The molecule
What Is Ipamorelin? The Peptide Explained
A wholly synthetic pentapeptide — five amino acids engineered into the first selective growth hormone secretagogue.
In plain English
So what is ipamorelin peptide, really? It is a man-made molecule built from just five amino acids — the small building blocks that link together to form every peptide and protein. Strung together in a specific order (Aib-His-D-2-Nal-D-Phe-Lys-NH2), those five pieces make a compound that does one precise thing: it tells the pituitary gland to release a pulse of growth hormone [1]. It is not something the human body makes on its own; it is wholly synthetic, designed in a lab to copy the action of ghrelin, the body's natural hunger-and-growth signal. What set it apart from earlier molecules like it is precision — it triggers growth hormone without dragging along the stress hormones that older versions did [1]. It has never been an approved medicine, and it is sold only as a research chemical. The sections below cover its structure, where it came from, and its regulatory status.
The structure: five amino acids, engineered for the job
Ipamorelin is a synthetic pentapeptide — a chain of five amino acids — with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2 [1]. Two design choices make it robust: it opens with Aib (alpha-aminoisobutyric acid, a non-natural amino acid that resists enzyme breakdown), and it uses D-form amino acids (D-2-naphthylalanine and D-phenylalanine) that the body's proteases struggle to chew up. It was derived from the earlier peptide GHRP-1 by removing a central dipeptide. Chemically it carries the molecular formula C38H49N9O5, a molecular weight near 712 daltons, and the CAS number 170851-70-4; it also goes by the development code NNC 26-0161 and the name ipamorelin acetate in its salt form. None of that is trivia for its own sake — the engineered backbone is why it survives long enough in the body to deliver its clean GH pulse [1].
Where it came from
Ipamorelin was discovered and developed by a major pharmaceutical company in the 1990s and characterized in a landmark 1998 paper as "the first selective growth hormone secretagogue" [1] — the first peptide able to release growth hormone potently while leaving cortisol and prolactin essentially untouched. Its human pharmacokinetics were mapped the following year, in 1999 [2]. It was later advanced toward a single clinical indication, postoperative ileus (slow bowel recovery after surgery), which became the only use to reach a Phase 2 trial [3]. That is the arc: an elegant molecule with a genuinely novel selectivity profile, a brief and ultimately unsuccessful run at the clinic, and a long afterlife as a research compound.
Is ipamorelin fda approved
No. Ipamorelin is not FDA approved for any indication, and it has never been approved as a drug by any regulatory authority anywhere in the world [3]. It was investigated — most notably for postoperative ileus (NCT00672074) — but that Phase 2 trial missed its primary endpoint, and no Phase 3 program followed [3]. In 2024, U.S. regulators went a step further on the compounding side: the FDA removed ipamorelin acetate from Category 2 of the interim Section 503A bulk drug substances list following the nominator's withdrawal, and reviewed ipamorelin at the October 29, 2024 Pharmacy Compounding Advisory Committee meeting — so it is not an approved bulk substance for pharmacy compounding either. It is marketed strictly as a research chemical, and it is also prohibited in sport at all times under the WADA category S2.
Ipamorelin is not the CJC-1295 blend
One clarification matters, because it is a constant source of online confusion: ipamorelin on its own is a single molecule, and it is not the same thing as the popular "CJC-1295 + ipamorelin" blend. CJC-1295 is a separate peptide — a GHRH analog acting on the GHRH receptor — and ipamorelin is a GHS-R1a (ghrelin-receptor) agonist acting on a different receptor entirely [1]. The blend pairs the two; this site is about ipamorelin by itself. The selectivity data, the human pharmacokinetics, and the failed Phase 2 trial covered across this digest all describe ipamorelin as a single agent [3], and any time the combination comes up here it is clearly labeled as a pairing of two distinct peptides whose joint use has never been tested in a controlled trial.
Research grade is not a drug product
A point worth making plainly: "research-grade ipamorelin" and "an approved ipamorelin medicine" are not the same thing, because the second does not exist. Material sold for research use comes from unregulated suppliers without pharmaceutical quality assurance — its purity, peptide identity, and sterility are unverified [3]. This digest exists to summarize what the published science actually shows about the molecule, not to point anyone toward a product; the word "online" in this site's name refers to where you are reading, not to anything for sale. Everything here is editorial commentary on the literature, with each figure carried back to Ipamorelin references.