CJC-1295: Mechanism of Action
1. DAC Technology — Albumin-Binding Mechanism
The DAC linker on CJC-1295 is an N-ε-3-maleimidopropionyl (MPA) group attached to the ε-amine of Lys29 at the C-terminus. After subcutaneous injection, the maleimide group undergoes a thio-Michael addition with the free thiol of serum albumin Cys-34 (the only free cysteine in circulating albumin), forming a stable, irreversible thioether bond. [1]
| Phase | Mechanism | Result |
|---|---|---|
| 1. In vivo binding | MPA maleimide + albumin Cys-34 → thioether bond | CJC-1295 becomes albumin-conjugated; plasma t½ → 6–8 days |
| 2. Slow release | Albumin-CJC-1295 complex circulates; GHRHr remains accessible | Sustained GHRH receptor stimulation for 9–11 days |
| 3. GHRHr activation | GHRHr → Gs → adenylyl cyclase → cAMP ↑ | PKA activation → GH gene transcription in somatotrophs |
| 4. GH secretion | GH released from anterior pituitary → circulation | GH → liver IGF-1 production; peripheral anabolic effects |
2. GHRHr Signaling Cascade
CJC-1295 engages the GHRH receptor (GHRHr), a class B G protein-coupled receptor expressed on anterior pituitary somatotroph cells: [2]
- Gs/cAMP pathway: GHRHr → Gs → adenylyl cyclase → cAMP ↑ → PKA activation → phosphorylation of CREB → GH gene transcription
- IP3/Ca²⁺ pathway: Secondary Gq coupling → PLC → IP3 → intracellular Ca²⁺ mobilization → GH vesicle exocytosis
- IGF-1 loop: GH → liver → IGF-1 production → peripheral tissues (muscle, bone, adipose) → anabolic signaling
- Negative feedback: Rising IGF-1 and somatostatin suppress further GH release — preserving physiological regulation
3. CJC-1295 with DAC vs. No-DAC vs. Native GHRH
| Property | Native GHRH(1-44) | No-DAC (Mod GRF 1-29) | CJC-1295 with DAC |
|---|---|---|---|
| Half-life | ~7 min | ~30 min | 6–8 days |
| GH pattern | Pulsatile | Pulsatile | Tonic/continuous |
| Clinical trials | Yes (approved) | None (FDA Dec 2024) | Phase I/II (Teichman 2006) |
| IGF-1 elevation duration | Minutes | Hours | 9–11 days |
| Albumin binding | No | No | Yes (irreversible) |
4. DNA Damage Considerations
Preclinical research (Ben-Shlomo et al., 2020) has raised the hypothesis that sustained, continuous GH stimulation via long-acting GHRH analogues may promote DNA damage in pituitary somatotroph cells — a potential concern with tonic GH elevation unlike the physiological pulsatile pattern. [6] This remains an active area of mechanistic research and is not yet established as a clinical safety signal from human trial data.
References
- Jetté L, 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, 146(7):3052–3058.
- Ionescu M, Frohman LA. (2006). Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. J Clin Endocrinol Metab, 91(12):4792–4797.
- Teichman SL, 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. J Clin Endocrinol Metab, 91(3):799–805.
- Alba M, et al. (2006). Once-monthly administration of CJC-1295, a long-acting growth hormone-releasing hormone (GHRH) analog, normalizes growth in the GHRH-deficient dwarf rat. Am J Physiol Endocrinol Metab, 291(6):E1290–E1294.
- Walker RF. (2006). Sermorelin: a better approach to management of adult-onset growth hormone insufficiency? Clin Interv Aging, 1(4):307–308.
- Ben-Shlomo A, et al. (2020). Growth hormone-releasing hormone (GHRH) and its analogues: from bench to bedside. Neuroendocrinology, 110(3–4):192–199.
- Gahete MD, et al. (2009). In vivo and in vitro evidence for the importance of growth hormone-releasing hormone in the regulation of GH secretion. Mol Cell Endocrinol, 309(1–2):40–47.
- FDA. (2024). Bulk Drug Substances Under Evaluation for Use in Compounding Under Section 503A: Category 2. Docket FDA-2013-N-1525. Federal Register, Dec 2024.
- WADA. (2024). List of Prohibited Substances and Methods. S2: Peptide Hormones, Growth Factors, Related Substances, and Mimetics. World Anti-Doping Agency.
- Frohman LA, Jansson JO. (1986). Growth hormone-releasing hormone. Endocr Rev, 7(3):223–253.
Related Research Questions
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