BUTEMBO, Democratic Republic of Congo—The Ebola virus kills in terrifying ways, shutting down the body’s organs and draining victims of the fluids that keep them alive. In outbreaks, it has claimed as many as 9 in 10 patients.

In a medical breakthrough that compares to the use of penicillin for war wounds, two new drugs are saving lives from the virus and helping uncover tools against other deadly infectious diseases. They were proven effective in a gold-standard clinical trial conducted by an international coalition of doctors...