Peptides / GH Axis
CJC-1295 Without DAC (Mod GRF 1-29) — Half-Life & Protocol Guide
Also known as: Modified GRF(1-29) · Mod GRF 1-29 · tetrasubstituted GRF(1-29)
Inferred Data
· No published human PK study for no-DAC form · Half-life inferred from GHRH analogue class
⚠ Data Transparency
No peer-reviewed human pharmacokinetic study for CJC-1295 without DAC has been published. The ~30-minute half-life is inferred from GHRH analogue class pharmacology and the DPP-4 resistance modifications (Ala2, Gln8, Ala15, Nle27 substitutions vs native GHRH). Native GHRH(1-29) t½ is ~7 minutes in humans (Frohman LA et al., J Clin Invest 1984; PMID 6371044). Use with caution; these figures may not reflect actual human clearance.
Quick Reference
| Parameter | Value | Source / Note |
|---|
| Common names | CJC-1295 no DAC · Mod GRF 1-29 · Modified GRF(1-29) | Research community terminology |
| Class | Short-acting GHRH analogue | Peptide / GH axis |
| Plasma half-life | ~30 min (inferred) | GHRH analogue class + DPP-4 resistance; no human PK study |
| DAC linker | None — no albumin binding | Distinguishes from CJC-1295 DAC (~6–8 d t½) |
| GH pulse duration | ~2–3 h per injection | GHRH analogue class pharmacology |
| Administration route | SC injection | No published IV or oral human data |
| Steady state | N/A (episodic dosing) | Short-acting; used per-injection basis |
| FDA status | Not approved — Research chemical | Only approved GHRH analogue: tesamorelin (Egrifta) |
| Data Quality | Inferred / Limited Data — no dedicated human PK study for no-DAC form published |
Plasma Half-Life
~30 min
Inferred — no dedicated human PK study. Native GHRH(1-29) t½ ~7 min in humans (PMID 6371044). DPP-4 substitutions extend clearance; exact human value unpublished.
GH Pulse Duration
~2–3 hours
Per injection, GHRH class
Dosing Frequency
2–3× daily
Typical research protocol
IGF-1 Elevation
Builds 6–24 h
Post-GH pulse; inferred
Pulsatility
Preserved
vs DAC version which blunts
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Mechanism of Action
GHRH Receptor Agonism
CJC-1295 without DAC contains the first 29 amino acids of GHRH with modifications at key positions to resist DPP-4 cleavage. Native GHRH(1-29) is cleaved at the Ala²-Gln(2) bond by dipeptidyl peptidase-4 within minutes; the amino acid substitutions in CJC-1295 no DAC — including D-Ala at position 2 and additional modifications at positions 8, 15, and 27 (exact substitutions may vary by manufacturer) — confer resistance to this cleavage. Like native GHRH, the compound binds the GHRH receptor on pituitary somatotrophs, activating the Gs/adenylyl cyclase/cAMP signaling cascade. This increases the pituitary GH pool size and augments the amplitude of natural pulsatile GH release. Each injection produces a GH pulse lasting approximately 2–3 hours.1
Pulsatility Preservation
Unlike CJC-1295 with DAC — which binds albumin via its maleimide linker and provides continuous GHRH stimulation for 6–8 days — the no-DAC form clears from plasma within approximately 2–3 hours, allowing the natural GH pulse pattern to recover between injections. This preservation of physiologic pulsatility is considered favorable by some researchers, as pulsatile GH secretion is important for optimal anabolic and lipolytic signaling. Continuous GHRH exposure, as produced by the DAC version, may blunt natural pulse amplitude over time by persistently occupying somatotroph GHRH receptors and depleting releasable GH stores. The short-acting no-DAC form avoids this concern.
Synergy with GHRPs
CJC-1295 without DAC is most commonly used in combination with a GHRP — typically ipamorelin — to simultaneously expand the GH pool via the GHRH mechanism and amplify pulse amplitude via the GHRP (ghrelin receptor) mechanism. This dual-mechanism approach produces synergistic GH stimulation in animal models: GHRH analogues increase the pool of releasable GH while GHRPs augment the signal that triggers release. Human synergy data from controlled clinical trials is not available; this rationale is based on animal research and the known additive physiology of the two receptor systems. IGF-1 elevation builds over 6–24 hours following the GH pulse.2
Three-Layer Pharmacokinetic Model
| Layer | Timeframe | Description |
|---|
| Layer 1 — Plasma t½ | ~30 min (inferred) | Compound clearance from plasma. No dedicated human PK study published. |
| Layer 2 — Near-complete clearance | ~2–3 hours (5× t½) | ~97% of dose cleared; pituitary somatotroph GH secretion continues during this window. |
| Layer 3 — Downstream effects | GH pulse ~2–3 h; IGF-1 builds 6–24 h | GH released from pituitary has its own clearance (~20 min t½); IGF-1 induction is slower. |
Clearance Timeline (5 × t½ = ~150 min)
Based on ~30-minute estimated half-life (inferred — no human study):
Note: These values are extrapolated from the ~30-minute estimated half-life. They are not derived from a published human pharmacokinetic study and should be interpreted with caution.
Administration Route Data
| Route | Status | Notes |
|---|
| Subcutaneous (SC) | Common research route | No published human PK study for this formulation; inferred from GHRH analogue class. |
| Intramuscular (IM) | No published data | Not characterized in literature for this compound. |
| Intravenous (IV) | GHRH class research only | Native GHRH IV data exists (Frohman 1984); not a clinical route for CJC-1295 no DAC. |
| Oral | Not bioavailable | Peptide; degraded in GI tract. No oral formulation exists. |
In-Class Comparison — GHRH Axis Compounds
| Compound | Class | Half-life | FDA Status | Route |
|---|
| CJC-1295 no DAC | GHRH analogue | ~30 min (inferred) | Not approved | SC |
| CJC-1295 DAC | GHRH analogue | ~6–8 days | Not approved | SC |
| Sermorelin | GHRH analogue | ~10–20 min | Not currently marketed | SC |
| Tesamorelin | GHRH analogue | ~26 min | FDA approved (Egrifta) | SC |
| Ipamorelin | GHRP / Ghrelin receptor | ~2 h (animal) | Not approved | SC |
Page metadata
Published: May 2026 · Data classification: Inferred / Limited Data · Evidence tier: Animal Study + class inference
No dedicated human PK study for CJC-1295 without DAC has been identified in peer-reviewed literature as of May 2026. The ~30-minute half-life is a community estimate consistent with GHRH analogue class pharmacology and DPP-4 resistance substitutions.
Safety & Regulatory Notice
CJC-1295 without DAC is not FDA-approved and has no published long-term human safety data. Unlike the DAC version, pulsatility blunting is not a concern with appropriate episodic dosing. However, risks of supraphysiologic GH stimulation — including fluid retention, insulin resistance, potential promotion of pre-existing malignancy, and injection site reactions — apply to all GHRH analogues. This page is for educational and research reference only. It does not constitute medical advice.
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Frequently Asked Questions
What is the half-life of CJC-1295 without DAC?
Approximately 30 minutes, inferred from GHRH analogue class pharmacology and the DPP-4 resistance modifications present in the compound. No specific peer-reviewed human pharmacokinetic study has been published for CJC-1295 without DAC. Native GHRH(1-29) has a human half-life of approximately 7 minutes (Frohman LA et al., J Clin Invest 1984; PMID 6371044). The DPP-4-resistant substitutions extend clearance, but exact human data are not available for this formulation.
What is the difference between CJC-1295 with and without DAC?
The DAC (Drug Affinity Complex) version includes a maleimide linker that covalently binds to serum albumin, extending the half-life to approximately 6–8 days, enabling once-weekly dosing and producing a continuous GHRH signal that may blunt natural GH pulsatility. CJC-1295 without DAC has a ~30-minute half-life, is typically dosed 2–3 times daily alongside a GHRP such as ipamorelin, and preserves the physiologic pulsatile GH secretion pattern. The no-DAC form produces a GH pulse per injection rather than sustained baseline elevation.
Is CJC-1295 no DAC the same as Mod GRF 1-29?
Yes. "Modified GRF(1-29)" and "Mod GRF 1-29" are alternative names for CJC-1295 without the DAC linker. The terms are used interchangeably in the research community. The compound is also referred to as tetrasubstituted GRF(1-29), reflecting its four amino acid substitutions relative to native GHRH(1-29) that confer DPP-4 resistance.
How often should CJC-1295 no DAC be injected?
Due to its ~30-minute half-life, CJC-1295 without DAC is typically injected simultaneously with ipamorelin or another GHRP, 2–3 times daily, to match the pulsatile dosing schedule. Near-complete plasma clearance occurs within approximately 2–3 hours (5 × 30 min). Research protocols vary significantly; there is no standardized human dosing regimen given the absence of clinical trials.
Is CJC-1295 without DAC FDA approved?
No. CJC-1295 without DAC is a research chemical with no FDA approval for any indication. The only FDA-approved GHRH analogue is tesamorelin (Egrifta), approved specifically for HIV-associated lipodystrophy. All other GHRH analogues including sermorelin, CJC-1295 (with or without DAC), and related peptides remain research compounds.
Why is CJC-1295 no DAC preferred over the DAC version by some researchers?
The no-DAC form preserves physiologic GH pulsatility, which is important for normal anabolic and lipolytic signaling. The DAC version's continuous GHRH stimulation over days may blunt natural GH pulse patterns by persistently occupying somatotroph GHRH receptors. Some researchers prefer the no-DAC form for its ability to mimic the intermittent GHRH signaling that normally drives pulsatile GH secretion from the pituitary.
Can CJC-1295 no DAC be combined with ipamorelin?
Yes, this is the most common research combination. CJC-1295 without DAC expands the pituitary GH pool via GHRH receptor agonism (Gs/cAMP pathway), while ipamorelin amplifies pulse amplitude via the ghrelin receptor (GHSR-1a) mechanism. This dual-receptor approach produces synergistic GH stimulation in animal models. Human synergy data from controlled clinical trials is not available; the rationale is based on animal research and the known additive physiology of the GHRH and ghrelin receptor systems.
What is the GH pulse duration from CJC-1295 no DAC?
The GH pulse typically lasts approximately 2–3 hours per injection, consistent with GHRH analogue class pharmacology. This duration is longer than the plasma half-life (~30 min) because pituitary somatotroph GH secretion continues after receptor activation and the released GH itself has its own clearance kinetics (~20-minute half-life in circulation). IGF-1 elevation, a downstream marker of GH action, builds over 6–24 hours following the GH pulse.
Related Compounds
References & Citations
- Frohman LA, Downs TR, Heimer EP, Felix AM. Dipeptidylpeptidase IV and trypsin-like enzymatic degradation of human growth hormone-releasing hormone in plasma. J Clin Invest. 1989;83(5):1533–1540. PMID 2539395. (DPP-4 cleavage of GHRH — mechanism basis for CJC-1295 no DAC substitutions)
- Frohman LA, Thominet JL, Webb CB, Vance ML, Uderman H, Rivier J, Vale W, Thorner MO. Metabolic clearance and plasma half-disappearance time of human growth hormone-releasing factor in man. J Clin Invest. 1984;73(5):1304–1311. PMID 6371044. (Native GHRH(1-29) t½ ~7 min in humans — primary baseline reference)
- 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. J Clin Endocrinol Metab. 2006;91(3):799–805. PMID 16352683. (DAC form comparator — only published human CJC-1295 PK; no-DAC form not studied)
- Walker RF. Sermorelin: A better approach to management of adult-onset growth hormone insufficiency? Clin Interv Aging. 2006;1(4):307–308. PMID 18047277. (GHRH analogue class context — sermorelin short-acting comparator)
- Falutz J, Allas S, Blot K, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007;357(23):2359–2370. PMID 18057338. (Tesamorelin — only FDA-approved GHRH analogue; comparative regulatory context)
About our data quality classifications
Halflife Labs classifies compound pharmacokinetic data by source quality: FDA-approved label data, peer-reviewed human PK studies, animal study data, and inferred/class-extrapolated data. CJC-1295 without DAC is classified as
Inferred / Limited Data because no dedicated human PK study has been published. See our
methodology page for the full framework. For compounds in this tier, the reported values are estimates only and should not be used for clinical dosing decisions.