Phase 3 Study to Evaluate the Efficacy and Safety of Orally Administered BF2.649 in Japanese Patients with Obstructive Sleep Apnea Syndrome Complaining Excessive Daytime Sleepiness despite Treated by Nasal Continuous Positive Airway Pressure (nCPAP), Consisting of a Double-blind, Randomized, Placebo-controlled, Parallel-group, Multicenter Study (Part 1) and Subsequent Open-label Extension Study (Part 2)

INTERVENTION: BF2.649 oral administration at a dose of 5mg or 10mg or 20 mg, or placebo tablets CONDITION: obstructive sleep apnea syndrome PRIMARY OUTCOME: Epworth Sleepiness Scale (ESS) INCLUSION CRITERIA: ‐ Individuals who have been diagnosed with obstructive sleep apnea syndrome ‐ Japanese males or females aged 18 years or older at the time of informed consent ‐ Individuals whose daytime sleepiness have not been improved even after 3 months of nCPAP therapy. ‐ Individuals who can continue to use nCPAP during the study. ‐ In the past 1 month, percentage of days wearing nCPAP is at least 70%, and mean wearing time of days wearing is at least 4 hours/day. ‐ ESS score is at least 12 (mean score of baseline period and Day 0)