CJC-1295: The DAC Distinction, Albumin Binding, and What the Trials Measured

CJC-1295 is a tetrasubstituted analog of human growth hormone-releasing factor 1-29, engineered at ConjuChem to bind covalently to circulating albumin. That albumin bond is the entire point of the molecule, and it is also the thing most often stripped out by the name as it is used commercially. Laboratories buying under this name are buying one of two different peptides depending on whether the DAC group is present.

What is CJC-1295?

Native hGRF(1-29) has the sequence YADAIFTNSYRKVLGQLSARKLLQDIMSR, amidated at the C terminus. CJC-1295 modifies four positions: D-alanine at position 2, glutamine at 8, alanine at 15, and leucine at 27. Jetté and colleagues at ConjuChem then added a lysine at position 30 carrying an N-epsilon-3-maleimidopropionamide group [1].

That maleimide is the drug affinity complex, or DAC. It reacts with the free thiol on Cys34 of serum albumin, forming a covalent bioconjugate in circulation.

The full molecule is C₁₆₅H₂₆₉N₄₇O₄₆, molecular weight 3647.2 g/mol, CAS 863288-34-0, indexed as PubChem CID 91971820. No regulatory authority has approved it.

CJC-1295 with DAC and CJC-1295 no DAC are different molecules

This is the most consequential fact about the compound and the one most often lost.

The four substitutions at positions 2, 8, 15, and 27 give the peptide resistance to dipeptidyl peptidase-IV, the enzyme that clips native GRF at the N terminus. Those substitutions alone produce the 29-residue peptide sold as CJC-1295 no DAC, which is more accurately called Modified GRF(1-29). It has no maleimide and cannot conjugate to albumin.

CJC-1295 with DAC carries the Lys30 maleimide and does conjugate. The published half-life of roughly six to eight days belongs to that conjugate, not to the peptide backbone [2].

Every study cited below used the DAC form. Searching the literature for “CJC-1295” and applying the results to the no-DAC peptide attributes a pharmacokinetic profile to a molecule that lacks the group responsible for it. The two compounds share a backbone and differ by one residue and one reactive handle, and that handle is what the entire pharmacology rests on.

Mechanism of action

GRF binds the GHRH receptor on pituitary somatotropes and drives synthesis and release of growth hormone. Growth hormone in turn raises IGF-1. Native GRF is useless as a sustained stimulus because plasma enzymes destroy it quickly.

The specific vulnerability is position 2. Kubiak and colleagues showed that DPP-IV hydrolyses Ala2-containing GRFs by cleaving between Ala2 and Asp3. Mouse GRF carries Val2 instead and resists that cleavage.

The same work incubated two bovine GRF analogs in plasma, including [Ala15,Leu27]bGRF(1-29)NH₂. Both converted to their (3-29) fragments [5]. Two of those substitutions match CJC-1295 at positions 15 and 27, which is why the position-2 change carries the protective load.

CJC-1295 addresses both halves of the problem. The tetrasubstitution blocks enzymatic clipping. The maleimide anchors the peptide to albumin, a carrier with a plasma residence time measured in weeks.

Kubiak’s work also carries a caution. Blocking DPP-IV does not make a GRF peptide durable on its own, because trypsin-like and other proteolytic cleavages continue elsewhere in the chain [5]. Albumin conjugation, not the substitutions, is what produces the multi-day half-life.

Jetté and colleagues synthesised three maleimido derivatives of hGRF(1-29) and conjugated them to human serum albumin. All three resisted DPP-IV and remained bioactive in a GH secretion assay in cultured rat anterior pituitary cells [1].

Research findings

Rat pituitary and in vivo rat work

Subcutaneous administration to Sprague-Dawley rats produced acute GH secretion. CJC-1295 gave a fourfold increase in GH area under the curve over two hours compared with unmodified hGRF(1-29). Western blot of plasma from an injected rat showed CJC-1295 immunoreactivity on the band corresponding to serum albumin, appearing at 15 minutes and still present beyond 24 hours [1].

Human pharmacokinetics and pharmacodynamics

Teichman and colleagues ran two randomised, placebo-controlled, double-blind ascending-dose trials in healthy adults aged 21 to 61. A single subcutaneous injection produced dose-dependent increases in mean plasma GH of two- to tenfold lasting six days or more, and IGF-1 increases of 1.5- to threefold lasting nine to eleven days. Estimated half-life was 5.8 to 8.1 days. After repeated doses, mean IGF-1 stayed above baseline for up to 28 days. The trials reported no serious adverse reactions [2].

Whether pulsatility survives

Continuous stimulation of a pulsatile axis raises an obvious question. Ionescu and Frohman sampled blood every 20 minutes across a 12-hour overnight window in healthy men, before and one week after a single injection.

Pulse frequency and pulse magnitude were unchanged. What rose was the trough: basal GH increased 7.5-fold, mean GH by 46%, and IGF-1 by 45%. The authors attributed the IGF-1 rise chiefly to elevated trough levels rather than to altered pulses [3].

Serum protein changes

Sackmann-Sala and colleagues ran two-dimensional gel electrophoresis on sera from 11 healthy young men before and one week after injection, hunting for biomarkers of GH and IGF-1 action. An apolipoprotein A1 isoform and a transthyretin isoform fell. Beta-hemoglobin and two albumin fragment spots rose, one of which tracked linearly with IGF-1 [4].

What the published record does not cover

The CJC-1295 literature is four primary papers, all on the DAC form, all from 2005 to 2009, and the human work is short-duration dose-ranging in healthy volunteers. No published trial covers long-term administration, no study addresses the no-DAC peptide under this name, and the clinical development programme did not continue to approval.

Two further gaps are worth naming. Nothing published characterises what fraction of an administered dose actually conjugates to albumin under real conditions, so the ratio of bound to free peptide in circulation is unmeasured. And because all four papers predate 2010, none uses the high-resolution mass spectrometry now standard for peptide identity work.

The class itself is not short of evidence, which sharpens the contrast. Tesamorelin, a GRF(1-44) analog, carried a GHRH agonist through randomised controlled trials to approval. Secondary analyses of those trials are still being published [6]. That is the benchmark CJC-1295 did not reach.

For a laboratory, that shapes what the compound is good for. It is a well-documented positive control for GHRH receptor activation, and the albumin bioconjugation chemistry is described in enough detail to reproduce [1]. It is not a compound with a deep or current evidence base, and any protocol treating it as one is reading more into four papers than they contain.

Physicochemical properties and handling

Supplied lyophilised, the peptide is stable at low temperature and away from light and moisture. Once in aqueous solution, two degradation routes matter.

The maleimide is a thiol-reactive electrophile. Any free thiol in the buffer competes with the intended target and consumes it. Reducing agents such as DTT or 2-mercaptoethanol are the usual culprits.

Maleimides also hydrolyse at elevated pH to the unreactive maleamic acid. That reaction destroys DAC function. It barely changes the peptide mass, so a mass check alone will not catch it.

Avoid repeated freeze-thaw cycles. Aliquot instead.

Analytical characterization and quality

Peptide identity work rests on accurate mass and sequence confirmation. For a 30-mer at 3647 Da, high-resolution LC-MS gives the intact mass, and MS/MS fragmentation confirms the sequence rather than merely the composition. That distinction matters here, because a deletion or a substitution elsewhere in the chain can leave the total mass close to correct.

Three checks are specific to this molecule:

Confirm the DAC group is present and intact. A no-DAC preparation is roughly 280 Da lighter and is a different product. Hydrolysed maleimide is a further small mass shift and is not visible at all in a purity number.

Confirm the D-alanine at position 2. Standard MS cannot distinguish D-Ala from L-Ala, and the L form is DPP-IV labile. This needs chiral amino acid analysis after hydrolysis.

Confirm net peptide content rather than chromatographic purity alone. Lyophilised material carries water and counter-ion mass, so HPLC area percent overstates how much peptide is in the vial.

Kimera publishes third-party certificates of analysis for every lot in its COA database. More peptide chemistry appears in the peptides category.

The conjugation chemistry in detail

The albumin bond is what makes this molecule work, and the chemistry is worth understanding rather than taking on trust.

Why Cys34

Human serum albumin carries 35 cysteine residues. Disulfide bridges lock 34 of them. Cysteine 34 is the exception, presenting the only free thiol on the protein.

That single reactive site makes albumin a viable conjugation partner in circulation. A maleimide group reacts with thiols selectively and rapidly under physiological conditions, forming a stable thioether bond.

Jetté and colleagues exploited exactly that. They synthesised three maleimido derivatives of human growth hormone-releasing factor 1-29 and conjugated them to albumin. The best performer went forward for development [1]. Western blot analysis of plasma from injected rats showed the compound on the band corresponding to serum albumin within 15 minutes. It remained there beyond 24 hours [1].

Why the peptide needed protecting

The reason for going to this trouble is enzymatic. Dipeptidyl peptidase IV cleaves native growth hormone-releasing hormone rapidly, removing residues from the amino terminus.

The tetrasubstitution addresses this. All three albumin conjugates in the original work showed enhanced in vitro stability against that enzyme [1]. The substitutions serve that purpose rather than receptor affinity.

Two problems therefore get solved by two different features. Amino acid substitution blocks enzymatic degradation. The maleimide extends circulation time by attaching the peptide to a protein with a multi-week half-life.

What the human trials measured

Three clinical studies define what is known in people, and each measured something different.

Pharmacokinetics and dose response

Teichman and colleagues ran two randomised, placebo-controlled, double-blind ascending-dose trials in healthy adults aged 21 to 61. The two trials ran 28 and 49 days [2].

A single subcutaneous injection produced dose-dependent increases in mean plasma growth hormone of two to ten fold, sustained six days or more. Insulin-like growth factor I rose 1.5 to 3 fold across nine to eleven days [2].

The estimated half-life was 5.8 to 8.1 days [2]. After multiple doses, mean insulin-like growth factor I levels stayed above baseline for up to 28 days. The authors described that as evidence of a cumulative effect [2].

No serious adverse reactions appeared. The authors identified 30 and 60 µg/kg as the better-tolerated doses [2].

Whether pulsatility survived

This is the most mechanistically interesting result. Continuous stimulation of a pulsatile axis might reasonably be expected to flatten it.

Ionescu and Frohman sampled blood every 20 minutes across a 12-hour overnight period. Sampling ran before and one week after a single injection [3].

Pulsatility persisted. Neither the frequency nor the magnitude of growth hormone secretory pulses changed [3]. The baseline moved instead. Trough growth hormone levels rose 7.5-fold, contributing to a 46 percent rise in mean levels and a 45 percent rise in insulin-like growth factor I [3].

The authors drew the conclusion that matters. Raising trough levels through continuous stimulation, rather than amplifying pulses, drove the insulin-like growth factor I increase [3]. The rise also failed to correlate with any parameter of growth hormone secretion [3].

Evidence that the receptor arm is sufficient

One animal study addresses a question the human trials cannot, by removing the endogenous ligand entirely.

Alba and colleagues treated GHRH-knockout mice from one week of age for five weeks, dosing 2 µg at intervals of 24, 48 or 72 hours [7]. Placebo-treated knockouts and heterozygous animals served as controls.

Daily dosing normalised body weight and length. Femur and tibia length stayed normal in animals treated every 24 and 48 hours, and relative lean mass and subcutaneous fat mass were normal across all treated groups [7]. Longer intervals produced partial rather than full normalisation [7].

The pituitary finding is worth noting alongside. Treatment increased total pituitary RNA and growth hormone messenger RNA, which the authors attributed to somatotroph proliferation and confirmed immunohistochemically [7].

That result establishes something the human work does not. In an animal with no endogenous GHRH at all, the analogue alone restored normal growth, which places the effect squarely at the receptor rather than at some permissive interaction with residual native hormone.

Downstream protein changes

Sackmann-Sala and colleagues took serum from eleven healthy young men, before and one week after injection. They ran two-dimensional gel electrophoresis to look for markers of axis activation [4].

Two protein spots decreased after treatment. They corresponded to isoforms of apolipoprotein A1 and transthyretin. Three others increased, among them beta-haemoglobin and albumin fragments [4]. One spot showed a linear relationship with insulin-like growth factor I levels [4].

That work matters less for what it found than for why anyone attempted it. Existing markers of growth hormone action vary substantially between individuals. They reliably predict neither physiological effect nor detection of abuse [4].

Two routes to the same axis

Discussions frequently place CJC-1295 alongside compounds that raise growth hormone by a different route. The distinction is worth keeping clear.

Both routes converge on pituitary somatotrophs. Both preserve the pulsatile pattern that distinguishes secretagogue approaches from exogenous hormone administration [12].

Kimera lists MK-677 (Ibutamoren) separately for that reason, since it acts at the other receptor entirely.

They are not interchangeable experimentally. A GHRH analogue tests the GHRH receptor arm specifically. Any study attributing an effect to that receptor needs a compound acting there rather than at the ghrelin receptor.

Detection and the analytical problem

The doping-control literature contains the most rigorous analytical work on this compound, and it identifies a specific difficulty.

Timms and colleagues stated the problem plainly. Three features make conjugated CJC-1295 difficult to detect in blood by mass spectrometry: low abundance, high molecular weight once bound, and conjugation to a range of different protein substrates [10].

That last point is the awkward one. The compound does not exist as a single species in circulation. It exists as a family of conjugates, and that defeats methods expecting one analyte at one mass.

Their solution combined immunoaffinity capture with tryptic digestion before liquid chromatography tandem mass spectrometry. It reached detection down to 180 pg/mL in equine plasma [10]. Thomas and colleagues developed a comparable immunoaffinity approach covering twelve prohibited peptides including this one, at low picogram per millilitre limits [9].

The most directly relevant study for identity purposes is more recent. Memdouh and colleagues investigated in vitro metabolism and detection of four larger GHRH analogues. Their list runs sermorelin, tesamorelin, CJC-1295, and CJC-1295 with drug affinity complex [8].

Read that list carefully. A validated anti-doping method treats the two forms as separate analytes requiring separate reference materials. The analytical literature therefore confirms what the naming convention obscures.

That study identified nineteen major in vitro metabolites. The authors synthesised and characterised them in house as reference materials, achieving detection limits generally at or below 1 ng/mL [8].

How the compound circulates outside research

One study documents how the compound circulates outside research settings, and it is informative about why identity confusion persists.

Van Hout and Hearne analysed 23 discussion threads on bodybuilding forums concerning female use. A systematic search returned 96 relevant sites [11].

Their relevant finding concerns information quality rather than effects. They describe communal online folk pharmacology driving use. Participants were well versed in poly-supplementation, yet uncertain about dosing, cycling and long-term consequences [11].

Two forms differ in half-life by orders of magnitude. A community discussing both under one name produces exactly the confusion this article opens with.

Common misclassifications

Four errors recur.

Suppliers treat the DAC and no-DAC forms as the same compound at different strengths. They differ by the maleimide group producing albumin binding, and therefore by their entire pharmacokinetic profile [1][8].

Summaries apply trial data to the no-DAC form. Every human trial cited here used the albumin-binding compound [2][3][4].

Copy describes the compound as a growth hormone. It is a releasing-hormone analogue acting on pituitary somatotrophs, and it preserves pulsatile secretion rather than overriding it [3].

Readers assume detection is straightforward. Conjugation to multiple protein substrates complicates direct mass spectrometric detection, and validated methods require immunoaffinity capture [9][10].

Experimental design considerations

State which form the study used, specifying the maleimide as present or absent. This is the single most important methodological detail for this compound.

Sample over days, not hours. The half-life is measured in days, and effects on insulin-like growth factor I persist for weeks after repeated dosing [2].

Measure trough as well as peak. The mechanism operates by raising baseline secretion rather than amplifying pulses, and a peak-only design will understate it [3].

Plan for conjugate heterogeneity in any analytical work. The compound binds several plasma proteins, so a method expecting one species will underestimate total exposure [10].

Include a GHRH receptor comparator rather than a ghrelin receptor one if the receptor arm is the question [12].

Frequently asked questions

What is CJC-1295? A tetrasubstituted analog of hGRF(1-29) bearing a maleimide group that conjugates covalently to serum albumin. Kimera supplies it as a laboratory research material.

What does DAC mean? Drug affinity complex. The term refers to the N-epsilon-3-maleimidopropionamide on Lys30 that reacts with Cys34 of albumin [1].

Is CJC-1295 no DAC the same compound? No. That product is Modified GRF(1-29), the 29-residue peptide without the maleimide. Lacking the reactive handle, it cannot bind albumin, and none of the published CJC-1295 pharmacokinetics applies to it.

Does continuous GHRH stimulation flatten GH pulses? Not in the reported human data. Pulse frequency and magnitude were preserved; trough GH rose 7.5-fold [3].

Why do the four substitutions matter? Position 2 does the protective work. DPP-IV cleaves Ala2-containing GRFs between Ala2 and Asp3, and the D-alanine blocks it [5]. Other proteases still act elsewhere, so the substitutions alone do not confer a long half-life [5].

How much CJC-1295 literature exists compared with the class? Four papers on CJC-1295 against a GHRH-analog class that carried tesamorelin through randomised trials to approval [6].

Can standard mass spectrometry confirm the D-alanine? No. D-Ala and L-Ala have identical mass. Chiral amino acid analysis after hydrolysis is required.

How much literature exists? Four primary papers, published between 2005 and 2009, all using the DAC form.

References

1. Jetté L, Léger R, Thibaudeau K, et al. 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. 2005;146(7):3052-3058. PMID 15817669. DOI
2. 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. PMID 16352683. DOI
3. 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. PMID 17018654. DOI
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. PMID 19386527. DOI
5. Kubiak TM, Martin RA, Leone JW, Cleary DL. Metabolism of mouse growth hormone-releasing factor, mGRF(1-42)OH, and selected analogs from the bovine GRF series in mouse and bovine plasma in vitro. Pept Res. 1994;7(3):153-161. PMID 7915920

6. Adrian S, Scherzinger A, Sanyal A, et al. The Growth Hormone Releasing Hormone Analogue, Tesamorelin, Decreases Muscle Fat and Increases Muscle Area in Adults with HIV. J Frailty Aging. 2019;8(3):154-159. PMID 31237318. DOI

7. Alba M, Fintini D, Sagazio A, et al. 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. PMID 16822960. DOI

8. Memdouh S, Gavrilović I, Ng K, Cowan D, Abbate V. Advances in the detection of growth hormone releasing hormone synthetic analogs. Drug Test Anal. 2021;13(11-12):1871-1887. PMID 34665524. DOI
9. Thomas A, Schänzer W, Delahaut P, Thevis M. Immunoaffinity purification of peptide hormones prior to liquid chromatography-mass spectrometry in doping controls. Methods. 2012;56(2):230-235. PMID 21871962. DOI
10. Timms M, Ganio K, Steel R. A method for confirming CJC-1295 abuse in equine plasma samples by LC-MS/MS. Drug Test Anal. 2019;11(8):1248-1257. PMID 30938069. DOI
11. Van Hout MC, Hearne E. Netnography of female use of the synthetic growth hormone CJC-1295: pulses and potions. Subst Use Misuse. 2016;51(1):73-84. PMID 26771670. DOI
12. Smith RG. Development of growth hormone secretagogues. Endocr Rev. 2005;26(3):346-360. PMID 15814848. DOI

CJC-1295 is sold for laboratory research use only. Not for human consumption, nor medical, veterinary, or household uses.

Literature retrieved from PubMed.