Sermorelin vs CJC-1295 (No DAC): GRF 1-29 and Its Modified Analog

Sermorelin and CJC-1295 without DAC are both 29-residue fragments of growth hormone-releasing hormone, and they differ at exactly four positions. Sermorelin is the unmodified fragment, GRF (1-29) amide, with a molecular weight of about 3357.9 Da [2]. CJC-1295 without DAC, also called modified GRF (1-29), replaces residues 2, 8, 15 and 27 to make the peptide more resistant to degradation, and weighs about 3367.9 Da.

What does each substitution do?

Position 2: alanine becomes D-alanine, which blocks cleavage by dipeptidyl peptidase-4, the enzyme that rapidly inactivates the natural fragment by removing its first two residues. Position 8: asparagine becomes glutamine, removing a site prone to deamidation. Position 15: glycine becomes alanine, which favors the helical shape of the peptide. Position 27: methionine becomes leucine, removing a residue that oxidizes easily. The four changes address enzymatic, chemical and conformational weaknesses of the native sequence.

How do they differ in the literature?

Sermorelin was developed and marketed in the United States as a prescription product and was later discontinued by its manufacturer. Its literature includes clinical diagnostic and pharmacology work from that period. The modified analog was developed later; its best-known clinical pharmacology studies concern the albumin-binding DAC form rather than the unconjugated peptide [1].

How are they told apart in the laboratory?

The masses differ by about 10 Da, which high-resolution mass spectrometry resolves, although both peptides carry many charges in electrospray spectra and the comparison should be made on the deconvoluted parent mass. Their HPLC retention times also differ because leucine is more hydrophobic than methionine and the other substitutions change the overall profile. Sermorelin's methionine at position 27 means oxidized forms, 16 Da heavier, are a common impurity to look for; the modified analog has no methionine.

Frequently asked questions

Is sermorelin the same as GHRH?

No. Native growth hormone-releasing hormone has 44 residues. Sermorelin is its first 29 residues with a C-terminal amide, the shortest fragment reported to retain full activity in early studies.

Is CJC-1295 without DAC the same as CJC-1295 with DAC?

No. The DAC form adds a lysine with an albumin-binding group and weighs about 3647.2 Da.

Does FLASK list both?

Yes: Sermorelin 5 mg and CJC-1295 (no DAC) 5 mg, plus CJC-1295 (with DAC) 10 mg.