Retatrutide
Triple GIP/GLP-1/Glucagon Agonist (Lilly)
Evidence grade 4 of 5, Strong. Read how the Atlas grades evidence.
Retatrutide's investigational efficacy rests on replicated, high-quality RCT evidence: the phase 2 obesity trial (Jastreboff et al., NEJM 2023, 338 adults) showed 24.2% mean weight loss at 12mg over 48 weeks, the phase 2 diabetes trial (Rosenstock et al., Lancet 2023, 281 adults) showed HbA1c reductions near 2 points, the phase 2a MASLD substudy (Sanyal et al., Nature Medicine 2024, 98 adults) showed roughly 86% liver-fat reduction, and this was extended by positive phase 3 topline results (TRIUMPH-1, 2,339 adults, announced May 21 2026) with up to about 28 to 30% weight loss at 80 weeks and a published phase 3 diabetes trial (TRANSCEND-T2D-1, Lancet 2026). The grade 4 grade applies to the drug's efficacy signal as an investigational agent, not to any marketed product; retatrutide is NOT FDA-approved as of July 2026, phase 3 TRIUMPH-2 and TRIUMPH-3 remain ongoing, long-term safety is still being established, and the gray-market 'research chemical' retatrutide sold online is unapproved, cannot legally be compounded, and has drawn FDA warning letters.
Counted on the record: 19 human studies, 19 randomized trials, 21,382 participants, 4 animal studies, 15 lab studies.
- FDA
- Not FDA-approved. Phase 3 obesity trial TRIUMPH-1 topline reported positive May 2026 (n=2,339); TRIUMPH-2, TRIUMPH-3 and the cardiovascular outcomes trial ongoing. NDA submission anticipated but not yet filed as of July 2026.
- WADA
- Not currently on the WADA Prohibited List, though incretin/metabolic agents are monitored; status may change.
Reference only. Not medical advice.
What can go wrong
GI adverse events common during dose escalation, dose-dependent heart-rate increase and expected lean-mass loss consistent with the incretin class, long-term safety still being established.
Talk to a clinician before taking this, particularly if you have a heart condition. The Atlas can tell you what has been studied about Retatrutide. It cannot tell you how it would interact with your body, your history, or anything else you are taking, and nothing on this page is a reason to start.
A first-in-class triple receptor agonist targeting GIP, GLP-1, AND glucagon receptors. Its Phase 3 TRIUMPH-1 topline (May 21, 2026) showed 28.3% average weight loss at 80 weeks on the 12mg dose, the largest figure of any obesity drug to date. FDA submission is expected in late 2026.
Phase 3 hit 28.3% weight loss in May 2026. The biggest number in obesity medicine.
What people take it for
What it is taken for. Approval, where it exists, covers only some of these.
How it works
Retatrutide is the first triple agonist: a single peptide that switches on three receptors at once, GIP, GLP-1, and glucagon. The GLP-1 and GIP halves do what they do in tirzepatide, curbing appetite, slowing the stomach, and improving insulin response. The third receptor, glucagon, is the innovation. On its own glucagon raises blood sugar, but paired with strong GLP-1 activity its other effects come forward: it increases energy expenditure, drives the liver to burn its own fat, and markedly reduces liver fat. Adding that metabolic accelerator on top of appetite suppression is why retatrutide has produced the largest weight loss of any drug yet tested.
- Step 1GLP-1 and GIP receptorsBinds to the glucagon-like peptide-1 (GLP-1) receptor, the glucose-dependent insulinotropic polypeptide (GIP) receptor, and the glucagon (GCG) receptor
- Step 2Cellular CascadesBinds to each receptor, the receptor changes shape and couples with internal G-protein complexes. This activates the enzyme adenylate cyclase, raising intracellular cyclic AMP (cAMP) levels which act as a secondary messenger to stimulate downstream pathways like protein kinase A (PKA)
- Step 3GLP-1GLP-1 pathway signals the brain to reduce appetite and increase feelings of fullness (satiety). Slows gastric emptying (the rate at which food leaves the stomach), helping prolong satisfaction after eating. Stimulates glucose-dependent insulin secretion from the pancreas while suppressing inappropriate glucagon secretion during high blood sugar states.
- Step 4GIPFurther augments insulinotropic responses and helps regulate nutrient storage, fat metabolism, and cellular glucose uptake.
- Step 5Glucagon ReceptorIncreases energy expenditure (encouraging the body to burn more calories at rest) and promotes lipolysis (the breakdown of stored body fat). Helps clear excess fat accumulation from the liver, offering therapeutic benefits for metabolic dysfunction-associated steatotic liver disease (MASLD).
Still in clinical trials phase 3. This mechanism was shown only in cell tests and obese mice, with no human data confirming it works the same way in people.
Retatrutide (Eli Lilly's LY3437943) is a synthetic peptide of about 36 amino acids, engineered as a single molecule that binds and activates the GIP, GLP-1 and glucagon receptors together, balanced so the glucagon effect aids fat-burning without letting blood sugar climb. Like the other incretin drugs it carries a fatty-acid modification that binds albumin and allows once-weekly injection. Building one molecule to hit three receptors in the right proportions is the core pharmacological achievement, and it is also what its overseas copyists are trying to reproduce from Lilly's published patent sequence.
- Class
- Triple GIP/GLP-1/glucagon
- Size
- 39 alpha-amino acids + γ-glutamate + serine
- Route
- Weekly injection
- Doses studied
- 2 to 12 mg
- Status
- Investigational (Phase 3)
- Approved
- Nowhere yet
The 41 vs 39 Amino Acid Debate
Retatrutide has 39 alpha-amino acids + side chain that make it 40 amino acids. However, Eli Lily, trying to protect patent life and future compounding-shortage related issues, wants to categorize it as a biologic. FDA's rule says: a biologic is more than 40 alpha-amino acids. EL and FDA are debating this over court.
Safety in detail
- Gastrointestinal effects are the most common and grow with the dose. Dysesthesia, an odd skin-tingling feeling tied to the glucagon part, is the side effect most specific to retatrutide, and a urinary-tract-infection signal and small heart-rate increases are being watched. The glucagon effect can nudge blood sugar up, which the GLP-1 part offsets, but long-term metabolic effects are still being established.
Children and teenagers
There is no pediatric use of retatrutide, no pediatric data, and no approval in anyone of any age, since the drug is still investigational even for adults. Any use in a minor would be gray-market misuse of an experimental compound, with all the dosage-verification and oversight problems multiplied. The broader debate about treating adolescent obesity with incretin drugs, which is live for the approved agents semaglutide and liraglutide, does not extend to retatrutide: it is far too early, and nothing about an unapproved, unverified, self-sourced injection belongs anywhere near a child.
What people get wrong
Often saidRetatrutide is an approved weight-loss medicine.
ActuallyRetatrutide is still investigational, and the FDA warns that unapproved GLP-1-class products sold as retatrutide are unsafe.
Often saidRetatrutide products sold online as research peptides are the same as the drug tested in trials.
ActuallyProducts sold outside trials are only purported to be retatrutide and are unverified, and cannot legally be compounded; Australian health authorities have reported liver injury cases linked to an unapproved product labelled Retatrutide, though a cause has not been established.
Often saidEveryone who takes retatrutide loses about 30% of their body weight.
ActuallyReported weight loss figures are averages from specific trial doses and durations, ranging from about 19% to 30.3%, with the phase 3 numbers being unreviewed company topline results.
Often saidRetatrutide causes weight loss by making the body burn more energy.
ActuallyThis mechanism is yet to be tested in humans. Human trials in progress.
Often saidRetatrutide's side effects are only mild stomach upset.
ActuallyTrial side effects were mostly gut related but sometimes led to stopping treatment, and separate lab and unverified self-report data suggest possible heart-rate effects not confirmed in humans.
Often saidPeople using retatrutide bought outside trials get the same results as trial participants.
ActuallyAn unreviewed preprint found that unapproved retatrutide use was associated with weaker weight loss and more cardiovascular symptoms, though this shows association, not cause and effect.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
No one earns a cent from an approved retatrutide product, because it does not exist as a medicine anywhere. The future beneficiary is clear: Eli Lilly holds the patent and is building manufacturing capacity for a launch expected around 2027 to 2028, with analysts projecting a premium price near $1,200 to $1,500 a month given its efficacy. The money flowing today is entirely gray-market: overseas factories copying Lilly's patented sequence and the online vendors who resell their output as "research only." This is essentially bootlegging a patent-protected, still-experimental drug, a numbers game vendors play against the manufacturer, and the people profiting are precisely the ones with no accountability for what is in the vial.
How we got here
Retatrutide is an investigational once-weekly peptide developed by Eli Lilly that simultaneously activates three receptors: GIP, GLP-1, and glucagon, the first such triple agonist to advance to Phase 3. It is being evaluated across Lilly's TRIUMPH Phase 3 program for obesity, type 2 diabetes, and related conditions, and as of 2026 it has not received regulatory approval. Because no approved product exists, any retatrutide sold direct to consumers is an unapproved gray-market copy of unverified purity and safety.
Retatrutide began as Lilly molecule LY3437943, conceived to push beyond the dual agonist tirzepatide by adding glucagon-receptor activity for extra fat-burning. Its 2023 Phase 2 results in the New England Journal of Medicine, about 24% weight loss at 48 weeks, immediately marked it as the most powerful obesity drug yet seen and launched the multi-trial TRIUMPH program. Through 2025 and 2026 the Phase 3 readouts confirmed and extended that promise, reaching roughly 30% in severe obesity. In parallel, and unusually, a gray market sprang up around the unapproved drug, with copies made from its patent sequence sold online, turning retatrutide into a case study in demand outrunning both evidence and regulation.
Discovery and patent
2017 to 2019
- 2020Discovery work later described in Cell Metabolism (2022)GIP-based peptide engineered to activate GIP, GLP-1 and glucagon receptors; development code LY3437943.
- Dec 21, 2017WO2019125938A1 patent family, earliest priority dateEarliest claimed filing date for the key retatrutide-related patent family; not necessarily the exact discovery date.
- Dec 14, 2018PCT/US2018/065663International patent application filed for long-acting incretin analogs with triple-receptor activity.
- Jun 27, 2019WO2019125938A1 publishedPatent application became public, disclosing the relevant peptide designs and supporting experiments.
Preclinical and Phase 1
2019 to 2022
- Mar 13–Jul 25, 2019NCT03841630 Phase 1Single ascending doses in healthy volunteers to assess safety, tolerability and pharmacokinetics.
- Dec 18, 2019–Dec 28, 2020NCT04143802Weekly LY3437943 tested for 12 weeks in people with type 2 diabetes, with placebo and dulaglutide comparators.
- Jun 1, 2021Diabetes / ADA abstract 679-PPublic preclinical report: major weight loss in diet-induced obese mice, largely from fat loss, with improved glucose measures.
- Aug 18, 2022Cell Metabolism, discovery-to-proof-of-concept paperFull molecular, receptor, animal and early human story published; supported reduced intake plus increased energy expenditure.
- Aug 18, 2022Cell Metabolism; NCT03841630Single 6 mg dose produced notable mean weight loss; pharmacokinetics supported once-weekly dosing; gastrointestinal effects were common.
- Oct 27, 2022The Lancet; NCT04143802Phase 1b results published: dose-dependent weight loss and HbA1c reduction over 12 weeks, with gastrointestinal events most common.
Phase 2
2023 to 2023
- 2023Phase 2Phase 2 (NEJM): ~24% weight loss at 48 weeks, the highest yet, plus a large liver-fat reduction.
Phase 3
2024 to 2027
- 2024-2025Phase 3The multi-trial TRIUMPH Phase 3 program scales up; recruitment starts and after preliminary information and results it gains popularity in the RUO/Grey Market space.
- Dec 2025Phase 3 TRIUMPH studiesTRIUMPH-4 (obesity with knee osteoarthritis): 28.7% weight loss.
- Mar 2026Type 2 Diabetes Phase 3 StudyTRANSCEND-T2D-1 (diabetes): A1c down ~2%, weight down up to ~17%.
- May 2026Obesity Phase 3 StudyTRIUMPH-1 (pivotal obesity): 28.3% at 80 weeks, up to 30.3% at 104 weeks
- Late 2026-2027New Drug Application - Into MarketNDA filing expected; FDA decision realistic in 2027, launch perhaps 2028.
The numbers behind the grade
- Peak weight loss
- ~28 to 30%
- Mechanism
- Triple agonist
- Status
- Phase 3
- NDA
- Late 2026 to 2027
- Approved
- Nowhere yet
- WADA
- Prohibited (S0)
The people taking it
The most anticipated drug in the obesity pipeline and the holder of the biggest weight-loss number in medicine. Known online as "reta," it has the rare distinction of being heavily used and discussed before it is approved anywhere, which is exactly what makes it both exciting and concerning.
The other buys it gray-market, and that group skews toward experienced GLP-1 users and biohackers, many of them men, have already used tirzepatide or semaglutide.
Used legitimately only within Eli Lilly’s global trials.
Set against the alternatives
Retatrutide is, by the numbers, the most effective weight-loss agent ever tested. Its roughly 28 to 30% sits about 6 to 8 points above tirzepatide and roughly double semaglutide, and it approaches the range of bariatric surgery. The trade-off is tolerability: higher rates of dysesthesia and, in sicker populations, more discontinuation than the approved drugs. Against the field, it sits clearly at the top of efficacy, above tirzepatide, semaglutide, the oral pill orforglipron, and Novo's CagriSema, which actually failed to beat tirzepatide. The crucial asterisk is that all of those competitors are approved and retatrutide is not, so for now it wins on paper while the others win on availability.
| Semaglutide (Wegovy) | GLP-1 | ~15% | Approved |
|---|---|---|---|
| Tirzepatide (Zepbound) | GIP + GLP-1 | ~20 to 22.5% | Approved |
| Orforglipron (Foundayo) | Oral GLP-1 | ~11 to 12% | Approved 2025 |
| CagriSema | Semaglutide + amylin | ~23% (failed vs tirzepatide) | FDA decision late 2026 |
| Retatrutide | GIP + GLP-1 + glucagon | ~28 to 30% | Investigational |
What we do not know
- What TRIUMPH-2 (diabetes) and TRIUMPH-3 (cardiovascular) show, and whether efficacy holds across populations.
- Whether the glucagon-driven effects on heart rate and blood sugar prove safe over the long term.
- Whether dysesthesia and discontinuation limit real-world use once it is approved.
- How large the health toll of pre-approval gray-market use will turn out to be.
- When, and at what price, it actually reaches the market.
- Whether Retatrutide will be categorized as a peptide or biologic
What could change
The remaining TRIUMPH readoutsTRIUMPH-2 (diabetes) and TRIUMPH-3 (cardiovascular) are expected in 2026 and will complete the filing package.Liver diseaseThe strong glucagon-driven liver-fat effect makes MASLD and MASH a major target.Cardiovascular and renal outcomesA large outcomes trial will test whether the weight loss prevents deaths and major events.New indicationsKnee osteoarthritis, sleep apnea and even low back pain are under study as obesity-linked conditions.The approval itselfThe defining near-term event is whether and when it reaches the market, which would convert today’s gray-market demand into regulated access.
Legal status
Retatrutide is not approved for sale in any country. Eli Lilly is expected to file for approval in late 2026 or early 2027.
Status current as of July 2026. Regulatory positions change, sometimes quickly.
The market for this
What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.
There is no legitimate price yet. Analysts expect a premium when it launches, plausibly $1,200 to $1,500 a month, reflecting its class-leading efficacy. Gray-market vials are sold at typical research-peptide prices, but the apparent savings come with the real cost of unverified identity, uncertain dose, and no medical supervision.
Every gray-market vial traces to overseas synthesis, predominantly in China, of a molecule copied from Lilly’s published patent. Nothing in that chain is regulated or independently verified by default, so a buyer cannot know whether a vial holds real retatrutide, the right dose, or contaminants. Even a third-party certificate, uncommon in this market, cannot substitute for the manufacturing controls a real drug undergoes.
No legitimate supplyRetatrutide is not manufactured for sale as a medicine in any country, so there is no approved, traceable chain. Lilly’s only product is the trial supply.ChinaThe entire gray-market supply originates with overseas chemists, predominantly in China, who synthesize a copy from Lilly’s published patent sequence and sell bulk or finished vials online.United States and onlineDomestic and international "research peptide" vendors repackage and resell that material as research-use-only, shipping directly to consumers who inject it.The verification gapBecause nothing here is regulated, identity and dose are unverified; a journalist who tested the scene found vials that could contain multiples of the stated dose.
At a glance
- Amino acid sequence
- YAQGTFTSDYSILLDKKAQAAFIEYLLEGGPSSGAPPPS
- Amino acids
- 36
- TRIUMPH-1 (May 2026)
- 28.3% at 80 weeks
- TRIUMPH-4
- 28.7% weight loss
- Mechanism
- Triple receptor agonist
- FDA filing
- Expected late 2026 - Early 2027
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about Retatrutide.
Nothing outstanding on this one.
Sources
A 2023 phase 2 double-blind, randomized, placebo-controlled trial of retatrutide enrolled 338 adults with a body-mass index of 30 or higher, or a BMI of 27 to under 30 with at least one weight-related health condition. Once-weekly retatrutide led to substantial weight reduction at both 24 and 48 weeks, with the effect growing with dose; at 12 mg over 48 weeks, mean weight loss was 24.2%. The trial authors concluded that these results justify further study in a phase 3 trial.
Jastreboff AM et al., New England Journal of Medicine (NEJMoa2301972)
A 2023 phase 2 randomised, double-blind, double-dummy trial published in The Lancet compared retatrutide with placebo and dulaglutide 1.5 mg in adults aged 18 to 75 with type 2 diabetes across 42 US centres. Participants received once-weekly injections of placebo, dulaglutide 1.5 mg, or one of six retatrutide maintenance dose arms ranging from 0.5 mg to 12 mg, with the primary outcome measured as HbA1c change at week 24 and secondary outcomes including HbA1c and body weight at week 36. The authors report that retatrutide produced clinically meaningful improvements in blood sugar control and robust weight reductions with a safety profile consistent with GLP-1 receptor agonists and GIP and GLP-1 receptor agonists, results that informed the choice of doses for the subsequent phase 3 programme, though the abstract does not provide the magnitude of these changes.
In a phase 2a liver-fat substudy of 98 adults with metabolic dysfunction-associated steatotic liver disease and at least 10% liver fat on MRI, retatrutide at doses from 1 to 12 mg led to up to an 82% reduction in liver fat at 24 weeks, compared to placebo. Completion rates were lower in the placebo group (58%) than in the retatrutide groups (77% to 90%), with 77.6% of all participants completing the substudy overall.
In Eli Lilly's May 21, 2026 topline announcement for the phase 3 TRIUMPH-1 trial, adults with obesity or overweight and at least one weight-related health condition (but no diabetes) on the investigational drug retatrutide lost an average of 28.3% of body weight over 80 weeks at the 12 mg dose, with 45.3% losing at least 30%; the 4 mg dose produced an average loss of 19.0% at 80 weeks. A study extension reported up to 30.3% average weight loss at 104 weeks in people with a starting BMI of 35 or higher. Discontinuation due to side effects occurred in 4.1%, 6.9%, and 11.3% of participants on the 4 mg, 9 mg, and 12 mg doses respectively, compared with 4.9% in a comparison group whose identity was not fully specified in the release. These are company-reported topline figures, not peer-reviewed data.
Eli Lilly investor press release, May 21 2026 (via PR Newswire)
Independent coverage of TRIUMPH-1 phase 3 topline weight-loss figures and program status
A double-blind, randomised, phase 3 trial published in The Lancet in 2026 randomly assigned 537 adults with type 2 diabetes not controlled by diet and exercise alone to retatrutide 4 mg, 9 mg, or 12 mg, or placebo. Average HbA1c fell by 1.69% with retatrutide 4 mg, 1.86% with 9 mg, and 1.94% with 12 mg, compared with 0.81% with placebo, with all three doses significantly better than placebo (p<0.0001). The trial authors conclude that retatrutide used on its own significantly improved blood sugar control and reduced body weight in this population, with a side effect profile consistent with other GLP-1 receptor agonists.
FDA warns that unapproved GLP-1-class drugs sold for weight loss, including retatrutide labeled 'not for human consumption,' are unapproved and unsafe
Gray-market retatrutide is unapproved and not legally compoundable; FDA issued warning letters to multiple vendors, many still selling as of May 2026
Registered phase 2 diabetes study record (dosing, design, comparator)
Clinical concern is rising about off-label prescribing of unapproved retatrutide ahead of approval. A clinical professor of medicine at NYU Langone Health has expressed concern that if retatrutide is given to patients who do not require this degree of weight loss, there can be significant loss of lean muscle, gallstones especially with rapid weight loss, and nutritional deficiencies, though this represents her clinical view rather than study findings. Reddit users taking retatrutide most often described increased appetite, fatigue, increased energy, nausea, food cravings, insomnia and a faster heart rate, in contrast with mostly gut-related side effects reported in trials, with over half of users reporting at least one side effect.
In cell-based assays, LY3437943 (retatrutide) showed balanced activity at the glucagon and GLP-1 receptors and greater activity at the GIP receptor. In obese mice, the compound lowered body weight by raising energy expenditure and reducing calorie intake, with these effects attributed to glucagon-receptor-linked increases in energy use and GIP-receptor- and GLP-1-receptor-linked reductions in food intake. The compound was engineered as a single peptide designed for weekly injection, built on earlier dual GIP and GLP-1 receptor work with glucagon receptor activity added in an attempt to improve energy use, weight loss, and blood sugar control. However, these findings come from cell tests, obese mice, and isolated mouse tissue; no human data shows that the same mechanism operates the same way in people.
A 12-week phase 1b proof-of-concept trial published in The Lancet in 2022 gave multiple weekly doses of LY3437943 (retatrutide) to adults aged 20 to 70 who had type 2 diabetes for at least 3 months, with an HbA1c of 7.0 to 10.5% and a BMI of 23 to 50 in a double-blind, placebo-controlled randomised design with doses stepped up across groups. The trial authors report that LY3437943 showed an acceptable safety profile, that the way the body handled it suggests it suits once-weekly dosing, and that it gave robust reductions in blood sugar and body weight in people with type 2 diabetes.
A 2026 medRxiv preprint, not peer reviewed, analyzed Reddit posts and comments through December 2025 from retatrutide-specific and broader peptide and weight-management communities using a language-model tool to identify posts reporting personal use and extract symptoms matched to standard medical terms. Among 13,589 Reddit users whose posts were classed as describing current retatrutide use, 7,823 reported at least one symptom after exclusions; the most common were increased appetite, fatigue, increased energy, nausea, food cravings, insomnia, and faster heart rate, which differed from phase 2 trial findings dominated by gut-related side effects. However, these are self-reports with no comparison group, the products used were not verified, the Reddit accounts were classified by software rather than confirmed as actual users, and the authors describe the findings as hypothesis-generating.
In a 2025 lab study of isolated mouse heart tissue, retatrutide at 100 nanomolar did not increase the pumping force of electrically paced left atrial tissue but did speed up the beating rate in spontaneously beating right atrial tissue. The faster beating rate appeared to work through the glucagon receptor, as it was counteracted by adomeglivant, a glucagon receptor blocker, and weakened by H89, a PKA inhibitor, while rolipram strengthened it. The effect was independent of beta-adrenoceptors, since propranolol did not block it, but was blocked by carbachol and reversed by atropine, implicating muscarinic receptors. These are findings from isolated mouse heart tissue, not human studies.
Contractile effects of retatrutide in isolated mouse atrial preparations (PMC12678479).
A 2023 letter to the New England Journal of Medicine responding to the phase 2 retatrutide obesity trial notes that ongoing trials are testing whether treating obesity with medicines lowers the risk of cardiovascular events, and that which kinds of events might be reduced is debated and may depend on the type of obesity. Only the letter's opening lines were readable, so its full argument is not recorded here.
LY3437943 (retatrutide), a triple glucagon, GIP, and GLP-1 receptor agonist discovered in 2022 and reported in Cell Metabolism, lowered body weight and improved blood sugar control in obese mice through increased energy use and reduced calorie intake. In a first human study with single rising doses, the drug showed safety and tolerability similar to other incretin-class drugs, with pharmacokinetics supporting once-weekly dosing and lower body weight persisting up to day 43 after a single dose, though the number of participants and statistical values for weight change were not stated in the available summary.
A 2024 paper in Cell Discovery by Li and colleagues reports cryo-electron microscopy maps, a way of imaging molecules in near-atomic detail, of retatrutide bound to each of its three target receptors: GLP-1R, GIPR and GCGR. The paper uses these structures to explain how one peptide can switch on all three receptors. This is a laboratory structure study, not a study in animals or people, and the detailed structural findings were not part of the text read this turn.
Structural insights into the triple agonism at GLP-1R, GIPR and GCGR manifested by retatrutide
A 2026 paper in The Journal of Clinical Endocrinology and Metabolism measured blood fats and other small molecules in fasting blood samples from two randomized, placebo-controlled phase 2 trials of retatrutide. It included 282 people with obesity from one trial and 213 people with type 2 diabetes from the other, treated for 48 and 36 weeks. The analysis was planned after the trials ended and is described by its authors as exploratory. The summary read states the design and aims, but its specific results were not part of the text read this turn.
A 2026 design paper in Diabetes, Obesity and Metabolism describes the TRIUMPH phase 3 program for retatrutide as four trials: TRIUMPH-1 and TRIUMPH-2 for weight management with nested studies of sleep apnea and knee osteoarthritis, TRIUMPH-3 for weight management in people with cardiovascular disease, and TRIUMPH-4 as a stand-alone knee osteoarthritis trial. The main measures planned are percent change in body weight for weight management, change in the Apnea-Hypopnea Index (a count of breathing pauses during sleep) for obstructive sleep apnea, and change in the WOMAC pain score (a standard knee pain questionnaire) for knee osteoarthritis. The paper describes plans and does not report results.
A 2026 preprint not yet peer reviewed found that among 652 people reported as using retatrutide, 71.2% of those with documented supply routes obtained a product purported to be retatrutide outside a clinical trial. The preprint reports an association between accelerating use of unapproved retatrutide and weaker weight loss and increased cardiovascular symptoms in people using products purported to be retatrutide, though association does not establish causation.
TRIUMPH-1 is a randomized, double-blind, placebo-controlled study of once-weekly retatrutide in people without type 2 diabetes who have obesity or overweight, running under a master protocol that includes groups with knee osteoarthritis or obstructive sleep apnea. The study lasts about 89 weeks with up to 24 visits, with an optional addendum allowing about 500 participants to continue treatment for up to 24 more weeks. The ClinicalTrials.gov registration lists actual enrollment as 2,335 people with no results posted, though the topline account describes 2,339 adults; these figures have not been reconciled.
A Study of Retatrutide (LY3437943) in Participants Who Have Obesity or Overweight (TRIUMPH-1)
In a December 2025 press release, Eli Lilly reported topline results from its phase 3 TRIUMPH-4 trial of retatrutide in 445 adults with obesity or overweight and knee osteoarthritis: participants given retatrutide 12 mg lost an average of 28.7% of their body weight, or 71.2 lbs, at 68 weeks, and the treatment lowered knee pain scores by up to an average of 75.8%, improved measures of physical function, and left more than 1 in 8 treated patients completely free of knee pain. These are company-reported topline results; detailed findings have not yet been peer reviewed.
PubChem, the chemistry database of the US National Institutes of Health, holds a record titled Retatrutide (sodium salt), CID 171934787, which prints the molecular formula C221H342N46O68. The record is for the sodium salt form, so this formula is not presented as the formula of every form of retatrutide. As printed, the formula lists no sodium atom; that has not been checked against the full record.
On this deeper read, the record still gives what it gave before: a patent application titled Incretin analogs and uses thereof, WO2019125938A1, carrying a priority date of December 21, 2017, a filing date of December 14, 2018, and a publication date of June 27, 2019, as printed on its Google Patents page. Looking specifically for what that page itself says about formulation, stability, or pharmacological class, this reading could not open WO2019125938A1's own abstract, claims, or description text again in this session. Repeated attempts to reach that page instead returned a separately numbered, same-day, same-titled sibling filing (WO2019125929A1) and other, later patents that merely cite WO2019125938A1 as one of several applications said to cover GLP-1, GIP and glucagon receptor triple agonist peptides meant for once-weekly, protracted dosing. That description comes from those other filings pointing at WO2019125938A1, not from WO2019125938A1's own printed page text, so it is not recorded here as the source's own statement. No formulation detail, no stability data, and no pharmacological class label attributed to WO2019125938A1 itself could be confirmed in this reading. The page also still does not print the development code LY3437943, so which example in the patent corresponds to retatrutide remains unconfirmed, and these dates still come before the discovery year of 2020 that the entry currently records.
WO2019125938A1 - Incretin analogs and uses thereof - Google Patents
The Victorian Department of Health in Australia issued an alert on June 19, 2026 reporting six cases of acute liver injury in Victoria since January 2026 in people who used an unapproved peptide product labelled Retatrutide, with similar cases possibly reported in other Australian states and territories; investigations into product contents and potential contaminants are ongoing, though the alert does not establish that retatrutide itself caused the injuries. The products linked to these cases were bought online, through friends, and through social media accounts, while in Australia most peptides are prescription medicines. The department strongly advises people not to use any unapproved peptide products, including those labelled Retatrutide, and asks doctors to inquire about peptide use in patients presenting with signs of liver injury.
Toxicity linked to unapproved peptide product labelled Retatrutide
The studies that matter
Phase 2 (NEJM)2023
Up to 24.2% weight loss at 48 weeks on the 12mg dose.
TRIUMPH-42025
First Phase 3 readout: 28.7% weight loss; Phase 2 had shown an 86% reduction in liver fat.
TRIUMPH-12026
28.3% mean weight loss at 80 weeks on the 12mg dose; up to 30.3% in higher-BMI participants at 104 weeks.