# CJC-1295 DAC vs no DAC (Modified GRF 1-29): The Half-Life Difference

> CJC-1295 DAC vs no DAC, disambiguated: the DAC variant's multi-day half-life via serum-albumin conjugation versus the short-acting no-DAC Modified GRF 1-29. The single most-conflated distinction, cited.

Same backbone, two clocks. The DAC variant lasts days; the no-DAC form lasts minutes-to-hours. This is the single distinction the literature most often blurs — kept apart here, variant by variant.

## The CJC-1295 DAC vs no DAC distinction in one frame

The **CJC-1295 DAC vs no DAC** question has one clean answer: it is a half-life difference, created by one piece of chemistry. Both forms share the same tetrasubstituted hGRF(1-29) backbone — the same four protease-resistant substitutions [7]. The DAC variant adds a covalent bond to serum albumin; the no-DAC form does not. That single addition is the difference between a multi-day half-life and a minutes-to-hours one [2][8].

The DAC variant ("Drug Affinity Complex") is the long-acting species: estimated half-life 5.8 to 8.1 days, with IGF-1 elevation persisting up to about 28 days after multiple doses [1]. The no-DAC form is sold as "Modified GRF 1-29" and is short-acting, clearing on the timescale of native GHRH(1-29) — minutes to hours [8][9]. Marketing and forums routinely treat them as interchangeable; pharmacokinetically they are not. Reading a no-DAC microgram "protocol" as if it applied to the DAC conjugate, or vice versa, is the most common factual error about this compound.

## What 'DAC' (Drug Affinity Complex) means

### What 'DAC' (Drug Affinity Complex) means

"DAC" stands for Drug Affinity Complex — the albumin-conjugation chemistry that makes CJC-1295 long-acting. In the DAC variant, a C-terminal lysine is functionalized with a maleimidopropionyl (MPA) linker that undergoes Michael addition with the free thiol on Cys34 of circulating serum albumin, forming a covalent peptide-albumin conjugate [2]. The effective circulating species is therefore not the small peptide but the much larger peptide-albumin complex.

The consequence is the multi-day half-life. In rats, the albumin conjugate gave roughly 4-fold higher GH area-under-the-curve over two hours than the unconjugated hGRF(1-29) and remained detectable in plasma beyond 72 hours [2]. That is the molecular basis for the entire long-acting profile — and the reason "CJC-1295 DAC" and "CJC-1295" are often used to mean the same multi-day molecule.

## Modified GRF (1-29): the short-acting no-DAC form

**Modified GRF 1-29** is the no-DAC form: the tetrasubstituted hGRF(1-29) sequence with the four protease-resistant substitutions but without the albumin-binding DAC moiety. It is short-acting. The substitutions — most importantly D-Ala at position 2 — protect against dipeptidylpeptidase-IV cleavage and increase half-life and potency relative to native GHRH(1-29), but only into the minutes-to-hours range, because there is no albumin handle to extend plasma residence [7][8].

This is why the no-DAC form is described as having a more "pulsatile," short-burst character in research discussion: it raises GH acutely and then clears, more closely mimicking a natural GHRH pulse than the DAC conjugate's days-long plateau. The pharmacology is the same receptor and the same downstream GH/IGF-1 axis; only the duration differs [3]. Calling Modified GRF 1-29 "CJC-1295" without the no-DAC qualifier is the conflation this whole page exists to prevent.

## The DAC-variant questions, answered

### What is CJC-1295 with DAC?

The version carrying a maleimidopropionyl-lysine handle that covalently bonds to a free thiol on circulating serum albumin, forming a peptide-albumin conjugate that extends the plasma half-life toward that of albumin — hence a multi-day duration of action [2].

### What is CJC-1295 DAC?

"DAC" = Drug Affinity Complex, the albumin-conjugation chemistry. In rats the conjugate gave roughly 4-fold higher GH AUC than unconjugated hGRF(1-29) and was detectable in plasma beyond 72 hours [2], the design that makes CJC-1295 long-acting.

### How much CJC-1295 DAC should I take?

The DAC variant's multi-day half-life (5.8-8.1 days) was studied at 30-90 micrograms/kg single subcutaneous doses [1]; murine work showed once-daily 2 micrograms normalized growth while less frequent dosing was progressively inferior [4]. Online fixed-microgram "protocols" are not derived from controlled human trials, and CJC-1295 has no approved human use.

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The CJC-1295 record read as a state machine — each figure logged to its study and tagged confirmed, the absent long-term human safety data left in plain view as the loudest state on the panel; no clinic behind the interface and nothing here dispensed or sold.