FORM · PHARMACOKINETICS
CJC-1295 DAC vs No-DAC (Modified GRF 1-29): The Pharmacokinetic Difference
One name, two very different molecules. The DAC variant tethers serum albumin for a multi-day half-life; the no-DAC form is cleared in minutes to hours. Here is the difference the marketing flattens, drawn from the record.
What 'DAC' Changes
CJC-1295 DAC and the no-DAC form share an identical peptide backbone and differ by a single chemical handle — and that handle changes everything about how long a dose lasts. Both forms are the tetrasubstituted hGRF(1-29) sequence: D-Ala at position 2, Gln at 8, Ala at 15, Leu at 27, the substitutions that block DPP-IV cleavage and stabilize the helix. The DAC variant adds one thing the no-DAC form lacks: a covalent tether to circulating serum albumin.
That tether is the Drug Affinity Complex. A C-terminal lysine is functionalized with a maleimidopropionyl (MPA) linker that undergoes Michael addition with the free thiol on cysteine-34 of serum albumin, forming a covalent peptide-albumin conjugate [2]. Because the peptide now travels bound to albumin, its plasma half-life extends toward that of albumin itself — turning a peptide that would otherwise clear quickly into a multi-day depot. The no-DAC form keeps the four substitutions but carries no albumin-binding moiety, and so it stays short-acting.
CJC-1295 Half-Life: DAC vs No-DAC
The half-life gap between the two forms is the entire story, and it is large. Anyone searching CJC-1295 half life is really asking about two numbers, not one. The CJC-1295 DAC half-life was estimated at 5.8 to 8.1 days in healthy adults, with IGF-1 elevation persisting up to 28 days after multiple doses [1]. That is the property that lets a single DAC dose elevate growth hormone for six days or more [1].
What is CJC-1295 DAC?
CJC-1295 DAC is the long-acting form: the tetrasubstituted GHRH(1-29) sequence plus the albumin-binding DAC moiety. It is the molecule the early human pharmacokinetic studies characterized [1][3], and it is pharmacokinetically distinct from the short-acting no-DAC 'Modified GRF 1-29.'
What is CJC-1295 with DAC?
The Drug Affinity Complex variant adds a maleimide linker that covalently binds the peptide to circulating serum albumin at cysteine-34, extending the plasma half-life toward that of albumin itself and giving a multi-day duration [2]. The conjugation is what converts the peptide into a sustained depot rather than a short pulse.
Modified GRF (1-29): The No-DAC Form
Modified GRF (1-29) — the no-DAC form, also written modified GRF 1-29 or Mod GRF 1-29 — is the short-acting counterpart. It carries the same four protease-resistant substitutions as the DAC variant, which gives it more stability than native GHRH, but without the albumin tether it clears in the minutes-to-hours range, reflecting native GHRH(1-29) clearance with the substitutions slowing it modestly.
The practical consequence is that the two forms are not interchangeable, even though forums and product listings often treat them as the same thing. The DAC form is a multi-day depot; the no-DAC Modified GRF (1-29) is a brief pulse. Conflating them — assuming a 'CJC-1295' half-life of days when handling the no-DAC form, or vice versa — is the single most common error in the popular literature on this compound. This site keeps them on separate panes for exactly that reason.
Side by Side
The DAC and no-DAC forms diverge on the one axis that matters most — duration — and converge on nearly everything else. Both target the GHRH receptor, both were administered subcutaneously in the research, and both rest on the tetrasubstituted hGRF(1-29) backbone. Where they part is residence time: the DAC conjugate was detectable in plasma beyond 72 hours in rats [2] and carried a 5.8- to 8.1-day half-life in humans [1], while the no-DAC form is a short-acting peptide.
This is why a single estimate of 'CJC-1295 half-life' is meaningless without naming the form. The number 5.8 to 8.1 days belongs to the DAC variant alone [1]. The no-DAC Modified GRF (1-29) has no comparable multi-day figure because it was never engineered for one. For the dose figures the studies used, see the research doses; for the safety questions the long duration raises, see CJC-1295 side effects.
Where the DAC Program Went
The long-acting DAC program did not become an approved drug. The original developer, ConjuChem, ran a Phase 2 trial of CJC-1295 in HIV-associated visceral obesity (NCT00267527), which was discontinued; the DAC program did not advance [1]. Human evidence for the compound stops at the early Phase 1/pharmacokinetic studies in healthy volunteers — no large efficacy or long-term safety trial in healthy adults was ever completed.
How much CJC-1295 DAC should I take?
No validated human dose exists for the DAC form. Its multi-day half-life — estimated at 5.8 to 8.1 days [1] — is the reason community schedules are spaced out, but those schedules are not derived from controlled human efficacy trials. The published human work used single or multiple subcutaneous doses of 30, 60, or 90 µg/kg as pharmacokinetic probes [1][3], not as a recommended regimen.