To keep things in perspective, in oncology the current success rate of treatments that enter trials is just 5%! See http://blogs.sciencemag.org/pipeline/archives/2016/06/02/are....

Immunotherapy is indeed the most promising approach to cancer therapy so I'm optimistic, but the odds of success here are 1-in-20 if this is an average study, or perhaps 1-in-5 at best.