Zogenix Inc. CEO Stephen Farr said the refusal to file (RTF) letter from left field for Fintepla (ZX-008, fenfluramine hydrochloride) for seizures associated with Dravet syndrome (DS) could set the compound back "12 to 15 months, would be our best guess" if the FDA insists that the Emeryville, Calif.-based firm do further nonclinical toxicology studies. "We had constructive interactions with the FDA on our program, which started in 2015," Fuller said during a conference call with investors. "This requirement is definitely unexpected for us."