There are lots of reasons why the p21 data isn't out yet. For instance:
It would be partial data, since the trial isn't over yet.
They won't have data yet on the most recent enrollees in the trial.
They want to have statistically significant data on enough people so that they can eliminate the data on the extreme low-dose trial participants from the first several cohorts (who probably didn't have a response because the dose was so low), and there aren't enough people at higher doses yet.
And, if there is indeed mind-blowing news, they won't want to release partial data now, and potentially endanger the possibility of publication in one of the most prestigious journals because it's "old news."