Quick comparison
| Feature | CJC-1295 with DAC | Modified GRF 1-29 (no DAC) |
|---|---|---|
| Plasma half-life | 5.8 to 8.1 days (human, measured) | ~30 minutes (DPP-IV resistance only) |
| Albumin binding | Covalent thioether at Cys34 | None |
| GH release pattern | Sustained elevation; pulses preserved | Discrete pulse, returns to baseline in ~2 h |
| Typical dosing frequency | Weekly or twice weekly | 2 to 3 times daily |
| Human RCT data published | Yes (Teichman 2006; Ionescu & Frohman 2006) | No standalone human pharmacokinetic trial |
| Commonly paired with ipamorelin | Less common (timing mismatch) | Standard combination |
What the drug affinity complex modification does
Growth hormone-releasing hormone (GHRH) has a plasma half-life of roughly 2 to 5 minutes. Dipeptidylpeptidase-IV (DPP-IV) cleaves the Ala2-Asp3 bond rapidly, inactivating the peptide before much of it reaches pituitary somatotrophs. Additional serum endopeptidases degrade the remainder.
Modified GRF 1-29, sold as CJC-1295 without DAC, addresses this by substituting four amino acids: D-Ala at position 2, Gln at position 8, Ala at position 15, and Leu at position 27. These substitutions make the backbone resistant to DPP-IV while preserving GHRH receptor (GHRHR) binding affinity. The result is a half-life of approximately 30 minutes rather than 2 to 5 minutes, but the peptide still clears within a couple of hours.
The Drug Affinity Complex (DAC) takes a different approach. A maleimide-derivatized lysine is appended to the C-terminus of the same tetrasubstituted GRF(1-29) backbone. After subcutaneous injection, this maleimide group reacts spontaneously with the free thiol on Cys34 of circulating serum albumin, forming a stable covalent thioether bond. This is covalent linkage, not non-covalent plasma protein binding; the bond does not dissociate under physiological conditions. Because albumin has a half-life of approximately 19 days in humans and is not renally filtered, the bound peptide persists in circulation far longer than the free form.
Jetté et al. (2005) identified CJC-1295 as the most effective of three maleimide-conjugated GRF analogs tested in rat anterior pituitary assays. CJC-1295 produced 4-fold greater GH area-under-the-curve over 2 hours compared with native hGRF(1-29), and remained detectable in rat circulation more than 24 hours post-injection (Jette et al., Endocrinology 2005, in vitro and rat model).
Half-life and pharmacokinetics in human subjects
The first human data for CJC-1295 with DAC came from a Phase I/II randomized, placebo-controlled, double-blind, ascending-dose trial by Teichman et al. (2006), conducted across two cohorts with durations of 28 and 49 days. The trial enrolled 66 healthy adults aged 21 to 61 years.
A single subcutaneous injection produced dose-dependent increases in mean plasma GH concentrations of 2- to 10-fold lasting 6 or more days, and mean plasma IGF-1 concentrations of 1.5- to 3-fold lasting 9 to 11 days. The measured half-life of CJC-1295 was 5.8 to 8.1 days. After multiple doses, mean IGF-1 levels remained above baseline for up to 28 days. Doses of 30 and 60 micrograms per kilogram subcutaneously were described as safe and well tolerated (Teichman et al., JCEM 91(3):799, 2006, n=66).
For modified GRF 1-29, no equivalent standalone human pharmacokinetic trial has been published as of mid-2026. The 30-minute half-life estimate comes from DPP-IV resistance assays and from analogy to the parent GRF(1-29) structure. Anti-doping studies have detected modified GRF 1-29 in equine samples, confirming its use in practice, but equine pharmacokinetics do not translate directly to human data.
GH release pattern: pulse vs sustained stimulation
Modified GRF 1-29 produces a discrete GH pulse from pituitary somatotrophs. GH peaks within 15 to 30 minutes post-injection and returns to pre-injection levels within about 2 hours, closely tracking endogenous GHRH pulse kinetics. Researchers pairing it with ipamorelin, a selective GHS-R1a agonist, can achieve co-timed GH pulses through complementary receptor mechanisms.
The combination is well characterized. Ipamorelin activates the ghrelin receptor (GHS-R1a) rather than GHRHR, so the two peptides stimulate GH release through separate pathways simultaneously. In rat models, ipamorelin differed from earlier GH secretagogues by having 5-fold lower systemic plasma clearance than GHRP-6 and by not elevating cortisol or prolactin at research doses (Raun et al., Eur J Endocrinol 1998). More detail on the ipamorelin mechanism is in the CJC-1295 and ipamorelin research overview.
CJC-1295 with DAC produces a different pattern. Continuous GHRH receptor stimulation keeps both trough GH and pulse amplitude elevated throughout the dosing interval. A human study by Ionescu and Frohman (2006) used 20-minute blood sampling across 12 overnight hours in healthy men aged 20 to 40, assessed at baseline and 1 week after a single injection of 60 or 90 micrograms per kilogram. GH pulsatility was preserved: pulse amplitude and trough GH were both higher than pre-treatment, and IGF-1 was elevated (Ionescu and Frohman, JCEM 91(12):4792, 2006, human). This pattern contrasts with exogenous GH administration, which suppresses endogenous GH secretion.
The practical consequence: modified GRF 1-29 allows researchers to define a GH response window by the injection time. CJC-1295 with DAC provides near-continuous GH and IGF-1 elevation but removes that timing control.
Research protocol considerations
Naming inconsistency between the two forms is a recurring problem. "CJC-1295" without qualification has been applied to both forms in vendor catalogs, anti-doping literature, and published research summaries. The albumin-binding form is CJC-1295 with DAC, also written DAC:GRF. The form without the albumin linker is modified GRF 1-29, mod GRF 1-29, or CJC-1295 without DAC. These are not interchangeable in research protocols, and ordering or citing the wrong one is a meaningful experimental error.
Protocols combining a GHRH analog with a short-acting GH secretagogue such as ipamorelin typically use modified GRF 1-29. Both peptides have short half-lives measured in minutes to a couple of hours, so injections can be co-timed and GH responses measured relative to a specific time point. The dosing calculator on this site handles reconstitution math for both forms.
Protocols using CJC-1295 with DAC accept less frequent dosing at the cost of reduced temporal control. The washout period after the last injection extends 3 to 4 weeks before IGF-1 returns to pre-treatment baseline, based on the Teichman data. Any protocol requiring a clean pre-treatment baseline within a short timeframe needs to account for that tail. On the other hand, protocols studying sustained IGF-1 elevation over days with weekly dosing are well matched to what the published data shows.
Both forms are sold as lyophilized research peptides. Standard reconstitution with bacteriostatic water applies to both. See the CJC-1295 compound page for available vial sizes and current stock.
Storage in tropical research environments
Lyophilized CJC-1295 in either form tolerates short transit periods at ambient temperature, but long-term storage requires freezing. In Bali and other parts of Indonesia where ambient temperatures regularly exceed 30 degrees Celsius and relative humidity can reach 80 to 90%, even brief storage at room temperature accelerates peptide degradation. A dedicated laboratory freezer at -20 degrees Celsius or colder is necessary from the point of receipt.
After reconstitution with bacteriostatic water, both forms should be refrigerated at 2 to 8 degrees Celsius and used within 4 to 6 weeks. The maleimide-albumin bond on the DAC form does not change the storage requirements for the lyophilized powder.