TWO-CHANNEL READOUT / DAC + NO-DAC
CJC-1295 DAC vs no DAC (Modified GRF 1-29) in the research literature
Two molecules, one name, very different kinetics. The DAC variant persists for days; the no-DAC form is short-acting. This is the distinction the literature is most often conflated on.
Why CJC-1295 DAC vs no DAC is the central distinction
The CJC-1295 DAC vs no DAC distinction separates two molecules that share a backbone but behave nothing alike. Both are tetrasubstituted versions of hGRF(1-29) — the same four protease-resistant substitutions (D-Ala2, Gln8, Ala15, Leu27). The difference is a single chemical addition: the DAC variant carries an albumin-binding handle, and the no-DAC variant does not [1][11].
That one difference changes the duration of action from a multi-day window to a window of minutes to hours. Marketing and forum discussion routinely use "CJC-1295" to mean either form, which is why a half-life figure, a dose, or a safety claim is meaningless until the variant is specified. This page keeps the two on separate channels: DAC on one, no-DAC on the other.
The stakes of the confusion are not academic. A half-life that differs by two orders of magnitude means the same dose deposits a fundamentally different total exposure depending on the variant — and total exposure is what every downstream effect, from IGF-1 elevation to the anti-doping detection window, scales with. Reading the literature correctly starts with reading the variant correctly.
Half-life: DAC (5.8-8.1 days) vs no-DAC (short-acting)
The CJC-1295 half life is the clearest expression of the difference. For the DAC variant, the estimated half-life in healthy adults is 5.8 to 8.1 days, with measurable IGF-1 elevation persisting up to 28 days after multiple doses [1]. A single DAC dose elevated GH for 6 days or more and IGF-1 for 9 to 11 days [1].
The no-DAC form is short-acting. Lacking the albumin-binding moiety, Modified GRF (1-29) clears at roughly the rate of native GHRH(1-29) — a window measured in minutes to hours rather than days [1][11]. The same nominal dose therefore produces a brief pulse from the no-DAC form and a multi-day plateau from the DAC form. This is the single most important number on the site to attach to the correct channel.
The gap is not a matter of degree but of kind. A multi-day half-life and a minutes-to-hours half-life describe fundamentally different exposure profiles: the DAC variant holds the GHRH receptor under near-continuous stimulation across days, while the no-DAC form produces a transient signal that resolves the same day [1][11]. Notably, that sustained DAC stimulation did not flatten the body's own pulsatile GH rhythm in the human studies — pulsatility persisted despite the multi-day drive [3]. Any figure quoted for "CJC-1295" therefore has to be read against the variant it came from before it means anything at all.
What is CJC-1295 DAC, and what is the DAC chemistry
CJC-1295 "with DAC" carries a Drug Affinity Complex — a maleimidopropionyl (MPA) linker on a C-terminal lysine that undergoes Michael addition with the free thiol on Cys34 of circulating serum albumin, forming a covalent peptide-albumin conjugate [1][2]. Albumin has a long native residence in plasma, so bonding the peptide to it pulls the analog's half-life toward albumin's own — hence the multi-day window.
The rat work that identified CJC-1295 used exactly this chemistry: the hGRF(1-29)-albumin bioconjugate activated the GRF receptor in vivo and remained detectable in plasma beyond 72 hours, roughly quadrupling GH area-under-the-curve versus the unconjugated peptide [2]. The DAC chemistry is the entire reason the DAC variant is long-acting.
Modified GRF (1-29): the no-DAC form
Modified GRF (1-29) — written in shorthand as modified GRF 1-29 — is the no-DAC variant: the tetrasubstituted GHRH(1-29) sequence without the albumin-binding DAC moiety [11]. It keeps the four stabilizing substitutions (D-Ala2, Gln8, Ala15, Leu27) that block DPP-IV cleavage and stabilize the helix, but because it lacks the albumin tether, it is short-acting [1][11].
The name confusion is the core problem: "CJC-1295" is frequently used for this short-acting molecule even though, in the original ConjuChem terminology, CJC-1295 referred to the long-acting DAC conjugate. When a source says "CJC-1295" and means a peptide that clears in hours, it is describing Modified GRF (1-29) — the no-DAC form. Keeping the label attached to the right channel is the whole point of this distinction.
The practical consequence is that almost every cross-channel claim is wrong by default. A multi-day half-life belongs to the DAC variant, not to modified GRF 1-29; a microgram dose that makes sense as a brief pulse for the no-DAC form behaves very differently when attached to an albumin tether that holds it in circulation for days [1][11]. When you read a figure for "CJC-1295," the first question is always which of these two molecules produced it.