The purpose of this study is to find out the time it takes to absorb, distribute, breakdown and remove the drug from the body, safety and tolerability of AMG 581 in healthy participants and subjects with schizophrenia.

The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetic profile of single-ascending oral doses of AMG 581 in healthy subjects and subjects diagnosed with schizophrenia or schizoaffective disorder receiving antipsychotic treatment.

This will be a placebo-controlled, single-ascending oral-dose study of AMG 581 with a food-effect cohort. Approximately 70 subjects will be enrolled. This study will enroll healthy subjects into 8 cohorts (Cohorts 1,2,3,4,5,6,8 and 9), and subjects with schizophrenia or schizoaffective disorder receiving antipsychotic medication into a single cohort (Cohort 7).

Inclusion Criteria:

• Provide informed consent prior to initiation of any study-related procedure
• Male and female subjects ≥ 18 to ≤ 45 years of age at the time of screening
• Non-nicotine or non-tobacco for healthy subjects
• No history of relevant medical disorders
• BMI ≥ 18.0 and ≤ 30.0
• Non-reproductive females
• Males practicing effect birth control
• Avoid tanning/direct sunlight
• Willing to consume high-fat meal
• Schizophrenia or schizoaffective disorder
• PANSS score ≤ 4 points on a few items (i.e. conceptual disorganization, hallucinatory behavior, excitement, suspiciousness/persecution, hostility, depression, anxiety, disorientation, uncooperativeness, disturbance of volition, and poor impulse control) / total score ≤ 80 points

Exclusion Criteria:

• Females lactating/breastfeeding
• Pregnant partners of male subjects
• Tremor or gait disturbance
• History of hereditary shorten QT syndrome
• Malignancy or tumor (other than skin cancers)
• History of GI disease
• QTc ≥ 450 msec or ≤ 380 msec
• Creatinine clearance < 80 mL/min at screening