http://www.sciencemag.org/news/2015/12/special-report-ebolas-thin-harvest

*Update, 4 June 2018, 3 p.m.: While public health authorities and international organizations are trying to stop the Ebola outbreak in the Democratic Republic of the Congo (DRC), scientists have a rare chance to test new therapies on people infected with the virus, both to potentially help them and to gather data for the future. The DRC is considering testing several candidate Ebola drugs and antibodies that are in development. But the Ebola epidemic that exploded across West Africa several years ago showed that such trials are difficult to set up and conduct.

As the West African epidemic was winding down, Science took stock of each clinical study that researchers had conducted—or attempted to carry out—in the three most affected countries: Guinea, Liberia, and Sierra Leone. It was a thin harvest—except for a study of a vaccine produced by Merck, none of the trials yielded conclusive results. Some were able to enroll only a handful of patients, even though there were more than 28,000 cases; others suffered from not having a control group.