On this page

Evidence status — updated and source-checked 6 October 2026: Retatrutide (LY3437943) is an investigational single-molecule agonist of the GIP, GLP-1 and glucagon receptors. Phase 2 and TRIUMPH-1 Phase 3 results are now published in the New England Journal of Medicine. Lilly also states that TRIUMPH-2 results in adults with type 2 diabetes and obesity or overweight were published in The Lancet on 29 September 2026. Retatrutide remains unapproved by the TGA, FDA and every other regulator.

This living tracker separates peer-reviewed publications, sponsor announcements, trial registrations and regulatory decisions. It does not provide dosing, sourcing or treatment advice.

What changed: The 29 September 2026 TRIUMPH-1 publication replaces the earlier topline-only evidence status. Its treatment-regimen analysis reported mean weight changes of −17.6%, −23.7% and −25.0% for the 4 mg, 9 mg and 12 mg groups, versus −3.9% with placebo at 80 weeks.

At a glance

Question Current answer
What is it? A triple hormone-receptor agonist targeting GIP, GLP-1 and glucagon receptors.
Who is developing it? Eli Lilly and Company.
Highest evidence stage Phase 3, with TRIUMPH-1 peer reviewed and additional Phase 3 studies reported or published.
Peer-reviewed obesity evidence Phase 2 and Phase 3 TRIUMPH-1 randomised trials published in the New England Journal of Medicine.
Australian approval No TGA approval as checked 6 October 2026.
Commercial online products Not equivalent to clinical-trial material; the TGA warns products outside trials may be counterfeit.

Evidence ledger: what each source actually establishes

Source check: 6 October 2026. Evidence type matters: a registry record, company announcement, peer-reviewed paper and regulator decision answer different questions.

Record What it establishes Limit to keep in view
Phase 2 obesity trial (2023) At 48 weeks, the efficacy-estimand mean change in the 12 mg group was −24.2% versus −2.1% with placebo. A controlled Phase 2 result, not a personal forecast or evidence about online products.
TRIUMPH-1 Phase 3 paper (29 September 2026) In the treatment-regimen analysis, mean weight change at 80 weeks was −17.6%, −23.7% and −25.0% across the 4 mg, 9 mg and 12 mg groups, versus −3.9% with placebo. The trial enrolled adults with obesity without diabetes. Results cannot be transferred automatically to people with diabetes or to unverified products.
TRIUMPH-1 registry Documents design, eligibility, outcomes and record changes for NCT05929066. A registry explains what was planned; the publication explains what was analysed and reported.
Lilly programme update (September 2026) Lists disclosed Phase 3 studies and states that TRIUMPH-2 results were published in The Lancet. Sponsor summaries require verification against the complete publication and regulator review.
Victorian health alert (19 June 2026) Reports six acute liver-injury cases associated with unapproved products labelled retatrutide; contamination was suspected and investigation continued. These cases concern unapproved labelled products, not verified Lilly clinical-trial material.
TGA alert (14 September 2026) A tested product labelled retatrutide contained undeclared semaglutide and no retatrutide. One sample cannot characterise every product, but proves that an online label is not evidence of identity.

Update trigger: this page changes when a full trial report, registry result or regulator decision changes the evidence state. Planned completion dates and launch speculation are not treated as results or approval.

Phase 2: the 24.2% result in context

The 2023 Phase 2 obesity trial randomised adults with obesity, or overweight plus a weight-related condition, to retatrutide regimens or placebo. At 48 weeks, the reported mean weight change in the 12 mg group was 24.2%, compared with 2.1% for placebo. The result attracted attention because it exceeded the mean changes reported in earlier incretin-therapy trials.

That number should not be read as a guaranteed individual outcome. It is a group mean from a controlled study with eligibility criteria, protocol-defined escalation, monitoring and investigational material. Trial duration, discontinuations, missing-data assumptions and the selected analysis all affect interpretation.

Phase 3 TRIUMPH-1: the peer-reviewed result

TRIUMPH-1 (NCT05929066) was a Phase 3 randomised, double-blind, placebo-controlled trial involving 2,339 adults with obesity without diabetes. Participants received retatrutide 4 mg, 9 mg or 12 mg, or placebo, for 80 weeks.

The peer-reviewed paper, published online in the New England Journal of Medicine on 29 September 2026, reported the following treatment-regimen results. This analysis estimates outcomes regardless of treatment discontinuation or use of prohibited weight-management interventions and is therefore different from the earlier sponsor-reported efficacy estimand.

Trial group Mean body-weight change at 80 weeks Evidence status
Retatrutide 4 mg −17.6% Peer-reviewed treatment-regimen result
Retatrutide 9 mg −23.7% Peer-reviewed treatment-regimen result
Retatrutide 12 mg −25.0% Peer-reviewed treatment-regimen result
Placebo −3.9% Peer-reviewed treatment-regimen result

Why earlier articles reported 28.3%

Lilly’s May topline announcement used an efficacy estimand: the estimated effect had participants remained on assigned treatment without prohibited weight-management treatment. That analysis reported −28.3% for the 12 mg group versus −2.2% for placebo. The later peer-reviewed treatment-regimen result was −25.0% versus −3.9%. Both numbers can be accurate while answering different analytical questions.

Our weight-loss trial guide explains estimands, missing data, discontinuations and why percentages from different trials should not be ranked without matching their methods.

Other outcomes in the TRIUMPH-1 programme

The paper also analysed prespecified subgroups with knee osteoarthritis and obstructive sleep apnoea. It reported greater reductions in WOMAC pain scores and apnoea–hypopnoea events in relevant retatrutide groups than with placebo. These subgroup outcomes do not turn the investigational molecule into an approved treatment; indication-specific regulator assessment remains necessary.

Adverse events reported in TRIUMPH-1

In the sponsor’s TRIUMPH-1 release, the most common adverse events were gastrointestinal and increased with dose in several categories. For the 4 mg, 9 mg and 12 mg groups respectively, reported nausea rates were 28.6%, 38.4% and 42.4%, compared with 14.8% for placebo. Vomiting was reported in 10.6%, 22.8% and 25.3%, compared with 4.8% for placebo.

Discontinuation because of adverse events was reported in 4.1%, 6.9% and 11.3% across the three active groups, versus 4.9% with placebo. These headline rates do not capture every risk question; longer follow-up and complete regulatory review remain important.

Phase 3 programme: studies answer different questions

Lilly’s September 2026 programme update lists disclosed data from TRIUMPH-1, TRIUMPH-2, TRIUMPH-3, TRIUMPH-4 and TRANSCEND-T2D-1. The populations differ: obesity without diabetes, obesity with type 2 diabetes, severe obesity with cardiovascular disease, knee osteoarthritis and diabetes with inadequate glycaemic control are not interchangeable.

Study Population or question Current evidence label
TRIUMPH-1 Obesity without diabetes; includes knee-osteoarthritis and sleep-apnoea substudies Peer-reviewed Phase 3 publication
TRIUMPH-2 Obesity or overweight with type 2 diabetes Lilly reports detailed results published in The Lancet; publication should be read before cross-trial comparison
TRIUMPH-3 Severe obesity with established cardiovascular disease, with or without diabetes Phase 3 results disclosed by sponsor
TRIUMPH-4 Obesity or overweight with knee osteoarthritis pain, without diabetes Phase 3 results disclosed
TRANSCEND-T2D-1 Type 2 diabetes inadequately controlled with diet and exercise Lilly reports full Phase 3 results published in The Lancet

Which retatrutide page do you need?

Australia: urgent regulatory context

On 14 September 2026, the TGA reported testing a product sold as retatrutide after a serious adverse-event report. The tested sample contained undeclared semaglutide, no retatrutide, and approximately eight times the semaglutide level found in TGA-assessed semaglutide products. The TGA says retatrutide has not been approved and products accessed outside clinical trials could be counterfeit.

A separate Victorian Chief Health Officer alert dated 19 June 2026 reported six acute liver-injury cases associated with unapproved products labelled retatrutide. The department said contamination was suspected and the investigation was continuing. These alerts concern unapproved labelled products; they must not be misrepresented as adverse-event findings from verified clinical-trial material.

Read our full TGA retatrutide safety-alert briefing.

What the evidence does not establish

  • It does not establish that a product sold online contains retatrutide.
  • It does not establish safety or effectiveness outside a controlled clinical trial.
  • It does not establish an Australian approval or legal consumer supply pathway.
  • It does not predict an individual’s result.
  • It does not make one receptor component solely responsible for the observed clinical effect.

Frequently asked questions

Is retatrutide approved in Australia?

No. As checked 6 October 2026, retatrutide remains investigational and is not approved by the TGA.

Were the TRIUMPH-1 results peer reviewed?

Yes. The Phase 3 paper was published online in the New England Journal of Medicine on 29 September 2026.

Why do TRIUMPH-1 weight-loss figures differ between reports?

Different estimands handle treatment discontinuation, adherence and additional interventions differently. The peer-reviewed treatment-regimen result for the 12 mg group was −25.0%; the earlier efficacy-estimand topline was −28.3%.

Does a clinical-trial result prove that an online product contains retatrutide?

No. Trial material has controlled identity and handling. Australian alerts document unapproved products whose contents did not match their labels.

Does publication mean public availability is imminent?

No. Publication is not regulatory approval. Timing depends on the remaining programme, submissions and regulator decisions.

Primary records

Editorial boundary: Retatrutide is investigational. This article is a study and regulatory-status summary, not medical advice or a recommendation to obtain or use any substance.

Citation record

How to cite this article

Retatrutide Trial Tracker: Phase 2 Evidence, Phase 3 Results and Regulatory Status. Elite Peps Australia. Published 2 July 2026; updated 6 October 2026. https://elitepepsaustralia.com/retatrutide-triple-agonist-explained/

Source checks: Consult the primary studies, trial records and regulator documents linked in this article for current evidence and status. Publication and update dates do not by themselves indicate an evidence review.