The move comes after TSPT's board adpoted a poison pill and rejected an offer of $3.50/share last week.
Retrophin says the deal "represents an attractive premium to TSPT's trading performance, and ... offers a compelling opportunity for TSPT's stockholders."
Retrophin CEO Martin Shkreli goes on to call TSPT's acquisition strategy "risky and controversial." (PR)
TSPT +8% AH on top of 8% during the regular session.