Researchers have published an expanded set of findings on retatrutide, a drug under investigation for weight management that works by engaging three distinct metabolic pathways — GLP-1, GIP, and glucagon — a combination no approved treatment has previously attempted. Regulatory submission to the FDA is anticipated in the early months of next year, once the drug completes the final phase of its clinical trial programme.

Data released by Eli Lilly from its Phase 3 "Triumph-4" trial, published within the current year, showed that participants shed an average of 28.7% of their total body weight over the course of the study. Withdrawal numbers ran above those recorded in previous studies, with a portion of participants choosing to leave after their body weight fell further than intended.

Data released by Lilly from a separate Phase 3 trial indicated that even at the lowest dose tested, participants recorded notable outcomes. Participants assigned to the lowest available dose — a 4 mg weekly injection — shed an average of 29.8 pounds, representing roughly 12.7% of their starting body weight.

Where GLP-1 receptor agonists such as Ozempic act on a single pathway, and dual-action therapies like Mounjaro and Zepbound engage two — either GLP-1 paired with GIP, or GLP-1 paired with glucagon — retatrutide is formulated to activate all three receptor types simultaneously.

Three dosage levels of retatrutide — 4 mg, 9 mg, and 12 mg — were among the findings Lilly put forward for public review. By the 80-week mark, those taking the lowest dose had shed an average of 29.8 pounds — roughly 12.7% of their body weight — while participants on the middle dose dropped 45.4 pounds (19.1%), and those assigned the highest dose saw reductions of 49.6 pounds, or about 20.8% of their starting weight.

Beyond its effect on weight, retatrutide also drove down blood-glucose levels across trial participants — a finding relevant to type 2 diabetes management. Lead researcher Dr. Juan P. Frías noted that the two conditions have historically been difficult to treat in tandem, that the drug produced meaningful reductions in both body weight and A1C, that more than half of participants dropped below the threshold for an obesity diagnosis, and that up to 40 percent reached A1C readings within the normal range. At the lowest dose, average A1C fell by 1.4 percentage points, with each subsequent dose increase yielding an additional average reduction of 0.1 percentage points.

Cardiovascular outcomes were among the findings recorded during the drug's evaluation. At its peak concentration, the compound drove down readings across five health markers — triglycerides, total cholesterol, blood pressure, waist circumference, and high-sensitivity C-reactive protein.

Gastrointestinal effects — ranked from most to least frequent as diarrhea, affecting between 27.4% and 33.6% of trial participants, followed by nausea, constipation, reduced appetite, and vomiting — are consistent with the known tolerability profile of GLP-1 receptor agonists. At elevated dosages, the likelihood of adverse reactions rose in proportion to the amount administered.

Among the trial participants, between 4.5% and 7.3% experienced dysesthesia, a nerve-related condition that disrupts normal touch perception. Urinary tract infections affected a share of trial participants — ranging from 3.8% to 8% depending on dose — and the rate climbed as doses increased, though the study team noted that nearly all such cases were mild to moderate in severity and cleared up while treatment was still under way.