August 14, 2019

Health officials on Monday announced that two experimental treatments appear to have improved the survival rates of patients infected with the Ebola virus, and the treatments now will be offered to all patients in the Democratic Republic of Congo (DRC) who have contracted the virus.

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Background

The news comes as DRC grapples with the second-largest Ebola outbreak in history. The World Health Organization (WHO) has reported a total of 2,816 Ebola cases and 1,888 deaths tied to the DRC outbreak as of Saturday.

There currently is no FDA-approved medication to treat Ebola, though there are experimental vaccinations against the virus.

However, the U.S. National Institute of Allergy and Infectious Diseases (NIAID) and WHO in November 2018 launched a randomized clinical trial—called the Pamoja Tulinde Maisha (PALM), which is Swahili for Together Save Lives, study—to test four experimental treatments for Ebola:

  • mAb114, a monoclonal antibody developed by NIAID from the antibodies of an Ebola survivor that blocks components of the virus;
  • REGN-EB3, an antibody cocktail developed by Regeneron Pharmaceuticals using mouse-generated antibodies that is specialized in bioreactors and blocks components of the Ebola virus;
  • Remdesivir (GS-5734), a drug developed by Gilead Sciences;and
  • ZMapp, a drug developed by Mapp Biopharmaceutical that previously had shown signs of improving survival.

A total of 725 patients have enrolled in the clinical trial at Ebola treatment centers in Beni, Katwa, Butembo, and Mangina, which at various points have been hotspots of the current outbreak in DRC. Additional patients who are not enrolled in the trial also have received the treatments under compassionate use protocols. In total, more than 1,400 patients have received one of the experimental treatments.

Preliminary data show two experimental treatments are effective at treating Ebola

Health officials on Monday announced that preliminary data based on 499 study participants showed patients who received REGN-EB3 and mAb114 had lower mortality rates than patients with untreated Ebola. The overall mortality rate for untreated cases is an estimated 67%. In comparison, NIAID Director Anthony Fauci said preliminary data from the clinical trial, which ended Friday, showed patients treated with:

  • mAb114 had mortality rates of 34%;
  • REGN-EB3 had mortality rates of 29%;
  • Remdesivir had morality rates of 53%; and
  • ZMapp had morality rates of 49%.

Further, NIAID reported that, among participants in the trial who initially had low levels of Ebola virus detected in their blood, the survival rate was 94% when treated with REGN-EB3 and 89% when treated with mAb114.

Fauci said officials will drop Remdesivir and ZMapp from future trials because the experimental drugs did not improve survival rates to the same extent as mAb114 and REGN-EB3, and they did not meet a pre-established survival rate threshold. The researchers moving forward plan to test REGN-EB3 and mAB114 against each other.

Implications

Fauci said the preliminary results "mea[n] that we do have now what looks like treatments for a disease which not too long ago we really had no therapeutic approach at all." He said, "We feel that with agents such as these … that we may be able to improve the survival of people with Ebola and … might even make people more enthusiastic about coming for care. Because when you have something to offer an individual, it makes it much more likely that you might get to them early. And the earlier the better, as in any disease." Fauci noted that NIH has about 300 doses of mAb114, and more will become available later this year.

However, Fauci also warned that the data are preliminary, and might change as researchers continue evaluating the results. For instance, Fauci noted that 15% of participants also had received an experimental Ebola vaccine, and it currently is unclear whether those participants' results skewed the data. "More stringent data will be coming," he said.

Reaction

Jean-Jacques Muyembe, director general of DRC's Institut National de Recherche Biomédicale, said, "From now on, we will no longer have to say Ebola is untreatable [if caught early enough]." He added, "These advances will help save thousands of lives."

Sumathi Sivapalasingam, Regeneron's medical lead on the REGN-EB3 project, said Regeneron had expected REGN-EB3 would perform better than the preliminary data suggest, but the company still was surprised at how well the drug performed when compared with the other therapies.

According to STAT News, Mapp Bio President Larry Zeitlin would not immediately comment on the preliminary findings, but said, "We look forward to reviewing the data, and more importantly, hope resources continue to be mobilized to end the [DRC Ebola] outbreak as quickly as possible."

Gilead in a statement said it remains committed to researching Remdesivir as a treatment option for Ebola and other viral diseases, STAT News reports. The company said, "A full analysis of the PALM trial data will help to inform future study [and] use of Remdesivir. Potential learnings may include insight into the impact of viral strain and severity of disease progression on treatment strategies and the potential for both single agent and combination treatment approaches" (O'Reilly, Axios, 8/12; Kelland, Reuters, 8/12; Branswell, STAT News, 8/12; McNeil, New York Times, 8/12).

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