The shared core
Both forms start from the first 29 residues of human growth-hormone-releasing hormone, the fragment that carries full receptor activity. Four substitutions make it resist the enzymes that clear native GHRH within minutes: D-alanine at position 2 blocks DPP-4, glutamine at 8 and alanine at 15 remove chemically unstable residues, and leucine at 27 replaces an oxidation-prone methionine. This tetrasubstituted fragment is what most vendors sell as "modified GRF(1-29)" or "CJC-1295 without DAC". On its own it still has a half-life of minutes, because the kidney clears small peptides quickly regardless of enzyme resistance.
What the DAC adds
The Drug Affinity Complex is a lysine added to the C-terminus carrying a maleimidopropionic acid group. Maleimides react with free thiols, and the most abundant free thiol in blood is cysteine-34 of serum albumin. After administration the peptide bonds covalently to albumin and thereafter circulates with it, protected from filtration by the kidney. Albumin's own half-life is about three weeks; the conjugate's measured half-life in the Teichman study was 5.8 to 8.1 days. That mechanism, developed by ConjuChem in Montreal, is the whole reason the DAC form exists.
Side by side
| CJC-1295 with DAC | Modified GRF(1-29), "no DAC" | |
|---|---|---|
| Sequence | Tetrasubstituted GHRH(1-29) plus a C-terminal lysine bearing the maleimide linker | Tetrasubstituted GHRH(1-29) |
| Molecular weight | About 3,647 g/mol | About 3,368 g/mol |
| Half-life | 5.8–8.1 days (Teichman 2006) | Minutes |
| Growth hormone pattern | Elevated baseline with pulses preserved on top (Ionescu 2006) | A single pulse shortly after administration |
| Published human data | Two phase 1 and 2 studies in healthy adults, cited on the product page | Sparse; most of what circulates is extrapolated from GHRH(1-29) analogues such as sermorelin |
| Stability in solution | The maleimide hydrolyses slowly in water; reconstitute shortly before use | Standard peptide handling |
Why the name causes trouble
"CJC-1295" was ConjuChem's code for the DAC conjugate. The no-DAC fragment was never called that by its developers; the research-peptide market attached the name to it because the core sequence is the same. A study design built around once-weekly exposure needs the DAC form. A design built around a short pulse mimicking natural GHRH needs the fragment. Ordering one when the protocol assumes the other is the most common mistake with this compound, and the label on the vial is the only defence: a certificate for the DAC form will show a mass near 3,647, the fragment near 3,368.
What the certificate on our vial shows
Our CJC-1295 with DAC page carries a third-party certificate for the batch in stock, with the laboratory's verification key. The assay was run on the 5mg fill of the same batch as the 10mg vials, which the page states. We do not currently stock the no-DAC fragment.
Handling notes
- The maleimide group is the reactive part of the molecule and it does not last indefinitely in water. Reconstitute what will be used and do not store the DAC form in solution.
- Keep it away from thiol-containing reagents such as DTT or β-mercaptoethanol, which will consume the maleimide before it reaches anything else.
- Lyophilised powder is stable for years at −20°C. Storage by form is on the storage guide.