Molecular Structure Explorer
Ipamorelin
Structure of the compound covered in this guide.
Last reviewed: October 2026 · Cleared Peptides research team
Research use only. Ipamorelin: Research Guide to the Selective GHS-R Agonist is supplied for laboratory research. It is not a drug, food, cosmetic, or dietary supplement. It is not FDA-approved. It is not for human or veterinary administration. This page does not give a dose or a method of administration. A study cited on this page describes that study’s own test article. It does not make this lot an approved medicine. To check a fact, open the PubMed or DOI link, confirm the authors and year, and match the paper’s compound name, CAS number, or sequence to the specification table. The full method is on the research desk page. Identity and purity for a lot are only what that lot’s certificate of analysis reports. An HPLC percentage is not a sterility result and not an endotoxin result unless the certificate prints those tests.
Ipamorelin (NNC 26-0161) is a synthetic pentapeptide described in 1998 as a selective agonist of the growth-hormone secretagogue receptor (GHS-R1a), the receptor for ghrelin. It is a reference ligand in GHS-R binding and signaling research.
In this guide:
Ipamorelin Structure and Identifiers
| Name | Ipamorelin |
|---|---|
| Code | NNC 26-0161 |
| CAS number | 170851-70-4 |
| PubChem CID | 9831659 |
| Molecular formula | C38H49N9O5 |
| Molecular weight | ≈711.9 g/mol |
| Sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH2 |
| Form | Lyophilized powder |
Receptor Pharmacology
Ipamorelin belongs to the growth-hormone-releasing peptide (GHRP) family but was designed for greater receptor selectivity than earlier GHRPs such as GHRP-6. It contains non-coded residues — α-aminoisobutyric acid (Aib) and D-2-naphthylalanine — that increase stability and receptor affinity. In research it is used to study GHS-R1a activation, Gq/calcium signaling and receptor desensitization.
Ipamorelin vs GHRH Analogs
| Ipamorelin | Tesamorelin | |
|---|---|---|
| Receptor | GHS-R1a (ghrelin receptor) | GHRH receptor |
| Length | 5 residues | 44 residues |
| CAS | 170851-70-4 | 218949-48-5 |
| Product | Ipamorelin | Tesamorelin |
Because the two act through different receptors, they are commonly compared in receptor-pharmacology studies. This summary describes laboratory research only and makes no claim about effects in humans or animals.
Research materials referenced in this guide
Analytical testing notes for Ipamorelin
Ipamorelin is identified in this guide as CAS 170851-70-4, formula C38H49N9O5, listed mass ≈711.9 g/mol. The sequence recorded here is Aib-His-D-2-Nal-D-Phe-Lys-NH2. An identity test compares a measurement with those values. A mass spectrum is the usual measurement for a peptide. FTIR, when a certificate uses it, is a supporting infrared fingerprint and is less specific for closely related sequences.
For Ipamorelin, routine chemical characterization is reversed-phase HPLC for area-percent purity and mass spectrometry for identity against the formula and mass in the table above. Oxidizable residues (cysteine, methionine, tryptophan) and deamidating residues (asparagine, glutamine), when the sequence contains them, are typical related-impurity questions for the chromatogram and the mass spectrum.
HPLC purity for this material is an area-percent result at the wavelength and gradient the laboratory states, commonly ultraviolet detection near 214 nm on a reversed-phase column. The instrument is a gradient pump, injector, column oven, and UV or diode-array detector. That percentage is not the number of milligrams in the vial. Water, acetate, trifluoroacetate, and other UV-silent material can dominate the gross weight while the purity figure stays high. Net peptide content, from an assay or amino-acid analysis, is the separate result to read when the certificate reports it.
A sterility test and an endotoxin test are not included in a chemical purity result. The compendial sterility test is a culture method (USP <71>): membrane filtration or direct inoculation into fluid thioglycollate medium and soybean-casein digest medium, incubated for 14 days. A PCR sterility screen uses a thermal cycler to detect microbial DNA and is a different method. The endotoxin test (USP <85> LAL, or USP <86> recombinant Factor C) reports endotoxin units with an incubating reader or a cartridge reader. Use a result only when that method is printed on the lot certificate. One published example in this catalog states that the report does not cover microbial contamination or endotoxins. The full description of equipment, standards, and how US laboratory accreditation works is in peptide analytical testing. Lot records are on the COA page.
Frequently Asked Questions
What receptor does ipamorelin act on?
Ipamorelin is characterized as a selective agonist of GHS-R1a, the ghrelin receptor.
What is the CAS number of ipamorelin?
170851-70-4; molecular formula C38H49N9O5.
Is ipamorelin for human use?
No. It is supplied for laboratory research use only.
Written by the Cleared Peptides Research Desk, the editorial desk of Cleared Wellness Group LLC. This is not a personal profile of a physician or a scientist, and it is not a fictional author. The checking method is public on the research desk page. Last reviewed October 2026.
Ipamorelin research note: a pentapeptide secretagogue, not a GHRH analogue
Research use only. This ipamorelin material is for laboratory research, code NNC 26-0161, CAS 170851-70-4. It is not for human or veterinary administration. The cell-assay numbers below are the paper’s numbers. They are not a dose.
What Raun and colleagues measured
Raun, Hansen, Johansen, and colleagues (European Journal of Endocrinology, 1998) describe ipamorelin as the pentapeptide Aib-His-D-2-Nal-D-Phe-Lys-NH2, selected from a series that removed the central Ala-Trp dipeptide of GHRP-1. In primary rat pituitary cells they report growth-hormone release with EC50 1.3 ± 0.4 nmol/L and Emax 85 ± 5 percent, close to GHRP-6 in that assay (2.2 ± 0.3 nmol/L, Emax 100 percent). Antagonist experiments in the paper place the activity on a GHRP-like receptor, which is the ghrelin-receptor pathway, not the GHRH receptor. The title’s word “selective” is their claim from a hormone panel in the models they ran. A reader should look at that panel in the paper rather than treat the adjective as a new measurement. They also report growth-hormone release in pentobarbital-anaesthetized rats. That is an animal pharmacology result. PubMed 9849822, DOI 10.1530/eje.0.1390552.
The catalog table matches the sequence, formula C38H49N9O5, mass about 711.9 g/mol. Aib and D-2-naphthylalanine are not proteinogenic. An identity method that assumes twenty standard amino acids will mis-assign the mass. Stereochemistry at the D residues is part of the specification.
Why tesamorelin is the wrong comparison compound to merge with it
Tesamorelin is a 44-residue analogue of growth hormone-releasing hormone. Falutz’s trial studied that analogue as a drug. Ipamorelin is five residues and, in Raun’s antagonist experiments, uses the GHRP receptor. Both conversations are about growth hormone. The receptors are different, the masses are different (about 711.9 versus about 5135.9), and the papers are not interchangeable. There is also no basis on this site for mixing ipamorelin with MOTS-c or tesamorelin and citing either paper for the mixture.
How to verify this note
- Open Raun 1998 and confirm the sequence and the 1.3 nmol/L EC50 in rat pituitary cells. Leave that number in the assay.
- Match CAS 170851-70-4. A GHRP-6 mass is not an ipamorelin mass, even though the paper uses GHRP-6 as the comparator.
- Lot identity stays on the certificate.
Selected References
Peer-reviewed literature on the compounds discussed in this guide, listed as scientific background for laboratory researchers. Citation does not imply endorsement by the authors or any use other than in-vitro research.
- Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-61. PubMed 9849822 · DOI
- Ankersen M, et al. A new series of highly potent growth hormone-releasing peptides derived from ipamorelin. J Med Chem. 1998;41(19):3699-704. PubMed 9733495 · DOI
Laboratory note: solubility depends on salt form and solvent. This guide does not state a single solubility figure. Handling of lyophilized material is described in the peptide storage guide.
Research Use Only Notice
This guide is provided for educational and laboratory reference purposes. It summarizes published, primarily in-vitro and structural research literature and does not describe, recommend or imply any use in humans or animals. Products sold by Cleared Peptides are for laboratory research use only; they are not drugs, foods, cosmetics or dietary supplements, are not FDA-approved, and are not intended to diagnose, treat, cure, mitigate or prevent any disease. No dosing, administration or therapeutic information is provided.
