The market seems to think that 38% market share is too large.
That the market expects ABBV/ENTA to get less than 38% of the GT1 market is clear not only from ENTA’s valuation, but also from a survey by ISI analyst, Mark Schoenbaum of the “buy side” in which the average forecast was a 23% share for ABBV/ENTA.
Of course, such disagreements are what makes a market.