Both treatments involve giving patients antibodies that trap the virus and block it from attacking the cells.
Ebola may no longer be an incurable disease.
Scientists today announced that two treatments tested in a clinical trial in the Democratic Republic of the Congo significantly improve survival – to the point where both treatments will now be available to all enrolled patients.
Both treatments deliver anti-Ebola antibodies to patients, providing rapid protection. While Ebola typically carries a mortality rate of around 50 percent (and it’s approaching 70 percent in the current outbreak), only about 10 percent of patients who started either treatment shortly after falling ill succumbed to the disease.
Two other treatments in the study, which began in November, with less impressive survival rates, were discontinued so study participants could switch to better options.
The findings remain preliminary, and it is unclear how the drugs will work outside of clinical trials. But the researchers behind this announcement hope this early success could pave the way to contain the ongoing epidemic in the Democratic Republic of Congo, which has killed nearly 2,000 people since it began last summer.
Both treatments, called REGN-EB3 and mAb-114, involve the injection of antibodies that latch on to the outside of the Ebola virus. This swarm strategy blocks the virus from attacking cells, while immune cells are recruited to defeat the invader. A similar process underlies the third drug in the study, ZMapp, which until now was considered the standard of care for the Ebola outbreak. But both REGN-EB3 and mAb-114 outperform their predecessors as well as a fourth drug called remdesivir.
Photo from the 1995 Ebola outbreak in the Democratic Republic of the Congo.
At four treatment centers, half of the patients taking ZMapp or remdesivir died, while REGN-EB3 and mAb-114 reduced the mortality to 29 and 34 percent, respectively. Deaths decreased even further in patients who received treatment soon after they began experiencing symptoms, with approximately 90 percent of patients with REGN-EB3 and mAb-114 surviving, compared with approximately 65 to 75 percent of those taking other medications.
The results came as a complete shock, Sumathi Sivapalasingam, Regeneron’s medical firm in the REGN-EB3 project, Helen Branswell told STAT News.
The study also highlights the urgent need for immediate treatment. On average, people arrive at treatment centers about four days after falling ill, Michael Ryan of the World Health Organization told Sarah Bosely in The Guardian – a delay that not only reduces the chances of survival, but also increases the likelihood of the virus being passed on.
There is no guarantee that the current numbers will hold on with the start of a new series of trials, now with a renewed emphasis on comparing the effectiveness of REGN-EB3 and mAb-114. But the manufacturers of both drugs have already pledged to continue production.
It’s not clear why these two new treatments have an advantage over ZMapp, but it could have something to do with the way they are formulated. While ZMapp is a single antibody suspension isolated from Ebola infected mice, REGN-EB3 is a mix of three – an immune cocktail that increases the body’s chances of controlling the virus. mAb-114 also has a single antibody component, but one is isolated from a human Ebola survivor, reports Megan Molteni in Wired.
Ryan told Donald G. McNeil Jr. from The New York Times that having two options available is an unexpected boon and provides natural support should one or the other drug run into complications.
The forecast is not yet clear, especially for the now-not-based ZMapp. But it has the potential to be replaced by two new therapies that could ultimately change the outcomes of ebola patients.
“From now on, we will no longer say that Ebola is incurable,” said Bosely Jean-Jacques Muyembe, director general of the Institut National de Recherche Biomédicale in the DRC, who oversaw the trial. “These advances will help save thousands of lives.”