Retatrutide Phase 3 results: what is public (Nov 2026)

Key points

• Retatrutide is an investigational drug. It is not approved anywhere we could verify, and Lilly says it plans to submit a US application in the first quarter of 2027 [9][11].
• Phase 3 results are public. In TRIUMPH-1 (2,339 adults without diabetes), mean weight change at 80 weeks was -25.0% on the highest dose against -3.9% on placebo, counting everyone as randomized [3][8]. Lilly is the funder of all of these trials.
• Lilly’s own releases report dysaesthesia (altered skin sensation) in up to 12.5% of participants on retatrutide in TRIUMPH-1, against 0.9% on placebo [8].
• Research-use-only vials are not the trial product. Regulators in the US, UK and Australia have said products sold as retatrutide are unapproved, and some tested samples did not contain it [13][14][15].

What retatrutide is

Retatrutide (code LY3437943) is a once-weekly injection that activates three receptors: GIP, GLP-1 and glucagon. It is an investigational drug, and the vials sold online as “research use only” are not the product used in these trials. We compare retatrutide as a research peptide on its compound page. This article covers only what trials, regulators and Lilly have published. For Lilly’s business context see the Lilly GLP-1 overview.

Phase 2 results (2023)

Obesity, NEJM. A double-blind, placebo-controlled trial (NCT04881760) randomized 338 adults with obesity, or overweight plus a weight-related condition, for 48 weeks. Mean weight change at 24 weeks (the primary endpoint) and 48 weeks was [1]:

Arm (weekly)	24 weeks	48 weeks
1 mg	-7.2%	-8.7%
4 mg (combined)	-12.9%	-17.1%
8 mg (combined)	-17.3%	-22.8%
12 mg	-17.5%	-24.2%
Placebo	-1.6%	-2.1%

The abstract says gastrointestinal events were the most common, dose-related and mostly mild to moderate, and that starting at a lower dose reduced them. Heart rate rose with dose, peaked at 24 weeks and declined afterwards [1]. The abstract does not report dysaesthesia or discontinuation rates. Funder: Eli Lilly [1].

Type 2 diabetes, Lancet. A placebo- and dulaglutide-controlled trial (NCT04867785) at 42 US sites randomized 281 adults for 36 weeks, with HbA1c at 24 weeks as the primary endpoint [2]. HbA1c fell by 0.43% on 0.5 mg and by between 1.30% and 2.02% on the 4 mg to 12 mg arms, against 0.01% on placebo and 1.41% on dulaglutide 1.5 mg. Weight change at 36 weeks reached about -17% on the two highest-dose arms, against -3.0% on placebo [2]. Gastrointestinal events affected 35% of retatrutide participants (13% on placebo); no severe hypoglycaemia or deaths were reported [2]. Funder: Eli Lilly.

The Phase 3 programme

ClinicalTrials.gov lists 14 Phase 3 records naming retatrutide, read on 2026-11-08 [6]. None had posted results on the registry; the two Phase 2 trials above had [6]. TRIUMPH covers obesity and its complications; TRANSCEND covers type 2 diabetes. TRIUMPH-Outcomes (NCT06383390) plans 10,000 participants for cardiovascular and kidney outcomes, with primary completion listed as February 2029 [6].

Lilly announced these topline results:

Date	Trial	Reported by Lilly
11 Dec 2025	TRIUMPH-4, knee osteoarthritis (445 adults, 68 weeks)	9 mg and 12 mg: -20.0% and -23.7% (all randomized) or -26.4% and -28.7% (adherent); placebo -4.6% or -2.1% [7]
21 May 2026	TRIUMPH-1 (2,339 adults, 80 weeks)	-17.6%, -23.7%, -25.0% on 4, 9, 12 mg; placebo -3.9% [8]
23 Jul 2026	TRIUMPH-2 (1,152, type 2 diabetes) and TRIUMPH-3 (1,949, obesity with cardiovascular disease)	TRIUMPH-2 (adherent): -12.7%, -19.1%, -20.8%; placebo -4.0%. TRIUMPH-3: -21.6% and -22.6% on 9 and 12 mg; placebo -3.2% [9]

Lilly gives two estimates. The “efficacy estimand” counts people who stayed on the drug; the “treatment-regimen estimand” counts everyone as randomized [7]. The lower number is the better guide to a whole trial population. For TRIUMPH-1 the adherent figures were -19.0%, -25.9% and -28.3% against -2.2% on placebo [8]. In a 104-week extension for 532 participants with BMI of 35 or higher, Lilly reported -30.3% on the highest-dose group (adherent), although dose levels in that extension were changed to the maximum tolerated dose [8]. TRIUMPH-3 reported 44 five-component cardiovascular events on retatrutide against 52 on placebo (hazard ratio 0.82, interval 0.55 to 1.22); Lilly said events were fewer than expected in both arms [9]. The trial was not powered to answer that question.

Peer-reviewed papers. TRIUMPH-1 appeared in NEJM (published online 29 September 2026), TRIUMPH-2 in The Lancet (29 September 2026), and the two sleep apnoea trials, TRIUMPH-1-OSA (243 adults) and TRIUMPH-2-OSA (448), in NEJM on 21 October 2026 [3][4][5]. All are Lilly-funded [3][4][5]. We read the abstracts through Europe PMC, not the full texts. The NEJM TRIUMPH-1 abstract matches Lilly’s treatment-regimen figures; it also reports knee pain and apnoea-hypopnoea index changes in subgroups of 574 and 243 participants [3]. The TRIUMPH-2 abstract reports -11.9%, -16.8% and -18.8% against -5.1% on placebo [4]. This differs from Lilly’s -20.8% because the estimand differs; the abstract did not say which estimand the paper used, and we could not confirm it.

TRANSCEND. TRANSCEND-T2D-1 (537 adults, placebo-controlled) is complete in the registry [6]. A search result gave 19 March 2026 as Lilly’s topline date, but we could not open that release and give no numbers. Lilly’s Q3 2026 release says a Phase 3 trial against Ozempic 2 mg in type 2 diabetes had positive topline results, with greater A1C reduction and more than double the weight loss, and gives no figures in the part we read [11]. The registry trial that fits is TRANSCEND-T2D-2 (NCT06260722, 1,250 participants, primary completion August 2026), but the release does not name it [6][11].

Safety signals in the public data

• Dysaesthesia. TRIUMPH-1: 5.1%, 12.3% and 12.5% on the three doses against 0.9% on placebo. TRIUMPH-4: 8.8% on 9 mg and 20.9% on 12 mg against 0.7%. Lilly describes the events as mostly mild to moderate [7][8].
• Stopping because of adverse events. TRIUMPH-1: 4.1%, 6.9%, 11.3% against 4.9% on placebo. TRIUMPH-4: 12.2% and 18.2% against 4.0%; Lilly attributes part of this to participants judging their weight loss excessive [7][8].
• Heart rate. Raised heart rate was reported in Phase 2 [1]. None of the Phase 3 releases or abstracts we read reports heart rate, so the Phase 3 picture is unknown to us.
• Gastrointestinal events (nausea, diarrhoea, constipation, vomiting) were the most common in every report [1][3][4][7].

Regulatory status

• United States, 8 November 2026: not approved. Lilly said on 23 July 2026 that it plans to submit “in Q1 2027” and is completing the chemistry and manufacturing package [9]. We found no announced submission to any regulator. We did not check the EMA, BfArM or any other agency’s register.
• Expanded access: a single-patient programme (NCT07629401, first posted 5 June 2026) supplies it to adults with a BMI of 35 or higher and at least two serious obesity complications who cannot join a trial [12]. It is not an approval.
• Prescription or scheduling status: none, because there is no authorisation.
• “Research use only” is a seller’s label. It does not make a product legal for human use. In FDA warning letters dated 10 December 2024 and 24 August 2026 the agency listed retatrutide sold under that label as an unapproved new drug and said website content showed the products were intended for human use [13][14].
• United Kingdom: the MHRA said on 24 July 2026 that retatrutide is not approved for UK use, that sellers are acting illegally, and that there is no guarantee products sold as retatrutide contain it [15].
• Australia: the Victorian health department’s alert of 19 June 2026 reported six cases of acute liver injury since January 2026 in people who used products labelled retatrutide, with a contaminant suspected [16]. We could not open the TGA’s own page; a search summary attributed to the TGA a finding that one sold sample contained semaglutide and no retatrutide, which we do not treat as verified.

Risks and unknowns

Documented effects are those above: gastrointestinal events, dysaesthesia, dose-related discontinuations and, in Phase 2, a heart-rate rise. Phase 3 trials ran 68 to 80 weeks, and 104 weeks in one extension. Long-term safety, cardiovascular outcomes (TRIUMPH-Outcomes is ongoing), effects in people under 18 and in pregnancy, and interactions are not established in the sources we read. We did not read full texts or the trial protocols. Rates of dysaesthesia in Phase 2 are unknown to us. Products sold as retatrutide outside trials have no identity or purity guarantee, and a regional health department has linked them to liver injury [16]. We have no evidence on any such product’s effect.

Frequently asked questions

Are retatrutide Phase 3 results public? Yes. Lilly has announced topline results for TRIUMPH-4, TRIUMPH-1, TRIUMPH-2 and TRIUMPH-3 between December 2025 and July 2026, and three peer-reviewed papers appeared in September and October 2026 [3][4][5][7][8][9].

How much weight did people lose? In TRIUMPH-1, counting everyone as randomized, mean weight change at 80 weeks was -17.6%, -23.7% and -25.0% across three dose arms, against -3.9% on placebo [8]. People with type 2 diabetes lost less on average [4][9].

Is retatrutide approved? Not anywhere we could verify. Lilly plans a US submission in the first quarter of 2027 [9].

Is the “research use only” product the same as the trial drug? No. The trials were sponsored by Lilly. Regulators in the US, UK and Australia call retatrutide sold outside trials unapproved, and some testing found other contents [13][14][15][16].

Sources

1. Jastreboff AM et al., “Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial,” N Engl J Med (2023), PMID 37366315, abstract read through Europe PMC. https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:37366315&resultType=core&format=json&src=med
2. Rosenstock J et al., retatrutide in type 2 diabetes, Phase 2, Lancet (2023), PMID 37385280, abstract read through Europe PMC. https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:37385280&resultType=core&format=json&src=med
3. “Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity” (TRIUMPH-1), N Engl J Med 395(18) (online 2026-09-29), PMID 42814954, abstract through Europe PMC. https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:42814954&resultType=core&format=json&src=med
4. “Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2),” The Lancet 408 (online 2026-09-29), PMID 42810372, abstract through Europe PMC. https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:42810372&resultType=core&format=json&src=med
5. “Retatrutide Once Weekly for Treatment of Obstructive Sleep Apnea,” N Engl J Med (online 2026-10-21), PMID 42904878, abstract through Europe PMC. https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:42904878&resultType=core&format=json&src=med
6. ClinicalTrials.gov, query for intervention “retatrutide” via API v2 (read 2026-11-08). https://clinicaltrials.gov/api/v2/studies?query.intr=retatrutide
7. Eli Lilly and Company, TRIUMPH-4 topline release (2025-12-11), via PR Newswire. https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-delivered-weight-loss-of-up-to-an-average-of-71-2-lbs-along-with-substantial-relief-from-osteoarthritis-pain-in-first-successful-phase-3-trial-302638804.html
8. Eli Lilly and Company, TRIUMPH-1 topline release (2026-05-21), via PR Newswire. https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss-in-pivotal-phase-3-obesity-trial-302778859.html
9. Eli Lilly and Company, TRIUMPH-2 and TRIUMPH-3 topline release (2026-07-23), via PR Newswire. https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-successful-in-two-additional-phase-3-obesity-trials-delivering-significant-improvements-in-weight-and-a1c-302832674.html
10. Eli Lilly and Company, TRIUMPH-2 detailed results release (2026-09-29), via PR Newswire. https://www.prnewswire.com/news-releases/lillys-triple-agonist-retatrutide-delivered-substantial-weight-loss-and-a1c-reduction-underscoring-its-potential-promise-for-people-with-obesity-and-type-2-diabetes-302891798.html
11. Eli Lilly and Company, third-quarter 2026 results, Exhibit 99.1 to Form 8-K (2026-10-29). https://www.sec.gov/Archives/edgar/data/59478/000005947826000104/q326lillysalesandearningsp.htm
12. ClinicalTrials.gov, NCT07629401, “Pre-approval Expanded Access of Retatrutide (LY3437943)” (first posted 2026-06-05). https://clinicaltrials.gov/api/v2/studies/NCT07629401
13. U.S. FDA, warning letter to Xcel Research LLC (2024-12-10). https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/xcel-research-llc-694608-12102024
14. U.S. FDA, warning letter to Peak Performance Peptides (2026-08-24). https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/peak-performance-peptides-735127-08242026
15. MHRA, “No summer shortcut for safe weight loss,” GOV.UK (2026-07-24). https://www.gov.uk/government/news/no-summer-shortcut-for-safe-weight-loss
16. Victorian Department of Health, “Toxicity linked to unapproved peptide product labelled Retatrutide” (2026-06-19). https://www.health.vic.gov.au/health-alerts/toxicity-linked-to-unapproved-peptide-product-labelled-retatrutide

Note on reading: the abstracts and registry data were read through summarising tools; Lilly’s investor site blocked us, so Lilly releases were read as PR Newswire copies. Source 10 supports the TRIUMPH-2 figures also given in [9].

This article is information, not medical advice.