Eli Lilly and Company (NYSE: LLY) announced positive topline results from TRANSCEND-T2D-1, the first Phase III trial evaluating retatrutide in adults with type 2 diabetes inadequately controlled by diet and exercise alone. The data showed A1C reductions of up to 2.0% and body weight loss of up to 16.8% at 40 weeks, positioning the Lilly triple agonist as a potential new entrant in a treatment landscape already reshaped by incretin-based therapies.
Trial specifics
TRANSCEND-T2D-1 is a 40-week, randomized, double-blind, placebo-controlled Phase III study that enrolled 537 adults with type 2 diabetes and a mean disease duration of 2.5 years. Participants had baseline A1C between 7.0% and 9.5%, a BMI of at least 23 kg/m², and had not used anti-diabetes medications for at least 90 days. They were randomized 1:1:1:1 to retatrutide 4 mg, 9 mg, or 12 mg, or placebo, administered once weekly with stepwise dose escalation from a starting dose of 2 mg.
For the primary endpoint of change in A1C from a baseline of 7.9%, retatrutide achieved reductions of 1.7%, 2.0%, and 1.9% at the 4 mg, 9 mg, and 12 mg doses respectively, compared with 0.8% for placebo, using the efficacy estimand. On the key secondary endpoint of percentage change in body weight from a baseline of 96.9 kg, participants on the 12 mg dose lost an average of 16.8% (36.6 lbs), compared with 2.5% (6.2 lbs) for placebo. The company reported that no weight loss plateau was observed through the 40-week treatment period. Retatrutide also showed reductions in non-HDL cholesterol, triglycerides, and systolic blood pressure, though these cardiovascular risk factor improvements were only controlled for type I error at the 9 mg and 12 mg doses.
Gastrointestinal adverse events were the most common, consistent with the incretin class. Nausea occurred in 16.4% to 26.5% of retatrutide-treated participants versus 3.7% on placebo; diarrhea in 18.7% to 26.3% versus 4.5%; and vomiting in 15.7% to 17.6% versus 2.2%. These events occurred primarily during dose escalation. Dysesthesia, a sensory disturbance not typically associated with GLP-1 receptor agonists, was reported in 2.3% to 4.5% of retatrutide-treated participants versus none on placebo; the company described these events as generally mild and mostly resolving during treatment. Discontinuation due to adverse events ranged from 2.2% to 5.1% across retatrutide doses, compared with 0% for placebo.
Development context
Lilly stated that detailed TRANSCEND-T2D-1 results will be presented at the American Diabetes Association Scientific Sessions in June and published in a peer-reviewed journal. The broader TRANSCEND-T2D program encompasses three global registrational trials that have enrolled more than 2,050 participants, with additional readouts expected over the next year. Beyond type 2 diabetes, Lilly is running Phase III trials of retatrutide in obesity, obstructive sleep apnea, knee osteoarthritis, chronic low back pain, cardiovascular and renal outcomes, and metabolic dysfunction-associated steatotic liver disease.
Research context
Retatrutide is a once-weekly peptide that simultaneously activates three receptors: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon. The GIP and GLP-1 components enhance glucose-dependent insulin secretion and reduce appetite, mechanisms shared with dual agonists such as tirzepatide. The addition of glucagon receptor agonism is hypothesized to increase hepatic energy expenditure and lipid oxidation, which may account for the degree of weight loss observed. This triple receptor engagement distinguishes retatrutide from existing approved incretin therapies and is the central pharmacological rationale for the molecule.