It is quite possible that ENTA acquisition discussions are taking place already and these discussions are not going well.
Just a fact that may (or may not) have a bearing on the timing of a potential deal with ABBV. The composition and use patents for ABT-450 have not yet issued. ABBV may be waiting for these patents to clear before deciding when (or if) they will make an offer for ENTA. Note: ABBV and ENTA worked together on the protease class assets (including ABT-450).