CJC-1295: Engineered for a Longer Pituitary Signal

The short version

CJC-1295 is a synthetic analogue of the first 29 residues of growth hormone-releasing hormone — the peptide the hypothalamus sends to the pituitary to trigger growth hormone release. It differs from the natural sequence in four amino-acid positions that protect it from enzymatic breakdown. In its most common research form, it also carries a chemical moiety called the Drug Affinity Complex (DAC) that attaches it covalently to circulating serum albumin, extending its half-life from minutes to roughly six to eight days ^[16].

In healthy adults, a single subcutaneous dose produced dose-dependent two- to ten-fold increases in mean plasma GH for six days or more, and IGF-1 elevations lasting nine to eleven days ^[16]. Pulsatile GH secretion was preserved throughout ^[17]. These are the most directly relevant human findings. CJC-1295 has never been approved for any use by any regulator, it is listed as a prohibited substance under WADA Section S2, and this page lists no human dose.

What it is

CJC-1295 is a synthetic GHRH analogue built on the first 29 residues of human growth-hormone-releasing factor, hGRF(1-29). Four amino-acid substitutions are introduced: D-Ala at position 2 (blocks DPP-IV cleavage), Gln at 8, Ala at 15, and Leu at 27 (the latter two stabilise the alpha-helix and block deamidation/oxidation). The result is a protease-resistant peptide that retains full receptor-binding activity.

The DAC variant (also called DAC:GRF) adds a maleimidopropionyl (MPA) linker on a C-terminal lysine that undergoes a Michael addition reaction with the free thiol on Cys34 of circulating serum albumin — forming a covalent peptide-albumin conjugate with an extended half-life toward that of albumin itself (about six to eight days measured in human subjects) ^[16].

The no-DAC form (also called Modified GRF 1-29, or Mod GRF 1-29) keeps the four protease-resistant substitutions but lacks the albumin-binding moiety, so it remains short-acting. Community discussion routinely conflates the two; pharmacokinetically they are very different compounds ^[13].

How it works

CJC-1295 binds the growth hormone-releasing hormone receptor (GHRHR) on anterior-pituitary somatotrophs and activates the same Gs/cAMP/PKA signalling cascade as native GHRH, stimulating GH synthesis and release. Downstream, GH drives hepatic production of IGF-1.

The DAC modification means that a single dose maintains above-baseline GH and IGF-1 for days, not hours. When CJC-1295 (60 or 90 µg/kg) was given to healthy men aged 20–40, basal (trough) GH increased approximately 7.5-fold, mean GH by ~46%, and IGF-1 by ~45% one week later ^[17]. Importantly, the frequency and amplitude of pulsatile GH secretion were not significantly altered — the natural rhythm was preserved even under sustained GHRH-analogue stimulation ^[17]. A 2025 review in Nature Reviews Endocrinology synthesises the receptor pharmacology, design rationale and therapeutic landscape of GHRH analogues as a class, situating CJC-1295 within that framework ^[13].

What the research shows

Dose-dependent GH and IGF-1 elevation. In healthy adults aged 21–61, single subcutaneous doses of 30 or 60 µg/kg CJC-1295 produced two- to ten-fold increases in mean plasma GH for six days or more and 1.5- to 3-fold increases in IGF-1 for 9–11 days; after multiple doses IGF-1 remained above baseline for up to 28 days. Estimated half-life was 5.8–8.1 days ^[16].

GH pulsatility preserved. In healthy men aged 20–40, CJC-1295 (60 or 90 µg/kg) raised trough GH approximately 7.5-fold and mean GH by ~46% while leaving the frequency and magnitude of endogenous GH pulses intact, indicating pulsatile architecture persists under continuous GHRH-analogue stimulation ^[17].

Serum proteomic shifts. In eleven healthy young men, CJC-1295 administration shifted the serum proteome — decreased apolipoprotein A1 and a transthyretin isoform; increased an albumin fragment and immunoglobulin species — and the albumin-fragment signal correlated linearly with IGF-1, identifying candidate biomarkers of GH/IGF-1 axis activation ^[15].

Anti-doping identification. CJC-1295 was structurally identified by high-resolution LC-MS/MS as the active ingredient in an unknown pharmaceutical preparation seized in an anti-doping context, confirming its use as a black-market doping agent and establishing the detection methodology ^[14].

Class pharmacology context. The 2025 Nature Reviews Endocrinology review synthesises the pharmacology of GHRH and synthetic analogues including CJC-1295, sermorelin and tesamorelin, covering receptor signalling, long-acting analogue design rationale and the therapeutic/investigational landscape ^[13].

Reported effects, cautions and safety

CJC-1295 has a defined pharmacokinetic profile in healthy humans and a well-understood receptor mechanism, but its caution profile is substantial:

• Never approved. CJC-1295 has not been approved by the FDA or any major regulator for any human use. The original long-acting DAC programme (ConjuChem) was discontinued; a patient death during that development era is frequently cited in the literature, though a causal link to CJC-1295 was not established in the public record ^[13].
• DAC versus no-DAC confusion. Community sources and vendors routinely equate CJC-1295 DAC (half-life ~6–8 days) with Modified GRF 1-29 / no-DAC (short-acting, minutes to hours). They are pharmacokinetically distinct; the published human data were all obtained with the DAC form ^[16][17].
• IGF-1 and theoretical cancer risk. Sustained elevation of GH and IGF-1 raises theoretical concerns: epidemiological data link higher IGF-1 to modestly increased risk of certain cancers. FDA briefing materials for the 2024 Pharmacy Compounding Advisory Committee cited immunogenicity and safety concerns for GH secretagogues including CJC-1295; it was not recommended for the 503A compounding bulks list ^[13].
• Fluid retention and insulin sensitivity. GH-axis stimulation can cause fluid retention, oedema and effects on insulin sensitivity — effects documented with recombinant GH and expected to be relevant to CJC-1295 by mechanism ^[13].
• WADA prohibition. CJC-1295 is prohibited at all times under WADA Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics). Detection assays using LC-MS/MS and immuno-PCR are well established ^[14].
• Thin human evidence base. Published human data consist of early pharmacokinetic and serum-biomarker studies; there are no completed controlled efficacy trials in any condition ^[16][17].

No community-anecdote reports are compiled in this desk's source material for CJC-1295, so none are presented; the above are drawn from the cited literature.

Where it fits in GH axis research

CJC-1295 is the pharmacological archetype on this desk: a molecule engineered to make pituitary GH stimulation more durable, with clean human PK data showing it achieves that goal, and no controlled human efficacy trials to say what that durability produces clinically beyond the measured GH and IGF-1 numbers ^[16]. Where tesamorelin has been taken all the way through Phase 3 RCTs to approval for a specific indication, CJC-1295 stopped at pharmacokinetics and the development programme was discontinued. Where MOTS-c operates at a cellular level beneath the pituitary, CJC-1295 acts at the apex of the GH axis — the hypothalamic-pituitary interface — making it the most structurally comparable to tesamorelin, though without the clinical trial record. See the comparison page for the side-by-side.