Mod GRF 1-29 (CJC-1295 without DAC)

What it is

GHRH is the signal from the hypothalamus to the pituitary gland to release growth hormone. The first 29 of its amino acids are sufficient for the effect; this fragment is called GRF(1-29) and was approved in the US as sermorelin. Mod GRF 1-29 is a chemically modified version of it with 4 substitutions compared with natural GHRH. If an anchor that binds to albumin is additionally attached to this backbone, the result is CJC-1295 with DAC, which acts for days. Without the anchor, a short-acting peptide remains.

This is precisely the origin of the great naming chaos in the peptide scene: the form without the anchor is often sold under the label CJC-1295. In 2009, a Norwegian laboratory examined a product with this label that had been seized by police and customs and found a 29-amino-acid peptide without DAC. So anyone who buys CJC-1295 often has Mod GRF in the vial, and vice versa.

Why the substitutions

Natural GRF is broken down rapidly in the blood. The enzyme DPP-IV cleaves it right at the start, between the second and third amino acids; in addition, the amino acid at position 8 rearranges chemically and the one at position 27 oxidizes. Peptide chemists therefore began specifically substituting individual building blocks back in the 1990s to make GRF more stable, and at position 15 they chose a building block that improves binding to the receptor. Such analogs were considerably more stable and effective in the laboratory and in animals.

Mod GRF stands in this tradition. Whether the greater stability actually leads to a longer or stronger effect in humans has not been measured, however. That this transfer cannot be taken for granted was shown as early as 1989 by a study in healthy men: a GRF analog that was considered superactive in rats did not release more growth hormone in healthy men than unmodified GRF(1-29), nor did it disappear from the blood more slowly.

How it is supposed to work

Mod GRF binds to the GHRH receptor of the pituitary gland and amplifies the signal for release there. The gland remains the pacemaker; somatostatin and IGF-1 continue to apply the brakes. Because the peptide without the anchor disappears again quickly, it is meant to trigger a single, short growth hormone pulse that resembles the natural pattern, rather than raising the level for days as the DAC form does.

In practice it is usually combined with a ghrelin mimetic such as ipamorelin or GHRP-2. That a GHRH signal and a ghrelin signal together work more strongly than either alone is established in humans for the substance classes. For Mod GRF in this combination there is no study; a 2026 review calls the rationale for this practice largely anecdotal.

What users report

In bodybuilding and biohacking forums, Mod GRF is a standard component of growth hormone stacks, typically together with ipamorelin and often after strength training, with the stated aim of amplifying the natural pulses. A 2026 clinical review systematically compared such forum protocols with the study evidence. As typical complaints among users of this peptide group, it lists water retention, tingling, muscle and joint pain and injection-site reactions, plus laboratory findings such as raised IGF-1. The review classifies the reports of effects as gray literature. We take them seriously as a picture of user experience, but they do not replace measurement under controlled conditions.

What the studies show

Khorram et al. 1997 — a GRF analog in older adults

19 healthy women and men aged between 55 and 71, single-blinded, 4 weeks of placebo, then 16 weeks of nightly injections of [Nle27]GHRH(1-29)-NH2. GH, IGF-1 and IGFBP-3 rose; IGF-1 remained elevated over 12 weeks. Skin thickness improved in both sexes, lean mass only in men. The only side effect was a temporary rise in blood lipids. Not Mod GRF, but its closest studied relative.

Aitman et al. 1989 — potency in animals is not potency in humans

Healthy men received unmodified GRF(1-29) or an analog that is superactive in animals under the skin. Growth hormone peak, total amount and rate of clearance from the blood did not differ. The authors suspect differences between the rat and human receptor. Here, too, Mod GRF was not studied; the finding applies only indirectly.

Dominikowski et al. 2026 — the classification

Clinical review of peptides of the growth hormone axis with four evidence levels. Mod GRF 1-29 is at the lowest level, D: no peer-reviewed human study, no measured half-life; statements on pulsatility and body composition are based on extrapolation from sermorelin and on gray literature.

Where the data stop

There is no published study in humans on Mod GRF 1-29 itself. Unknown are its half-life, duration of action, strength of the growth hormone response and effect on IGF-1, sleep, muscle or fat. All statements on this are derived from sermorelin, other GRF analogs and peptide chemistry. That such derivations can be wrong is shown by the 1989 study, in which an analog that was superior in animals had no advantage in humans.

The popular comparison with the DAC form is untested as well. That Mod GRF better preserves the natural pulses is pharmacologically plausible but has never been measured directly. The only study on the pulse pattern that is often cited actually examined CJC-1295 with DAC, and there, incidentally, the pulses were preserved as well.

Status, approval and legal

Mod GRF 1-29 is not approved as a medicine in Germany, the EU or the US and is sold as a research peptide, often under the name CJC-1295. In sport it is prohibited at all times: it falls under S2.2.4 of the WADA 2026 list and is named explicitly as mod-GRF in the annex of the German Anti-Doping Act. For CJC-1295, without distinguishing between the variants, the FDA cites serious adverse events and limited clinical data. We do not give dosage information for unapproved substances.

Safety

No safety data of its own exist. Known from the substance class are water retention, tingling in the hands and joint pain; in addition, insulin sensitivity may decrease. For CJC-1295, the FDA reports increased heart rate and a whole-body vasodilation reaction. Because IGF-1 is a growth signal, the peptide is considered problematic in active or past cancer, although a clinical cancer signal has not been demonstrated for the class. Then there is quality: in a not yet peer-reviewed analysis of 6,441 gray-market samples from 14 peptides, including CJC-1295, 41.6 to 71.1 percent failed depending on the standard applied, and because of the naming chaos it is not even certain whether the vial contains the variant with or without DAC.

Sources

• Dominikowski et al., Frontiers in Endocrinology 2026
• Khorram et al., Journal of Clinical Endocrinology and Metabolism 1997 – different GRF analog, only indirectly relevant to Mod GRF
• Aitman et al., Peptides 1989 – different GRF analog, only indirectly relevant to Mod GRF
• Campbell et al., Peptides 1994
• Jetté et al., Endocrinology 2005
• Henninge et al., Drug Testing and Analysis 2010
• Sigalos & Pastuszak, Sexual Medicine Reviews 2018
• Ionescu & Frohman, Journal of Clinical Endocrinology and Metabolism 2006 – CJC-1295 with DAC, only indirectly relevant to Mod GRF
• FDA, bulk drug substances that may present significant safety risks, as of 2026-04-22