drug affinity complex comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
| 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.
At the pituitary, the peptide binds the growth hormone-releasing hormone receptor on somatotroph cells. Receptor activation raises intracellular cyclic AMP and triggers release of stored growth hormone. Somatostatin and other hypothalamic signals modulate this response. Negative feedback from insulin-like growth factor 1 also influences output. The same regulatory architecture operates with the native hormone. Whether the synthetic analog alters feedback dynamics over repeated exposure remains an open question. Most published receptor work uses cell models rather than intact human systems.
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.
CJC-1295 is a synthetic analogue of growth hormone-releasing hormone, built on the 29-amino-acid GHRH(1-29) fragment. Four substitutions distinguish it from the natural sequence: D-alanine at position 2, glutamine at position 8, alanine at position 15, and leucine at position 27. These changes reduce enzymatic cleavage and extend the peptide's persistence in circulation. The compound is discussed in two forms, one carrying a drug affinity complex and one without it.
The drug affinity complex is a maleimidopropionic acid group attached to a lysine side chain. It reacts with the free thiol of cysteine-34 on circulating albumin, forming a covalent bond. This conjugation keeps the peptide in the bloodstream and shields it from rapid renal filtration and proteolysis. Reported circulation half-lives for the albumin-bound form fall in the range of roughly six to nine days in early human studies.
Fibronectin type III domain-containing protein 5, the precursor of irisin, is a type I transmembrane glycoprotein that is encoded by the FNDC5 gene. Irisin is a cleaved version of FNDC5, named after the Greek messenger goddess Iris. Fibronectin domain-containing protein 5 is a membrane protein comprising a short cytoplasmic domain, a transmembrane segment, and an ectodomain consisting of a ~100 kDa fibronectin type III (FNIII) domain.
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Sources: en.wikipedia.org
Transamination is mediated by several types of aminotransferase enzymes. An aminotransferase may be specific for an individual amino acid, or it may be able to process any member of a group of similar ones, for example the branched-chain amino acids, which comprises valine, isoleucine, and leucine. The two common types of aminotransferases are alanine aminotransferase (ALT) and aspartate aminotransferase (AST).
1985–1987 – 1.3 L (1,296 cc) E3, 2 barrel, 8-valve, 74 PS (54 kW; 73 hp) Gross / 10.5 kg⋅m (103 N⋅m; 76 lb⋅ft) 1987–1989 – 1.3 L (1,323 cc) B3, 2 barrel, 8-valve, 67 PS (49 kW; 66 hp) Net / 10.4 kg⋅m (102 N⋅m; 75 lb⋅ft) 1985–1987 – 1.5 L (1,490 cc) E5, 2 barrel carburettor, 8-valve, 85 PS (63 kW; 84 hp) Gross / 12.3 kg⋅m (121 N⋅m; 89 lb⋅ft) Gross – Net rating 70 PS (51 kW; 69 hp) / 11.2 kg⋅m (110 N⋅m; 81 lb⋅ft) 1985–1987 – 1.5 L (1,490 cc) E5, EGi, 8-valve, 95 PS (70 kW; 94 hp) Gross/12.6 kg⋅m (124 N⋅m; 91 lb⋅ft) Gross – Net rating 76 PS (56 kW; 75 hp) / 11.6 kg⋅m (114 N⋅m; 84 lb⋅ft) 1985–1987 – 1.5 L (1,490 cc) E5T, turbo EGi, 8-valve, 115 PS (85 kW; 113 hp) Gross / 16.5 kg⋅m (162 N⋅m; 119 lb⋅ft) 1987–1989 – 1.5 L (1,498 cc) B5, 2 barrel, 12-valve, 76 PS (56 kW; 75 hp) Net / 11.4 kg⋅m (112 N⋅m; 82 lb⋅ft) 1987–1989 – 1.6 L (1,597 cc) B6, EGi, 8-valve, 85 PS (63 kW; 84 hp) Net / 12.5 kg⋅m (123 N⋅m; 90 lb⋅ft) 1986–1989 – 1.6 L (1,597 cc) B6D, EGi, 16-valve, 110 PS (81 kW; 108 hp) Net / 13.5 kg⋅m (132 N⋅m; 98 lb⋅ft) 1985–1989 – 1.6 L (1,597 cc) B6T, turbo EGi, 16-valve, 140 PS (103 kW; 138 hp) Net / 19.0 kg⋅m (186 N⋅m; 137 lb⋅ft) 1985–1989 – 1.7 L (1,720 cc) PN, diesel, 8-valve, 59 PS (43 kW; 58 hp) Gross / 10.8 kg⋅m (106 N⋅m; 78 lb⋅ft) Gross – Net rating 55 PS (40 kW; 54 hp) / 10.2 kg⋅m (100 N⋅m; 74 lb⋅ft), 1987–1989; Net rating: 58 PS (43 kW; 57 hp) / 10.7 kg⋅m (105 N⋅m; 77 lb⋅ft)
== U == Tito Ureta (1935–2012) Chilean biochemist at the University of Chile known for work on hexokinases. Merton F. Utter (1917–1980). American microbiologist and biochemist at Case Western Reserve University, known for work on intermediary metabolism. Member Natl. Acad. Sci. USA.
Sources: en.wikipedia.org
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.