The purpose of this study is to test a new drug, RG2417, to see how the drug affects symptoms of bipolar I depression and to make sure it is safe in humans.

Inclusion Criteria:

• Bipolar I Disorder, most recent episode depressed
• History of 2 or more manic or mixed episodes, at least one of which required pharmacologic treatment for manic symptoms

Exclusion Criteria:

• Current manic, hypomanic or mixed episode
• Rapid cycling bipolar disorder (4 or more mood episodes in the last year)
• Dementia or any other Axis I diagnosis (besides bipolar I) that requires treatment
• Alcohol or drug dependence within 6 months; alcohol or drug abuse within 3 months
• Positive urine drug test for amphetamines, cocaine metabolites, opiates and/or phencyclidine(PCP)
• Axis II diagnosis likely to interfere with study compliance
• Serious suicidal or homicidal risk
• Sensitivity to any of the drug ingredients, including lactose
• Women who are pregnant, breast feeding or refuse to use adequate birth control
• Current seizure disorder
• Current episode of depression is longer than 1 year