Trust Signals
Written by the FormBlends Medical Team. Evidence graded by type (human RCT, human PK study, animal, mechanistic). All cited statistics trace to named, real publications. No ghost statistics. Last reviewed 2026-05-29.
Key Takeaways
- The DAC linker extends CJC-1295 half-life from roughly 30 minutes to approximately 6 to 8 days by covalent albumin binding, confirmed in the 2006 Teichman et al. human pharmacokinetic study.
- CJC-1295 without DAC (Mod GRF 1-29) preserves a GH pulse shape closer to physiological secretion; CJC-1295 with DAC produces a sustained, flattened GH elevation sometimes called IGF-1 bleed.
- Neither form is FDA approved or legally compoundable in the US under current 503A and 503B rules; both are research compounds.
- The maleimide group in the DAC linker itself degrades in aqueous solution, meaning a reconstituted DAC product sitting in a vial loses albumin-binding capacity over time independent of peptide stability.
- A legitimate COA should confirm molecular weight by mass spectrometry: approximately 3367 Da for the no-DAC form, approximately 5040 Da for the DAC form, plus HPLC purity at or above 98 percent.
Direct Answer: DAC vs No DAC in Plain Terms
DAC vs no DAC is a choice between two half-life profiles for the same GHRH analogue backbone. The DAC version runs for nearly a week per injection; the no-DAC version clears in roughly 30 minutes and better mimics natural GH pulsatility. Neither is superior in every context. The right choice depends on dosing convenience, pulsatility goals, and your tolerance for sustained IGF-1 elevation.
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- What exactly is the DAC modification?
- How do the two forms work differently at the receptor level?
- What does the evidence actually show?
- Which form preserves pulsatile GH release?
- What do most pages get wrong about DAC?
- What is the formulation and stability reality?
- Honest head-to-head: DAC vs no DAC vs alternatives
- How to read a COA and dose correctly
- FAQ
- Sources
- Disclaimers
What Exactly Is the DAC Modification?
The Drug Affinity Complex (DAC) is a lysine-maleimido-propionic acid side chain added at position 31 of the CJC-1295 peptide. After subcutaneous injection, the maleimide group reacts with the free thiol of Cys-34 on serum albumin via a thiol-maleimide Michael addition, forming a stable covalent bond. Albumin has a circulatory half-life of roughly 19 to 21 days in humans. Hitchhiking on albumin shields the peptide from dipeptidyl peptidase-IV (DPP-IV) cleavage and renal filtration, which are the two primary degradation routes for short GHRH analogues.
The no-DAC form (Mod GRF 1-29) lacks this linker entirely. Its four amino acid substitutions (Ala-2 replaced by D-Ala, Phe-27 by Aib, Ser-28 by D-Ala, and Leu-4 by Leu or related changes depending on the exact synthesis) improve resistance to DPP-IV relative to native GHRH(1-29), but the peptide still clears within about 30 minutes without the albumin anchor.
How Do the Two Forms Work Differently at the Receptor Level?
Both forms bind the same target: the GHRH receptor (GHRHR), a Gs protein-coupled receptor expressed on somatotroph cells of the anterior pituitary. Receptor activation elevates intracellular cAMP, triggering GH synthesis and secretion. This part is identical for both forms. The difference is entirely pharmacokinetic, not pharmacodynamic at the receptor.
Where this matters clinically: the GHRHR undergoes homologous desensitization with continuous stimulation. Prolonged receptor occupancy, as produced by the DAC form, can reduce somatotroph responsiveness over time. The no-DAC form, because it clears rapidly, allows receptor recovery between doses. This is an established receptor pharmacology principle (tachyphylaxis), not speculation, though the quantitative extent of GHRHR desensitization in humans with multi-day DAC dosing is not precisely characterized in published clinical data.
What Does the Evidence Actually Show?
| Claim | Best Evidence Type | Key Source | Effect Direction | Confidence |
|---|---|---|---|---|
| CJC-1295 with DAC extends half-life to approximately 6 to 8 days | Human PK dose-escalation study | Teichman et al., J Clin Endocrinol Metab, 2006 | Strongly positive | High |
| CJC-1295 with DAC elevates mean 24-hour GH 2 to 3-fold above baseline | Human PK/PD study (n=65) | Teichman et al., 2006 | Positive | Moderate |
| Mod GRF 1-29 (no DAC) produces short, acute GH pulse similar to native GHRH | Human PK study and GHRH analogue literature | Broadly established in GHRH pharmacology literature | Positive (pulse shape) | Moderate |
| GHRH analogue plus GHRP combination amplifies GH pulse synergistically | Human controlled studies | Multiple studies in GHRH+GHRP combination literature | Strongly positive | Moderate to High |
| DAC-linked maleimide degrades in aqueous solution before albumin binding | Maleimide hydrolysis chemistry, established organic chemistry | General maleimide conjugate literature (Lyon et al., Nat Biotechnol 2014 context) | Negative (formulation risk) | Moderate |
| GHRHR desensitization with prolonged agonist exposure | In vitro and animal data | Receptor pharmacology literature, mechanism | Potentially negative | Low (clinical translation uncertain) |
| DAC form improves lean mass or reduces fat in humans | No dedicated human body composition RCT identified | Not established | Unknown | Very Low |
Which Form Preserves Pulsatile GH Release?
GH is secreted in discrete pulses, typically 6 to 12 per 24 hours in healthy adults, with the largest pulse occurring in early slow-wave sleep. Pulsatility is physiologically important: continuous GH exposure, as seen in acromegaly, produces different downstream signaling than pulsatile exposure. Hepatic GH receptor dynamics and IGF-1 production are sensitive to pulse pattern, not just total GH exposure.
CJC-1295 without DAC injected 30 to 60 minutes before the anticipated sleep window can amplify the nocturnal GH pulse while still allowing normal GH trough periods between injections. The GH elevation resolves within 2 to 3 hours, preserving the trough.
CJC-1295 with DAC eliminates this precision entirely. Its week-long action means GH and downstream IGF-1 are continuously elevated at a moderate level. Some users and clinicians describe this as a "GH bleed," though the term is colloquial rather than a clinical diagnosis. Whether continuous moderate elevation or high-amplitude pulsatile elevation produces better outcomes for a given goal (recovery, body composition, sleep) is not resolved by clinical evidence.
What Do Most Pages Get Wrong About DAC?
Most comparison articles treat DAC vs no DAC as a simple "long-acting vs short-acting" binary and stop there. Three things are almost universally omitted:
1. The maleimide hydrolysis problem. The DAC linker relies on a reactive maleimide group forming a bond with albumin's Cys-34 after injection. Maleimides hydrolyze in aqueous conditions, converting the reactive maleimide to an open-chain maleamic acid that can no longer bind thiol groups. Research on maleimide-conjugated antibody-drug conjugates (Lyon et al., Nature Biotechnology, 2014) has documented this retro-Michael reaction. For a reconstituted CJC-1295 DAC product sitting in a vial at room temperature or even at 4 degrees Celsius, the albumin-binding capacity decays over time. You can still have a full-concentration, structurally intact peptide that no longer binds albumin and therefore behaves functionally like the no-DAC form. No commodity page explains this. It means stability testing of the DAC form must include assessment of the maleimide group, not just peptide purity by HPLC.
2. The "Mod GRF 1-29" naming confusion. Vendors and forums use "CJC-1295 without DAC" and "Mod GRF 1-29" interchangeably, and they are the same compound. However, some vendors sell a product labeled "CJC-1295" that is actually just Mod GRF 1-29 without clarifying the DAC status. Mass spectrometry confirmation of molecular weight is the only reliable way to verify which compound you actually have. A molecular weight near 3367 Da indicates no-DAC; near 5040 Da indicates DAC present.
3. The regulatory reality. The FDA has placed CJC-1295 on the 503A and 503B lists of bulk drug substances that compounding pharmacies are not permitted to use. This is not a grey area. Products sold online as "research chemicals" are not subject to GMP manufacturing standards, and purity claims on vendor websites without accompanying third-party COAs are unverifiable.
What Is the Formulation and Stability Reality?
Both forms are supplied as lyophilized (freeze-dried) powder. As powder, peptide stability at minus 20 degrees Celsius is measured in years for most well-synthesized peptides, though oxidation of methionine or cysteine residues can occur even in dry form if oxygen exposure is present during vial sealing.
After reconstitution with bacteriostatic water:
- No-DAC form: best used within roughly 4 weeks when refrigerated at 4 degrees Celsius. Peptide bond hydrolysis and non-specific adsorption to vial walls reduce effective concentration over time.
- DAC form: the same peptide stability concerns apply, plus the additional maleimide hydrolysis problem described above. The longer you wait after reconstitution, the lower the fraction of DAC molecules capable of binding albumin. There is no published kinetics study specific to CJC-1295 DAC maleimide hydrolysis at refrigerator temperature, so the exact rate cannot be stated with precision. Directionally, use reconstituted DAC product promptly rather than storing for extended periods.
Never reconstitute with plain sterile water if you intend to use the product across multiple sessions. Sterile water lacks a bacteriostatic agent and allows microbial growth. Bacteriostatic water (0.9% benzyl alcohol) is the correct diluent.
Honest Head-to-Head: DAC vs No DAC vs Alternatives
| Parameter | CJC-1295 with DAC | CJC-1295 without DAC (Mod GRF 1-29) | Sermorelin | Tesamorelin |
|---|---|---|---|---|
| Half-life | Approximately 6 to 8 days | Approximately 30 minutes | Approximately 10 to 20 minutes | Approximately 26 minutes |
| Preserves GH pulsatility | No | Yes (with timed dosing) | Yes | Yes (daily injection) |
| Injection frequency | Once or twice weekly | Multiple times per week to daily | Daily | Daily |
| Human clinical trial data | Yes (Teichman et al. 2006) | Limited dedicated trials; relies on GHRH analogue literature | Yes, multiple | Yes, robust RCT data (HIV-associated lipodystrophy) |
| FDA regulatory status | Not approved; not compoundable | Not approved; not compoundable | Not approved (compounding restrictions vary) | FDA approved (Egrifta, specific indication) |
| IGF-1 bleed risk | Higher (sustained elevation) | Lower (episodic elevation) | Lower | Moderate (daily dosing) |
| Where DAC loses | Loses on pulsatility, on maleimide formulation complexity, on regulatory standing, and on the theoretical tachyphylaxis concern. Convenience (less frequent injections) is its primary practical advantage. | |||
How to Read a COA and Dose Correctly
What a legitimate COA must contain:
- HPLC purity at or above 98 percent with a chromatogram, not just a number
- Mass spectrometry result confirming molecular weight (DAC: approximately 5040 Da; no-DAC: approximately 3367 Da)
- Endotoxin testing (LAL assay) below 1 EU per mg
- Water content (Karl Fischer titration), because lyophilized peptides carry residual water that affects effective dose
- A batch number that matches the vial label
Reconstitution math: If you have a 2 mg vial and add 2 mL of bacteriostatic water, each 0.1 mL (10 units on an insulin syringe) delivers 100 mcg. Double the water volume halves the concentration. Write this on a label and attach it to the vial. A dosing error by a factor of 10 is possible if the math is done at injection time without a label.
What degraded product looks like: A properly lyophilized peptide appears as a white to off-white fluffy powder. Yellowing, clumping, or an amber liquid after reconstitution suggests oxidation or contamination. A reconstituted solution should be clear and colorless. Cloudiness after mixing suggests particulate matter or protein aggregation. Do not inject a cloudy solution.
Dosing ranges from published research (descriptive, not prescriptive): The Teichman et al. 2006 study used CJC-1295 with DAC at doses ranging from 30 mcg per kg to 120 mcg per kg in single-dose and multi-dose cohorts. Research use contexts vary widely. No dose has been established as safe or effective by the FDA for these compounds.
FAQ
What does DAC stand for in CJC-1295?
DAC stands for Drug Affinity Complex. It is a lysine-maleimido-propionic acid linker attached to the CJC-1295 peptide that covalently binds to serum albumin after injection, dramatically extending the half-life from roughly 30 minutes to approximately 6 to 8 days.
What is CJC-1295 without DAC also called?
CJC-1295 without DAC is frequently sold and discussed under the name Modified GRF(1-29), often abbreviated as Mod GRF 1-29. It is a 29-amino-acid analogue of endogenous GHRH with four amino acid substitutions to improve stability, but it lacks the albumin-binding linker.
Which form preserves natural pulsatile GH release?
CJC-1295 without DAC (Mod GRF 1-29) preserves pulsatile GH release because its short half-life of roughly 30 minutes allows GH levels to rise and fall in a pattern closer to physiological secretion. CJC-1295 with DAC produces a prolonged, blunted elevation that does not replicate normal pulsatility.
How often do you inject each version?
CJC-1295 without DAC is typically injected multiple times per week, often paired with a GHRP, because its active window is short. CJC-1295 with DAC needs only once or twice weekly dosing due to its multi-day half-life from albumin binding.
Does CJC-1295 with DAC cause IGF-1 bleed?
Yes. The sustained GH elevation from CJC-1295 with DAC produces a continuous background rise in IGF-1, which some researchers call IGF-1 bleed. This can push IGF-1 outside normal range with repeated weekly dosing and is a meaningful safety consideration not present with the short-acting no-DAC form.
Which form is better for sleep-related GH pulses?
CJC-1295 without DAC timed 30 to 60 minutes before sleep can amplify the natural nocturnal GH pulse. CJC-1295 with DAC cannot replicate this because its action is continuous and not timed to any specific physiological window.
How stable is each form in solution?
Both forms degrade faster in aqueous solution than as lyophilized powder. The no-DAC form is especially vulnerable to peptide bond hydrolysis and should be used within a few weeks of reconstitution when stored at 4 degrees Celsius. The DAC form has the same general peptide stability concerns but its albumin-binding maleimide group can also hydrolyze before injection, reducing binding efficiency.
Can you use CJC-1295 without DAC without a GHRP?
Yes, but clinical data showing meaningful GH elevation in humans comes predominantly from studies combining GHRH analogues with GHRPs. Using Mod GRF 1-29 alone is pharmacologically rational but the evidence base for the combination is meaningfully stronger than for either agent alone.
Is CJC-1295 with or without DAC approved by the FDA?
Neither form is FDA approved as a drug product for general use. They are research compounds. The FDA has specifically placed CJC-1295 on its list of bulk drug substances that may not be compounded under section 503A and 503B, meaning licensed compounding pharmacies in the US cannot legally compound it for patient use.
What should a COA show for a quality CJC-1295 product?
A certificate of analysis should show HPLC purity at or above 98 percent, mass spectrometry confirmation of the correct molecular weight (DAC form approximately 5040 Da, no-DAC form approximately 3367 Da), endotoxin testing results below 1 EU per mg, and water content by Karl Fischer titration.
Which version has stronger human clinical evidence?
CJC-1295 with DAC has more published human pharmacokinetic and GH-elevation data, including a 2006 dose-escalation study by Teichman et al. in the Journal of Clinical Endocrinology and Metabolism. The no-DAC form has less dedicated clinical trial data, though its mechanism is well supported by the broader GHRH literature.
How do you reconstitute CJC-1295 correctly?
Use bacteriostatic water (0.9% benzyl alcohol) rather than sterile water. Add the diluent slowly down the side of the vial, never inject directly onto the lyophilized cake. Swirl gently rather than shaking. Calculate your dose in micrograms per injection and confirm the math before drawing. Label the vial with the date of reconstitution and store at 4 degrees Celsius.
Sources
- 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.
- Lyon RP, Setter JR, Bovee TD, et al. Self-hydrolyzing maleimides improve the stability and pharmacological properties of antibody-drug conjugates. Nat Biotechnol. 2014;32(10):1059-1062.
- Frohman LA, Jansson JO. Growth hormone-releasing hormone. Endocr Rev. 1986;7(3):223-253.
- US Food and Drug Administration. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act. FDA.gov. Accessed 2026.
- Casanueva FF. Physiology of growth hormone secretion and action. Endocrinol Metab Clin North Am. 1992;21(3):483-517.
- Walker RF. Sermorelin: a better approach to management of adult-onset growth hormone insufficiency? Clin Interv Aging. 2006;1(4):307-308.
- Dhillon S. Tesamorelin: a review of its use in the management of HIV-associated lipodystrophy. Drugs. 2011;71(8):1071-1091.