Ipamorelin and CJC-1295: what the research models measure

Research-use notice: this article is for legitimate laboratory and educational research only. It does not provide guidance for human use, administration, dosing or treatment.

Ipamorelin and CJC-1295 are two different peptides that act on two different receptors in the same system, and the published record on each is small, old and mostly unflattering to the claims made for them. Ipamorelin was taken into clinical trials for a surgical complication and did not meet its primary endpoint. CJC-1295 reached a phase 2 trial in HIV-associated lipodystrophy, and dosing was halted in 2006 after a participant died. Neither is a licensed medicine anywhere, and no published study has tested the two together. This article sets out what each molecule is, what the research models measure, and where the evidence stops.

What is ipamorelin?

Ipamorelin is a synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH₂, with a mass of about 711 Da. It was developed at Novo Nordisk in the 1990s as a growth-hormone secretagogue: a molecule that binds the receptor later identified as the ghrelin receptor, GHS-R1a. The founding paper is Raun and colleagues, 1998, in the European Journal of Endocrinology, which reported receptor binding in pituitary membranes, GH release from primary rat pituitary cells, and GH responses in anaesthetised rats and conscious swine.

Its selling point in that paper was selectivity. Ipamorelin released GH with a potency and efficacy similar to the older peptide GHRP-6, but it did not raise ACTH or cortisol above the levels seen after GHRH stimulation, even at doses 200-fold higher than those needed for GH release, and it left FSH, LH, prolactin and TSH unchanged. That is the basis for the paper’s title claim that ipamorelin was the first selective growth hormone secretagogue.

What is CJC-1295?

CJC-1295 is a 29-amino-acid analogue of the first 29 residues of growth-hormone-releasing hormone, GRF(1–29), with four substitutions to resist enzymatic breakdown and a lysine-linked maleimidopropionic acid group at the C-terminus. That group is the Drug Affinity Complex, or DAC. After administration the maleimide reacts with the free thiol on Cys34 of serum albumin, so the peptide circulates attached to albumin and is cleared slowly. The chemistry and rodent pharmacology were described by Jetté and colleagues in Endocrinology in 2005.

“CJC-1295 no DAC” is a trade name for the same tetrasubstituted GRF(1–29) without the albumin-binding group. It is a different molecule with a half-life measured in minutes rather than days, and much of the published CJC-1295 pharmacology does not apply to it. Our CJC-1295 DAC vs no DAC article covers the naming problem in detail.

What the research models measure

Because the two peptides act on different receptors with different time courses, they are studied with different designs, and reading a paper means knowing which design was used.

Receptor-binding assays

The simplest model. Membranes from pituitary tissue or from cells expressing the cloned receptor are incubated with a radiolabelled ligand, and the test peptide competes for binding. The output is an affinity value. It tells you the peptide binds, and how tightly, and nothing about what happens downstream in an animal. The 1998 ipamorelin paper and the 2005 CJC-1295 paper both start here.

Pituitary cell culture

Dispersed rat pituitary cells release GH into the medium when stimulated, and the amount released over a few hours is measured by immunoassay. This is where selectivity is assessed: whether ACTH, prolactin or other hormones change alongside GH. It is a sensitive model and an artificial one, with no feedback from the rest of the body. Jetté and colleagues used the same model to show that their albumin conjugates survived dipeptidyl peptidase-IV and remained bioactive.

Rodent and pig studies: pulsatile vs sustained signals

GH is normally released in pulses, and the pattern matters as much as the amount. A short-acting molecule such as ipamorelin or modified GRF(1–29) produces a brief GH pulse, so the studies sample blood every few minutes for an hour or two. A long-acting molecule such as CJC-1295 produces a sustained elevation of GH and of its downstream marker IGF-1, so the studies sample daily or weekly. Jetté 2005 reported a GH response in rats about fourfold greater than that of unmodified GRF(1–29), with the conjugate still detectable in circulation beyond 72 hours. These are different experiments answering different questions, and a result from one design cannot be converted into the other.

What is not studied

There is no published study, in any model, of ipamorelin and CJC-1295 given together, and no published study of ipamorelin with modified GRF(1–29). Any statement about what the combination does is an inference from single-compound work.

The human evidence, in full

Ipamorelin

Gobburu and colleagues published a pharmacokinetic and pharmacodynamic study in healthy men in 1999: five escalating 15-minute infusion rates, with eight subjects at each level. The kinetics were dose-proportional, the terminal half-life was about two hours, and every dose level produced a single episode of GH release peaking at about 40 minutes and then declining to negligible concentrations.

Novo Nordisk later licensed the compound to Helsinn, which ran a clinical programme for postoperative ileus, the slowing of the gut that follows abdominal surgery. The phase 2 trial in patients after small or large bowel resection, published by Beck and colleagues in the International Journal of Colorectal Disease in 2014, enrolled 117 patients and analysed 114. Median time to first tolerated solid meal, the key efficacy endpoint, was 25.3 hours in the ipamorelin arm against 32.6 hours on placebo, a difference that did not reach statistical significance (p = 0.15). A second and larger phase 2 trial, NCT01280344, is recorded as completed with no results published. The programme did not progress.

On 29 October 2024 the US Food and Drug Administration’s Pharmacy Compounding Advisory Committee reviewed ipamorelin and voted against adding it to the list of bulk substances that pharmacies may use in compounding under section 503A. For both the free base and the acetate salt the vote was none in favour, 12 against and one abstention.

CJC-1295

Teichman and colleagues published two randomised, placebo-controlled, double-blind studies in healthy adults aged 21 to 61 in the Journal of Clinical Endocrinology and Metabolism in 2006, covering single and repeated administration. The estimated half-life was 5.8 to 8.1 days. After a single injection, mean plasma GH rose two- to tenfold for six days or more and mean IGF-1 rose 1.5- to threefold for nine to eleven days; after repeated doses IGF-1 remained raised for as long as 28 days. Ionescu and Frohman, in the same journal that year, showed that the GH pulse pattern was preserved rather than flattened.

In July 2006 the developer, ConjuChem, suspended dosing in its phase 2 trial of CJC-1295 in HIV-associated lipodystrophy after a participant died at a study site in Argentina. The company said at the time that the cause of death, and any relationship to the study drug, were under investigation. The programme did not resume, ConjuChem did not take CJC-1295 further, and no later human studies have been published.

The compounding committee reviewed CJC-1295 at a separate meeting, on 4 December 2024, and voted against all five nominated forms, from the free base through to the DAC trifluoroacetate salt. Neither peptide is named on the FDA’s list of bulk substances with identified safety risks, and neither sits on the 503A list.

That is the whole human record: one dose-ranging study in healthy men and one phase 2 trial that missed its endpoint for ipamorelin, and two healthy-volunteer studies and a halted programme for CJC-1295. None of it concerns the combination, and none of it was designed to assess long-term safety.

What this means for a research design

• Name the molecule exactly. “CJC-1295” in a paper almost always means the DAC form. If a batch is modified GRF(1–29), the 2005 and 2006 pharmacokinetics do not apply, and the sampling design has to change accordingly.
• Match the sampling to the half-life. Minute-scale sampling for short-acting peptides, day-scale for DAC. A single time point tells you little about either.
• Keep the arms separate. Because the combination has never been studied, a design that includes it needs single-compound arms and a vehicle control, or it cannot attribute anything to either peptide.
• Confirm identity by mass spectrometry. The DAC and no-DAC forms differ by about 280 Da: the DAC form carries an extra lysine residue and a maleimidopropionyl group, giving about 3,647 Da against about 3,368 Da. That gap is unmistakable by MS and easy to miss on HPLC retention alone. See HPLC vs mass spectrometry.

How to check an ipamorelin or CJC-1295 batch

For either peptide, read the batch laboratory report for:

• The batch number matching the vial label.
• Identity by mass spectrometry: about 711 Da for ipamorelin; about 3,368 Da for modified GRF(1–29); about 3,647 Da for CJC-1295 with DAC. A report that does not distinguish the last two has not identified the material.
• Purity as an HPLC area percentage, read as a separation result rather than a statement of content.
• Method, date and report reference so the result can be verified with the laboratory.

For the general method, see How to read a peptide COA, What does 99% purity actually mean? and our batch report lookup.

Are ipamorelin and CJC-1295 legal in the UK?

Neither has a UK marketing authorisation as a medicine, and neither is a controlled drug under the Misuse of Drugs Act 1971. Both are supplied as research materials for laboratory use. Presentation matters: in April 2026 the MHRA said that where clinics make medicinal claims for peptide injections, those products will be treated as medicines under the Human Medicines Regulations 2012.

In sport, both are prohibited at all times. The World Anti-Doping Agency’s 2026 Prohibited List names each of them at S2.2.4, growth hormone releasing factors: CJC-1295 appears as an example of a GHRH analogue, alongside CJC-1293, sermorelin and tesamorelin, and ipamorelin as an example of a growth hormone secretagogue, alongside anamorelin, ibutamoren and macimorelin. The section also covers substances of similar chemical structure or similar biological effect, so modified GRF(1–29) falls under it even though it is not listed by name.

This section is general information, not legal advice.

Storage and handling

Both peptides are supplied as lyophilised powders in sealed vials. Keep them sealed, dry and protected from heat and light. CJC-1295 with DAC carries a reactive maleimide group, which is the working part of the molecule: it is designed to react with a thiol. Keep it dry and away from thiol-containing reagents such as dithiothreitol or 2-mercaptoethanol until it is used, and note that the maleimide also hydrolyses in water to a form that will no longer conjugate. See our peptide storage guide and the reconstitution method article.

Ipamorelin and CJC-1295 FAQs

Are ipamorelin and CJC-1295 the same kind of peptide?

No. Ipamorelin is a five-residue ghrelin-receptor agonist. CJC-1295 is a 29-residue GHRH analogue. They act on different receptors on the same cell type.

Has the combination been studied?

No. There is no published study of the two together in cells, animals or people.

Did either reach the market as a medicine?

No. Ipamorelin’s phase 2 trial for postoperative ileus, published in 2014, found no significant difference from placebo on its key endpoint. CJC-1295’s phase 2 programme was halted in 2006. Neither is licensed anywhere.

Is “CJC-1295 no DAC” the same as CJC-1295?

No. It is modified GRF(1–29), without the albumin-binding group. It clears in minutes rather than days, and the CJC-1295 pharmacokinetic papers do not describe it.

Are they banned in sport?

Yes. Both are named on WADA’s 2026 Prohibited List at S2.2.4, growth hormone releasing factors, and are prohibited at all times, in and out of competition.

Sources

• Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552–561. Receptor binding, primary rat pituitary cells, anaesthetised rats and conscious swine; no ACTH or cortisol rise above GHRH at 200-fold the GH-releasing dose.
• Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research. 1999;16(9):1412–1416. Five infusion rates, eight healthy men each; terminal half-life 2 hours.
• Beck DE, Sweeney WB, McCarter MD. Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. International Journal of Colorectal Disease. 2014;29(12):1527–1534. 117 enrolled, 114 analysed; 25.3 vs 32.6 hours, p = 0.15.
• ClinicalTrials.gov. NCT00672074 (the trial reported by Beck and colleagues) and NCT01280344: ipamorelin for recovery of gastrointestinal function after bowel resection, sponsored by Helsinn Therapeutics.
• Jetté L, Léger R, Thibaudeau K, et al. Human growth hormone-releasing factor (hGRF)1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: identification of CJC-1295 as a long-lasting GRF analog. Endocrinology. 2005;146(7):3052–3058. Conjugation to Cys34 of albumin; rats only.
• Teichman SL, Neale A, Lawrence B, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology and Metabolism. 2006;91(3):799–805. Estimated half-life 5.8–8.1 days.
• Ionescu M, Frohman LA. Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. Journal of Clinical Endocrinology and Metabolism. 2006;91(12):4792–4797.
• aidsmap. Lipodystrophy study halted after patient death. July 2006. The ConjuChem CJC-1295 halt; cause of death stated as under investigation.
• FierceBiotech. ConjuChem shares dive on study death. 13 July 2006. Dosing halted; the participant died at a site in Argentina.
• US Food and Drug Administration, Pharmacy Compounding Advisory Committee. Transcript, 29 October 2024 meeting. Ipamorelin free base and ipamorelin acetate: 0 yes, 12 no, 1 abstention.
• US Food and Drug Administration, Pharmacy Compounding Advisory Committee. Transcript, 4 December 2024 meeting. All five CJC-1295 forms voted against inclusion.
• US Food and Drug Administration. Safety risks associated with certain bulk drug substances nominated for use in compounding. Neither ipamorelin nor CJC-1295 is listed.
• World Anti-Doping Agency. Prohibited List 2026. S2.2.4, growth hormone releasing factors: CJC-1295 among GHRH analogues, ipamorelin among GH secretagogues.
• Aesthetics Journal. MHRA investigates clinics following peptide claims. 15 April 2026.

Published by Thistle BioLabs, a UK supplier of research materials. This article summarises external research, not studies conducted by Thistle. Educational information only; no medical advice or recommendation for personal use.