VARIANT CHANNEL / DAC · NO-DAC
CJC-1295 DAC vs no DAC (Modified GRF 1-29): the half-life difference
Same backbone, two clocks. The DAC variant lasts days; the no-DAC form lasts minutes-to-hours. This is the single distinction the literature most often blurs — kept apart here, variant by variant.
The CJC-1295 DAC vs no DAC distinction in one frame
The CJC-1295 DAC vs no DAC question has one clean answer: it is a half-life difference, created by one piece of chemistry. Both forms share the same tetrasubstituted hGRF(1-29) backbone — the same four protease-resistant substitutions [7]. The DAC variant adds a covalent bond to serum albumin; the no-DAC form does not. That single addition is the difference between a multi-day half-life and a minutes-to-hours one [2][8].
The DAC variant ("Drug Affinity Complex") is the long-acting species: estimated half-life 5.8 to 8.1 days, with IGF-1 elevation persisting up to about 28 days after multiple doses [1]. The no-DAC form is sold as "Modified GRF 1-29" and is short-acting, clearing on the timescale of native GHRH(1-29) — minutes to hours [8][9]. Marketing and forums routinely treat them as interchangeable; pharmacokinetically they are not. Reading a no-DAC microgram "protocol" as if it applied to the DAC conjugate, or vice versa, is the most common factual error about this compound.
What 'DAC' (Drug Affinity Complex) means
What 'DAC' (Drug Affinity Complex) means
"DAC" stands for Drug Affinity Complex — the albumin-conjugation chemistry that makes CJC-1295 long-acting. In the DAC variant, a C-terminal lysine is functionalized with a maleimidopropionyl (MPA) linker that undergoes Michael addition with the free thiol on Cys34 of circulating serum albumin, forming a covalent peptide-albumin conjugate [2]. The effective circulating species is therefore not the small peptide but the much larger peptide-albumin complex.
The consequence is the multi-day half-life. In rats, the albumin conjugate gave roughly 4-fold higher GH area-under-the-curve over two hours than the unconjugated hGRF(1-29) and remained detectable in plasma beyond 72 hours [2]. That is the molecular basis for the entire long-acting profile — and the reason "CJC-1295 DAC" and "CJC-1295" are often used to mean the same multi-day molecule.
Modified GRF (1-29): the short-acting no-DAC form
Modified GRF 1-29 is the no-DAC form: the tetrasubstituted hGRF(1-29) sequence with the four protease-resistant substitutions but without the albumin-binding DAC moiety. It is short-acting. The substitutions — most importantly D-Ala at position 2 — protect against dipeptidylpeptidase-IV cleavage and increase half-life and potency relative to native GHRH(1-29), but only into the minutes-to-hours range, because there is no albumin handle to extend plasma residence [7][8].
This is why the no-DAC form is described as having a more "pulsatile," short-burst character in research discussion: it raises GH acutely and then clears, more closely mimicking a natural GHRH pulse than the DAC conjugate's days-long plateau. The pharmacology is the same receptor and the same downstream GH/IGF-1 axis; only the duration differs [3]. Calling Modified GRF 1-29 "CJC-1295" without the no-DAC qualifier is the conflation this whole page exists to prevent.
The DAC-variant questions, answered
What is CJC-1295 with DAC?
The version carrying a maleimidopropionyl-lysine handle that covalently bonds to a free thiol on circulating serum albumin, forming a peptide-albumin conjugate that extends the plasma half-life toward that of albumin — hence a multi-day duration of action [2].
What is CJC-1295 DAC?
"DAC" = Drug Affinity Complex, the albumin-conjugation chemistry. In rats the conjugate gave roughly 4-fold higher GH AUC than unconjugated hGRF(1-29) and was detectable in plasma beyond 72 hours [2], the design that makes CJC-1295 long-acting.
How much CJC-1295 DAC should I take?
The DAC variant's multi-day half-life (5.8-8.1 days) was studied at 30-90 micrograms/kg single subcutaneous doses [1]; murine work showed once-daily 2 micrograms normalized growth while less frequent dosing was progressively inferior [4]. Online fixed-microgram "protocols" are not derived from controlled human trials, and CJC-1295 has no approved human use.