# CJC-1295 DAC vs No-DAC (Modified GRF 1-29) | Half-Life Explained

> CJC-1295 DAC vs No-DAC: the DAC variant binds albumin for a 5.8-8.1-day half-life; the no-DAC Modified GRF (1-29) form is short-acting. The single most-confused CJC-1295 distinction.

Two channels, two half-lives. The DAC variant bonds covalently to serum albumin for a multi-day half-life; the no-DAC Modified GRF (1-29) form keeps the four substitutions but clears in minutes to hours. The distinction the whole CJC-1295 literature confuses.

## What is CJC-1295 DAC?

CJC-1295 DAC vs no-DAC is the central confusion in this compound, so start with the DAC channel. CJC-1295 DAC is the variant whose C-terminal lysine is functionalized with a maleimidopropionyl (MPA) linker that undergoes a Michael addition with the free thiol on Cys34 of circulating serum albumin, forming a covalent peptide-albumin conjugate [2]. That covalent bond is the whole point: it drags the molecule's plasma residence toward that of albumin itself, extending the estimated half-life to 5.8 to 8.1 days in healthy adults [1].

The effective circulating species after conjugation is therefore not the small ~3,367.9-Da peptide but the far larger peptide-albumin complex, near 66 kDa [2]. CAS 863288-34-0 is the registry number consistently attributed to the DAC variant. This is the form that the human pharmacokinetic studies characterized, and the form responsible for a single dose moving GH and IGF-1 for over a week.

### What is CJC-1295 with DAC?

"With DAC" denotes the Drug Affinity Complex modification — a maleimide handle that bonds the peptide to circulating albumin, turning a short-acting GHRH analog into a multi-day one [2]. "DAC" and "with DAC" name the same albumin-conjugating chemistry; the term distinguishes this form from the no-DAC sequence that lacks it.

## No-DAC: Short-Acting Modified GRF (1-29)

The CJC-1295 no DAC form is a different pharmacokinetic animal. It keeps the four protease-resistant substitutions — D-Ala2, Gln8, Ala15, Leu27 — but lacks the albumin-binding DAC moiety, so it is short-acting, clearing in a minutes-to-hours window rather than days [11]. Without the covalent albumin bond, there is nothing to anchor it in circulation; the substitutions slow proteolytic clearance relative to native GHRH but do not extend it into the multi-day range.

This is the form most often sold and discussed as "Modified GRF 1-29," and conflating it with CJC-1295 DAC is the single most common error in the marketing and the forums. They share a backbone and four edits; they differ by one chemistry — the DAC handle — and that one difference is the entire half-life story.

### Modified GRF (1-29) and the No-DAC Distinction

Modified GRF (1-29) is the encyclopedic name for the tetrasubstituted GHRH(1-29) sequence without the DAC moiety [11]. Reference material describes it as a synthetic GHRH analog carrying the four stabilizing substitutions but lacking the albumin-binding chemistry, and therefore a much shorter duration of action than CJC-1295 DAC [9][11]. The D-Ala2 substitution is what extends GHRH(1-29) half-life and potency against dipeptidylpeptidase-IV in both forms [9]; only the DAC variant adds the albumin bond on top.

The conflation persists for a practical reason: the marketing shorthand collapsed two distinct molecules into one familiar name. "CJC-1295" became a catch-all label, so a buyer or reader encountering the term cannot tell from the name alone whether it refers to the multi-day DAC conjugate that the human pharmacokinetic studies actually characterized [1] or the short-acting no-DAC sequence that those studies did not. The peer-reviewed record keeps them separate; the casual record does not. Reading the literature correctly means treating "CJC-1295 DAC" and "Modified GRF (1-29)" as two entries, not two names for one thing — which is the distinction this entire page exists to hold.

## Half-Life: 5.8-8.1 Days (DAC) vs Minutes-to-Hours (No-DAC)

The half-life is the cleanest way to tell the two forms apart, and the numbers are not close. CJC-1295 DAC: an estimated 5.8 to 8.1 days in healthy adults, with IGF-1 elevation persisting up to 28 days after multiple doses [1]. No-DAC Modified GRF (1-29): short-acting, in the minutes-to-hours range, reflecting native GHRH(1-29) clearance modified only by the protease-resistant substitutions [11]. One form is dosed in the literature as a single injection that lasts a week; the other clears before the day is out.

That gap traces entirely to the albumin conjugation. In rats, the albumin-conjugated CJC-1295 produced a four-fold GH AUC over the unconjugated peptide and remained detectable in plasma beyond 72 hours — a direct readout of how much longer the covalent-albumin form persists [2]. The DAC bond converts a short-acting GHRH analog into a multi-day one; remove it and you are left with the short-acting sequence.

The duration difference cascades into how each form behaves in the body. The DAC variant's days-long residence is what let a single dose drive a dose-dependent 2- to 10-fold rise in mean GH for six days or more and a 1.5- to 3-fold rise in IGF-1 for nine to eleven days in healthy adults [1] — a sustained, low-level GHRH stimulus the pituitary answers continuously while still pulsing on its own schedule [3]. The short-acting no-DAC form produces a brief GHRH pulse instead: a sharp, transient signal that clears before it can hold the axis elevated for days. Same backbone, same four substitutions, same receptor — but the presence or absence of one covalent albumin bond is the difference between a multi-day pharmacology and a minutes-to-hours one.

When a source quotes a CJC-1295 half-life, the first question is always which form it means. A figure of "days" describes the DAC conjugate; a figure of "minutes to hours" describes no-DAC Mod GRF (1-29). Numbers quoted without that qualifier are the most common way the two forms get blurred together. For the doses attached to each form, see [doses used in research](/dosage), and for how CJC-1295 compares with shorter GHRH analogs like sermorelin, see [CJC-1295 vs sermorelin](/vs-sermorelin).

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An emerald-on-black console reading of the CJC-1295 record — the four substitutions, the DAC albumin handle, and the multi-day-versus-short-acting half-life each logged to its study and split by form, with no clinic behind the panel and nothing here dispensed or sold.