CJC-1295 With DAC vs Without DAC: What Is the Difference?

CJC-1295 with DAC and CJC-1295 without DAC are two different molecules that share a name. Both are synthetic analogs of the first 29 amino acids of growth hormone-releasing hormone (GHRH). The version with DAC carries an additional lysine linked to a maleimidopropionyl group that binds covalently to serum albumin, and published pharmacology reports an elimination half-life of roughly six to eight days for it [1]. The version without DAC has no albumin-binding group and a far shorter circulating half-life.

What do both versions have in common?

Both start from GRF (1-29) amide, the 29-residue fragment of GHRH that is also known as sermorelin: YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH2. CJC-1295 replaces four of those residues. D-alanine at position 2 resists cleavage by dipeptidyl peptidase-4 between positions 2 and 3. Glutamine at position 8 replaces an asparagine that is prone to deamidation. Alanine at position 15 replaces glycine. Leucine at position 27 replaces a methionine that oxidizes readily. The resulting 29-residue sequence is called tetrasubstituted GRF (1-29), and it is the entire molecule sold as "CJC-1295 without DAC".

What does DAC add?

DAC stands for Drug Affinity Complex. In CJC-1295 with DAC, a lysine is added after position 29 and its side chain carries 3-maleimidopropionic acid. The maleimide reacts with the free thiol of cysteine 34 on albumin, so the peptide circulates attached to a protein with a long lifetime of its own. In the published clinical pharmacology study of the DAC form, growth hormone and IGF-1 concentrations stayed elevated for days after a single exposure [1], and a follow-up study reported that pulsatile growth hormone secretion persisted during that period [2].

Why are the names confused?

The name CJC-1295 was originally given to the albumin-binding conjugate. Supplier catalogs later applied it to the unconjugated tetrasubstituted peptide as well, adding "no DAC" or "without DAC" to separate the two. CAS numbers are applied inconsistently for the same reason: PubChem lists 446262-90-4 for the DAC form [3], while 863288-34-0 appears in catalogs for both forms. A CAS number alone is therefore not enough to establish which molecule a label refers to.

How can the two be told apart on a lab report?

Mass spectrometry separates them clearly. The average molecular weight of the DAC form is about 3647.2 Da and that of the form without DAC is about 3367.9 Da, a difference of roughly 279 Da. A report that states the observed mass, not only the word "conforms", shows which molecule was in the vial. Sermorelin itself, the unmodified fragment, sits at about 3357.9 Da, close to but distinguishable from the tetrasubstituted version.

Frequently asked questions

Is CJC-1295 without DAC the same as sermorelin?

No. Sermorelin is unmodified GRF (1-29) amide. CJC-1295 without DAC carries four substitutions at positions 2, 8, 15 and 27, which change its stability and its molecular weight by about 10 Da.

Is Mod GRF 1-29 the same as CJC-1295 without DAC?

Yes. Modified GRF (1-29), Mod GRF 1-29 and tetrasubstituted GRF (1-29) are names for the same 29-residue peptide.

How does FLASK list the two?

FLASK lists them as separate materials: CJC-1295 (no DAC) and CJC-1295 (with DAC), each with its own formula, molecular weight and CAS number on the product page.