Metabolic pathway peptides are among the most actively researched compounds in the world, and the field has moved quickly from single-receptor agonists to molecules that engage two or three receptors at once. For research buyers, the compounds can look similar on paper — long, lipidated synthetic peptides with similar names — but they differ in their targets, structure and the questions they are used to investigate.
This guide compares four incretin- and amylin-pathway compounds side by side. It is written for research and procurement teams and makes no therapeutic claims.
The hormones behind the compounds
Four endogenous hormones frame this class of research:
- GLP-1 (glucagon-like peptide-1) — an incretin hormone released from the gut after eating, acting at the GLP-1 receptor. It is involved in glucose-dependent insulin secretion, gastric emptying and appetite signalling.
- GIP (glucose-dependent insulinotropic polypeptide) — the other major incretin hormone, acting at the GIP receptor.
- Glucagon — a pancreatic hormone acting at the glucagon receptor, involved in hepatic glucose output and energy expenditure.
- Amylin — a pancreatic hormone co-secreted with insulin, involved in satiety signalling and gastric emptying.
The native hormones are broken down within minutes in circulation. Much of the chemistry in the research compounds below is about extending that half-life — most commonly by attaching a fatty diacid chain that binds reversibly to albumin.
At a glance
| Compound | Receptor targets | Structure | Approx. molecular weight |
|---|---|---|---|
| Semaglutide | GLP-1 | 31-amino-acid GLP-1 analogue with a C18 fatty diacid chain | 4113.6 g/mol |
| Tirzepatide | GIP + GLP-1 (dual) | 39-amino-acid peptide on a GIP-based sequence with a C20 fatty diacid moiety | 4813.5 g/mol |
| Retatrutide | GIP + GLP-1 + glucagon (triple) | 39-amino-acid GIP-derived peptide with non-coded residues and a C20 fatty diacid chain | 4731 g/mol |
| Cagrilintide | Amylin (and calcitonin) receptors | Long-acting acylated amylin analogue | 4409 g/mol |
Semaglutide: the single-receptor benchmark
Semaglutide (CAS 910463-68-2) is a GLP-1 receptor agonist and, in many research programmes, the reference compound against which newer molecules are compared. Its sequence is closely based on human GLP-1, with an amino acid substitution that protects it from enzymatic breakdown and a C18 fatty diacid chain attached through a linker for albumin binding. Semaglutide is approved as a medicine in many jurisdictions; the material we supply is research grade and for laboratory use only.
Tirzepatide: dual GIP and GLP-1 agonism
Tirzepatide (CAS 2023788-19-2) is a single 39-amino-acid peptide that acts at both the GIP and GLP-1 receptors. Its sequence is based on GIP, modified so that it also engages the GLP-1 receptor, and it carries a C20 fatty diacid moiety for extended activity. Research interest centres on whether combined incretin signalling produces effects that GLP-1 agonism alone does not. Tirzepatide is also approved as a medicine in many jurisdictions; our material is research grade only.
Retatrutide: adding the glucagon receptor
Retatrutide (LY3437943, CAS 2381089-83-2) extends the multi-agonist idea to three receptors — GIP, GLP-1 and glucagon. Like tirzepatide it is built on a GIP-derived backbone, here with non-coded amino acids (including Aib residues and alpha-methyl-leucine) that tune receptor activity and stability, plus a C20 fatty diacid chain. The rationale for adding glucagon receptor activity is its role in energy expenditure and hepatic metabolism. Retatrutide has been investigational; check its current regulatory status in your jurisdiction.
Cagrilintide: the amylin pathway
Cagrilintide (CAS 1415456-99-3) works on a different axis altogether. It is a long-acting, acylated analogue of amylin that acts at amylin receptors (and, as a non-selective analogue, at calcitonin receptors). Because amylin and GLP-1 signal through distinct pathways, cagrilintide is frequently studied in combination with GLP-1 agonists such as semaglutide.
Where AOD-9604 fits — and where it does not
AOD-9604 often appears alongside these compounds in metabolic research catalogues, including our own weight management range, but it is mechanistically unrelated. It is a modified fragment of human growth hormone (amino acids 176–191), around 1815 g/mol, and does not act on incretin or amylin receptors. It is worth keeping separate when designing comparisons.
Handling considerations for lipidated peptides
All four incretin and amylin compounds above are large, lipidated peptides, which affects how they behave in the lab:
- The fatty acid chains change solubility and can promote adsorption to plastics — use the diluent specified in the product documentation and appropriate low-binding consumables where relevant.
- At over 4,000 g/mol, these peptides are typically handled in milligram vials; our reconstitution guide and calculator help plan concentrations.
- Store lyophilised material cold, dry and dark, and avoid repeated freeze–thaw of solutions — see our storage guide.
- Identity confirmation by mass is particularly useful for compounds this similar in size; our CoA guide explains what to look for.
Sourcing these compounds from Peptide Direct
Semaglutide, tirzepatide, retatrutide, cagrilintide and AOD-9604 are all part of our weight management range. Every batch is manufactured under GMP, verified by HPLC to ≥98% purity and shipped with a batch Certificate of Analysis. Add the compounds you need to a quote list to price them together.
Peptide Direct supplies these compounds strictly for laboratory research. They are not for human consumption, and nothing in this guide is medical advice.