Safety and Efficacy Study of APD125 in Patient With Insomnia

Inclusion Criteria: * Primary insomnia as defined in DSM-IV-TR, with predominant complaint of impaired sleep maintenance and confirmed by PSG * PSQI \>/= to 5 * Qualifying screening PSG parameters * Generally good health Exclusion Criteria: * History of any sleep disorder, other than primary insomnia (e.g., restless leg syndrome, narcolepsy, sleep apnea, and disorders of REM/NREM sleep) * Any clinically significant medical condition, laboratory finding, or ECG finding * Pregnant and/or lactating females * History of substance abuse within 2 years or positive urine drug screen * Positive Hepatitis B/C results or HIV markers * Apnea-Hypopnea Index (AHI) or a Periodic Limb Movement Arousal Index (PLMAI) \> 10 as determined by screening PSG * History of treatment with an investigational drug within the last month * Recent travel involving crossing more than 3 time zones or plans to travel to another time zone (\> 3 time zones) during the study