Chemical identity
| Designation | Tirzepatide |
|---|---|
| CAS number | 2023788-19-2 |
| Molecular formula | C225H348N48O68 |
| Molecular weight | 4813 g/mol |
| Chain | 39 amino acids, with a C20 fatty diacid and Aib substitution |
| Cartridge strength | 60 mg per cartridge |
| Concentration | 20 mg/ml |
| Presentation | Pre-mixed solution, sealed 3 ml cartridge |
| Storage | 2–8 °C, protect from light, do not freeze |
Identifiers verified against PubChem in both directions — name to compound record, then each CAS number back again — and, where the sequence is of standard residues, cross-checked by recomputing the molecular weight from the sequence. No purity, HPLC or certificate-of-analysis figure is stated, because no supplier data supports one.
What tirzepatide is
Tirzepatide is a synthetic peptide of thirty-nine amino acids that acts as an agonist at two receptors: the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor. An agonist binds a receptor and activates it, initiating the same class of signalling the receptor's natural ligand would.
Its backbone is built on the GIP sequence rather than the GLP-1 one, which is a detail worth holding onto: tirzepatide is a GIP analogue engineered to also be tolerated at the GLP-1 receptor, not a GLP-1 analogue with GIP activity bolted on. The two native hormones are related members of one peptide family with conserved segments in common, and that shared ancestry is what makes a single engineered chain capable of activating both.
Two structural features are doing most of the work. The chain incorporates α-aminoisobutyric acid, a non-natural residue, at positions that would otherwise present a cleavage site to dipeptidyl peptidase-4 — the enzyme that inactivates native GIP and GLP-1 within minutes. And a C20 fatty diacid chain is attached partway along the sequence, which allows the molecule to bind reversibly to serum albumin. Neither change alters what the molecule recognises; both change how long it persists.
What “dual agonist” describes, and what it does not
Dual agonist refers to coverage of two receptors and to nothing else. It does not describe a two-part construction: tirzepatide is a single continuous chain, not two linked fragments, and there is no sense in which one half is the GIP portion and the other the GLP-1 portion.
Critically, the label says nothing about relative potency. A molecule can be an agonist at two receptors while being far more active at one than the other, and the balance between them is a property of the specific sequence rather than something implied by the category. Comparing two dual agonists on the strength of the label alone tells you nothing about how they differ.
The same caution applies when comparing across categories. Retatrutide is a triple agonist, adding the glucagon receptor to the same two — that is a difference in receptor coverage, not evidence of greater potency at either shared receptor. Cagrilintide sits outside this family altogether, acting at the amylin and calcitonin receptors rather than the incretin receptors. The retatrutide and tirzepatide comparison sets out what actually separates the two.
What is studied in vitro
Work on molecules in this class is largely receptor pharmacology. A candidate sequence is run against cells expressing one receptor at a time, and the readout is the downstream signal — cyclic AMP accumulation for these receptors — measured across a concentration range. That produces a potency figure per receptor, and the ratio between the figures characterises the molecule's balance.
Related questions follow from the same setup: whether the molecule biases signalling toward one intracellular pathway over another at the same receptor, how quickly the receptor is internalised after activation, and how stable the peptide is when incubated with enzyme preparations or in serum. Structure–activity work compares a series of sequences differing at one position against the same panel, which is how the contribution of an individual residue is established.
All of that is in-vitro and cell-based work. It is a different activity from clinical investigation.
Regulatory status in the UK
Tirzepatide is unusual among the compounds covered in these guides in that it is the active ingredient of authorised medicines, in the United Kingdom and elsewhere. That fact needs stating precisely, because it is easily misread.
A marketing authorisation attaches to a specific finished product, made to a specific specification by a specific manufacturer, for specific indications. It does not attach to the molecule, and it does not extend to research-grade tirzepatide supplied by anyone else. Research material of an authorised molecule is not an authorised medicine, is not manufactured or released under a medicines framework, and carries none of the documentation that authorisation implies — no Qualified Person batch release, no monograph assessment, no patient information leaflet, no pharmacovigilance route.
Common questions
What is tirzepatide?
A synthetic 39-amino-acid peptide that acts as an agonist at both the GIP and the GLP-1 receptor. Its backbone derives from the GIP sequence, and it carries a non-natural residue that resists DPP-4 cleavage together with a C20 fatty diacid chain that lets it bind reversibly to albumin.
Is tirzepatide a GLP-1 or a GIP peptide?
Both, in the sense that it activates both receptors — but its backbone is built on GIP. It is a GIP analogue engineered to also be tolerated at the GLP-1 receptor rather than a modified GLP-1. The label "dual agonist" describes receptor coverage only and implies nothing about relative potency at either.
How is tirzepatide different from retatrutide?
Receptor coverage. Retatrutide adds the glucagon receptor to the same GLP-1 and GIP pair, making it a triple agonist; tirzepatide covers two. That is a difference in which receptors are activated, not evidence of greater potency at the shared ones. The comparison guide goes into what else separates them.
Is research-grade tirzepatide the same as a licensed medicine?
No. A marketing authorisation attaches to a specific finished product from a specific manufacturer, not to the molecule. Research material of an authorised compound is not an authorised medicine and carries none of the documentation that authorisation implies.
Is tirzepatide legal in the UK?
Tirzepatide is the active ingredient of medicines authorised in the UK, so the molecule is not a prohibited substance. But an authorisation attaches to a specific finished product from a specific manufacturer, not to a molecule — research-grade tirzepatide is not that product and is not a medicine. Nothing here is legal advice.
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