CJC-1295 and Ipamorelin: Distinct Mechanisms in GH-Axis Research

CJC-1295 and ipamorelin are two synthetic peptides studied for their effects on the growth hormone axis through entirely different receptors: CJC-1295 is a long-acting analog of growth hormone-releasing hormone (GHRH) that acts at the GHRH receptor on somatotrophs, while ipamorelin is a pentapeptide agonist at the growth hormone secretagogue receptor (GHS-R1a), the receptor later shown to be the target of the endogenous peptide ghrelin.

Because the two act on separate receptor systems, they are frequently discussed together in the literature and in supplier catalogs. This page compares them on receptor pharmacology, molecular design and published study history. It does not rank them, does not present one as preferable, and does not describe administration to humans or animals.

A naming problem that precedes any comparison

"CJC-1295" is used in commerce for two chemically different molecules, and conflating them makes any comparison meaningless. The compound identified in the peer-reviewed literature is CJC-1295 with a Drug Affinity Complex (DAC): a 30-residue GHRH(1-29) analog bearing a maleimidopropionyl linker that forms a covalent bond with cysteine-34 of circulating serum albumin. Jetté et al. (2005) synthesized several such bioconjugates in rats and identified this tetrasubstituted form as the long-lasting candidate. What is sold as "CJC-1295 without DAC" is a different, shorter molecule — a 29-residue GHRH analog usually catalogued as modified GRF(1-29), carrying four substitutions (D-Ala², Gln⁸, Ala¹⁵, Leu²⁷) that increase resistance to enzymatic cleavage but no albumin-binding element. The DAC form's CAS number is frequently and incorrectly applied to the non-DAC analog in commercial listings. Comparisons on this page refer to the DAC form unless stated otherwise.

Comparative specifications

Receptor pharmacology compared

The two receptors sit at different points in the same regulatory circuit. The GHRH receptor is a class B G protein-coupled receptor expressed on pituitary somatotrophs; agonism raises intracellular cyclic AMP and drives GH transcription and release. GHS-R1a is a class A G protein-coupled receptor identified by Howard et al. (1996) in pituitary and hypothalamus as the target of synthetic growth hormone secretagogues; it signals principally through G_q and phospholipase C. Because the pathways are separate, the two peptide classes are pharmacologically distinct rather than interchangeable.

Research history: CJC-1295

The compound originates from work at ConjuChem on albumin bioconjugation. Jetté et al. (2005) reported in Endocrinology that maleimido derivatives of human GHRH(1-29) conjugated to serum albumin activated the GHRH receptor on the rat anterior pituitary, and identified CJC-1295 as the stable, long-lasting analog, detectable in plasma beyond 72 hours. Teichman et al. (2006) reported two randomized, placebo-controlled, double-blind ascending-dose trials in healthy adults aged 21 to 61, over 28 and 49 days, and described dose-dependent increases in mean plasma GH and IGF-I concentrations sustained over several days. Ionescu and Frohman (2006) addressed a mechanistic question raised by that duration — whether continuous receptor stimulation would flatten the normal pulsatile pattern of GH release — and reported that pulsatility persisted. In a non-human model, Alba et al. (2006) reported that once-daily administration in GHRH-knockout mice maintained body weight and length in the normal range, a genetic-rescue design rather than a performance study.

Research history: ipamorelin

Ipamorelin was developed at Novo Nordisk and characterized by Raun et al. (1998) in the European Journal of Endocrinology, in the paper that named it the first selective growth hormone secretagogue. That work described a pentapeptide with GH-releasing potency in vitro and in vivo, and reported that unlike GHRP-6 and GHRP-2 it did not significantly elevate ACTH or cortisol above what GHRH stimulation produced — the selectivity observation the compound is principally known for. Gobburu et al. (1999) reported pharmacokinetic–pharmacodynamic modeling in healthy male volunteers using an intravenous ascending-infusion design, describing dose-proportional kinetics, a terminal half-life near two hours and a single episode of GH release with an early peak followed by exponential decline. In a rodent model, Svensson et al. (2000) administered ipamorelin or GHRP-6 continuously by osmotic minipump to thirteen-week-old female Sprague-Dawley rats for twelve weeks and reported higher bone mineral content by DXA in treated animals than in vehicle controls. That finding is rat-only; no corresponding human skeletal endpoint has been published.

The combination question

The two peptides are commonly co-marketed as a blend on the rationale that GHRH-receptor and GHS-R1a agonism act through separate pathways. That rationale restates the receptor pharmacology described above, but it remains a hypothesis rather than a published finding: the peer-reviewed record contains no controlled human trial of the specific combination, and the studies cited above examined each compound separately. Statements about what the combination does in humans are not supported by the literature.

What the published record does not establish

Neither compound is the subject of a completed late-phase clinical programme, and neither has published long-term human safety data. Development of both was discontinued as a pharmaceutical programme — CJC-1295 in the mid-2000s, ipamorelin after later clinical evaluation — and the peer-reviewed literature does not comprehensively document the reasons in either case. Reported effects on GH and IGF-I concentrations are biomarker observations, not clinical outcomes. Where the record is thin, it is thin.

Regulatory status

Neither CJC-1295 nor ipamorelin is approved by the FDA or any comparable authority for any indication. Neither is a dietary supplement ingredient. Both are supplied strictly for in vitro and laboratory research, not for human or animal consumption, under the terms set out in the research use policy.

Identity, purity and documentation

The two molecules differ by roughly 2,900 daltons, so mass spectrometry separates them and separates either from the non-DAC GHRH analog discussed above without ambiguity. A certificate of analysis should name the analytical methods, report reversed-phase HPLC purity with the chromatogram, and give a mass-spectrometric identity confirmation against the expected monoisotopic or average mass. Documentation practice for material supplied here is described under lab testing.

Handling and storage

Lyophilized peptide is generally held at −20 °C, desiccated and shielded from light, with freeze–thaw cycling minimized. Laboratory reconstitution technique is covered in how to reconstitute peptides and container and temperature considerations in peptide storage. Because the molecular weights differ by a factor of roughly five, molar concentration calculations must use the correct value for each; the peptide calculator handles that conversion.

Frequently asked questions

What is the difference between CJC-1295 with DAC and without DAC?

They are different molecules. The DAC form carries a maleimidopropionyl linker that covalently binds serum albumin and is the form described in the published literature. The non-DAC form is a shorter GHRH analog usually catalogued as modified GRF(1-29), with stabilizing substitutions but no albumin-binding element. Catalog listings often apply the DAC form's CAS number to both.

How should these peptides be stored?

Lyophilized material sealed and desiccated at −20 °C, protected from light. Ipamorelin's small pentapeptide structure and CJC-1295's larger conjugate have the same basic storage requirement, though reconstituted solutions of both are considerably less stable than the dry powder.

What documentation distinguishes these two on paper?

Mass spectrometry, primarily. An identity result near 712 daltons is consistent with ipamorelin and one near 3,647 daltons with CJC-1295 with DAC; a result near 3,367 daltons indicates the non-DAC GHRH analog rather than the DAC form. An HPLC purity percentage alone cannot make that distinction.

Is either of these approved for any use?

No. Neither has regulatory approval in any jurisdiction, and neither is lawful as a dietary supplement ingredient. Both are research chemicals, not for human or animal consumption.

References

• Howard et al. (1996). A receptor in pituitary and hypothalamus that functions in growth hormone release. Science.
• Raun et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology.
• Gobburu et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research.
• Svensson et al. (2000). The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. Journal of Endocrinology.
• Jetté et al. (2005). 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.
• Teichman et al. (2006). 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. The Journal of Clinical Endocrinology & Metabolism.
• Ionescu & Frohman (2006). Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. The Journal of Clinical Endocrinology & Metabolism.
• Alba et al. (2006). Once-daily administration of CJC-1295, a long-acting growth hormone-releasing hormone (GHRH) analog, normalizes growth in the GHRH knockout mouse. American Journal of Physiology-Endocrinology and Metabolism.