Retatrutide

What does retatrutide target?

Retatrutide, also called LY3437943, is an agonist of the glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1) and glucagon receptors, given as a once-weekly subcutaneous injection [1]. Lilly describes it as a "first-in-class GIP, GLP-1, and glucagon triple hormone receptor agonist," a step beyond the dual agonist tirzepatide [3].

What have retatrutide's trials shown?

In a phase 2 obesity trial, participants on the 8 mg and 12 mg doses lost 22.8% and 24.2% of body weight at 48 weeks, versus 2.1% on placebo [1]. In Lilly's phase 3 TRIUMPH-1 obesity trial, reported May 21, 2026, average weight loss at 80 weeks reached 28.3% on the 12 mg dose [3]. On July 23, 2026, Lilly reported two further phase 3 obesity trials, TRIUMPH-2 and TRIUMPH-3, and said it plans to submit a Biologics License Application to FDA in the first quarter of 2027 [2].

Is retatrutide FDA-approved?

No. Retatrutide is investigational and, per Lilly, "available only to participants in Lilly's clinical trials" [3]. FDA has stated that retatrutide cannot be used in compounding under federal law, is not a component of any FDA-approved drug, and has not been found safe and effective for any condition [4].