Evaluate Pharmacokinetics, Safety, and Tolerability of AX251 LAI in Patients With Schizophrenia

The purpose of this study is to assess the pharmacokinetics (PK), safety, and tolerability of AX251 long-acting injectable (LAI) administered as a single dose in patients with schizophrenia. The study will include sequential dose-escalation cohorts to evaluate different dose levels of AX251 LAI.

Inclusion Criteria: * Male or female subjects aged 18 to 65 years (inclusive). * clinical diagnosis of schizophrenia per the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) (or later) criteria, at screening. * Body Mass Index (BMI) 18.5-35.0 kg/m² at screening. * Clinical Global Impression-Severity (CGI-S) score ≤4 at screening. * Positive and Negative Syndrome Scale (PANSS) total score ≤75 at screening. * Clinically stable schizophrenia on current antipsychotic medication other than cariprazine for at least 3 months prior to screening. * Subjects must not be taking more than two antipsychotic medications. * Able to remain at the study site for 7 days following AX251 LAI injection. * Judged by the investigator to be physically and mentally able to participate in the study based on clinical evaluation, physical examination, electrocardiogram (ECG), and laboratory assessments. * Willing and able to comply with study procedures. * Agrees to use protocol-defined contraception during the study. * Previous tolerability to oral cariprazine (1.5-6 mg) or willingness to undergo a short oral tolerability test (2-7 days) followed by washout before study drug administration. Exclusion Criteria: * Diagnosis of psychiatric disorders other than schizophrenia according to DSM-5-TR (e.g., schizoaffective disorder, major depressive disorder, bipolar disorder, generalized anxiety disorder, obsessive-compulsive disorder, post-traumatic stress disorder, dementia, mild neurocognitive disorder, or personality disorders), except caffeine- or tobacco-related disorders. * Substance use disorder (including alcohol or benzodiazepines) within 180 days prior to screening, excluding caffeine and tobacco. * History of neuroleptic malignant syndrome, seizure disorder, or clinically significant tardive dyskinesia, akathisia, or extrapyramidal symptoms. * Clinically significant cardiovascular, hematologic, metabolic, hepatic, renal, immunologic, or neurological disease that may interfere with study participation. * Severe hepatic impairment (Child-Pugh Class C) at screening. * Uncontrolled hypertension. * Clinically significant electrocardiogram abnormalities at screening. * Severe renal impairment (estimated glomerular filtration rate \