CJC-1295 with DAC: Albumin Conjugation and What It Changes

CJC-1295 with DAC is the tetra-substituted GHRH(1-29) peptide - D-Ala2, Gln8, Ala15, Leu27 - extended with a drug affinity complex. The DAC itself is a maleimidopropionic acid group, attached through an added lysine beyond the peptide's 29th residue. PubChem resolves the unbound molecule as CID 91971820, formula C165H269N47O46, molecular weight 3647.2 g/mol, CAS 446262-90-4.

Those numbers describe the peptide before it does the thing it was built to do. The maleimide is an electrophile with a strong preference for free thiols, and human serum albumin carries one accessible unpaired cysteine. On contact, the maleimide undergoes conjugate addition to that thiol and forms a stable covalent thioether bond. The circulating species is therefore not a 3.6 kDa peptide at all - it is albumin, roughly 66 kDa, with a GHRH analogue attached.

That is what converts the pharmacokinetics. Albumin has a serum half-life measured in weeks, is too large for glomerular filtration, and is recycled rather than cleared through the neonatal Fc receptor pathway. A peptide bound covalently to it inherits a large share of that persistence. This is the same general strategy used with fatty-acid conjugation in semaglutide and tirzepatide, but implemented as a permanent covalent bond rather than as reversible non-covalent binding.

Teichman and colleagues published the only substantial human trial in 2006. In healthy adults, CJC-1295 produced prolonged stimulation of growth hormone and IGF-1 secretion - precisely the pharmacodynamic profile the albumin conjugation was designed to produce. That study is the reason statements about this compound in humans are not purely inferential.

It is also where the record ends. There is no Phase 3 programme, no approved indication, and no long-term safety dataset. The contrast with tesamorelin on the same receptor is instructive: two completed Phase 3 trials, a pooled registrational analysis, a regulatory label with defined monitoring, and a published non-clinical toxicology package. CJC-1295 with DAC has one Phase 1/2-scale human study and a rodent pharmacology paper.

The absence matters more than usual here because of the mechanism. A covalent albumin adduct is, by construction, difficult to reverse. If exposure needs to be withdrawn, the peptide does not simply clear on a short timescale - the conjugate persists on the albumin pool. Long-acting pharmacology narrows the margin for adjustment, and the published literature does not characterise what that means over extended periods in humans.

This is the substantive pharmacological question, and it is the one most discussion of the DAC-versus-non-DAC choice gets wrong in both directions. The physiological argument against sustained exposure is genuine: growth hormone is secreted in discrete bursts under alternating GHRH drive and somatostatin restraint, and some downstream signalling appears sensitive to the pattern of exposure and not only to the integrated amount. A compound that occupies the GHRH receptor continuously for days looks, on its face, like it should abolish that architecture.

Ionescu and Frohman tested exactly this in 2006 and found it does not. Pulsatile growth hormone secretion persisted during continuous stimulation by CJC-1295. The reading that makes sense of this is that the GHRH receptor is a permissive input rather than the pacemaker - somatostatin withdrawal and pituitary dynamics generate the pulses, and a constant GHRH signal raises their amplitude without erasing their rhythm. Anyone arguing that the non-DAC form is physiologically superior needs to engage with this result, because it undercuts the core of that argument.

The desensitisation question is separately contested. Vance and colleagues reported somatotroph desensitisation alongside an increase in releasable growth hormone during continuous GHRH infusion in 1986, then found no desensitisation or depletion after fourteen days of continuous administration in 1989. Both papers are theirs; both are in the same journal; they point in different directions. Meanwhile Laursen and colleagues compared continuous with intermittent growth hormone delivery across the IGF system, insulin sensitivity, body composition, bone and lipoprotein metabolism - which is the pattern question posed directly, and posed because it was not obvious. The honest summary is that sustained GHRH-receptor exposure is neither clearly better nor clearly worse than pulsatile exposure, and that the field has been arguing about it since the 1980s.

The code CJC-1295 was assigned by ConjuChem and used by Jetté and colleagues to designate a specific albumin bioconjugate. The 2005 title states it directly: among hGRF(1-29)-albumin bioconjugates, CJC-1295 is identified as the long-lasting GRF analog. The conjugation is definitional, not an added feature.

The unconjugated tetra-substituted peptide was the scaffold. It acquired the retronym 'CJC-1295 without DAC' only after it began circulating separately, and that phrase has caused a durable confusion: the published human and rodent data indexed under CJC-1295 describe the conjugate, while a large volume of online discussion applies those findings to the unconjugated peptide, whose circulating persistence differs by three orders of magnitude.

For practical purposes: if a claim about CJC-1295 cites Jetté, Teichman, or Ionescu and Frohman, it is a claim about the DAC-bearing molecule. Noreo's companion monograph on Modified GRF (1-29) covers the unconjugated peptide on its own terms, including the 1994 human pharmacokinetic work on the D-Ala2 substitution that is the closest directly applicable evidence for it.