CJC-1295 and Ipamorelin UK 2026 Research Reference

For laboratory research use only. This page summarises published scientific literature on CJC-1295 in plain English, in a neutral research style. It is not medical advice and contains no guidance on doses, administration or human use.

Last updated: April 2026 · UK research-grade reference · For laboratory research use only — not for human consumption

Table of Contents

• 1. Overview — why CJC-1295 and ipamorelin are paired
• 2. Receptor pharmacology: two pathways, one outcome
• 3. CJC-1295 structure and DAC variant
• 4. Ipamorelin structure and selectivity
• 5. Synergy mechanism at the somatotroph
• 6. Pharmacokinetics compared
• 8. Preserving GH pulsatility — why it matters
• 9. Hormonal selectivity vs sermorelin and GHRP-6
• 12. Research applications
• 13. UK research-grade sourcing standards
• References

1. Overview — why CJC-1295 and ipamorelin are paired

CJC-1295 and ipamorelin represent the modern selective versions of this combination: CJC-1295 is the most pharmacokinetically stable GHRH analogue, and ipamorelin is the most receptor-selective ghrelin-mimetic without cortisol or prolactin elevation. For UK laboratory research into growth-hormone pulse biology, IGF-1 induction, or somatotroph receptor pharmacology, this pair is the reference combination.

2. Receptor pharmacology: two pathways, one outcome

GHRH receptor (GHRHR): Class B GPCR, expressed primarily on anterior pituitary somatotrophs. Signals via Gαs → adenylyl cyclase → cAMP → PKA → CREB phosphorylation → GH1 transcription and GH vesicle exocytosis. CJC-1295 binds here.

Ghrelin receptor (GHSR-1a): Class A GPCR, expressed on somatotrophs, hypothalamic neurons, and peripherally in gastric mucosa, pancreas, and cardiovascular tissue. Signals via Gαq → PLC → IP₃/DAG → Ca²⁺ release and PKC activation. Ipamorelin binds here.

At the somatotroph, GHRHR activation primarily drives transcriptional and secretory priming via cAMP, while GHSR-1a activation primarily drives immediate Ca²⁺-dependent exocytosis. Co-activation produces GH pulses with both larger amplitude and greater secretory reserve than either pathway alone.

3. CJC-1295 structure and DAC variant

CJC-1295 is derived from human GHRH(1-29), the smallest biologically active fragment of GHRH. Four amino acid substitutions (D-Ala²→stabilise N-terminus against DPP-4; Gln⁸, Ala¹⁵, Leu²⁷) confer increased intrinsic stability and receptor affinity.

CJC-1295 “with DAC”: Adds a maleimidopropionyl-lysine tail that reacts covalently with circulating albumin in plasma. The albumin conjugate has a half-life of approximately 8 days. Produces sustained GHRH-receptor activation. Does not preserve pulsatility — somatotroph stimulation is tonic.

4. Ipamorelin structure and selectivity

Ipamorelin is a pentapeptide — Aib-His-D-2-Nal-D-Phe-Lys-NH₂ — designed at Novo Nordisk in the 1990s as a selective ghrelin receptor agonist without cross-reactivity at the receptors responsible for cortisol and prolactin release.

Key pharmacological features:

• GHSR-1a selectivity: comparable GH-releasing potency to hexalrelin and GHRP-6 but without the cortisol, ACTH or prolactin elevation those peptides produce
• Half-life: approximately 2 hours (plasma)

5. Synergy mechanism at the somatotroph

1. Converging second-messenger pathways: cAMP (from GHRHR) and Ca²⁺ (from GHSR-1a) both potentiate GH vesicle exocytosis; their convergence is synergistic, not additive.
2. Suppression of somatostatin: GHSR-1a activation at hypothalamic sites suppresses periventricular somatostatin neurons, removing the tonic brake on GH release. CJC-1295 alone does not do this.
3. Priming of somatotroph secretory reserve: CJC-1295’s cAMP signalling increases GH1 transcription and vesicle loading; subsequent ipamorelin-driven exocytosis releases this larger reserve.

6. Pharmacokinetics compared

CJC-1295 no-DAC (mod-GRF 1-29):

• Molecular weight: 3367.91 Da (30 aa after modifications including C-terminal NH₂)
• Tmax: 10-20 min
• Duration of GH-releasing effect: 60-90 min

CJC-1295 with DAC:

• Molecular weight: 3647.20 Da (as synthesised); effective MW as albumin-DAC conjugate ~70,000 Da
• Half-life: ~8 days (as albumin conjugate)
• Duration of GH-releasing effect: continuous at steady state

Ipamorelin:

• Molecular weight: 711.86 Da (pentapeptide + N-terminal Aib)
• Half-life: 2 hours
• Duration of GH-releasing effect: 2-3 hours

8. Preserving GH pulsatility — why it matters

Physiological GH release is strongly pulsatile, with 5-8 pulses per 24 hours, peak concentrations during the first hours of sleep, and near-undetectable trough concentrations between pulses. The pulsatility itself is biologically important:

• Downstream signalling (JAK2-STAT5, MAPK) is pulse-encoded; continuous GH signalling produces different transcriptional outputs than pulsatile signalling
• Peripheral GH receptor sensitivity is maintained by trough periods; continuous stimulation produces receptor desensitisation
• Sex-dimorphic gene expression in liver is pulsatility-dependent

Research designs that want to preserve these features use CJC-1295 no-DAC; designs that accept desensitisation as a variable or deliberately model pharmacological overdrive use CJC-1295 with DAC.

9. Hormonal selectivity vs sermorelin and GHRP-6

Sermorelin: GHRH(1-29), the unmodified native fragment. Half-life 10-20 minutes. No DAC variant. Largely superseded by CJC-1295 no-DAC in research use because the four CJC substitutions produce longer half-life and greater receptor affinity without loss of selectivity.

GHRP-6: First-generation ghrelin-receptor agonist. Potent GH releaser but also potent orexigen (strong appetite stimulation), moderate cortisol and prolactin elevation. Suitable for appetite research but inferior to ipamorelin for clean growth-hormone secretagogue studies.

GHRP-2: Intermediate selectivity — better than GHRP-6 but less selective than ipamorelin.

Hexarelin: Most potent ghrelin-receptor agonist but greatest cortisol and prolactin cross-reactivity. Declining use in contemporary research.

12. Research applications

Established UK laboratory research applications for the CJC-1295 + ipamorelin combination:

• Pulsatile GH release dynamics and pulse-amplitude modelling
• IGF-1 generation and time-course studies
• Somatotroph receptor pharmacology, desensitisation and re-sensitisation kinetics
• Sex-dimorphic GH pulse pattern studies in preclinical models
• Hypothalamic-pituitary axis GH-branch stimulation tests
• Benchmarking arm in novel growth-hormone-secretagogue compound development
• Tissue-specific IGF-1 response studies (hepatic, muscle, cartilage)
• Body-composition research in rodent and non-human primate models

13. UK research-grade sourcing standards

Both peptides should be sourced with full documentation:

• ≥98% HPLC purity (≥99% is the emerging 2026 standard)
• Mass spectrometry identity confirmation (CJC-1295 no-DAC 3367.91 Da; CJC-1295 with-DAC 3647.20 Da; ipamorelin 711.86 Da)
• Batch-specific Certificate of Analysis
• Endotoxin quantification
• Residual TFA analysis
• Lyophilised powder with cold-chain shipping

A quality-control specific note for CJC-1295 with DAC: the maleimidopropionyl-lysine tail is the most difficult synthetic step and the most common site of batch-to-batch variance. A high-quality COA should specifically confirm DAC attachment yield and absence of des-DAC parent peptide.

Limits of the evidence

Published findings come from specific study designs, often in cell systems or animals, and do not transfer automatically to other settings. A paper about a molecule is not proof that any particular batch has a given biological effect. Purity data show what is in a vial; they do not show sterility, safety or suitability for any use outside the laboratory.

Laboratory handling

• Store lyophilised powder sealed, cold (−20 °C for long-term storage), dry and protected from light.
• Let vials reach room temperature before opening to limit condensation.
• Prepare solutions with suitable laboratory solvents and calibrated equipment, and label each with lot number, concentration and date.
• Split solutions into single-use aliquots and avoid repeated freeze–thaw cycles.
• Use the peptide calculator for concentration arithmetic (mg/mL).

References

1. Teichman SL et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295 in healthy adults. J Clin Endocrinol Metab 2006;91:799–805.
2. Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998;139:552–561.
3. Jimenez-Reina L et al. In vitro effects of ghrelin and GHRP-6 on somatotroph GH secretion. Endocrinology 2003;144:3336–3344.
4. Bowers CY. History of the development of GH-releasing peptides and analogues. Growth Horm IGF Res 2012;22:221–231.
5. Ionescu M, Frohman LA. Pulsatile secretion of growth hormone induced by the combination of a GH-releasing peptide and a GH-releasing hormone analog. J Clin Endocrinol Metab 2006;91:4792–4797.
6. Khorram O et al. Effects of aging on the pulsatile secretion of growth hormone and its response to GHRH. J Clin Endocrinol Metab 1997;82:1472–1479.
7. Kineman RD et al. Understanding the physiology of growth hormone-releasing hormone and growth hormone-releasing peptide action. Front Endocrinol 2011;2:24.
8. Howard AD et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science 1996;273:974–977.
9. Camanni F, Ghigo E, Arvat E. Growth hormone-releasing peptides and their analogs. Front Neuroendocrinol 1998;19:47–72.
10. Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev 2018;6:45–53.

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For laboratory research use only. CJC-1295 sold by Peptides Lab UK is supplied strictly for in vitro laboratory research. It is not for human or veterinary use, and nothing on this page is medical advice or guidance on administration. UK purchasers are responsible for complying with all applicable legislation.