Retatrutide

What the evidence says

Retatrutide is an investigational once-weekly agonist of GIP, GLP-1, and glucagon receptors. In a 338-person phase 2 obesity trial, mean weight change at 48 weeks reached -24.2% with 12 mg versus -2.1% with placebo, with a clear dose response.^[1]

A separate phase 2 trial in people with type 2 diabetes also found substantial weight and glucose changes. A later meta-analysis pooled the still-small randomized program and confirmed dose-dependent weight reduction, but short trials cannot establish maintenance, rare harms, or cardiovascular benefit.^[2][4]

In 2026, Lilly reported topline TRIUMPH-1 phase 3 results: mean weight loss of 28.3% at 80 weeks with 12 mg versus 2.2% with placebo, with 45.3% of participants reaching at least 30% loss. These figures are company-reported and not yet a peer-reviewed pivotal publication.^[5][6]

A 98-person metabolic-liver-disease substudy found roughly 81% to 82% reductions in MRI-measured liver fat at higher doses after 24 weeks. This selected subgroup and imaging endpoint do not establish improved fibrosis, liver failure, or survival.^[3]

Gastrointestinal effects were dose related, and phase 2 showed a transient dose-related rise in heart rate. Phase 3 toplines also mention altered-sensation symptoms and dose-related discontinuation. Retatrutide remains investigational and should not be presented as an approved or commercially available treatment.^[1][5][6]