I realize the company may have been privy to more safety information, but actually going back some time on the conference calls (in hindsight) one could tell that they were planning it. There was a call where someone specifically asked and I vaguely recall Dan Welch hesitating before answering that is an option available to them not available to some other PI's (i.e. Vertex).
I remember that discussion. If you want to do some sleuthing work, find the date of the CC where the above exchange took place and ascertain how far ITMN-191+SoC studies had progressed by then.