Ipamorelin: structure, nomenclature and handling

The sequence is aminoisobutyryl-histidyl-D-2-naphthylalanyl-D-phenylalanyl-lysinamide, conventionally written Aib-His-D-2-Nal-D-Phe-Lys-NH2. Its molecular weight is approximately 712 daltons, and its molecular formula is C38H49N9O5.

Position one is aminoisobutyric acid, usually abbreviated Aib. It is not one of the twenty proteinogenic amino acids: it carries two methyl groups on the alpha carbon rather than a hydrogen and a side chain, which makes it achiral and conformationally restrictive. Residues of this kind constrain the backbone angles a peptide can adopt, favouring particular turn geometries, and they are also poor substrates for aminopeptidases, which expect a conventional amino terminus.

Positions three and four are D-amino acids: D-2-naphthylalanine and D-phenylalanine. Natural proteins are built almost exclusively from L-amino acids, and proteases have evolved to act on that stereochemistry, so inverting a residue at a cleavage-prone position confers resistance. The 2-naphthylalanine side chain is also larger than any natural aromatic residue, extending the phenyl ring of phenylalanine into a fused two-ring system.

The carboxyl terminus is an amide rather than a free acid, written as the -NH2 in the shorthand — a common feature of bioactive peptides, and one that removes the negative charge a free carboxylate would carry at neutral pH.

Ipamorelin is characterized against the growth hormone secretagogue receptor, GHS-R1a, a class A G-protein-coupled receptor. It is described in the literature as selective within that receptor family, which is the property that distinguishes it from earlier compounds of the same class.

Ipamorelin appears under the development code NNC 26-0161 and under CAS 170851-70-4, and as ipamorelin acetate, which is how peptides of this kind are typically isolated and supplied. The salt form affects the mass weighed out but not the identity of the peptide itself.

The generic name follows the -relin stem, used across peptides that act at releasing-hormone or secretagogue receptors. Recognising the stem places an unfamiliar name into the right functional family immediately, though it is worth noting that the stem spans two distinct receptor targets: sermorelin and tesamorelin are analogues of growth hormone-releasing hormone and are characterized against the GHRH receptor, while ipamorelin belongs to the ghrelin-receptor class. Shared stem, different receptor.

Mass spectrometry confirms the intact molecular mass, and for this compound the measurement carries a specific piece of information. If the C-terminal amide failed to form during synthesis, the resulting free-acid impurity is heavier than the target by approximately one dalton — a small difference, but a defined one, and detectable given adequate resolving power. A certificate reporting a mass rounded to whole numbers cannot exclude it.

High-performance liquid chromatography resolves the main peak from related substances and yields the purity figure. The characteristic related substances in a sequence like this one are diastereomers: the D-configured residues at positions three and four can invert during synthesis to the L form, producing compounds of identical molecular mass that mass spectrometry cannot distinguish at all. They are separable chromatographically, which is precisely why the two methods are run in combination rather than either being treated as sufficient on its own.

HEEZ Research supplies ipamorelin in a single format: a 10 mg lyophilized vial. There is no second strength in the current catalogue, so the format decision that arises with two-size products does not apply here.

The material is supplied as a lyophilized powder. Freeze-drying removes water and leaves the peptide as a solid, markedly more stable than the same peptide in solution, and stable enough at ambient temperature to ship without refrigeration in transit.

Reconstitution converts the dried cake into a working solution, and it is a standard laboratory step rather than a product specification. Which solvent is used, and at what final concentration, is determined by the protocol in force at the receiving facility.

What HEEZ specifies is the contents of the vial: lyophilized ipamorelin in a single 10 mg format, stated on the label and on the batch certificate of analysis. Where a protocol is expressed in molar rather than mass terms, the additional figure it needs is the molecular weight, which the certificate records for the batch supplied.

Sealed lyophilized ipamorelin is ambient-stable for the duration of transit, so no cold chain or insulated packaging is required for shipping. On receipt the vial goes to refrigeration and is kept out of direct light.

Reconstituted material is held refrigerated and used within the window the receiving facility's protocols specify, and repeated freeze-thaw cycling is avoided. Solutions are treated as short-lived relative to the lyophilized form.

The sequence contains no cysteine and no methionine, removing the two most common oxidation routes, and no asparagine or glutamine, removing deamidation as a degradation pathway. The residues warranting attention are the aromatic ones — naphthylalanine, phenylalanine and the imidazole of histidine — reason enough to keep solutions out of direct light. It is a robust molecule by peptide standards, though the substitutions that resist enzymatic cleavage do nothing against the physical routes that matter in storage.

The certificate records what an independent facility measured for one specific batch. Its value lies in being batch-specific, so the first check is that the lot number on the document matches the vial in hand.

The identity section compares observed molecular mass against theory. For an amidated peptide the theoretical figure should correspond to the amide, and the resolution of the reported measurement determines whether the free-acid form is excluded or merely unaddressed.

The purity figure is the HPLC main-peak area as a percentage of total peak area, and the attached chromatogram shows how that figure was arrived at. Peaks eluting close to the main peak are the ones to note on this compound, since diastereomers of identical mass separate by small retention differences rather than large ones.

Peptide content, or net peptide content, is sometimes reported separately. It accounts for counter-ions and residual water, and it is the figure determining how much actual peptide a nominal 10 mg represents.