DAC linker 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 2025-12-06. Numbers and descriptions here follow the published literature rather than marketing material.
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 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.
Lyophilized material is generally stable for extended periods when held at minus twenty degrees Celsius or below and protected from moisture and light. In solution the peptide is more labile; bond hydrolysis, aggregation and oxidation of susceptible residues all proceed faster at ambient temperature. Repeated freeze and thaw cycles should be avoided because they promote clumping and loss of soluble material. The conjugated variant adds a further consideration, since the maleimide group can hydrolyze in aqueous buffer and lose its ability to react with albumin.
Laboratory handling centers on minimizing exposure to water, heat and oxygen before use. Working solutions are typically prepared in sterile water or a mild buffer, and any residual particulate matter is removed by filtration. When the powder dissolves slowly, a small proportion of acetonitrile or dilute acetic acid is sometimes added as a co-solvent. Containers are kept sealed and desiccated between uses. Records of lot number, reconstitution date and storage conditions support later comparison of results across experiments.
Identity and purity are established with reversed phase high performance liquid chromatography coupled to mass spectrometry. The chromatographic step separates the target peptide from truncated sequences and deletion products, while the mass measurement confirms the expected molecular weight to within a fraction of a dalton. Because the two common variants differ by the presence of the linker, mass alone can distinguish them in the unconjugated state. Amino acid analysis and peptide mapping are used when sequence level confirmation is required.
| 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 |
Both forms act at the pituitary receptor for growth hormone-releasing hormone and increase growth hormone output, which in turn raises insulin-like growth factor 1. A long-acting analog produces sustained rather than pulsatile stimulation, and the physiological consequences of that pattern are not fully settled. Published human data on the extended form remain limited, and much of what circulates in discussion traces to early company reports rather than independent replication. How sustained exposure affects normal feedback remains an open question.
The distinguishing feature of the DAC form is a maleimide-containing group that reacts with the free thiol of cysteine-34 on human serum albumin. This reaction forms a covalent bond without enzymatic assistance, and it takes place after the peptide enters the bloodstream. Because albumin is abundant and long-lived, the attached peptide is carried through circulation far longer than an unmodified fragment would survive. The chemistry is a deliberate pharmacokinetic strategy rather than a change to receptor activity.
The compound emerged from work at a Canadian biotechnology firm in the early 2000s. Early human studies examined its effect on growth hormone and insulin-like growth factor 1 in healthy volunteers and in people with HIV-associated fat redistribution. Reports described sustained increases in both markers after a single injection. Development did not advance to regulatory approval, and the clinical programme was later discontinued. The molecule is now encountered mainly as a research chemical rather than a marketed medicine.
Two forms circulate in research settings and are frequently confused. One carries the drug affinity complex and is often written as CJC-1295 with DAC; the other lacks that group and is usually called modified GRF(1-29). The two share the same core sequence but differ sharply in how long they persist in blood. Products labelled only as CJC-1295 normally refer to the version carrying the complex. Documentation that omits the distinction leaves the intended molecule ambiguous.
CJC-1295 belongs to a class of synthetic peptides modeled on growth hormone releasing hormone, a forty-four amino acid signal produced by the hypothalamus. The compound is built from the first twenty-nine residues of the natural sequence, with four substitutions introduced at positions 2, 8, 15 and 27. These changes were designed to slow enzymatic breakdown while preserving receptor activation. The result is a peptide that is shorter than native GHRH and considerably more resistant to ordinary clearance pathways in circulation.
Two related forms appear under the CJC-1295 name. The simpler analogue, commonly written as modified GRF(1-29), carries the four substitutions but no additional conjugation. The second form attaches a maleimidopropionic acid linker to a lysine residue, a modification frequently called the drug affinity complex. That linker reacts with the free thiol on serum albumin to form a covalent bond. Because albumin has a long residence time in blood, the conjugated peptide stays in circulation far longer than the unconjugated analogue.
=== Males === Males are smaller in size than females, and winged. Their body ranges 17.7 to 23.4mm in length, however their tegmina and wings are longer than their body giving them the appearance of bigger size, their overall length is 28.5 to 33.5mm. Tegmina are slightly translucent, light brownish yellow in color, with brown random speckling throughout. Variation in speckling can occur, with some individuals having reduced or limited spotting. The wings are similar in color as the tegmina. The males' body color is significantly lighter than the females, being light yellow to tan.
However, the National Gazette had previously run articles detailing the struggling conditions in Sichuan; exacerbated by heavy war taxes and drought, desperate peasantry were allegedly eating grass, bark, and even resorting to cannibalism. Liu Wenhui admitted himself that anti-government unrest had occurred in Rongxian and Yibin. The National Gazette reported that students from Rongxian had submitted a petition listing the exorbitant taxes imposed on them; many of Liu Wenhui's fees were similar or even identical to those levied by Liu Chengxun, including the 5,000-yuan "revolution tax". Similar complaints and petitions to Liu Wenhui from local residents were recorded denouncing Liu Wencai's taxation regime in 1925 and around 1927. According to the 1927 letter, Liu Wencai had collaborated with Tan Xiaolou and become director of taxation bureaus. Liu Wencai exacted many inventive forms of payment, including a "flower tax" for prostitutes, fees to pay for wounded soldiers, and several other miscellaneous taxes on such varied articles as hoes, toilets, stamps, and clothing. Liu Wencai had also engaged in speculation, monopolizing the supply of various medicinal herbs to sell them at high prices. After the 24th Army launched an auction of public properties in 1927, Liu Wencai used several different aliases in order to purchase the bulk of the real estate for sale. Slogans targeting Liu Wencai had also appeared in the streets of Yibin. However, Liu Wenhui did not take action against his brother.
The trial, carried out between 1946 and 1947, aimed to test the efficacy of the chemical streptomycin for curing pulmonary tuberculosis. The trial was both double-blind and placebo-controlled. The methodology of clinical trials was further developed by Sir Austin Bradford Hill, who had been involved in the streptomycin trials. From the 1920s, Hill applied statistics to medicine, attending the lectures of renowned mathematician Karl Pearson, among others. He became famous for a landmark study carried out in collaboration with Richard Doll on the correlation between smoking and lung cancer. They carried out a case-control study in 1950, which compared lung cancer patients with matched control and also began a sustained long-term prospective study into the broader issue of smoking and health, which involved studying the smoking habits and health of more than 30,000 doctors over a period of several years. His certificate for election to the Royal Society called him "the leader in the development in medicine of the precise experimental methods now used nationally and internationally in the evaluation of new therapeutic and prophylactic agents". The ethics of selecting clinical trial subjects have been controversial for much of their modern history, especially in the United States. From the 1950s up until the early 1970s, the vast majority of pharmaceutical testing in America was performed on prison populations; only after widespread abuse during testing was reported at the Holmesburg Prison did research diminish in these areas.
=== DMPK, ADME, and bioanalysis === BioDuro conducts in vitro ADME assays, in vivo PK/TK studies, metabolic stability studies, and bioanalytical method development using LC–MS/MS platforms. These services are used to characterize compound absorption, distribution, metabolism, and excretion profiles during preclinical development.
Sources: en.wikipedia.org
Following the first presidential debate of the general election, in which Obama's performance was considered surprisingly lackluster, his lead over Romney collapsed, putting pressure on Biden to stop the bleeding with a strong showing against the Republican vice-presidential nominee, Paul Ryan. Some political analysts considered Biden's performance in the October 11 vice-presidential debate one of the best of his career and a key factor in Obama's rebound in the polls and eventual victory. The debate also became memorable for the popularization of Biden's use of the phrase "a bunch of malarkey" in response to an attack by Ryan on the administration's response to the attacks on the U.S. embassy in Benghazi in September. Biden reused the phrase during his 2020 presidential campaign. On November 6, Obama and Biden were reelected.
However, that 2006 review pre-dates recent data, which, although still too soon to be certain, suggest that the increase in childhood obesity in the US, the UK, and Sweden might be abating.3–5 A British longitudinal study has found that obesity restricted to childhood has minimal influence on adult outcomes at age 30. The study also found that, while obesity that continues into adulthood has little influence on men's outcomes, it makes women less likely to have ever been employed or to currently have a romantic partner. A 2017 National Bureau of Economic Research paper found that childhood obesity in the United States increases medical costs by $1,354 a year (in 2013 dollars).
== Epidemiology == ALD has not been shown to have an increased incidence in any specific country or ethnic group. In the United States, the incidence of affected males is estimated at 1:21,000. Overall incidence of hemizygous males and carrier females is estimated at 1:16,800. The reported incidence in France is estimated at 1:22,000.
== Health economics == Economic analyses suggest that TOPS may be cost-effective compared with fusion. These findings are based on improvements in quality of life, faster recovery, and reduced need for reoperation over time.
Once the peptide chain is synthesized, it still must be modified. Post-translational modifications can occur before protein folding or after. Common biological methods of modifying peptide chains after translation include methylation, phosphorylation, and disulfide bond formation. Methylation often occurs to arginine or lysine and involves adding a methyl group to a nitrogen (replacing a hydrogen). The R groups on these amino acids can be methylated multiple times as long as the bonds to nitrogen does not exceed 4. Methylation reduces the ability of these amino acids to form hydrogen bonds so arginine and lysine that are methylated have different properties than their standard counterparts. Phosphorylation often occurs to serine, threonine, and tyrosine and involves replacing a hydrogen on the alcohol group at the terminus of the R group with a phosphate group. This adds a negative charge on the R groups and will thus change how the amino acids behave in comparison to their standard counterparts. Disulfide bond formation is the creation of disulfide bridges (covalent bonds) between two cysteine amino acids in a chain which adds stability to the folded structure.
Sources: en.wikipedia.org
=== Immune response === Cortisol prevents the release of substances in the body that cause inflammation. Cortisol is used to treat conditions resulting from overactivity of the B-cell-mediated antibody response. Examples include inflammatory and rheumatoid diseases, as well as allergies. Low-dose topical hydrocortisone, available as a nonprescription medicine in some countries, is used to treat skin problems such as rashes and eczema. Cortisol inhibits production of interleukin 12 (IL-12), interferon gamma (IFN-gamma), IFN-alpha, and tumor necrosis factor alpha (TNF-alpha) by antigen-presenting cells (APCs) and T helper cells (Th1 cells), but upregulates interleukin 4, interleukin 10, and interleukin 13 by Th2 cells. This change results in a shift toward a Th2 immune response rather than general immunosuppression. The activation of the stress system (and resulting increase in cortisol and Th2 shift) seen during an infection is believed to be a protective mechanism which prevents an over-activation of the inflammatory response. Cortisol can weaken the activity of the immune system. Cortisol prevents proliferation of T-cells by rendering the interleukin-2 producer T-cells unresponsive to interleukin-1, and unable to produce the T-cell growth factor IL-2. Cortisol downregulates the expression of the IL2 receptor IL-2R on the surface of the helper T-cell which is necessary to induce a Th1 'cellular' immune response.
== Cause == Aside from L. odoratus, other members of the genus are also known to cause the disease, including L. sylvestris, L. cicera, and L. clymenum. L. odoratus grows well under famine conditions, often severe drought, where it is cultivated. These legumes carry a variety of osteolathyrogenic compounds, specifically excitatory amino-compounds. The most widely studied of these compounds is beta-aminopropionitrile (BAPN), which exerts its deleterious effect by an unknown yet potently irreversible mechanism. Other instigators are ureides, semicarbazides and thiosemicarbazides, which are believed to chelate the prosthetic Cu(II)-bipyridine cofactor complex in the enzyme lysyl oxidase. Lysyl oxidase is an important enzyme for the creation of crosslinks between collagen triple-helices in connective tissue. By oxidizing the terminal amino group of lysine, an aldehyde is created. This aldehyde can undergo several reactions with neighboring aldehydes or amines to create strong covalent cross-links between collagen tertiary structures in bone and cartilage. The main product of these reactions is the aldimine compound dehydrohydroxylysinonorleucine. This unique crosslink can be formed by the Schiff base mechanism in which the lone pair of electrons on a primary amine react with the carbonyl carbon of an aldehyde. Other crosslinks include the formation of an α,β-unsaturated ketone via aldol condensation and hydroxylysinonorleucine. If these crosslinks are not formed, as in the case of osteolathyrism, the synthesis of strong mesenchymal and mesodermal tissue is inhibited.
The condition has been described since ancient history. The Latinate term osteogenesis imperfecta was coined by Dutch anatomist Willem Vrolik in 1849; translated literally, it means "imperfect bone formation".
Isotope masses from: Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001 Isotopic compositions and standard atomic masses from: de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683. Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005. Half-life, spin, and isomer data selected from the following sources. Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001 National Nuclear Data Center. "NuDat 3.0 database". Brookhaven National Laboratory. Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.
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 mass difference from the linker is large enough for routine detection by mass spectrometry. The unconjugated form gives a single sharp signal at its expected weight. Material that has already reacted with albumin shows a much higher mass and a broadened chromatographic peak.