CJC-1295 With DAC vs Without DAC: Research Comparison
By UK Peptide Lab Research Team•22 May 2026•8 min read
Overview
CJC-1295 exists in two distinct research forms with very different pharmacokinetic profiles. The 'without DAC' variant is a modified GHRH(1-29) analogue with a circulating half-life measured in tens of minutes, producing a pulsatile growth hormone research model. The 'with DAC' variant adds a Drug Affinity Complex moiety that binds covalently to circulating albumin, extending half-life to multiple days and producing a continuous GH elevation model. Both compounds share the same core GHRH receptor agonism, but the pharmacokinetic divergence has substantial experimental consequences.
UK Peptide Lab supplies both CJC-1295 with DAC and CJC-1295 without DAC as research-grade lyophilised powder.
CJC-1295 Without DAC: Modified GHRH(1-29)
The 'no DAC' variant of CJC-1295 is a modified GHRH(1-29) sequence with four amino acid substitutions designed to resist enzymatic degradation by dipeptidyl peptidase IV (DPP-IV) and other serum proteases. The substitutions are typically described as D-Ala at position 2, Gln at position 8, Ala at position 15, and Leu at position 27. These changes extend the serum half-life of the peptide from the minutes-range characteristic of native GHRH to a half-life on the order of 30 minutes in research models, still short enough to preserve a pulsatile signalling pattern at the GHRH receptor when administered intermittently.
CJC-1295 With DAC: The Drug Affinity Complex
The 'with DAC' variant adds a maleimidopropionic acid lysine moiety at the C-terminus of the modified GHRH(1-29) sequence. The maleimide group is reactive toward free cysteine thiols, and on injection it forms a covalent thioether bond with the free cysteine-34 residue of circulating serum albumin. The resulting albumin conjugate is too large for renal filtration and is protected from the proteolytic clearance that would otherwise rapidly remove the peptide. This albumin-tethering mechanism is the entire pharmacokinetic difference between the two forms.
Teichman and colleagues published the first human pharmacokinetic data on CJC-1295 with DAC in the Journal of Clinical Endocrinology and Metabolism in 2005, reporting an estimated half-life of 5.8 to 8.1 days after subcutaneous administration in healthy adults, with sustained GH and IGF-1 elevation for up to 28 days after multiple doses. This represents an approximately 200-fold extension of half-life relative to the no-DAC variant.
Receptor Mechanism: Identical
Both variants bind the GHRH receptor on pituitary somatotrophs and stimulate growth hormone synthesis and release through the same cAMP-mediated signalling cascade. The receptor pharmacology is not the differentiator between the two forms. The differentiator is exclusively the duration of receptor engagement: short pulses with the no-DAC variant, continuous bathing of the receptor with the DAC variant.
Continuous vs Pulsatile GH Research Models
The pharmacokinetic divergence produces fundamentally different research models. CJC-1295 without DAC, when administered in a typical research protocol, produces discrete GH pulses with restoration of baseline between doses. This mimics the body's natural pulsatile GH secretion pattern and is suitable for research questions where the pulsatile architecture of GH signalling is important.
CJC-1295 with DAC, by contrast, produces continuous elevation of trough GH levels alongside preserved pulsatile peaks. Ionescu and Frohman reported in the Journal of Clinical Endocrinology and Metabolism in 2006 that pulsatile GH secretion was preserved after CJC-1295 with DAC administration, with the principal effect being a 7.5-fold increase in trough (basal) GH levels rather than disruption of pulse architecture. This is mechanistically important: chronic GH elevation studies often assume that pulsatility is lost, but the published data suggest both basal and pulsatile contributions can be examined simultaneously.
Research Applications
The no-DAC variant is selected when the research question requires preserved physiological pulsatility, controlled timing of GH exposure, or modelling of natural GHRH dynamics. The DAC variant is selected for chronic exposure studies, less-frequent dosing protocols, and research where sustained elevation of IGF-1 is the desired output. Both are commonly studied in combination with ghrelin receptor agonists such as Ipamorelin, where dual-pathway activation produces additive GH release. See the CJC-1295 vs Ipamorelin comparison for detail on the combined-pathway research model, and the Tesamorelin vs CJC-1295 GH secretagogue comparison for further context on alternative GH-releasing peptide tools.
Laboratory Handling
Both variants are supplied as lyophilised powder. Store at -20°C prior to reconstitution. Reconstitute with bacteriostatic water by slowly injecting the diluent down the inner wall of the vial and swirling gently. Never shake. Store the reconstituted solution at 2-8°C and use within 4 weeks. The two forms should not be combined in the same vial unless the research protocol specifically requires it, as the very different pharmacokinetics complicate dose-response interpretation.
Sourcing in the UK
UK Peptide Lab supplies research-grade CJC-1295 with DAC and CJC-1295 without DAC as lyophilised powder with full third-party HPLC documentation published on the product page. Same-day UK dispatch on orders placed before 2pm GMT, free Royal Mail Tracked shipping over £45. For in-vitro laboratory research use only, not for human consumption.
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Disclaimer: This article is for research and educational purposes only. All information provided is not intended as medical advice. UK Peptide Lab products are not for human consumption and are sold strictly for laboratory research use only.