CJC-1295: Days Bought With a Covalent Bond

The short version

CJC-1295 is a lab-made copy of the first 29 building blocks of a natural hormone that tells the pituitary gland to release growth hormone. On its own that natural fragment is destroyed in the blood almost immediately.

Four of its building blocks were swapped for versions the blood enzymes cannot cut. That alone helps. One version goes further: it carries a small chemical hook that latches permanently onto albumin, the most common protein in blood. Hooked to albumin, the peptide is carried around instead of being filtered out.

The result was measured in healthy adults. A single injection kept the molecule in circulation for days rather than minutes ^[4].

Two forms are sold under one name, and they behave very differently. The hooked form lasts days. The unhooked form lasts minutes to hours. Confusing them is the most common error in this subject ^[7]. CJC-1295 is not approved for use in people anywhere ^[4].

What it is

CJC-1295 is a synthetic analogue of growth-hormone-releasing hormone, built on hGRF(1-29) — the first 29 residues of human growth-hormone-releasing factor. It carries four amino-acid substitutions: D-alanine at position 2, glutamine at 8, alanine at 15 and leucine at 27. Together they stabilise the alpha-helix and block cleavage by dipeptidylpeptidase-IV, along with deamidation and oxidation.

The DAC variant — Drug Affinity Complex — adds a maleimidopropionyl linker on a C-terminal lysine. That linker undergoes Michael addition with the free thiol on cysteine-34 of circulating serum albumin, producing a covalent peptide-albumin conjugate. The peptide's residence time then approaches that of albumin itself.

The no-DAC form, sold as Modified GRF (1-29), keeps the four substitutions and omits the linker. It is short-acting. Both are catalogued under the same trade name in the grey market, which is the source of most of the confusion around this compound ^[7].

Its identity has been confirmed analytically in the wild: high-resolution LC-MS/MS identified CJC-1295 as the active ingredient of an unlabelled growth-hormone-releasing preparation seized in an anti-doping context ^[2]. The broader pharmacology of GHRH and its synthetic analogues — the class that also contains sermorelin and tesamorelin — is set out in a 2024/2025 review covering receptor signalling and the rationale behind long-acting analogue design ^[1].

How it works

CJC-1295 binds the growth-hormone-releasing hormone receptor on anterior-pituitary somatotrophs. That activates Gs/cAMP/PKA signalling, which stimulates synthesis and pulsatile release of growth hormone, which in turn drives hepatic IGF-1 production.

The pharmacological interest is the duration, not the mechanism. The mechanism is the same one native GHRH uses. What the substitutions and the albumin conjugate change is how long the receptor keeps seeing an agonist.

That raises an obvious question about pulsatility: growth hormone is normally released in bursts, and continuous stimulation could in principle flatten the rhythm. It did not. In healthy men aged 20 to 40, a single subcutaneous dose of 60 or 90 micrograms per kilogram raised trough growth hormone roughly 7.5-fold, mean growth hormone by about 46 per cent and IGF-1 by about 45 per cent one week later, while the frequency and magnitude of pulsatile secretion were unaltered ^[5]. Pulsatility survived the long-acting agonist.

The albumin strategy was validated at the design stage in animals. A series of hGRF(1-29) analogues bearing a C-terminal maleimidopropionyl-lysine handle was screened; the lead compound combined the four protective substitutions with covalent albumin bioconjugation and produced a four-fold increase in growth-hormone AUC over two hours compared with unconjugated hGRF(1-29) in rats, with peptide still detectable in plasma beyond 72 hours and improved in vitro stability against dipeptidylpeptidase-IV ^[7].

What the research shows

The human pharmacokinetic dataset is small and old, and it is the entire quantitative basis for the duration claims made about this compound.

In healthy adults, single subcutaneous doses of 30 or 60 micrograms per kilogram produced dose-dependent 2- to 10-fold increases in mean plasma growth hormone lasting six days or more, and 1.5- to 3-fold increases in IGF-1 lasting nine to eleven days. After multiple doses, IGF-1 remained above baseline for up to 28 days. The estimated half-life of CJC-1295 in that study was 5.8 to 8.1 days ^[4]. Those figures are from human subjects, and they are the only human half-life numbers for this compound in this digest's reference set.

A proteomic study in 11 healthy young adult men found that CJC-1295 administration shifted the serum proteome — apolipoprotein A1 and a transthyretin isoform decreased, a C-terminal albumin fragment and immunoglobulin and beta-haemoglobin species increased — and the immunoglobulin and albumin-fragment signal correlated linearly with IGF-1, identifying candidate biomarkers of axis activation ^[3]. The albumin fragment is a notable detail given that albumin is the molecule the DAC variant is bound to.

The interval work is entirely rodent. In GHRH-knockout mice, 2 micrograms of CJC-1295 given once every 24 hours fully normalised body weight and length, whereas dosing every 48 to 72 hours was progressively less effective; pituitary growth-hormone messenger RNA rose with treatment ^[6]. That is a mouse experiment establishing what a mouse model needed to grow normally. It is not a human schedule, it does not become one by conversion, and nothing on this site should be read as suggesting otherwise.

Reported effects, cautions and safety

The following reports come from peptide-user forums, clinic write-ups summarising client feedback and consumer guides. They are anecdotal, not clinical evidence. No doses are attached to any of them, and none has been measured in a controlled trial of this compound.

Deeper and more restful sleep is very commonly reported, and is often described as the first noticeable change. Faster recovery from training and reduced soreness, gradual fat loss around the midsection, a leaner appearance with better muscle retention are all frequently reported. More daytime energy, improved focus, and a firmer feel to skin and connective tissue are reported occasionally.

On the adverse side, water retention, bloating and puffiness are very commonly reported. Tingling or numbness in the hands and fingers and injection-site reactions are frequently reported. Flushing or a warm head-rush after injecting, fatigue or drowsiness, headache, increased appetite, and higher blood sugar are reported occasionally. Several of those track the known physiology of growth-hormone excess rather than anything peculiar to this molecule.

The documented cautions are these. CJC-1295 has never been approved by the FDA or any major regulator for human use and is sold only as a research chemical; published human evidence is limited to a small number of early pharmacology studies, with no large or long-term trials in healthy adults ^[4]. Immunogenicity — the risk of an immune response to the peptide — was cited among the safety concerns in 2024 FDA briefing materials for the Pharmacy Compounding Advisory Committee, as part of the basis for not recommending CJC-1295 for the 503A compounding bulks list ^[1]. The DAC and no-DAC forms are routinely conflated in marketing and forums despite behaving very differently, and the long duration of the DAC form is precisely what makes that confusion a safety matter rather than a pedantic one ^[7].

Further cautions in the record are mechanism-based rather than trial-derived, and are reported here without a citation number because their supporting sources are not in this digest's reference set: sustained IGF-1 elevation and the theoretical cancer concern it raises; sodium and water retention with nerve-compression effects, which is the likely mechanism behind the commonly reported puffiness and carpal-tunnel-like tingling; reduced insulin sensitivity and raised blood sugar, since growth hormone is glucose-sparing; a discontinued development programme with a patient death frequently cited alongside it, where the public record does not establish causation; and prohibition in sport at all times under WADA Section S2, with established detection methods.

Where it sits on the kinetics map

CJC-1295 is the long end of this desk. It is the only compound here whose extension strategy is a covalent bond, and it holds the longest measured human half-life in the reference set at 5.8 to 8.1 days ^[4].

It is also the compound where the gap between exposure and effect is widest in both directions. IGF-1 stayed above baseline for up to 28 days after repeated dosing — roughly four half-lives past the last injection ^[4] — while pulsatile secretion carried on as normal underneath the sustained signal ^[5].

And it is the only compound here where the name itself is kinetically ambiguous. Semaglutide is semaglutide. CJC-1295 might be a molecule with a multi-day half-life or one with a half-life measured in minutes, depending on whether the linker is present ^[7]. Any claim about how long CJC-1295 lasts is meaningless without that detail attached.