Yes this will be done but the point is: survival will only be used as a stop point. That's what we as investors have to worry about. The FDA will not just look at MDSCs and such and say "OK we'll halt the trial for efficacy." Any samples collected during SUNRISE are for understanding MOA only. I should have clarified that. My bad.
And the reason for that is...you just don't change design of the trial in light of new understanding of MOA. And it's highly experimental = high risk, especially for the most important trial ever. It would have taken months, years maybe for SUNRISE. For future clinical trials, yes this will likely be done as it is already evident from the melanoma trial design.