Ipamorelin

Ipamorelin was discovered at Novo Nordisk and characterised in 1998 as a pentapeptide in primary rat pituitary cell culture, in anaesthetised rats and in conscious swine, with growth hormone release as the endpoint. Human pharmacology was reported in 1999: a dose-escalation study in healthy male volunteers across five infusion rates from 4.21 to 140.45 nmol/kg over 15 minutes, eight subjects per dose level, measuring plasma ipamorelin and growth hormone concentrations, with a terminal half-life of about 2 hours. Development then moved to a commercial sponsor which ran two completed phase 2 trials in post-operative ileus and gastrointestinal recovery after bowel resection, one of them enrolling 117 participants. The FDA review of that programme records that the published trial showed no significant difference from placebo on the primary and secondary analyses, and that development for that indication was reportedly discontinued as a result.

What is not established

The FDA concluded in 2024 that evidence of effectiveness for growth hormone deficiency or post-operative ileus is limited by any route, and that there are no data at all supporting the subcutaneous route that compounders had proposed. Nothing is established for body composition, recovery, sleep or ageing outcomes in any population.

What distinguishes Ipamorelin

Ipamorelin is the only compound in this group that is a pentapeptide. It was designed by deleting the central Ala-Trp dipeptide from GHRP-1, so it carries five residues where GHRP-2 and GHRP-6 each carry six, and that edit produced a measured selectivity difference rather than a marketing claim: in conscious swine, GHRP-6 and GHRP-2 both raised plasma ACTH and cortisol while ipamorelin did not do so significantly even at doses more than 200-fold above the dose producing half-maximal growth hormone release. It is also the only one of the three secretagogues to have reached a named sponsor's registered phase 2 programme, which was then discontinued.

Sources

1. Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-61
2. Gobburu JV et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin in human volunteers. Pharm Res. 1999;16(9):1412-6
3. ClinicalTrials.gov. NCT00672074, ipamorelin for post-operative ileus, phase 2, completed December 2009
4. US FDA. Briefing document, Pharmacy Compounding Advisory Committee, evaluation of ipamorelin-related bulk drug substances, 29 October 2024
5. US FDA. Certain bulk drug substances for use in compounding that may present significant safety risks

This page describes a compound as a material and summarises published research about it. It is for general and procurement information only. It is not medical advice, not a treatment recommendation, and not guidance on use. Supplied for laboratory and research use, not for human consumption.