I agree that those numbers don't look very good for INCY. I wasn't anticipating the rates of discontinuation to be so high after just one year. In a real-world setting, it is likely to be even higher. However, it's not clear (at least not to me) what the other reasons for discontinuation were. They mention 40% due to progression or lack of response and 35% due to toxicity, but I'm assuming that these two categories overlap.
The rebound effect, if real, may limit ruxolitinib use to primarily high-risk patients. It would be interesting to know if the adverse events leading to discontinuation could have been manageable, without having to resort to treatment discontinuation. Perhaps patients might also need to be tapered off the medication instead of discontinuing it suddenly in order to avoid a rebound effect.