Retatrutide

Why scientists study it

• One molecule switches on the GLP-1, GIP and glucagon receptors together. The design is meant to join incretin pathways and energy-use pathways in a single compound.
• In a 48-week phase 2 trial, adults with obesity on the top dose lost about 24% of their body weight on average. In an 80-week phase 3 trial published in 2026, the figure was 25%.
• A sub-study and pooled analyses looked at its effects on fat and lean mass, blood fats and blood pressure. Phase 3 trials in obesity and in type 2 diabetes were published in 2026.

Three studies to know

Jastreboff and colleagues, 2023 · New England Journal of Medicine

This 48-week phase 2 trial tested four once-weekly dose levels, from 1 mg to 12 mg, against a placebo in adults with obesity. Body weight fell more as the dose went up. At the top dose the average drop was 24.2%, against 2.1% with placebo. Read the paper

Rosenstock and colleagues, 2023 · The Lancet

This phase 2 trial tested a range of doses in adults with type 2 diabetes. It reported results for blood sugar control and body weight, compared with a placebo and with an active drug. Read the paper

Coskun and colleagues, 2022 · Cell Metabolism

This paper covers the lab discovery of LY3437943, which acts on the GIP, GLP-1 and glucagon receptors, and describes how it behaves as a drug. It follows the work from the bench to the first proof of concept in people. Read the paper

Safety and legal status

• Retatrutide is still under study. As of 2026, it is not approved by the FDA, the EMA or the MHRA for any medical use in people.
• It is a peptide hormone that switches on receptors. That class falls under class S2 of the World Anti-Doping Agency Prohibited List.
• For laboratory research use only. It is not for human use.