Additional Relevant Details Catalyst Pharmaceuticals announced that it has received a "Refusal to File" letter from the FDA on its NDA for Firdapse.  The FDA found that the NDA, submitted in December 2015, was "not sufficiently complete, and requests additional supporting information".  However, the letter makes no claims against the efficacy or safety of Firdapse.  The Company plans to meet with the FDA and resolve the issues and then resubmit the NDA.