While the Ebola virus disease is not in the news as much now as it once was, we cannot afford to let down our guard. Ebola cases flared up again as recently as this March in West Africa, causing eight deaths in Guinea and one death in Liberia, and more than 30 other outbreaks of the disease have been recorded in the last 40 years.
The Ebola outbreak of 2014-2016 highlighted the urgent need for therapeutics that could increase the survival rate of infected patients and also aid response organizations in their efforts to limit the spread of this deadly virus. ZMapp, developed by Mapp Biopharmaceutical in San Diego with support from several components of the U.S. government, is a combination of three monoclonal antibodies that target the Ebola virus.
Based on a careful review of preclinical studies of various potential therapies, ZMapp was selected for field use and an evaluation of efficacy in the PREVAIL II study in Guinea, Liberia, Sierra Leone and the United States. However, with the decline in the outbreak’s severity came a slowing of the enrollment in the PREVAIL II clinical study, and that study was closed in January before sufficient patients could be enrolled to draw conclusive results about the efficacy of ZMapp, based on predetermined statistical thresholds. The data from this trial have now been published in the October 13 issue of The New England Journal of Medicine (2016;375:1448-56).
Although the trial did not conclusively prove that ZMapp works, the limited data gleaned from PREVAIL II are encouraging, suggesting there was a greater than 90 percent probability that the finding of increased survival amongst patients treated with ZMapp did not occur by chance alone. This trend toward efficacy means it is no longer ethical to continue a trial comparing ZMapp to standard of care; rather, efforts should shift to comparing ZMapp to other promising therapies. Meanwhile, given all of the work already done to study ZMapp, we anticipate that work will continue to seek FDA approval under the Animal Rule.
To better protect the health of their residents, the U.S. government and the governments of Guinea, Liberia and Sierra Leone want to ensure that ZMapp remains available in the event of new Ebola cases, future outbreaks and flare-ups.
On Aug. 5, these international partners announced that they are pursuing an effort to ensure ZMapp will continue to be a treatment option under an Expanded Access protocol for Ebola for the next three years.
ASPR’s Biomedical Advanced Research and Development Authority, or BARDA, is providing approximately $13.4 million over the next three years to implement and maintain the ZMapp Expanded Access Protocol. This will allow the continued use of ZMapp in the nations that participated in the PREVAIL II clinical study during the Ebola outbreak. The FDA approved the continued use of ZMapp under the Expanded Access Protocol earlier this year and continues to work with Mapp Biopharmaceutical to lay out a path that could lead to future approval.
The U.S. partners, including the National Institutes of Health, Centers for Disease Control and Prevention, BARDA, FDA, and Mapp Biopharmaceutical, will work with international partners, including the Ministries of Health in Guinea, Liberia and Sierra Leone, to ensure access.
Clinical sites are being set up in each of the three participating West African countries and will be staffed with experts with extensive expertise in those countries and professionals trained in administering ZMapp. The partnership also will operate one mobile Ebola treatment unit in each of these countries and provide air capability to reach remote areas.
Meanwhile, U.S. federal agencies will continue efforts to develop effective vaccines and therapies against Ebola. The response to Ebola underscored the importance of global health preparedness and, while the immediate threat Ebola poses has diminished since 2014, we must vigorously prepare against future emerging infectious disease outbreaks. Helping ensure the future availability of effective countermeasures to Ebola will help us better protect public health against this threat globally.
