Retatrutide

What Is Retatrutide?

Retatrutide is a synthetic peptide built to activate three hormone receptors at the same time: GLP-1 and GIP, the same two targets as tirzepatide, plus a third, the glucagon receptor. In early animal research, adding glucagon receptor activity produced greater weight loss and food intake reduction than tirzepatide alone, which is what set retatrutide apart and drove its advancement into human trials.^[1]

Retatrutide is still investigational, developed by Eli Lilly and currently working through Phase 3 clinical trials. It has not received FDA approval, so unlike semaglutide and tirzepatide, it isn't yet available as a prescribed medication.

What Retatrutide Is Being Researched For

• Body Weight

  The primary focus of retatrutide research has been its effect on body weight, with a Phase 2 trial in people with obesity reporting average reductions of up to roughly 24% at 48 weeks with the highest dose tested.^[2]

• Blood Sugar Control

  A separate Phase 2 trial in people with type 2 diabetes evaluated retatrutide's effect on blood sugar regulation alongside its effect on body weight in that population.^[3]

• Additional Metabolic Research

  Because retatrutide activates the glucagon receptor in addition to GLP-1 and GIP, research has also expanded into areas like liver fat, since glucagon signaling is tied to energy expenditure and fat metabolism beyond appetite alone.

How Retatrutide Works

• Activating Three Receptors at Once

  Research points to retatrutide binding to the GLP-1, GIP, and glucagon receptors simultaneously. The first two are shared with tirzepatide and relate mainly to insulin release and appetite signaling, while the added glucagon receptor activity is thought to contribute an energy expenditure component not present in the other two drugs.^[1]

• Reducing Food Intake and Increasing Energy Use

  Research points to retatrutide's combined receptor activity affecting both how much people eat and how their bodies use energy, a combination researchers have proposed as part of why its trial results have shown larger weight reductions than single or dual receptor medications.^[1][2]

• Lasting About a Week in the Body

  Research points to structural modifications that extend retatrutide's activity to roughly six days, supporting once-weekly dosing in the trials conducted so far.^[2]

Reconstitution and Handling

Because retatrutide is not yet an approved medication, it's currently only available through clinical trials or as a research-grade compound sold as lyophilized powder, which requires reconstitution with bacteriostatic water before use. Water should be added slowly rather than injected directly into the powder, and the vial should be swirled, not shaken.

Since the amount of water used affects the concentration of the final solution, researchers often use a dosage calculator to work this out before mixing. Once reconstituted, the solution is kept refrigerated to help preserve its stability.

Key Takeaways

Retatrutide's defining feature is its triple-receptor mechanism, adding glucagon receptor activity on top of the GLP-1 and GIP targets shared with tirzepatide. Separate Phase 2 trials in obesity and type 2 diabetes have reported larger average weight reductions than either of the two already-approved medications in this space, though it remains investigational and has not yet completed the FDA approval process. Research continues to expand into related areas like liver fat and blood sugar regulation.

Frequently Asked Questions

Sources and Research

1. Coskun T, Urva S, Roell WC, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: from discovery to clinical proof of concept. Cell Metab. 2022;34(9):1234-1247.
2. Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526.
3. Rosenstock J, Frias J, Jastreboff AM, et al. 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 conducted in the USA. Lancet. 2023;402(10401):529-544.