Two forms, one backbone
CJC-1295 DAC vs No-DAC (Modified GRF 1-29): Half-Life and Identity
The DAC variant is the multi-day, albumin-bonded form. The no-DAC form is short-acting. Same tetrasubstituted backbone, opposite pharmacokinetics — and the distinction marketing most often blurs.
What CJC-1295 DAC is
CJC-1295 DAC is the long-acting, albumin-conjugated form of the peptide. 'DAC' stands for Drug Affinity Complex: a C-terminal lysine on the tetrasubstituted hGRF(1-29) backbone is functionalized with a maleimidopropionyl linker that undergoes Michael addition with the free thiol on Cys34 of circulating serum albumin, forming a covalent peptide-albumin conjugate [2]. Because the effective circulating species is now bound to albumin, its plasma residence approaches that of albumin itself, and a single dose elevates GH and IGF-1 for days [1].
This is the form whose pharmacokinetics were characterized in healthy adults [1] [3] and whose once-daily dosing normalized growth in GHRH-knockout mice [4]. When the literature reports a multi-day half-life for CJC-1295, it is reporting on the DAC variant.
CJC-1295 half life: DAC (5.8-8.1 days) vs no-DAC (minutes to hours)
The CJC-1295 half life is the cleanest way to tell the two forms apart. In healthy adults the estimated half-life of the DAC variant was 5.8 to 8.1 days, and after multiple doses IGF-1 stayed above baseline up to 28 days [1]. In rats, the albumin conjugate was still detectable in plasma beyond 72 hours [2]. That multi-day residence is the entire point of the DAC chemistry.
The no-DAC form occupies the opposite end. Lacking the albumin-binding moiety, it clears in the minutes-to-hours range, reflecting the native GHRH(1-29) clearance that its protease-resistant substitutions slow but do not abolish. A 5.8-to-8.1-day half-life and a minutes-to-hours half-life are not two settings of one drug — they are two different pharmacokinetic species sold under one name.
CJC-1295 no DAC (Modified GRF 1-29): the short-acting form
The CJC-1295 no DAC form keeps the four substitutions that confer DPP-IV and protease resistance — D-Ala at position 2, Gln at 8, Ala at 15, Leu at 27 — but omits the albumin-binding DAC moiety entirely. The result is a short-acting GHRH analog: it still resists the proteases that destroy native GHRH within minutes, but without the albumin tether it clears far faster than the DAC form. Functionally it behaves as a stabilized GHRH(1-29) pulse rather than a multi-day stimulus.
The practical consequence is that no-DAC and DAC are studied and discussed as different tools. The no-DAC form's short action means its GH effect is brief and pulse-like; the DAC form's multi-day action is what the human PK studies measured [1] [3]. Conflating them — assigning DAC's multi-day duration to a no-DAC product, or vice versa — is the single most common error in CJC-1295 discussion.
Modified GRF 1-29 terminology
Modified GRF 1-29 is the name most consistently used for the no-DAC form. It signals exactly what the molecule is: a modified version of the first 29 amino acids of GH-releasing factor — the minimal sequence that retains full GH-releasing activity — carrying the four protease-resistant substitutions but not the albumin-binding handle. Synonyms in circulation include 'Mod GRF 1-29,' 'no-DAC,' and 'tetrasubstituted GRF(1-29).'
The terminology matters for due diligence because vendors and forums often use 'CJC-1295' alone to mean either form. When a source says only 'CJC-1295,' it has not actually told you which pharmacokinetic species it means. 'CJC-1295 DAC' and 'Modified GRF 1-29' are the unambiguous names — and registry identifiers can drift too: CAS 863288-34-0 is consistently attributed to the DAC variant, but some listings apply it loosely to the no-DAC sequence as well.
How much CJC-1295 DAC should I take?
There is no approved human dose; CJC-1295 is not approved for human use. DAC's 5.8-to-8.1-day half-life is why the GHRH-knockout-mouse study used once-daily dosing [4], and human pharmacokinetic studies used single subcutaneous doses of 30 to 90 µg/kg [1] [3]. Those are study doses described for the record, not a dosing recommendation.
What is CJC-1295 with DAC?
The variant whose C-terminal lysine carries a maleimidopropionyl linker that covalently bonds to serum albumin, extending the plasma half-life toward that of albumin itself [2]. The albumin conjugation is what produces the multi-day GH/IGF-1 elevation seen in human studies [1].
What is CJC-1295 DAC?
CJC-1295 with the Drug Affinity Complex moiety — the long-acting, albumin-conjugated form, as opposed to the short-acting no-DAC Modified GRF 1-29 [2]. It is the form whose 5.8-to-8.1-day half-life was estimated in healthy adults [1].