One-page index of every GLP-1, GLP-1/GIP, GLP-1/GIP/GCGR, and amylin/GLP-1 reference page on Peptides Lab UK — grounded in primary trial data from SURMOUNT, REDEFINE, FLOW, SELECT, ESSENCE, SYNERGY-NASH, and TRIUMPH. For laboratory research use only.
What is a GLP-1 receptor agonist?
Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted by intestinal L-cells that potentiates glucose-dependent insulin secretion, suppresses glucagon release, slows gastric emptying, and acts centrally on satiety circuits. Synthetic GLP-1 receptor agonists are peptide analogues engineered for resistance to dipeptidyl-peptidase-4 (DPP-4) cleavage and extended pharmacokinetic half-life, enabling once-weekly subcutaneous dosing in clinical research.
The class has expanded rapidly between 2017 and 2026 from native single-receptor agonists (semaglutide, liraglutide) to dual GLP-1/GIP agonists (tirzepatide), triple GLP-1/GIP/GCGR agonists (retatrutide, survodutide for GLP-1/GCGR), and combinations with amylin analogues (CagriSema). Each generation expands the pharmacological footprint and the body-weight reduction observed in research participants with obesity.
Class comparison — at a glance
| Compound | Receptor profile | Half-life | Dosing | Headline trial | Mean body-weight change |
|---|---|---|---|---|---|
| Liraglutide | GLP-1 | ~13 h | Daily SC | SCALE | ~ -8% (3 mg) |
| Semaglutide | GLP-1 | ~165 h | Weekly SC | STEP-1 | ~ -14.9% (2.4 mg) |
| Tirzepatide | GLP-1 + GIP | ~120 h | Weekly SC | SURMOUNT-1 | ~ -22.5% (15 mg) |
| Retatrutide | GLP-1 + GIP + GCGR | ~140 h | Weekly SC | TRIUMPH-1 (Ph 2) | ~ -24.2% (12 mg, 48 wk) |
| Survodutide | GLP-1 + GCGR | ~130 h | Weekly SC | SYNCHRONIZE / Ph 2 obesity | ~ -19% (Ph 2) |
| CagriSema (cagrilintide + semaglutide) | GLP-1 + amylin | ~165 h | Weekly SC (combination) | REDEFINE-1 | ~ -22.7% (Ph 3) |
All figures from peer-reviewed Phase 2/3 publications. Body-weight change reported as least-squares mean change from baseline at the primary endpoint analysis time-point of the cited trial. Compounds are supplied for in-vitro and preclinical research use only and are not authorised by the MHRA for human medicinal use unless otherwise stated.
Mechanism — what GLP-1 receptors do
GLP-1 receptors are class B G-protein-coupled receptors (GPCRs) expressed on pancreatic β-cells, α-cells, gastric parietal cells, vagal afferents, hypothalamic arcuate-nucleus neurons, and renal proximal tubule cells. Receptor activation triggers Gαs coupling, adenylyl-cyclase stimulation, intracellular cAMP elevation, and downstream PKA / Epac2 signalling.
The pharmacological consequences observed in research are:
- Glucose-dependent insulin release — insulinotropic effect occurs only when plasma glucose is elevated, reducing hypoglycaemia risk relative to insulin secretagogues.
- Glucagon suppression — α-cell glucagon output is reduced, contributing to lower hepatic gluconeogenesis.
- Delayed gastric emptying — slows postprandial glucose excursion and reduces meal size in research participants.
- Central satiety signalling — arcuate-nucleus POMC/CART activation and AgRP/NPY suppression reduce caloric intake.
- Renal natriuresis & cardio-renal effects — driver of FLOW trial endpoints in chronic kidney disease research.
Trial readouts — what the 2026 evidence base looks like
Single agonists (GLP-1 only)
- STEP / SUSTAIN (semaglutide) — full reference: Semaglutide UK 2026 Research Reference.
- SELECT (semaglutide cardiovascular outcomes) — primary MACE endpoint reduction in adults with obesity and pre-existing CVD; covered in the semaglutide reference above.
- FLOW (semaglutide in CKD) — 24% relative risk reduction in primary kidney composite outcome — full data in GLP-1 hepatic / renal hub.
- STEP-8 vs SUSTAIN-10 (semaglutide vs liraglutide) — head-to-head pharmacokinetics and weight-loss efficacy: comparison reference.
Dual agonists (GLP-1 + GIP)
- SURMOUNT-1 → SURMOUNT-5 (tirzepatide) — body-weight, glycaemic, hepatic, and head-to-head endpoints. SURMOUNT-5 head-to-head vs semaglutide: tirzepatide vs semaglutide comparison.
- SURMOUNT timeline by week: tirzepatide weight-loss timeline.
Triple agonists (GLP-1 + GIP + GCGR)
- TRIUMPH-1 (retatrutide Phase 2) — 24.2% body-weight reduction at 48 weeks, 12 mg dose. TRIUMPH-2/3/4 Phase 3 readouts ongoing through 2026. See retatrutide product page for batch-level COA.
GLP-1 + glucagon
- Survodutide Phase 2 obesity / MASH — full reference: survodutide reference.
GLP-1 + amylin
- REDEFINE-1 (CagriSema Phase 3) — full reference: cagrilintide + CagriSema.
Class side effects (research observations)
GLP-1 class side effects observed in research participants are predominantly gastrointestinal: nausea (15–45% incidence depending on titration speed), vomiting (5–18%), diarrhoea (10–22%), constipation (8–15%). Class-effect injection-site reactions occur in 3–8%. Lower-incidence signals being investigated in long-term cohorts include gallbladder disease and pancreatitis. Full mechanism-and-mitigation reference: GLP-1 side-effects reference.
Sourcing for UK research
Research-grade GLP-1 analogues should be sourced only from suppliers providing per-batch HPLC purity, mass-spectrometry identity confirmation, and bacterial endotoxin quantification on an independent third-party Certificate of Analysis. Peptides Lab UK supplies all GLP-1-class research peptides with a COA from Optima Labs (UK) and ships UK orders next working day.
See the Research-Grade Peptides Buyer’s Guide for sourcing criteria, and the Research Quality Standards SOP for the full quality framework.
Available GLP-1 research peptides
- Semaglutide — single GLP-1 agonist
- Tirzepatide — dual GLP-1/GIP agonist
- Retatrutide — triple GLP-1/GIP/GCGR agonist
- Survodutide — dual GLP-1/GCGR agonist
- GLP-1 (native)
FAQs — GLP-1 receptor agonists in UK research
Are GLP-1 peptides legal in the UK for research?
Yes. GLP-1 receptor agonists are not controlled substances under the UK Misuse of Drugs Act 1971 and may be supplied for laboratory research use only. Several (e.g., semaglutide as Wegovy/Ozempic, tirzepatide as Mounjaro) are also separately MHRA-authorised for human medicinal use under prescription — those formulations are distinct from research-grade material.
What is the strongest GLP-1 peptide by weight reduction in research?
As of April 2026, retatrutide (triple GLP-1/GIP/GCGR) holds the largest published weight-loss endpoint from a Phase 2 trial (~24.2% at 48 weeks, TRIUMPH-1, 12 mg). Phase 3 confirmation is pending TRIUMPH-2/3/4 readouts.
What is the difference between semaglutide and tirzepatide?
Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual GLP-1 / GIP receptor agonist with an additional incretin pathway. Direct head-to-head data (SURMOUNT-5) shows tirzepatide produces greater body-weight reduction at matched durations.
Can I source GLP-1 peptides for research in the UK with next-day delivery?
Yes. Peptides Lab UK ships every GLP-1 SKU same-day on orders before 14:00 GMT/BST, with Royal Mail Tracked 24 next-working-day delivery in the UK and tracked DHL/UPS to the EU.
Last updated: 26 April 2026. Reviewed by William, Lead Research Editor, Peptides Lab UK. All products are for in-vitro and preclinical research use only.
