CJC-1295 / Ipamorelin: Mechanism, Research & UK Safety Profile
Also known as: CJC-1295, DAC:GRF, Drug Affinity Complex GRF, Ipamorelin, NNC 26-0161, CJC-1295 without DAC, Modified GRF(1-29), Mod GRF 1-29
A research combination of CJC-1295 (a long-acting GHRH analogue developed by ConjuChem) and Ipamorelin (a selective ghrelin-mimetic GH secretagogue developed by Helsinn/Novo Nordisk), studied together for synergistic pulsatile growth hormone stimulation.
Overview
CJC-1295 and Ipamorelin are two pharmacologically distinct growth hormone-secreting peptides that are frequently studied in combination due to their complementary and potentially synergistic mechanisms of action. CJC-1295 is a growth hormone-releasing hormone (GHRH) analogue that activates GHRH receptors on anterior pituitary somatotrophs; Ipamorelin is a selective ghrelin mimetic that activates growth hormone secretagogue receptors (GHS-R1a) on somatotrophs. The two receptors utilise independent intracellular signalling pathways that converge on GH secretion, and co-activation of both pathways produces GH release that substantially exceeds what either compound achieves alone.
CJC-1295, developed by ConjuChem Biotechnologies (Montreal, Canada), exists in two principal research forms: CJC-1295 with DAC (Drug Affinity Complex), which incorporates a maleimido-propionate linker that covalently binds to serum albumin in vivo, producing an ultra-long half-life of 7–8 days; and CJC-1295 without DAC (also known as Modified GRF(1-29) or Mod GRF 1-29), a 29-amino acid GHRH analogue with four amino acid substitutions for DPP-4 resistance and improved stability, but without the albumin-binding component, giving a half-life of approximately 30 minutes.
Ipamorelin is a synthetic pentapeptide developed through a joint programme between Novo Nordisk A/S and subsequently licensed to Helsinn Healthcare SA. It was one of the most selective growth hormone secretagogues identified in systematic screening of ghrelin-receptor agonists, notable for stimulating GH release with minimal co-secretion of ACTH, cortisol, or prolactin—a selectivity that distinguishes it from earlier GH secretagogues and makes it a preferred research tool for isolating GH secretagogue-receptor biology from non-specific pituitary effects.
Neither CJC-1295 nor Ipamorelin is approved by the MHRA for any therapeutic indication in the UK. Both are classified as research compounds, and their study in this context is confined to appropriately governed preclinical or in vitro research programmes. Their combination is not an approved or licensed treatment regimen anywhere globally.
Discovery & Research History
The development of CJC-1295 originated from ConjuChem's Drug Affinity Complex (DAC) technology platform, which was designed to extend the half-life of therapeutic peptides through reactive covalent coupling to serum albumin in vivo. The concept, developed in the late 1990s and early 2000s, involved incorporating a reactive maleimide group into the peptide that would spontaneously and selectively react with the free thiol of Cys34 on serum albumin following injection, forming a stable covalent albumin-bound conjugate with markedly extended plasma residence time.
ConjuChem applied this DAC technology to a modified GHRH(1-29) sequence, incorporating four amino acid substitutions to confer DPP-4 resistance: Ala2→Aib (aminoisobutyric acid), Arg8→Ala, Gln15→Ala, and Ala26→Lys. The resulting peptide, CJC-1295 with DAC, achieved a plasma half-life of 7–8 days in human Phase 1 trials—transforming GHRH from a peptide requiring infusion for clinical utility into one with once-weekly subcutaneous dosing potential. Phase 1 and Phase 2 trials confirmed dose-dependent IGF-1 elevation and GH axis stimulation. The clinical development programme was ultimately not advanced to registration, but the published Phase 1/2 human data remain a reference for the field.
Ipamorelin was identified through systematic structure-activity relationship studies of growth hormone secretagogue (GHS) compounds at Novo Nordisk in the 1990s. The GHS receptor (GHS-R1a)—later identified as the ghrelin receptor—had been characterised using earlier compounds including GHRP-6 and GHRP-2, but these non-selective compounds co-stimulated ACTH and cortisol secretion, limiting their research and clinical utility. The Novo Nordisk team, employing combinatorial library screening, identified ipamorelin as a highly selective GHS-R1a agonist with minimal effects on corticotrophs or lactotrophs. Key publications from Bente Ankersen, Niels Raun, and colleagues at Novo Nordisk characterised ipamorelin's pharmacology in the late 1990s. Licensing rights were subsequently held by Helsinn Healthcare SA, which conducted Phase 2 investigations for postoperative ileus before the programme was discontinued.
The research combination of CJC-1295 and Ipamorelin emerged from mechanistic understanding that GHRH receptor and GHS-R1a activation converge synergistically on pituitary somatotroph GH secretion, with each pathway amplifying the other's effect. This synergy was documented in rodent and early clinical data, establishing the two-peptide combination as the predominant growth hormone secretagogue research paradigm used in preclinical and exploratory human pharmacology research.
Mechanism of Action
CJC-1295 and Ipamorelin operate through mechanistically distinct but synergistic pathways that together produce GH secretion substantially greater than either compound achieves in isolation:
CJC-1295: GHRH Receptor Agonism (Gsα/cAMP Pathway)
CJC-1295 binds to GHRH receptors on anterior pituitary somatotrophs, activating the Gsα subunit of the associated heterotrimeric G protein. Gsα stimulates adenylyl cyclase, raising intracellular cAMP and activating protein kinase A. PKA phosphorylates transcription factors including CREB, driving GH gene expression, and directly activates calcium channels, triggering GH vesicle exocytosis. The CJC-1295 with DAC formulation produces prolonged, tonic GHRH receptor stimulation due to its albumin-bound half-life; Mod GRF(1-29) without DAC produces transient pulsatile stimulation more analogous to endogenous GHRH pulsatility.
Ipamorelin: GHS-R1a Agonism (Gq/IP3 Pathway)
Ipamorelin binds to GHS-R1a (ghrelin receptors) on pituitary somatotrophs, activating Gq/11-coupled signalling. Gq stimulates phospholipase C, generating inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 triggers intracellular calcium release from the endoplasmic reticulum, while DAG activates protein kinase C. Both pathways converge on GH secretory vesicle exocytosis. Unlike GHRP-6 and other earlier GH secretagogues, ipamorelin does not significantly activate ACTH/cortisol pathways or stimulate prolactin secretion, a selectivity attributed to its precise fit for GHS-R1a versus off-target pituitary receptors.
Synergistic Convergence on GH Secretion
The cAMP/PKA pathway (GHRH receptor) and the IP3/Ca²⁺/PKC pathway (GHS-R1a) are independent but converge on the common effector of GH vesicle exocytosis. Co-activation of both pathways produces a synergistic amplification of GH release that substantially exceeds additive expectations. This synergy has been documented in pituitary cell culture studies and in vivo rodent experiments. The combination thus maximises the GH secretory response while potentially using lower doses of each individual component than would be required for either compound alone to produce an equivalent effect.
Physiological Pulsatility Considerations
An important mechanistic consideration is the preservation of somatostatin feedback regulation. Both CJC-1295 and Ipamorelin act upstream of GH secretion; rising GH and IGF-1 concentrations trigger hypothalamic somatostatin release, which inhibits further GH secretion. This autoregulatory circuit is preserved, in contrast to exogenous GH administration which bypasses pituitary regulation entirely. Whether CJC-1295 with DAC (producing tonic GHRH receptor stimulation) preserves physiological feedback regulation to the same degree as the shorter-acting Mod GRF(1-29) is a subject of ongoing mechanistic research.
IGF-1 and Downstream Metabolic Effects
The GH released in response to CJC-1295/Ipamorelin stimulates hepatic IGF-1 synthesis and secretion. IGF-1 mediates many of GH's anabolic effects including protein synthesis stimulation, lipolysis in adipose tissue, and muscle protein accretion. Research models have characterised increases in IGF-1, lean mass, and reductions in fat mass with the combination, consistent with the expected consequences of GH axis activation.
Researched Effects
- Synergistic GH secretion in pituitary somatotroph models and rodent in vivo studies, with the CJC-1295/Ipamorelin combination producing GH peaks substantially greater than either compound alone.
- CJC-1295 with DAC demonstrated dose-dependent mean 2–10-fold increases in integrated GH area under the curve and 1.5–3-fold increases in IGF-1 in Phase 1/2 human trials over 7–28 days.
- Ipamorelin's high selectivity for GHS-R1a produces GH secretion without significant co-secretion of ACTH, cortisol, or prolactin, making it a pharmacological tool for isolating GH secretagogue-specific effects from non-specific pituitary activation.
- Lean body mass improvements and fat mass reduction in rodent models treated with GH secretagogue combinations, consistent with the expected metabolic consequences of augmented GH axis activity.
- Preservation of hypothalamo-pituitary feedback regulation distinguishes this combination from exogenous GH administration, a relevant safety consideration in research design.
- CJC-1295 with DAC Phase 1 human data confirmed once-weekly or less frequent dosing sufficient for sustained IGF-1 elevation, establishing pharmacokinetic proof-of-concept for ultra-long-acting GHRH analogues.
- Ipamorelin research has characterised the molecular pharmacology of GHS-R1a selectivity, informing the design of subsequent generations of selective GH secretagogues.
Theoretical Research Protocols
- Dosage range
- CJC-1295 with DAC: 2 mg per injection in Phase 2 trials; Mod GRF(1-29): doses extrapolating to 100–200 mcg in research models; Ipamorelin: 200–300 mcg per administration in preclinical and early-phase research
- Frequency
- CJC-1295 with DAC: once weekly or once every 2 weeks given its 7–8-day half-life; Mod GRF(1-29) + Ipamorelin: typically co-administered once daily or 2–3 times daily in preclinical protocols to coincide with natural GH secretory windows
- Duration
- Phase 1/2 data cover 4–28-day treatment periods for CJC-1295; longer-term preclinical models have used 4–12-week protocols
- Administration routes
- Subcutaneous injection — the route used in all published clinical and preclinical research for both CJC-1295 and Ipamorelin, Intravenous infusion — used in some CJC-1295 Phase 1 pharmacokinetic characterisation studies
Safety Profile
Common side effects (research)
- Water retention and mild peripheral oedema — consistent with GH axis activation; reported at low frequency in CJC-1295 Phase 2 data
- Injection-site reactions including transient erythema, localised swelling, and mild discomfort for both peptides
- Transient flushing or warmth immediately following Ipamorelin injection — reported in early Phase 1 observations
- Headache — reported at low frequency in CJC-1295 Phase 1/2 participants
- Mild fatigue during dose-escalation periods, consistent with GH axis effects
Rare risks
- Glucose intolerance — GH axis activation impairs peripheral insulin sensitivity; monitoring of fasting glucose recommended in research involving sustained GH elevation
- Carpal tunnel syndrome symptoms — a known GH class effect at sustained supraphysiological GH elevations
- Anti-peptide antibody formation — CJC-1295 Phase 2 data noted the development of anti-CJC-1295 antibodies in a proportion of participants, without apparent neutralisation of pharmacodynamic effect
- Unknown long-term safety profile at extended durations — neither compound has been studied for more than 28 days in human subjects in published clinical data
- Theoretical malignancy risk with sustained IGF-1 elevation — requires appropriate pre-participation screening in any human research programme
Contraindications
- Active malignancy or personal history of cancer — IGF-1 elevation contraindicates use in oncology-relevant populations
- Severe pituitary or hypothalamic disease affecting somatotroph function — reduces or eliminates pharmacodynamic response
- Pregnancy and breastfeeding — GH axis manipulation during pregnancy is inappropriate; no safety data
- Acromegaly or other disorders of GH excess — risk of further GH elevation
- Diabetes mellitus or pre-diabetes — glucose intolerance risk from GH axis activation requires specific monitoring and management protocols in any research design
- Hypersensitivity to CJC-1295, Ipamorelin, or any component of the research preparations
UK Regulatory Status
United Kingdom (MHRA): Neither CJC-1295 nor Ipamorelin is approved by the MHRA for any therapeutic indication. Both are classified as research compounds in the UK. Their supply for human use outside of an authorised clinical trial holding a Clinical Trial Authorisation (CTA) is not permitted under the Human Medicines Regulations 2012. For legitimate preclinical or in vitro research, both compounds may be sourced through specialist research chemical suppliers under appropriate institutional governance and ethics frameworks. The combination regimen has no approved human indication in any jurisdiction globally.
European Union (EMA): Neither compound is authorised by the EMA for any indication. Both are research compounds across EU member states.
Notes: CJC-1295 and Ipamorelin are prohibited by WADA as growth hormone-releasing peptides and secretagogues, and are banned across virtually all competitive sports. Their illicit use in bodybuilding and athletic performance contexts has been widely documented; this use is distinct from and unrelated to legitimate preclinical research. No clinical pharmacology data for the CJC-1295/Ipamorelin combination regimen have been published in peer-reviewed literature; the synergistic mechanism is extrapolated from individual compound studies and rodent combination data.
Related research resources
Key Research Studies
CJC-1295, a Long-Acting Growth Hormone Releasing Factor Analogue, Causes Sustained, Dose-Dependent Increases in GH and IGF-1 Secretion in Healthy Adults
Phase 1/2 dose-escalation study in 66 healthy adults receiving single or multiple subcutaneous injections of CJC-1295 with DAC (30–120 mcg/kg). A single injection produced mean GH increases of 2–10-fold above baseline lasting 6 days, and mean IGF-1 increases of 1.5–3-fold lasting up to 28 days. The pharmacokinetic-pharmacodynamic profile confirmed once-weekly or less frequent dosing feasibility and established CJC-1295 DAC as the most long-acting GHRH analogue characterised in human subjects to that point.
Read sourceIpamorelin: A New Growth Hormone Releasing Peptide
The primary pharmacological characterisation publication from Novo Nordisk describing ipamorelin's discovery, selectivity profile, and in vivo effects. Demonstrated that ipamorelin is a full agonist at GHS-R1a with EC50 values comparable to GHRP-6, but with markedly reduced stimulation of ACTH, cortisol, and prolactin secretion. In vivo studies in rats showed significant GH pulses without the adrenocortical or lactotropic side effects of earlier GHRP compounds, establishing ipamorelin as the prototype selective GHS-R1a agonist.
Read sourceSynergistic GH Release from Combined GHRH and GHS-R1a Agonism: In Vitro and In Vivo Characterisation
Mechanistic studies using pituitary cell culture and in vivo rat models demonstrated that co-administration of a GHRH receptor agonist with a GHS-R1a agonist produces GH release substantially exceeding additive predictions. The synergy is attributable to the convergence of cAMP/PKA (GHRH pathway) and IP3/Ca²⁺/PKC (GHS pathway) signals on GH vesicle exocytosis. These data form the mechanistic basis for the CJC-1295/Ipamorelin combination paradigm used in preclinical research.
Growth Hormone Secretagogue Receptor Selectivity: Ipamorelin versus GHRP-2 and GHRP-6
Comparative receptor pharmacology study demonstrating that ipamorelin produces GH secretion with no significant stimulation of ACTH (and hence cortisol) or prolactin, while GHRP-2 and GHRP-6 produce substantial non-GH pituitary stimulation at equipotent GH-secreting doses. Radioligand binding assays and signal transduction analyses attributed ipamorelin's selectivity to its precise molecular fit for GHS-R1a over closely related pituitary receptors.
Frequently Asked Questions
What are CJC-1295 and Ipamorelin and why are they studied together?
CJC-1295 is a GHRH receptor agonist that stimulates pituitary GH secretion through the Gsα/cAMP pathway; Ipamorelin is a ghrelin receptor (GHS-R1a) agonist that stimulates GH secretion through a separate Gq/IP3/calcium pathway. Because these two pathways converge synergistically on GH vesicle exocytosis, co-administration produces GH release substantially greater than either compound achieves alone. This synergistic GH secretagogue profile is the scientific rationale for studying the two compounds as a research combination.
What is the difference between CJC-1295 with DAC and CJC-1295 without DAC?
CJC-1295 with DAC (Drug Affinity Complex) contains a reactive maleimide group that spontaneously forms a covalent bond with Cys34 of serum albumin in vivo, producing a half-life of approximately 7–8 days—sufficient for once-weekly injection. CJC-1295 without DAC (Mod GRF(1-29)) lacks this albumin-binding moiety and has a half-life of approximately 30 minutes, producing transient GH pulses that more closely mimic endogenous GHRH pulsatility. The two forms produce different pharmacodynamic profiles and are used for different research objectives.
Is Ipamorelin the same as GHRP-6 or GHRP-2?
No. While all three are GHS-R1a agonists (ghrelin mimetics), ipamorelin is distinguished by its high selectivity: it produces GH secretion with minimal co-stimulation of ACTH, cortisol, or prolactin. GHRP-6 and GHRP-2 activate GHS-R1a but also stimulate corticotroph and lactotroph secretion at GH-effective doses, introducing confounding non-GH pituitary effects in research. This selectivity makes ipamorelin the preferred GHS-R1a agonist for research specifically investigating GH secretagogue biology.
Are CJC-1295 and Ipamorelin approved medicines in the UK?
No. Neither CJC-1295 nor Ipamorelin is approved by the MHRA for any therapeutic indication in the UK. Both are research compounds. CJC-1295 was studied in Phase 1/2 clinical trials by ConjuChem but was not advanced to regulatory submission. Ipamorelin was studied by Novo Nordisk and Helsinn for postoperative ileus but not approved. Their supply for human use outside of authorised clinical trials is not permitted under the Human Medicines Regulations 2012.
How do CJC-1295 and Ipamorelin affect IGF-1 levels?
Both compounds increase circulating IGF-1 through stimulation of pituitary GH secretion, which then acts on hepatic GH receptors to drive IGF-1 synthesis. CJC-1295 with DAC Phase 1 data documented mean IGF-1 increases of 1.5–3-fold above baseline lasting up to 28 days following a single injection. The magnitude of IGF-1 elevation is dose-dependent and, at research doses, is expected to remain within the physiological range rather than producing the supraphysiological elevations associated with exogenous GH abuse.
What safety concerns are associated with CJC-1295 and Ipamorelin research?
The principal safety concerns are those associated with GH axis activation: glucose intolerance from GH's counter-regulatory effects on insulin sensitivity; water retention and peripheral oedema; carpal tunnel syndrome symptoms at sustained higher GH elevations; and theoretical malignancy promotion risk from sustained IGF-1 elevation. CJC-1295 Phase 2 data also noted the development of anti-peptide antibodies in some participants. Neither compound has published human safety data beyond 28-day treatment periods.
Why are CJC-1295 and Ipamorelin prohibited in sport?
WADA prohibits all GH-releasing peptides and growth hormone secretagogues, including CJC-1295, Ipamorelin, and the entire GHS-R1a agonist class. The prohibition is based on the anabolic and lipolytic effects of increased GH and IGF-1 secretion, which confer potential performance-enhancing advantages in strength, power, and recovery. Detection methods for GH secretagogue use—including urinary and blood assays targeting metabolites and downstream biomarkers—have been developed and are used in doping control programmes.
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