Yes, Zenith is being very tight lipped. My guess is that they are very close to, if not already, finding the maximum tolerated dose (MTD) in the ZEN-3694/enzalutamide combo trial. It took Zenith ~6 months from first dosing to announce that they had found the MTD for the single agent trial. Dosing for the combo trial started sometime in the late 2016/early 2017 timeframe, so assuming that the combo trial follows a similar timeline, then the MTD for the combo trial should have been found already or very soon. Once that happens, they will have found the MTD for both the single agent and combo trials.

As of last update June 20th, they were still in the dose escalation portion for the combo trial and were just initiating the expansion cohort at the optimal dose for the single agent trial. Once they get the MTD and decide on the optimal dose for the combo trial, then they should be ready for expansion cohort in the combo trial. 

Just for reference, here's a couple of my recent posts on Zenith that discuss the status of the single agent trial and potential timelines for other trials.

BearDownAZ