CJC-1295 DAC Peptide

CJC-1295 DAC (Drug Affinity Complex) is a synthetic analog of growth hormone-releasing hormone (GHRH) with a DAC modification that extends its half-life to approximately 6-8 days. This prolonged duration enables sustained elevation of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) levels, making it a key compound in endocrine research.

The DAC modification binds to serum albumin via a reactive chemical group, significantly reducing renal clearance and enabling less frequent dosing protocols in research settings compared to CJC-1295 without DAC (Modified GRF 1-29).

CJC-1295 DAC acts as a GHRH analog, binding to the GHRH receptor (GHRHR) on anterior pituitary somatotroph cells. This triggers a signaling cascade via the cAMP/PKA pathway, stimulating the synthesis and pulsatile release of growth hormone.

The DAC moiety consists of a maleimidopropionic acid (MPA) linker conjugated to lysine, which undergoes a Michael reaction with Cys34 on albumin. This albumin binding reduces proteolytic degradation and renal filtration, extending the peptide's functional half-life from ~30 minutes (without DAC) to approximately 6-8 days.

CJC-1295 DAC is a synthetic analog of growth hormone-releasing hormone (GHRH), engineered to combine the truncated bioactive GHRH(1-29) sequence with four amino acid substitutions and a C-terminal maleimidopropionic acid (MPA) linker that forms a Drug Affinity Complex (DAC) with circulating serum albumin. This rational design extends the in vivo half-life from minutes (native GHRH) to multiple days in preclinical models.

Primary structure: Tyr-D-Ala-Asp-Ala-Ile-Phe-Thr-Gln-Ser-Tyr-Arg-Lys-Val-Leu-Ala-Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Leu-Ser-Arg-Lys(MPA)-NH2. The four key substitutions relative to native GHRH(1-29) are D-Ala²(resistance to DPP-IV cleavage), Gln⁸ (resistance to asparagine deamidation/cleavage by trypsin-like proteases), Ala¹⁵ (enhanced amphipathic α-helix stability), and Leu²⁷ (resistance to oxidation of the native Met residue). The C-terminal lysine carries the MPA group, whose maleimide reacts selectively with the free thiol of Cys-34 on human serum albumin, generating a covalent thioether bond and albumin-bound depot.

Physical and chemical parameters:

• Molecular formula: C₁₆₅H₂₆₉N₄₇O₄₆
• Molecular weight: ~3647.28 g/mol (monoisotopic mass ~3644.0 Da)
• CAS number: 863288-34-0
• Appearance: White to off-white lyophilized powder
• Purity: ≥98% by reverse-phase HPLC (typical research-grade specification)
• Net charge at pH 7.0: approximately +2 to +3, due to multiple Arg/Lys residues partially offset by Asp residues
• Isoelectric point (pI): ~9.7 (predicted)
• Solubility: Soluble in sterile water, bacteriostatic water, and dilute acetic acid; limited solubility in non-polar organic solvents
• C-terminus: Amidated (-NH2), enhancing receptor recognition and proteolytic stability

Structural and pharmacological context: The peptide adopts an amphipathic α-helical conformation across residues 6-29, which is critical for binding the GHRH receptor (GHRH-R), a class B G-protein-coupled receptor expressed on anterior pituitary somatotrophs. Receptor activation engages Gαs, elevating intracellular cAMP and stimulating pulsatile growth hormone release in preclinical models. The MPA-mediated albumin conjugation does not abolish receptor binding because albumin-bound peptide can still engage GHRH-R, though with altered pharmacokinetics — the depot effect prolongs systemic exposure and shifts pulsatile GH secretion toward more sustained release patterns in animal studies (Teichman et al., 2006).

Analytical characterization: Quality control of research-grade material typically includes RP-HPLC for purity and identity, ESI- or MALDI-mass spectrometry for intact-mass confirmation, amino acid analysis or sequencing for primary structure verification, and tests for water content (Karl Fischer), residual TFA (counter-ion), and bacterial endotoxin. The presence of an intact, reactive maleimide can be verified by Ellman's assay following reaction with a thiol-containing probe such as cysteine or glutathione.

Research applications: CJC-1295 DAC is used in vitro and in preclinical animal models to study GHRH-R signaling, somatotroph axis regulation, IGF-1 dynamics, and albumin-conjugation pharmacokinetic strategies. This material is supplied for laboratory research use only and is not intended for human or veterinary administration.

Proper reconstitution of CJC-1295 DAC is critical for preserving structural integrity, maleimide reactivity, and analytical performance in downstream research applications. The 30-amino acid peptide is supplied lyophilized and must be solubilized prior to use under conditions that minimize mechanical shear, oxidative exposure, and pH excursions.

Recommended diluent: Bacteriostatic water for injection (0.9% benzyl alcohol in sterile water) is the standard reconstitution medium for research handling, providing antimicrobial protection during the multi-day post-reconstitution window. Sterile water for injection or 0.9% sodium chloride may also be used, but these lack preservatives and require shorter use windows. Avoid alkaline buffers, as elevated pH accelerates hydrolysis of the maleimidopropionic acid linker to the inert maleamic acid form, which abolishes the DAC mechanism of albumin conjugation.

Step-by-step procedure:

• Equilibrate: Remove the lyophilized vial from -20°C storage and allow it to reach room temperature (15-20 minutes) before opening. Cold vials accumulate atmospheric moisture on the lyophilate, which can cause clumping and incomplete dissolution.
• Sanitize: Wipe the rubber septum of both the peptide vial and diluent vial with 70% isopropanol and allow to air-dry.
• Calculate volume: Choose a reconstitution volume that yields a convenient working concentration (commonly 1-2 mg/mL). For a 2 mg vial reconstituted with 2 mL diluent, the resulting concentration is 1 mg/mL.
• Inject slowly: Using a sterile syringe, draw the diluent and inject it slowly down the inner wall of the vial. Direct injection onto the lyophilate cake produces foaming, mechanical shear, and aggregation.
• Dissolve passively: Allow the vial to stand undisturbed for 5-10 minutes. Gently swirl — do NOT shake or vortex. Shear forces can disrupt the peptide's secondary structure and degrade the reactive maleimide group.
• Inspect: The final solution should be clear, colorless, and free of visible particulates. Cloudiness, fibrils, or color indicates aggregation or contamination; discard the vial.

Concentration verification: For quantitative research, confirm post-reconstitution concentration by UV absorbance (A280, using ε calculated from Tyr/Trp content) or by RP-HPLC against a reference standard. Mass spectrometry can confirm intact-mass identity and detect early hydrolysis of the MPA linker (mass shift of +18 Da).

Handling precautions: Wear nitrile gloves, lab coat, and safety eyewear. Work in a clean laminar-flow hood when sterility is required for cell culture or in vitro receptor binding studies. Use low-protein-binding polypropylene tubes for aliquoting, as the amphipathic peptide can adsorb to high-binding surfaces at low concentrations, leading to underestimation of the true working concentration. CJC-1295 DAC is intended strictly for in vitro laboratory research and is not approved for human or animal administration.

CJC-1295 DAC (Drug Affinity Complex) requires careful storage to preserve its structural integrity and the integrity of the maleimidopropionic acid (MPA) linker that mediates albumin conjugation. The peptide is supplied as a lyophilized powder, which is the most stable physical form for long-term storage. Lyophilization removes bulk water and reduces hydrolytic and oxidative degradation pathways that can compromise the 30-residue sequence, the C-terminal amide, and the reactive maleimide functionality responsible for the extended half-life.

Long-term storage (lyophilized): Store the sealed vial at -20°C or colder for periods up to 24 months. For extended archival storage exceeding 12 months, -80°C is preferable, as lower temperatures further suppress residual moisture-driven hydrolysis of peptide bonds (notably Asp-Gly and Asn-Xaa motifs) and Met/Trp oxidation. Keep vials desiccated and protected from light, which can promote photo-oxidation of aromatic residues (Tyr, Phe) within the GHRH(1-29) backbone.

Short-term storage prior to reconstitution: Brief storage at 2-8°C (up to several weeks) is acceptable provided the vial remains sealed and desiccated. Always allow the vial to equilibrate to room temperature before opening to prevent atmospheric moisture from condensing onto the lyophilate, which can accelerate degradation and impair reconstitution behavior.

Post-reconstitution storage: Once dissolved in bacteriostatic water (0.9% benzyl alcohol) or sterile water, store the solution at 2-8°C and use within approximately 21 days when bacteriostatic diluent is employed. With non-preserved sterile water, the working window is substantially shorter (typically 24-72 hours) due to the absence of antimicrobial protection. Reconstituted solutions should remain clear; any visible precipitate, cloudiness, or color change indicates aggregation or degradation and the material should be discarded.

Stability considerations specific to CJC-1295 DAC:

• Maleimide reactivity: The MPA group is electrophilic and slowly hydrolyzes to a non-reactive maleamic acid at neutral to alkaline pH. Storage at acidic to neutral pH in lyophilized form maximizes preservation of the maleimide moiety, which is essential for in vivo albumin conjugation.
• Freeze-thaw avoidance: Repeated freeze-thaw cycles of reconstituted solution induce aggregation and loss of bioactivity. Aliquoting into single-use research volumes before freezing minimizes this issue.
• Light protection: Use amber vials or wrap in foil to mitigate photodegradation.
• Adsorption: At low concentrations, the peptide can adsorb to glass and plastic surfaces. Use low-binding polypropylene tubes and avoid extensive dilution prior to use.

For analytical confirmation of stability over time, RP-HPLC and mass spectrometry are recommended to monitor parent peak integrity, maleimide hydrolysis, oxidation products, and aggregate formation. This material is intended for in vitro laboratory research use only and is not for human or veterinary administration.