB3 had a greater chance of survival than those on the remdesivir or ZMapp. Researchers reported the trial results in a news release August 12. However, these findings have yet to be finalized.

“One thing that won’t change [after more study] is that those two therapies are better than the other two — that’s for sure,” says Anthony Fauci. Fauci is director of the National Institute of Allergy and Infectious Diseases. It’s part of the National Institutes of Health in Bethesda, Md. The trial now enters a phase with only the two most effective treatments. Researchers will gather more data on the treatments’ safety and the immune response to each drug. They won’t study enough patients, however, to see which drug works best.

Twenty-nine percent of the patients taking REGN-EB3 died. Among those taking mAb114, 34 percent died. That’s a big improvement over the current 67 percent mortality rate reported for Congo’s outbreak. (Regeneron Pharmaceuticals Inc. makes the REGN-EB3 therapy. Regeneron is a major financial supporter of the Society for Science & the Public. This nonprofit also publishes Science News for Students.)

Results were even better for patients with a low viral load, meaning those with less of the virus in their blood. A low viral load may indicate their infections were caught early. Among such patients, 6 percent taking REGN-EB3 died. Eleven percent of those on mAb114 died.   

The ZMapp antibody treatment showed promise when it was tested briefly on people during 2014. At that time, Ebola had spread through several nations in West Africa. In the new trial, ZMapp was considered the key comparison, or control, group. In the ZMapp group, 49 percent of patients died. Among low-viral load patients on ZMapp, 24 percent succumbed to the disease, Fauci says. Results for remdesivir were slightly worse than for ZMapp.

Antibody treatments provide the immune system with an immediate supply of antibodies that can target a virus. The mAb114 therapy is made of a single antibody cloned from an Ebola survivor of a 1995 outbreak. REGN-EB3 is a cocktail of three antibodies.

The World Health Organization, or WHO, declared Congo’s Ebola outbreak a public health emergency on July 17. Officials say there is a high risk that the disease could spread to neighboring countries. By August 10, the outbreak had killed 1,888 of the 2,816 people who had been reported as infected, WHO says. 

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