RESEARCH DIGEST // INVESTIGATIONAL COMPOUND
Retatrutide trial data. No spin. Read the studies.
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 — including what people report and what to watch for — are on the next page. Retatrutide 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 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.
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.