CJC-1295 With DAC vs No DAC: What Changes at the Molecular Level?
CJC-1295 with DAC and no DAC share one 29-residue backbone and the same four amino acid substitutions. The DAC form adds a single lysine carrying a maleimidopropionyl group, raising the calculated mass from about 3,368 to 3,647 Da, a difference of 279 Da. That group bonds to albumin, shifting the half-life from a reported 30 minutes to 5.8–8.1 days in a healthy-adult study, while GH pulsatility was preserved and trough GH rose 7.5-fold.
Search for CJC-1295, and you will find two compounds that share a name, a backbone, and most of a sequence, yet behave nothing alike in an experiment. The label separates them with a short suffix, and that suffix carries most of the science. For anyone working with research peptides in this family, the real question behind CJC-1295 with DAC vs. no DAC is what the suffix physically adds to the molecule, and what it leaves untouched.
Note: This content is provided for educational purposes within a research context only. It does not promote or suggest the use of peptides for personal, medical, or non-research applications.
Why Does One Name Cover Two Different Molecules?
CJC-1295 started as a code for one specific compound. The 2005 paper that identified it describes a tetrasubstituted form of human GHRH(1–29) with a lysine added at the C-terminus, carrying a maleimide group built to bind albumin (Jetté et al., 2005). That is the molecule later tested in healthy adults (Teichman et al., 2006) and sold today as CJC-1295 with DAC. DAC stands for Drug Affinity Complex. The plainer relative, CJC-1295 no DAC, keeps the same four-substitution backbone without the added lysine, which is why it also goes by modified GRF(1-29).
| Feature | CJC-1295 No DAC | CJC-1295 With DAC |
|---|---|---|
| Also called | Modified GRF(1-29) | CJC-1295 DAC, DAC:GRF |
| Backbone | GHRH(1-29) with four substitutions | Same backbone, same four substitutions |
| Added group | None | Lysine with a maleimidopropionyl group at the C-terminus |
| Formula | C152H252N44O42 | C165H269N47O46 |
| Average mass | About 3,368 Da | About 3,647 Da |
| Albumin binding | No | Yes, at Cys34 |
| Reported half-life | About 30 minutes | 5.8 to 8.1 days |
Both belong to the group of growth hormone peptides that act through the GHRH receptor, so papers, data sheets, and listings often use the name without saying which form they mean.
What Does the DAC Actually Add?
The formula difference between the two forms is C13H17N3O4, which works out to 279.3 Da. That is one lysine residue (128.2 Da) plus a maleimidopropionyl group (151.1 Da) attached to its side chain. The entire mass difference between the two forms is one extra lysine and one reactive group. Every other residue is identical.
Maleimides bind free thiols, and in the 2005 design the group was placed so that, after injection, it bonds to the free thiol on Cys34 of serum albumin (Jetté et al., 2005). In rats, a CJC-1295-reactive band appeared at the albumin position within 15 minutes and stayed beyond 24 hours, and the compound was still present in plasma beyond 72 hours. Ionescu and Frohman later in 2006 described it as binding permanently to endogenous albumin after injection.
The group also affects how the compound is prepared. Free thiols compete with albumin for the maleimide, so reagents such as DTT, beta-mercaptoethanol, cysteine, and glutathione do not belong in reconstitution or assay buffers for the DAC form. The no-DAC form has no maleimide, so its structure imposes no such restriction. Otherwise, the two are handled alike: both go into a neutral diluent and share the same storage conditions.
What Do the Four Shared Substitutions Do?
Both forms carry the same four changes relative to native GHRH(1-29), the sequence behind sermorelin:
- position 2: alanine replaced by D-alanine
- position 8: asparagine replaced by glutamine
- position 15: glycine replaced by alanine
- position 27: methionine replaced by leucine
Small edits to peptide structure can change both stability and receptor behavior, and these four are all small edits. Position 2 sits at the N-terminal end where DPP-4 acts, and swapping asparagine for glutamine at position 8 removes a residue prone to deamidation. The methionine-to-leucine change at position 27 removes a sulfur-containing residue that oxidizes easily. Deamidation and oxidation are two of the usual sources of peptide impurities, so these swaps suit a compound that has to stay intact. The glycine-to-alanine change at position 15 is less often explained, so no reason is assigned to it here.
Because both forms carry all four, the substitutions can account for why no DAC outlasts sermorelin, at about 30 minutes against 11 to 12. They cannot account for the gap between the two forms. That belongs to the DAC.
How Different Is the Half-Life?
Native GHRH lasts about 2 minutes, sermorelin 11 to 12, and the no-DAC form about 30. The DAC form sits in a different range entirely: 5.8 to 8.1 days in healthy adults (Teichman et al., 2006).
That figure comes from two randomized, placebo-controlled, double-blind ascending-dose trials lasting 28 and 49 days, in healthy adults aged 21 to 61. After a single injection, mean GH rose 2- to 10-fold for six days or more and mean IGF-I rose 1.5- to 3-fold for 9 to 11 days. After repeated doses, IGF-I stayed above baseline for up to 28 days. Those numbers describe one study population, and any peptide half-life depends on the species, route, and assay used to measure it.
What Does CJC-1295 With DAC vs No DAC Change in Study Design?
The no-DAC form gives a short, defined signal, which suits experiments built around pulsatile GH release. The DAC form keeps the GHRH receptor engaged for several days, which suits long observation windows where repeated short exposures would be impractical.
An obvious worry is that continuous stimulation flattens the pulses. In a study of healthy men, blood was sampled every 20 minutes over 12 hours, before and one week after a single injection of the DAC form. GH pulsatility was preserved: pulse frequency and magnitude were unchanged, while trough GH rose 7.5-fold, mean GH rose 46%, and IGF-I rose 45% (Ionescu & Frohman, 2006). The authors point to the trough increase as important to the IGF-I response.
Both papers describe the long-acting form, so none of these numbers should be carried over to no DAC.
How Can the Two Forms Be Told Apart on a Certificate of Analysis?
Because the two forms differ by 279 Da, the identity check on a certificate of analysis separates them cleanly. Mass spectrometry reports the molecular mass of the main peak, so a mass of about 3,368 Da points to the no-DAC form and about 3,647 Da to the DAC form. A purity figure alone cannot do this: two vials can both read 99% by HPLC and still be different molecules. The batch number on the certificate should match the vial, and the mass should match the form the label names.
Is Either Form of CJC-1295 an Approved Medicine?
No. Neither form is an FDA-approved drug, and both are supplied for research use only, a label that describes intended use and does not mean the FDA has evaluated the product. The FDA’s page on bulk drug substances for compounding lists CJC-1295 and cites immunogenicity risk, peptide-related impurities, limited clinical data, and reported adverse events including increased heart rate (U.S. Food and Drug Administration, 2026). The trials described above were research studies in healthy adults, and they do not amount to approval for any use.
Why Do the Two Blends Differ Too?
The same split runs through the blends, so the choice between CJC-1295 with DAC vs no DAC carries over to what each blend can test. CJC-1295 with DAC/Ipamorelin pairs a multi-day GHRH signal with discrete ghrelin-receptor activation, while CJC-1295 no DAC/Ipamorelin keeps both signals short. Comparing the two isolates the effect of GHRH receptor half-life.
Ipamorelin is the same in both: a five-residue ghrelin mimetic of about 712 Da that works through the ghrelin pathway rather than the GHRH receptor. Only the GHRH side changes, by 279 Da and by days against minutes. That is why the two blends answer different questions and are not interchangeable.
The Molecular Difference in One Attached Group
CJC-1295 with DAC vs no DAC comes down to one lysine and one maleimide group, 279 Da in total, on a backbone both forms share. That group explains the albumin binding, the multi-day persistence, the thiol-free preparation, and the different study designs each form supports. When a paper, a label, or a certificate of analysis says CJC-1295, the first thing to check is which of the two it describes.
References
Ionescu, M., & Frohman, L. A. (2006). Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. The Journal of Clinical Endocrinology & Metabolism, 91(12), 4792–4797. https://doi.org/10.1210/jc.2006-1702
Jetté, L., Léger, R., Thibaudeau, K., Benquet, C., Robitaille, M., Pellerin, I., Paradis, V., van Wyk, P., Pham, K., & Bridon, D. P. (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. https://doi.org/10.1210/en.2004-1286
Teichman, S. L., Neale, A., Lawrence, B., Gagnon, C., Castaigne, J.-P., & Frohman, L. A. (2006). Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of growth hormone-releasing hormone, in healthy adults. The Journal of Clinical Endocrinology & Metabolism, 91(3), 799–805. https://doi.org/10.1210/jc.2005-1536
U.S. Food and Drug Administration. (2026, April 22). Certain bulk drug substances for use in compounding that may present significant safety risks. https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
Frequently Asked Questions
Both forms share the same 29-residue GHRH backbone and four amino acid substitutions. The DAC form adds one lysine carrying a maleimidopropionyl group, which bonds to albumin at Cys34. That raises the calculated mass by 279 Da and extends the half-life from a reported 30 minutes to 5.8–8.1 days in a healthy-adult study (Teichman et al., 2006).
DAC stands for Drug Affinity Complex. In CJC-1295 it is a maleimidopropionyl group on a C-terminal lysine, designed to bond to the free thiol on Cys34 of serum albumin (Jetté et al., 2005).
In common usage, yes: both names refer to the 29-residue GHRH(1-29) backbone with the same four substitutions and no added lysine. In the original literature, however, “CJC-1295” refers to the albumin-binding form, so it is worth checking which version a paper or label means.
In a study of healthy adults, the estimated half-life was 5.8–8.1 days. After a single injection, mean GH was raised 2- to 10-fold for six days or more and mean IGF-I 1.5- to 3-fold for 9–11 days (Teichman et al., 2006). These values come from one study population and method.
In healthy men sampled every 20 minutes over 12 hours, GH pulsatility was preserved one week after a single injection: pulse frequency and magnitude were unchanged, while trough GH rose 7.5-fold (Ionescu & Frohman, 2006).
Neither is better in general; the choice follows the experiment. The no-DAC form gives a short, defined signal for studies built around pulses, while the DAC form keeps the GHRH receptor engaged for days, which suits long observation windows. The two are not interchangeable, and data from one should not be applied to the other.
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