If you have been reading about DAC linker and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-08-26. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Receptor level activity follows the canonical GHRH pathway. The peptide binds the GHRH receptor, a class B G protein coupled receptor on somatotroph cells of the anterior pituitary. Binding raises intracellular cyclic AMP, which promotes calcium entry and the release of growth hormone into the bloodstream. Because the molecule acts at the same receptor as the endogenous hormone, its effect is superimposed on the natural pulsatile rhythm rather than replacing it. Whether sustained receptor occupation leads to desensitization is not fully settled.
Enzymatic protection is a separate mechanism from plasma protein binding. The four substitutions in the backbone reduce recognition by dipeptidyl peptidase IV, which normally cleaves the natural hormone within minutes. Without the reactive group, this resistance still yields only a short window of activity, generally reported in the range of tens of minutes. With it, reported half-lives in early human work extended to several days. The size of that gap is the main practical distinction between the two materials.
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.
| Property | Value | Notes |
|---|---|---|
| Peptide class | Synthetic GHRH analogue | Built on a 29 residue sequence |
| Primary target | GHRH receptor (GHRHR) | Class B G protein coupled receptor |
| Unconjugated half life | Minutes | Limited by protease degradation |
| Key modification | Four residue substitutions | Positions 2, 8, 15 and 27 |
| Common synonym | Modified GRF(1-29) | Usually denotes the form without DAC |
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.
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.
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.
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In an 18-month double-blind, placebo controlled study, the effects of Preotact on the fracture incidence in 2532 women with postmenopausal osteoporosis was studied. Approximately 19% of patients had a prevalent vertebral fracture at baseline and the mean lumbar T-score of -3.0 in both active and placebo arm. Compared to the placebo group, there was a 61% relative risk reduction of a new vertebral fracture at month 18 for the women in the Preotact group. To prevent one or more new vertebral fractures, 48 women had to be treated for a median of 18 months for the total population. For patients who were already fractured, the number needed to treat was 21.
==== Cirkunovs v. Zuffa and Davis v. Zuffa ==== In May 2025, two antitrust lawsuits were filed against the UFC. One, led by former fighter Misha Cirkunov, specifically challenges the enforceability of arbitration clauses and class action waivers in UFC contracts. The other lawsuit, filed by former fighter Phil Davis, alleges that the UFC's anticompetitive practices also negatively impacted the ability of non-UFC fighters to secure fair wages.
Sources: en.wikipedia.org
=== Organic synthesis === Acetonitrile is a common two-carbon building block in organic synthesis of many useful chemicals, including acetamidine hydrochloride, thiamine, and 1-naphthaleneacetic acid, along with more complex nitriles. Its reaction with cyanogen chloride affords malononitrile.
== Return to university == Boyd Orr realised that his heart was not in teaching, and after fulfilling his teaching obligations under the terms of his Queen's Scholarship, he returned to the university to study biology, a subject he had always been interested in since childhood. As a precaution, he entered simultaneously for a degree in medicine. He found the university to be a stimulating environment. Diarmid Noel Paton (son of the artist Joseph Noel Paton) was Regius Professor of Physiology, and Edward Provan Cathcart head of Physiological Chemistry, both men of outstanding scientific ability. He was impressed by Samson Gemmell, Professor of Clinical Medicine, a philosopher whose deep thinking on social affairs also influenced Boyd Orr's approach to such questions. Half-way through his medical studies, his savings ran out. Reluctant to ask his family for support, he bought a block of tenanted flats on mortgage, with the help of a bank overdraft, and used the rents to pay for the rest of his studies. On graduating, he sold the property for a small profit. He graduated with a BSc in 1910, and MB ChB in 1912, at the age of 32, placing sixth in a year of 200 students. Two years later, in 1914, he graduated MD with honours, receiving the Bellahouston Gold Medal for the most distinguished thesis of the year. .
During the George W. Bush administration, relations between India and the United States blossomed, primarily over common concerns regarding growing Islamic extremism, energy security, and climate change. George W. Bush commented, "India is a great example of democracy. It is very devout, has diverse religious heads, but everyone is comfortable about their religion. The world needs India". Journalist Fareed Zakaria, in his book The Post-American World, described Bush as "being the most pro-Indian president in American history." Similar sentiments are echoed by Rejaul Karim Laskar, a scholar of Indian foreign policy and ideologue of Indian National Congress – the largest constituent of the United Progressive Alliance (UPA). According to Laskar, the UPA rule has seen a "transformation in bilateral ties with the US", as a result of which the relations now covers "a wide range of issues, including high technology, space, education, agriculture, trade, clean energy, counter-terrorism, etc". After the December 2004 tsunami, the US and Indian navies cooperated in search and rescue operations and in the reconstruction of affected areas. Since 2004, Washington and New Delhi have been pursuing a "strategic partnership" that is based on shared values and generally convergent geopolitical interests. Numerous economic, security, and global initiatives, including plans for civilian nuclear cooperation, are underway. First launched in 2005, cooperation on nuclear weapons reversed three decades of American non-proliferation policy.
About 98.5% of the oxygen in a sample of arterial blood in a healthy human breathing air at sea-level pressure is chemically combined with the hemoglobin. About 1.5% is physically dissolved in the other blood liquids and not connected to hemoglobin. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species. Hemoglobin has an oxygen binding capacity between 1.36 and 1.40 ml O2 per gram hemoglobin, which increases the total blood oxygen capacity seventyfold, compared to if oxygen solely were carried by its solubility of 0.03 ml O2 per liter blood per mm Hg partial pressure of oxygen (about 100 mm Hg in arteries). With the exception of pulmonary and umbilical arteries and their corresponding veins, arteries carry oxygenated blood away from the heart and deliver it to the body via arterioles and capillaries, where the oxygen is consumed; afterwards, venules and veins carry deoxygenated blood back to the heart. Under normal conditions in adult humans at rest, hemoglobin in blood leaving the lungs is about 98–99% saturated with oxygen, achieving an oxygen delivery between 950 and 1150 ml/min to the body. In a healthy adult at rest, oxygen consumption is approximately 200–250 ml/min, and deoxygenated blood returning to the lungs is still roughly 75% (70 to 78%) saturated.
An anaerobic organism or anaerobe is an organism that does not require molecular oxygen for growth or energy metabolism. Anaerobes produce adenosine triphosphate (ATP) by fermentation, anaerobic respiration, or both. During anaerobic respiration, substances other than oxygen serve as the terminal electron acceptor. Anaerobes are commonly classified according to their relationship with oxygen. Obligate anaerobes are harmed by it. Aerotolerant organisms do not use oxygen but can tolerate it, whereas facultative anaerobes can grow without oxygen but use it when available. Most anaerobes are microorganisms, including bacteria, archaea, protozoa, and fungi, although a small number of anaerobic multicellular animals are known. Anaerobes occur in oxygen-depleted environments and in symbiotic associations with other organisms. Culturing anaerobes often requires oxygen-free techniques.
Sources: en.wikipedia.org
In March 2015, Spotlight entered into a purchase agreement with Memcine Pharmaceuticals, Inc., a Coralville, Iowa-based biotech company specializing in vaccine efficacy. Memcine Pharmaceuticals would officially become a Spotlight Innovation subsidiary in June 2015. In April 2015, Spotlight Innovation secured $2.5 million in financing from an unsecured convertible promissory note. In October 2016, Spotlight Innovation announced that it was discontinuing the Memcine Pharmaceuticals Immunoplex development program. In August 2016 Spotlight Innovation entered into a sponsored research agreement with Florida State University to support the work of Professor Hengli Tang in the development of treatments for Zika virus infection. In October 2016, Spotlight Innovation announced the formation of subsidiary Caretta Therapeutics, LLC. Caretta Therapeutics is based in Urbandale, Iowa. The subsidiary develops and markets over-the-counter (OTC) analgesic products formulated to provide relief from chronic pain associated with inflammation. In October 2016, Spotlight Innovation obtained an exclusive license from Indiana University Research and Technology Corp to commercialize an orally available small molecule named STL-182 with potential therapeutic potential for the treatment of spinal muscular atrophy. Early preclinical testing of STL-182 was accomplished by Dr. Elliot Androphy of Indiana University School of Medicine and Professor Kevin Hodgetts of Brigham and Women's Hospital.
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The following retirements from the House of Lords are announced by Lord McFall of Alcluith by virtue of non-attendance: John Prescott, Conrad Black and Jeffrey Archer. 11 July – The SNP confirms it will have to make the majority of its Westminster staff redundant after Parliament reduces its "Short Money" – the annual amount paid to opposition parties – by £1m. Peter Martin becomes the DUP MLA for North Down after the previous incumbent, Alex Easton was elected to Westminster. A week after his election to Parliament, GB News announces that Nigel Farage is returning to his show on the channel, presenting on Tuesdays, Wednesdays and Thursdays from 16 July. 12 July – Justice Secretary Shabana Mahmood confirms that thousands of prisoners in England and Wales will be released early from their sentences at the beginning of September, warning of the "total collapse" of the prison system and a "total breakdown of law and order" without steps being taken to ease prison overcrowding. 14 July – Leading UK political figures, including Sir Keir Starmer and Nigel Farage, condemn the previous day's attempted assassination of Donald Trump in the United States. Foreign Secretary David Lammy makes his first visit to Israel and the Palestinian territory to hold talks with leaders. Lord Walney, the UK government's adviser on political violence, writes to the Home Secretary urging an inquiry into potential intimidation of candidates at the general election by groups in different constituencies.
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Sources: en.wikipedia.org
The names are often used interchangeably in casual writing, but they are not strictly identical. Modified GRF(1-29) refers to the unconjugated analogue carrying only the four substitutions. The version sold as CJC-1295 with DAC includes the albumin binding linker and clears much more slowly.
DAC stands for drug affinity complex, a term describing the maleimidopropionic acid linker. This group forms a covalent bond with the cysteine residue on serum albumin after administration. The resulting adduct is what extends the circulating half life from minutes to days.
No. It is entirely synthetic and does not correspond to any known endogenous peptide. The design starts from human growth hormone releasing hormone and introduces deliberate substitutions. Any biological effect comes from mimicking the natural hormone at its receptor.
A maleimide moiety reacts with the thiol of cysteine-34, forming a covalent bond. The reaction occurs in circulation without enzymatic catalysis.