This study consisted of two parts. In Treatment Period I, FK949E or placebo was administered orally in a blind manner to bipolar disorder patients with major depressive episodes, with the aim of evaluating the superiority of FK949E over placebo and the dose response of two doses of FK949E based on changes in Montgomery-Asberg Depression Rating Scale (MADRS) total score. In Treatment Period II, the long-term safety, efficacy and pharmacokinetics of open-label FK949E was evaluated in patients who completed Treatment Period I. An analysis was performed for data in Treatment Period I and another analysis was done for data in combined Treatment Periods I and II.
In period I, the treatment effect of FK949E was compared with that of placebo in a blind manner in bipolar disorder patients with major depressive episodes. In period II, the long-term safety and efficacy of FK949E was evaluated.