Retatrutide vs Tirzepatide: How the Two Research Peptides Differ

Retatrutide and tirzepatide are often mentioned together because both are long-acting synthetic peptides that act on incretin hormone receptors. They are not the same compound, though, and they are at very different stages of development. This guide sets out the differences that matter when you are comparing the two for research.

The short answer

• Tirzepatide (research code LY3298176) acts on two receptors: GIP and GLP-1. It is a dual agonist.
• Retatrutide (research code LY3437943) acts on three receptors: GIP, GLP-1 and glucagon. It is described as a triple agonist.
• Tirzepatide is an approved medicine in the UK under a brand name, prescribed by clinicians. Retatrutide is still an investigational compound in clinical trials and is not licensed anywhere in the UK.

Receptor targets

GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) are incretin hormones released from the gut after eating. Glucagon is a hormone made in the pancreas. Each of these hormones has its own receptor, and a peptide can be designed to activate one, two or all three.

Semaglutide activates the GLP-1 receptor only. Tirzepatide adds GIP receptor activity. Retatrutide adds glucagon receptor activity on top of both. Researchers are interested in how the balance between these receptors changes the overall effect of the molecule, which is why the three compounds are so often compared.

Structure

Both peptides are built on a chain of about 39 amino acids with a fatty-acid side chain attached. The side chain lets the peptide bind to albumin in the blood, which slows its clearance and gives both compounds a long half-life (several days). The amino acid sequences are different, which is what changes the receptor profile.

Clinical research programmes

Tirzepatide was studied in the large SURPASS (type 2 diabetes) and SURMOUNT (weight management) trial programmes before approval. Retatrutide is being studied in the TRIUMPH programme of Phase 3 trials. Until those trials are complete and a regulator has reviewed the results, retatrutide remains an investigational compound.

What this means for research supply

Research-grade retatrutide and tirzepatide are supplied as lyophilised (freeze-dried) powders for laboratory use. They are not licensed medicines and are not the branded pharmaceutical products. When you compare research listings, check:

• the exact compound and strength on the label (for example 20mg, 40mg or 60mg);
• the batch number, and whether a certificate of analysis for that batch is published;
• the identity and HPLC purity results in the lab report, and the name of the testing laboratory;
• storage advice: keep the powder at 2–8°C and away from light, or frozen for long-term storage.

Evora products

Evora lists retatrutide 20mg, retatrutide 40mg and retatrutide 60mg, plus KLIKJARO tirzepatide 40mg and 60mg. Combined formulations with cagrilintide, an amylin analogue, include RETAKLIK 2.0. Published batch reports are on our COAs page.