This study is a multicenter, randomized, double-blind, parallel, placebo-controlled Phase III clinical trial evaluating the efficacy and safety of GZR18 injection in obese subjects with moderate to severe obstructive sleep apnea who are unable or unwilling to undergo positive airway pressure (PAP) therapy.

Inclusion Criteria:

1. Subject is aged ≥18 years at the time of signing the informed consent form.

2. Body mass index (BMI) is ≥28 kg/m² at both screening and randomization.

3. Subject has a documented history of at least one unsuccessful attempt at weight loss through dietary control prior to screening, and has had <5% change in body weight during the 12 weeks prior to screening.

4. Subject has been diagnosed with obstructive sleep apnea (OSA) , and has a centrally assessed apnea-hypopnea index (AHI) ≥15 events/hour on polysomnography (PSG) at screening.

5. Unable or unwilling to receive PAP therapy before screening, and not planning to initiate PAP therapy during the study period.

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Exclusion Criteria:

1. Known or suspected hypersensitivity to glucagon-like peptide-1 receptor agonists (GLP-1 RAs) or any of their excipients, or presence of a contraindication to GLP-1 RA use.
2. History of any type of diabetes mellitus (history of gestational diabetes is permitted).
3. Has undergone or plans to undergo during the study period surgical or device-based obesity treatment (exceptions: acupuncture, liposuction, or abdominal fat removal performed >1 year prior to screening; prior device-based obesity treatment is acceptable if the device was removed >1 year before screening).
4. Secondary obesity due to disease, medication, or other causes (e.g., Cushing's syndrome, Prader-Willi syndrome, monogenic obesity, or obesity secondary to hypothalamic/pituitary injury).
5. Clinically significant gastric emptying disorders at screening (e.g., gastroparesis or gastric outlet obstruction); or long-term use (≥4 consecutive weeks) of medications affecting gastrointestinal motility within 6 months prior to screening.
6. History of acute or chronic pancreatitis or pancreatic injury prior to screening.
7. History of symptomatic gallbladder disease at screening (post-cholecystectomy status is permitted); or presence at screening of cholelithiasis conferring high risk for acute biliary pancreatitis.
8. Clinical or subclinical thyrotoxicosis at screening, regardless of treatment status.
9. Inadequately controlled blood pressure at screening or randomization: systolic BP ≥160 mmHg and/or diastolic BP ≥100 mmHg (concurrent antihypertensive therapy is permitted).
10. History within 6 months prior to screening of: decompensated heart failure (NYHA Class III-IV), unstable angina, myocardial infarction, ischemic or hemorrhagic stroke (lacunar infarcts excluded), transient ischemic attack; or invasive cardiovascular procedures/therapies (e.g., valve replacement, CABG, PCI). (Diagnostic coronary angiography without intervention is permitted.)
11. Positive response on the Columbia-Suicide Severity Rating Scale (C-SSRS) Screening Version to Question 4 or 5 of the "Suicidal Ideation" section, or any question in the "Suicidal Behavior" section, with the event occurring within 4 weeks prior to screening; or investigator assessment of significant suicide risk during the study.
12. History of moderate-to-severe depression; or Patient Health Questionnaire-9 (PHQ-9) score ≥15 at screening.
13. Any uncontrolled acute or chronic hepatitis other than metabolic dysfunction-associated fatty liver disease (MAFLD).
14. Personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia (MEN) type 2A or 2B.
15. History of malignancy within 5 years prior to screening (exceptions: definitively cured in situ carcinomas, e.g., basal/squamous cell skin cancer, cervical in situ carcinoma, or prostate in situ carcinoma).