Supernus Pharmaceuticals Inc. CEO Jack Khattar said the phase III failure in the study called P301 with SPN-810 (molindone hydrochloride) was "very puzzling" to the Rockville, Md.-based firm, which will be "digging very deep into the data" with hopes of figuring out what went wrong. Shares (NASDAQ:SUPN) closed Wednesday at $19.93, down $9.20, or 31.6%.