Eli Lilly’s Retatrutide Sets New Weight Loss Records in Phase 3 Trials

Key points

• In the TRIUMPH-2 trial for Type 2 diabetes, patients on the highest dose lost an average of 49.6 pounds (23% of body weight) over 80 weeks, the largest loss recorded in a diabetes drug trial.
• A separate trial for patients with obesity but no diabetes showed an average weight loss of 25% after 80 weeks, with some patients losing up to 30% after an extension period.
• Retatrutide is a 'triple agonist' targeting GLP-1, GIP, and glucagon, distinguishing it from current dual-agonist competitors like tirzepatide (Mounjaro/Zepbound).
• The drug significantly improved cardiometabolic markers, including blood pressure and cholesterol, and reduced inflammation markers, with 72% of diabetic patients achieving HbA1c levels below the diabetes threshold.
• Side effects were primarily gastrointestinal, similar to other GLP-1 drugs, with about 8% of high-dose patients discontinuing the medication due to adverse events.

Background

This development follows recent FDA approvals for tirzepatide to reduce cardiovascular risk in high-risk Type 2 diabetes patients and public attention on GLP-1 efficacy, including Illinois Governor JB Pritzker’s reported 80-pound weight loss. Roche recently reported phase 2 data for its dual-agonist enicepatide, positioning itself as a competitor in the obesity drug market, though Lilly’s retatrutide results appear superior in magnitude of weight loss.

How outlets are covering it

NBC News and Scientific American emphasize the historic nature of the weight loss results, noting that retatrutide’s efficacy in diabetic patients is particularly significant since this group typically struggles with weight loss on current medications. The Guardian highlights the broader cardiometabolic benefits, including reduced inflammation and improved lipid profiles, while noting the trial’s global scope across eight countries. Ars Technica focuses on the drug’s potential to rival bariatric surgery, citing data from the obesity-only trial where severe obesity patients lost up to 30% of their weight. All sources agree on the drug’s mechanism as a triple agonist but differ in emphasis: NBC and SciAm focus on the diabetes-specific breakthrough, while Ars and The Guardian highlight the broader obesity and metabolic benefits. No source disputes the efficacy data, but Ars Technica notes the lack of head-to-head comparisons with existing drugs like tirzepatide as a limitation.

Why it matters

Retatrutide represents a potential paradigm shift in treating obesity and Type 2 diabetes, offering weight loss results comparable to bariatric surgery without surgical risks. Its success could reshape the GLP-1 drug market, potentially displacing current leaders like Ozempic and Mounjaro. The drug’s additional benefits for sleep apnea and knee pain may expand its clinical utility. However, the rapid emergence of unapproved versions raises concerns about safety and regulatory oversight, while the lack of head-to-head trials means its relative superiority to existing drugs remains unproven in direct comparison.

What to watch

Eli Lilly plans to submit retatrutide for FDA approval early next year. The company is also pursuing approval in other global markets. Meanwhile, Lilly has filed lawsuits against companies selling unapproved versions of the drug through wellness platforms and compounding pharmacies. Further trials are needed to compare retatrutide directly with existing GLP-1 drugs and to assess long-term safety, including rare cardiovascular events and pancreatitis risks.