This is an efficacy and safety study evaluating an experimental treatment for cognitive deficits in adults with schizophrenia.

This is a Phase 2 study designed to evaluate the efficacy and safety of ABT-126 in approximately 210 adults with schizophrenia. Subjects will be randomized to one of three treatment groups (ABT-126 Dose 1, ABT-126 Dose 2 or placebo) for a 12-week Treatment Period. The purpose of this research study is to find out whether ABT-126 compared to placebo can improve cognition and what side effects ABT-126 may cause. Cognition is the way a person thinks, and it includes abilities like paying attention, focusing, remembering things, and solving problems. Acronyms listed in the Outcomes and/or Eligibility sections for this study are defined below: • MCCB: Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery • UPSA-2: University of California at San Diego (UCSD) Performance-Based Skills Assessment-2 • CANTAB: Cambridge Neuropsychological Test Automated Battery • PANSS: Positive and Negative Syndrome Scale • NSA-16: Negative Symptom Assessment-16 • CGI-S: Clinical Global Impression - Severity

Inclusion Criteria

• Has current DSM-IV-TR diagnosis of schizophrenia confirmed by the Mini-International Neuropsychiatric Interview.
• Is clinically stable while receiving antipsychotic therapy with one or two atypical antipsychotic medications: lack of hospitalizations from 4 months of Initial Screening Visit; taking same antipsychotic medication(s) for at least 8 weeks prior to the Day -1 visit; core positive symptoms of PANSS no worse than moderate in severity throughout Screening Period of at least 4 weeks.
• Has been diagnosed with or treated for schizophrenia for at least 2 years prior to Initial Screening Visit.
• Has had continuity in psychiatric care (e.g., mental health system, clinic or physician) for at least 6 months prior to Initial Screening Visit.
• Has an identified responsible contact person (e.g., family member, social worker, case worker, or nurse) that can provide support to the subject and ensure compliance with protocol requirements.

Exclusion Criteria

• Has valid current or past diagnosis of schizoaffective disorder, bipolar disorder, manic episode, dementia, posttraumatic stress disorder, obsessive compulsive disorder, or a current major depressive episode.
• Has history of substance abuse (excluding nicotine or tobacco products) or alcohol abuse within 6 months prior to Screening Visit; has a substance dependence disorder (excluding nicotine or tobacco products) that has not been remitted for at least 1 year prior to Initial Screening Visit.
• Is taking any medication for extrapyramidal symptoms at any time from the Initial Screening Visit until the Day -1 Visit.
• Is taking any antidepressant that is excluded, including tricyclic antidepressants and monoamine oxidase inhibitors, at any time from 8 weeks prior to the Day -1 Visit.
• Has significant suicidal ideation at Initial Screening Visit.
• Has had a suicide attempt within 1 year prior to the Day -1 Visit.
• Has participated in another trial utilizing the MATRICS Consensus Cognitive Battery (MCCB) or UCSD Performance-Based Skills Assessment (UPSA) (any version) within 6 months prior to Initial Screening Visit.
• Is currently enrolled in any form of cognitive remediation training.