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Terminus Peptides
  • Research use only — not for human or veterinary use
  • 55 compound profiles, every source cited
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Research profile · Peptide

Ipamorelin

Also known as NNC 26-0161

Early human — evidence level 3 of 4: Early human evidenceExperimental — UK regulatory status: Experimental — not authorised for human use in the UK

Overview

A synthetic pentapeptide growth hormone secretagogue whose one controlled human trial did not meet its endpoint.

Category
Peptide
Highest evidence level identified
Early human evidence
Last scientifically reviewed
20 August 2026
Last regulatory review
20 August 2026

Mechanism under investigation

Ipamorelin is a synthetic pentapeptide acting as an agonist at the growth hormone secretagogue receptor, the receptor for the endogenous hormone ghrelin. Binding is proposed to stimulate release of growth hormone from the anterior pituitary. In the originating pharmacology it released growth hormone from primary rat pituitary cells with potency similar to GHRP-6 but, unlike other secretagogues tested, did not significantly raise corticotropin or cortisol. Any downstream effect on body composition in humans is inferred from the growth hormone axis rather than demonstrated.

Research areas

  • Pituitary endocrinology
  • Gastrointestinal motility models

These are fields in which the compound has been investigated. Listing a field is not a statement that anything was demonstrated within it.

Current evidence

In-vitro evidence

Cells, tissues or biochemical systems outside a living organism.

Present. The originating work characterised growth hormone release from primary rat pituitary cells and established receptor selectivity against GHRP-6, which is the compound’s genuine distinguishing feature.

Animal evidence

Studies in living non-human animals.

Present and the strongest tier. Two rodent models of postoperative ileus showed accelerated gastric emptying and reduced time to first bowel movement. Further animal work covers chemotherapy-induced weight loss and visceral nociception.

Human observational evidence

Studies observing people without assigning an intervention.

Essentially absent. No cohort or case-control studies of use for body composition, recovery or ageing were located. The only human-use literature is a single case report of an adverse outcome in a long-term user of growth hormone and a related secretagogue, plus survey material on grey-market peptide use.

Clinical-trial evidence

Studies assigning an intervention to human participants.

One completed randomised, double-blind, placebo-controlled phase 2 trial in 117 patients with postoperative ileus after bowel resection. It did not meet its endpoint — median time to first tolerated meal was 25.3 hours against 32.6 on placebo, which did not reach significance — and the development programme was subsequently discontinued. No controlled human trial exists for any body-composition, muscle-growth or recovery indication, which are the uses the compound is actually sold for.

Study limitations

  • The single human trial was in postoperative ileus, not in any indication for which the compound is now promoted, and its findings cannot be extrapolated to body composition or wellbeing outcomes.
  • That trial failed to show a statistically significant benefit and the programme was discontinued — a negative result frequently omitted from secondary summaries.
  • Rodent ileus models measure gut motility over hours to days and say nothing about chronic administration, endocrine adaptation or long-term safety.
  • No published human study reports outcomes beyond short inpatient exposure, so there is no evidence base at all for repeated or long-term use.

UK regulatory context

Experimental — not authorised for human use in the UK

A compound appearing in research literature that holds no UK authorisation for human use in any indication.

Source: The Human Medicines Regulations 2012, regulation 46 — prohibition on sale or supply of an unauthorised medicinal product (opens legislation.gov.uk in a new tab) (legislation.gov.uk)

Regulatory classification is jurisdiction-specific. A compound authorised elsewhere is not thereby authorised in the UK, and a supplier’s description of a substance does not determine how it is classified in law. See safety and regulation for the framework and the authoritative sources.

Safety and interpretation

In the one controlled human trial adverse events were common in both arms and were not more frequent than placebo, but that trial was short, inpatient-based and conducted under medical supervision in a surgical population. Because no long-term human data exist, the effects of sustained stimulation of the growth hormone axis remain uncharacterised for this compound. Material obtained outside a regulated supply chain carries separate risks of variable identity, purity and sterility.

References