# CJC-1295 Research: Mechanism, Variants, Pairing, and the Phase-1 Record

> The CJC-1295 research literature in plain English: GHRH-receptor mechanism, the DAC vs no-DAC variant comparison, the ipamorelin pairing, and what phase-1 trials measured.

*Three decades of GHRH pharmacology, applied to a 30-amino-acid analog with a maleimide linker. Set out feature by feature.*

## CJC-1295 mechanism of action

CJC-1295 is a GHRH-receptor agonist on anterior-pituitary somatotrophs [1]. Binding to the receptor activates Gs-protein-coupled signaling, raises intracellular cyclic AMP, drives protein kinase A activity, and triggers exocytotic release of stored growth hormone. The released GH then acts on hepatic GH receptors to induce IGF-1 transcription [1]. The four amino-acid substitutions in the CJC-1295 sequence — D-Ala at position 2, Gln at 8, Ala at 15, and Leu at 27 — block dipeptidyl-peptidase-IV cleavage between residues 2 and 3, which is what inactivates native GHRH within minutes [6]. The DAC moiety, when present, covalently binds Cys34 of serum albumin via maleimide chemistry; the albumin tether shields the peptide from clearance and extends the plasma residence time by roughly two orders of magnitude [5]. Pulsatility of GH secretion is preserved despite sustained receptor occupancy [2]. The pulse generator is upstream of the receptor and is not desensitized by tonic GHRH-receptor activation across the studied dosing windows.

## CJC-1295 with DAC vs no DAC

The two variants share the same 30-residue backbone and the same four sequence substitutions [5]. The DAC variant adds a maleimidopropionic-acid (MPA) lysine derivative at the C-terminus that covalently binds the free Cys34 thiol on circulating serum albumin [5]. The no-DAC variant — equivalent to [modified GRF (1-29)](/research#modified-grf) — does not. The pharmacokinetic difference is dramatic. CJC-1295 with DAC: plasma half-life of approximately 5.8 to 8.1 days in healthy adults [1]. CJC-1295 without DAC: plasma half-life of approximately 30 minutes. The dosing-frequency implications follow directly: weekly or every-other-week intervals were used in the phase-1 multi-dose arm of the DAC variant [16]; the no-DAC variant requires far more frequent administration in research protocols. The two variants are pharmacodynamically equivalent at the receptor — they bind the same GHRH receptor and drive the same downstream cascade — but produce very different exposure profiles.

## Modified GRF (1-29): the precursor to CJC-1295

Modified GRF (1-29) is the 30-amino-acid CJC-1295 backbone without the DAC linker — sometimes written ModGRF, Mod GRF 1-29, or CJC-1295 no-DAC. The four sequence substitutions (D-Ala-2, Gln-8, Ala-15, Leu-27) are identical to those in the DAC variant and confer the same protease resistance [6]. What modified GRF (1-29) lacks is the albumin-binding C-terminal maleimide moiety. In its absence, the peptide is cleared at the rate set by renal filtration and residual peptidase activity, producing a plasma half-life of approximately 30 minutes. Research protocols that prefer pulsatile rather than sustained receptor occupancy use modified GRF (1-29) for that reason. The native unmodified parent fragment — sermorelin / GHRH (1-29) — has a still shorter plasma half-life of approximately 7 to 20 minutes, illustrating how each modification step extends pharmacokinetic residence [10].

## CJC-1295 and Ipamorelin: the GHRH + GHRP Pairing

CJC-1295 and ipamorelin activate two non-overlapping receptors on the same target cell [7][8]. CJC-1295 binds the GHRH receptor; ipamorelin binds the ghrelin / GHS-R1a receptor [7]. The downstream pathways are mechanistically distinct: GHRH-receptor stimulation raises intracellular cyclic AMP via Gs; ghrelin-receptor stimulation raises intracellular calcium via phospholipase C and IP3 [8]. Both pathways converge on the somatotroph's GH-release machinery without competing for the same binding site, so combination dosing in published research produces additive — and in some preclinical models supra-additive — growth-hormone pulse amplitude versus either compound alone [8]. Ipamorelin in particular is characterized by selectivity: in healthy-volunteer dose-finding work, dose-dependent GH release occurred without significant elevation of ACTH, cortisol, FSH, LH, prolactin, or TSH [7][15]. That selectivity is why ipamorelin is the conventional GHRP partner for a GHRH analog like CJC-1295 in research protocols where additional HPA-axis activation is undesirable.

## CJC-1295 vs ipamorelin: GHRH analog vs GHRP

These are not the same kind of molecule. CJC-1295 is a 30-amino-acid GHRH analog — a synthetic version of the upstream hypothalamic releasing hormone, acting on the GHRH receptor [1]. Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that mimics ghrelin and acts on the ghrelin / GHS-R1a receptor [7]. Both produce GH release, but through different receptors. The pharmacokinetic profiles diverge as well: CJC-1295 with DAC has a half-life of roughly 7-8 days [1]; ipamorelin is short-acting on the order of an hour in plasma. The two are most commonly described in the research literature as **complementary** rather than substitutable — pairing them lets researchers stimulate the somatotroph through two independent receptors simultaneously, exploiting the additive pulse amplitude documented across rodent, ovine, and human bolus studies [8].

## Effects observed in published CJC-1295 research

Across the indexed literature, four endpoints recur. **Growth-hormone elevation**: 2- to 10-fold dose-dependent increases in mean plasma GH following single subcutaneous doses of 30 to 250 µg/kg in healthy adults, sustained at least six days at higher doses [1]. **IGF-1 elevation**: 1.5- to 3-fold above baseline for 9 to 11 days following a single DAC dose, with cumulative elevation across 49 days in the multi-dose arm at 60 µg/kg weekly or every other week [1][16]. **Pulse preservation**: pulse frequency unchanged under continuous receptor stimulation; both pulse amplitude and inter-pulse baseline elevated [2]. **Downstream proteomic shifts**: reproducible changes in serum protein composition following a single 90 µg/kg dose, including downregulation of apolipoprotein A1 and transthyretin isoforms and upregulation of beta-hemoglobin and albumin fragments [4]. These are pharmacodynamic markers — they describe what the molecule does to measurable serum analytes, not what it does to symptoms, body composition, or clinical outcomes in any indicated population.

## What clinical and preclinical CJC-1295 studies have reported

Two completed phase-1 trials in healthy adults form the published human evidence base for CJC-1295 with DAC: a single-ascending-dose arm (30, 60, 125, 250 µg/kg subcutaneous) and a multi-dose arm (60 µg/kg subcutaneous weekly or every other week for 49 days), with n ≈ 65 total participants across both arms [1][16]. The companion pulsatility analysis [2] used samples from the multi-dose arm. One phase-2 trial of CJC-1295 with DAC in HIV-associated lipodystrophy was halted after a fatal cardiovascular event roughly two hours after the eleventh weekly dose; the trial investigator attributed it to pre-existing coronary disease judged unrelated to study drug, and the development program did not continue past phase 2 [14]. Preclinical work includes the Alba 2006 GHRH-knockout mouse study showing that once-daily CJC-1295 normalized body weight, lean mass, and subcutaneous fat distribution versus untreated knockout controls [3]. The Henninge 2010 analytical-chemistry paper characterized a seized doping-market preparation, confirming the 30-residue sequence and the C-terminal maleimide moiety [5]. The 2025 WADA Prohibited List continues to name CJC-1295 explicitly under Section S2.2 [12].

## Onset of measurable effects in published trials

Phase-1 trials measured plasma GH elevation within hours of a single subcutaneous dose of CJC-1295 with DAC and sustained IGF-1 elevation for one to two weeks following that single dose [1]. The measured endpoint is biochemical — serum GH and IGF-1 — not subjective. Subjective sensations of energy, sleep quality, or body composition are outside the scope of pharmacokinetic studies and are not reported as primary endpoints in the indexed phase-1 literature.

## CJC-1295 and sleep architecture

Growth hormone is released predominantly during slow-wave sleep, and GHRH-receptor activation has direct sleep-architecture effects independent of peripheral GH. A 1992 study by Steiger and colleagues found that intranasal native GHRH administered 30 minutes before bedtime enhanced slow-wave sleep proportion (particularly in the latter half of the night) and reduced early-night cortisol in healthy male subjects [9]. That work is upstream of CJC-1295 but informs interpretation of any reported sleep observations in the GHRH-analog class; CJC-1295's own published phase-1 trials did not include polysomnography as a primary endpoint.

## References

[1] Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA. 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. J Clin Endocrinol Metab. 2006;91(3):799-805. doi:10.1210/jc.2005-1536 https://academic.oup.com/jcem/article/91/3/799/2843281
[2] Ionescu M, Frohman LA. Pulsatile Secretion of Growth Hormone (GH) Persists during Continuous Stimulation by CJC-1295, a Long-Acting GH-Releasing Hormone Analog. J Clin Endocrinol Metab. 2006;91(12):4792-4797. doi:10.1210/jc.2006-1702 https://academic.oup.com/jcem/article/91/12/4792/2656274
[3] Alba M, Fintini D, Sagazio A, Lawrence B, Castaigne JP, Frohman LA, Salvatori R. Once-daily administration of CJC-1295, a long-acting growth hormone-releasing hormone (GHRH) analog, normalizes growth in the GHRH knockout mouse. Am J Physiol Endocrinol Metab. 2006;291(6):E1290-E1294. doi:10.1152/ajpendo.00201.2006 https://pubmed.ncbi.nlm.nih.gov/16822960/
[4] Sackmann-Sala L, Ding J, Frohman LA, Kopchick JJ. Activation of the GH/IGF-1 axis by CJC-1295, a long-acting GHRH analog, results in serum protein profile changes in normal adult subjects. Growth Horm IGF Res. 2009;19(6):471-477. doi:10.1016/j.ghir.2009.03.001 https://www.sciencedirect.com/science/article/abs/pii/S1096637409000409
[5] Henninge J, Pepaj M, Hullstein I, Hemmersbach P. Identification of CJC-1295, a growth-hormone-releasing peptide, in an unknown pharmaceutical preparation. Drug Test Anal. 2010;2(11-12):647-650. doi:10.1002/dta.158 https://pubmed.ncbi.nlm.nih.gov/21204297/
[6] Frohman LA, Downs TR, Heimer EP, Felix AM. Degradation of human growth hormone-releasing factor (hGRF 1-29)-NH2 by various peptidases and DPP-IV-mediated inactivation. J Clin Invest. 1989;83(5):1533-1540. doi:10.1172/JCI114122 https://www.jci.org/articles/view/114122
[7] Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561. doi:10.1530/eje.0.1390552 https://academic.oup.com/ejendo/article-abstract/139/5/552/6748390
[8] Bowers CY, Reynolds GA, Durham D, Barrera CM, Pezzoli SS, Thorner MO. Growth hormone-releasing peptide-6 (GHRP-6) stimulates growth hormone secretion synergistically with GHRH in normal subjects. J Clin Endocrinol Metab. 1990;70(4):975-982. doi:10.1210/jcem-70-4-975 https://pubmed.ncbi.nlm.nih.gov/2108187/
[9] Steiger A, Guldner J, Hemmeter U, Rothe B, Wiedemann K, Holsboer F. Sleep-promoting effects of growth hormone-releasing hormone in normal men. Neuroendocrinology. 1992;56(4):566-573. doi:10.1159/000126067 https://pubmed.ncbi.nlm.nih.gov/1361964/
[10] Frohman LA, Thominet JL, Webb CB, Vance ML, Uderman H, Rivier J, Vale W, Thorner MO. Pharmacokinetics of growth hormone releasing factor [GRF(1-29)NH2] in normal men. J Clin Invest. 1984;73(5):1304-1311. doi:10.1172/JCI111574 https://www.jci.org/articles/view/111574
[12] World Anti-Doping Agency. World Anti-Doping Code International Standard — Prohibited List 2025. WADA-AMA. https://www.wada-ama.org/en/prohibited-list
[14] Carter M. Lipodystrophy study halted after patient death. aidsmap (NAM news report on ConjuChem trial CL-2002). 2006. https://www.aidsmap.com/news/jul-2006/lipodystrophy-study-halted-after-patient-death
[15] Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Growth hormone (GH) response to ipamorelin, a new pentapeptidic selective GH secretagogue, in healthy volunteers. Pharm Res. 1999;16(9):1412-1416. doi:10.1023/A:1018955126402 https://pubmed.ncbi.nlm.nih.gov/10496658/
[16] Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA. 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 — multi-dose arm. J Clin Endocrinol Metab. 2006;91(3):799-805. doi:10.1210/jc.2005-1536 https://academic.oup.com/jcem/article/91/3/799/2843281

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The CJC-1295 research record, set out as a specification — not a clinic, not a vendor, not a prescription.