CJC-1295 Without DAC: Research Profile

Palmetto Peptides Research Team

February 22, 2026

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CJC-1295 Without DAC — also known as Modified GRF 1-29 or Mod GRF 1-29 — is a 29-amino acid peptide analog of growth hormone-releasing hormone (GHRH). Unlike its counterpart CJC-1295 with DAC, this version does not contain a Drug Affinity Complex, meaning it produces sharp, pulsatile spikes in growth hormone (GH) secretion that closely mimic the body's natural GH release pattern. It is one of the most studied GHRH analogs in the research literature.

What Is CJC-1295 Without DAC?

CJC-1295 Without DAC is derived from the first 29 amino acids of endogenous GHRH (GHRH 1-29), with four amino acid substitutions that increase metabolic stability. These substitutions prevent enzymatic cleavage by dipeptidylpeptidase IV (DPP-IV), extending the peptide's biological half-life from approximately 2 minutes (native GHRH) to approximately 30 minutes in plasma.

The four key substitutions in Mod GRF 1-29 are:

Position 2: Alanine replaced by D-Alanine (DPP-IV resistance)
Position 8: Asparagine replaced by Glutamine (prevents asparagine deamidation)
Position 15: Glycine replaced by Alanine (increases stability)
Position 27: Methionine replaced by Leucine (prevents oxidation)

These modifications preserve full GHRH receptor binding affinity while dramatically improving the peptide's plasma stability — a key consideration in research applications.

Mechanism of Action

CJC-1295 Without DAC works by binding to GHRH receptors (GHRHR) on somatotroph cells in the anterior pituitary gland. Upon binding, it activates adenylate cyclase, increasing intracellular cyclic AMP (cAMP) concentrations. This triggers a signaling cascade that results in GH synthesis and secretion.

Pulsatile vs. Continuous GH Release

Because Mod GRF 1-29 lacks the DAC component, it does not bind to albumin in plasma. This results in a distinct pharmacokinetic profile: GH levels rise sharply within 15–30 minutes of administration and return to baseline within 2–3 hours. This pulsatile pattern is considered physiologically normal and is favored in research contexts where mimicking natural GH secretion rhythms is important.

Synergy with GHRPs

Researchers frequently combine Mod GRF 1-29 with growth hormone-releasing peptides (GHRPs) such as Ipamorelin, GHRP-2, or GHRP-6. These two classes of compounds act on different but complementary receptors — GHRHR and GHSR-1a respectively — and have been shown in animal studies to produce synergistic increases in GH pulse amplitude far exceeding what either compound produces alone.

Research Findings

GH and IGF-1 Elevation

Multiple preclinical studies have examined the effects of GHRH analogs on GH and insulin-like growth factor 1 (IGF-1) levels. Research using Mod GRF 1-29 analogs in rodent models demonstrated dose-dependent increases in pulsatile GH secretion, with IGF-1 levels rising in proportion to cumulative GH exposure. Frohman et al. (1984) established foundational pharmacokinetics of GHRH 1-29 analogs, demonstrating that the first 29 amino acids retain full receptor binding activity.

Body Composition Research

Animal model studies examining GHRH analog administration have reported changes in lean mass and adiposity measures. Research in rodents demonstrated that sustained GHRH receptor stimulation was associated with increased lean body mass and reduced fat mass in aged animals, suggesting a role in reversing age-related GH secretion decline. These findings have driven significant scientific interest in GHRH analogs as research tools for studying somatotropic axis modulation.

Combination Studies with GHRPs

Research published in the Journal of Clinical Endocrinology & Metabolism demonstrated that co-administration of GHRH analogs with GHRPs produced synergistic GH release in both healthy subjects and patients with GH deficiency. The mechanistic basis for this synergy has been extensively studied — GHRPs increase somatotroph sensitivity to GHRH while simultaneously reducing somatostatin tone.

Research Protocols

In preclinical research settings, CJC-1295 Without DAC is typically studied as a lyophilized powder reconstituted in bacteriostatic water (BAC Water) immediately prior to use. Research protocols commonly examine the compound's effects in the context of pulsatile administration, as the short half-life makes it well-suited for studies requiring defined GH pulse induction.

Storage of reconstituted peptide requires refrigeration (2–8°C) and protection from light. Lyophilized powder maintains stability at room temperature for short-term storage but benefits from cold storage for long-term preservation. Standard research practice involves use within 28 days of reconstitution when stored under appropriate conditions.

CJC-1295 Without DAC vs. With DAC: Key Research Differences

The fundamental distinction between the two CJC-1295 variants lies in GH secretion pattern:

Without DAC (Mod GRF 1-29): Short half-life (~30 min), produces physiological GH pulses. Research applications favor this version when studying pulsatile GH physiology or when researchers require precise timing of GH elevation.
With DAC: Extended half-life (5–7 days), produces sustained, blunted GH elevation. Suited for research examining chronic GHRH receptor activation and steady-state IGF-1 effects.

Neither variant is superior in absolute terms — the choice depends on the specific research question being investigated.

Frequently Asked Questions

What distinguishes Mod GRF 1-29 from native GHRH 1-29?

Mod GRF 1-29 contains four strategic amino acid substitutions that confer DPP-IV resistance and prevent oxidative degradation, extending plasma half-life from ~2 minutes to ~30 minutes while retaining full receptor binding affinity.

Why do researchers combine Mod GRF 1-29 with GHRPs?

GHRH analogs and GHRPs operate via distinct but complementary mechanisms. GHRH analogs stimulate GH synthesis and secretion at the receptor level, while GHRPs reduce somatostatin inhibition and directly stimulate GHSR-1a receptors. Combined administration produces markedly greater GH pulse amplitude than either compound alone.

What is the difference between Mod GRF 1-29 and Sermorelin?

Sermorelin is GHRH 1-29 without the stability-enhancing substitutions, making it susceptible to DPP-IV cleavage. Mod GRF 1-29 represents a more stable, research-grade refinement of the same 29-amino acid sequence.

References

Frohman LA, et al. (1984). Characterization of growth hormone-releasing factor activity of a synthetic peptide corresponding to the amino-terminal segment of the hypothalamic factor. Biochemical and Biophysical Research Communications. PMID: 6145128
Jaffe CA, et al. (1993). Regulatory mechanisms of growth hormone secretion are sexually dimorphic. Journal of Clinical Investigation. PMID: 8440476
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. PMID: 16464938

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