NEWS ABOUT Ebola, a viral disease that kills up to 90% of those it infects, is usually grim. The latest outbreak, in the Democratic Republic of Congo (DRC), has thus far killed nearly 1,900 people and rages on. But on August 12th the grimness lifted somewhat with the announcement that two anti-Ebola treatments being tested in the country have proved effective. If administered when the first signs of infection appear, they boost survival rates to about 90%.
The treatments in question employ antibodies. These are special protein molecules made by the immune system in response to infection. They work by locking onto specific parts of invading pathogens, or of body cells infected by those pathogens—either gumming the target up and disabling it or marking it for destruction by other parts of the immune-system. It is possible, however, to give the immune system a helping hand by identifying suitable antibodies in advance, manufacturing them in bulk, and then injecting them into those infected by the target organism.
One of the successful treatments, code-named REGN-EB3, is a cocktail of three such antibodies, mixed by Regeneron, an American biotechnology firm. The other, mAb114, is a single antibody developed by America’s National Institute for Allergies and Infectious Diseases. REGN-EB3 and mAb114 were among four experimental treatments tested in a randomised trial at clinics in the DRC. Based on preliminary results from 500 patients, an oversight committee led by the World Health Organisation concluded that the trial should be stopped immediately, in order that the two successful treatments could be made available to everyone.
Prompt use after infection is vital. Overall, 29% of those receiving REGN-EB3 died. But of people treated when their viral loads were still low only 6% succumbed. For mAb114 the numbers were 34% and 11% respectively—superficially worse, but actually indistinguishable, statistically speaking, from the results for REGN-EB3. Two other candidates had significantly worse figures than these, and were therefore rejected by the overseers.
Both REGN-EB3 and mAb114 have histories. Regeneron developed the former in 2016, in response to an Ebola epidemic in West Africa in which 11,000 people died. But that outbreak came to an end before the treatment could make its way into clinics, and until now there has been no opportunity to test it. The story of mAb114 goes back even further. Its pertinent antibody was isolated from a survivor of an epidemic of Ebola in the DRC in 1995.
Both treatments will now be deployed in the field—but, given the smallish size of the trial that approved them, doctors will be looking closely at their relative efficacies to determine whether, in light of more data, one is actually better than the other. Regardless of that, effective treatment will surely help break the epidemic directly, by stopping those cured passing on the virus. And it may help indirectly, too. At the moment, those who have become infected, seeing others go into clinics alive only to leave in coffins, are understandably reluctant to follow suit. That means they remain in their homes and spread the illness to others. The prospect of going to a clinic for a cure will change this, and thus help also to break the chain of transmission.