CJC-1295 With DAC vs Without DAC: The Real Difference Explained

Two vials can carry the same name, CJC-1295, and contain molecules that behave as differently as a camera flash and a floodlight. One version fires a short burst of growth hormone signalling and is gone within hours. The other hooks itself onto the most common protein in your blood and keeps signalling for about a week. The only thing separating them is a small chemical attachment called DAC.

That makes “with DAC or without DAC?” one of the most important questions anyone researching this peptide can ask, and one of the most confused online. This guide explains what DAC actually is, how the attachment was invented, what the published studies measured for each form, why the difference in timing changes everything about how the compounds are used, and how to choose between them. Both forms are supplied by Crown Peptides for laboratory research use only.

First, What Is CJC-1295 at All?

CJC-1295 is a synthetic analogue of growth hormone releasing hormone, or GHRH, the signal the brain uses to tell the pituitary gland to release growth hormone. Natural GHRH is 44 amino acids long, but researchers discovered in the 1980s that its first 29 amino acids carry essentially all of its activity. That shorter fragment, called GRF(1-29), is the starting point for CJC-1295.

There is a problem with the natural fragment, though. It is destroyed in the bloodstream within minutes. An enzyme called dipeptidyl peptidase-4, or DPP-4, snips off its first two amino acids, inactivating it, and other enzymes attack elsewhere along the chain. Whatever GRF(1-29) is going to do, it has to do quickly.

Four changes to make it tougher

CJC-1295’s designers began by making four precise substitutions to the 29-amino-acid chain: a D-alanine at position 2, glutamine at position 8, alanine at position 15 and leucine at position 27. Each targets a known weak point. The D-alanine, a mirror-image form of the natural amino acid, blocks DPP-4 from recognising its cutting site. The others improve resistance to other enzymes and to chemical degradation such as oxidation.

That tougher, four-times-modified 29-amino-acid peptide is what is known as CJC-1295 without DAC. You will also see it called modified GRF(1-29), Mod GRF 1-29 or tetrasubstituted GRF(1-29). All of these names describe the same molecule.

And then the attachment

CJC-1295 with DAC takes that same modified peptide and adds one more thing: an extra lysine at the end of the chain carrying a small reactive chemical group. That group is the Drug Affinity Complex, or DAC, and it is what turns a short-lived peptide into a long-lived one.

So the relationship is simple. CJC-1295 without DAC is the modified peptide. CJC-1295 with DAC is the modified peptide plus a lysine and a chemical hook.

The Montreal Idea: Borrowing the Lifespan of Albumin

DAC was the signature technology of ConjuChem, a biotechnology company based in Montreal. Its idea was elegant: rather than redesigning each drug to survive longer on its own, why not attach it to something that already lasts a long time in the blood?

Why albumin is the perfect carrier

Albumin is the most abundant protein in blood plasma, making up more than half of all plasma protein. It carries hormones, fatty acids and many drugs around the body, and it lasts a remarkably long time, with a half-life of around three weeks in humans. Crucially, it is too large to be filtered out by the kidneys, which is one of the main ways small peptides are cleared.

A single sticky spot

Albumin has a useful chemical feature: a single free thiol group, a reactive sulphur, on the cysteine at position 34 of its chain. ConjuChem’s chemists designed DAC to react with exactly that spot. The DAC group on CJC-1295 is a maleimide, a chemical that forms a stable, permanent bond with thiols. Once CJC-1295 with DAC enters circulation, it finds albumin’s cysteine 34 and locks on.

The study that picked CJC-1295

ConjuChem’s scientists published the work that identified CJC-1295 in Endocrinology in 2005 (PMID: 15817669). Jetté and colleagues made three versions of GRF(1-29) with maleimide groups attached at different points and tested them. All three, once bound to human serum albumin, were more resistant to DPP-4 and still stimulated growth hormone secretion from rat pituitary cells in the laboratory.

When injected into rats, the best of the three, CJC-1295, produced a four-fold increase in growth hormone release over two hours compared with GRF(1-29) alone. It was still present in the blood beyond 72 hours. Analysis of rat blood showed CJC-1295 appearing on the albumin band within 15 minutes of injection and remaining in circulation beyond 24 hours. That confirmed the DAC strategy worked exactly as designed: the peptide found albumin quickly and stayed attached.

What Happens When CJC-1295 With DAC Reaches People

CJC-1295 with DAC was then tested in two published clinical studies in healthy adults, both appearing in the Journal of Clinical Endocrinology and Metabolism in 2006.

A week-long effect from one injection

In the first, Teichman, Frohman and colleagues ran two randomised, placebo-controlled, double-blind trials in healthy volunteers aged 21 to 61 (PMID: 16352683). After a single injection, mean growth hormone concentrations rose two- to ten-fold and stayed elevated for six days or more. IGF-1, the downstream hormone that growth hormone drives, rose 1.5- to three-fold and stayed elevated for 9 to 11 days. The estimated half-life of CJC-1295 was 5.8 to 8.1 days. With repeated doses, IGF-1 stayed above baseline for up to 28 days, with evidence of a cumulative effect. No serious adverse reactions were reported.

To put that half-life in context: natural GHRH lasts minutes. CJC-1295 with DAC lasts roughly a week. The albumin hook extended the peptide’s life by a factor of more than a thousand.

The pulses survive

That raised an important question. Growth hormone is naturally released in pulses, and many of its effects are thought to depend on that pulsing pattern. Would a week of continuous GHRH signalling flatten it?

Ionescu and Frohman answered that in a second study, sampling blood every 20 minutes through the night in healthy young men before and a week after a single injection (PMID: 17018654). The pulses were preserved: their frequency and size did not change. What rose dramatically was the floor between them. Trough growth hormone levels increased 7.5-fold, mean growth hormone rose by 46% and IGF-1 by 45%. The authors concluded that CJC-1295 increased growth hormone and IGF-1 while preserving the natural pulsatile pattern, and highlighted the raised trough as a key driver of the IGF-1 increase.

Restoring growth in mice lacking GHRH

A third study tested CJC-1295 with DAC in a demanding animal model, and it is especially useful because it shows what happens when the peptide has to do all the work itself, with no natural GHRH signal to amplify. In 2006, a team at Johns Hopkins led by Roberto Salvatori published work in the American Journal of Physiology on mice genetically engineered to lack GHRH entirely (PMID: 16822960). These mice grow poorly, and the same group had previously found that even twice-daily injections of a conventional GHRH analogue could not normalise their growth.

With CJC-1295, the picture changed. Mice treated daily for five weeks reached normal body weight and length, with normal bone length and normal body composition. Treatment every 48 or 72 hours improved growth compared with placebo but did not fully normalise it. CJC-1295 also increased pituitary growth hormone messenger RNA and caused the growth hormone-producing cells to multiply, showing that sustained GHRH signalling supports the pituitary itself as well as its output. The difference between daily and less frequent treatment is also telling: in mice, which clear drugs far faster than people do, the signal worked best when it was renewed every day.

And CJC-1295 Without DAC?

Here is where many online comparisons go wrong. Most of the published pharmacology described above was carried out on the DAC version. CJC-1295 without DAC, the modified GRF(1-29), has a much smaller dedicated literature.

What is well established is its design logic. The four substitutions protect it against DPP-4 and other enzymes, so it lasts considerably longer than natural GRF(1-29) or Sermorelin, which is the unmodified fragment. But without the albumin hook, it is still cleared relatively quickly, over a period usually described as around half an hour rather than days. It therefore produces a short, sharp GHRH signal, much closer to a natural pulse than the continuous signal of the DAC version.

That short, pulse-like action is exactly why the non-DAC form has become the preferred partner for ghrelin receptor agonists such as Ipamorelin, which also act over a short window. The pairing aims to reproduce the body’s own coordinated burst of growth hormone release.

Why the Shape of the Signal Matters So Much

It would be easy to assume that more growth hormone signalling is simply more growth hormone signalling, whatever its timing. Biology does not work that way, and the difference between the two forms of CJC-1295 only makes sense once you see why.

The body reads rhythm, not just quantity

Growth hormone is released in pulses: a few large bursts through the day and night, with the biggest usually arriving shortly after the onset of deep sleep. Between bursts, levels fall very low. Tissues respond not only to how much growth hormone they see on average but to the pattern in which it arrives.

The liver’s striking example

The clearest demonstration comes from rodents. Male rats and mice release growth hormone in tall, widely spaced pulses with near-zero troughs between them, while females have a more continuous pattern. That difference alone is enough to switch on different sets of genes in the liver, including enzymes that process drugs and hormones, so that male and female livers behave measurably differently. A 2006 review in Molecular Endocrinology by David Waxman and colleagues described how growth hormone’s secretion pattern regulates this sex-dependent liver gene expression (PMID: 16543404). Same hormone, different rhythm, different biology.

What that means for CJC-1295

This is why the DAC question is not just about convenience or potency. CJC-1295 with DAC keeps pulses intact but raises the trough between them, shifting the overall pattern towards a more continuous profile. CJC-1295 without DAC produces a brief burst that leaves the troughs largely alone. Researchers choosing between them are, in effect, choosing which growth hormone rhythm to create, and the rhythm itself can shape the outcome.

With DAC vs Without DAC: Side by Side

With the research laid out, the differences are easy to summarise.

Structure

Without DAC: 29 amino acids with four substitutions. With DAC: the same 29 amino acids and substitutions, plus a lysine carrying a maleimide group, 30 residues in all.

How long it lasts

Without DAC: a short window, measured in minutes to around half an hour. With DAC: a half-life of roughly six to eight days in human studies, because it binds albumin.

Signal pattern

Without DAC: a short pulse of GHRH receptor activation, similar to a natural burst. With DAC: sustained receptor activation over days, which raises baseline growth hormone between natural pulses while leaving the pulses themselves intact.

Published human data

Without DAC: little dedicated clinical research. With DAC: two published clinical studies in healthy adults with detailed pharmacokinetic and pulsatility data, plus animal work including the GHRH-knockout mouse study.

Typical research pairing

Without DAC: frequently paired with Ipamorelin or other ghrelin receptor agonists. With DAC: usually studied on its own, as a tool for sustained GHRH signalling.

Which One Fits the Research Question?

Autocomplete data shows people asking “which is better, DAC or no DAC?” In research terms, it depends entirely on the pattern of signal you want to study.

Choose CJC-1295 with DAC for sustained signalling

The DAC version is the right tool for questions about continuous GHRH receptor activation: how raised baseline growth hormone affects IGF-1 over days and weeks, how the pituitary adapts to sustained stimulation, and how long-acting peptide design behaves in living systems. Its detailed human pharmacokinetic data make it a strong reference compound for albumin-binding technology generally.

Choose CJC-1295 without DAC for pulse-style signalling

The non-DAC version is the right tool when you want to mimic a natural GHRH pulse with a more durable molecule than Sermorelin, and especially when you want to combine it with a ghrelin receptor agonist to recreate a coordinated growth hormone burst. That is the logic behind the CJC-1295 (No DAC) + Ipamorelin (Blend).

Or compare them directly

Because the two forms share the same modified peptide, comparing them in the same model isolates a single variable: timing. Any difference in outcome can be attributed to sustained versus pulsed GHRH receptor activation, which is one of the central questions in growth hormone research.

The Technical Breakdown: Chemistry of the Hook

This section is for readers who want the chemistry in detail.

The maleimide-thiol reaction

A maleimide is a five-membered ring containing a carbon-carbon double bond flanked by two carbonyl groups. That double bond is highly reactive towards thiols. When a thiol meets a maleimide, it adds across the double bond in a reaction known as a Michael addition, forming a stable thioether bond. The reaction is fast and highly selective for thiols at physiological pH, which is why maleimides are widely used in bioconjugation chemistry, including in several antibody-drug conjugates.

Why cysteine 34 in particular

Most cysteines in proteins are paired up in disulfide bonds, leaving no free thiol to react. Albumin has 35 cysteines, and 34 of them are paired. The one exception, cysteine 34, carries the protein’s only free thiol, making it a single, predictable attachment point. Because albumin is so abundant, there is always plenty available for CJC-1295 to find.

The linker

In CJC-1295, the maleimide is attached to the side chain of the added C-terminal lysine through a short propionamide linker, described in the 2005 paper as an N-epsilon-3-maleimidopropionamide derivative of lysine. Placing the hook at the end of the peptide, away from the region that binds the GHRH receptor, allows the peptide to remain active even while attached to albumin.

Why the substitutions still matter with DAC

It might seem that albumin binding alone would protect the peptide. But the Jetté study showed that the albumin conjugates were more resistant to DPP-4, not immune to it, and the free peptide exists briefly before it binds. The four substitutions provide a second layer of protection, which is why CJC-1295 with DAC carries both.

A strategy that spread

Albumin binding has since become one of the most successful strategies for extending the life of peptide drugs, though often through a different mechanism. The GLP-1 medicines liraglutide and semaglutide, for example, carry fatty acid chains that bind albumin non-covalently, reversibly rather than permanently, extending their half-lives to roughly half a day and roughly a week respectively. CJC-1295’s permanent covalent approach is a distinct and elegant variation on the same theme.

The bigger picture of half-life extension

Making peptides last longer is one of the central challenges of modern drug design. Most natural peptides and proteins survive only minutes to hours in the body, cleared by enzymes and filtered out by the kidneys. A 2018 review in Current Pharmaceutical Design by Tan and colleagues surveyed the main strategies, noting that the two most common approaches are reducing the rate at which the kidneys clear a molecule and exploiting the body’s natural recycling system for albumin and antibodies, which protects both from breakdown and keeps them circulating for weeks (PMID: 30727869). Other approaches include attaching polyethylene glycol chains, a technique called PEGylation, and fusing a peptide to part of an antibody. CJC-1295 with DAC belongs to the albumin family of strategies, and its covalent, one-step design made it one of the earliest and most direct demonstrations of the idea for a hormone-releasing peptide.

Why Identity Testing Matters More Than Usual Here

Two products with almost the same name and very different behaviour are a recipe for confusion, and that makes analytical verification essential.

The first question is simply which form is in the vial. CJC-1295 with DAC is heavier than the non-DAC form because of the extra lysine and the maleimidopropionamide group, so mass spectrometry distinguishes them immediately. A vial labelled as one but containing the other would produce a completely different experiment.

The second is whether the substitutions are correct. A version with ordinary L-alanine at position 2 instead of D-alanine would have exactly the same mass but lose its DPP-4 resistance, so a clean HPLC profile from a well-controlled synthesis matters too. The third, for the DAC form, is whether the maleimide group is intact: maleimides can react with other thiols or open up in water over time, which would stop the peptide binding albumin.

The Crown Peptides standard

Every batch of CJC-1295 with DAC and the CJC-1295 (No DAC) + Ipamorelin (Blend) supplied by Crown Peptides comes with a batch-specific certificate of analysis showing HPLC purity and mass spectrometry identity, with lot numbers matching those on vial labels. Published certificates are on our Lab Reports page, and our guides to peptide testing and reading a certificate of analysis explain the methods.

Handling

Both are supplied as lyophilised powders and should be stored cold, dry and away from light. Because the DAC form carries a reactive maleimide, it is particularly important to keep it dry until use and to handle reconstituted solutions carefully. Our guides to peptide reconstitution, peptide half-life and the peptide calculator cover the practical side, and Bacteriostatic Water is available alongside.

Related Compounds in the Growth Hormone Axis

CJC-1295 sits in a family of compounds acting at different points in the growth hormone system.

The other GHRH analogues

Sermorelin is the unmodified GRF(1-29), once an FDA-approved paediatric medicine, and Tesamorelin keeps all 44 amino acids of GHRH with a protective group on its front end. Compare them in CJC-1295 vs Sermorelin and Sermorelin vs Tesamorelin.

The ghrelin receptor agonists

Ipamorelin, GHRP-2 and GHRP-6 act on the other main growth hormone receptor. Our article CJC-1295 No DAC and Ipamorelin: the two-pathway approach explains why pairing the two receptor systems is so common.

Downstream

IGF-1 LR3 is a long-acting analogue of the downstream hormone IGF-1. Our CJC-1295 with DAC guide covers the DAC form on its own in more depth, and the full group is in our endocrine and hormonal research peptides category.

DAC Questions, Answered

What does DAC stand for?

Drug Affinity Complex. It is a reactive maleimide group, attached through an added lysine, that binds permanently to the free thiol on albumin in the blood.

Is Mod GRF 1-29 the same as CJC-1295 without DAC?

Yes. Modified GRF(1-29), Mod GRF 1-29 and tetrasubstituted GRF(1-29) all describe CJC-1295 without DAC.

How long does CJC-1295 with DAC last?

In human studies, its estimated half-life was 5.8 to 8.1 days, with growth hormone elevated for six days or more and IGF-1 for 9 to 11 days after a single injection.

Does CJC-1295 with DAC stop natural growth hormone pulses?

No. A 2006 study found the frequency and size of natural pulses were unchanged, while the baseline between them rose substantially.

Is CJC-1295 with DAC stronger than without DAC?

Not stronger in the sense of a bigger single burst. It is longer-acting. The DAC version produces a sustained signal over days, while the non-DAC version produces a short pulse. Which is more useful depends on the pattern of signalling the research requires.

Can the DAC version be switched off once it has bound albumin?

No. The bond between the maleimide and albumin’s cysteine is designed to be stable, so once the peptide has attached there is no way to release it on demand. It stays in circulation for days, with a measured half-life of roughly six to eight days in people, gradually declining as the peptide and its carrier are cleared. That long, fixed duration is a key reason researchers treat the two forms as completely different tools, and why the DAC form is chosen deliberately for studies where sustained signalling is the aim rather than a side effect.

Why is the no-DAC version paired with Ipamorelin?

Because both act over a short window, together producing a coordinated burst of growth hormone release through two complementary receptors, closer to the body’s own pattern.

One Small Hook, Two Different Tools

The difference between these two peptides comes down to a few atoms: a lysine and a maleimide ring. Yet those atoms let one molecule borrow the three-week lifespan of the most common protein in the blood, turning a signal that lasts minutes into one that lasts a week, without silencing the body’s natural rhythm. The other molecule keeps the tougher backbone but stays brief, pulse-like and ideal for partnership.

Knowing which one you are working with, and why, is the foundation of any good experiment on the growth hormone axis. Explore CJC-1295 with DAC and the CJC-1295 (No DAC) + Ipamorelin (Blend) from Crown Peptides, every batch HPLC and mass spectrometry verified and dispatched from the UK.