I believe this drug started being used for Ebola about 5 years ago which is a virus similar to this one.
That means two things, one this isn't a drug that was rushed through. It is a drug that is used for a similar virus. Second, it means that knowing that this drugs mechanism can have an affect on this virus, they can work on making it more effective to target this specific virus.
Yet the last time I checked people continued to contract Ebola.