Tesamorelin is a synthetic analogue of the full 44-residue human growth hormone-releasing hormone in which the N-terminal tyrosine carries a trans-3-hexenoyl group — a single lipophilic modification designed to blunt dipeptidyl peptidase-4 cleavage while preserving receptor recognition. At 5135.86 g/mol it is the largest GHRH-family peptide in this catalogue and roughly 1.5 times the mass of sermorelin. It is also the only GHRH analogue here with a full regulatory approval behind it: tesamorelin acetate is an FDA-approved prescription medicine, marketed under the Egrifta name, and that approval defines how it must be described.
This page covers the chemistry of the modification, the receptor mechanism, the clinical and preclinical literature, and the laboratory handling of the research-grade material. Tesamorelin supplied here is research-grade peptide for in-vitro and preclinical work only, and is not the approved pharmaceutical product.
Tesamorelin at a glance
| Property | Value |
|---|---|
| Chemical identity | trans-3-hexenoyl-GHRH (1–44) amide analogue |
| Length | 44 residues, full-length GHRH backbone |
| Modification | trans-3-hexenoyl group on the N-terminal tyrosine |
| CAS number | 218949-48-5 |
| Molecular formula | C221H366N72O67S |
| Molecular weight | 5135.86 g/mol |
| Receptor | GHRH receptor (GHRHR), class B GPCR on pituitary somatotrophs |
| Signalling | Gs → adenylyl cyclase → cyclic AMP → protein kinase A |
| Regulatory status of the drug | Prescription-only; FDA-approved as tesamorelin acetate (2010) |
| Sizes supplied (research grade) | 5 mg, 10 mg, 20 mg lyophilized vials |
| Purity specification | ≥99% by RP-HPLC with lot-matched COA |
Origin and structure: one acyl group, one problem solved
Native GHRH is a 44-residue hypothalamic peptide whose great weakness as a pharmacological agent is its N-terminus. Dipeptidyl peptidase-4 clips the first two residues rapidly, and because the N-terminal region is exactly what engages the transmembrane core of the receptor, the truncated product is essentially inactive. Every stabilised GHRH analogue on the market is an answer to this one problem, and they differ mainly in how they answer it.
Sermorelin does not answer it at all — it is unmodified GHRH (1–29) amide and is cleared in minutes. Modified GRF 1-29, sold as CJC-1295 without DAC, substitutes the residue at position 2 so that DPP-4 no longer recognises the site. Tesamorelin takes a third route: it leaves the sequence intact but attaches a six-carbon unsaturated acyl chain, trans-3-hexenoyl, to the alpha-amino group of tyrosine 1. Blocking that amine removes the free N-terminus that the peptidase requires, while the modification is small enough not to obstruct receptor engagement.
Retaining the full 44-residue backbone rather than truncating to 1–29 is a deliberate difference from most analogues. The practical consequences are a longer and more expensive synthesis and a molecule with more residues that can degrade, but the sequence remains the native one throughout.
How tesamorelin is thought to work
The mechanism is straightforward GHRH receptor agonism. Binding to the GHRH receptor on pituitary somatotrophs activates Gs, raising cyclic AMP and activating protein kinase A, which increases growth hormone gene transcription and release. Because the hypothalamic-pituitary axis remains intact, somatostatin tone continues to oppose secretion and IGF-1 feedback stays operative — the resulting secretion pattern is an amplification of an existing rhythm rather than a replacement of it. That is the pharmacological distinction between a GHRH analogue and recombinant growth hormone, which bypasses the axis entirely and is a separate, prescription-only class of product.
The downstream biology most examined for tesamorelin concerns adipose tissue, and specifically visceral adipose tissue, where growth hormone signalling is associated with lipolysis. The reason this molecule became a medicine at all is that visceral fat accumulation proved responsive in a population where it was a defined clinical problem.
What research has examined
Human clinical trials
Tesamorelin has a genuine phase 3 record, unusual among peptides in a research catalogue. Randomised placebo-controlled trials in people living with HIV who had lipodystrophy with excess visceral adipose tissue reported reductions in visceral adipose tissue measured by CT, with associated changes in lipid parameters and IGF-1. On that basis tesamorelin acetate received FDA approval in 2010 for reduction of excess abdominal fat in HIV-associated lipodystrophy, and it remains a prescription-only medicine. Later investigator-led studies have examined it in other contexts, including hepatic fat in HIV-associated fatty liver.
These data describe an approved pharmaceutical product administered under medical supervision. They are not evidence about research-grade peptide, and no part of that clinical record transfers to material sold for laboratory use.
Preclinical endocrine work
In cell and animal systems tesamorelin is used as a stable, well-characterised GHRH receptor agonist — a comparator against which shorter or less stable analogues are measured, and a tool for studying sustained receptor engagement without the minute-scale clearance of native GHRH.
Adipose and metabolic models
Animal work has examined lipolysis, adipose depot distribution and hepatic lipid handling, drawing on the clinical observations that motivated the drug's development. Our longer piece on the HIV lipodystrophy trials sets out that history in more detail.
Combination pharmacology
Because GHRH receptor and growth hormone secretagogue receptor agonists act on the same cell through different second messengers, combinations are a recurring research design. Pre-blended research material such as tesamorelin with ipamorelin exists for that purpose; whether combined signalling is more than additive remains an open question in published work.
Forms and sizes we supply
Research-grade tesamorelin is stocked as a lyophilized powder in 5 mg (USD 85), 10 mg (USD 145) and 20 mg (USD 225) sealed vials. The molar arithmetic is worth noting: at 5135.86 g/mol, a 5 mg vial contains only about 0.97 micromoles, roughly two-thirds the molar content of a 5 mg sermorelin vial. Mass-for-mass comparisons between GHRH analogues are therefore misleading, and molar matching is the correct basis for a structure-activity experiment. The family sits under GHRH analogs. The approved prescription product is listed separately as a prescription reference and is not sold as research material.
Reconstitution and storage in a laboratory context
The calculation: a 10 mg vial reconstituted with 2 mL of bacteriostatic water gives 5 mg/mL, equivalently 5,000 mcg/mL; 0.1 mL (10 units on a U-100 syringe) contains 500 mcg. In molar terms, 5 mg/mL of a 5135.86 g/mol peptide is approximately 973 micromolar — slightly under 1 mM, a convenient reference point for planning serial dilutions down to the nanomolar concentrations used in receptor assays.
Handling follows the general rules for a long, partly hydrophobic peptide. Add diluent slowly down the vial wall, swirl rather than shake, and allow full dissolution before use; the acyl chain increases surface activity, so agitation is more likely to cause foaming and aggregation than with short hydrophilic peptides. The methionine in the sequence is oxidation-sensitive, so stock solutions are protected from air and light. Lyophilized vials are stored at −20 °C or colder, protected from moisture; reconstituted material is aliquoted and kept cold. Detail is in the peptide storage guide.
Purity, COA and how to read one
Each lot is purified by reversed-phase HPLC to at least 99% with mass confirmation and a lot-matched certificate. For tesamorelin two checks carry most of the weight. First, the acyl group is the molecule: the observed mass should match 5135.86 g/mol, and unmodified GHRH (1–44) would appear roughly 96 Da lighter. A mass consistent with the unacylated peptide means the material is not tesamorelin, whatever the label says. Second, resolution matters more at 44 residues than at 7 or 15. Deletion sequences differing by one residue are the characteristic impurity of long syntheses and can elute close to the target, so a symmetrical single peak on a well-resolved chromatogram is the evidence that supports the headline number. Our COA reading guide covers how to assess both.
Regulatory status
Tesamorelin acetate is a prescription-only medicine approved by the FDA in 2010 for reduction of excess abdominal fat in HIV-associated lipodystrophy. Prescription products are manufactured to pharmaceutical standards, supplied through regulated channels and used under medical supervision. The research-grade peptide supplied here is a different thing entirely: it is research use only, intended for in-vitro and preclinical laboratory investigation by qualified researchers, and is not for human or veterinary administration. Clinical trial results obtained with the approved product do not transfer to research material.
Related peptides and further reading
For a direct structural and pharmacokinetic comparison with the shortest member of the family, see tesamorelin vs sermorelin. Modified GRF 1-29 and CJC-1295 with DAC represent two further stabilisation strategies at the same receptor, while ipamorelin and the GHRPs act at the growth hormone secretagogue receptor instead. Broader context sits in the growth hormone and IGF axis hub.