Who is buying it and why? Hmmm, tough one, but I'll take a crack. Technically speaking, it's an absolutely perfect chart as it closed above both the pivot point and 200 day MA yesterday. The gap filled from Brexit, it got right back up off it's back quick and has technical breakout written all over it.
Fundamentally speaking, it's probably the most undervalued stock in biotech. It has an approved product for a multi billion dollar space that big pharma can do wonders with. They've already spoken with their CHECKBOOK for a competitor and bought their unapproved product for over 3x the current valuation here.
You aren't dense enough to believe the recent stranglehold on the PPS changed any of the fundamentals are you? So man, really tough question, but the reason people are buying the stock is because a perfect storm is brewing and it's as close to free money as you can get from this level.