Not counting the pending cases, that's only 50% (so far), which can happen with Ebola, anyway--especially considering that these patients are getting the best available care.
Granted, there may be a host of other considerations such as general health, age, disease progress, etc. on a case by case basis, and if the other two recover, that would tend to indicate some efficacy (33% death rate instead of 50% or higher).
Without all the outcomes, and considering it is a very small sample with numerous other variables, I can't say the therapy does not work, but it does not appear to be the magic bullet at this time. The disease might have progressed more in the patients who died prior to receiving treatment, too.
A larger sample, (and even full results from this one) could show a different and better outcome, so it would be premature to say it isn't effective.