Retatrutide

Definition

Retatrutide is an investigational peptide that acts as an agonist at three receptors at once — the glucose-dependent insulinotropic polypeptide receptor, the GLP-1 receptor, and the glucagon receptor ^[12]. It is a further step along the line that runs from single-agonist to dual-agonist incretin drugs, and it is in active late-stage development.

It is also sold, today, as research-use-only material. This index tracks it because that combination — a real drug candidate with a real trial program and no lawful route to a person outside a trial — is the position readers most often misread.

Evidence

The published TRIUMPH-1 phase 3 report used a treatment-regimen analysis and reported mean weight change of minus 25.0 percent in the highest-strength group versus minus 3.9 percent on placebo at 80 weeks ^[19]. Those figures should not be interchanged with the earlier sponsor headline below. TRIUMPH-2 reported substantial weight reductions in adults with type 2 diabetes, alongside gastrointestinal adverse events and more hypotension and dysesthesia than placebo ^[20]. A smaller DXA substudy addresses a separate question: fat loss versus lean-mass loss, with only 103 participants completing treatment and paired scans ^[17]. The body-composition review explains that denominator and why it is not a muscle-preservation guarantee.

The trial record exists and it is the sponsor's. Across two name variants PubMed returns 178 indexed records, of which 109 carry the Humans subject heading, 8 the clinical-trial publication type, and 7 the randomized-controlled-trial type ^[1]. All eight were opened and read, and every one belongs to the development program: a phase 1b multiple-ascending-dose trial in type 2 diabetes, phase 2 trials in obesity and in type 2 diabetes, a phase 2a trial in metabolic dysfunction-associated steatotic liver disease, body-composition and lipid substudies, and a phase 3 trial ^[1].

The phase 2 obesity trial is the result the market reacted to and the one most often quoted secondhand ^[2]; a phase 3 trial in people with type 2 diabetes and inadequate glycemic control on diet and exercise has since been published ^[3]. Reporting either as evidence of approval is the common error here, and the distinction is not subtle: a trial establishes what a compound does under study conditions, and an approval establishes that a specific product may be sold to be used.

The phase 3 obesity program has since read out. TRIUMPH-1 randomized 2,339 adults with obesity, or overweight with a weight-related condition, and without diabetes; the earlier sponsor release reported average weight loss of 28.3 percent at 80 weeks at the highest dose tested against 2.2 percent on placebo ^[9], and the registry lists the trial as completed, with primary completion in April 2026 ^[11]. TRIUMPH-2, in type 2 diabetes, and TRIUMPH-3, in obesity with established cardiovascular disease, met their primary endpoints in July 2026, and Lilly states that it plans to submit a biologics license application in the first quarter of 2027 ^[10]. The sponsor's own release says the molecule is legally available only to participants in its clinical trials ^[9].

The eight trial-type records are also the reason a count alone tells a reader nothing about legality. Ipamorelin has two and no route; retatrutide has eight and no route; semaglutide has hundreds and an approval. The number that decides the legal question is not in the literature at all.

Lawful access

There is no lawful United States supply route outside a clinical trial. No approved product containing retatrutide exists: a query of Drugs@FDA by active ingredient returns no records for it, in the October 2026 check in which the same query returned a record for bremelanotide and none for a deliberately invented ingredient name ^[4].

FDA has stated the compounding position in its own words rather than leaving it to inference: retatrutide and cagrilintide cannot be used in compounding under federal law, they are not components of FDA-approved drugs, and they have not been found safe and effective for any condition ^[5]. The substance appears in no category of the section 503A bulks list published on May 14, 2026, and it has never been nominated for one ^[6].

The agency has also acted on research-use-only sales. In March 2026 it issued warning letters to two firms whose websites offered retatrutide, finding the products to be unapproved new drugs; both letters state that despite labeling marketing the products for research use only and not for human consumption, evidence obtained from the firms' own websites establishes that the products are intended to be drugs for human use ^[7][8]. Those letters are disclosure of what FDA has stated, and nothing here adjudicates a business. The research-only page explains what the labeling posture is and is not.

Related molecules

Retatrutide sits with the GLP-1 receptor agonists, where it is the only member without an approval: semaglutide and tirzepatide are approved with their shortages resolved, and liraglutide is approved and still listed in shortage. The human trial record prints this molecule's eight trials beside molecules with none, which is the clearest way to see that the trial count and the legal position are separate facts.

Two other investigational drugs pair the glucagon receptor with GLP-1, without GIP. Survodutide is an acylated peptide from Boehringer Ingelheim ^[13] that met its phase 3 SYNCHRONIZE-1 endpoints in April 2026, with up to 16.6 percent average weight loss at 76 weeks against 3.2 percent on placebo ^[14]; mazdutide, an oxyntomodulin analogue licensed from Lilly, was approved in China in June 2025 ^[15]. None of the three, and neither cagrilintide nor amycretin, has a record in Drugs@FDA ^[16]. The incretin pipeline tracker sets every late-stage candidate beside the approved drugs.

Elsewhere in this index