What Is Ipamorelin? The Peptide Explained

The gist

What is ipamorelin peptide? It is a synthetic chain of five amino acids — a pentapeptide — built to do one job: make the pituitary gland release growth hormone. It does that by binding the ghrelin receptor (GHS-R1a), the docking point the body's hunger hormone normally uses ^[1].

Where did it come from? The drug company Novo Nordisk made it in the 1990s, with the code NNC 26-0161 ^[1]. It was the first peptide of its kind to release growth hormone cleanly — without dragging up the stress hormone cortisol ^[1].

Is it a medicine? No. It was tested in one human efficacy trial, for slow bowel recovery after surgery, and that trial failed ^[3]. It was never approved anywhere. Today it exists as a research chemical. "Research-grade" is not the same as a finished, quality-checked drug — purity varies by supplier.

The molecule

Ipamorelin is the pentapeptide Aib-His-D-2-Nal-D-Phe-Lys-NH2. Position 1 carries alpha-aminoisobutyric acid (Aib), a non-natural amino acid; D-2-naphthylalanine and D-phenylalanine sit in the chain. Those unusual residues resist enzyme breakdown, which is how a five-residue peptide survives long enough to act.

It was derived from GHRP-1 by removing the central Ala-Trp dipeptide ^[1]. Formula C38H49N9O5; molecular weight about 711.9 Da; CAS 170851-70-4. Synonyms include NNC 26-0161 and ipamorelin acetate.

It is wholly synthetic — not a human peptide. It works by imitating endogenous ghrelin at the GHS-R1a receptor.

The class

Ipamorelin is a growth hormone secretagogue (GHS) — specifically a growth-hormone-releasing peptide (GHRP) that acts on the ghrelin receptor. Its siblings are GHRP-2 and GHRP-6.

This class is distinct from the GHRH analogs (sermorelin, CJC-1295, tesamorelin), which mimic growth-hormone-releasing hormone and act on a different receptor. GHRP and GHRH analog are two separate keys to the same GH lock — which is why they are studied in combination.

Within its own class, ipamorelin is the selective one: it releases GH without the cortisol and prolactin rise that the older GHRPs carry ^[1].

Is ipamorelin fda approved

No. Ipamorelin is not FDA-approved for any indication ^[3]. It was investigated — most notably for postoperative ileus (NCT00672074) — but the trial missed its primary endpoint and no approval followed ^[3].

In 2024 the regulatory door narrowed further: the FDA removed ipamorelin acetate from Category 2 of the interim Section 503A bulk-substances list, and the Pharmacy Compounding Advisory Committee reviewed it at the October 29, 2024 meeting. It is not an approved bulk substance for compounding. It is marketed only as a research chemical, and it is prohibited in sport (WADA category S2).

What it is not

Ipamorelin is not the CJC-1295 + ipamorelin blend. This site reads pure ipamorelin. The popular combination pairs ipamorelin with CJC-1295, a GHRH analog; that combination has never been tested as a product in a controlled human trial. Any claim about the blend rests on the separate single-agent pharmacology of its two parts, not on a trial of the mixture.

It is also not an approved anti-aging therapy, a fat-loss drug, or a sanctioned performance aid. Those are marketing frames. What the literature supports is a selective GH-releasing mechanism and a body of mostly short, mostly animal data — set out, cited, on the Ipamorelin research page.