GLP-1 peptides: an overview
GLP-1 peptides are among the most studied molecules of recent years. But what is GLP-1 exactly, and how do semaglutide, tirzepatide and retatrutide differ? This overview explains the hormone, the generations of agonists and their status.
What is GLP-1?
GLP-1 (glucagon-like peptide-1) is a hormone released by L-cells in the gut after eating. It is an incretin: a hormone that boosts insulin release from the pancreas depending on blood sugar.
Natural GLP-1 is broken down in the blood within minutes by the enzyme DPP-4, which is why synthetic versions that stay stable much longer were developed.
Three generations of agonists
The well-known peptides can be grouped by how many receptors they activate:
- Mono-agonist: semaglutide – activates only the GLP-1 receptor
- Dual agonist: tirzepatide – activates the GIP and GLP-1 receptors
- Triple agonist: retatrutide – activates the GIP, GLP-1 and glucagon receptors
Shared design
All three are peptides of 31 to 39 amino acids carrying a fatty-acid side chain that binds albumin in the blood. They are therefore broken down slowly, and one dose a week is enough in clinical studies. In the lab, that albumin binding means the protein content of the assay medium can affect the measured potency.
Approval status
Semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) are approved medicines in the EU and available only on prescription. Retatrutide is not yet approved; it is in phase 3 and a marketing application is not expected before 2027.
Virexa Labs does not sell semaglutide. We supply retatrutide and tirzepatide solely as research reagents for in-vitro laboratory research, not for human or veterinary use.
Further reading
For more detail, see our articles 'What is retatrutide?', 'What is tirzepatide?', 'Retatrutide vs tirzepatide' and 'Retatrutide studies'. For related research on energy metabolism we also offer MOTS-c, NAD+ and 5-Amino-1MQ.
Products
Frequently asked questions
What is a GLP-1 peptide?
A peptide that activates the GLP-1 receptor, like the body's own hormone GLP-1. Well-known examples are semaglutide, tirzepatide and retatrutide.
What is the difference between semaglutide, tirzepatide and retatrutide?
Semaglutide activates one receptor (GLP-1), tirzepatide two (GIP and GLP-1) and retatrutide three (GIP, GLP-1 and glucagon).
Is retatrutide approved?
No. Retatrutide is in phase 3 and not approved as a medicine anywhere.
Does Virexa Labs sell semaglutide?
No. Virexa Labs offers retatrutide and tirzepatide solely as research reagents for laboratory research.