On 6 June, at the 86th Scientific Sessions of the American Diabetes Association (ADA) in New Orleans, Louisiana, findings from the Phase III TRIUMPH-1 trial (NCT05929066) were presented, assessing Eli Lilly's retatrutide in adults with obesity or overweight and at least one weight-related comorbidity, defined as a BMI of ≥30kg/m² or ≥27kg/m² with hypertension, dyslipidemia, obstructive sleep apnoea (OSA), or cardiovascular disease. While the advent of GLP-1 receptor agonists and dual incretin therapies has substantially advanced pharmacological weight management, the potential for a first-in-class triple receptor agonist to surpass these efficacy benchmarks and approach outcomes historically associated with bariatric surgery has been a defining question for the obesity pharmacotherapy field.
Retatrutide is an investigational, once-weekly subcutaneous triple hormone receptor agonist targeting glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon receptors. It is currently in Phase III investigation globally across obesity, overweight, type 2 diabetes (T2D), cardiovascular disease, and other diseases, with a new drug application (NDA) submission expected in late 2026 or early 2027.
TRIUMPH-1 was conducted as an 80-week, randomised, double-blind, placebo-controlled master trial in which 2,339 participants were randomised 1:1:1:1 to once-weekly subcutaneous retatrutide 4mg, 9mg, 12mg, or placebo, with stepwise dose escalation to their target dose every four weeks from a 2mg starting dose. The primary endpoint was the percentage change in body weight at week 80. TRIUMPH-1 additionally incorporated two basket trials evaluating retatrutide in participants with moderate-to-severe OSA and knee osteoarthritis pain, respectively.
In results presented by Ania M. Jastreboff, MD, PhD, Professor of Medicine and Pediatrics at Yale School of Medicine and director of the Yale Weight Management Center, retatrutide met its primary and all key secondary endpoints across all dose arms at week 80. At the highest dose of 12mg, participants achieved a mean body weight reduction of 28.3% (70.3lb); in a pre-specified blinded extension for subjects with a BMI of ≥35kg/m² at baseline, those on the 12mg dose achieved a mean reduction of 30.3% (85.0lb) at week 104. Categorical weight loss thresholds further underscore the magnitude of effect: at 80 weeks, a body weight reduction of ≥35% was achieved by over 25% of subjects in the study, a threshold approaching the efficacy ceiling of bariatric surgery. Furthermore, a BMI of <30kg/m² was achieved by over 65% of participants on retatrutide 12mg, and a BMI of <25kg/m² was achieved by 33.3% of participants, indicating restoration of a healthy weight range. Adverse events were broadly consistent with those observed across incretin-based therapies, with gastrointestinal events predominating. Urinary tract infections were identified as a new safety signal.
Key opinion leaders interviewed by GlobalData have anticipated the TRIUMPH-1 readout with considerable interest, with some characterising retatrutide as a "heavy gun" and a "very aggressive, very active medication" best suited to patients presenting with severe obesity and multiple comorbidities.
As retatrutide approaches regulatory submission, TRIUMPH-1 establishes it as the most efficacious pharmacological agent for obesity reported to date in a Phase III setting, delivering weight loss that is unprecedented in magnitude. These data materially strengthen retatrutide’s competitive positioning as it enters an obesity pharmacotherapy landscape. According to GlobalData’s Pharma Intelligence Center, there are 46 Phase III candidates, 110 Phase II candidates, and 165 Phase I candidates for overweight and obesity globally.
