CJC-1295 exists in two distinct chemical forms — with the drug-affinity complex (DAC) modification and without it. They share the same biological target but behave so differently in plasma that they are best thought of as separate research tools. This article walks through what DAC is, how it changes the pharmacokinetics, and where each form fits in published research designs.
Background: what CJC-1295 is
CJC-1295 is a synthetic 30-amino-acid analog of growth-hormone-releasing hormone (GHRH), the hypothalamic peptide that drives pulsatile GH release from the pituitary. The native human GHRH(1-29) sequence — known as sermorelin — is biologically active but has a plasma half-life measured in minutes due to rapid degradation by dipeptidyl peptidase IV (DPP-IV) and other proteases.
CJC-1295 modifies the GHRH(1-29) sequence at four positions (D-Ala²-Gln⁸-Ala¹⁵-Leu²⁷) to resist enzymatic degradation. These four substitutions alone, without any further modification, define what is commonly sold as CJC-1295 without DAC — and is also known in the literature as modified GRF(1-29) or tetrasubstituted GRF.
What "DAC" adds
The drug-affinity complex (DAC) modification — developed by ConjuChem — is a maleimidopropionic acid linker attached to a lysine added at the C-terminal end of the modified GHRH(1-29) sequence. Once injected, the maleimide group reacts covalently with the free cysteine residue on circulating serum albumin, tethering the peptide to a large, slow-clearing carrier protein.
This single modification dramatically changes the pharmacokinetic profile. The peptide is no longer cleared on a peptide-typical timescale; it is cleared on an albumin-typical timescale.
Half-life: the core difference
| Form | Plasma half-life | Typical research dosing cadence in literature |
|---|---|---|
| CJC-1295 without DAC (mod GRF 1-29) | ~30 minutes | Multiple short-window administrations, often paired with a secretagogue like ipamorelin to mimic a pulsatile profile. |
| CJC-1295 with DAC | ~6–8 days | Long-interval administration. Plasma GHRH activity is essentially continuous between doses. |
The 6–8 day half-life of CJC-1295 with DAC comes directly from the original ConjuChem phase I human pharmacokinetic study (Teichman et al., 2006), which established that albumin-conjugated GHRH analog plasma concentrations remain elevated for 7+ days after a single administration. The without-DAC form has been characterized in numerous shorter studies; ~30 minutes is the consensus value.
Pulsatility: why this matters for experimental design
Endogenous GH release is pulsatile. The pituitary responds to GHRH that arrives in transient bursts; continuous GHRH exposure causes receptor desensitization and downregulation of GH responses over time. This is a well-characterized finding in the GHRH-physiology literature.
- Without DAC reproduces something closer to a natural pulse: a sharp rise, a peak, and a fall over roughly an hour. Repeat administrations can model multiple pulses through the day.
- With DAC produces a tonic, non-pulsatile signal. This is a different physiological scenario and is the appropriate research tool when continuous GHRH exposure is the experimental variable being studied — not when modeling normal pulsatile signaling.
Stacking with secretagogues
The without-DAC form is commonly paired with a growth-hormone secretagogue receptor (GHSR / ghrelin receptor) agonist — most often ipamorelin — in published research designs. The mechanistic rationale is that GHRH and ghrelin act on independent pituitary pathways that synergize when co-stimulated, producing a larger GH response than either alone.
HelixCore offers ipamorelin pre-combined with the without-DAC base in our CJC + Ipamorelin blend for researchers using this combined-stimulation paradigm. The two compounds are also available separately for groups that prefer to control the ratio explicitly.
With-DAC CJC-1295 is generally not co-administered with a short-acting secretagogue in the same dose — the timescales do not match, and the chronic albumin-tethered GHRH signal is the experimental variable being isolated.
Stability and handling differences
Both forms ship as lyophilized powders and are reconstituted with bacteriostatic water following the standard protocol described in our reconstitution guide. Storage and handling are functionally identical between the two — 2–8°C after reconstitution, −20°C for long-term lyophilized stocks.
One operational note specific to the with-DAC form: the maleimide group is hydrolytically labile at high pH. Researchers performing custom buffer work with this compound should hold solutions near neutral pH and minimize time in solution before use. For ordinary BAC-water reconstitution, this is not an issue.
Summary
- The two forms differ by one modification (DAC linker / lysine) at the C-terminus.
- That modification covalently tethers the peptide to albumin in vivo.
- Result: plasma half-life jumps from ~30 minutes to ~6–8 days.
- Without-DAC = pulsatile-research tool, often paired with ipamorelin.
- With-DAC = continuous-GHRH-signal research tool, used alone.
- The two are not dose-equivalent and cannot be substituted for each other without reconsidering experimental design.
