Eli Lilly confirmed on 15 September 2026 that the full Phase 3 results for retatrutide in people with type 2 diabetes will be presented at the European Association for the Study of Diabetes (EASD) annual meeting in Milan, at a dedicated retatrutide symposium on Wednesday 30 September. That matters because the TRIUMPH-2 numbers released in July looked very different to the headline figures everyone has been quoting — and the retatrutide vs tirzepatide comparison in a diabetes population is where this drug's competitive case actually gets tested.

The short version: retatrutide's best average weight loss in adults with type 2 diabetes was 20.8% at 80 weeks. In the non-diabetes obesity trial, TRIUMPH-1, the same 12 mg dose averaged 28.3%. Same molecule, same dose, same trial length — roughly seven and a half percentage points of difference, driven by the population.

Why the diabetes number is lower — and why that's not a disappointment

TRIUMPH-2 randomised 1,152 adults with type 2 diabetes and obesity or overweight to retatrutide 4 mg, 9 mg, 12 mg or placebo over 80 weeks. Average weight loss came in at 12.7% (4 mg), 19.1% (9 mg) and 20.8% (12 mg), alongside A1C reductions of up to 1.6 percentage points from a baseline of 7.7%.

Compare that to TRIUMPH-1, which enrolled 2,339 adults with obesity or overweight and at least one weight-related complication but without diabetes. There, the dose curve ran 19.0%, 25.9% and 28.3%, against 2.2% on placebo.

A blunted weight-loss response in people with type 2 diabetes is a well-documented pattern across this drug class rather than anything specific to the triple agonist — so the more useful question is not "why is it lower?" but "lower compared to what else is available?" More on the TRIUMPH programme and how the trials differ.

Retatrutide vs tirzepatide: the honest cross-trial read

The existing benchmark in this exact population is tirzepatide's SURMOUNT-2 trial, which enrolled 938 adults with overweight or obesity plus type 2 diabetes. At 72 weeks, the 15 mg dose produced 15.7% average weight loss and the 10 mg dose 13.4%, versus 3.3% on placebo.

So retatrutide's 20.8% in TRIUMPH-2 sits above tirzepatide's 15.7% in SURMOUNT-2 — but read that gap carefully:

  • These are separate trials, not a head-to-head. No randomised comparison of retatrutide against tirzepatide in a diabetes population has been reported.
  • Different durations. TRIUMPH-2 ran 80 weeks; SURMOUNT-2 ran 72. Weight loss on these agents is still accruing late in the curve, so the longer trial has an advantage before you account for anything else.
  • Different baseline populations, different eras of background care. SURMOUNT-2 reported in 2023; TRIUMPH-2 in 2026.

Cross-trial arithmetic is the weakest form of comparison in clinical medicine. It's suggestive, not conclusive. If you want the mechanistic reason retatrutide might do more — the glucagon arm added on top of GLP-1 and GIP — see what is retatrutide.

The rest of the 2026 TRIUMPH picture

The July announcement covered two trials, and the second one is arguably the more interesting of the pair. TRIUMPH-3 enrolled more than 1,900 people with class II or III obesity (BMI 35+) and established cardiovascular disease, with or without type 2 diabetes. Average weight loss reached up to 22.6% at 80 weeks versus about 3% on placebo, with the 12 mg dose also delivering a 37.0% drop in triglycerides, 16.5% in non-HDL cholesterol, 9.3 mmHg in systolic blood pressure and 51.2% in high-sensitivity C-reactive protein.

One caveat Lilly itself flagged: major adverse cardiovascular events occurred less frequently than anticipated in both the retatrutide and placebo arms. TRIUMPH-3 was not powered as a cardiovascular outcomes trial, and a low event count in both groups limits what can be concluded about hard cardiovascular endpoints.

Safety: the same dose-related pattern

In TRIUMPH-2, gastrointestinal adverse events predominated, and discontinuations due to adverse events ran from 3.8% to 11.6% across the retatrutide doses versus 4.9% on placebo — the same dose-dependent tolerability gradient reported in TRIUMPH-1. Full tolerability detail is on the safety page.

Where this sits, and what it isn't yet

Everything above comes from company press releases and conference materials, not peer-reviewed publications. TRIUMPH-2's full dataset has its first proper airing at EASD on 30 September, where the detail that press releases skip — subgroup responses, A1C target attainment, body composition, the shape of the tolerability curve — should finally be visible. Lilly is also presenting ACHIEVE-4 data for its approved oral GLP-1 Foundayo (orforglipron) and first Phase 2 results for eloraTZP at the same meeting.

Retatrutide remains investigational everywhere in the world. Lilly has said it plans to submit a Biologics License Application to the US FDA in the first quarter of 2027. For Australian readers, that ordering matters: retatrutide is not TGA-approved, no Australian submission has been announced, and the TGA generally acts on a sponsor's application after major-market filings rather than before them. See retatrutide in Australia for the local regulatory position.

Join the free updates list and we'll send you what the EASD presentation actually shows on 30 September — including whatever the press release left out.

FAQ

Does retatrutide work as well in people with type 2 diabetes?

It works, but less powerfully. In TRIUMPH-2, adults with type 2 diabetes and obesity or overweight lost up to 20.8% of body weight at 80 weeks on 12 mg, compared with 28.3% at the same dose and duration in TRIUMPH-1, which excluded people with diabetes.

Is retatrutide better than tirzepatide for weight loss in diabetes?

Cross-trial numbers favour retatrutide — 20.8% in TRIUMPH-2 at 80 weeks versus 15.7% for tirzepatide 15 mg in SURMOUNT-2 at 72 weeks — but these were separate trials of different lengths and populations, and no head-to-head study has been reported.

When is the TRIUMPH-2 data being presented?

At an EASD-sponsored retatrutide symposium in Milan on Wednesday 30 September 2026, 8:30–9:30 a.m. CEST, during the EASD annual meeting running 28 September to 2 October.

Has retatrutide been approved anywhere?

No. Retatrutide is investigational and has no marketing authorisation in any country. Lilly has said it plans to file a Biologics License Application with the US FDA in the first quarter of 2027; it is not TGA-approved in Australia.

Sources

Disclaimer: This article is general information, not medical advice. Retatrutide is an investigational medicine and is not approved by the TGA or any other regulator. Nothing here should be used to make treatment decisions — speak with a qualified Australian health professional about your own situation. retatrutide.net.au is an independent information site and is not affiliated with, endorsed by or sponsored by Eli Lilly and Company.