Shares of Longboard Pharmaceuticals (LBPH) gained 14% on Thursday after it announced that the FDA granted two designations — orphan drug and rare pediatric disease — to its lead pipeline drug bexicaserin for the treatment of Dravet syndrome (DS).An orphan drug designation is granted by the FDA to the candidates developed to treat, diagnose or prevent a rare disease or condition. This designation makes the sponsor eligible to receive seven years of market exclusivity following a potential approval and tax cr ...