There can be a ton of reasons wholly unrelated to the drug, a common one is the person who championed the deal left.
If the results are good, I wouldn't overthink it. Big pharma makes mistakes. What I hear over and over from people in bio is that big pharma is incredibly risk averse. $B's in bio market cap can be attributed to drugs pharma "gave back." A good one these days is vx-950, used to be lly's until they gave it back.
Market Data 
Markets 
AI
