Two of four Ebola treatments prove highly effective in a clinical trial

Two Ebola treatments have proven to be effective in preventing death during a clinical trial conducted amid the ongoing outbreak in Congo, preliminary data suggest.

The trial began in November, with participants randomly given one of four experimental treatments (SN: 3/16/19, p. 9). Data from 499 patients reviewed August 9 suggest that those people taking one of two antibody treatments — mAb114 or REGN-EB3 — had a greater chance of survival than those on the antiviral drug remdesivir or the antibody treatment ZMapp. Researchers reported the trial results in a news release August 12, but these findings have yet to be finalized.

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

The percentage of patients who died while taking one of the treatments was 29 percent for REGN-EB3 and 34 percent for mAb114. That’s a big improvement over the current 67 percent mortality rate reported for Congo’s outbreak, which began August 1, 2018. (Regeneron Pharmaceuticals Inc., which makes the REGN-EB3 therapy, is a major financial supporter of the Society for Science & the Public, the nonprofit that also publishes Science News.)

Results were even better for patients with a low viral load, or less of the virus in their blood — which may be an indication that their infections were caught early. Among those patients, 6 percent taking REGN-EB3 died and 11 percent on mAb114 died.    

Among patients given the ZMapp antibody treatment, which was considered the key comparison group, 49 percent died, with 24 percent of low-viral load patients on ZMapp succumbing 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 the virus. The mAb114 therapy is made of a single antibody cloned from an Ebola survivor of a 1995 outbreak, while REGN-EB3 is a cocktail of three antibodies.

The World Health Organization declared Congo’s Ebola outbreak a public health emergency on July 17, due to fears of the disease spreading to neighboring countries (SN Online: 7/17/19). By August 10, the outbreak had killed 1,888 of the 2,816 people reported infected, WHO says.