What Is Modified GRF 1-29? (CJC-1295 Without DAC)

Modified GRF 1-29 is a synthetic analog of the first 29 amino acids of growth-hormone-releasing hormone (GHRH 1-29, the same core sequence as sermorelin), carrying four amino-acid substitutions that improve its stability against enzymatic breakdown. It is most commonly marketed under the name “CJC-1295 without DAC,” and in laboratory models it acts as an agonist at the GHRH receptor.

Research-use-only (RUO) note: Modified GRF 1-29 is studied as a research chemical. The information below summarizes preclinical, in-vitro, and animal findings on the underlying GHRH-analog chemistry. It is not a description of effects in humans and is not medical guidance.

Quick facts

• Class: tetra-substituted GHRH(1-29) analog (GHRH-receptor agonist studied in the lab)
• Also known as: CJC-1295 without DAC (“no-DAC”), tetrasubstituted GRF 1-29, Mod GRF 1-29
• Core sequence: first 29 residues of GHRH — the same fragment as sermorelin
• Research focus: the GH / IGF-1 signaling axis in preclinical models

What is Modified GRF 1-29?

Endogenous growth-hormone-releasing hormone (GHRH) is a 44-amino-acid peptide. Structure-activity work established that the first 29 residues — GHRH(1-29)-NH₂ — retain essentially the full receptor activity of the parent molecule, which is why this shorter fragment (sermorelin) became the standard research scaffold. Modified GRF 1-29 takes that 29-residue backbone and introduces four substitutions intended to slow enzymatic degradation, giving researchers a more stable GHRH-analog tool than the unmodified fragment.

The naming confusion: Mod GRF 1-29 vs CJC-1295

This is the single most common point of confusion, so it is worth stating plainly. “CJC-1295” is used in the marketplace to describe two distinct molecules:

• CJC-1295 WITH DAC – the tetra-substituted GHRH(1-29) analog plus a Drug Affinity Complex (DAC), a group that binds covalently to serum albumin. This is the long-acting version.
• CJC-1295 WITHOUT DAC – the same tetra-substituted GHRH(1-29) analog without the albumin-binding group. This short-acting molecule is what “Modified GRF 1-29” refers to. Mod GRF 1-29 = CJC-1295 no-DAC.

In other words, the only chemical difference between the two “CJC-1295” products is the DAC attachment. For background on the albumin-binding variant, see CJC-1295, and for the parent GHRH(1-29) fragment, see Sermorelin.

What does the research show?

Because Modified GRF 1-29 shares its active sequence with the broader GHRH(1-29)-analog family, the most informative published data come from studies on that scaffold. A 1994 pharmacokinetic study in normal men reported that adding a single D-Ala₂ substitution to GHRH(1-29)-NH₂ lowered metabolic clearance and extended the disappearance half-life relative to the unmodified peptide — direct evidence that these substitutions confer enzymatic stability. The DAC-equipped relative, CJC-1295 with DAC, was characterized in a 2006 clinical study reporting dose-dependent increases in GH and IGF-1 with an estimated half-life of roughly 6–8 days, illustrating how the DAC attachment — absent in Mod GRF 1-29 — is what drives the long duration of action. All such findings are reported here strictly as published research on GHRH-analog chemistry.

Mechanisms studied in the lab

• GHRH-receptor agonism: the 29-residue sequence engages the GHRH receptor (a Gs-coupled receptor) in preclinical models, the same target as native GHRH.
• Four substitutions for protease resistance: swaps studied for their ability to slow cleavage by enzymes such as DPP-IV, improving the peptide’s stability over the unmodified fragment.
• No DAC, shorter duration: without the albumin-binding group, the molecule is short-acting in research models — the key contrast with CJC-1295 with DAC.

Research status

Modified GRF 1-29 (CJC-1295 without DAC) is a research-use-only chemical. It is not approved by the FDA for human use, is not a dietary supplement, and is not intended to diagnose, treat, cure, or prevent any disease. It should be handled only by qualified personnel in an appropriate laboratory setting.

Related research peptides

Bolt Peptide does not carry Modified GRF 1-29 as a separate listing. Researchers exploring GHRH-analog chemistry can browse the full research peptide catalog, and may find the comparison article CJC-1295 vs Ipamorelin useful for understanding how GHRH analogs are studied alongside growth-hormone secretagogues.

FAQ

Is Modified GRF 1-29 the same as CJC-1295? It is the same as CJC-1295 without DAC. CJC-1295 with DAC is a separate, longer-acting molecule that adds an albumin-binding group to the same core sequence.

How is it related to sermorelin? Both are built on the GHRH(1-29) sequence. Sermorelin is the unmodified fragment; Modified GRF 1-29 adds four substitutions studied for greater enzymatic stability.

Can it be used in humans? No. It is a research-use-only chemical and is not approved or intended for human or veterinary use.

References

1. Cervini LA, et al. Human GHRH(1-29)-NH2: systematic structure-activity relationship studies. J Med Chem. 1998.
2. Soule S, et al. Incorporation of D-Ala2 in GHRH(1-29)-NH2 increases half-life and decreases metabolic clearance in normal men. J Clin Endocrinol Metab. 1994.
3. Teichman SL, et al. Prolonged stimulation of GH and IGF-I by CJC-1295, a long-acting GHRH analog. J Clin Endocrinol Metab. 2006.

For research use only. Not a drug, supplement, or food; not FDA-approved; not for human or veterinary use. Statements have not been evaluated by the FDA.