CJC-1295 With DAC vs Without DAC: What Changes in the Molecule

The shared starting point: GHRH(1–29)

Growth hormone-releasing hormone (GHRH) has 44 residues, but its first 29 carry the receptor activity. That 1–29 fragment, amidated at the C-terminus, is Sermorelin. Its weakness as a research tool is a short half-life, because enzymes such as dipeptidyl peptidase-4 cleave it quickly.

Without DAC: modified GRF (1–29)

CJC-1295 without DAC, also called modified GRF (1–29), keeps the 29-residue length but swaps four amino acids (at positions 2, 8, 15 and 27) to resist enzymatic cleavage. It remains a linear peptide with no added groups.

With DAC: an added albumin-binding group

CJC-1295 with DAC adds a "drug affinity complex": a lysine at the C-terminus carrying a maleimidopropionic acid group. In biological samples that group reacts with a cysteine on serum albumin, tethering the peptide to a large, long-lived protein. Published pharmacokinetic studies report a half-life measured in days rather than minutes.

Practically, the two forms have different molecular weights and different mass-spectrometry signatures, so it matters which one a label describes.

Side by side

• Sermorelin: native GHRH(1–29) amide, shortest half-life.
• CJC-1295 without DAC: four substitutions, no added group.
• CJC-1295 with DAC: four substitutions plus a C-terminal lysine-maleimide linker that binds albumin.
• Tesamorelin: full 44-residue GHRH with an N-terminal trans-3-hexenoyl group; see the Tesamorelin overview.

Where Ipamorelin fits

Ipamorelin is not a GHRH analog. It acts at a different receptor (GHS-R1a, the ghrelin receptor), which is why it is often paired with a GHRH analog in research designs and in the CJC-1295 / Ipamorelin blend.