# Retatrutide: Published Phase 2 and Phase 3 Trial Data, Summarized > Retatrutide (LY3437943) is an investigational triple agonist at GIP, GLP-1, and glucagon receptors. Read the Phase 2 and Phase 3 trial data — cited, no spin. An independent digest of Phase 1b, Phase 2, and Phase 3 findings on the investigational triple agonist (GIP + GLP-1 + glucagon). Every number cited. No prescription, no vendor, no clinic. ## The short version Retatrutide is an investigational drug — not approved anywhere, not available by prescription. It is being studied by Eli Lilly in clinical trials under the code name LY3437943. The basic idea: it activates three hormone signals at once — GLP-1 (appetite suppression), GIP (insulin enhancement), and glucagon (calorie-burning). No approved drug does all three together yet. The trials so far have produced large weight-loss numbers. In the biggest Phase 2 study, people with obesity who received the highest dose lost an average of about 24% of their body weight over 48 weeks — roughly 58 lbs for a 240-lb person — compared to 2% with placebo. That figure comes from a controlled trial, not a testimonial. This site summarizes what the published studies have measured. It does not sell anything. It does not give medical advice. It does not help anyone obtain retatrutide outside a clinical trial. [Retatrutide effects](/effects) — including what people report and what to watch for — are on the next page. [Retatrutide research](/research) covers the mechanism in full detail. ## What retatrutide is Retatrutide (LY3437943) is a 39-amino-acid synthetic peptide developed by Eli Lilly and Company. It is a triple agonist — a single molecule that simultaneously activates three receptors: GLP-1R (glucagon-like peptide-1 receptor), GIPR (glucose-dependent insulinotropic polypeptide receptor), and GCGR (glucagon receptor). No approved obesity or diabetes drug activates all three receptors in a single compound as of 2026. The molecule is acylated with a C20 fatty-diacid chain for albumin binding, extending its half-life to approximately 6 days — consistent with once-weekly subcutaneous injection, as confirmed in the Phase 1b pharmacokinetics trial [4]. Molecular weight: 4,731.33 Da. CAS: 2381089-83-2. This is a synthetic compound; there is no natural endogenous source that matches its structure. ## What the trials have measured Three phases of clinical data have been published: **Phase 1b (Urva et al., 2022):** 72 adults with type 2 diabetes. Once-weekly subcutaneous doses from 0.5 mg up to 12 mg over 12 weeks. Confirmed ~6-day half-life. At the highest dose cohort, placebo-adjusted weight loss reached -8.96 kg (90% CI -11.16 to -6.75) over 12 weeks [4]. **Phase 2 obesity (Jastreboff et al., 2023, NEJM):** 338 adults with obesity or overweight-plus-comorbidity. 48 weeks, once-weekly subcutaneous 1/4/8/12 mg. Mean body-weight change at 12 mg: -24.2% vs -2.1% placebo [1]. GI adverse events were dose-related and mostly mild-to-moderate. Dose-dependent heart-rate increase peaked at week 24. **Phase 2 type 2 diabetes (Rosenstock et al., 2023, Lancet):** 281 adults with type 2 diabetes. 36 weeks. At 12 mg, HbA1c (glycated hemoglobin — a marker of average blood glucose over three months) fell by -2.02% at 24 weeks; body weight fell by -16.94% at 36 weeks vs -3.00% placebo [2]. No severe hypoglycemia, no deaths. **Phase 2 liver-fat substudy (Sanyal et al., 2024, Nature Medicine):** 98 participants with MASLD (metabolic dysfunction-associated steatotic liver disease, formerly called fatty liver disease), no diabetes. At 12 mg over 24 weeks, liver fat fell by -82.4% relative; 86% of participants reached normal liver-fat levels (<5% by MRI-PDFF — a non-invasive liver-fat scanner) [5]. Effect was sustained to 48 weeks (-86.0% at 12 mg). A 2025 meta-analysis pooling three RCTs (878 patients) found a mean pooled weight reduction of -14.33% vs placebo, with no statistically significant difference in overall adverse-event rate (RR 1.11, P=0.24) [8]. See [retatrutide results](/results) for a full tabulation of these findings by trial. ## Phase 3 program (TRIUMPH) Eli Lilly's TRIUMPH series is the pivotal Phase 3 program for retatrutide as of 2026. Registered trials include TRIUMPH-1 and TRIUMPH-2 (obesity), alongside dedicated arms studying type 2 diabetes, cardiovascular outcomes (NCT06383390), chronic kidney disease (TRANSCEND-CKD; NCT05929066), obstructive sleep apnea, and knee osteoarthritis [10]. A Phase 3 head-to-head trial against tirzepatide is also registered, which will be the first direct efficacy comparison between the two investigational / approved incretin compounds in a controlled trial. No TRIUMPH Phase 3 results have been published as of mid-2026. Regulatory approval — if it follows a positive readout and FDA review — would come after the Phase 3 data package is submitted. The TRIUMPH program is the milestone to watch. This site will update its summaries when data are published. ## Is retatrutide fda approved No. Retatrutide is not FDA-approved and not approved by any regulatory agency as of mid-2026. It is an investigational compound in Phase 3 clinical trials. It has no approved indication, no approved labeling, no approved dose, and is not available as a prescription product in any country. Retatrutide availability is limited to clinical trial enrollment. Obtaining it outside a clinical trial means sourcing gray-market research-labeled material of unverified identity, purity, and sterility — a distinct risk discussed on the [effects and safety page](/effects). When will retatrutide be available? That depends on TRIUMPH Phase 3 readouts and FDA review timelines, neither of which has been publicly confirmed as of 2026. --- Trial data on one investigational compound — published, cited, and held by no clinic and no vendor.