Retatrutide

How far human research has progressed: Pivotal Phase 3 results reported (2026); investigational, not approved

Clinical trials use once-weekly subcutaneous injection. Material sold online as 'retatrutide' is unapproved, unstudied in humans as sold, and outside any regulated supply chain.

Route availability is not evidence of efficacy, and evidence from one route does not transfer to another. The Registry never provides dosing or sourcing information.

A single peptide engineered to hit three metabolic receptors, adding glucagon-receptor agonism (which raises energy expenditure) to the incretin pair.

• The largest weight loss yet seen in an incretin-class trial programme
• Improvements in liver fat
• Better body composition outcomes

Pivotal Phase 3 efficacy is now supported by detailed TRIUMPH-2 results presented at EASD 2026: in 1,152 adults with obesity or overweight and type 2 diabetes, mean weight change at 80 weeks was -12.7%, -19.1% and -20.8% with 4 mg, 9 mg and 12 mg retatrutide versus -4.0% with placebo under the efficacy estimand. Glycaemic and cardiometabolic markers also improved. Retatrutide remains investigational and unapproved; long-term safety, cardiovascular and renal outcomes, regulatory review and real-world effectiveness remain unresolved.

• TRIUMPH-2 Phase 3 (detailed results reported by Lilly and presented at EASD, 29 September 2026): 1,152 adults with obesity or overweight and type 2 diabetes were randomised 1:1:1:1 to retatrutide 4 mg, 9 mg, 12 mg or placebo for 80 weeks. Under the efficacy estimand, mean weight change was -12.7%, -19.1% and -20.8% versus -4.0% with placebo; HbA1c fell by 1.4, 1.6 and 1.5 percentage points versus 0.2 with placebo. At 12 mg, 67.0% achieved at least 15% weight loss, 52.0% at least 20%, and 34.9% at least 25%. These are trial-population averages, not individual forecasts.
• TRIUMPH-1 Phase 3 topline (sponsor-reported, 21 May 2026): average body-weight reduction of 28.3% over 80 weeks in the 12 mg group, with 45.3% of participants losing at least 30% of body weight.
• TRIUMPH-1 extension in participants with baseline BMI of 35 or above: average reduction of 30.3% at 104 weeks.
• TRANSCEND-T2D-1 (sponsor-reported, 6 June 2026): HbA1c reductions of up to 2.0 percentage points and weight loss of up to 16.8% at 40 weeks in type 2 diabetes.
• Further TRIUMPH findings reported in knee osteoarthritis and obstructive sleep apnoea populations.
• Earlier randomised Phase 2 trials reporting substantial dose-dependent weight reduction.

• Rodent models of triple agonism showing increased energy expenditure alongside reduced intake.

Animal and cell findings are Level 1–2 evidence.

• Incretin agonism reduces appetite and improves glycaemic handling.
• Glucagon receptor agonism increases energy expenditure and hepatic fat mobilisation — the piece that distinguishes it from dual agonists.

Regulatory decisions apply to specific jurisdictions, products, formulations and indications. An approval elsewhere is not automatically an approval in your country.

Check the regulatory note and linked primary sources for jurisdiction-specific details.

Not approved in any region. Pivotal Phase 3 results from the TRIUMPH programme were reported in 2026, but positive trial results are not an approval: no regulator has yet licensed it and long-term safety data are still accumulating. Anything sold to the public as 'retatrutide' today is outside approved medical supply. On 24 August 2026 the FDA issued warning letters to US vendors — Royal Peptides LLC, Peptide Partners LLC and TXP Innovations LLC (Tex Peptides) — identifying products marketed as retatrutide as unapproved new drugs, and noting that injectable products sold this way are especially concerning because injection bypasses key body defences. This is regulatory and supply-chain evidence, not evidence that pharmaceutical-grade retatrutide has developed a new toxicity signal. FDA also states explicitly that retatrutide cannot be used in compounding under US federal law, because it is not an FDA-approved drug and is not on a bulk drug substances list permitted for compounding. Again, that is a legal and compounding-status point, not a finding about efficacy or intrinsic toxicity.

• Baseline · Global

  Investigational only; advanced Phase 3 programme in obesity and metabolic disease.

• Independent peer-reviewed appraisal and additional full pivotal Phase 3 datasets, including longer-term safety and outcome data.
• A regulatory approval decision in a major region.

• Sponsor / officialLilly — detailed TRIUMPH-2 Phase 3 results presented at EASD (29 September 2026)
• Sponsor / officialLilly — new data on Foundayo (orforglipron), retatrutide and Eloratzp to be presented at EASD 2026, including TRIUMPH-2 (15 September 2026)
• Sponsor / officialLilly — TRIUMPH-1 Phase 3 topline: retatrutide delivered powerful weight loss (21 May 2026)
• Sponsor / officialLilly — retatrutide drove substantial improvements across TRIUMPH and TRANSCEND-T2D trials (6 June 2026)
• Trial registryClinicalTrials.gov — TRIUMPH-5: retatrutide in obesity with cardiovascular disease (NCT06662383)NCT: NCT06662383
• Trial registryClinicalTrials.gov — TRIUMPH-Outcomes: cardiovascular outcomes trial of retatrutide (NCT06383390)NCT: NCT06383390
• Regulatory / labelFDA warning letter — Royal Peptides LLC (24 August 2026)
• Regulatory / labelFDA warning letter — Peptide Partners LLC (24 August 2026)
• Regulatory / labelFDA warning letter — TXP Innovations LLC dba Tex Peptides (24 August 2026)
• Regulatory / labelFDA — FDA's concerns with unapproved GLP-1 drugs used for weight loss

Source hierarchy: regulatory documents and trial registries first, peer-reviewed work next, sponsor material flagged as non-independent. We never use supplier or clinic marketing as evidence, and where a verified source has not yet been curated we say so rather than inventing one.

These entries record changes to our assessment of the published evidence — not changes to the compound itself.

1. 2026-09-18

   Lilly reported that adults with obesity or overweight and type 2 diabetes lost up to a mean 49.6 lb (22.5 kg, 20.8%) and had HbA1c reductions of up to 1.6 percentage points at 80 weeks in TRIUMPH-2.

   Change 1 of 4

   L4Good human trials

   These are company-reported Phase 3 topline results announced on 15 September 2026, pending fuller scientific presentation and publication. Retatrutide remains investigational and unapproved, and another sponsor topline does not move its Level 4 rating. Reviewed 18 September 2026.

2. 2026-09-06

   Pivotal Phase 3 results now available: TRIUMPH-1 topline (21 May 2026) reported 28.3% average weight loss over 80 weeks in the 12 mg group, with 45.3% of participants losing at least 30% of body weight, and 30.3% average loss at 104 weeks in the higher-BMI extension.

   Change 2 of 4

   L4Good human trials

   Our human-efficacy score rose because the pivotal trial has now reported, but the evidence level and regulatory status did not move. These are sponsor topline announcements rather than peer-reviewed publications, and retatrutide is still not approved anywhere. Strong efficacy evidence and complete long-term safety evidence are different things.

3. 2026-09-06

   Lilly's 6 June 2026 update reported TRANSCEND-T2D-1 HbA1c reductions of up to 2.0 percentage points and weight loss of up to 16.8% at 40 weeks, plus further TRIUMPH findings in knee osteoarthritis and obstructive sleep apnoea.

   Change 3 of 4

   L4Good human trials

   Added as sponsor-reported trial results across additional populations. Breadth of reported benefit is not the same as regulatory acceptance, and none of these indications is approved.

4. 2026-07-02

   Baseline entry: efficacy confidence for weight loss set high; safety confidence held low pending Phase 3 completion.

   Change 4 of 4

   L4Good human trialsEvidence rating changedBaseline entry

   Randomised human trial data support large weight reduction. Long-term safety and a regulatory decision are still outstanding, so the two axes are rated separately.