CJC-1295 vs CJC-1295 with DAC: Pulsatile vs Sustained GH Release
CJC-1295 (Modified GRF 1-29) and CJC-1295 with DAC share the same GHRH backbone but differ in half-life by orders of magnitude. This comparison summarizes the pharmacokinetic, mechanistic, and regulatory distinctions that determine which variant is appropriate for a given research question.
Research reference only. The information in this article is a summary of peer-reviewed scientific literature. It does not constitute medical advice and is not intended to guide human use. See our full disclaimer.
Researchers studying the hypothalamic-pituitary-somatotropic axis frequently choose between two structurally related growth hormone-releasing hormone (GHRH) analogues that share the same 29-amino-acid backbone but differ by a single chemical modification: CJC-1295 without Drug Affinity Complex (commonly written as Modified GRF 1-29, sometimes "CJC-1295 no-DAC") and CJC-1295 with DAC. The DAC moiety — a maleimidopropionic acid linker conjugated to the lysine residue at position 30 of the GHRH(1-29) sequence — transforms a peptide with a circulating half-life of approximately 30 minutes into one with a half-life measured in days. That single biochemical change produces two compounds with substantially different pharmacokinetic profiles, different growth hormone (GH) release patterns, and different research applications.
The choice between the two has been described in the literature as a choice between preserving the natural pulsatile pattern of endogenous GH secretion (no-DAC) and producing sustained, non-pulsatile elevation of GH and downstream insulin-like growth factor 1 (IGF-1) (with-DAC). Each pattern models a distinct physiological state, and each carries implications for receptor desensitization, IGF-1 feedback, and the interpretation of downstream metabolic endpoints. This article examines the published receptor pharmacology, evidence base, and regulatory status of each compound to support investigators selecting between them for laboratory research.
Research reference only. All information on this page is a summary of peer-reviewed scientific literature and does not constitute medical advice. See individual library profiles for full compound data.
CJC-1295 (Modified GRF 1-29): mechanism and evidence base
CJC-1295 without DAC, more precisely designated Modified GRF 1-29, is a synthetic analogue of native GHRH(1-29). The "modified" designation refers to four amino-acid substitutions within the 1–29 sequence — primarily at positions 2, 8, 15, and 27 — that confer enzymatic resistance against dipeptidyl peptidase-4 (DPP-4) degradation and trypsin-mediated cleavage. These substitutions extend the molecule's plasma stability beyond native GHRH(1-29), which is cleared within minutes, while preserving the receptor-binding domain that engages the GHRH receptor on anterior pituitary somatotroph cells.
Without the DAC linker, Modified GRF 1-29 retains a comparatively short circulating half-life of approximately 30 minutes in published pharmacokinetic studies. This brevity is functionally significant: it allows the compound to act as a transient GHRH receptor agonist, producing a discrete GH pulse that mirrors the physiologic pulsatile pattern in which endogenous GHRH triggers somatotrope activation. After the bolus is cleared, somatostatin-mediated negative feedback can re-establish baseline, and a subsequent dose produces another discrete pulse. This is mechanistically important because pulsatile GH exposure is the pattern under which GH receptor signaling has been characterized in most preclinical literature, and chronic, non-pulsatile exposure has been associated in older endocrinology studies with receptor desensitization and altered IGF-1 dynamics.
A 2026 critical review of peptide-analog drugs (PMID 41880199, DOI 10.1210/jc.2005-1536) notes that CJC-1295 and related GHRH analogues have been positioned in research literature as "more selective and ostensibly safer alternatives" to anabolic-androgenic steroids, but cautions that most published clinical evidence derives from therapeutic dosing protocols rather than from the supraphysiological regimens common in non-medical contexts. The review identifies cardiovascular strain, insulin resistance, and dyslipidemia as documented risks under uncontrolled dosing patterns.
Visit the CJC-1295 compound library entry for full pharmacokinetic data, citation index, and indexed PubMed sources.
CJC-1295 with DAC: mechanism and evidence base
CJC-1295 with DAC retains the same Modified GRF 1-29 backbone but adds the Drug Affinity Complex modification at the lysine residue at position 30. The DAC linker is a maleimidopropionic acid moiety that forms a covalent disulfide bond with the free cysteine residue (Cys-34) on circulating human serum albumin almost immediately after subcutaneous administration. Because albumin has a plasma half-life of approximately 19 days, the resulting albumin-peptide adduct circulates for far longer than free Modified GRF 1-29: published single-dose pharmacokinetic data in healthy adults demonstrate sustained elevation of GH and IGF-1 for six to eight days post-administration.
A seminal pharmacokinetic study published in the Journal of Clinical Endocrinology & Metabolism (PMID 16352683, Teichman et al., 2006, DOI 10.1210/jc.2005-1536) characterized the sustained release profile of CJC-1295 with DAC in healthy adults. The investigators reported dose-dependent and sustained elevation of GH and IGF-1 following single subcutaneous injections, with biological activity maintained well beyond the time course observed for unmodified GHRH or for Modified GRF 1-29 alone. The same study reported that weekly dosing supported cumulative IGF-1 elevation across multiple administrations — a pharmacokinetic property that has informed the design of research protocols using weekly subcutaneous administration as the canonical dosing schedule.
Mechanistically, the consequence of this prolonged half-life is that GH release is no longer pulsatile. Instead, somatotroph cells receive continuous agonist exposure at the GHRH receptor, producing a sustained elevation of GH secretion at the pituitary level. This is qualitatively distinct from the pulsatile pattern produced by Modified GRF 1-29 (no-DAC) and is mechanistically closer to the continuous elevation that characterizes acromegalic states than to physiologic GH secretion. Researchers therefore use the DAC variant to model sustained somatotropic axis activation rather than physiologic pulsatility.
Visit the CJC-1295 with DAC compound library entry for full pharmacokinetic data, indexed PubMed citations, and chemical references.
Side-by-side comparison
| Feature | CJC-1295 (Modified GRF 1-29, no-DAC) | CJC-1295 with DAC |
|---|---|---|
| Backbone | Modified GHRH(1-29) — substitutions at residues 2, 8, 15, 27 | Same backbone plus DAC linker at Lys-30 |
| Albumin binding | None | Covalent via maleimidopropionic acid linker |
| Plasma half-life (human) | ~30 minutes | ~6–8 days |
| GH release pattern | Pulsatile, discrete pulses | Sustained, non-pulsatile elevation |
| IGF-1 profile | Transient elevation per dose | Cumulative elevation with weekly dosing |
| Dosing interval (research protocols) | Multiple times per day | Once weekly subcutaneous |
| Primary referenced PMID | 41880199 (2026 critical review) | 16352683 (Teichman et al., 2006) |
| FDA approval status | Investigational; not approved | Investigational; not approved |
| 503A compounding status | Under Review | Under Review |
| WADA prohibited list (2026) | Prohibited (GHRH analogues, class S2) | Prohibited (GHRH analogues, class S2) |
| Primary research applications | Pulsatile GH biology, physiologic somatotropic modeling | Sustained GH/IGF-1 elevation modeling, long-duration receptor occupancy studies |
Differential research applications
The choice between Modified GRF 1-29 (no-DAC) and CJC-1295 with DAC turns on which physiologic state the research question is attempting to model.
Modified GRF 1-29 is the preferred tool when the experimental design requires preservation of pulsatile GH release. This pattern is important when investigators are studying GH receptor sensitivity dynamics, the interplay between GH pulses and somatostatin-mediated feedback, or downstream tissue responses (such as IGF-1 generation, lipolytic signaling, or counter-regulatory glucose effects) that have been characterized under pulsatile rather than continuous exposure. Studies of somatotrope physiology, GH pulse-frequency analysis, and short-duration pharmacodynamic experiments typically rely on the short-acting variant because its rapid clearance permits multiple discrete dose-response observations within a single experimental day.
CJC-1295 with DAC is the preferred tool when sustained somatotropic axis activation is itself the variable under investigation. Long-duration protocols examining cumulative IGF-1 elevation, models of chronic GHRH receptor occupancy, and studies of compounds in conjunction with growth hormone secretagogue receptor (GHS-R) ligands (such as ipamorelin or MK-677) often benefit from the once-weekly dosing convenience and the sustained baseline elevation it provides. Investigators modeling acromegaly-adjacent physiology, or studying the metabolic consequences of continuous rather than pulsatile somatotropic stimulation, find the DAC variant pharmacologically more appropriate.
In comparative pharmacokinetic-pharmacodynamic studies, the two variants are sometimes administered to parallel cohorts within the same experimental protocol to dissect which downstream endpoints are pulsatility-dependent and which are exposure-duration-dependent. Practical considerations also factor into selection: the DAC variant's once-weekly schedule simplifies long-duration protocols, but reagent cost per milligram is typically higher, and the longer washout period (multiple weeks) complicates crossover designs.
Regulatory and compounding status
Neither variant of CJC-1295 holds FDA approval for any indication. Both are classified as investigational research compounds, and both currently appear on the FDA's list of bulk drug substances under active review for the 503A compounding framework. The July 2026 Pharmacy Compounding Advisory Committee (PCAC) meeting agenda has not, in publicly available pre-meeting summaries, included either CJC-1295 variant among the named compounds under direct evaluation, but the broader category of GHRH analogues remains an area of regulatory uncertainty for compounding pharmacies operating under Section 503A of the Federal Food, Drug, and Cosmetic Act.
The European Medicines Agency has not granted marketing authorization for either variant. The World Anti-Doping Agency 2026 Prohibited List names "growth hormone-releasing factors" and explicitly includes GHRH analogues in Class S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics), which means both no-DAC and with-DAC variants are prohibited substances in competitive sport at all times, in and out of competition. Detection remains analytically challenging due to structural homology with endogenous GHRH and the short biomarker windows associated with the no-DAC variant; the DAC variant's longer biological half-life produces a longer detection window in principle, though validated mass-spectrometry assays for the modified albumin adduct remain a developing area of anti-doping methodology.
Cited studies
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PMID 16352683 — Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA. "Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults." (Journal of Clinical Endocrinology & Metabolism, 2006). https://doi.org/10.1210/jc.2005-1536
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PMID 41880199 — "A new era of doping? Use of peptide and peptide-analog drugs in recreational and professional sport and bodybuilding: a critical review." (2026). Reference for the broader regulatory and pharmacologic context of GHRH analogues including CJC-1295.
See also: CJC-1295 compound library entry | CJC-1295 with DAC compound library entry
For laboratory research purposes only. Not for human or animal consumption. Compounds described are not approved by the FDA for human or veterinary use unless explicitly stated.