Reference
Ipamorelin molecular data
Verified chemical identity for ipamorelin: sequence, molecular formula, weight, CAS and UNII numbers, InChIKey, and measured pharmacokinetics.
By the Ipamorelin Research editorial team · Last reviewed · Scientific review: pending
Short answer
Ipamorelin is the pentapeptide Aib-His-D-2-Nal-D-Phe-Lys-NH2, molecular formula C38H49N9O5, molecular weight 711.9 g/mol, CAS 170851-70-4, PubChem CID 9831659. Its measured half-life in healthy men is about two hours. Three of its five residues are not standard L-amino acids, which is what makes it resistant to ordinary proteolysis.
Interactive structure
The structure below is drawn from PubChem's own atom coordinates for CID 9831659. Residue membership is not hand-assigned: it is derived by cutting the four inter-residue amide bonds in the bond graph and checking each resulting fragment against the composition that residue must have, so a wrong assignment cannot reach this page.
Ipamorelin structure
Two-dimensional structure drawn from PubChem's own atom coordinates. Hover or select a residue to highlight it.
Sequence, N-terminus first
PubChem CID 9831659, 2D depiction (PUG REST SDF), retrieved 2026-11-11
Chemical identity
| Property | Value |
|---|---|
| Amino acid sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH2A pentapeptide. Three of the five residues are not standard L-amino acids: Aib is 2-aminoisobutyric acid, and the naphthylalanine and phenylalanine residues are in the D configuration. The C-terminus is an amide, not a free acid. |
| Molecular formula | C38H49N9O5 |
| Molecular weight | 711.9 g/molThis is the average molecular weight of the free base. Material supplied as the acetate salt has a higher formula weight. |
| Monoisotopic mass | 711.38566570 Da |
| CAS registry number | 170851-70-4 |
| UNII | Y9M3S784Z6 |
| InChIKey | NEHWBYHLYZGBNO-BVEPWEIPSA-N |
| PubChem CID | 9831659 |
| IUPAC name | (2S)-6-amino-2-[[(2R)-2-[[(2R)-2-[[(2S)-2-[(2-amino-2-methylpropanoyl)amino]-3-(1H-imidazol-5-yl)propanoyl]amino]-3-naphthalen-2-ylpropanoyl]amino]-3-phenylpropanoyl]amino]hexanamide |
| Hydrogen bond donors / acceptors | 8 / 8Computed descriptors. Rotatable bonds 19, topological polar surface area 240 Ų, XLogP 1.8. |
Every value above was read from the PubChem record via PUG REST [PubChem], except the UNII, which comes from the FDA Global Substance Registration System [FDA GSRS].
The residues, and why they matter
Ipamorelin is unusual for a peptide of its size in how little of it is conventional. Aib — 2-aminoisobutyric acid — does not occur in ordinary proteins and constrains the shape of the N-terminus. The naphthylalanine and phenylalanine are both in the D configuration rather than the L configuration found in natural peptides. That combination is the reason the molecule survives in circulation long enough to be measured with a two-hour half-life, and it is also precisely what FDA pointed to when it said the unnatural amino acids “add to the complexity of peptide characterisation” [FDA Category 2]. Harder to characterise means harder to confirm that a given sample is what it claims to be — and modified forms carrying an extra N-terminal glycine have been found in market product [Krug 2018].
Measured pharmacokinetics
These are research measurements, reported with the species they were measured in. They are not dosing guidance, and this site publishes none.
| Parameter | Value | Measured in | Source |
|---|---|---|---|
| Terminal half-life | About 2 hoursMeasured across five infusion rates from 4.21 to 140.45 nmol/kg. Pharmacokinetics were dose-proportional. | Healthy human males, intravenous infusion | Gobburu 1999 |
| Clearance | 0.078 L/h/kg | Healthy human males, intravenous infusion | Gobburu 1999 |
| Volume of distribution at steady state | 0.22 L/kg | Healthy human males, intravenous infusion | Gobburu 1999 |
| Time to peak growth hormone | 0.67 hours after the start of infusionA single episode of release at every dose, declining exponentially to negligible concentrations. | Healthy human males, intravenous infusion | Gobburu 1999 |
| Concentration for half-maximal GH stimulation | 214 nmol/L | Healthy human males, intravenous infusion | Gobburu 1999 |
| Systemic plasma clearance relative to GHRP-6 | Five-fold lower than GHRP-6 | Male rats, intravenous bolus | Johansen 1998 |
| Route of excretion | Mainly urinaryGHRP-6 by contrast was excreted predominantly in bile. 60–80% of the administered dose was recovered as intact peptide. | Male rats | Johansen 1998 |
| Nasal bioavailability | Approximately 20%Lower than the roughly 50% estimated for GHRP-2 and two related NNC peptides in the same study. | Male rats, intranasal | Johansen 1998 |
How it compares on size
At 711.9 g/mol and five residues, ipamorelin is small for a peptide of this class. Sermorelin and CJC-1295 are 29-residue GHRH analogues around 3,400 to 3,650 g/mol, and tesamorelin is a 44-residue analogue at about 5,136 g/mol — roughly seven times the mass. GHRP-2 and GHRP-6 are hexapeptides of comparable size to ipamorelin, and act at the same receptor. The compound comparison tool sets these out side by side.
References
- Gobburu JV, Agersø H, Jusko WJ et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. PubMed 10496658 · doi:10.1023/a:1018955126402[Human, grade B]
- Johansen PB, Hansen KT, Andersen JV et al. (1998). Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption. Xenobiotica. PubMed 9879640 · doi:10.1080/004982598238976[Animal, grade C]
- Raun K, Hansen BS, Johansen NL et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. PubMed 9849822 · doi:10.1530/eje.0.1390552[Animal, grade C]
- Krug O, Thomas A, Malerød-Fjeld H et al. (2018). Analysis of new growth promoting black market products. Growth Horm IGF Res. PubMed 29864719 · doi:10.1016/j.ghir.2018.05.001[Analytical, grade D]
- PubChem, National Library of Medicine. Ipamorelin (CID 9831659). Source[retrieved 2026-11-11]
- FDA Global Substance Registration System. IPAMORELIN, UNII Y9M3S784Z6. Source[retrieved 2026-11-11]
- U.S. Food and Drug Administration (2026-04-22). Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Source[retrieved 2026-11-11]