CJC-1295 with DAC is the Modified GRF 1-29 backbone extended by a lysine at position 30 that carries a maleimidopropionyl group — the drug affinity complex — which reacts covalently with the free cysteine-34 thiol of circulating serum albumin and converts a peptide cleared in minutes into one that persists for days. The chemistry is the whole molecule. Everything that distinguishes CJC-1295 with DAC from the version without it follows from that one maleimide, and so does its research role: it is the tool used when the experimental question requires continuous GHRH receptor occupancy rather than a discrete pulse.
This page explains the conjugation chemistry, the receptor mechanism, what continuous exposure changes, and how the material is specified and handled. CJC-1295 with DAC is supplied for laboratory research use only.
CJC-1295 with DAC at a glance
| Property | Value |
|---|---|
| Backbone | Modified GRF 1-29 (tetrasubstituted GHRH 1–29 amide) |
| Extension | Lys30 bearing a maleimidopropionyl (drug affinity complex) group |
| Length | 30 residues plus the DAC linker |
| CAS number | 863288-34-0 |
| Molecular formula | C165H269N47O46 |
| Molecular weight | 3647.28 g/mol |
| Conjugation target | Cysteine-34 thiol of serum albumin |
| Bond formed | Covalent thioether (Michael addition) |
| Receptor | GHRH receptor (GHRHR), class B GPCR |
| Reported persistence | Days rather than minutes; multi-day half-life reported in animal and early human work |
| Sizes supplied | 2 mg, 5 mg, 10 mg lyophilized vials |
| Purity specification | ≥99% by RP-HPLC with lot-matched COA |
Origin and structure: how the drug affinity complex works
Serum albumin is the most abundant protein in plasma, it circulates for roughly three weeks, and it carries a single free cysteine thiol at position 34 — the only unpaired cysteine in the molecule. That combination makes it an unusually convenient anchor for extending the lifetime of a small peptide, and the drug affinity complex approach exploits it directly.
Maleimides react with thiols by Michael addition, forming a stable thioether bond, and they do so with high selectivity at near-neutral pH. Attaching a maleimidopropionyl group to the peptide therefore creates a molecule that will find and bind albumin's Cys34 after administration. The resulting conjugate is far too large for renal filtration and is shielded from most peptidase attack, so clearance follows albumin turnover rather than peptide turnover.
The structural details matter. The maleimide is carried on an added lysine at position 30, beyond the C-terminus of the 1–29 receptor-binding sequence, which places the reactive chemistry as far as possible from the residues that engage the receptor. The backbone itself is Modified GRF 1-29 — D-alanine at 2, glutamine at 8, alanine at 15, leucine at 27 — so the DAC version inherits all the chemical robustness of the substituted analogue and adds albumin binding on top. The mass difference tells the story: 3647.28 g/mol against 3367.93 g/mol for the version without DAC, a difference of about 279 Da corresponding to the added lysine and linker.
How it is thought to work
Receptor mechanism is unchanged from any other GHRH analogue: binding at the GHRH receptor on pituitary somatotrophs activates Gs, raises cyclic AMP and activates protein kinase A, increasing growth hormone gene transcription and release.
What changes is the shape of the exposure. Native GHRH and sermorelin produce a spike lasting minutes; Modified GRF 1-29 produces a somewhat longer pulse; the albumin-conjugated form produces a plateau lasting days, with multi-day half-life values reported in animal studies and early human pharmacokinetic work conducted during its development. This is a fundamentally different pharmacological experiment, and the literature is explicit about what it raises: sustained agonist occupancy at a class B GPCR invites receptor desensitisation and downregulation, and it removes the pulsatility that characterises normal somatotropic axis function.
For a researcher, that is the point. If the question is what continuous GHRH receptor engagement does to somatotroph signalling, to receptor expression or to downstream IGF-1, a long-acting agonist is the correct tool and a short-acting one is not. If the question concerns pulsatile physiology, the reverse holds. Selecting between the two versions is a study-design decision, not a preference, and the trade-off is set out in CJC-1295 vs CJC-1295 with DAC.
What research has examined
Pharmacokinetics and sustained receptor occupancy
The original development programme generated animal and early-phase human pharmacokinetic data demonstrating the multi-day persistence that the DAC conjugation was designed to produce, together with sustained elevation of growth hormone and IGF-1 markers. Development did not proceed to approval, and no CJC-1295 product holds marketing authorisation anywhere.
Receptor desensitisation and axis regulation
Continuous versus pulsatile agonist exposure is a general problem in class B GPCR pharmacology, and long-acting GHRH analogues are a natural tool for studying it. Endpoints include receptor expression, cyclic AMP responsiveness on re-challenge and downstream IGF-1 behaviour.
Comparative structure-activity work
The DAC and non-DAC versions differ in exactly one structural feature, which makes them a clean pair for isolating the effect of exposure duration from the effect of receptor pharmacology — an unusually well-controlled comparison in peptide research.
Combination designs
Pairing a GHRH receptor agonist with a growth hormone secretagogue receptor agonist such as ipamorelin is a common design, since the two receptors sit on the same cell and use different second messengers. Pre-blended research material exists as CJC-1295 DAC with ipamorelin. Combining a long-acting agonist with a short-acting one produces a more complicated exposure profile than either alone, which should be stated explicitly in any method.
Forms and sizes we supply
CJC-1295 with DAC is stocked as a lyophilized powder in 2 mg (USD 55), 5 mg (USD 100) and 10 mg (USD 180) sealed vials. At 3647.28 g/mol a 5 mg vial contains approximately 1.37 micromoles, slightly less than the 1.48 micromoles in a 5 mg vial of the non-DAC version — a difference worth accounting for in any molar-matched comparison between the two. The family sits under GHRH analogs.
Reconstitution and storage in a laboratory context
The calculation: a 5 mg vial reconstituted with 2 mL of bacteriostatic water gives 2.5 mg/mL, equivalently 2,500 mcg/mL; 0.1 mL (10 units on a U-100 syringe) contains 250 mcg. In molar terms the stock is approximately 686 micromolar.
One handling consideration is specific to this molecule and it is the important one: the maleimide is a reactive group, and it reacts with any accessible thiol, not only with albumin. Diluents and buffers containing reducing agents such as dithiothreitol or beta-mercaptoethanol will consume it, and free cysteine or thiol-containing additives in a culture medium will do the same. Maleimides also hydrolyse over time in aqueous solution, more rapidly at alkaline pH, which slowly destroys the conjugating capacity. The practical consequences are to reconstitute in a thiol-free, near-neutral diluent, to avoid prolonged storage in solution, and to keep aliquots frozen. Lyophilized vials go to −20 °C or colder, protected from light and moisture. General guidance is in the peptide storage guide.
Purity, COA and how to read one
Each lot is purified by reversed-phase HPLC to at least 99% with mass confirmation and a lot-matched certificate. The decisive check is mass. The observed mass should match 3647.28 g/mol; a mass near 3367.93 g/mol is the non-DAC peptide, and given the price difference between the two products this is a substitution worth verifying rather than assuming. A mass 18 Da above the expected value indicates hydrolysis of the maleimide ring to the unreactive maleamic acid, which means the material will no longer conjugate to albumin even though it will still bind the receptor — a degradation product that a purity percentage alone will not reveal. Beyond that, standard practice applies: read the chromatogram for a single symmetrical peak, confirm the lot number matches the vial, and check net peptide content against gross weight, as covered in our COA reading guide.
Regulatory status
No CJC-1295 product, with or without DAC, holds marketing authorisation as a medicine in the United States or elsewhere; the original development programme did not reach approval. It is not a dietary supplement ingredient and not a generally available compounded medication. Material supplied here is research use only, for in-vitro and preclinical laboratory investigation by qualified researchers, and is not intended for human or veterinary administration.
Related peptides and further reading
The non-DAC version is the direct structural counterpart and the appropriate comparator for any experiment isolating exposure duration. Sermorelin is the unmodified parent fragment and tesamorelin the acylated full-length analogue. On the secretagogue side, ipamorelin and the GHRPs act at the ghrelin receptor rather than the GHRH receptor, and the overall landscape is mapped in the GH secretagogue landscape explained.