Shares of Vitae Pharmaceuticals Inc. (NASDAQ:VTAE) fell more than 50 percent to hit a record low Friday after the company closed enrollment earlier than expected in the second part of a multiple ascending-dose study of its psoriasis candidate, VTP-43742. Concern over the meaning of the move, for which Vitae provided little explanation, led Stifel analyst Tom Schrader to downgrade company shares and suggest that the firm is “unlikely to report data that are viewed as overall positive for this trial.”