CJC-1295 with DAC vs without DAC

The same core peptide with half-lives differing by orders of magnitude. What the drug affinity complex changes, and why the choice decides what a study can measure.

One peptide, two kinetic profiles

Both forms are CJC-1295: a 29-residue GHRH analogue with four substitutions that resist DPP-4 cleavage. The difference is a single added group.

CJC-1295 with DAC carries a drug affinity complex, a maleimidopropionic acid moiety that forms a covalent bond with cysteine-34 on serum albumin. Albumin circulates with a half-life of around twenty days, so the bound peptide persists far beyond what the sequence alone would allow. CJC-1295 without DAC, commonly called modified GRF(1-29), has no such anchor and a half-life on the order of half an hour.

This is a pharmacokinetic difference, not a potency one. Both act at the same receptor with similar affinity.

Where they differ

Half-life. Roughly thirty minutes without DAC; several days with it.
Release profile. A discrete pulse that rises and decays, against a sustained elevation of the baseline.
Pulsatility. The non-DAC form preserves the natural pulsatile pattern of growth hormone secretion. The DAC form flattens it.
Combination work. Pairing a GHRH analogue with a ghrelin agonist such as Ipamorelin to produce coincident peaks requires the short-acting form; with the DAC form there is no peak to align to.
Study duration. The DAC form suits long-observation designs with infrequent intervention. The non-DAC form suits time-course work where the shape of the response is the measurement.
Receptor behaviour. Continuous agonism at a receptor normally exposed to pulses is itself a variable, and desensitisation is a consideration with the DAC form that does not arise with the other.

Which suits which question

If the endpoint is the shape of the growth hormone response — amplitude, timing, interaction with an endogenous pulse — the non-DAC form is the only one that can answer it. If the endpoint is a downstream consequence of chronically elevated GH or IGF-1 measured over days or weeks, the DAC form removes a large source of variability from the design.

The combined CJC-1295 / Ipamorelin preparation uses the short-acting form for exactly this reason. A sustained GHRH signal paired with a pulsatile secretagogue would defeat the purpose of the pairing.

How both are supplied

Both forms are lyophilised in sealed vials and each batch is specified at 99% purity or better by HPLC with identity confirmed by mass spectrometry, released against a batch-matched Certificate of Analysis by the process on the lab testing page. Identity confirmation is doing real work here: the two forms are close in mass, and a laboratory sent the wrong one will observe a plausible result that answers a different question. Both sit in the growth and recovery group.

Research use only

Both forms are laboratory reference materials. Neither is a medicine, a supplement, or for human or veterinary use, and no dosing guidance or administration protocol is provided for either. The full terms are in the research use policy. Every guide is indexed in the research library.