This is a working overview of DAC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-10-13 and is reviewed periodically as new material appears.
CJC-1295 acts at the growth hormone-releasing hormone receptor, a G-protein-coupled receptor found on somatotroph cells in the anterior pituitary. Binding triggers a rise in cyclic AMP and calcium entry, which promotes release of stored growth hormone. Because the peptide mimics the body's own releasing hormone, it amplifies existing secretory pulses rather than driving continuous output. The size of the response therefore depends partly on the subject's own hormonal rhythm and feedback state.
The attached maleimide group explains the unusual duration of the DAC version. After injection it reacts with the thiol of cysteine-34 on serum albumin, forming a stable covalent bond. The resulting conjugate is too large for rapid kidney filtration and is shielded from many peptidases. Reported half-lives for this form reach several days, whereas the version without the group is cleared in roughly half an hour. That gap is the main pharmacological difference between the two.
Downstream of growth hormone, the liver and other tissues increase production of insulin-like growth factor 1, a mediator of many growth-promoting effects. Studies have documented elevated levels of both hormones after dosing, and the rise from the long-acting form persists longer than that produced by shorter-acting analogues. What remains unclear is whether sustained elevation of these markers translates into meaningful clinical benefit, and whether prolonged exposure carries risks that short trials could not detect.
CJC-1295 is a synthetic peptide designed to mimic growth hormone-releasing hormone (GHRH), the endogenous signal that prompts the pituitary gland to release growth hormone. The compound is a modified fragment of the natural hormone, spanning the first twenty-nine amino acids of GHRH with several substitutions that slow enzymatic breakdown. Two variants circulate in research settings: one carrying a drug affinity complex (DAC) and one without it. The DAC-free form is frequently labelled Mod GRF(1-29) in catalogs and discussion forums.
The peptide binds GHRH receptors on somatotroph cells within the anterior pituitary, triggering a signalling cascade that increases growth hormone secretion. Its improved resistance to dipeptidyl peptidase IV degradation distinguishes it from the parent hormone. In the DAC-bearing version, a maleimide group reacts with a cysteine residue on serum albumin, forming a covalent bond that keeps the peptide in circulation far longer. That albumin attachment is the central design feature separating the two research variants.
Pharmacokinetic behaviour differs sharply between the two forms. The DAC-bearing peptide shows an extended circulation time measured in days, whereas the version without the complex is cleared within roughly half an hour. This gap shapes how researchers design dosing schedules in animal models. Whether the prolonged presence of the DAC form produces effects meaningfully different from the short-acting variant remains an open question, since comparative human data are scarce.
| Property | Value | Notes |
|---|---|---|
| Primary target | GHRH receptor | G-protein-coupled receptor on pituitary somatotrophs |
| Half-life, long-acting form | Several days | Extended by covalent albumin binding |
| Half-life, short form | About 30 minutes | Cleared rapidly by peptidases and kidneys |
| Route in studies | Subcutaneous injection | Used in the published human trials |
| Main measured effect | Rise in GH and IGF-1 | Surrogate markers rather than clinical endpoints |
CJC-1295 is a synthetic peptide belonging to the growth hormone-releasing hormone analog family. It comprises twenty-nine amino acid residues derived from the N-terminal region of natural GHRH. The molecule incorporates several non-natural substitutions that increase resistance to enzymatic degradation. These modifications extend its activity compared with the native hormone fragment. Researchers use it to study pituitary growth hormone secretion in laboratory and clinical settings. This compound is distinct from native GHRH in its stability profile.
Two principal forms appear in the literature and in research supply. One carries a drug affinity complex, a maleimide-based group that forms a covalent bond with circulating albumin. This linkage slows clearance and produces a long-lasting elevation of peptide levels. The other form lacks that group and is often labeled MOD GRF(1-29). It has a much shorter circulation time. Both variants retain the same core receptor-binding sequence. Reported half-lives differ substantially between the two.
Characterization of this peptide relies on a small set of routine techniques. Reversed-phase high-performance liquid chromatography separates the target from truncated or oxidized by-products and yields a purity estimate when paired with ultraviolet detection near 214 nanometers. Mass spectrometry, either electrospray coupled to liquid chromatography or matrix-assisted laser desorption, confirms that the observed mass matches the value calculated for the expected sequence. Amino acid analysis, and enzymatic digestion followed by fragment mapping, are used when the sequence itself rather than the mass requires verification.
Stability depends heavily on physical state. A lyophilized powder kept dry, desiccated, and shielded from light typically holds its integrity for months to years at minus twenty degrees Celsius, and longer at minus eighty. Once dissolved, the peptide becomes far more vulnerable, since peptide bond hydrolysis, oxidation of susceptible residues, and aggregation all proceed faster in solution. Buffers near neutral pH are generally gentler than strongly acidic or alkaline conditions. Repeated freeze-thaw cycles and exposure to air-liquid interfaces during vigorous mixing cause losses that are easy to overlook.
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Platelets play an essential role in clotting. When the wall of a blood vessel is damaged, platelets adhere to the exposed surface at the site of injury and plug the gap. Simultaneous activation of the coagulation cascade results in the formation of fibrin, which reinforces the platelet plug to create a stable clot. A low platelet count, known as thrombocytopenia, may cause bleeding if severe. It can occur in individuals who are undergoing treatments that suppress the bone marrow, such as chemotherapy or radiation therapy, or taking certain drugs, such as heparin, that can induce the immune system to destroy platelets. Thrombocytopenia is a feature of many blood disorders, like acute leukaemia and aplastic anemia, as well as some autoimmune diseases. If the platelet count is extremely low, a platelet transfusion may be performed. Thrombocytosis, meaning a high platelet count, may occur in states of inflammation or trauma, as well as in iron deficiency, and the platelet count may reach exceptionally high levels in people with essential thrombocythemia, a rare blood disease. The platelet count can be reported in units of cells per microlitre of blood (/μL), 103 cells per microlitre (× 103/μL), or 109 cells per litre (× 109/L).
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=== Reticular dermis === The reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of dense irregular connective tissue featuring densely-packed collagen fibers. It is the primary location of dermal elastic fibers. The reticular region is usually much thicker than the overlying papillary dermis. It receives its name from the dense concentration of collagenous, elastic, and reticular fibers that weave throughout it. These protein fibers give the dermis its properties of strength, extensibility, and elasticity. Within the reticular region are the roots of the hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels. The orientation of collagen fibers within the reticular dermis creates lines of tension called Langer's lines, which are of some relevance in surgery and wound healing.
== Clinical significance == Proline hydroxylation requires ascorbic acid (vitamin C). The most obvious, first effects (gingival and hair problems) of absence of ascorbic acid in humans come from the resulting defect in hydroxylation of proline residues of collagen, with reduced stability of the collagen molecule, causing scurvy. Increased serum and urine levels of hydroxyproline have also been demonstrated in Paget's disease. Mass spectrometry analysis showed decreased amount of hydroxyproline post-translational modifications in non inflamed tissue from ulcerative colitis patients when compared to tissue from donors without the disease.
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It binds the growth hormone-releasing hormone receptor on pituitary somatotroph cells. Receptor activation raises cyclic AMP and promotes release of stored growth hormone granules. Because the peptide persists longer than natural releasing hormone, stimulation is prolonged rather than brief.
The drug affinity complex links the peptide to serum albumin through a covalent bond. The conjugate is too large to be filtered quickly by the kidneys and is shielded from enzymatic breakdown. This extends the apparent half-life from roughly minutes to several days.
Long-term safety and any clinical benefit are unestablished. Published human data cover small groups over limited periods and focus on hormone levels rather than health outcomes. Whether prolonged elevation of growth hormone and insulin-like growth factor 1 is beneficial or harmful is an open question.
The synthetic peptide keeps the receptor-binding region of GHRH but carries substitutions that resist enzymatic cleavage. In the DAC version, an added group also anchors the molecule to albumin, extending its presence in the bloodstream.