PANSS negative subscale assesses negative symptoms associated with schizophrenia. The negative subscale consists of 7 items (blunted affect, emotional withdrawal, poor rapport, passive/apathetic social withdrawal, difficulty in abstract thinking, lack of spontaneity and flow of conversation, and stereotyped thinking). Each item is rated on a scale from 1 (symptom not present) to 7 (symptoms extremely severe). Total negative subscale scores range from 7 to 49; higher score indicates greater severity.

General psychopathology subscale assesses general psychopathology symptoms associated with schizophrenia. The general psychopathology subscale consists of 16 items (somatic concern, anxiety, guilt feelings, tension, mannerisms/posturing, depression, motor retardation, uncooperativeness, unusual thought content, disoriented, poor attention, lack of judgment/insight, disturbance of volition, poor impulse control, preoccupation, and active social avoidance). Each item is rated on a scale from 1 (symptom not present) to 7 (symptoms extremely severe). Total general psychopathology subscale scores range from 16 to 112; higher score indicates greater severity.

Cognition cluster subscale assesses cognitive symptoms associated with schizophrenia. The cognition cluster subscale score is a sum of 5 items from positive, negative and general psychopathology subscales (conceptual disorganization, difficulty in abstract thinking, poor attention, lack of judgment and insight, and preoccupation). Each item is rated on a scale from 1 (symptom not present) to 7 (symptoms extremely severe). Total cognition cluster subscale scores range from 5 to 35; higher score indicates greater severity.

Responders were defined as 20 percent (%) responders and 50 % responders. A 20% responder was a participant whose PANSS total score was decreased by at least 20% from baseline to the week of assessment. A 50% responder was a participant whose PANSS total score was decreased by at least 50 % from baseline to the week of assessment. PANSS total score assesses the positive symptoms, negative symptoms, and general psychopathology specifically associated with schizophrenia. The scale consists of 30 items. Each item is rated on a scale from 1 (symptom not present) to 7 (symptoms extremely severe). The sum of the 30 items is defined as the PANSS total score and ranges from 30 to 210; higher score indicates greater severity.

CGI-S: 7-point clinician rated scale to assess severity of participant's current illness state; range: 1 (normal - not ill at all) to 7 (among the most extremely ill patients).

CGI-I: 7-point clinician rated scale to assess global improvement in the participant's clinical state compared to baseline; range: 1 (very much improved) to 7 (very much worse).

CDSS: 9-item clinician rated scale, validated for rating the severity of depressive symptoms in participants with schizophrenia. Each item is rated on a 4-point scale ranging from 0 (absent) to 3 (severe). CDSS total score is the sum of each item scores and ranges from 0 to 27; higher score indicates more severity of symptoms.

One vabicaserin 100 mg capsule and 3 placebo capsules matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

One vabicaserin 50 mg capsule, 1 vabicaserin 100 mg capsule, and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 150 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 32 and then 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

Two vabicaserin 100 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 100 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 300 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Two vabicaserin 200 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 400 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 200 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 600 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

One risperidone 4 mg capsule and 3 placebo capsules matched to risperidone (equivalent to risperidone 4 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 risperidone 2 mg capsule and 1 placebo capsule matched to risperidone (equivalent to risperidone 2 mg) orally once daily up to Day 35 during taper phase.

One vabicaserin 100 mg capsule and 3 placebo capsules matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

One vabicaserin 50 mg capsule, 1 vabicaserin 100 mg capsule, and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 150 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 32 and then 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

Two vabicaserin 100 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 100 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 300 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Two vabicaserin 200 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 400 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 200 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 600 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

One risperidone 4 mg capsule and 3 placebo capsules matched to risperidone (equivalent to risperidone 4 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 risperidone 2 mg capsule and 1 placebo capsule matched to risperidone (equivalent to risperidone 2 mg) orally once daily up to Day 35 during taper phase.

One vabicaserin 50 mg capsule, 1 vabicaserin 100 mg capsule, and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 150 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 32 and then 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

Two vabicaserin 100 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 100 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 300 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Two vabicaserin 200 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 400 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 200 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 600 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

One risperidone 4 mg capsule and 3 placebo capsules matched to risperidone (equivalent to risperidone 4 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 risperidone 2 mg capsule and 1 placebo capsule matched to risperidone (equivalent to risperidone 2 mg) orally once daily up to Day 35 during taper phase.

One vabicaserin 50 mg capsule, 1 vabicaserin 100 mg capsule, and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 150 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 32 and then 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

Two vabicaserin 100 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 100 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 300 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Two vabicaserin 200 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 400 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 200 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 600 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.

One risperidone 4 mg capsule and 3 placebo capsules matched to risperidone (equivalent to risperidone 4 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 risperidone 2 mg capsule and 1 placebo capsule matched to risperidone (equivalent to risperidone 2 mg) orally once daily up to Day 35 during taper phase.

One vabicaserin 100 mg capsule and 3 placebo capsules matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

One vabicaserin 50 mg capsule, 1 vabicaserin 100 mg capsule, and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 150 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 32 and then 2 placebo capsules matched to vabicaserin orally once daily up to Day 35 during taper phase.

Two vabicaserin 100 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Three vabicaserin 100 mg capsules and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 300 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 32 and then 1 vabicaserin 50 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 50 mg) orally once daily up to Day 35 during taper phase.

Two vabicaserin 200 mg capsules and 2 placebo capsules matched to vabicaserin (equivalent to vabicaserin 400 mg) orally once daily up to Day 28 during double-blind treatment phase followed by 1 vabicaserin 200 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 200 mg) orally once daily up to Day 32 and then 1 vabicaserin 100 mg capsule and 1 placebo capsule matched to vabicaserin (equivalent to vabicaserin 100 mg) orally once daily up to Day 35 during taper phase.