Retatrutide ('Reta'): Trial Results, Price, Availability - and Why 'Reta Peptide' Online Is Risky

Key takeaways

• Retatrutide (LY3437943) is Lilly's once-weekly peptide that activates three receptors at once: GIP, GLP-1 and glucagon. In its phase 2 trial, 12 mg a week produced 24.2% mean weight loss at 48 weeks; in the phase 3 TRIUMPH-1 trial, 25.0% at 80 weeks by intention to treat, the largest figure any obesity drug has produced in a pivotal trial.
• It is not approved anywhere. Lilly says it plans to file with FDA in the first quarter of 2027, which puts any approval in late 2027 or beyond. Nobody can prescribe it, no pharmacy can compound it, and the only legitimate access is a trial or Lilly's narrow physician-requested early access program.
• The price is unknown because there is no product. The only "retatrutide prices" online are for unlabeled vials that FDA has called unapproved drugs in warning letters of March 31 and August 24, 2026.
• The side effects are the GLP-1 class effects plus two of its own: skin dysesthesia (burning, tingling, hypersensitivity) in about one in eight participants at the higher doses in TRIUMPH-1, and one in five at 12 mg in the knee-osteoarthritis trial, plus a dose-related rise in heart rate. Discontinuation for side effects reached 11.3% at 12 mg in TRIUMPH-1 versus 4.9% on placebo.
• The risks of a vial bought online are specific: unknown content, a glucagon-driven drug with no dosing data outside trials, and two 2026 case reports of hospital admissions after online-sourced "reta".

Retatrutide at a glance

Also called

LY3437943, reta, reta peptide, triple G agonist, GIP/GLP-1/glucagon receptor triple agonist

Class

Single synthetic peptide that activates the GIP, GLP-1 and glucagon receptors (a triple agonist)

Route

Once-weekly subcutaneous injection in trials, escalated in steps from a 2 mg starting dose

FDA status

Investigational. Not approved in any country as of October 2026; Lilly plans to file with FDA in the first quarter of 2027. Vials sold online are unapproved drugs and were the subject of FDA warning letters in March and August 2026.

FDA Category 2 (compounding restricted)

No

Available by prescription (US)

Not as a prescription product

Best-studied use

Obesity with and without type 2 diabetes (phase 2 and the phase 3 TRIUMPH program), liver fat, knee osteoarthritis pain and obstructive sleep apnea

Typical monthly cost (telehealth, 2026)

None. There is no legitimate product to price; Lilly has not announced a price, and the only access outside trials is a physician-requested early access program

What retatrutide is and how it works

Retatrutide is a single synthetic peptide designed to activate three receptors that the body's own meal hormones use: the GLP-1 receptor (the target of semaglutide), the GIP receptor (added by tirzepatide), and the glucagon receptor. In cell studies it has balanced glucagon and GLP-1 activity and stronger GIP activity. In obese mice, the glucagon component added a rise in energy expenditure on top of the reduction in food intake driven by the GLP-1 and GIP components; in the first human study, a single dose was tolerated like other incretin drugs and its pharmacokinetics supported once-weekly injection, with a weight effect still measurable six weeks after one dose (Coskun 2022).

The glucagon receptor is the interesting and the awkward part. Glucagon is the hormone that raises blood sugar between meals by telling the liver to release glucose; it also raises energy expenditure and drives the liver to burn fat. A drug that stimulates it on purpose has to pair that with enough GLP-1 and GIP activity to keep glucose down, and the phase 2 trial in type 2 diabetes was partly a test of whether that balance holds. It did: HbA1c fell by up to 2 percentage points. The same mechanism is why retatrutide produced the largest liver-fat reductions yet seen in a drug trial, and why the trials watch heart rate and blood pressure closely.

Like semaglutide and tirzepatide, retatrutide reduces appetite and slows the stomach; the gastrointestinal side effects are the same family, and the phase 2 trial showed they are smaller if the dose is started at 2 mg rather than 4 mg and escalated slowly (Jastreboff 2023).

What the evidence actually shows

Phase 2 (2023): the 24.2% result

The trial that made "reta" a search term enrolled 338 adults with obesity (or overweight plus a weight-related condition), without diabetes, and randomized them to retatrutide 1, 4, 8 or 12 mg weekly or placebo for 48 weeks. Weight loss at 24 weeks, the primary endpoint, was 7.2%, 12.9%, 17.3% and 17.5% versus 1.6% with placebo. At 48 weeks it was 8.7%, 17.1%, 22.8% and 24.2% versus 2.1%. At 12 mg, every participant lost at least 5%, 93% lost at least 10% and 83% lost at least 15%. Gastrointestinal events were dose-related and mostly mild to moderate; heart rate rose with dose, peaked at 24 weeks and then declined (Jastreboff 2023).

A substudy of the same trial looked at 98 participants with fatty liver disease (MASLD) and at least 10% liver fat. At 24 weeks liver fat had fallen by 42.9%, 57.0%, 81.4% and 82.4% at the four doses versus a 0.3% rise on placebo, and 86% of the 12 mg group had normal liver fat (under 5%) (Sanyal 2024).

Phase 3: the TRIUMPH program (2025 to 2026)

Four phase 3 trials had reported by October 2026.

TRIUMPH-4 (knee osteoarthritis), December 2025. The first phase 3 readout, in adults with obesity and knee osteoarthritis treated for 68 weeks with 9 or 12 mg or placebo. Lilly reported weight loss of up to 28.7% (about 71 pounds) and a reduction in WOMAC knee-pain score of up to 4.5 points (75.8%) versus 2.4 points (40.3%) on placebo; about one in eight treated participants reported no knee pain at all by the end. Dysesthesia occurred in 8.8% on 9 mg, 20.9% on 12 mg and 0.7% on placebo, and 12.2%, 18.2% and 4.0% stopped because of adverse events (TRIUMPH-4, Patient Care Online 2025). These are company-reported figures; the full paper has not appeared.

TRIUMPH-1 (obesity), May 2026 topline, NEJM September 2026. 2,339 adults with obesity and no diabetes were randomized to 4, 9 or 12 mg or placebo for 80 weeks. By intention to treat (the estimand that counts everyone randomized, including those who stopped), mean weight change was 17.6%, 23.7% and 25.0% versus 3.9%. Prespecified subgroups showed less knee pain (574 participants with osteoarthritis) and fewer sleep-apnea events per hour (243 with obstructive sleep apnea) (Jastreboff 2026). Lilly's "efficacy estimand", which models what happens if participants stay on treatment, gave 19.0%, 25.9% and 28.3%, with 62.5% of the 12 mg group losing at least a quarter of their body weight and 45.3% losing at least 30%; a 104-week extension in 532 participants with a BMI of 35 or more reached 30.3% (Lilly, May 21, 2026). When you see "30% weight loss" in a headline, that is the number: two years, the heaviest participants, people who stayed on the drug.

TRIUMPH-2 (obesity with type 2 diabetes), July 2026 topline, Lancet October 2026. 1,152 adults treated for 80 weeks. By intention to treat, weight fell 11.9%, 16.8% and 18.8% versus 5.1%; by Lilly's efficacy estimand, 12.7%, 19.1% and 20.8% versus 4.0%; HbA1c fell by 1.4 to 1.6 points versus 0.2. Diarrhea (27 to 34% versus 13%) and nausea (14 to 28% versus 8%) were the most common events; hypotension (up to 6% versus under 1%) and dysesthesia (4 to 7% versus 1%) were more frequent than with placebo; 12% of the 9 mg group and 8% of the 12 mg group stopped because of adverse events or death, versus 5% on placebo, with the seven deaths across the trial judged unrelated to the drug by investigators (Bellido 2026) (Lilly, July 23, 2026).

TRIUMPH-3 (severe obesity with cardiovascular disease), July 2026 topline. 1,949 adults with a BMI of 35 or more and established cardiovascular disease, 80 weeks: weight loss 21.6% (9 mg) and 22.6% (12 mg) versus 3.2%, with 9.8% and 13.5% stopping for adverse events versus 4.8%. The trial also counted cardiovascular events, and the honest reading is "not yet known": the prespecified five-point MACE analysis gave a hazard ratio of 0.82 (95% CI 0.55 to 1.22) and the three-point analysis 1.12 (0.64 to 1.96), both with confidence intervals crossing 1 because fewer events occurred than expected (Lilly, July 23, 2026). A dedicated outcomes trial will have to answer the heart question that SELECT answered for semaglutide.

Retatrutide claims, graded by the evidence behind them

Claim	Grade	What the evidence shows	Sources
Produces more weight loss than any approved obesity drug has shown in its pivotal trial	A	Phase 2: 24.2% at 48 weeks with 12 mg (338 adults). TRIUMPH-1: 25.0% at 80 weeks by intention to treat (2,339 adults), 28.3% by efficacy estimand, 30.3% in a 104-week extension of the heaviest participants. Cross-trial comparison only.	Jastreboff 2023; Jastreboff 2026; Lilly 2026a
Lowers blood sugar and weight in type 2 diabetes	A	TRIUMPH-2: 1,152 adults, 80 weeks; weight down 11.9 to 18.8% by intention to treat versus 5.1%; HbA1c down 1.4 to 1.6 points versus 0.2.	Bellido 2026; Lilly 2026b
Reduces liver fat	B	Phase 2 substudy, 98 participants with MASLD: liver fat down 81 to 82% at 24 weeks on 8 and 12 mg; 86% reached normal liver fat on 12 mg. Histology (MASH resolution, fibrosis) not yet studied.	Sanyal 2024
Reduces knee osteoarthritis pain and sleep-apnea events	B	TRIUMPH-1 subgroups: WOMAC pain down 3.5 to 3.6 points versus 1.9 (hybrid estimand); apnea-hypopnea index down 32 to 34 events per hour versus 10. TRIUMPH-4: pain down up to 4.5 points versus 2.4 (company-reported, not yet peer-reviewed). Graded B because these are secondary and subgroup endpoints.	Jastreboff 2026; TRIUMPH-4 2025
Reduces heart attacks and strokes	C	TRIUMPH-3 was underpowered for events: MACE-5 hazard ratio 0.82 (0.55 to 1.22), MACE-3 1.12 (0.64 to 1.96). Risk markers improved; outcomes unproven.	Lilly 2026b
Better than tirzepatide	D	No head-to-head trial has reported. SURMOUNT-5 shows what a direct comparison looks like (tirzepatide 20.2% versus semaglutide 13.7%); nothing equivalent exists for retatrutide.	Aronne 2025
Causes dose-related gastrointestinal effects, dysesthesia, hypotension and a faster heart rate	A	TRIUMPH-1: nausea 29 to 42% versus 15%, vomiting 11 to 25% versus 5%, dysesthesia 5 to 13% versus 1%, discontinuation for adverse events 4.1 to 11.3% versus 4.9%. Phase 2: heart-rate increase peaking at 24 weeks.	Lilly 2026a; Jastreboff 2023; Bellido 2026
Safe and effective at the doses sold online	D	No data: online vials have no verified content, and the trials used slow 4-week escalations from 2 mg with clinical monitoring. Two 2026 case reports describe hospital admissions after online-sourced product.	Buzzi 2026; Branine 2026

What you are promised versus what is documented

The marketing around "reta" borrows the trial numbers and drops the conditions. Sorting the claims:

• Documented: mean weight loss of 25% at 80 weeks by intention to treat, and 28 to 30% in people who stayed on the top dose for up to two years; large liver-fat reductions; less knee pain and fewer apnea events; improved HbA1c in type 2 diabetes.
• Plausible but unproven: fewer heart attacks and strokes (TRIUMPH-3 could not tell); superiority over tirzepatide (no head-to-head); durable benefit after stopping (no withdrawal study has reported, and every GLP-1 withdrawal study so far shows regain).
• Not supported: that the glucagon component "burns fat while sparing muscle" (body-composition data from phase 3 have not been published), that it is gentler than tirzepatide (discontinuations for side effects were higher at the top dose), that any dose below those studied does anything, or that the vial you can buy today contains what the trial participants received.

Side effects and the glucagon question

The gastrointestinal profile is the GLP-1 class profile at a higher intensity. In TRIUMPH-1, at 4, 9 and 12 mg versus placebo: nausea 28.6%, 38.4% and 42.4% versus 14.8%; diarrhea 25.2%, 34.1% and 32.0% versus 13.5%; constipation 23.8%, 25.9% and 26.1% versus 10.9%; vomiting 10.6%, 22.8% and 25.3% versus 4.8%. Discontinuation for adverse events was 4.1%, 6.9% and 11.3% versus 4.9% (Lilly, May 21, 2026). The 4 mg dose, which produced 17.6% weight loss, had fewer discontinuations than placebo; the price of the extra seven points at 12 mg was roughly a doubling of nausea and a tripling of discontinuations.

Two effects are more specific to retatrutide. Dysesthesia, an umbrella term for burning, tingling, skin hypersensitivity and pain of the skin, affected 5.1%, 12.3% and 12.5% at the three doses in TRIUMPH-1 versus 0.9% on placebo, and up to 20.9% at 12 mg in TRIUMPH-4; Lilly describes the events as mostly mild to moderate and resolving during treatment. Heart rate rose with dose in phase 2, peaking at 24 weeks before declining, and hypotension was reported in up to 6% in TRIUMPH-2 versus under 1% on placebo (Jastreboff 2023) (Bellido 2026).

The glucagon receptor raises a theoretical concern that the trials address but do not close. Glucagon drives the liver to release glucose; in people with type 2 diabetes the GLP-1 and GIP components more than compensated and HbA1c fell. In people who depend on injected insulin, nobody has tested the balance: the only data are a 2026 case report of a man with type 1 diabetes who developed ketosis and acute kidney injury after taking an online-sourced product during a gastrointestinal illness (Branine 2026). The trials enrolled adults without diabetes or with type 2 diabetes; type 1 diabetes has not been studied.

By class, retatrutide will almost certainly carry the warnings of its relatives: the rodent thyroid C-cell tumor boxed warning (a contraindication for anyone with a history of medullary thyroid carcinoma or MEN 2), pancreatitis, gallbladder disease, dehydration-related kidney injury, slowed gastric emptying during anesthesia, and pregnancy. Whether it earns any of its own will be decided by the label FDA writes.

Retatrutide vs tirzepatide vs semaglutide

The comparison that matters for a decision in 2026 is between the two approved drugs; our compounded semaglutide versus tirzepatide guide covers that choice in depth (Aronne 2025). Retatrutide belongs in the "what comes next" column, and the gap between 21% and 25% is smaller than the gap between a labeled pen and an unlabeled vial.

Availability and price: what is known and what is not

Known. Retatrutide is not approved in the United States or anywhere else. On July 23, 2026 Lilly said it is completing the chemistry, manufacturing and controls data package required for a Biologics License Application and plans to submit retatrutide to FDA in the first quarter of 2027 for US approval, with global submissions to follow for obesity, knee osteoarthritis pain and obstructive sleep apnea (Lilly, July 23, 2026). Standard FDA review runs about ten months from acceptance, so the earliest plausible approval is late 2027, and nothing guarantees that date.

Known. In early August 2026 Lilly opened a limited early access program, described by Reuters and the BMJ as compassionate or expanded access, for adults with refractory obesity (persisting despite the highest approved dose of an existing obesity drug), at least two serious weight-related complications under treatment, and no ability to enroll in a retatrutide trial. Clinicians, not patients, submit requests, and Lilly describes the program as consistent with FDA's guidance (Reuters/KSL 2026) (Brown 2026). It is not a launch and it is not a waiting list.

Not known. The price. Lilly has announced none, and the early access terms are not public. For scale, the same company sells brand tirzepatide for $299 to $449 a month through LillyDirect, per our cost guide; whether retatrutide lands near that or above it is speculation. Also not known: the final label, the approved doses, and whether the 4 mg dose, which produced 17.6% weight loss with fewer discontinuations than placebo, will be a maintenance option.

Not a price. Figures quoted for retatrutide vials online. They are prices for an unlabeled powder with no verified identity, purity, sterility or potency, and we do not report them because they are not prices for a medicine.

Why "reta peptide" vials online are unapproved drugs

Every retatrutide vial for sale to the public is sold with a research-use disclaimer, because the sellers know there is no legal way to sell it for human use. In 2026 FDA said in writing that the disclaimer does not work. Its March 31, 2026 warning letter to Gram Peptides covered retatrutide, tirzepatide and bacteriostatic water; its five letters of August 24, 2026 covered retatrutide alongside semaglutide, tirzepatide, tesamorelin and others. In each, FDA rejected the research label in a footnote: the websites' dosing guidance, injection instructions, reconstitution calculators and bundled bacteriostatic water showed the products were intended as drugs for people, which makes them unapproved new drugs under sections 505(a) and 301(d) of the FD&C Act (FDA, Gram Peptides letter) (ArentFox Schiff 2026). The legal tracker lists every letter.

The letters are addressed to sellers. For a buyer the problems are practical, and they are specific to this molecule:

1. Unknown content. No regulator, pharmacist or clinician has checked what is in the vial. It may be retatrutide at the stated amount, a different amount, a different peptide, or a contaminated one. A 2026 BMJ case report describes a woman in her mid-20s admitted with five days of nausea, vomiting and loose stools that did not respond to three antiemetics; the cause was four weekly, escalating injections of a product "reported to contain retatrutide", given in a wellness setting by a self-described life coach. She had not considered the injections a medication (Buzzi 2026).
2. A glucagon agonist without supervision. Retatrutide raises heart rate, lowers blood pressure in some people, and stimulates the liver's glucose output. In the trials, heart rate and blood pressure were monitored throughout. The type 1 diabetes case above shows what the unmonitored version looks like (Branine 2026).
3. No dosing data outside the trials. The trials used low starting doses (2 mg in phase 2, chosen specifically because it reduced nausea and vomiting), stepwise escalation and maintenance doses of 4 to 12 mg. Online dose charts are copied from those protocols or invented; neither comes with the exclusion criteria, the labs or the clinician who stops the escalation.
4. Nobody accountable. No pharmacy label, no beyond-use date, no adverse-event reporting, no one to call.

Dosage: what was studied, not a protocol

We do not publish a reconstitution example for retatrutide, because a reconstitution example is for a prescription with a pharmacy label; our peptide calculator exists for those. A reader working out how many units of a research vial to draw is doing exactly what FDA's 2026 letters describe, and we will not help with the arithmetic.

Legal status in the United States

• Not approved, so it cannot be prescribed, dispensed or sold for human use.
• Not compoundable by any 503A pharmacy or 503B outsourcing facility: it is not a component of an FDA-approved drug, it has no USP monograph, and it is not on FDA's permitted bulk-substances list. No prescription can change that, and a clinic that offers "prescribed retatrutide" is offering a research vial with a signature on it.
• Not a controlled substance. Possessing it is not a crime; the law acts on the seller, as the 2026 warning letters did.
• Importing it for personal use is not permitted; packages can be detained.
• Early access through Lilly's program and enrollment in a trial are the only lawful routes, and both run through a physician.

The legal tracker is updated when any of this changes, including when Lilly files and when FDA acts.

Cost and how to get it: the honest answer

There is no cost because there is nothing to buy. The paths that exist:

1. A clinical trial. Lilly's program continues to enroll in some studies; ClinicalTrials.gov lists them by location, and a clinician can check eligibility.
2. Lilly's early access program, for the narrow group described above, requested by your physician.
3. The approved alternatives now. Tirzepatide and semaglutide are available this month, from a licensed clinician, with labels, at $299 to $449 (Zepbound) and $349 (Wegovy) for cash through the manufacturers' programs, and often through insurance. Someone who needs to lose 20% of their body weight does not need to wait for 25%.

Who should not use it

Outside a trial or Lilly's program: everyone, for the reasons above. If approved, expect the class contraindications its relatives carry: a personal or family history of medullary thyroid carcinoma or MEN 2, prior serious hypersensitivity and pregnancy, with caution in pancreatitis history, severe gastroparesis and insulin-treated diabetes. There are no data in type 1 diabetes, pregnancy, breastfeeding or adolescents.

Bottom line

Retatrutide is the most effective weight-loss drug ever put through a pivotal trial, with 25% mean loss by intention to treat and a side-effect profile that is the GLP-1 class profile turned up, plus skin dysesthesia and a faster pulse. It is also, as of October 2026, a drug that does not exist as a product: not approved, not compoundable, not priced, and at least a year from any pharmacy if Lilly's first-quarter 2027 filing goes to plan. The "reta peptide" you can order tonight is not that drug. It is a vial of unverified powder that FDA has called an unapproved drug, sold with a dose chart copied from a trial that excluded most of the people buying it. If you need to lose weight now, the approved drugs exist, work, and come with a label; if you want retatrutide, the honest route runs through a physician and a calendar, not a checkout page.

Frequently asked questions

+−When will retatrutide be available?

Not before late 2027 at the earliest, and only if FDA approves it. Lilly said on July 23, 2026 that it plans to submit retatrutide to FDA in the first quarter of 2027, once its manufacturing data package is complete. Standard FDA review of a new drug takes about ten months from acceptance of the application. Until approval, the only legitimate routes are a clinical trial or Lilly's physician-requested early access program, which is limited to adults with refractory obesity and at least two serious weight-related complications who cannot join a trial.

+−Is retatrutide legal?

Possessing it is not a crime; selling it for human use is. Retatrutide is an investigational drug with no approval anywhere, it cannot be compounded by any pharmacy (it is not a component of an approved drug, has no USP monograph and is not on FDA's permitted list), and no clinician can lawfully prescribe it outside a trial or an FDA-sanctioned access program. FDA's warning letter to Gram Peptides on March 31, 2026 and its five letters of August 24, 2026 said that research-use labels do not change that when the website explains how to dose and inject it.

+−How much does retatrutide cost per month?

There is no price, because there is no product. Lilly has not announced pricing, and the early access program's terms are not public. For scale, Lilly sells brand tirzepatide (Zepbound) for $299 to $449 a month through LillyDirect in 2026. Prices quoted for retatrutide vials online are not prices for a medicine: the vial has no label, no verified content and no legal path to human use, and we do not report them.

+−What does retatrutide do to digestion?

The same things GLP-1 drugs do, somewhat more often at the higher doses. It slows stomach emptying and reduces appetite; in the phase 3 TRIUMPH-1 trial nausea was reported by 29% to 42% of participants depending on dose (15% on placebo), diarrhea by 25% to 34%, constipation by 24% to 26% and vomiting by 11% to 25%. Most events were mild to moderate and occurred during dose escalation, and the phase 2 trial found that starting at 2 mg rather than 4 mg reduced them. Decreased appetite was also reported more often than with placebo.

+−Is retatrutide better than tirzepatide?

Probably more weight loss, but no head-to-head trial has reported. TRIUMPH-1 produced 25.0% mean weight loss at 80 weeks by intention to treat (28.3% among those who stayed on the 12 mg dose), against 20.9% at 72 weeks in tirzepatide's SURMOUNT-1; those are different trials with different populations and durations. Retatrutide also produced more discontinuations for side effects at the top dose (11.3% versus 4.9% on placebo) and a new side effect, skin dysesthesia, in about one in eight participants on the higher doses. Tirzepatide is approved, labeled and available; retatrutide is none of those.

+−What is grey market retatrutide?

Vials sold online as 'reta' or 'retatrutide' with a research-use disclaimer, usually as a lyophilized powder you reconstitute with bacteriostatic water and dose from a chart the seller or a forum provides. No regulator has tested what is in them; FDA treats them as unapproved drugs, and in 2026 published case reports described a woman hospitalized with five days of refractory nausea and vomiting after four injections in a wellness setting, and a man with type 1 diabetes who developed ketosis and kidney injury after an online-sourced product.

+−Is liraglutide the same as GLP-1?

Liraglutide is a GLP-1 receptor agonist, a modified copy of the hormone GLP-1 that lasts a day instead of minutes, sold as Victoza for diabetes and Saxenda for weight management. Semaglutide is the weekly successor; tirzepatide adds a second receptor (GIP); retatrutide adds a third (glucagon). Each step has produced more weight loss in trials: liraglutide 3 mg about 8 kg over 56 weeks, semaglutide 2.4 mg about 15%, tirzepatide up to 21%, retatrutide 25% by intention to treat in phase 3.

+−Can I get retatrutide through Lilly's early access program?

Only if your physician applies and you meet the criteria Lilly announced in August 2026: age 18 or older, obesity that persists despite tolerating the highest approved dose of an existing obesity medication, at least two serious or life-threatening weight-related complications under treatment, and no way to enroll in an ongoing retatrutide trial. Requests go from clinicians to Lilly, not from patients, and the company describes the program as consistent with FDA's expanded-access guidance. It is not a launch and it is not a waiting list.

Sources

1. StudyJastreboff AM et al. Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial. N Engl J Med 2023;389:514-26. (2023)
2. StudySanyal AJ et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med 2024;30:2037-48. (2024)
3. StudyCoskun T et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: from discovery to clinical proof of concept. Cell Metab 2022;34:1234-47. (2022)
4. StudyJastreboff AM et al. Retatrutide, a triple hormone receptor agonist, for treatment of obesity (TRIUMPH-1). N Engl J Med 2026; published online September 29, 2026. (2026)
5. StudyBellido V et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. Lancet 2026;408:1455-72. (2026)
6. NewsEli Lilly. Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal phase 3 obesity trial (TRIUMPH-1 topline results). Press release via PR Newswire, May 21, 2026. (2026)
7. NewsEli Lilly. Lilly's triple agonist, retatrutide, successful in two additional phase 3 obesity trials (TRIUMPH-2 and TRIUMPH-3 topline results; BLA submission planned for Q1 2027). Press release via BioSpace, July 23, 2026. (2026)
8. NewsPatient Care Online. Retatrutide achieves up to 28.7% weight loss and marked knee pain reduction in phase 3 TRIUMPH-4 trial. December 11, 2025. (2025)
9. NewsBrown C. Retatrutide: obesity drug opens to compassionate use in US after speculation Trump took it. BMJ 2026;394:e100530. (2026)
10. NewsReuters (via KSL). Eli Lilly to offer early access to next-gen obesity drug to some patients. August 4, 2026. (2026)
11. StudyBuzzi RM et al. Emerging risks of health optimisation: refractory nausea associated with peptide injections reported to contain retatrutide. BMJ Case Rep 2026;19. (2026)
12. StudyBranine N et al. Online-sourced retatrutide complicating impending diabetic ketoacidosis in a patient with type 1 diabetes and concurrent Shigella gastroenteritis. Cureus 2026;18:e115260. (2026)
13. StudyAronne LJ et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). N Engl J Med 2025;393:26-36. (2025)
14. RegulatoryFDA. Warning letter to Gram Peptides (retatrutide, tirzepatide and bacteriostatic water sold with research-use labels). March 31, 2026. (2026)
15. NewsArentFox Schiff. RUO-ined: five peptide vendors learn that research use only is not a legal strategy (FDA warning letters of August 24, 2026). September 18, 2026. (2026)