The Structural Distinction: What DAC Actually Does
Both forms of CJC-1295 are based on Modified GRF (1-29) -- a 29-amino acid analogue of GHRH(1-29) with four amino acid substitutions that confer DPP-4 resistance and improved receptor binding: Tyr1 to His1, Ala2 to Aib2 (alpha-aminoisobutyric acid), Gln8 to Ala8, and Ala15 to Gln15. These substitutions alone produce the "without DAC" form, also called Mod GRF 1-29, with a half-life of approximately 30 minutes -- substantially longer than native GHRH (1-2 minutes) due to DPP-4 resistance, but still relatively short-acting.
The DAC (Drug Affinity Complex) modification adds a maleimidopropionic acid (MPA) group to the epsilon-amino group of lysine at position 40 of the extended sequence. In vivo, this MPA group reacts with cysteine-34 on circulating serum albumin through a Michael addition reaction, forming a covalent bond. Since albumin has a half-life of approximately 21 days, the albumin-conjugated peptide is substantially protected from renal clearance, extending the effective half-life to 7-10 days. This same albumin-binding strategy is used by semaglutide and other long-acting peptide drugs.
| Parameter | CJC-1295 Without DAC (Mod GRF 1-29) | CJC-1295 With DAC |
|---|---|---|
| Also called | Mod GRF 1-29, Modified GRF(1-29) | CJC-1295 DAC, DAC:GRF |
| Amino acids | 29 residues | 30 residues + DAC modification |
| Half-life | ~30 minutes | ~7-10 days |
| Albumin binding | No | Yes (covalent via MPA-Cys34) |
| GH release pattern | Pulsatile (physiological) | Sustained (non-pulsatile) |
| Research application | Pulsatile GH dynamics, GHRH receptor studies | Sustained GH elevation, long-exposure studies |
Why GH Release Pattern Matters for Research
Growth hormone is not secreted continuously -- it is secreted in pulses, with the majority of daily GH output occurring during slow-wave sleep. This pulsatile pattern is physiologically important: the oscillating on-off GH signal drives different downstream responses than continuous GH exposure. Sustained GH elevation leads to GH receptor downregulation and altered IGF-1 dynamics compared to pulsatile secretion.
CJC-1295 without DAC (Mod GRF 1-29) mimics the physiological pulsatile pattern. Its 30-minute half-life means each administration produces a defined GH pulse followed by return to baseline -- a pattern closely resembling endogenous GHRH-driven GH secretion. Research protocols examining GH pulse dynamics, somatotroph responsiveness, or IGF-1 response to pulsatile GH stimulation benefit from the without-DAC form.
CJC-1295 with DAC produces sustained GHRH receptor activation and correspondingly sustained GH elevation. This profile is appropriate when the research question requires prolonged GH exposure -- studies of long-term GH-dependent effects on IGF-1, body composition endpoints in animal models, or pharmacokinetic modeling of long-acting GHRH analogues. The trade-off is loss of physiological pulsatility, which may confound interpretation in research contexts where GH pulse dynamics are mechanistically relevant.
Ipamorelin Combination Research
Both forms of CJC-1295 are frequently studied in combination with Ipamorelin, a selective GHSR (ghrelin receptor) agonist. The combination addresses both major GH secretagogue pathways: GHRH receptor (CJC-1295) and ghrelin receptor (Ipamorelin). These pathways converge on somatotroph cells through different second messenger systems -- GHRH-R through cAMP, GHSR through PLC/IP3/PKC -- producing a synergistic GH release that exceeds either compound alone.
The synergy has a physiological basis: endogenous GH pulses are triggered by the simultaneous arrival of GHRH and ghrelin signals at the somatotroph. CJC-1295 plus Ipamorelin recapitulates this dual-signal pattern in research models. The pre-formulated CJC-1295/Ipamorelin combination from LSPC provides both compounds in a single vial, simplifying research protocols that require both signals.
Selecting the Right Form for Your Protocol
Use CJC-1295 without DAC (Mod GRF 1-29) when your research requires physiologically accurate GH pulsatility, short-term mechanistic studies of GHRH receptor signaling, or comparison to endogenous GHRH. The short half-life gives you temporal control over GH exposure -- you can define exactly when the GH pulse occurs and how long it lasts in your experimental system.
Use CJC-1295 with DAC when sustained GH elevation is the experimental requirement -- long-term animal studies, pharmacokinetic modeling, or research into sustained IGF-1 responses where weekly administration is logistically preferred. Be aware that the albumin-binding mechanism means plasma half-life in rodent models may differ from human data due to species differences in albumin-DAC reactivity.
FOR RESEARCH USE ONLY. All compounds referenced are supplied exclusively for in vitro and laboratory research by qualified scientists. Not intended for human or animal consumption, therapeutic use, or clinical application.