Bioequivalence Study of Long-Acting Paliperidone Palmitate in Patients With Schizophrenia

Prior treatment

• Past or current seizure or convulsive disorders (except childhood febrile seizures), or stroke or transient ischemic attack within 1 year prior to consent.
• Electroconvulsive therapy within 28 days prior to consent.
• Blood loss ≥400 mL within 3 months prior to consent, or ≥200 mL within 1 month prior to consent due to donation, surgery, or other causes.
• Use of any investigational drug within 1 month prior to first study dose (excluding paliperidone palmitate or placebo), or prior participation in a gene therapy or cell therapy clinical trial such that, in the investigator's judgment, the participant is not suitable for this study.
• Major surgery within 3 months prior to consent, or planned surgery within 1 month after study completion.
• Prohibited medications/treatments: (1) ziprasidone or thioridazine within 4 weeks prior to consent; (2) any other long-acting injectable antipsychotic received within one labeled dosing interval prior to consent (except risperidone microspheres), or receipt of risperidone microspheres (e.g., Hengde®) within 6 weeks prior to consent; (3) non-selective or irreversible monoamine oxidase inhibitors within 1 month prior to first dose; (4) strong or moderate inhibitors or inducers of CYP3A4, CYP2D6, or P-gp within 2 weeks prior to consent.
• Drug abuse history, illicit drug use, or positive drug abuse screening within 1 year prior to consent.

Other illness

• Known or suspected hypersensitivity to the study drug (paliperidone palmitate) or any of its components.
• Diagnosis per ICD-10 or DSM-5 of any psychiatric disorder other than schizophrenia.
• Clinically significant diseases or abnormalities, as judged by the investigator, in the respiratory, cardiovascular, gastrointestinal, genitourinary, reproductive, nervous, endocrine, or immune systems that may affect participant safety or interfere with study participation.
• History of orthostatic hypotension or syncope due to orthostatic hypotension (except if stable for \>6 months); or at screening/baseline, a decrease in systolic blood pressure ≥20 mmHg or diastolic blood pressure ≥10 mmHg within 3 minutes after changing from supine to standing.
• Past or current neuroleptic malignant syndrome.
• Parkinson's disease, Lewy body dementia, or dementia-related psychosis.
• History of tardive dyskinesia induced by risperidone, paliperidone, or other antipsychotics.
• Esophageal motility disorders, dysphagia, or other conditions that confer risk of aspiration pneumonia.
• Positive tests for hepatitis B surface antigen, hepatitis C antibody, HIV antibody, or treponemal (syphilis) antibody.
• Clinically significant history of syncope related to needles or blood draws. Any other condition that, in the investigator's opinion, makes the participant unsuitable for the study.

Lab values

• Laboratory abnormalities at screening or baseline meeting any of the following: (1) total bilirubin \>1.5 × ULN, or AST or ALT \>2 × ULN; (2) creatinine clearance (CLcr) \<90 mL/min; (3) white blood cell count \<3 × 10\^9/L, or absolute neutrophil count \<1.5 × 10\^9/L, or platelets \<80 × 10\^9/L.
• Congenital long QT syndrome; uncontrolled or significant cardiovascular disease, including congestive heart failure of NYHA class II or higher, unstable angina, or myocardial infarction within 6 months prior to first study dose; significant arrhythmias (including frequent premature ventricular contractions), or clinically significant arrhythmias requiring treatment at screening; QTc \>450 ms (male) or \>460 ms (female) at screening or baseline; risk factors for torsades de pointes or sudden death (e.g., bradycardia, clinically significant hypokalemia or hypomagnesemia, current use of medications that prolong QTc); or other clinically significant ECG abnormalities as judged by the investigator.
• Uncontrolled diabetes mellitus, or HbA1c ≥7% at screening or baseline.

Other

• Harmful alcohol use: \>14 units per week (1 unit = 360 mL beer, or 150 mL wine, or 45 mL spirits).
• High suicide risk: C-SSRS suicidal ideation items 4 or 5 answered "Yes" within the past 6 months at screening/baseline; or suicidal behavior within the past 6 months; or, in the investigator's judgment, a serious risk of suicide.
• Pregnant, breastfeeding, or planning pregnancy; except for women who are postmenopausal for ≥1 year or surgically sterile (e.g., bilateral tubal ligation with non-recanalized tubes, bilateral oophorectomy, or hysterectomy).

• Age 18 to 65 years inclusive at the time of consent.
• Diagnosis of schizophrenia (ICD-10 criteria) prior to screening.
• PANSS total score ≤70 at screening and at baseline.
• CGI-S score ≤4 at screening and at baseline.
• Body weight at screening: ≥50.0 kg (male) or ≥45.0 kg (female); body mass index (BMI) 19.0 to 35.0 kg/m2 (inclusive).
• The participant and/or partner have no plans for pregnancy during the study and for 6 months after the last dose, and agree to use effective contraception (oral contraceptives are not allowed).
• Signed informed consent and willingness and ability to comply with all study requirements.