Here's the gist of what happened, i.e. the reason for the sell-off: (From the 10Q):
"In addition, we are continuing our work on various regulatory matters, including our work with the FDA on updated documents that we have submitted to the FDA on our Xyrem Risk Management Program. The updated documents are intended to conform to current formatting requirements for REMS required by law, as well as to make other updates to the program and its documentation. While we cannot predict the timing of finalization, or the final terms, of approved REMS documents for Xyrem, we expect that the FDA will require final REMS documents that will result in, or permit, modifications to aspects of the Xyrem Risk Management Program, which may include the ability to distribute Xyrem through more than one pharmacy. We also expect that the final REMS documents will include requirements that are not currently implemented in the Xyrem Risk Management Program. Any such modifications or additional requirements could potentially make it more difficult or expensive for us to distribute Xyrem, make it easier for future generic competitors to enter the market and/or negatively affect sales of Xyrem. "