Overview

Phase 2, multicenter, randomized, double-blind, placebo-controlled study evaluating once-weekly subcutaneous retatrutide (LY3437943) at multiple maintenance dose levels versus placebo in adults with obesity or overweight with weight-related comorbidities (without type 2 diabetes), alongside standardized diet and physical activity counseling.

Eligibility

Inclusion Criteria:

• Age 18 to 75 years (inclusive) at time of informed consent.
• BMI ≥30 and ≤50 kg/m², OR BMI ≥27 and \<30 kg/m² with at least 1 weight-related comorbidity (hypertension; dyslipidemia; or cardiovascular disease such as ischemic CVD or NYHA Class I-II heart failure).
• Motivated and able/willing to self-inject (or have trained assistance if needed) and follow study procedures, including lifestyle advice and questionnaires.
• Subgroup (NAFLD addendum): liver fat content ≥10% by MRI-PDFF (for participants invited to the addendum).
• Male and/or female; contraception requirements apply; women of childbearing potential must have negative pregnancy tests at specified visits and should not be breastfeeding.
• Capable of giving signed informed consent and complying with protocol requirements.

Exclusion Criteria:

• History of diabetes mellitus (type 1 or type 2), ketoacidosis, or hyperosmolar state/coma.
• Screening lab values suggestive of diabetes (HbA1c ≥6.5%; fasting glucose ≥126 mg/dL; or random glucose ≥200 mg/dL).
• Self-reported change in body weight \>5 kg within 3 months prior to screening.
• Prior or planned surgical treatment for obesity (exceptions: liposuction/abdominoplasty \>1 year prior).
• Current/planned endoscopic or device-based obesity therapy, or device removal within last 6 months (e.g., intragastric balloon, gastric artery embolization).
• Renal impairment: eGFR \<45 mL/min/1.73 m² (CKD-EPI) at screening.
• Clinically significant gastric emptying abnormality (e.g., severe gastroparesis) or chronic drugs affecting GI motility.
• History of acute or chronic pancreatitis (exception for resolved gallstone pancreatitis post-cholecystectomy).
• TSH outside 0.4 to 6.0 mIU/L at screening (with protocol-defined exceptions).
• Obesity due to other endocrine disorders (e.g., Cushing's) or monogenic/syndromic obesity (e.g., Prader-Willi).
• Psychiatric exclusion criteria including unstable major depressive disorder/severe psychiatric disorder within 2 years; lifetime suicide attempt; PHQ-9 score ≥15; or specified Columbia-Suicide Severity Rating Scale (C-SSRS) findings within past month.
• Uncontrolled hypertension (systolic ≥160 mmHg and/or diastolic ≥100 mmHg) or elevated resting pulse rate (\>100 bpm) at baseline.
• Recent (within 3 months) major cardiovascular events (e.g., MI, stroke, unstable angina, CHF hospitalization); tachyarrhythmia syndromes; NYHA Class III-IV CHF; or ECG abnormalities interfering with interpretation.
• Acute/chronic hepatitis or liver disease other than NAFLD; or screening labs: ALT \>3× ULN, ALP \>1.5× ULN, or total bilirubin \>1.5× ULN (with exception).
• Elevated calcitonin at Visit 1 per protocol thresholds; personal/family history of medullary thyroid carcinoma or MEN2.
• Active/untreated malignancy or remission \<5 years (with protocol exceptions for certain in-situ/skin cancers).
• Contraindication to GLP-1 receptor agonists, or other conditions that could prevent protocol compliance (including drug/alcohol abuse or eating disorder), per investigator judgment.
• Alcohol consumption \>14 units/week (women) or \>21 units/week (men).
• Recent marijuana/THC-containing product use within 3 months or unwillingness to abstain during trial (protocol exception for cannabidiol oil if agrees to refrain).
• Organ transplant history (except corneal transplant) or awaiting transplant.
• Hematologic conditions interfering with HbA1c measurement; recent large blood donation/transfusion/severe blood loss; hemoglobin below protocol thresholds.
• Severe atopy/multiple severe allergies or severe hypersensitivity reactions.
• Fasting triglycerides \>500 mg/dL at screening (with stability requirement for lipid-lowering therapy).
• Significant active, uncontrolled medical condition or history posing risk or interfering with data interpretation, per investigator judgment.
• History of symptomatic gallbladder disease within past 2 years (protocol-defined exceptions after cholecystectomy).
• History of documented HIV infection.
• Chronic systemic glucocorticoid therapy within 3 months or active autoimmune abnormality likely to require systemic steroids during study (with specified formulation exceptions).
• Recent medications that may cause significant weight gain (e.g., tricyclic antidepressants, atypical antipsychotics, mood stabilizers) within 3 months.
• Recent use (within 3 months) of medications or remedies intended to promote weight loss (examples listed in protocol, including GLP-1 RAs).
• Use of metformin or other glucose-lowering medications (e.g., for PCOS or diabetes prevention) not permitted at entry.
• Started implantable/injectable contraceptives within 18 months prior to screening (IUDs allowed if used ≥3 months).
• Known allergies to GLP-1 receptor agonists or LY3437943.
• Currently enrolled in another investigational study or recent participation/treatment within 30 days (or 5 half-lives, whichever longer).
• Previously received LY3437943 in this or another study.
• Investigator site personnel directly affiliated with the study and/or their immediate family; or Lilly employees.
• Note: The publicly posted protocol references additional exclusion criteria numbered 52-57 in a separate protocol addendum (not included in the posted protocol PDF).