Peptide Basics
GLP-1 Peptides: What GLP-1 Is and How the Medicines Are Built
GLP-1 is a peptide hormone, 30 or 31 amino acids long, made mainly by cells in the intestine. The medicines known as GLP-1 drugs are peptides engineered to act on its receptor for days instead of minutes. This page sets out what GLP-1 is and where it comes from, why the natural hormone is gone within two minutes, how each approved peptide medicine was changed to last, from exenatide (2005) to tirzepatide (2022), the first GLP-1 medicine that is not a peptide, and where investigational compounds such as retatrutide stand. Every figure is taken from U.S. labels, FDA approval records, UniProt, the U.S. National Library of Medicine or the records each compound guide cites.
What GLP-1 is
Glucagon-like peptide-1 is one of the peptide hormones. MeSH describes it as a peptide of 36 or 37 amino acids, derived from proglucagon and mainly produced by the intestinal L cells, which is then shortened at its start to the active forms GLP-1(7-37) and GLP-1(7-36), the second of which can be amidated. According to MeSH, these peptides enhance glucose-dependent insulin release, suppress glucagon release and gastric emptying, lower blood glucose and reduce food intake.
GLP-1 is an incretin: one of the gut hormones that increase insulin release after a meal. The other main incretin is GIP (gastric inhibitory polypeptide, about 43 amino acids). GLP-1 acts through its own receptor, which MeSH places mainly on the beta and ductal cells of the pancreas, as well as on cells of other tissues; the Wegovy label adds that the receptor is present in several areas of the brain involved in appetite regulation.
One precursor, several peptides: proglucagon
GLP-1 is not made on its own. MeSH describes proglucagon as the common precursor of pancreatic glucagon and the intestinal glucagon-like peptides, processed differently in each tissue into several active peptides. The human record in UniProt (P01275) lists these products, shortest to longest:
| Peptide | Amino acids | Note |
|---|---|---|
| Glucagon | 29 | The pancreatic product of the same precursor. |
| GLP-1(7-36) amide | 30 | One of the two active forms; ends in arginine amide. |
| GLP-1(7-37) | 31 | The other active form; the natural molecule the medicines are compared with. |
| GLP-2 | 33 | Cut from the far end of the same precursor. |
| Oxyntomodulin | 37 | The glucagon sequence plus eight more amino acids. |
| GLP-1 (full length) | 37 | The chain before its first six amino acids are removed. |
| Glicentin | 69 | The longest product listed; it contains the whole glucagon sequence. |
Sources: UniProt P01275 (human pro-glucagon, 180 amino acids including a 20-amino-acid signal sequence); NLM MeSH descriptors D052216 and D052336. Read 1 November 2026.
Why natural GLP-1 lasts two minutes, and how the medicines last days
U.S. labels for liraglutide state that endogenous GLP-1 has a half-life of 1.5 to 2 minutes, because two enzymes, dipeptidyl peptidase-4 (DPP-4) and neutral endopeptidase, break it down almost as soon as it is released. Every GLP-1 medicine is an answer to that problem. The labels describe three approaches:
- Change the cut site. Semaglutide is modified at position 8 to resist DPP-4. Tirzepatide’s label lists aminoisobutyric acid (Aib) at positions 2 and 13 without stating its purpose.
- Attach a fatty acid that binds albumin. Liraglutide carries a 16-carbon fatty acid, semaglutide an 18-carbon fatty di-acid and tirzepatide a 20-carbon one. Bound to albumin in the blood, the molecule is filtered out by the kidneys more slowly and protected from breakdown.
- Fuse it to part of an antibody. Dulaglutide joins two GLP-1 analogue chains to a modified antibody fragment (IgG4 Fc), making a large fusion protein produced in mammalian cells.
Exenatide took a different route: it was first identified in a lizard, the Gila monster (Heloderma suspectum), and its 39-amino-acid sequence only partly overlaps human GLP-1. Its label gives a terminal half-life of 2.4 hours.
Sources: current U.S. labels via openFDA for Saxenda, Victoza, Ozempic, Mounjaro, Trulicity and Byetta. Read 1 November 2026.
The approved GLP-1 peptide medicines
In order of first U.S. approval. The structure column paraphrases each product’s U.S. label; the half-life is the elimination or terminal half-life the label gives.
| Peptide | U.S. brands | First approved | How it is built | Half-life |
|---|---|---|---|---|
| Exenatide | Byetta | 2005 | A 39-amino-acid peptide amide first found in the Gila monster (Heloderma suspectum); its sequence only partly overlaps GLP-1. | 2.4 hours |
| Liraglutide | Victoza, Saxenda | 2010 | 97% the same as human GLP-1: one amino acid swapped (arginine for lysine at 34) and a 16-carbon fatty acid attached. | About 13 hours |
| Dulaglutide | Trulicity | 2014 | Two GLP-1 analogue chains joined to part of an antibody (a modified IgG4 Fc), made in hamster ovary cells. | About 5 days |
| Lixisenatide | Adlyxin; Soliqua (with insulin glargine) | 2016 | A GLP-1 receptor agonist; the Soliqua label pairs it with insulin glargine in one product. | — |
| Semaglutide | Ozempic, Rybelsus, Wegovy | 2017 | 94% the same as human GLP-1, changed at position 8 to resist the enzyme DPP-4 and given an 18-carbon fatty di-acid that binds albumin. | About 1 week |
| Tirzepatide | Mounjaro, Zepbound | 2022 | Built on the GIP sequence, not GLP-1; activates both the GIP and GLP-1 receptors and carries a 20-carbon fatty diacid. | About 5 days |
The first GLP-1 medicine that is not a peptide. FDA approved orforglipron (Foundayo) on 1 April 2026. Its label describes a GLP-1 receptor agonist with a molecular weight of about 902, a small synthetic molecule rather than a chain of amino acids. So “GLP-1 drug” and “GLP-1 peptide” no longer mean the same thing.
Sources: Drugs@FDA original approval dates (Byetta NDA021773, Victoza NDA022341, Trulicity BLA125469, Adlyxin BLA208471, Ozempic NDA209637, Mounjaro NDA215866, Foundayo NDA220934); U.S. labels via openFDA for Byetta, Saxenda, Trulicity, Soliqua 100/33, Ozempic, Wegovy, Mounjaro, Zepbound and Foundayo. Read 1 November 2026.
Beyond GLP-1: dual and triple agonists
Tirzepatide began a second generation: peptides that act on more than one hormone receptor. Its label describes a molecule built on the GIP sequence that activates both the GIP and the GLP-1 receptors. Several newer compounds go further. None of the four below has an FDA approval; each guide sets out its identity, research history and regulatory status.
| Compound | Receptors it acts on | Regulatory position |
|---|---|---|
| Retatrutide | GIP, GLP-1 and glucagon receptors (a triple agonist) | No FDA approval; phase 2 obesity trial published in NEJM in 2023. |
| Mazdutide | Glucagon and GLP-1 receptors (a dual agonist) | No FDA approval; approved in China in June 2025, according to its developer’s stock-exchange announcement. |
| Survodutide | Glucagon and GLP-1 receptors (a dual agonist) | No FDA approval. |
| Cagrilintide | Amylin receptors; not a GLP-1 receptor agonist | No FDA approval, alone or in combination; studied together with semaglutide. |
Two of these are often compared with the approved medicines; see semaglutide vs tirzepatide and tirzepatide vs retatrutide.
Sources: Drugs@FDA (no approval for retatrutide, mazdutide, survodutide or cagrilintide); Jastreboff et al., N Engl J Med 2023 (PMID 37366315); Innovent Biologics announcement on HKEX, 27 June 2025; each compound guide’s regulatory section. Read 22 October to 1 November 2026.
GLP-1 peptides sold for research
Search results for “GLP-1 peptides” mix the approved medicines with compounds sold as research chemicals. They are not the same thing. An approved medicine is a specific product, made and tested under an FDA approval, with a label. A compound sold for research use only is labelled not for human use, and retatrutide, mazdutide and survodutide have no FDA approval at all. Our pages on what research peptides are and whether peptides are legal set out what regulators have said, record by record.
Medibact does not manufacture or sell peptides. We supply USP-grade bacteriostatic water, made in the USA, for research use only, and publish reference material like this page.
Where this sits in the rest of the reference
FAQ
What is GLP-1?
GLP-1, glucagon-like peptide-1, is a peptide hormone made mainly by L cells in the intestine. It is cut from a precursor called proglucagon; the active forms are GLP-1(7-37), 31 amino acids long, and GLP-1(7-36) amide, 30 amino acids long. The U.S. National Library of Medicine’s MeSH vocabulary records that GLP-1 enhances glucose-dependent insulin release, suppresses glucagon release and gastric emptying, lowers blood glucose and reduces food intake.
What are GLP-1 peptides?
The phrase is used for two things: the natural hormone GLP-1, and the peptide medicines built to act on its receptor, called GLP-1 receptor agonists. Exenatide, liraglutide, dulaglutide, lixisenatide, semaglutide and tirzepatide are all peptides. The phrase is also used for unapproved compounds sold as research chemicals, which are not the same as the approved medicines.
Is semaglutide a peptide?
Yes. U.S. labels describe semaglutide as a GLP-1 analogue with 94% sequence homology to human GLP-1, with its peptide backbone produced by yeast fermentation. Two changes make it last: position 8 is modified to resist the enzyme DPP-4, and a fatty di-acid on lysine 26 binds it to albumin in the blood. Its elimination half-life is about one week.
Is tirzepatide a GLP-1 peptide?
It is a peptide that acts on the GLP-1 receptor, but it is not built on GLP-1. Its U.S. label says tirzepatide is based on the sequence of GIP, another gut hormone, and activates both the GIP and the GLP-1 receptors. That is why it is described as a dual agonist rather than a GLP-1 analogue.
Are all GLP-1 medicines peptides?
No. Orforglipron (Foundayo), approved by FDA on 1 April 2026, is a GLP-1 receptor agonist that is a small synthetic molecule with a molecular weight of about 902, not a chain of amino acids. Every earlier U.S.-approved GLP-1 medicine on this page, from exenatide in 2005 to tirzepatide in 2022, is a peptide.
Why does natural GLP-1 not last long in the body?
Because enzymes break it down within minutes. U.S. labels for liraglutide state that endogenous GLP-1 has a half-life of 1.5 to 2 minutes, due to the enzymes dipeptidyl peptidase-4 (DPP-4) and neutral endopeptidase. The medicines are engineered against this: an amino-acid change at the DPP-4 cut site, a fatty acid that binds albumin, or fusion to part of an antibody.
What is the difference between GLP-1 and GIP?
Both are incretins, gut hormones that increase insulin release after a meal. GLP-1 comes from proglucagon and is about 30 amino acids in its active form; GIP, gastric inhibitory polypeptide, is about 43 amino acids according to MeSH. Tirzepatide acts on both receptors, and retatrutide, still investigational, adds the glucagon receptor.
Are research GLP-1 peptides the same as the approved medicines?
No. The approved medicines are specific products made and tested under an FDA approval. Retatrutide, mazdutide and survodutide have no FDA approval, and a product sold for research use only is labelled not for human use. Our pages on research peptides and on peptide legality set out what regulators have said.
Is this medical advice?
No. This page explains what GLP-1 peptides are, from public scientific and regulatory sources. It gives no dose, schedule, protocol or recommendation, and peptides sold for research are labelled research use only, not for human use. Medibact supplies USP-grade bacteriostatic water, made in the USA, and is not affiliated with any manufacturer of the products named here.
References: NLM MeSH descriptors D052216, D052336, D054795, D000067757, D000097789 and D005749; UniProt P01275; U.S. labels via openFDA for Byetta, Victoza, Saxenda, Trulicity, Soliqua 100/33, Ozempic, Rybelsus, Wegovy, Mounjaro, Zepbound and Foundayo; Drugs@FDA approval records; PubMed 37366315. Read 1 November 2026.
Educational use only — not medical advice. This guide summarizes information reported in published research and community practice for educational purposes. It is not medical advice and not a recommendation to use any compound. Any doses, schedules, or combinations shown are examples of what has been reported, not instructions for you. Many peptides described here are research compounds that are not FDA-approved for the uses discussed and may be investigational or restricted. Effects, risks, and legal status vary; individual needs and results vary. Consult a qualified, licensed healthcare professional before making any decision. Do not use this content to diagnose, treat, or dose yourself.