Retatrutide: Triple Agonist Obesity Drug Landscape and Rivals

Retatrutide is Eli Lilly’s investigational once-weekly injection for obesity, and it is the clearest test yet of whether adding a third hormone target can push weight loss beyond today’s drugs. It is not approved anywhere. As of November 4, 2026, Lilly has reported topline results from six Phase 3 trials and says it plans to submit to the FDA in the first quarter of 2027.

Mechanism at a glance

Retatrutide is a triple receptor agonist: it activates the GIP, GLP-1 and glucagon receptors. It is given as a weekly injection, with doses stepped up over time (the Phase 3 trials used 4 mg, 9 mg and 12 mg). In Lilly’s trials the most common side effects were stomach and bowel symptoms such as nausea, diarrhea, constipation and vomiting. Lilly also reported dysesthesia, a sensory disturbance, in a subset of participants; the company describes it as generally mild.

Why it matters

In TRIUMPH-1 (2,339 adults with overweight or obesity, 80 weeks), Lilly reported average weight loss of 19.0%, 25.9% and 28.3% on the 4 mg, 9 mg and 12 mg doses. In TRIUMPH-3 (adults with severe obesity and established cardiovascular disease, 1,949 participants), the 12 mg dose produced 22.6% average weight loss versus 3.2% on placebo. These are company-reported topline figures from the efficacy analysis, not yet peer-reviewed. Tolerability is the number to read alongside them: discontinuations due to adverse events were 11.3% at 12 mg in TRIUMPH-1 versus 4.9% on placebo, and 13.5% at 12 mg in TRIUMPH-3 versus 4.8%.

Competitive pressure points

• Tirzepatide (Lilly’s own): a Phase 3 head-to-head of retatrutide against tirzepatide in adults with obesity (ClinicalTrials.gov NCT06662383) lists a primary completion date of November 2026. That is a study-record date, not a results date.
• Semaglutide: Lilly reported on October 28, 2026 that retatrutide beat Ozempic 2 mg in type 2 diabetes (TRANSCEND-T2D-2, open-label, 1,298 adults): A1C fell 2.2% versus 1.8%, and weight fell 19.5-20.9% versus 9.4%.
• CagriSema (Novo Nordisk): in REDEFINE 4, an open-label head-to-head with tirzepatide, Novo reported 23% weight loss and that the primary endpoint was not achieved. Trade coverage says Novo filed in the US in December 2025.
• Survodutide (Boehringer Ingelheim): a glucagon/GLP-1 dual agonist. In SYNCHRONIZE-1 (725 adults, 76 weeks), weight loss reached up to 16.6% versus 3.2% on placebo, and 19% of survodutide patients stopped treatment because of gastrointestinal events. It was published in the New England Journal of Medicine in June 2026.
• Oral options: orforglipron (Foundayo) is already approved; see our orforglipron landscape.
• Amgen’s MariTide: its Phase 3 MARITIME program is enrolling and ongoing, and Amgen’s November 3, 2026 release gives no data timing.

What to watch

• Peer-reviewed publication of TRIUMPH-2, TRIUMPH-3 and TRANSCEND-T2D-2. Lilly says detailed results will come at future meetings and in journals, without dates.
• Whether dysesthesia and discontinuation rates look different in the full data, since they will shape how the label and market position are read.
• Cardiovascular outcomes: in TRIUMPH-3, event counts were small and the confidence intervals included 1.0 (for example MACE-5 HR 0.82, 95% CI 0.55-1.22), so no benefit was shown. Lilly lists cardiovascular and renal outcomes trials as ongoing.

For background on how crowded this space is, see our look at obesity trial volume, our survodutide spotlight, and our guide to reading a ClinicalTrials.gov record.

Recent developments

Updated November 4, 2026. Items are drawn from company announcements, regulators and trade press; links go to the sources.

• Oct 28, 2026: Lilly reported topline results of TRANSCEND-T2D-2, its sixth positive Phase 3 retatrutide trial, against Ozempic 2 mg (see above). Discontinuations due to adverse events were 4.8% (9 mg) and 7.9% (12 mg) versus 2.7% for semaglutide. Lilly’s October 29 earnings release repeats the result. (HCPLive; Lilly 8-K)
• Jul 23, 2026: Lilly reported TRIUMPH-2 (type 2 diabetes with obesity or overweight, 1,152 participants: up to 20.8% weight loss and A1C reductions up to 1.6% at 80 weeks) and TRIUMPH-3 (see above). It said it is completing the manufacturing (CMC) package and plans an FDA submission in Q1 2027. (Lilly release via BioSpace)
• Jun 5-8, 2026: TRIUMPH-1 was presented at the American Diabetes Association Scientific Sessions. In that data, nausea occurred in 42.4% at 12 mg versus 14.8% on placebo, and dysesthesia in 12.5% versus 0.9%. (HCPLive)
• May 21, 2026: Lilly announced TRIUMPH-1 topline results; at the time it anticipated a regulatory submission in 2026. (Pharmacy Times)
• Dec 11, 2025: Lilly announced the first Phase 3 result, TRIUMPH-4 in obesity with knee osteoarthritis: up to 28.7% weight loss at 68 weeks (efficacy estimand) with improved knee pain scores. (Healio)

Upcoming catalysts

• Nov 14-17, 2026: ObesityWeek, Gaylord National Resort & Convention Center, National Harbor, Maryland. We did not find any retatrutide presentation announced for it.
• Nov 2026: primary completion date listed on ClinicalTrials.gov for the retatrutide versus tirzepatide trial (a results announcement is not scheduled).
• Dec 7, 2026: Lilly Innovation Day, with more pipeline detail, per Lilly’s Q3 call. (call transcript)
• Q1 2027: Lilly’s planned FDA submission.

Bottom line

Retatrutide has posted the largest weight-loss figures reported so far in Phase 3, including against semaglutide in diabetes, but it has also shown a higher discontinuation rate at the top dose and a distinctive dysesthesia signal. Nothing has been reviewed by a regulator yet.

The next questions are the head-to-head against tirzepatide, full peer-reviewed data, and how rivals with different tolerability or dosing profiles position against it.

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This article is for informational and competitive-intelligence purposes only and is not medical advice. Approvals, labels and trial results change; verify details against current prescribing information and primary sources.