Two vials on the shelf carry almost the same name. One reads CJC-1295 DAC, the other CJC-1295 No-DAC. They share a peptide backbone, target the same receptor, and belong to the same drug family. Yet in the research literature they behave like different tools entirely — one produces a slow, days-long elevation, the other a brief pulse measured in minutes. The gap between them comes down to a single chemical addition. Understanding that addition is the fastest way to understand why the growth-hormone secretagogue shelf is organized the way it is.
The Shared Starting Point: A GHRH Analog
Both compounds descend from growth-hormone-releasing hormone (GHRH), the hypothalamic peptide that tells the pituitary to release growth hormone. The active signaling region of GHRH lives in its first 29 amino acids, a fragment known as GRF(1-29) — the same sequence marketed as Sermorelin.
Native GRF(1-29) is fragile. The enzyme dipeptidyl peptidase-4 (DPP-4) clips it near the N-terminus within a couple of minutes, so its window of action is extremely short. To make a more stable research analog, chemists introduced four amino acid substitutions into the GRF(1-29) sequence. These swaps — at positions vulnerable to enzymatic attack and oxidation — produce a molecule commonly called modified GRF(1-29), or "Mod GRF 1-29."
This is the crucial fact that confuses newcomers: modified GRF(1-29) and "CJC-1295 without DAC" are the same molecule. The No-DAC product is the tetrasubstituted GRF(1-29) analog. Everything that follows builds on top of it.
The Fork in the Road: The Drug Affinity Complex
The letters DAC stand for Drug Affinity Complex. It is not part of the peptide's signaling machinery — it is a bolt-on. To the modified GRF(1-29) backbone, chemists attach a small maleimidopropionic acid linker through a lysine residue. That linker is designed to do one job: react with albumin, the most abundant protein in blood plasma.
Once injected into a research model, the DAC-bearing peptide forms a covalent bond with circulating albumin, hitching itself to a large carrier protein that the body does not rapidly clear. The result is a peptide that dodges kidney filtration and enzymatic breakdown by hiding on a much bigger molecule.
No-DAC simply lacks this linker. It carries the four stabilizing substitutions but nothing to grab albumin. So it circulates freely, does its work, and is cleared on the ordinary timescale of a small peptide.
That single structural difference — a linker present or absent — is the entire comparison.
Half-Life: Minutes vs Days
The pharmacokinetic split is dramatic.
CJC-1295 No-DAC (modified GRF 1-29) has a half-life on the order of ~30 minutes. It reaches the receptor, drives a short burst of activity, and fades. In research protocols it is typically studied alongside a ghrelin-mimetic secretagogue such as Ipamorelin, and its brief window is central to how it is characterized.
CJC-1295 DAC, tethered to albumin, has a half-life reported in the range of ~6 to 8 days. A single exposure produces a sustained elevation of GH-releasing signal that persists for the better part of a week. This property earned the DAC version its original description in the literature as a "long-acting GHRH analog" — the design goal was infrequent administration with a durable effect.
The numbers are not a minor detail. A half-life difference of two orders of magnitude changes the entire pharmacological personality of the molecule.
Pulsatility: The Deeper Distinction
Half-life is the headline, but the more scientifically interesting difference is what each compound does to the pattern of GH release.
In healthy physiology, growth hormone is secreted in pulses — sharp bursts, especially during deep sleep, separated by troughs where levels fall low. This pulsatile rhythm is not incidental; downstream signaling and the somatostatin "brake" that shapes it are tuned to the peaks-and-valleys pattern. (We covered this architecture in the GH secretagogue axis explainer.)
No-DAC's short half-life means it layers onto the natural rhythm. A brief GHRH signal nudges a pulse and then clears, leaving the trough intact. Research interest in No-DAC often centers on preserving that pulsatile character.
DAC's week-long presence does the opposite. By keeping a GHRH-like signal elevated continuously, it tends toward a sustained, less pulsatile "bleed" of releasing activity. This is a recurring discussion point in the preclinical literature: whether a continuous elevation of the GHRH signal is physiologically equivalent to amplifying the body's own pulses, or whether it represents a fundamentally different stimulus. The somatostatin feedback system and IGF-1 negative feedback still operate, but the input pattern they are responding to has changed.
There is no settled verdict here — it is precisely the kind of open mechanistic question that makes the DAC/No-DAC pair interesting as research tools rather than interchangeable products.
Identity, Naming, and COA Confusion
Because the No-DAC compound has multiple names, the paperwork can mislead. A certificate of analysis might list the same molecule as "CJC-1295 No-DAC," "Mod GRF 1-29," or "modified GRF(1-29)." All three describe the tetrasubstituted GRF(1-29) analog without the albumin linker.
Meanwhile, some sources loosely use "CJC-1295" to mean the DAC version specifically, since that was the compound the CJC-1295 designation originally described in the peer-reviewed pharmacology. When comparing two vials, the presence or absence of the DAC linker — reflected in the reported molecular mass — is the only unambiguous way to tell them apart.
This is a case where reading the COA matters. The two molecules have different masses because the DAC linker adds measurable weight. Mass-spectrometry identity confirmation, not the label alone, distinguishes them. For more on how identity versus purity are established, see our quality standards overview.
Side-by-Side Summary
- Backbone: Both are modified GRF(1-29), a stabilized 29-amino-acid GHRH fragment with four substitutions.
- The difference: DAC adds a maleimidopropionic acid linker that binds albumin. No-DAC has no linker.
- Half-life: No-DAC ~30 minutes; DAC ~6–8 days.
- Release pattern: No-DAC layers onto natural GH pulses; DAC produces a sustained, less pulsatile elevation.
- Naming: No-DAC is synonymous with "Mod GRF 1-29." "CJC-1295" alone often implies the DAC form.
- Research framing: No-DAC is studied for short, pulse-preserving signaling, frequently paired with a ghrelin-mimetic; DAC is studied as a long-acting analog for durable receptor stimulation.
Frequently Asked Questions
Are CJC-1295 No-DAC and Mod GRF 1-29 really the same thing? Yes. In practical terms the two names refer to the identical modified GRF(1-29) molecule. The "No-DAC" label exists mainly to contrast it with the albumin-binding DAC version.
Why would a longer half-life not simply be "better"? Because growth hormone physiology is built around pulses. A longer half-life trades pulsatility for duration, and whether that trade is advantageous is an open research question, not a settled fact. The two compounds model different hypotheses.
Do they target different receptors? No. Both act at the GHRH receptor on pituitary cells. The DAC modification changes pharmacokinetics — how long the molecule persists — not which receptor it binds.
Browse the full growth-hormone secretagogue category and related mechanism explainers in the Trulogic library.
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