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Peptide profile · Growth hormone secretagogue (ghrelin/GHS-R1a agonist), pentapeptide

Ipamorelin

Also known as: NNC 26-0161, Ipamorelin acetate

A selective ghrelin-receptor agonist that stimulates growth hormone release. Early human studies exist; a post-operative ileus programme was discontinued for lack of efficacy. Not FDA-approved.

Preliminary evidenceNot FDA-approved
Abstract peptide-chain illustration for the ipamorelin profile

Evidence level

Preliminary

Human phase 1 studies confirm GH release; a phase 2 trial in post-operative ileus did not show efficacy and the programme was stopped. No trials of body composition, recovery or aging outcomes.

Regulatory status (US)

Not FDA-approved

Not FDA-approved for any use; development discontinued. Ipamorelin acetate remains in category 2 of the 503B interim compounding policy (added 29 September 2023) and appears on the 503A withdrawn-nomination list, per the FDA list current 22 April 2026. Prohibited in sport by WADA (S2).

Mechanism (proposed)

Activates the ghrelin receptor on pituitary somatotrophs to release growth hormone, with less effect on cortisol and prolactin than earlier GHRPs. Downstream effects on body composition or recovery have not been demonstrated in controlled human trials.

Studied for: GH release (human phase 1), Post-operative ileus (human phase 2, negative), Body composition (marketing; no trials)

Full research analysis

CJC-1295 and Ipamorelin: Growth Hormone Research and Unanswered Risks

The 'CJC/ipa' stack is sold for muscle, fat loss, sleep and anti-aging. The human evidence is a handful of short hormone-level studies, two abandoned development programmes, and no outcome trials — plus a set of risks that have never been studied because the trials were never run.

Read the analysis

What ipamorelin is

Ipamorelin is a synthetic five-amino-acid peptide that stimulates growth hormone release through the ghrelin receptor. It was designed in the 1990s to be more selective than earlier secretagogues — releasing GH without much cortisol or prolactin[1] — and was later studied for post-operative ileus, where a phase 2 trial did not show benefit and development stopped[2].

Where the evidence stands

The controlled human record is short-term pharmacology plus one negative outcome trial in an unrelated indication. Everything it is marketed for today — lean mass, fat loss, sleep, recovery, "anti-aging" — is untested in controlled trials. The common pairing with CJC-1295 has never been studied for any clinical endpoint.

Regulatory position

Not approved; development discontinued. FDA placed it in category 2 of the compounding interim policies in 2023, citing immunogenicity risk for certain routes; on the list current at 22 April 2026 it appears among substances whose nominations were withdrawn by the nominators — a procedural change that does not add it to the 503A bulks list[3]. Prohibited in sport.

Safety summary

Short-term human studies reported tolerability without serious signals. Long-term safety of chronic ghrelin-receptor stimulation and GH/IGF-1 elevation is unstudied. No data on the combination with CJC-1295 that is commonly marketed.

Frequently asked questions

Is ipamorelin FDA-approved?
No. Its development for post-operative ileus was discontinued after a phase 2 trial did not show efficacy. Ipamorelin acetate also remains in category 2 of the FDA's 503B compounding interim policy, added in September 2023 over immunogenicity concerns.
Why is ipamorelin called "selective"?
In animal studies it released growth hormone without the cortisol and prolactin increases seen with earlier secretagogues. That is a pharmacological property, not evidence of any clinical benefit.
Does ipamorelin help with fat loss or muscle?
No controlled human trial has measured either outcome.

References

Numbered in order of first use. Study type is shown for every source; see our methodology for how we rank evidence.

  1. 1.

    Raun K, Hansen BS, Johansen NL, et al.. Ipamorelin, the first selective growth hormone secretagogue European Journal of Endocrinology, 1998.

    Preclinical

    Result: Ipamorelin released GH selectively without significant ACTH/cortisol release in animal models.

    Limitations: Preclinical characterisation only.

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  2. 2.

    Clinical trials of ipamorelin (search) ClinicalTrials.gov.

    Trial registry

    Result: Registered phase 1/2 studies, including post-operative ileus; no registered trials of body composition or aging outcomes.

    ↑ back to text
  3. 3.

    Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (category 2 list) U.S. Food and Drug Administration, 2026.

    Regulatory source

    Result: Ipamorelin acetate remains in category 2 under the 503B interim policy (added 29 September 2023) and also appears on the 503A withdrawn-nomination list. FDA cited immunogenicity risk from aggregation or peptide-related impurities.

    ↑ back to text

Review status: Editorially reviewed against primary sources. This article was fact-checked against the primary sources listed in the references by our editorial team, and it has not been reviewed by a licensed clinician. It is educational content, not medical advice. Read our editorial policy and methodology. Spotted an error? Tell us.

Profile by Tristen Ta. Published August 15, 2026; updated August 15, 2026.

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