SECTION 05 / VARIANT SPLIT · DAC | NO-DAC
CJC-1295 DAC vs no DAC (Modified GRF 1-29): the half-life distinction
One sequence, two pharmacokinetic species. The albumin-conjugated DAC form lasts days; the no-DAC form lasts minutes to hours. They are not interchangeable.
The distinction in one paragraph
CJC-1295 DAC vs no DAC is the single most-confused point about this peptide, and the difference is pharmacokinetic, not cosmetic. Both forms carry the four protease-resistant substitutions on hGRF(1-29). The DAC variant adds one thing the no-DAC form lacks: a maleimide linker that covalently binds the peptide to circulating serum albumin, extending the plasma half-life toward 5.8 to 8.1 days [1][2]. The no-DAC form — Modified GRF (1-29) — has no albumin handle and clears in the minutes-to-hours range.
Marketing and forums routinely conflate the two. They should not be. A multi-day half-life and a minutes-to-hours half-life imply completely different kinetics, and treating one form's data as the other's is the most common error in the popular literature.
The two pages of this site that carry quantitative figures keep the label attached for exactly this reason. When you read "5.8 to 8.1 days" or "up to 28 days," the form is the DAC variant [1]; when you read "short-acting" or "minutes to hours," it is the no-DAC Modified GRF (1-29). The sections below take each form in turn, so the chemistry that creates the difference — the albumin conjugation — is never assumed and never skipped.
What is CJC-1295 DAC?
DAC stands for "Drug Affinity Complex" — a maleimidopropionyl linker on a C-terminal lysine that undergoes Michael addition with the free thiol on Cys34 of serum albumin, forming a covalent peptide-albumin conjugate [2]. The effective circulating species after conjugation is the much larger peptide-albumin complex, near 66 kilodaltons.
The DAC chemistry was identified in the discovery work that screened hGRF(1-29)-albumin bioconjugates and named CJC-1295 as the lead long-lasting GHRH analog [2]. In that work the conjugated lead produced a four-fold increase in GH area-under-the-curve over two hours versus the unconjugated peptide in rats, with peptide detectable in plasma beyond 72 hours [2].
What is CJC-1295 with DAC?
DAC ("Drug Affinity Complex") is a maleimide linker that covalently binds the peptide to circulating serum albumin, extending the plasma half-life toward 5.8-8.1 days [1][2]. "CJC-1295 with DAC" is the long-acting, albumin-conjugated form.
What is CJC-1295 DAC?
The albumin-conjugated, long-acting variant of CJC-1295. The DAC chemistry was identified in the discovery work that screened hGRF(1-29)-albumin bioconjugates and named CJC-1295 as the lead long-lasting GHRH analog [2].
Modified GRF (1-29): the no-DAC form
Modified GRF (1-29), also called Mod GRF 1-29 or no-DAC CJC-1295, is the tetrasubstituted GHRH(1-29) sequence without the albumin-binding DAC moiety. It keeps the DPP-IV resistance the substitutions provide but is short-acting — its clearance reflects that of native GHRH(1-29), in the minutes-to-hours range rather than days [1].
The practical consequence is that no-DAC kinetics resemble a brief, repeatable GH pulse, while the DAC variant sustains stimulation across days. Any figure quoted for "CJC-1295" should specify which form it describes; the half-life alone (days versus minutes) tells you which one is meant.
Half-life: 5.8 to 8.1 days for the DAC variant
The DAC variant's estimated half-life is 5.8 to 8.1 days in healthy adults, established in the controlled human pharmacokinetic work; after multiple doses, IGF-1 elevation persisted up to 28 days [1]. That multi-day residence is the defining property of the DAC form and the reason a single dose elevates GH and IGF-1 for days while preserving pulsatility [3].
The no-DAC Modified GRF (1-29) does not share this. Its short-acting kinetics are why fixed-interval comparisons between the two forms mislead, and why this site reports the 5.8-8.1-day figure only for the DAC species.
How much CJC-1295 DAC should I take?
Controlled human pharmacokinetic work used 30-90 microgram-per-kilogram single subcutaneous doses of the DAC variant, with IGF-1 elevation persisting up to 28 days after multiple doses [1]. No validated human dosing regimen exists; the multi-day half-life distinguishes DAC handling from the short-acting no-DAC form.
Why the conflation matters, and how to tell the forms apart
The DAC-versus-no-DAC confusion is not a pedantic distinction; it changes what any quoted figure means. A half-life of days and a half-life of minutes-to-hours describe different molecules behaving differently, and a claim attached to "CJC-1295" without a form label is ambiguous at best. When the popular literature applies the DAC variant's 5.8-8.1-day kinetics [1] to a no-DAC peptide, or treats a short-acting protocol as if it carried multi-day exposure, the error is structural — it mixes the data of two species.
There is a simple test for which form a source means. If the figure is a multi-day half-life, a once-weekly framing, or IGF-1 elevation measured over weeks, it describes the albumin-conjugated DAC variant [1]. If it is a minutes-to-hours half-life or a several-times-daily framing, it describes the no-DAC Modified GRF (1-29). The albumin handle is the dividing line: present, and the peptide rides serum albumin for days [2]; absent, and it clears on the timescale of native GHRH(1-29).
This site keeps the two apart everywhere they appear. The 5.8-8.1-day half-life, the up-to-28-day IGF-1 persistence, and the four-fold GH area-under-the-curve from the discovery work are all DAC-variant findings [1][2]. The no-DAC form is reported only as short-acting, because that is what the literature supports for it. Holding that line is the single most useful thing a reader can take from this page.