Retatrutide
Also sold as: LY3437943, Triple G, GGG tri-agonist
Retatrutide (LY3437943) is not approved by FDA for any indication, and FDA states it 'cannot be used in compounding under federal law' — it appears on neither the 503A Bulks List, the 503B Bulks List, nor FDA's drug shortage list, leaving no lawful US route to a compounded retatrutide product, and FDA has issued warning letters treating retatrutide sold online as an unapproved new drug. Its human evidence is nonetheless genuine: in the Phase 3 TRANSCEND-T2D-1 trial published in The Lancet in June 2026, investigators randomised 537 adults with type 2 diabetes to weekly subcutaneous retatrutide or placebo and reported substantially greater HbA1c reduction at week 40 in the retatrutide groups — but those trials used Eli Lilly's investigational material, FDA says retatrutide has 'not been found safe and effective for any condition', and FDA warns that products sold as retatrutide direct to consumers are of unknown quality and may be harmful.
Which molecule this is. A single synthetic peptide that agonises three receptors — glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon — described as such in the Phase 2 report (NEJM 2023) and the Phase 3 report (Lancet 2026). Unlike BPC-157 or TB-500, there is no fragment-versus-full-length ambiguity in the literature: 'retatrutide' and 'LY3437943' denote one investigational Eli Lilly molecule. The ambiguity is elsewhere — nothing verifies that a vial sold as 'retatrutide' by a research-chemical vendor contains that molecule, at that purity, at any stated content. It is not a component of any FDA-approved drug product, so no vial of it comes from an approved supply (recorded, sourced, under FDA findings).
FDA status
This is in active clinical development with an identifiable sponsor and registered trials. It is not approved, and being in trials is not evidence that it works.
In active clinical development with an identifiable sponsor and registered trials. Not approved. Being in trials is not evidence that it works.
“Retatrutide is not the subject of an applicable USP or NF monograph, is not a component of an FDA-approved drug product, and does not appear on the 503A Bulks List.”Checked against the source on .
503A compounding
This substance was never nominated for use in compounding under section 503A.
Absent from Categories 1, 2 and 3 of the bulks list updated 2026-05-14 — verified by fetching and text-extracting the document directly; the string 'retatrutide' does not occur in it. Recorded as never-nominated rather than withdrawn-from-nomination: FDA's 2025 letter walks through each of the three statutory 503A prongs and reports that retatrutide satisfies none, without referencing any nomination, category placement or withdrawal — which a letter written specifically to explain its 503A status would have had occasion to mention. First-in-human dosing was 2019 (NCT03841630), well after the nomination window that produced the Category 1/2/3 cohort. HONEST LIMIT: absence from the categories is equally consistent with withdrawal (BPC-157 is also absent), so this rests on the letter's silence plus chronology, not on a document stating 'never nominated'. If a nomination record surfaces, this field changes. 'Never nominated' IS NOT A LOOPHOLE AND IS NOT PERMISSION — it is the opposite. The withdrawn peptides at least have a nomination history; retatrutide has no lawful compounding pathway under either 503A or 503B, which FDA states in terms.
“Retatrutide is not the subject of an applicable USP or NF monograph, is not a component of an FDA-approved drug product, and does not appear on the 503A Bulks List.”Checked against the source on .
Evidence
Efficacy established by adequate, well-controlled trials in humans.
ADMINISTRATION CHECK PASSED, EXPLICITLY. Retatrutide is a synthetic investigational drug, not an endogenous peptide, so the biomarker trap that empties MOTS-c's and TB-500's apparent trial counts does not apply here — but the check was run per-study anyway rather than assumed. In TRANSCEND-T2D-1 (NCT06354660), a 40-week Phase 3 double-blind placebo-controlled trial at 48 sites in the USA, Mexico and India, investigators randomised 537 adults with type 2 diabetes to subcutaneous retatrutide or placebo weekly; they reported substantially greater reduction in HbA1c at week 40 in every retatrutide group than with placebo. In the earlier Phase 2 obesity trial (NCT04881760, NEJM 2023), investigators randomised 338 adults and reported substantially greater weight reduction at 48 weeks in the highest retatrutide group than with placebo. The per-arm figures are left to the cited papers deliberately: an amount beside a frequency reconstructs a regimen, and this record does not publish one. Both trials administered the drug; both were funded by Eli Lilly; the ClinicalTrials.gov intervention record for each reads 'Administered SC'. WHAT THE TIER DOES AND DOES NOT MEAN. It means: efficacy on the endpoints those trials measured — glycaemic control and body weight — is established by adequate, well-controlled human trials. It does NOT mean approved, and it does not mean safe: FDA's own position is that retatrutide has 'not been found safe and effective for any condition' (recorded under FDA findings). It does not mean the outcomes that matter longest are known — the cardiovascular and kidney outcomes trial (NCT06383390, n=10,000, Eli Lilly, Phase 3) began 2024-04-30, is active and not recruiting, has posted no results, and runs about five years. Most of the Phase 3 programme is likewise unreported: of 14 Eli Lilly Phase 3 registrations confirmed on ClinicalTrials.gov on 2026-07-16, none has results posted there, and exactly one (TRANSCEND-T2D-1) is peer-reviewed and published. Other Phase 3 outcomes exist so far only as company press releases, which are not a primary evidentiary source and are not cited here. And none of it transfers to grey-market product: these findings describe Lilly's investigational material under trial conditions, not a vial bought from a vendor.
“Participants were randomly assigned (1:1:1:1) to receive retatrutide […] or placebo by once-weekly subcutaneous injection.”Checked against the source on .
What FDA found
FDA’s own words. These are the most citable thing on this site, and the least likely to appear anywhere funded by someone selling the compound.
FDA states that retatrutide cannot be used in compounding under federal law, and that it has not been found safe and effective for any condition.
Read this against the evidence tier rather than instead of it. Both are true and they are not in conflict: a published Phase 3 trial can establish efficacy on its endpoints while FDA — which has not reviewed a marketing application, because none has been approved — has made no safety-and-effectiveness finding. 'Not found safe and effective' is a statement about the approval process, not a finding that the trials failed. The vendor corpus quotes the trial results without this sentence; the cautious corpus quotes this sentence as though it meant the drug does not work. Both are misreadings.
FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss — FDA, 15 June 2026“Retatrutide and cagrilintide cannot be used in compounding under federal law. Additionally, these are not components of FDA-approved drugs and have not been found safe and effective for any condition.”
Checked against the source on .FDA finds retatrutide satisfies none of the three statutory conditions for a bulk drug substance under 503A, and does not appear on the 503B Bulks List or FDA's drug shortage list.
The shortage-list point is what closes the door that semaglutide and tirzepatide briefly left open. Compounders could supply those during declared shortages; retatrutide has never been on the shortage list because it has never been marketed, so that route never existed for it. FDA sent this letter to NABP, the Federation of State Medical Boards and the National Council of State Boards of Nursing — it is addressed to prescribers and dispensers, not only to compounders.
Letter to the National Association of Boards of Pharmacy re: Compounded Drug Products Containing Retatrutide — FDA, 31 March 2025“Retatrutide does not appear on the 503B Bulks List, nor does it appear on FDA's drug shortage list. Therefore, compounded retatrutide products would not at this time qualify for the exemptions under section 503B of the FD&C Act.”
Checked against the source on .FDA has warned telehealth companies for marketing unapproved retatrutide directly to consumers, API distributors for selling it to compounders, and outsourcing facilities for repackaging it.
Enforcement here reaches the whole chain, not just the manufacturer — prescriber-facing telehealth included. Consistent with the Watkins indictment (D. Utah, 1:26-cr-00015, 2026-04-01), which charges misbranding under 352(b): sourcing and labeling are the line, and a compound's category status — or absence from every category, as here — is neither the safety line nor the criminal line. The quote is FDA's own three-item list, reproduced in full; the run-on reads oddly because the source renders it as a lead-in and three bullets, and flattening it was preferred to silently rewriting FDA's words.
FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss — FDA, 15 June 2026“The agency has warned: Telehealth companies for marketing unapproved drugs such as retatrutide, including instances of direct marketing to consumers. Active pharmaceutical ingredient distributors for selling retatrutide and other GLP-1 drugs to compounders. Outsourcing facilities for repackaging retatrutide.”
Checked against the source on .In a warning letter to a retatrutide seller, FDA found the products to be unapproved new drugs and held that 'Research Use Only' labeling did not defeat evidence of intended use.
This is the sentence that answers the question the market actually asks about retatrutide — not 'is the molecule legit' but 'does the research-use-only label make the sale lawful'. FDA's answer, in this letter and consistently across the 2026-03-31 tranche, is that intended use is established from the seller's own website copy, and a disclaimer contradicted by that copy is not a defence. FDA also recorded a general finding about the dosage form rather than the molecule: 'injectable drug products can pose risks of serious harm to users… bypass some of the body's key defenses against toxins and microorganisms'. WHAT THIS IS NOT: not a finding about retatrutide's pharmacology, and not a finding that the Lilly trials are wrong. It is a finding about a seller. The letter concerns Gram Peptides specifically; it is cited here as evidence of FDA's legal position on retatrutide sold this way, not as a claim about any other vendor.
Warning Letter — Gram Peptides (MARCS-CMS 721806) — FDA, 31 March 2026“Despite statements on your product labeling marketing your products for “Research Use Only,” and “not intended for human consumption, medical use, or veterinary use,” evidence obtained from your website establishes that your products are intended to be drugs for human use.”
Checked against the source on .FDA has established a green list import alert (66-80) directed at GLP-1 active pharmaceutical ingredients with potential quality concerns entering the US supply chain.
Included because it is the concrete mechanism behind the abstract 'unknown quality' warning: FDA is stopping material at the border, which tells you where it judges the risk to sit. Read the scope precisely, in both directions. The alert is aimed at GLP-1 APIs broadly, not at retatrutide by name, so it is recorded as context for the supply chain retatrutide arrives through rather than as a retatrutide-specific action. And FDA states its own limits: the alert 'does not apply to GLP-1 API from manufacturers that … appear to be in compliance', and 'does not stop the legal importation into the U.S. market of GLP-1 APIs from compliant API manufacturers, nor does it create any new limits on the legal compounding of GLP-1 drugs'. That last clause does nothing for retatrutide, which has no lawful compounding to limit.
FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss — FDA, 15 June 2026“The agency has established a green list import alert (66-80) to help stop GLP-1 active pharmaceutical ingredients (APIs) that have potential quality concerns from entering the U.S. supply chain.”
Checked against the source on .
Documented safety signals
FDA has warned companies illegally selling unapproved retatrutide falsely labeled 'for research purposes' or 'not for human consumption', sold direct to consumers with dosing instructions, and recommends consumers not purchase them, as they are of unknown quality and may be harmful.
This is the safety signal that actually applies to the way people obtain retatrutide. It is not a signal about the molecule — it is a signal about the supply. Note what is NOT claimed here. FDA's GLP-1 page does spell out failure modes for illegally sold product — wrong or harmful ingredients, 'too little, too much or no active ingredient at all' — but that language sits in its counterfeit-Ozempic section and in a bullet list whose lead sentence scopes it to 'illegally marketed semaglutide and tirzepatide'. The section that names retatrutide says 'unknown quality and may be harmful' and stops there, so that is where this record stops too; importing the more specific failure modes would attribute to retatrutide what FDA wrote about other drugs. The trial evidence cannot speak to any of it either way, because the trials used Lilly's material.
Letter to the National Association of Boards of Pharmacy re: Compounded Drug Products Containing Retatrutide — FDA, 31 March 2025“Additionally, FDA has warned companies that have illegally sold unapproved drugs containing retatrutide and other ingredients that are falsely labeled “for research purposes” or “not for human consumption.” These products have been sold directly to consumers for human use with dosing instructions. The agency recommends that consumers not purchase these products which are of unknown quality and may be harmful to their health and encourages health care providers to discuss this issue with their patients.”
Checked against the source on .In the Phase 2 obesity trial (n=338), investigators reported that the most common adverse events with retatrutide were gastrointestinal, dose-related and mostly mild to moderate, and that dose-dependent increases in heart rate peaked at 24 weeks and declined thereafter.
Attributed to the trial, and scoped to it. The most frequently reported adverse events in the ClinicalTrials.gov results posting for NCT04881760 were nausea (91 participants affected), decreased appetite (62), diarrhoea (45), vomiting (34) and constipation (32). Two limitations bound this: 338 participants over 48 weeks cannot characterise uncommon or long-latency harms, and the heart-rate finding was observed under monitored titration with a controlled starting dose — a condition that does not exist outside a trial. The Phase 3 report (Lancet 2026) characterised the profile as 'consistent with molecules with GLP-1 agonist activity'.
Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial — The New England Journal of Medicine, 10 August 2023“The most common adverse events in the retatrutide groups were gastrointestinal; these events were dose-related, were mostly mild to moderate in severity, and were partially mitigated with a lower starting dose […]. Dose-dependent increases in heart rate peaked at 24 weeks and declined thereafter.”
Checked against the source on .A Phase 2 registration for retatrutide (NCT07467447) is sponsored by Hudson Biotech and carries an official title identical, word for word, to Eli Lilly's genuine Phase 2 trial NCT04881760.
Recorded as a safety signal because registry contamination is a hazard to the reader, not a curiosity. ClinicalTrials.gov is self-reported and unvetted: registration is not vetting, and 'RECRUITING' is a sponsor's assertion. NCT07467447 matches the known contaminated cluster on every marker — sponsor Hudson Biotech, which sells research peptides; a single site; start date 2026-02-15; status recruiting; zero results — and its official title is a verbatim clone of Lilly's, exactly as NCT07481747 clones Lilly's SURMOUNT-1. It is not cited as evidence anywhere in this record and should not be mistaken for the real NCT04881760, whose results are posted and published in NEJM. Verified 2026-07-16 against the ClinicalTrials.gov API. Related registrations in the same cluster are self-marked: NCT07481734 carries '(Mock Study)' in its official title and NCT07487363 states in its own brief summary that it is fictional — and vendor sites are already laundering that one as '2026 human trial data'.
A Phase 2 Study of Once-Weekly LY3437943 Compared With Placebo in Participants Who Have Obesity or Are Overweight With Weight-Related Comorbidities — ClinicalTrials.gov, 15 February 2026Checked against the source on .
Questions people actually ask
Every answer cites the document behind it. Where the honest answer is “nobody knows”, that is the answer you will get.
- Is retatrutide legal in 2026?
No — there is no lawful way to obtain retatrutide in the United States outside a clinical trial. FDA wrote to the National Association of Boards of Pharmacy on 31 March 2025 that retatrutide is not the subject of a USP or NF monograph, is not a component of an FDA-approved drug product, and does not appear on the 503A Bulks List — so it satisfies none of the three statutory conditions for a bulk drug substance, and compounded retatrutide products 'would not at this time qualify for the exemptions under section 503A of the FD&C Act'. FDA found the same for section 503B — retatrutide appears on neither the 503B Bulks List nor FDA's drug shortage list. NABP circulated the letter to state boards of pharmacy with the summary that compounding with retatrutide 'is prohibited by all pharmacies compounding under either Section 503A or 503B'.
Letter to the National Association of Boards of Pharmacy re: Compounded Drug Products Containing Retatrutide — FDA, 31 March 2025“Retatrutide is not the subject of an applicable USP or NF monograph, is not a component of an FDA-approved drug product, and does not appear on the 503A Bulks List. Therefore, compounded retatrutide products would not at this time qualify for the exemptions under section 503A of the FD&C Act.”
Checked against the source on .- Did FDA approve retatrutide?
No. Retatrutide is not approved by FDA for any indication, in any population, by any route, and as of 15 June 2026 FDA states that retatrutide and cagrilintide 'are not components of FDA-approved drugs and have not been found safe and effective for any condition'. Retatrutide is an investigational Eli Lilly molecule still in Phase 3 development. Note precisely what FDA's phrase means: 'not been found safe and effective' describes the absence of an approval decision, because no marketing application for retatrutide has been approved — it is not a finding that the clinical trials failed.
FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss — FDA, 15 June 2026“Retatrutide and cagrilintide cannot be used in compounding under federal law. Additionally, these are not components of FDA-approved drugs and have not been found safe and effective for any condition.”
Checked against the source on .- Can I get retatrutide from a compounding pharmacy?
No. FDA has stated in a letter to the National Association of Boards of Pharmacy, and again on its own website, that retatrutide cannot lawfully be used in compounding under either section 503A or section 503B of the Federal Food, Drug, and Cosmetic Act. Retatrutide does not appear on the 503B Bulks List, and — unlike semaglutide and tirzepatide, which compounders could supply during declared shortages — it has never appeared on FDA's drug shortage list, because it has never been marketed. FDA has warned outsourcing facilities for repackaging retatrutide and API distributors for selling it to compounders. A pharmacy or telehealth service offering compounded retatrutide is not operating in a grey area FDA has yet to address; it is doing something FDA has addressed twice, in writing, by name.
Letter to the National Association of Boards of Pharmacy re: Compounded Drug Products Containing Retatrutide — FDA, 31 March 2025“Retatrutide does not appear on the 503B Bulks List, nor does it appear on FDA's drug shortage list. Therefore, compounded retatrutide products would not at this time qualify for the exemptions under section 503B of the FD&C Act.”
Checked against the source on .- Is there any human evidence that retatrutide works?
Yes — retatrutide is one of the few compounds sold on the peptide market with a published, peer-reviewed Phase 3 randomised trial. In TRANSCEND-T2D-1 (NCT06354660), a 40-week double-blind trial at 48 sites in the USA, Mexico and India reported in The Lancet on 13 June 2026, investigators randomised 537 adults with type 2 diabetes to weekly subcutaneous retatrutide or placebo and reported substantially greater reduction in HbA1c at week 40 in every retatrutide group than with placebo. Earlier, in a Phase 2 obesity trial reported in the New England Journal of Medicine in 2023, investigators randomised 338 adults and reported substantially greater weight reduction at 48 weeks in the highest retatrutide group than with placebo. Both trials were funded by Eli Lilly and used Lilly's investigational material. That evidence describes the molecule under trial conditions and says nothing about the contents, purity or identity of a vial sold as 'retatrutide' by a research-chemical vendor.
Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial — The Lancet, 13 June 2026“Participants were randomly assigned (1:1:1:1) to receive retatrutide […] or placebo by once-weekly subcutaneous injection.”
Checked against the source on .- Is retatrutide sold 'for research purposes only' legal to buy?
No. FDA has held that a 'research use only' or 'not for human consumption' label does not make selling retatrutide lawful, because intended use is established from the seller's own marketing rather than its disclaimer. In a warning letter of 31 March 2026 to Gram Peptides, FDA found that despite labeling the products 'Research Use Only' and 'not intended for human consumption', evidence from the firm's website established the products were 'intended to be drugs for human use' — making them unapproved new drugs whose introduction into interstate commerce violates sections 301(d) and 505(a) of the Federal Food, Drug, and Cosmetic Act. FDA added that these products are especially concerning because injectable drug products 'bypass some of the body's key defenses against toxins and microorganisms'.
Warning Letter — Gram Peptides (MARCS-CMS 721806) — FDA, 31 March 2026“Based on our review, these products are unapproved new drugs under section 505(a) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), 21 U.S.C. 355(a). As explained further below, introducing or delivering these products for introduction into interstate commerce violates sections 301(d) and 505(a) of the FD&C Act, 21 U.S.C. 331(d) and 355(a).”
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