The Peptide Atlas
Retatrutide
An experimental weekly peptide that acts on three metabolic hormone receptors at once: GLP-1, GIP, and glucagon.
Class
Triple agonist (GIP/GLP-1/glucagon)
Evidence
Human-tested
Status
In late-stage clinical trials.
Forms
Weekly injection (in trials)
What people use it for
Watched, more than used: the next weight-loss drug people are waiting on.
The signal
The same appetite signals semaglutide and tirzepatide work through, plus a third: the glucagon receptor, which nudges the body to burn more energy rather than only eat less.
How it works
One molecule, three receptors. The GLP-1 and GIP activity quiets appetite the way the approved drugs do; the glucagon activity adds an energy-expenditure effect on top.
What the research shows
In its Phase 2 trial, adults lost 24.2% of their body weight on average at the highest dose over 48 weeks, the largest reduction reported for any obesity drug in trials at the time [1]. A separate Phase 2 in type 2 diabetes showed strong glucose results [2]. Phase 3 trials are running now.
What people get wrong
That you can get it. It isn't approved or legally available anywhere yet, so anything sold as "retatrutide" today comes from unregulated labs, with no connection to the trial drug. The Phase 2 numbers are also averages at the top dose, not a promise of what any one person loses.
References
- Jastreboff AM et al., N Engl J Med (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. PubMed
- Rosenstock J et al., Lancet (2023). Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial. PubMed
Last reviewed 2026-08-24. Every reference is verified against the primary literature at review time. How the Atlas grades evidence