Ipamorelin

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Snapshot

Chemistry and make-up

A short 5-residue peptide carrying three non-proteinogenic building blocks: an N-terminal Aib (2-aminoisobutyric acid, a gem-dimethyl glycine), a D-2-naphthylalanine, and a D-phenylalanine, finished with a C-terminal amide rather than a free acid [A]. Those choices are deliberate. The D-amino acids at positions 3 and 4 and the Aib cap block the aminopeptidases and other proteases that would otherwise clip a natural L-peptide quickly, which is why a molecule this small still has a usable serum half-life of roughly two hours [A][D]. The C-terminal amide removes the terminal negative charge and further slows carboxypeptidase attack.

There is no cysteine, so no disulfide bridge, and no metal binding. It is normally supplied as the acetate salt of the amidated peptide. Because the free-base amide sits at ~711.9 and the acetate adds counterion mass, a CoA that just says “Ipamorelin, 99%” without stating salt form and observed mass is under-specified. The non-natural residues (Aib, 2-Nal) are also the identity features a mass-spec identity check should confirm, since cheaper or mislabelled material could substitute a plain Phe or drop the amide.

What it is studied for (evidence)

• Mechanism [A]: Ipamorelin is a ghrelin-receptor (GHS-R1a) agonist. It binds the same pituitary receptor as the natural hormone ghrelin and, via a Gq / phospholipase-C / intracellular-calcium pathway, triggers the somatotroph cells of the anterior pituitary to release a pulse of growth hormone (Raun et al., Eur J Endocrinol 1998). This is a different receptor from the one GHRH analogues (like tesamorelin) use, which is why the two classes act synergistically and are so often stacked (see the CJC-1295 note below).
• Established (good evidence): In the original preclinical and early human pharmacology work, ipamorelin was notable as the first GHS with GHRH-like selectivity: it raised GH cleanly without the dose-dependent spikes in ACTH, cortisol, prolactin or aldosterone that dog older GHRPs such as GHRP-6 and GHRP-2, even at doses far above the GH-releasing threshold [A]. That selectivity, and its preservation of the natural pulsatile GH pattern, are its best-supported properties. The dose-response is bell-shaped.
• Emerging / thin / preclinical only: Beyond acute GH/IGF-1 pharmacology, clinical outcome data are sparse. It reached Phase II (developed by Novo Nordisk, later Helsinn) for postoperative ileus and was discontinued for lack of efficacy [A][D]. There is no completed, published outcome trial for body composition, recovery, “anti-aging”, bone or the other uses vendors imply.
• Marketing claims vs data: Vendor and blend pages routinely imply fat loss, lean-mass gain, better sleep, injury recovery and anti-aging. None of these is established for ipamorelin in a controlled human efficacy trial. What is real is a transient rise in GH and downstream IGF-1; the leap from “raises GH acutely” to “changes body composition or heals tissue in humans” is unsupported extrapolation. Treat any dosing protocol on these pages as outside our scope and not evidence.
• Human clinical status: No approval anywhere, for any indication. Development halted at Phase II.

Handling, format and stability

Supplied lyophilised as a white powder, typically as the acetate salt, and reconstituted with water for research handling only (no dosing or human-use guidance here). Store the lyophilised powder cold and protected from light; reconstituted peptide is markedly less stable and is cold-chain dependent, with the amide and D-residues giving good resistance to enzymatic breakdown but not to hydrolysis or oxidation in solution over time. When sold as a CJC-1295 + ipamorelin blend, the two peptides are co-lyophilised in one vial, which means a single CoA has to characterise both actives and their ratio, a common gap in market CoAs.

Regulatory and trade status

• UK / EU RUO: Research use only; not an authorised medicine. Because it has no marketing authorisation, any listing or email that describes human benefits (fat loss, recovery, anti-aging) risks pulling it into “medicinal product by presentation” territory under UK medicines law. Keep all copy strictly RUO.
• US: Not FDA-approved. Ipamorelin is among the peptides FDA has treated unfavourably for pharmacy compounding (the broader GHS/peptide compounding crackdown); it is not a lawful active in approved drugs.
• WADA (sport): Prohibited at all times under S2.2 (Growth Hormone, its fragments and releasing factors) as a growth hormone secretagogue / ghrelin-receptor agonist mimetic. Ipamorelin is named explicitly in the 2026 List alongside anamorelin, capromorelin, ibutamoren (MK-677), lenomorelin (ghrelin), macimorelin and tabimorelin [B]. The class heading also prohibits “other substances with a similar chemical structure or similar biological effect”, so analogues are caught too [B]. Athletes should treat it as banned in and out of competition.
• Customs: Lower profile than the GLP-1 class, but as an unapproved GHS it can attract scrutiny; the main trade risk is identity/labelling rather than scheduling.

Sources

• [A] Raun K. et al., “Ipamorelin, the first selective growth hormone secretagogue”, *Eur J Endocrinol* 1998 — https://scispace.com/pdf/ipamorelin-the-first-selective-growth-hormone-secretagogue-1t1xkfpaeo.pdf
• [B] WADA Prohibited List, S2.2 Peptide Hormones / GH secretagogues (drugs.com WADA mirror) — https://www.drugs.com/wada/s2-peptide-hormones-growth-factors-and-related-substances.html
• [B] WADA Prohibited List (official) — https://www.wada-ama.org/en/prohibited-list
• [B] PubChem CID 9831659 (formula C38H49N9O5, MW 711.9) — https://pubchem.ncbi.nlm.nih.gov/compound/9831659
• [D] ChemicalBook, Ipamorelin CAS 170851-70-4 (identity/dev history NNC 26-0161, Phase II ileus discontinued) — https://www.chemicalbook.com/ChemicalProductProperty_EN_CB41117534.htm
• [D] Vendor blend pages (Core Peptides, Midwest Peptide, Nationwide Peptides) — commercial; used for format/blend norms only, not for efficacy — https://www.corepeptides.com/peptides/cjc-1295-ipamorelin-10mg-blend/

Plain summary

Ipamorelin is a tiny 5-amino-acid peptide that makes the pituitary release a clean pulse of growth hormone by acting on the ghrelin receptor, and its claim to fame is doing that without raising cortisol or prolactin the way older peptides did. It never became a medicine (drug development stopped at Phase II for lack of effect) and no human trial supports the fat-loss, muscle or anti-aging claims vendors make, so it is strictly research-use-only and is banned in sport (WADA S2). Commercially the main traps are that it is usually sold blended with CJC-1295, so the CoA must characterise both peptides and the ratio, and that its identity rests on non-natural residues and a C-terminal amide a proper mass-spec check should confirm.

For laboratory and research use only (RUO). Not for human or veterinary use, not for consumption, and not a medicine. Information is a research summary, not medical advice, and contains no dosing guidance.

For laboratory research use only. Not for human or veterinary use, not for consumption, and not a medicine. This is a research summary, not medical advice, and contains no dosing guidance.