The next-gen triple agonist versus the current dual-agonist leader.
| Attribute | Retatrutide Investigational | Tirzepatide FDA-approved |
|---|---|---|
| Class / type | GLP-1 / GIP / glucagon triple agonist | Dual GIP / GLP-1 agonist |
| How it works | Activates GLP-1, GIP and glucagon receptors at once; the glucagon arm may add an energy-expenditure/fat-oxidation effect beyond GLP-1/GIP drugs. | Activates both GIP and GLP-1 receptors: raises glucose-dependent insulin, lowers glucagon, slows gastric emptying, strongly suppresses appetite. |
| Known / used for | Obesity, type 2 diabetes; studied for MASH (fatty liver). | Type 2 diabetes (Mounjaro), weight management (Zepbound), obstructive sleep apnea with obesity (Zepbound). |
| Positives | Best-in-class trial weight loss - Phase 3 TRIUMPH data show ~28% average loss (28.3% at 80 wks); strong glycemic/metabolic improvement. | Among the most effective approved agents (~20%+ weight loss); strong A1c reduction; added OSA indication. |
| Negatives & risks | GI effects during titration (nausea, constipation); raised resting heart rate; fatigue; skin tingling/dysesthesia reported. Long-term safety unknown; not approved. | GI effects (nausea, diarrhea, vomiting, constipation); injection-site reactions, fatigue, reported hair loss; boxed thyroid C-cell tumor warning; rare pancreatitis. |
| Legal status (Jul 2026) | NOT FDA-approved. All four Phase 3 TRIUMPH trials are now complete; the NDA is expected around Q4 2026-Q1 2027, with possible approval late 2027-2028. In Aug 2026 Eli Lilly opened a limited early-access program for a defined patient group ahead of approval. Anything otherwise sold now is gray-market / research-use-only. | FDA-approved prescription drug (Mounjaro, Zepbound). Gray-market 'research' vials are NOT the approved product. The FDA is also winding down compounded versions. |
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