Ipamorelin

What Ipamorelin Is

Ipamorelin is a synthetic pentapeptide (five amino acids, with the reported sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2) developed at Novo Nordisk and first described in the scientific literature by Raun and colleagues in the European Journal of Endocrinology in 1998. That paper introduced it as the first selective growth hormone (GH) secretagogue. It was engineered from the earlier growth hormone-releasing peptide GHRP-1 by removing a central dipeptide, a modification that preserved GH-releasing potency while markedly improving receptor selectivity. Ipamorelin is a research-stage compound; it is not an approved medicine and has no established human therapeutic use.

Mechanism of Action

In published research, ipamorelin acts as an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), the G-protein-coupled receptor in the anterior pituitary and hypothalamus that also binds the endogenous hormone ghrelin. Activation of this receptor in preclinical models stimulates the release of stored GH from pituitary somatotrophs, generating a pulsatile GH signal rather than a flat, sustained elevation. The 1998 Raun et al. characterization emphasized that ipamorelin released GH with a potency comparable to earlier secretagogues but with far greater selectivity, and reported that even at doses substantially above the GH-effective range it did not meaningfully raise ACTH, cortisol, or prolactin in the animal systems tested. This clean selectivity, particularly the contrast with GHRP-6 which more readily elevates cortisol and prolactin, is the property most consistently cited in later literature.

What Published Research Has Examined

The body of work on ipamorelin is concentrated in two areas. The first is GH-axis pharmacology, where in-vitro and rodent studies characterized potency, receptor selectivity, and effects on GH pulsatility, along with some animal endpoints related to GH-driven bone and body-composition markers. The second is gastrointestinal motility, reflecting the role of the ghrelin/GHS-R pathway in gut function. Greenwood-Van Meerveld and colleagues (Journal of Experimental Pharmacology, 2012) reported that ipamorelin improved gastric dysmotility in a rodent model of postoperative ileus, and this rationale carried into human testing. Beck et al. (International Journal of Colorectal Disease, 2014) ran a Phase 2 proof-of-concept randomized controlled trial in patients undergoing bowel resection. Ipamorelin also appears as a reference or tool compound in broader reviews of ghrelin-receptor agonists.

Key Findings

The central preclinical finding, from Raun et al. 1998, was selective, potent, pulsatile GH release without the off-target endocrine effects seen with earlier peptides. The most substantial human finding comes from the Phase 2 postoperative ileus trial (n=114), in which intravenous ipamorelin administered twice daily for up to seven days was reported as generally well tolerated; however, the study did not meet its primary endpoint. Although some measures such as time to recovery of gastrointestinal function trended in ipamorelin's favor, the trial was not positive overall, and the postoperative ileus development program was subsequently discontinued. As a result, the human evidence base remains limited to early-stage work, and much of what is known about ipamorelin still rests on animal and in-vitro data rather than confirmatory clinical trials.

Regulatory Status

Ipamorelin is not an FDA-approved drug. The FDA-approved peptide medicines relevant to adjacent conversations are finished drugs such as semaglutide, tirzepatide, and bremelanotide, none of which is ipamorelin. Within the Section 503A compounding framework, ipamorelin is best described as Category 2 (may not be compounded pending sufficient safety review) and otherwise unscheduled / research-use-only. Importantly, ipamorelin is NOT among the seven peptides on the FDA Pharmacy Compounding Advisory Committee (PCAC) docket for the July 23-24, 2026 meeting, which covers BPC-157, TB-500 (thymosin beta-4 fragment), KPV, MOTS-c, emideltide, epitalon, and semax. Ipamorelin was handled in a separate PCAC review cycle and did not advance toward the 503A bulks list, so it remains outside that pathway. Any PCAC vote is non-binding and represents only one early step in a multi-step FDA rulemaking process; a favorable vote would still leave a realistic timeline of 12 to 18 months minimum before any legal compounding availability.

Safety Considerations & Related Compounds

No comprehensive long-term human safety profile for ipamorelin exists in the peer-reviewed literature. The largest published human dataset, the Phase 2 postoperative ileus trial, reported that it was generally well tolerated over a short course, with the most common adverse events (nausea, vomiting, dyspepsia) consistent with recent bowel surgery rather than clearly drug-related. Because it acts on the GH axis, the literature notes class-relevant theoretical considerations common to GH secretagogues, such as potential effects on glucose handling, though these were not established as clinical safety signals in the limited trials run. Related compounds discussed in the same research space include other ghrelin-receptor agonists and GH secretagogues such as GHRP-6, GHRP-2 (pralmorelin), and hexarelin, the orally active secretagogue MK-677 (ibutamoren), and GHRH analogs such as sermorelin, CJC-1295, and the FDA-approved tesamorelin. None of this constitutes guidance for human use.

Key published studies

Regulatory status

Current status: Category 2 · under review. Not FDA approved. PepSense tracks FDA filings and updates this record as the regulatory picture changes. See the FDA PCAC tracker for the July 2026 vote and what happens next.

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