Every medicine in this class is a prescription product in its authorised uses. The molecules sold under the same names on the grey market are not those medicines. That distinction sits under the whole of this article.
What "incretin mimetic" means
Incretins are gut hormones released after a meal that amplify insulin release and act on appetite. Two matter here: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). An incretin mimetic is a peptide engineered to reproduce or extend that signalling. Over a decade the class has moved from single-receptor agonists to molecules that engage two or three related receptors at once.
Single-receptor agonists (GLP-1)
Exenatide and liraglutide were the first generation. Semaglutide is the best characterised, with the deepest outcome-trial record. In STEP 1, semaglutide 2.4 mg produced a mean weight reduction of about 14.9% at 68 weeks in adults with overweight or obesity and without diabetes, against about 2.4% with placebo. Semaglutide is licensed in the UK under several brands and, since 2026, as an oral tablet.
Dual GIP/GLP-1 agonists
Tirzepatide activates both the GIP and the GLP-1 receptor. In SURMOUNT-1, mean weight reduction at 72 weeks was 15.0%, 19.5% and 20.9% at 5 mg, 10 mg and 15 mg respectively, against 3.1% with placebo. It is licensed in the UK for type 2 diabetes and for weight management. The dual mechanism is the current evidence ceiling for a licensed incretin mimetic.
Triple agonists
Retatrutide adds glucagon-receptor agonism to GIP and GLP-1. It is not licensed in the UK. The TRIUMPH Phase 3 programme has reported substantial mean weight reductions, and the 2026 Lancet review of the field places next-generation multi-receptor agonists at up to roughly 24% mean weight loss in late-phase trials. Those are group means from specific regimens; they are not individual predictions, and the glucagon component carries its own open questions about tolerability and lean mass.
The UK licensing picture
The MHRA licenses each product separately, and the class does not move as one. GLP-1 receptor agonists and tirzepatide are licensed for their authorised indications. Orforglipron, a non-peptide oral GLP-1 receptor agonist, was licensed by the MHRA on 10 August 2026 — the first such approval in Europe. Retatrutide, mazdutide and survodutide remain investigational. NICE recommends individual products within defined eligibility criteria; a class-level assertion that "GLP-1s are recommended" is not accurate.
Safety: a class-wide regulatory signal
On 29 January 2026 the MHRA updated the product information for all UK GLP-1 receptor agonists and dual GLP-1/GIP receptor agonists to strengthen warnings on severe acute pancreatitis, including rare reports of necrotising and fatal cases. The regulator reminded clinicians to remain alert to the early symptoms. This is a class-wide signal, reported through the Yellow Card scheme, and it is why the class is described here as medicines with known risk profiles rather than as research compounds.
What a receptor profile does and does not tell you
A receptor profile predicts mechanism, not outcome. The headline percentages above come from different trials, populations and regimens, and cannot be ranked against one another without head-to-head data. Where a direct comparison exists — as in the CagriSema versus tirzepatide REDEFINE 4 readout — it tends to complicate the picture rather than simplify it.
Evidence grades in this class
Single-receptor and dual agonists with Phase 3 outcome data and a UK licence grade Strong in this reference. Investigational multi-receptor agonists are graded Moderate: Phase 3 data are reported, but there is no licence and no long-term outcome record. Preparations sold for research use only carry no evidence grade, because there is no product-specific evidence to grade.
This article is AI-researched and editorially reviewed. It is provided for research and educational purposes only and is not medical advice. Research peptides are not licensed for human consumption in the UK.