Retatrutide: Triple GLP-1 / GIP / Glucagon Agonist

What Retatrutide is

Retatrutide is a synthetic single-chain incretin analog developed by Eli Lilly under the code LY3437943. It is an investigational compound — at the time of writing it is not approved by the FDA or any regulatory agency; it remains in Phase 3 trials.

What sets it apart from the previous generation of analogs is its triple agonism: a single molecule activates the GLP-1, GIP and glucagon receptors. Earlier molecules activated one (semaglutide) or two (tirzepatide) of these receptors.

The triple agonism

"Incretins" are gut hormones that coordinate the body's response to food. Retatrutide combines three axes in a single structure:

• GLP-1 (glucagon-like peptide-1) — satiety, slower gastric emptying, glucose-dependent insulin secretion.
• GIP (glucose-dependent insulinotropic polypeptide) — potentiates insulin secretion and modulates adipose tissue.
• Glucagon (GCGR) — this is the novelty: glucagon agonism increases energy expenditure and promotes hepatic fat mobilization and lipolysis.

The added glucagon component is thought to be responsible for the magnitude of weight loss observed: instead of only reducing intake (like GLP-1), it also increases caloric expenditure.

Each receptor's role

GLP-1: the foundation

The GLP-1 arm reduces appetite at the central nervous system level, slows gastric emptying, and improves insulin secretion only when glucose is elevated (low hypoglycemia risk). It is the best-characterized mechanism in the whole class.

GIP: the potentiator

GIP's role is more debated, but the evidence suggests that combined with GLP-1 it improves glycemic control and lipid handling in adipose tissue, while also blunting nausea — an effect that can improve tolerability.

Glucagon: the differentiator

Glucagon agonism is the most distinctive component. At the hepatic level it mobilizes fat (relevant for steatosis/MASLD research) and systemically it raises energy expenditure. It is also the axis that demands the most attention in research: it can raise heart rate and, theoretically, glucose, so the balance among the three receptors in the molecule is carefully engineered.

Clinical evidence

Phase 2 (obesity) — NEJM 2023

The Phase 2 obesity trial (Jastreboff et al., published in the New England Journal of Medicine in 2023) reported mean weight reductions of up to ~24% at 48 weeks in the highest-dose group — figures not previously seen with an injectable incretin agonist, approaching bariatric-surgery territory.

Phase 2 (type 2 diabetes)

A parallel type 2 diabetes trial showed significant reductions in HbA1c and weight, with a safety profile consistent with the class (dose-dependent gastrointestinal effects that improve with titration).

Phase 3 — the TRIUMPH program

Eli Lilly has the Phase 3 TRIUMPH program underway, evaluating retatrutide in obesity, diabetes and related conditions. Results from these trials will determine an eventual regulatory approval.

Retatrutide vs Tirzepatide vs Semaglutide

Compound	Receptors	Status
Semaglutide	GLP-1 (mono)	Approved
Tirzepatide	GLP-1 + GIP (dual)	Approved
Retatrutide	GLP-1 + GIP + glucagon (triple)	Phase 3 (research)

The mono → dual → triple progression reflects the strategy of adding hormonal axes to amplify the metabolic effect. We cover the practical comparison with tirzepatide in our Tirzepatide vs Retatrutide guide, and the fundamentals of the class in GLP-1: How Incretin Analogs Work.

Reconstitution

The pre-mixed 10 mg presentation comes reconstituted in 2 mL, giving a concentration of 5 mg/mL. Higher-mg presentations keep the 10 mg/mL ratio, except the 10 mg which is offered at 5 mg/mL for better precision in small volumes.

Calculation example (10 mg vial + 2 mL = 5 mg/mL): to research 2 mg → 0.4 mL → 40 units on a U100 syringe.

The lyophilized powder variants are reconstituted with your own bacteriostatic water at the concentration you define. Refrigerate (2–8 °C) after reconstitution. For custom calculations use the reconstitution calculator or see the complete reconstitution guide.

Retatrutide at Renova

Retatrutide is available in several presentations, pre-mixed and lyophilized powder:

• 10 mg — $160 · 20 mg — $320 · 30 mg — $390 · 60 mg — $685
• 60 mg powder — $575

Our material is manufactured in a cGMP-compliant US lab that we work with directly, with a Certificate of Analysis (COA) by HPLC and mass spectrometry.