CJC-1295 with DAC vs without DAC: the difference explained

Research context (RUO): CJC-1295 with DAC and CJC-1295 without DAC (mod GRF 1-29) are synthetic analogues of growth hormone-releasing hormone (GHRH). At Peplife both peptides are supplied exclusively for in-vitro laboratory research (Research Use Only) and are not intended for human or animal use.

CJC-1295 with DAC vs without DAC: the difference explained

The comparison CJC-1295 with DAC vs without DAC is one of the most frequently asked questions in GHRH research. Chemically, both variants share the same core: a modified fragment of the first 29 amino acids of human growth hormone-releasing hormone. The difference lies in a single addition at the C-terminus, the drug affinity complex, and that addition extends the half-life from roughly half an hour to several days. This changes not only the pharmacokinetics but also the type of research model in which the compound is genuinely useful. This pillar article sets both variants side by side, purely from a research perspective.

The core: one shared peptide backbone, two half-lives

Native GHRH(1-29) is broken down in plasma within minutes by dipeptidyl peptidase-4, which cleaves the peptide at the N-terminus. In both CJC variants that cleavage site is protected by four amino acid substitutions: D-alanine at position 2, glutamine at position 8, alanine at position 15 and leucine at position 27. This modified backbone is known in the literature as mod GRF (1-29) and is sold commercially as CJC-1295 without DAC. The half-life thereby rises from a few minutes to about thirty minutes: long enough for a measurable, sharply defined GH peak, too short to raise plasma levels for any length of time.

What the drug affinity complex actually does

CJC-1295 with DAC carries a maleimidopropionyl group at the C-terminus. After administration this group forms a covalent bond with cysteine-34 of albumin, the most abundant protein in blood plasma. The peptide then travels along with its carrier and so escapes both renal filtration and enzymatic breakdown. In the 2006 study by Teichman and colleagues, a half-life of 5.8 to 8.1 days was measured in healthy adults after a single dose. Growth hormone levels remained elevated for about six days and IGF-1 levels for nine to eleven days. Without DAC that effect has faded completely within a few hours.

Pulsatile versus continuous: why the research model differs

Growth hormone is physiologically released in pulses, with the largest peak during deep sleep. A short-acting GHRH analogue mimics that pattern: every administration produces a defined pulse, after which levels fall back to baseline. That makes mod GRF (1-29) suitable for models measuring the amplitude and recovery of a single pulse. CJC-1295 with DAC, by contrast, raises the baseline for days on end. Interestingly, Ionescu and Frohman showed in 2006 that pulsatility does not disappear in the process: under continuous GHRH stimulation the pulses persisted, but on top of an elevated baseline. For research into chronic exposure that is a fundamentally different starting point from a series of separate peaks.

The two variants side by side

Dosing frequency in published research

The difference in frequency follows directly from the pharmacokinetics. Studies using the DAC variant work with one administration per week or per two weeks, because the compound itself extends exposure. Research with mod GRF (1-29) instead uses several administrations per day, often around natural pulse moments, in order to follow the endogenous rhythm rather than override it. Anyone comparing both variants within the same protocol should therefore not match the dose per administration, but the total exposure over time.

Combining with a GH secretagogue in research models

GHRH analogues and ghrelin mimetics such as ipamorelin act on different receptors and are therefore studied together in many models. Because mod GRF (1-29) and ipamorelin have a comparably short time window, their peaks coincide when they are given at the same time. With the DAC variant things work out differently: the GHRH component remains present for days, while the secretagogue is short-acting. Which of the two combinations fits depends entirely on the research question. In the comparison Ipamorelin vs CJC-1295 vs sermorelin these routes are set out side by side in more detail.

Which variant suits which research objective

For short-running in-vitro experiments centred on the direct response of the pituitary to a GHRH signal, an albumin binder adds nothing: the longer half-life is then merely a confounding variable. Conversely, a short-acting analogue is impractical in models spanning weeks, because exposure is then impossible to keep stable. That is also why tesamorelin and sermorelin, with their own half-lives, appear in yet other research designs.

CJC-1295 in laboratory research: handling and reconstitution

Both variants are supplied as a freeze-dried powder and are stable in that form for long periods at minus twenty degrees Celsius. After reconstitution with bacteriostatic water the solution should be kept refrigerated and in the dark. Because the DAC variant owes its action to a reactive maleimide group, repeated warming and cooling is particularly undesirable there. The reconstitution guide sets out the calculation steps and the practicalities of preparation and storage.

Quality & purity

Precisely with two peptides that look almost identical on the certificate of analysis, identity testing is essential: the difference between the variants is a single modification at the end of the chain. Every relevant batch is independently HPLC-tested by an external laboratory and the certificate of analysis is publicly verifiable per batch, so the research material demonstrably matches the specified peptide. In the pillar article why we rejected a batch you can read how that process works in practice.

Frequently asked questions about CJC-1295 with and without DAC

What does DAC mean in CJC-1295?
DAC stands for drug affinity complex: a maleimidopropionyl group that binds covalently to albumin after administration and thereby keeps the peptide in circulation for days.

Is CJC-1295 without DAC the same as mod GRF 1-29?
Yes. Both names refer to the same quadruply substituted GHRH(1-29) fragment; mod GRF (1-29) is the usual term in the scientific literature.

Why does the dosing frequency differ so much?
Because the half-life differs by a factor of roughly three hundred. The DAC variant sustains exposure for days, the variant without DAC for only half an hour.

Does natural GH pulsatility disappear under the DAC variant?
In the research by Ionescu and Frohman, pulsatile secretion persisted under continuous GHRH stimulation, on top of an elevated baseline.

Are both variants approved as a medicine anywhere?
No. Neither variant is approved by the EMA, NVWA or FDA; they are supplied exclusively for laboratory research.

Read more & research at Peplife

• Research CJC-1295 with DAC at Peplife
• Research CJC-1295 without DAC at Peplife
• CJC-1295 and ipamorelin blend
• View all GH axis peptides
• CJC-1295: research on the GHRH analogue
• Ipamorelin vs CJC-1295 vs sermorelin
• Sermorelin: research on the short GHRH fragment
• Tesamorelin: research on the stabilised analogue

Sources: Teichman et al. 2006, J Clin Endocrinol Metab · Ionescu & Frohman 2006, pulsatile GH secretion · PubChem: CJC-1295 (CID 91971820) · PubChem: CJC-1295 without DAC (CID 91976842)

Research Use Only. All products are supplied exclusively for in vitro laboratory research. Not intended for diagnostic or therapeutic use in humans or animals, and not approved by the EMA or FDA.