Research Education
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Retatrutide and Tirzepatide come up together a lot, and for good reason. Both are synthetic peptides studied in metabolic receptor pharmacology, both came out of the same incretin research programme, and both are built on a lipidated, GIP-based peptide backbone. The big difference is how many receptors each one was designed to act on. This page compares what the published literature examines, for research reference purposes only.
Tirzepatide is a dual agonist, studied at the GIP and GLP-1 receptors. Retatrutide is a triple agonist, studied at the GIP, GLP-1 and glucagon receptors. That third target, the glucagon receptor, is the main pharmacological difference researchers focus on when comparing the two.
Tirzepatide (development code LY3298176) was first described in 2018 by Coskun and colleagues in Molecular Metabolism. It is a 39 amino acid peptide based on the native GIP sequence, with a C20 fatty diacid attached through a linker. That lipid side chain supports albumin binding, and published pharmacokinetic studies report a half-life of around five days.
Retatrutide (LY3437943) followed in 2022, again described by Coskun and colleagues, this time in Cell Metabolism. It uses a similar design approach, a lipidated GIP-based peptide, but was engineered to activate the glucagon receptor as well. Published pharmacokinetic data report a half-life of roughly six days.
| Feature | Tirzepatide | Retatrutide |
|---|---|---|
| Development code | LY3298176 | LY3437943 |
| Receptor targets studied | GIP, GLP-1 | GIP, GLP-1, glucagon |
| Agonist class | Dual | Triple |
| Backbone | GIP-based, lipidated | GIP-based, lipidated |
| Reported half-life | About 5 days | About 6 days |
| Key early publication | Coskun et al., Molecular Metabolism, 2018 | Coskun et al., Cell Metabolism, 2022 |
| Clinical research stage | Completed phase 3 programmes (SURPASS, SURMOUNT) | Phase 3 programme (TRIUMPH) reporting from 2026 |
Neither compound activates its targets equally. Willard and colleagues (JCI Insight, 2020) described Tirzepatide as an imbalanced agonist, with greater relative activity at the GIP receptor than at the GLP-1 receptor. The same work reported biased signalling at the GLP-1 receptor, favouring cAMP generation over beta-arrestin recruitment.
The original characterisation of Retatrutide reported higher potency at the human GIP receptor, and lower potency at the GLP-1 and glucagon receptors, compared with each receptor's native ligand. These potency profiles are a big part of why the two compounds are studied side by side rather than treated as interchangeable.
The glucagon receptor is studied mainly in hepatic metabolism and energy expenditure research. Adding glucagon receptor activity to GIP and GLP-1 agonism is investigated as a way to understand how the three pathways interact. Much of the comparative interest in Retatrutide comes down to one question: what changes in a model when a third receptor is added to a dual agonist design?
Both molecules have been through human clinical trials run by their developer. Tirzepatide's phase 3 programmes, SURPASS and SURMOUNT, examined glycaemic and body weight endpoints. Retatrutide's phase 2 results were published in 2023 (Jastreboff et al., New England Journal of Medicine; Rosenstock et al., The Lancet), and its phase 3 TRIUMPH programme began reporting topline results in 2026.
These were pharmaceutical development programmes using products manufactured under medicinal controls. They're referenced here for research context only, and say nothing about the research reference materials supplied by PerformanceLabsUK.
Both compounds are listed as research reference materials: Retatrutide and Tirzepatide. For a closer look at each, see the Retatrutide research overview, the Tirzepatide research overview and the wider guide to GLP-1, GIP and glucagon receptor agonist research.
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