# Retatrutide: An Independent Appraisal of the Clinical Trial Evidence > Retatrutide is an investigational triple-agonist compound in Phase 3 trials. An independent dossier appraising the published evidence, study by study — efficacy, liver data, safety, and what remains open. Phase 2 produced a mean −24.2% body-weight change at 48 weeks and an −82.4% reduction in liver fat at 24 weeks. Phase 3 is running. This is what the published record contains — not what vendors claim. ## The brief version Retatrutide is an experimental compound — not an approved drug — being studied by Eli Lilly in large clinical trials. It works by activating three hormone receptors at once: GLP-1 (which curbs appetite and helps regulate blood sugar), GIP (which enhances insulin response after eating), and glucagon (which raises the body's calorie-burning rate). No other approved obesity medicine activates all three simultaneously. The trials so far have shown large effects. In a 48-week study involving 338 adults with obesity, the highest dose produced an average weight loss of 24.2%, compared with 2.1% in the placebo group. A separate substudy in people with fatty liver disease (called MASLD — metabolic dysfunction-associated steatotic liver disease) found that 86% of participants reached normal liver fat levels by week 24. These are Phase 2 results — the compound is now in Phase 3 trials (the TRIUMPH program) that will confirm those findings in larger populations before any regulatory submission. Retatrutide is **not available by prescription** and is **not approved by the FDA or any regulator** as of 2026. What people report about it — and what to watch out for — is on [the effects page](/effects). ## What the Phase 2 record shows The landmark finding for retatrutide comes from the 48-week Phase 2 obesity trial published in the *New England Journal of Medicine*: once-weekly subcutaneous injections at the 12 mg dose produced a mean body-weight change of −24.2% versus −2.1% with placebo [1]. The trial enrolled 338 adults with obesity or overweight with a comorbidity; doses of 1, 4, 8, and 12 mg were tested, with weight loss scaling across the dose range. For type 2 diabetes, a parallel Phase 2 trial in 281 adults demonstrated HbA1c (glycated hemoglobin — the standard three-month blood-sugar average) reduction of −2.02 percentage points at 12 mg versus −0.01 with placebo at 24 weeks, with body weight down 16.94% by week 36 [2]. The liver-MASLD finding is the angle this dossier follows most closely. A 48-week Phase 2a substudy specifically enrolled participants with MASLD — fatty liver tied to metabolic risk — and found that retatrutide 12 mg reduced liver fat (measured by MRI-PDFF, the standard non-invasive liver-fat scan) by −82.4% at 24 weeks. Eighty-six percent of participants at the highest dose reached normal liver fat (below 5%) [5]. Reductions were sustained to 48 weeks (−86.0% at 12 mg). The glucagon receptor arm — which drives lipolysis (fat breakdown) and mitochondrial fat oxidation in the liver — is the mechanistic explanation favored in the literature [7]. For comparative context: a systematic review of 26 RCTs in 15,491 adults without diabetes found retatrutide 12 mg produced weight loss of up to 22.1% (95% CI 19.3%–24.9%) at 48 weeks, exceeding figures for tirzepatide 15 mg (up to 17.8% at 72 weeks) and semaglutide 2.4 mg (up to 13.9% at 68 weeks) in the same literature scan — though no head-to-head trial has been conducted, and the comparison is descriptive, not a ranked finding [9]. See [retatrutide results](/results) for the full numeric summary, and [Retatrutide research](/research) for mechanistic detail. ## What does retatrutide do Retatrutide simultaneously activates three receptors that control appetite, glucose metabolism, and energy expenditure. The GLP-1 receptor arm slows gastric emptying (food moves through the stomach more slowly, extending fullness) and suppresses appetite via hypothalamic signaling. The GIP receptor arm enhances insulin secretion after meals and influences fat tissue remodeling. The glucagon receptor arm raises energy expenditure — the body burns more calories at rest — and stimulates hepatic (liver) lipid breakdown. The combination is what distinguishes retatrutide from GLP-1–only or GLP-1/GIP dual agonists: glucagon receptor activation adds an energy-expenditure component that the earlier drug classes do not carry. Cryo-EM structural analysis confirmed retatrutide engages all three receptors, and measured its relative potency at approximately 8.9× native GIP at the GIP receptor, 0.3× at glucagon receptor, and 0.4× at GLP-1 receptor versus their respective endogenous hormones [3]. ## Is retatrutide fda approved No. Retatrutide is investigational — it has not been approved by the FDA or any regulatory agency as of mid-2026. It is currently in Phase 3 trials under Eli Lilly's TRIUMPH program, which covers obesity, type 2 diabetes, cardiovascular outcomes, and chronic kidney disease. No regulatory submission has been made; a filing would follow the completion and review of Phase 3 data. The compound should not be confused with tirzepatide (approved for type 2 diabetes and obesity) or semaglutide (approved for type 2 diabetes and obesity) — those are distinct compounds with approved indications. Retatrutide is their successor candidate, still in trials. ## Retatrutide availability Retatrutide is not commercially available. Access is limited to enrolled participants in registered clinical trials (TRIUMPH and related studies). A gray market for research-labeled retatrutide peptide vials exists outside clinical trials, but such products are unregulated, of unverified identity and purity, and carry no clinical oversight. The FDA issued more than 50 warning letters to retatrutide vendors in 2025, citing violations of the Federal Food, Drug, and Cosmetic Act. The status of such materials is unrelated to the approved drug that Eli Lilly may eventually file for — gray-market vials are not that product. ## When will retatrutide be available No approval timeline has been confirmed by Eli Lilly or any regulator. Phase 3 trials (TRIUMPH-1, TRIUMPH-2, TRIUMPH-3, and dedicated cardiovascular and kidney outcome studies) are actively enrolling and running as of mid-2026. These trials need to complete, be analyzed, and have data submitted to the FDA and other agencies before any approval decision. Based on the Phase 3 timeline and standard regulatory review periods, analysts have speculated about a potential 2026–2027 NDA filing window, but that is analyst modeling, not official guidance. This dossier will note when Phase 3 data are published. --- An independent appraisal of the published retatrutide trial record — each figure traced to its study, the Phase 3 questions held open, nothing here prescribed or dispensed.