CJC-1295 with DAC and CJC-1295 without DAC are the same base GHRH analog sequence modified at the C-terminus in two different ways, and the two modifications produce very different pharmacokinetic profiles. The no-DAC form has a circulating half-life of roughly 30 minutes and produces a pulsatile GH release pattern. The DAC form binds serum albumin through its Drug Affinity Complex modification, which stretches the half-life to 6 to 8 days and produces sustained GH elevation. The distinction is mechanistically real, and the two forms show up in different research contexts for different reasons.
This article covers what the modification does, how the two release patterns differ, which form appears where in the published literature, and what the literature does not settle.
What the DAC Modification Does
The Drug Affinity Complex modification appended to CJC-1295 with DAC consists of a lysine derivative coupled through a maleimide-functionalized linker to the C-terminus of the peptide. That lysine derivative carries a reactive thioester group, which forms a covalent bond with the free thiol of cysteine-34 on circulating serum albumin.
The effect is a large extension of circulating half-life. Native GHRH(1-29) is cleaved by dipeptidyl peptidase-IV within minutes of entering circulation, which makes it pharmacologically transient. CJC-1295 without DAC addresses that by substituting a DPP-IV-resistant amino acid at position 8, the Ala8/Gln8 modification, which extends half-life to roughly 30 minutes. Adding the DAC modification extends it much further. Bound to albumin, the peptide is shielded from renal filtration and from proteolytic degradation, reaching a half-life of 6 to 8 days in research models.
The albumin-bound form stays biologically active. It dissociates gradually, releasing functional peptide into circulation continuously over days. That is what produces the sustained GH elevation profile characteristic of the DAC form.
Molecular specifications for comparison:
| Parameter | CJC-1295 (no DAC) | CJC-1295 (with DAC) |
|---|---|---|
| Molecular weight | ~3367.97 g/mol | ~3647.28 g/mol |
| Half-life | ~30 minutes | 6 to 8 days |
| GH release pattern | Pulsatile | Sustained |
| Albumin binding | No | Yes, covalent via Cys-34 |
| DPP-IV resistance | Yes, Ala8 modification | Yes |
Published GHRH analog research extends from the foundational work of Guillemin and Vale through the modern structural analog literature. CJC-1295 specifically was investigated for its improved stability relative to native GHRH(1-29), which is degraded within minutes by dipeptidyl peptidase-IV (DPP-IV). The Ala8 substitution in CJC-1295 confers resistance to DPP-IV cleavage, extending its functional half-life beyond that of unmodified GHRH.
Pulsatile Versus Sustained GH Release
This is where the two forms diverge most for research purposes.
Endogenous GH secretion is pulsatile. The hypothalamus releases GHRH in discrete bursts, and those bursts trigger corresponding GH pulses from pituitary somatotrophs. The pulses occur roughly 8 to 12 times across a 24-hour period in humans, with the largest ones during slow-wave sleep. Between pulses, GH levels sit near zero.
That pattern is not incidental. GH receptor downregulation occurs under continuous GH exposure, and the pulsatile pattern is what preserves receptor sensitivity and downstream IGF-1 production.
CJC-1295 without DAC produces a GH pulse that models the endogenous pattern. In research models it triggers a discrete secretory event that returns to baseline within 1 to 2 hours. That mirrors physiological GHRH pulsatility, which makes it the more biologically authentic model for studying GH axis dynamics.
CJC-1295 with DAC produces continuous, sustained GH elevation across days. That is not a physiological pattern. It is closer to exogenous GH administration than to endogenous GHRH signaling. The sustained elevation does produce measurable effects on GH-dependent outcomes such as IGF-1, lean tissue and fat metabolism in animal models, which is why the DAC form turns up in studies focused on those downstream outcomes rather than on GH axis dynamics themselves.
The research question decides which form fits. For work on GH axis pulsatility, somatotroph response kinetics, or the role of pulsatile versus tonic GH secretion, the no-DAC form is the appropriate tool. For work where the variable is a downstream outcome that needs sustained GH elevation to become measurable inside a practical experimental window, the DAC form may be more useful.
Which Form Appears More in the Literature, and Why
A PubMed search for CJC-1295 returns a substantially larger body of work referencing the DAC form. Part of that is historical. The DAC formulation drew early clinical attention because the extended half-life made it attractive for proof-of-concept studies on GHRH analog biology in human subjects. The Teichman et al. 2006 paper in the Journal of Clinical Endocrinology and Metabolism, which characterized GH and IGF-1 responses to CJC-1295, used the DAC formulation and became a foundational citation.
The trend has since shifted. As investigators moved from pharmacokinetic characterization toward mechanistic work on GH axis biology, the pulsatile form became more relevant. CJC-1295 without DAC, sometimes called modified GRF(1-29) or Mod GRF 1-29 in older literature, appears more often in studies examining GH pulse architecture, somatotroph regulation, and combined secretagogue models.
In research combining CJC-1295 with Ipamorelin, the no-DAC form is overwhelmingly the one used. The rationale is half-life matching. Ipamorelin has a roughly 2-hour half-life, and pairing it with a similarly short-acting GHRH analog produces a synchronized dual-pathway pulse. Pairing Ipamorelin with the DAC form creates a pharmacokinetic mismatch instead, because the DAC form supplies continuous background GHRH signaling while Ipamorelin supplies intermittent GHS-R1a activation. Both pairings appear in the literature. The mechanistic rationale favors the matched one.
What the Literature Does Not Settle
Most of the published CJC-1295 record is pharmacokinetic and endocrine. It describes what happens to circulating GH and IGF-1. It says considerably less about what follows from that.
Three gaps are worth naming. First, the two forms have rarely been compared head to head in the same study under the same conditions, so most of the comparison above is assembled across studies rather than drawn from one. Second, the long-term consequences of sustained versus pulsatile GH elevation are not resolved, and receptor sensitivity over extended exposure is exactly the kind of question a 6 to 8 day half-life makes harder to study cleanly. Third, the combined secretagogue literature is thinner than its popularity suggests, and a good part of what circulates about it is not peer-reviewed.
None of that makes the mechanism uncertain. The albumin binding, the half-life difference and the release patterns are well characterized. It means the downstream picture is less settled than the upstream one, and it is worth reading any strong claim about the DAC form with that gap in view.
Frequently Asked Questions
Q: What is the main difference between CJC-1295 with and without DAC?
A: The Drug Affinity Complex modification causes CJC-1295 to bind serum albumin covalently, which extends its half-life from roughly 30 minutes to 6 to 8 days. Without DAC, CJC-1295 produces a short pulsatile GH release. With DAC, it produces sustained GH elevation across days.
Q: Which form of CJC-1295 is more physiologically accurate?
A: CJC-1295 without DAC is more physiologically relevant for research on GH axis dynamics, because it produces pulsatile GH release that mirrors endogenous GHRH biology. The DAC form produces continuous GH elevation, which does not reflect normal GH secretion patterns.
Q: How does the half-life of CJC-1295 without DAC affect research design?
A: A roughly 30-minute half-life means GH elevation returns to baseline within 1 to 2 hours. That makes the no-DAC form appropriate for time-resolved GH pulse studies, and for combination models using similarly short-acting compounds such as Ipamorelin.
Q: Why is CJC-1295 without DAC the form paired with Ipamorelin in the literature?
A: The two have compatible pharmacokinetic profiles. Both are short-acting, and both produce GH pulses that resolve within 2 to 3 hours. The pairing activates GH release through two distinct receptor pathways, GHRH-R and GHS-R1a, and published rodent models report a combined effect greater than either alone. The matched half-lives are what produce a coordinated pulse rather than a mismatched one.
Q: Which CJC-1295 form appears more in the published research literature?
A: Both appear. The DAC form received more attention in early clinical pharmacokinetic work, including the Teichman et al. 2006 paper in JCEM. The no-DAC form appears more commonly in mechanistic research on GH pulsatility and in combined secretagogue models. The no-DAC form is generally preferred when pulsatile GH dynamics are the variable of interest.
Where to Read Further
Etched Research does not carry CJC-1295 in either form. The growth hormone signaling compound in the catalog is Ipamorelin, the GHS-R1a-side compound in the pairing described above.
Research summaries for both compounds are in the library: CJC-1295 and Ipamorelin. The full Research Library covers the rest of the catalog.
All products mentioned are for research use only. Not for human consumption.
New reports, new research.
We send a note when a new lab report is posted or a compound comes back in stock, plus a short list of new research pages in any month we publish some. Never more than one email a week, and nothing else.
For Research Use Only. Not for human consumption. Etched Research supplies compounds for laboratory and research use only. Nothing on this page is medical advice, a health claim, or a recommendation to use.