The PANSS is comprised of 30 items and three subscales. The Negative subscale contains seven questions to assess blunted effect, emotional withdrawal, poor rapport, passive/apathetic social withdrawal, lack of motivation, and similar symptoms. An anchored Likert scale from 1-7, where values of 2 and above indicate the presence of progressively more severe symptoms, is used to score each item. The PANSS Negative subscale score is the sum of all 7 items and ranges from 7 through 49. A higher score is associated with greater illness severity.

The PANSS is comprised of 30 items and three subscales. The General Psychopathology subscale addresses other 16 symptoms such as anxiety, somatic concern, and disorientation. An anchored Likert scale from 1-7, where values of 2 and above indicate the presence of progressively more severe symptoms, is used to score each item. The PANSS General Psychopathology subscale score is the sum of all 16 items and ranges from 16 through 112. A higher score is associated with greater illness severity.

Proportion of participants with treatment-emergent adverse events. An adverse event was defined as any untoward medical occurrence in a study participant who was taking a medicinal (investigational) product. Treatment-emergent adverse events (TEAEs) were defined as adverse events with a start date on or after the date of the first dose through the end of follow-up, or adverse events occurring before the date of first dose and worsening during the treatment or follow-up period.

Proportion of participants with treatment-emergent adverse events. An adverse event was considered serious if it met one or more of the following criteria: Resulted in death; Was life-threatening (i.e., a patient was at immediate risk of death at the time of the event, not an event where occurrence in a more severe form might have caused death); Required in-patient hospitalization or prolongation of existing hospitalization; Resulted in persistent or significant disability/incapacity; Was a congenital anomaly/birth defect; Was considered to be an important medical event.

Placebo was administered orally twice daily.

Risperidone 2 mg was administered orally twice daily.

Total of all reporting groups

The PANSS is comprised of 30 items and three subscales. The Positive subscale contains seven questions to assess delusions, conceptual disorganization, hallucinations behavior, excitement, grandiosity, suspiciousness/persecution, and hostility. An anchored Likert scale from 1-7, where values of 2 and above indicate the presence of progressively more severe symptoms, is used to score each item. The PANSS Positive subscale score is the sum of all 7 items and ranges from 7 through 49. A higher score is associated with greater illness severity.

FAS (Full Analysis Set)

The PANSS is comprised of 30 items and three subscales. The Negative subscale contains seven questions to assess blunted effect, emotional withdrawal, poor rapport, passive/apathetic social withdrawal, lack of motivation, and similar symptoms. An anchored Likert scale from 1-7, where values of 2 and above indicate the presence of progressively more severe symptoms, is used to score each item. The PANSS Negative subscale score is the sum of all 7 items and ranges from 7 through 49. A higher score is associated with greater illness severity.

FAS (Full Analysis Set)

The PANSS is comprised of 30 items and three subscales. The General Psychopathology subscale addresses other 16 symptoms such as anxiety, somatic concern, and disorientation. An anchored Likert scale from 1-7, where values of 2 and above indicate the presence of progressively more severe symptoms, is used to score each item. The PANSS General Psychopathology subscale score is the sum of all 16 items and ranges from 16 through 112. A higher score is associated with greater illness severity.

FAS (Full Analysis Set)

Proportion of participants with treatment-emergent adverse events. An adverse event was defined as any untoward medical occurrence in a study participant who was taking a medicinal (investigational) product. Treatment-emergent adverse events (TEAEs) were defined as adverse events with a start date on or after the date of the first dose through the end of follow-up, or adverse events occurring before the date of first dose and worsening during the treatment or follow-up period.

Safety population defined as subjects who receive at least one dose of the study drug in the treatment period.

Safety population defined as subjects who receive at least one dose of the study drug in the treatment period.

Proportion of participants with treatment-emergent adverse events. An adverse event was considered serious if it met one or more of the following criteria: Resulted in death; Was life-threatening (i.e., a patient was at immediate risk of death at the time of the event, not an event where occurrence in a more severe form might have caused death); Required in-patient hospitalization or prolongation of existing hospitalization; Resulted in persistent or significant disability/incapacity; Was a congenital anomaly/birth defect; Was considered to be an important medical event.

Safety population defined as subjects who receive at least one dose of the study drug in the treatment period.

SM-13496 40 mg was administered orally once daily on Days 1 to 7, SM-13496 60 mg on Days 8 to 14, and SM-13496 80 mg on Days 15 to 42.

Placebo was administered orally twice daily for 6 weeks.

Risperidone 2 mg was administered orally twice daily on Days 1 to 7, risperidone 3 mg on Days 8 to 14, and risperidone 4 mg on Days 15 to 42.