What ipamorelin is
Ipamorelin is a synthetic pentapeptide that acts as a selective agonist at the growth hormone secretagogue receptor (GHS-R1a), the receptor for endogenous ghrelin. Its sequence — Aib-His-D-2-Nal-D-Phe-Lys-NH₂ — contains three non-proteinogenic residues and a C-terminal amide, and at roughly 712 Da it is one of the smallest peptides in routine research use.
Its defining property is selectivity. The first generation of growth hormone secretagogues activated GHS-R1a but carried a substantial off-target profile: appetite signalling, cortisol, prolactin. Ipamorelin was developed specifically to separate the growth hormone secretagogue activity from that profile, and its continued use as a research tool follows from that separation.
Molecular profile
| Property | Value |
|---|---|
| Development code | NNC 26-0161 |
| CAS number | 170851-70-4 |
| Sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH₂ |
| Molecular formula | C38H49N9O5 |
| Molecular weight | ~711.9 Da |
| Receptor target | GHS-R1a (ghrelin receptor) |
| Appearance | White lyophilised powder |
Non-standard residues and why they are there
Three of the five residues are unusual, and each is doing specific work:
- Aib (2-aminoisobutyric acid) — a doubly methylated alanine that constrains backbone conformation, favouring the shape the receptor recognises.
- D-2-naphthylalanine and D-phenylalanine — D-configuration amino acids that proteases evolved on L-peptides do not efficiently cleave.
- C-terminal amide — removes the free carboxyl terminus, closing off carboxypeptidase degradation.
A five-residue L-peptide would be degraded almost immediately. These modifications are what make a molecule this small viable at all.
Research context
Ipamorelin is used in growth hormone axis research as a selective GHS-R1a probe: receptor binding and selectivity assays, calcium mobilisation and inositol phosphate accumulation as functional readouts, and pituitary cell models examining growth hormone release. It is frequently paired with a GHRH receptor agonist such as CJC-1295, since the two engage different receptors within the same regulatory axis, allowing the contributions to be separated.
Supplied for in-vitro laboratory research only. No therapeutic claim is made and no dosing or administration guidance is provided.
Analytical notes
Ipamorelin's small size makes it comparatively straightforward to characterise — mass confirmation is unambiguous, and impurities separate more cleanly than they do for a 40-residue peptide.
The analytical question that does arise is stereochemical. Two of the five residues are D-amino acids, and a synthesis that incorporates the L-form at either position produces a diastereomer with an identical molecular mass. Mass spectrometry cannot detect this. Chromatography can, because diastereomers have different retention times — but only if the method resolves them and the analyst is looking. It is a good illustration of why a purity figure and an identity figure together are still not the same thing as a chromatogram someone has examined. See reading an HPLC chromatogram.
Handling and storage
Store sealed at −20 °C, protected from light and moisture, and bring to room temperature before opening. Reconstitute by running diluent down the vial wall and swirling gently. Small peptides tolerate handling better than large ones, but the practice costs nothing. Store solution at 2–8 °C, protected from light.
What we supply
Released against a ≥99% purity specification, with HPLC purity and mass spectrometry identity confirmation on every batch and a batch-specific Certificate of Analysis. Select batches additionally receive independent third-party purity verification.