What is Reta?
Retatrutide (also known as LY3437943) is an investigational medication developed by Eli Lilly and Company. It’s a once-weekly injectable drug classified as a triple hormone receptor agonist, meaning it simultaneously activates three key receptors:
• GLP-1 (glucagon-like peptide-1) — helps regulate appetite, blood sugar, and digestion (similar to drugs like Ozempic or semaglutide).
• GIP (glucose-dependent insulinotropic polypeptide) — enhances insulin secretion and metabolic effects (like in tirzepatide/Zepbound).
• Glucagon (GCGR) — adds unique benefits like increased energy expenditure and fat metabolism.
This triple action sets it apart from dual agonists (e.g., tirzepatide) or single GLP-1 drugs, potentially leading to greater weight loss and metabolic improvements.
Clinical Trial Results and Effectiveness
Retatrutide has shown impressive results in trials for obesity and related conditions:
• In a Phase 2 trial (published in NEJM, 2023), participants with obesity achieved substantial weight reductions over 48 weeks, with some doses leading to around 24% average body weight loss.
• In the Phase 3 TRIUMPH-4 trial (topline results announced December 2025), adults with obesity/overweight and knee osteoarthritis (without diabetes) lost up to an average of 28.7% of body weight (about 71.2 lbs in some cases) at the highest dose (12 mg) after 68 weeks. It also provided significant relief from osteoarthritis pain and improved physical function.
• Other studies indicate benefits for type 2 diabetes, metabolic dysfunction-associated steatotic liver disease (MASLD/NASH), and improvements in lipid profiles, liver health, and glycemic control.
Recent reports (February 2026) noted some participants in trials dropped out because they felt they were losing “too much” weight, highlighting its potency.
