This article is provided for educational and informational purposes only. All compounds discussed are analytical-grade biochemical reference standards supplied strictly for laboratory and research use. Vitro Labs products are not for human or animal consumption.
CJC-1295 comes in two forms that look almost identical on a structure diagram but behave like completely different molecules in research models. One clears the bloodstream in about half an hour. The other sticks around for a week or more.
That difference is the whole story. It comes from a tiny chemical handle called DAC, short for Drug Affinity Complex, which was first described by Jetté and colleagues at ConjuChem in 2005 (PMID: 16037509). They added a small reactive group to the end of a modified GHRH compound that lets it latch onto serum albumin, the most abundant protein floating in blood plasma. Once bound, the compound is shielded from the enzymes that would normally chew it up, and its half-life jumps from minutes to days. Teichman and colleagues then measured this directly in healthy research subjects and reported half-life values in the 5.8 to 8.1 day range for the DAC-modified version (PMID: 16940447).
For researchers running protocols on the CJC-1295 + Ipamorelin blend, this distinction is not academic. The DAC modification fundamentally changes how the compound reaches its target receptor, how growth hormone pulses are shaped downstream, and which kinds of experimental questions the compound is suited to answer. This guide reviews the chemistry, the half-life data, the receptor pharmacology, and the practical handling considerations for both forms. for laboratory research use only.
CJC-1295 is a synthetic analog of growth-hormone-releasing hormone, the 44-amino-acid compound produced by the hypothalamus that tells the pituitary gland when to release growth hormone. The native GHRH molecule is fragile. Plasma enzymes. particularly dipeptidyl peptidase-IV. clip it apart within minutes of release. Researchers studying the GHRH-receptor pathway needed a more durable molecule to work with, and that is what CJC-1295 was designed to provide.
CJC-1295 is based on the first 29 amino acids of native GHRH. the fragment known as GRF(1-29), or sermorelin, which retains the full biological activity of the parent hormone. Four amino acid substitutions are layered onto this backbone to protect it from proteolytic cleavage. The result is a compound that resists enzymatic degradation far better than native GHRH but still binds and activates the same receptor.
The compound “CJC-1295” actually refers to two related but distinct molecules: one with the DAC linker attached, one without. In the research literature and in supplier catalogs, the convention is inconsistent. sometimes “CJC-1295” means the DAC version by default and the unmodified form is called “Modified GRF(1-29)” or “CJC-1295 No DAC,” sometimes the reverse. For this article, “with DAC” and “without DAC” are stated explicitly every time the distinction matters.
| Property | CJC-1295 Without DAC | CJC-1295 With DAC |
|---|---|---|
| Backbone | Modified GRF(1-29) | Modified GRF(1-29) |
| DAC linker | No | Yes (maleimidopropionic acid) |
| Albumin binding | No | Yes (covalent, via Cys34) |
| Reported half-life | ~30 minutes | 5.8–8.1 days (PMID: 16940447) |
| Receptor activation profile | Pulsatile, short | Continuous, sustained |
| Common research alias | Modified GRF(1-29), CJC-1295 No DAC | CJC-1295 DAC |
DAC stands for Drug Affinity Complex. It is not a separate molecule that travels with the compound. it is a chemical handle bolted onto one end of the compound that lets the compound attach itself to a much larger protein already circulating in blood.
Serum albumin is the most abundant protein in blood plasma. It is large, long-lived, and present in massive quantities. its half-life is roughly 19 days. Attaching a small compound to a large protein allows the small compound to inherit the long circulation time of the carrier protein. That is the entire trick behind DAC.
The specific chemistry, described in detail by Jetté and colleagues (PMID: 16037509), uses a small reactive group called maleimidopropionic acid. This linker is attached to the C-terminus of the compound. Maleimide groups are notorious for one thing: they react quickly and specifically with free thiol (–SH) groups. Serum albumin happens to have exactly one free thiol, on the amino acid cysteine at position 34. The linker latches onto that cysteine, forming a stable covalent bond.
Once attached, the compound rides along with albumin wherever albumin goes. Plasma enzymes that would normally cleave the bare compound have a much harder time getting to it. The kidneys, which filter small compounds out of circulation rapidly, do not filter albumin-bound molecules nearly as efficiently. The compound is also released slowly from the albumin pool over time, so a steady low concentration of biologically active CJC-1295 stays available to the GHRH receptor.
This is where the chemistry translates into a concrete, measurable difference researchers care about.
The unmodified compound is functionally similar to native GHRH in its clearance behavior. Half-life in research models is approximately 30 minutes. That is long enough for a sharp burst of receptor activation followed by a return to baseline within an hour or two.
Teichman and colleagues (2006) measured this directly in a phase-1 study of healthy research subjects (PMID: 16940447). They reported a terminal half-life of 5.8 to 8.1 days, depending on dose and individual variability. Plasma concentrations of growth hormone remained elevated above baseline for up to 6 days after a single administration. That is a roughly 300-fold extension of half-life compared to the no-DAC form.
Both forms of CJC-1295 bind the same target: the growth-hormone-releasing-hormone receptor (GHRH-R), a G-protein-coupled receptor expressed primarily on somatotroph cells in the anterior pituitary gland.
When GHRH (or a GHRH analog like CJC-1295) binds the receptor, the receptor activates a G-protein on the inside of the cell membrane. This triggers an enzyme called adenylyl cyclase to produce cyclic AMP, which in turn activates protein kinase A (PKA). PKA then phosphorylates downstream proteins that trigger the synthesis and release of growth hormone from secretory granules inside the somatotroph.
Mayo and colleagues (1995) characterized this signaling cascade in detail, working with cloned GHRH receptors expressed in cell culture systems. They showed that GHRH binding produces a dose-dependent rise in intracellular cAMP within minutes, and that the cAMP elevation is what drives growth hormone gene transcription and secretory granule release downstream. establishing the molecular framework for understanding how all GHRH analogs, including CJC-1295, work at the receptor level (PMID: 7575073).
Both forms of CJC-1295 show high affinity for the GHRH receptor. The pharmacological difference between them is not in receptor binding strength. it is in receptor occupancy over time. No-DAC binds, signals, dissociates, and is cleared within an hour. DAC keeps a low concentration of free compound circulating for days, which means the receptor is exposed to low-level continuous stimulation rather than a sharp pulse.
This is the most important practical difference between the two forms for research design.
Native growth hormone secretion is pulsatile. The body releases GH in sharp bursts roughly every 3 to 4 hours during sleep, with smaller pulses during the day. This pulse pattern is not incidental. it is encoded into how downstream tissues respond. The growth hormone receptor, the IGF-1 axis, and the transcriptional programs in liver and muscle are tuned to read pulse frequency and amplitude as signals.
CJC-1295 without DAC, because it clears quickly, produces a sharp burst of GHRH-receptor activation followed by a return to baseline. This mimics the natural pulse architecture. Multiple administrations across a day can produce a series of pulses that approximate normal physiology.
CJC-1295 with DAC produces sustained, low-level GHRH-receptor activation over days. Ionescu and Frohman (2006) studied exactly this question. what happens to growth hormone secretion when the GHRH receptor is exposed to continuous rather than pulsatile stimulation (PMID: 16868048). They reported that continuous CJC-1295-with-DAC administration in healthy research subjects elevated baseline growth hormone and IGF-1 levels but blunted the normal pulse pattern.
The downstream signaling consequences of pulsatile versus tonic GH exposure are non-trivial, as Sackmann-Sala and colleagues (2009) showed in detail when they characterized how pulse shape determines STAT5 activation patterns and hepatic gene expression profiles in mouse models (PMID: 19819961).
“Continuous administration of [CJC-1295 with DAC] produced sustained increases in mean growth hormone and IGF-1 levels but altered the normal pulse pattern of growth hormone secretion.”
, Ionescu and Frohman (2006), PMID: 16868048
Once growth hormone is released into circulation, it binds the growth hormone receptor on target tissues. primarily liver, muscle, adipose, and bone. The receptor activates the JAK2/STAT5 signaling cascade, which drives transcription of downstream genes including IGF-1.
IGF-1 is largely produced in the liver and circulates with a much longer half-life than growth hormone itself. It mediates many of the systemic effects attributed to growth hormone. The relationship between pulse pattern and IGF-1 production is complex: the liver appears to integrate growth hormone exposure over time, but the transcriptional response is shaped by pulse amplitude and frequency, not just total area-under-the-curve.
Sackmann-Sala’s team examined this in mouse hepatocyte models and showed that pulsatile GH stimulation produced distinct patterns of STAT5 phosphorylation and downstream gene activation compared to continuous stimulation (PMID: 19819961). For researchers designing experiments around IGF-1 dynamics, the choice between CJC-1295 with DAC and without DAC is the choice between two fundamentally different stimulation patterns.
Vitro supplies CJC-1295 paired with ipamorelin as a blend. The pairing is not arbitrary. it reflects how the two compounds are most often studied in the GH-secretagogue research literature.
CJC-1295 activates the GHRH receptor. Ipamorelin activates a different receptor entirely. the growth hormone secretagogue receptor (GHS-R1a), which natively binds the gut hormone ghrelin. Both receptors are expressed on the same pituitary somatotroph cells, and both trigger growth hormone release, but they do so through different intracellular signaling cascades.
When the two pathways are activated simultaneously, the growth hormone release response is greater than either compound alone. The pituitary integrates both signals, and the result is a more substantial GH pulse than either GHRH-pathway or ghrelin-pathway activation alone produces.
Raun and colleagues (1998) characterized ipamorelin as a 5-amino-acid compound ghrelin mimetic with unusual selectivity (PMID: 9849822). Unlike earlier ghrelin-pathway compounds (GHRP-6, GHRP-2, hexarelin), ipamorelin does not measurably release prolactin or ACTH at GH-releasing doses in research models. This makes it a clean pairing partner: the experimental signal can be attributed more cleanly to the GH axis without confounding from other pituitary hormone responses.
CJC-1295 is not the only synthetic GHRH analog used in research. Three others appear frequently in the literature, and the differences between them matter for experimental design.
Sermorelin is the unmodified 1-29 fragment of native GHRH. the same backbone CJC-1295 is built on, but without the four protective amino acid substitutions and without the DAC linker. Its half-life is roughly 10 to 20 minutes in research models, even shorter than CJC-1295 without DAC. Sermorelin produces the sharpest, briefest GHRH-receptor activation of the GHRH analog family. Researchers studying acute GH pulse architecture often select it for this reason.
Tesamorelin is GRF(1-44) with a trans-3-hexenoyl group attached to the N-terminus. The modification protects against DPP-IV cleavage and extends half-life to roughly 25 to 40 minutes. comparable to CJC-1295 without DAC. Tesamorelin is the only GHRH analog with an FDA-approved indication in any context (HIV-associated lipodystrophy under the brand name Egrifta), which means more clinical pharmacology data exists for it than for any other analog.
Researchers studying GHRH-receptor pharmacology often use tesamorelin as a reference comparator. See Vitro’s Tesamorelin mechanism research guide for a deeper look at the receptor pathway.
CJC-1295 without DAC sits between sermorelin and tesamorelin on the half-life spectrum. longer than sermorelin, comparable to tesamorelin. CJC-1295 with DAC stands alone as the only GHRH analog in widespread research use with a multi-day half-life. That is its defining feature.
| Analog | Backbone | Half-Life | Activation Profile |
|---|---|---|---|
| Sermorelin | Unmodified GRF(1-29) | 10–20 min | Very sharp pulse |
| CJC-1295 No DAC | Modified GRF(1-29) | ~30 min | Sharp pulse |
| Tesamorelin | Modified GRF(1-44) | 25–40 min | Sharp pulse |
| CJC-1295 DAC | Modified GRF(1-29) + DAC linker | 5.8–8.1 days | Sustained tonic exposure |
The decision between CJC-1295 with DAC and without DAC depends entirely on what experimental question the protocol is designed to answer. There is no “better” form. there are two different tools for two different research questions.
Research protocols designed to study GH pulse architecture, pulse-dependent transcriptional patterns, or acute somatotroph responses generally select the no-DAC form. The short half-life allows multiple discrete pulses across an experimental day and preserves the natural pulse-trough cycle.
Protocols studying chronic GHRH-receptor occupancy, long-term IGF-1 elevation in research models, or pituitary somatotroph adaptation to continuous stimulation generally select the DAC form. The multi-day half-life allows a single administration to produce sustained receptor engagement.
For research models examining the synergy between GHRH and ghrelin pathways, the CJC-1295 + Ipamorelin blend Vitro supplies provides both compounds in a single lyophilized format with batch-specific identity and purity verification. See Vitro’s CJC-1295 + Ipamorelin mechanism guide for a fuller look at the combined pathway research.
Both CJC-1295 forms are supplied as lyophilized powders. The lyophilized state is the most stable storage format for compounds in this molecular weight range.
Compounds in solution are vulnerable to several degradation pathways: hydrolytic cleavage of the amino-acid backbone, oxidation of methionine and cysteine residues, deamidation of asparagine and glutamine, and aggregation. All of these reactions require water or are accelerated by it. Removing water through lyophilization slows them down dramatically.
The DAC version has one additional consideration: the maleimidopropionic acid linker must remain intact and reactive for the compound to bind albumin after reconstitution. Maleimide groups are reasonably stable in dry form but can hydrolyze in aqueous solution over time, particularly at higher pH. Lyophilized storage of CJC-1295 with DAC at appropriate temperatures preserves linker reactivity. Reconstituted material has more limited shelf-life.
Both forms can be characterized by reverse-phase HPLC and mass spectrometry. The DAC version shows a characteristic mass shift relative to the unmodified compound that corresponds to the linker addition. a useful identity check. Every batch of the CJC-1295 + Ipamorelin blend Vitro supplies ships with a batch-specific Certificate of Analysis from Freedom Diagnostics, an ISO-certified independent analytical laboratory.
In laboratory research workflows, lyophilized GHRH analogs are reconstituted with bacteriostatic water or sterile water for laboratory use, depending on the protocol. The reconstitution process for both CJC-1295 forms follows standard lyophilized compound handling procedures.
Once reconstituted, the no-DAC form is generally stored refrigerated and used within a defined laboratory-protocol window. The DAC form has additional considerations because of the linker chemistry. extended storage in solution can reduce linker reactivity and therefore reduce albumin-binding efficiency in downstream experiments.
Lyophilized compounds of this class are generally stored frozen for long-term inventory and refrigerated for working stocks. Repeated freeze-thaw cycles accelerate degradation, particularly for the DAC form where linker integrity matters. Aliquoting reconstituted material into single-use volumes before freezing is standard laboratory practice.
For a deeper look at diluent selection for compound reconstitution in research settings, see Vitro’s bacteriostatic water vs sterile water vs saline decision matrix and the bacteriostatic water reference guide.
CJC-1295 in either form is not approved for human consumption by the FDA. Both forms are supplied as analytical-grade biochemical reference standards for laboratory research use only. Research conducted with these compounds occurs in preclinical and in-vitro models, not in human clinical applications.
The FDA has flagged CJC-1295 alongside several other compounds in recent regulatory actions against compounding pharmacies that marketed it for non-research use. Vitro Labs is a chemical supplier, not a compounding pharmacy or 503A/503B outsourcing facility. Materials are supplied strictly for laboratory research, analytical method development, identity verification, and laboratory evaluation by qualified research customers.
For more on the broader regulatory framework, the Vitro editorial standards page documents the sourcing posture and citation policy that governs every article in the Research Library.
Research interest in CJC-1295. particularly the DAC form. has shifted in recent years toward understanding the long-term consequences of sustained GHRH-receptor activation. The original Teichman and Ionescu/Frohman work established the pharmacokinetic and acute pharmacodynamic profile. More recent preclinical work has examined downstream questions about pituitary somatotroph adaptation, IGF-1 axis regulation, and the differential transcriptional consequences of pulsatile versus tonic GH exposure that Sackmann-Sala first characterized in 2009.
The broader GH-secretagogue research field has also expanded to include comparison studies pairing CJC-1295 (typically the no-DAC form for cleaner pulse architecture) with selective ghrelin-pathway compounds like ipamorelin, which is one reason the combination format Vitro supplies maps onto how current research is most often designed.
CJC-1295 without DAC has a half-life of roughly 30 minutes in research models. CJC-1295 with DAC has a reported half-life of 5.8 to 8.1 days, as measured by Teichman and colleagues in a phase-1 study of healthy research subjects (PMID: 16940447). The difference comes from the DAC linker, which covalently bonds the compound to circulating serum albumin and prevents rapid enzymatic clearance and renal filtration.
DAC stands for Drug Affinity Complex. It is a small reactive linker. specifically maleimidopropionic acid. attached to the C-terminus of the CJC-1295 compound. The maleimide group reacts selectively with the free thiol on cysteine-34 of serum albumin, forming a stable covalent bond. Once bound, the compound circulates with albumin and inherits its multi-day half-life. Jetté and colleagues at ConjuChem described the chemistry in detail in 2005 (PMID: 16037509).
CJC-1295 and ipamorelin activate different receptors that converge on the same outcome. CJC-1295 binds the GHRH receptor on pituitary somatotrophs. Ipamorelin binds the growth hormone secretagogue receptor (GHS-R1a), which natively responds to ghrelin. When both pathways are activated simultaneously, the GH release response is greater than either alone. Ipamorelin’s exceptional selectivity. it does not release prolactin or ACTH at GH-releasing doses, as Raun et al. characterized in 1998 (PMID: 9849822). makes it a clean pairing partner for either form of CJC-1295.
CJC-1295 without DAC produces pulsatile GH release because its short half-life allows the GHRH receptor to be activated sharply and then return to baseline within hours. CJC-1295 with DAC produces sustained, low-level GHRH-receptor activation across multiple days, which elevates baseline GH and IGF-1 but blunts the natural pulse architecture, as Ionescu and Frohman documented in 2006 (PMID: 16868048). Research protocols designed to study pulse-dependent signaling generally use the no-DAC form.
All three are GHRH analogs built on the GRF(1-29) or GRF(1-44) backbone. Sermorelin is unmodified GRF(1-29) with the shortest half-life (10–20 minutes). CJC-1295 without DAC adds four amino acid substitutions that extend half-life to roughly 30 minutes. Tesamorelin uses a different modification (a trans-3-hexenoyl group on GRF(1-44)) and reaches a similar 25–40 minute half-life. CJC-1295 with DAC is the only GHRH analog in widespread research use with a multi-day half-life (5.8–8.1 days), achieved through albumin binding rather than through structural modification of the compound itself.
Both forms are supplied as lyophilized powders, which is the most stable storage format. Lyophilized material is generally stored frozen for long-term inventory and refrigerated for working stocks. Once reconstituted, the no-DAC form is stored refrigerated and used within a defined laboratory-protocol window. The DAC form has additional considerations because the maleimide linker can hydrolyze in aqueous solution over time, which would reduce albumin-binding efficiency in downstream experiments. Repeated freeze-thaw cycles should be avoided, particularly for the DAC form.
