If you have only seen one number attached to retatrutide, it is almost certainly 28.3% — the average body weight reduction at 12mg over 80 weeks in the phase 3 TRIUMPH-1 trial, where 45.3% of participants lost 30% or more of their starting weight. But the retatrutide results picture got considerably more nuanced over the past few weeks. Eli Lilly's July 2026 topline release of TRIUMPH-2 and TRIUMPH-3 showed that the headline figure moves — sometimes by seven or eight percentage points — depending on who is being treated. That is the most useful piece of new information in the retatrutide world right now, and it is the number most people will actually be quoted by a clinician if and when this drug reaches market.

What's actually new: TRIUMPH-2 and TRIUMPH-3

On 23 July 2026, Lilly reported topline results from two further phase 3 obesity trials. In TRIUMPH-2, which enrolled adults living with both obesity and type 2 diabetes, once-weekly retatrutide produced body weight reductions of up to 20.8%, alongside HbA1c reductions reported at up to roughly 1.6 percentage points. In TRIUMPH-3, in adults with obesity and established cardiovascular disease, weight reduction reached up to 22.6%.

Two important caveats up front. Both are topline company announcements, not peer-reviewed publications — the full datasets, subgroup breakdowns and safety tables will only be properly assessable when they are presented at a scientific meeting and published in a journal. And topline releases describe results at the highest dose in completers-style analyses, which usually flatter the number relative to what a real-world clinic sees.

With these two readouts, Lilly has now reported positive results from five late-stage retatrutide trials, and has said it intends to file with the US FDA from 2027.

Why the same drug gives different retatrutide results

The gap between ~28% (TRIUMPH-1, obesity without diabetes) and ~21% (TRIUMPH-2, obesity with type 2 diabetes) is not a fluke or a manufacturing difference. It is a pattern that has been seen with every incretin drug on the market.

Type 2 diabetes blunts weight loss

Semaglutide and tirzepatide both deliver noticeably less weight loss in people with type 2 diabetes than in people without it. The likely reasons are a mix of altered energy metabolism, the effect of other glucose-lowering medicines (some of which are weight-neutral or weight-gaining), a lower baseline capacity to lose fat as glycaemic control improves, and reduced incretin responsiveness. A drop from ~28% to ~21% is entirely in keeping with that history — and 20.8% is still a very large number by the standards of diabetes medicine, where 10–15% was considered exceptional two years ago.

Cardiovascular disease populations are older and sicker

TRIUMPH-3's ~22.6% sits between the two. Adults with established cardiovascular disease tend to be older, on more concurrent medications, and often have less physiological headroom for aggressive dose escalation. Trial protocols in these groups are also typically more conservative about pushing to the top dose.

The practical read: retatrutide's relative advantage over existing options appears to hold across populations, but the absolute number you should expect depends on your metabolic starting point. More on how the trials are structured is in our clinical trials overview.

The regulatory picture shifted too

Alongside the data, two regulatory developments are worth knowing about. First, Lilly confirmed in early August 2026 that a defined group of patients can apply for early access to retatrutide ahead of FDA approval, a pathway built after sustained pressure from physicians. Second — and more consequential for timelines — reporting in early August indicated the FDA has taken the view that retatrutide is neither a protein nor a biological product, which would push it down the new drug application route rather than the biologics licence application route Lilly had signalled. The classification matters for review mechanics and for how competitors can eventually enter.

Neither of these changes anything for Australia today. Retatrutide is not TGA-approved and cannot be prescribed here for weight management. An Australian submission would follow US and European filings, and the TGA would then run its own independent evaluation. There is a real Australian implication in the TRIUMPH-2 numbers though: a large share of the Australian population that would be considered for this class lives with both obesity and type 2 diabetes, so 20.8% — not 28.3% — is the figure that will be relevant to many of the people who eventually ask about it. See our Australia page for where things stand locally.

Safety: consistent, and consistently gastrointestinal

Across the trials reported so far, the most common adverse events remain diarrhoea, nausea, constipation and decreased appetite — the familiar incretin profile, generally dose-dependent and most pronounced during escalation. Retatrutide's glucagon component also raises questions that need long-term data to settle, including effects on heart rate and hepatic parameters. Our safety page covers what has been reported to date and what remains open.

What to watch next

  • Full publications of TRIUMPH-2 and TRIUMPH-3 in a peer-reviewed journal, with complete adverse-event and discontinuation data.
  • The SYNERGY MASLD/MASH programme, where phase 2 liver fat reductions were the most eye-catching of any compound in development, and where a separate liver indication would be a genuinely new use case.
  • The TRANSCEND diabetes readouts, which position retatrutide against tirzepatide on glycaemic control rather than weight alone.
  • Whether Lilly's 2027 filing target holds given the drug-versus-biologic classification question.

Want each of these as it lands, in plain English, without the hype? Join the free updates list — we email when something material actually changes. New to the molecule? Start with what is retatrutide.

FAQ

What were the TRIUMPH-2 and TRIUMPH-3 retatrutide results?

Lilly's July 2026 topline release reported up to 20.8% average body weight reduction in adults with obesity and type 2 diabetes (TRIUMPH-2) and up to 22.6% in adults with obesity and established cardiovascular disease (TRIUMPH-3). Both are company topline announcements and have not yet been published in full peer-reviewed form.

Why is retatrutide weight loss lower in people with type 2 diabetes?

This pattern applies to every drug in the incretin class, including semaglutide and tirzepatide. Contributing factors include concurrent glucose-lowering medications, altered energy metabolism and reduced incretin responsiveness — it is not a sign the drug is working poorly.

Has retatrutide been approved anywhere yet?

No. Retatrutide remains investigational in every jurisdiction, including Australia, where it is not TGA-approved. Eli Lilly has said it plans to file for approval from 2027, and a limited early-access pathway opened in the US in August 2026 for a defined patient group.

How does retatrutide differ from Ozempic and Mounjaro?

Ozempic and Wegovy are semaglutide, which acts on one receptor (GLP-1). Mounjaro and Zepbound are tirzepatide, which acts on two (GLP-1 and GIP). Retatrutide adds a third — glucagon — which is thought to increase energy expenditure on top of the appetite and glycaemic effects.

Sources

Disclaimer: This article is general information only and is not medical advice. Retatrutide is an investigational medicine and is not approved by the TGA or any other regulator for weight management. Always speak with your GP or a qualified health professional about treatment decisions. retatrutide.net.au is an independent Australian information site and is not affiliated with, endorsed by, or sponsored by Eli Lilly and Company.