CJC-1295 Ipamorelin: DAC vs No-DAC Explained

The short version

When people write CJC-1295 Ipamorelin, the CJC-1295 half comes in two versions, and the difference is entirely about how long it lasts. The "DAC" version (DAC = Drug Affinity Complex) carries a small chemical hook that grabs onto albumin — a protein floating in your blood — and rides it for days, so growth hormone stays elevated for the better part of a week. The "no-DAC" version, usually called Mod GRF (1-29), has no hook; an enzyme chops it up in about half an hour. Same core peptide, wildly different timescale. That choice changes everything about how the stack behaves: a days-long steady push versus a brief sharp pulse. Below is the chemistry and the measured data — no dosing, just the difference.

What the DAC actually is

The Drug Affinity Complex is a piece of chemistry bolted onto the peptide's tail. CJC-1295 carries an N-epsilon-maleimidopropionamide-lysine group that covalently bonds to the Cys34 thiol (a sulfur atom) of serum albumin — essentially welding the peptide to a long-lived blood protein. In rats, this produced about a 4-fold increase in GH AUC (area under the curve, a total-exposure measure) over 2 hours versus unmodified GHRH(1-29), with albumin-bound peptide still detectable in plasma beyond 72 hours ^[5].

The payoff in humans: a single subcutaneous dose of CJC-1295 (DAC) raised mean plasma GH 2- to 10-fold for six or more days and IGF-1 1.5- to 3-fold for 9–11 days; after multiple doses IGF-1 stayed above baseline up to 28 days ^[1]. The DAC is the reason a GHRH analogue can act on a multi-day clock instead of a multi-minute one.

No-DAC: Mod GRF (1-29)

Strip the DAC off and you have mod grf 1-29 — the modified 29-amino-acid GHRH fragment with no albumin binding. Without the hook, it behaves like native GHRH: DPP-IV (a serum enzyme that cleaves GHRH at the N-terminus) clears it in minutes, giving a half-life on the order of ~30 minutes. CJC-1295's amino-acid substitutions were designed to resist DPP-IV, which extends it somewhat versus raw GHRH, but without the DAC it remains short and pulsatile.

That short pulse is, in one sense, the more physiological signal — native GH secretion is pulsatile, in 5–9 bursts a day. The no-DAC form mimics a single such pulse; the DAC form replaces pulses with a sustained background.

Why the distinction matters for the stack

Pairing CJC-1295 with ipamorelin is where the DAC choice gets consequential. Ipamorelin produces one short GH pulse and clears within hours ^[2]. Pair it with no-DAC Mod GRF (1-29) and you get two short, time-matched pulses — close to the GHRP+GHRH synergy the human literature actually studied ^[3]. Pair it with DAC CJC-1295 and you get a brief ipamorelin pulse riding on a multi-day GHRH background ^[1] — a different, less-characterized exposure profile.

The honest consequence: the intended pulsatile synergy and the net GH exposure are not characterized for any specific protocol, and chronic continuous GHRH drive from the DAC version is distinct from the short pulses the synergy work used ^[3]. The synergy evidence is strongest for the matched-pulse case; the multi-day-background case is extrapolation.

DAC vs no-DAC, at a glance

The contrast, from the cited record:

• CJC-1295 with DAC — molecular weight ~3647.3 Da; albumin-bound via Cys34; half-life ~6–8 days in humans; GH/IGF-1 elevated for days to weeks ^[1][5]. CAS 863288-34-0.
• CJC-1295 no-DAC (Mod GRF 1-29) — molecular weight ~3367.9 Da; no albumin binding; half-life ~30 minutes; short pulsatile action. CAS 446262-90-4.

Neither form is FDA-approved, and neither — nor the combination with ipamorelin — has been validated in a controlled human trial of the fixed blend. The DAC-vs-no-DAC choice is a pharmacokinetic fork, documented here, not a protocol recommendation.