Short answer: Ipamorelin is a synthetic pentapeptide developed in the 1990s as a selective agonist of the growth hormone secretagogue receptor (GHS-R1a, also known as the ghrelin receptor). It is used in receptor pharmacology research, particularly in studies of how selectivity differs across secretagogue compounds. Its sequence includes non-standard amino acids, which affects how identity and purity are established analytically.
Background
Ipamorelin was developed by Novo Nordisk and first described in the scientific literature in 1998. It belongs to the growth hormone secretagogue family, a group of synthetic peptides and small molecules that act at GHS-R1a, the receptor later identified as the target of the endogenous hormone ghrelin. Ipamorelin was characterised as notably selective for this receptor compared with earlier secretagogues, and that selectivity is the main reason it appears in receptor research today.
Structure
Ipamorelin is a pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. Three features matter for laboratory work:
Aib (α-aminoisobutyric acid): a non-proteinogenic amino acid at the N-terminus.
D-amino acids: D-2-naphthylalanine and D-phenylalanine, rather than the L-forms found in natural proteins.
C-terminal amide: the C-terminus is amidated rather than a free acid.
Its molecular formula is C38H49N9O5, with a molecular weight of roughly 712 g/mol (monoisotopic mass approximately 711.4 Da).
Receptor Selectivity in Research
In published receptor studies, ipamorelin acted as an agonist at GHS-R1a with high selectivity relative to several earlier secretagogue compounds. This makes it useful as a comparison compound in experiments examining how structurally different secretagogues engage the same receptor, and how downstream signalling differs between them.
These are findings from laboratory and preclinical research models. They do not establish any effect outside those models.
Analytical Identity
Mass spectrometry is the usual identity technique for ipamorelin. A useful certificate of analysis reports both the expected and measured mass, so a reader can compare the two. Because the C-terminal amide and the free acid differ by roughly 1 Da, the expected value should state which form was tested.
The non-standard residues also matter. Standard amino-acid analysis is built around proteinogenic amino acids, so Aib and D-2-naphthylalanine need appropriate reference standards to be quantified. Amino-acid analysis can support composition, but it cannot distinguish D- from L-forms or establish residue order. Where stereochemistry is relevant, chiral methods provide that evidence.
Purity
Purity is typically reported as an RP-HPLC area percentage. The figure is only meaningful alongside the method: column, gradient, detection wavelength and the laboratory that ran it. Synthesis-related impurities for a peptide like ipamorelin may include deletion sequences and diastereomers, where one residue has the wrong stereochemistry. Diastereomers can be difficult to separate, so whether a method resolves them depends on the method itself.
Net Peptide Content and Counterion
Ipamorelin is commonly supplied as an acetate salt. The gross weight of material in a vial includes peptide, counterion and residual water. Net peptide content states how much of that weight is the peptide itself, and the counterion should be confirmed from the batch documentation rather than assumed.
Storage Documentation
Ipamorelin is usually supplied lyophilised. Dry-state stability information should come from the batch-specific documentation supplied with the material. Solution stability may differ from dry-state stability and can depend on the solvent, container material, temperature and study conditions, so laboratories should rely on their validated internal procedures.
Regulatory Status
Ipamorelin is not a component of an FDA-approved drug. Research-use labeling does not constitute FDA approval or establish that a supplier's distribution is lawful. Legal status depends on the product's intended use, marketing, distribution and the applicable regulations.
FAQs
Is ipamorelin the same as ghrelin?
No. Ghrelin is an endogenous 28-amino-acid hormone. Ipamorelin is a synthetic five-residue peptide that acts at the same receptor.
Why does ipamorelin contain D-amino acids?
D-amino acids and other non-standard residues are common in synthetic peptide design, where they change how a peptide interacts with its receptor and with enzymes. For analysis, they mean that stereochemistry may need to be confirmed separately from mass.
What should an ipamorelin certificate of analysis report?
Identity by mass spectrometry with expected and measured mass, purity by RP-HPLC with the method named, net peptide content where available, and a lot number that matches the vial.
Research use only: Ipamorelin and all products referenced in this article are supplied for laboratory research use only. They are not intended for human or animal use, and nothing in this article describes or recommends any such use.
