One weekly injection just matched the first two years of bariatric surgery: 27.6 kg off — 23.4% of body weight — in 80 weeks, in people whose BMI starts above 35. Surgery typically buys 20–35% over the same window. This drug is still in Phase 3.
On September 30, at the 62nd EASD annual meeting in Milan, Eli Lilly unveiled the full results of retatrutide's TRIUMPH-2 trial — and The Lancet published them the same day.
TRIUMPH-2 (NCT05929079) randomized about 1,152 participants with obesity or overweight plus type 2 diabetes to weekly retatrutide 4 mg, 9 mg, 12 mg, or placebo, for 80 weeks. Average weight loss: 13.5 kg (12.7%), 20.6 kg (19.1%), and 22.5 kg (20.8%) for the three doses.
The sicker group did even better. In participants with baseline BMI ≥ 35, the 12 mg arm lost 27.6 kg (23.4%) — the range surgery delivers in its first two years, without the scalpel.
Blood sugar followed. A1C fell 1.4%, 1.5%, and 1.6% across doses, and up to 40.0% of participants reached A1C < 5.7% — the normal glucose range.
The same top dose produced a list of metabolic wins, each measured: triglycerides −39.5%, non-HDL cholesterol −19.6%, systolic blood pressure −10.8 mmHg, waist circumference −16.9 cm, and high-sensitivity C-reactive protein −58.3%.
Why would one molecule do all this? Retatrutide is the first triple receptor agonist in clinical development, engaging GIP, GLP-1, and glucagon (GCG) receptors together. GLP-1 pushes insulin secretion and suppresses GCG; GIP adds insulin when glucose is high; the GCG arm is the wildcard — it raises energy expenditure and drives fat breakdown, while GIP buffers the glucose spike GCG can cause. Three mechanisms, one injection.
Safety looked tolerable: the commonest events were diarrhea, nausea, constipation, decreased appetite, and vomiting, mostly mild to moderate; discontinuation ran 3.8%, 11.6%, and 7.7% across doses versus 4.9% on placebo.
The pipeline behind it is already crowded. Novo Nordisk's CagriSema — cagrilintide plus semaglutide — beat tirzepatide head-to-head in REIMAGINE 5 (12.4% vs 9.1% weight loss) and cut 21.0% versus placebo's 2.0% in REDEFINE 9. Meanwhile Eli Lilly quietly ended an early-stage program (LY4064912), Novo returned TransCon semaglutide rights, and Pfizer wrote off part of its $10 billion Metsera deal.
This is what a winner's market looks like: 20% weight loss no longer moves the needle, and drugs get cut not because they fail but because continuing is uneconomical. After semaglutide, tirzepatide, and now retatrutide, no single selling point — weight loss, oral dosing, durability, muscle preservation, safety — guarantees success. The next winner probably needs all of them.
Lilly plans to file retatrutide in the U.S. in the first quarter of next year, with more Phase 3 readouts — knee osteoarthritis pain, obstructive sleep apnea, chronic low-back pain, cardiorenal outcomes, and MASH — due over the next twelve months. It could become the first approved triple agonist.
