Category: Research Peptides | Reading time: 6 min | For research use only
CJC-1295 is a synthetic analogue of growth hormone releasing hormone (GHRH) that appears in the research literature in two distinct forms: CJC-1295 without DAC (also known as Modified GRF 1-29 or Mod GRF 1-29) and CJC-1295 with DAC. Despite sharing a common peptide backbone, the two forms differ fundamentally in their pharmacokinetic profiles — a distinction with direct consequences for experimental design.
Confusion between these two compounds is among the most common sources of error in growth hormone axis research. This article clarifies their structural differences, pharmacokinetic profiles, and respective research applications.
Background: Natural GHRH and Its Limitations as a Research Tool
Natural human GHRH is a 44-amino acid peptide released from the hypothalamus in pulses, traveling via the hypothalamic-pituitary portal system to stimulate GH synthesis and release from anterior pituitary somatotrophs. Its biologically active fragment is GHRH(1–29) — the first 29 amino acids contain the full receptor-binding and activation activity of the intact molecule.
Native GHRH(1–29) is poorly suited as a research tool due to rapid enzymatic degradation. Dipeptidyl peptidase IV (DPP-IV) cleaves the Ala²-Asp³ bond within minutes of administration in vivo, producing a half-life of approximately 7 minutes. This instability motivated the development of stabilized analogues — which is where CJC-1295 No DAC and CJC-1295 with DAC originate.
Molecular Profiles
CJC-1295 No DAC (Modified GRF 1-29)
- Also known as: Mod GRF 1-29, Modified GRF(1-29), CJC-1295 without DAC
- Sequence: GHRH(1–29) with four amino acid substitutions
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Key substitutions:
- Position 2: Ala → D-Ala (DPP-IV resistance)
- Position 8: Asn → Gln (oxidative stability)
- Position 15: Gly → Ala (increased receptor affinity)
- Position 27: Met → Nle (oxidative stability)
- Molecular weight: ~3,036 g/mol
- Half-life: 30–60 minutes
- Form: Lyophilized powder (research grade)
CJC-1295 with DAC
- Also known as: CJC-1295 DAC, DAC:GRF
- Sequence: Same Modified GRF 1-29 backbone + Drug Affinity Complex (DAC) moiety
- DAC modification: Lysine-maleimide group added at position 30 (C-terminus extension)
- Mechanism of extended half-life: DAC moiety forms a reversible covalent bond with serum albumin after administration, using albumin as a circulating depot
- Molecular weight: ~3,367 g/mol
- Half-life: ~6–8 days
- Form: Lyophilized powder (research grade)
The sole structural difference is the DAC moiety — a maleimide-modified lysine residue appended to the C-terminus. This addition does not alter receptor binding at the GHRH receptor but dramatically changes how the compound behaves pharmacokinetically in vivo.
Pharmacokinetics: The Critical Difference
Understanding the pharmacokinetic profiles of both forms is essential for interpreting published research and designing experiments correctly.
CJC-1295 No DAC — Pulsatile Profile
With a half-life of 30–60 minutes, CJC-1295 No DAC produces a sharply defined GH release pulse following administration. The compound reaches peak pituitary GHRH receptor occupancy rapidly, stimulates a GH pulse, and is then cleared — closely mimicking the pulsatile pattern of endogenous GHRH action.
This profile is used in research contexts where:
- Pulse kinetics are the experimental variable of interest
- Preservation of natural GH pulsatility is important for the model
- Short-duration GHRH receptor stimulation is required
- Frequent administration intervals are acceptable in the experimental design
Published research using Mod GRF 1-29 has focused on pituitary responsiveness, somatostatin interplay, and GH pulse amplitude characterization in animal models.
CJC-1295 with DAC — Sustained Profile
The DAC moiety fundamentally alters the compound's behavior. After administration, the maleimide group reacts with a cysteine-34 residue on serum albumin (the most abundant plasma protein), forming a reversible covalent bond. The albumin-bound CJC-1295 DAC:
- Is protected from enzymatic degradation
- Is too large to be renally filtered
- Slowly dissociates from albumin, providing sustained GHRH receptor stimulation
- Produces measurable GH and IGF-1 elevation over 6–8 days from a single administration
The landmark clinical pharmacology study by Teichman et al. (2006) in the Journal of Clinical Endocrinology & Metabolism demonstrated dose-dependent increases in mean 24-hour GH concentrations and sustained IGF-1 elevation lasting up to 14 days following single-dose CJC-1295 DAC administration in healthy adult subjects.
GH Secretion Patterns: Pulsatile vs Sustained
This is the most consequential practical distinction for researchers:
| Parameter | CJC-1295 No DAC | CJC-1295 with DAC |
|---|---|---|
| GH release pattern | Acute pulse | Sustained elevation |
| Peak GH response | High, narrow | Lower, broad |
| IGF-1 elevation | Short duration | Sustained days |
| Somatostatin interaction | Pulse-sensitive | Partially bypassed |
| Administration frequency | Multiple times per week | Once weekly (in animal models) |
| Experimental design | Pulse kinetics models | Chronic stimulation models |
The distinction matters because GH pulsatility itself is biologically significant. Natural GH is secreted in pulses, and many downstream effects (including differential gene expression patterns in liver) are pulse-frequency and pulse-amplitude dependent. CJC-1295 No DAC preserves pulsatility; CJC-1295 with DAC blunts it in favor of sustained tonic stimulation. Neither profile is inherently superior — the correct choice depends on the research question.
Naming Confusion in the Literature
A significant source of confusion in published and gray literature concerns nomenclature. The compound now commonly called "CJC-1295" in research supply contexts often refers specifically to the DAC form, while "Modified GRF 1-29" or "Mod GRF 1-29" refers to the No DAC form. However, usage is inconsistent across sources.
Researchers should verify which form is being discussed in any publication or protocol by checking:
- Molecular weight reported (3,036 g/mol = No DAC; 3,367 g/mol = with DAC)
- Half-life cited (minutes = No DAC; days = with DAC)
- Administration frequency in the experimental design (frequent = No DAC; weekly = with DAC)
- Whether the DAC or maleimide modification is explicitly described
When ordering for research purposes, always confirm with the supplier whether the product is the DAC or No DAC form. These are not interchangeable compounds for experimental purposes.
Research Applications by Form
CJC-1295 No DAC — Recommended for:
- Studies examining acute GH pulse dynamics
- Experiments where natural pulsatility must be preserved or mimicked
- Short-duration intervention models
- Protocols requiring precise timing of GH elevation relative to experimental measurements
- Research combined with Ipamorelin (GHSR agonist) to model dual-pathway pulsatile GH stimulation
CJC-1295 with DAC — Recommended for:
- Chronic GH axis stimulation models
- Long-term body composition research in animal models
- Studies where sustained IGF-1 elevation is the experimental target
- Protocols requiring infrequent administration (once weekly or less)
- Pharmacokinetic studies of albumin-binding peptide drug delivery mechanisms
Combined Use with Ipamorelin
Both CJC-1295 forms are studied in combination with Ipamorelin, a selective ghrelin receptor agonist that stimulates GH release through the GHSR pathway independently of GHRH. The combination provides dual-pathway stimulation:
- CJC-1295 No DAC + Ipamorelin: models acute pulsatile dual-pathway GH stimulation; both compounds have compatible short-to-medium duration profiles
- CJC-1295 DAC + Ipamorelin: the pharmacokinetic profiles are mismatched — CJC-1295 DAC provides sustained background stimulation while Ipamorelin provides additional acute pulses; this combination produces a different GH secretion pattern than either form with Ipamorelin alone
Researchers designing combination protocols should account for these kinetic differences in their experimental models.
Key Published Research
- Teichman SL, et al. (2006). Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology & Metabolism, 91(3), 799–805.
- Jetté L, et al. (2005). hGRF1–29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: a potential long-acting GRF analog. Endocrinology, 146(7), 3052–3058.
- Alba M, et al. (2006). Once-monthly administration of CJC-1295, a long-acting growth hormone-releasing hormone analog, maintains elevated IGF-1 levels in dogs. American Journal of Physiology — Endocrinology and Metabolism, 291(6), E1250–E1254.
- Ionescu M & Frohman LA. (2006). Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. Journal of Clinical Endocrinology & Metabolism, 91(12), 4792–4797.
Storage and Handling Notes
Both forms are supplied as lyophilized powders and follow standard peptide storage protocols:
- Store at −20°C unopened
- Protect from light and moisture
- Reconstitute with sterile or bacteriostatic water
- Aliquot reconstituted solution immediately; avoid repeated freeze-thaw cycles
- Confirm lot number matches COA before use
Note that CJC-1295 DAC contains a maleimide functional group which is reactive toward thiol-containing compounds. Avoid reconstitution in solvents or buffers containing free thiol groups (e.g., DTT, β-mercaptoethanol) as these will react with the DAC moiety and inactivate the albumin-binding mechanism.
NordBioLab supplies both CJC-1295 No DAC and CJC-1295 with DAC as research-grade lyophilized peptides with ≥98% purity (HPLC verified) and full COA documentation per batch.
View CJC-1295 No DAC in our catalog →
All products and information provided by NordBioLab are strictly for scientific research and laboratory use only. Not for human or veterinary consumption. This article does not constitute medical advice.