What Is Ipamorelin? Sequence, CAS Number, Receptor Pharmacology and Research Literature
By the Zen Well Labs Research Team · Last reviewed September 2026 · For laboratory research reference only
Short answer: Ipamorelin (development code NNC 26-0161) is a synthetic pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2, molecular formula C38H49N9O5, molecular weight about 711.9 Da and CAS number 170851-70-4. It is a selective agonist of the growth hormone secretagogue receptor (GHSR-1a, the ghrelin receptor) and was first described by Novo Nordisk researchers in 1998. It is not approved by the FDA for any use; Zen Well Labs sells it for in-vitro laboratory research only.
Ipamorelin at a glance
| Common names | Ipamorelin, NNC 26-0161 |
| Type | Synthetic pentapeptide amide containing non-proteinogenic residues |
| Sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH2 |
| Molecular formula | C38H49N9O5 |
| Molecular weight | ≈711.9 Da |
| CAS number | 170851-70-4 |
| PubChem CID | 9831659 |
| Molecular target | GHSR-1a (ghrelin receptor) agonist |
| Typical supplied form | Lyophilized powder |
What makes the structure unusual?
Three of ipamorelin’s five residues are not among the twenty standard amino acids: Aib (2-aminoisobutyric acid), D-2-Nal (D-2-naphthylalanine) and D-Phe (the D-enantiomer of phenylalanine). The C-terminus is an amide rather than a free acid. These features are typical of the growth hormone–releasing peptide (GHRP) family; D-amino acids and Aib make a peptide backbone more resistant to proteases than an all-L sequence would be.
Receptor pharmacology
Ipamorelin binds and activates GHSR-1a, the G-protein-coupled receptor whose endogenous ligand is ghrelin. In the original characterisation, Raun and colleagues (European Journal of Endocrinology, 1998) called it “the first selective growth hormone secretagogue”: in rat pituitary cell assays and in swine, it released growth hormone with potency comparable to GHRP-6, but — unlike GHRP-6 and GHRP-2 — it did not significantly raise ACTH or cortisol, even at doses far above those needed for GH release. That selectivity is the reason it remains a common reference agonist in GHSR research.
Clinical development history
Ipamorelin was later evaluated in clinical trials for postoperative ileus — a gastrointestinal-motility indication connected to ghrelin-receptor biology — but development did not proceed to approval. No ipamorelin product is FDA-approved, and growth hormone secretagogues including ipamorelin are named on the World Anti-Doping Agency Prohibited List.
Ipamorelin and CJC-1295: why they appear together in the literature
The two act on different receptors. Ipamorelin is a GHSR-1a (ghrelin receptor) agonist; CJC-1295 is an analogue of growth hormone–releasing hormone and acts on the GHRH receptor. Because the GHRH and ghrelin pathways converge on pituitary somatotrophs through distinct signalling cascades, researchers studying GH-axis regulation in vitro often examine agonists of both receptors.
Storage and handling
Store lyophilized ipamorelin sealed, dry and dark at −20 °C. After reconstitution for bench work, keep solutions at 2–8 °C, aliquot to avoid freeze–thaw cycles, and rely on your own stability data for working lifetimes. See the storage and stability guide.
Frequently asked questions
What is the sequence of ipamorelin?
Aib-His-D-2-Nal-D-Phe-Lys-NH2 — a pentapeptide amide containing 2-aminoisobutyric acid, D-2-naphthylalanine and D-phenylalanine.
What is the CAS number and molecular weight of ipamorelin?
CAS 170851-70-4; molecular weight approximately 711.9 Da; molecular formula C38H49N9O5.
What receptor does ipamorelin act on?
The growth hormone secretagogue receptor type 1a (GHSR-1a), also known as the ghrelin receptor.
Why is ipamorelin described as selective?
In the original 1998 characterisation it released growth hormone without significantly raising ACTH or cortisol in the animal models tested, unlike earlier peptides such as GHRP-6 and GHRP-2.
Is ipamorelin FDA-approved?
No. Ipamorelin is not approved by the FDA for any use and is on the WADA Prohibited List. Zen Well Labs sells it for in-vitro laboratory research only.
References
- Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552–561.
- PubChem Compound Summary, CID 9831659 (Ipamorelin). National Center for Biotechnology Information.
- World Anti-Doping Agency. Prohibited List, section S2.
Related
Research use only. All products sold by Zen Well Labs are intended strictly for in-vitro laboratory research. They are not drugs, foods, cosmetics or dietary supplements, are not approved by the FDA for any use, and are not for human or veterinary use. Nothing on this page is medical advice, and nothing here describes or recommends administration to humans or animals.
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