CJC-1295 DAC Peptide

In preclinical and early clinical studies, CJC-1295 DAC demonstrated dose-dependent increases in GH secretion. A 2006 study by Teichman et al. found that a single subcutaneous injection of CJC-1295 resulted in sustained GH elevation for 6+ days, with IGF-1 levels remaining elevated for up to 14 days.

The study reported mean GH levels increased 2-10 fold above baseline, with peak IGF-1 increases of 1.5-3 fold depending on dosage. The compound maintained the natural pulsatile pattern of GH secretion rather than producing a continuous, non-physiological elevation.

The landmark Phase 1 study by Teichman and colleagues (2006) established the pharmacokinetic profile of CJC-1295 DAC (then designated CJC-1295) in healthy human volunteers, providing the foundational data that distinguishes this analog from native GHRH and modified GHRH(1-29) peptides such as Sermorelin and tesamorelin.

Study Design:

• Randomized, double-blind, placebo-controlled, ascending single-dose trial
• Subjects: 21 healthy adult volunteers
• Doses: 30, 60, 125, and 250 μg/kg subcutaneous CJC-1295 DAC
• Endpoints: serum CJC-1295 concentration, GH, and IGF-1 over 28 days post-dose

Key Pharmacokinetic Findings:

• Mean terminal half-life of ~5.8 to 8.1 days, vastly exceeding the <30-minute half-life of native GHRH
• Detectable serum levels persisted up to 28 days at higher doses
• Mean GH levels increased 2-10 fold and remained elevated for 6 days
• IGF-1 levels increased 1.5-3 fold above baseline and remained elevated for 9-11 days post single dose
• No significant change in prolactin, cortisol, or other pituitary hormones, confirming GHRH-receptor selectivity

The extended half-life is mechanistically attributable to the maleimidopropionyl-lysine DAC moiety, which forms a covalent thioether bond with cysteine-34 of circulating serum albumin. This bioconjugation strategy shields the peptide from dipeptidyl peptidase-IV (DPP-IV) cleavage and renal filtration, properties that severely limit native GHRH and unmodified GHRH(1-29) (Sermorelin), which has a half-life of only 11-12 minutes. A subsequent multiple-dose study (Teichman et al., 2006) demonstrated that weekly or bi-weekly dosing produced sustained 1.5- to 3-fold elevations in IGF-1 over multi-week dosing periods, confirming that DAC enables practical chronic-dose research paradigms not feasible with shorter-acting GHRH analogs.

A pharmacological comparison study by Ionescu and Frohman (2006) directly evaluated CJC-1295 DAC against native GHRH and exercise-induced GH stimulation in healthy male volunteers, characterizing how DAC-mediated half-life extension alters the GH secretory profile.

Study Design:

• Crossover design in healthy adult males
• Compared single-dose CJC-1295 DAC (60 μg/kg SC) with intravenous GHRH (1 μg/kg) and acute exercise stimulus
• Frequent serum sampling for GH pulse analysis over 7 days

Key Findings:

• CJC-1295 DAC produced a sustained 7.5-fold increase in mean GH levels at 24 hours and a 2-fold increase persisting at day 7
• Crucially, pulsatile GH secretion was preserved rather than collapsed into a tonic plateau — pulse amplitude increased while pulse frequency remained physiologic
• GH trough levels rose, but pulses remained discrete, contrasting with concerns of pituitary desensitization
• IGF-1 elevation was sustained for >6 days from a single subcutaneous dose

Comparison Summary:

• Native GHRH: half-life <10 minutes, requires continuous infusion or repeated bolus dosing
• Sermorelin (GHRH 1-29): half-life ~12 minutes, daily dosing required
• CJC-1295 (no DAC, modified GHRH 1-29): half-life ~30 minutes — improved DPP-IV resistance only
• CJC-1295 DAC: half-life ~8 days, weekly dosing feasible, preserves pulsatility

These data established CJC-1295 DAC as a research tool uniquely suited to investigate chronic GHRH-receptor agonism in long-duration animal and clinical studies, where short-acting analogs are pharmacokinetically impractical. Subsequent rodent and primate work has utilized this profile to study sustained somatotroph stimulation, IGF-1-mediated tissue effects, and feedback dynamics within the GH/IGF-1 axis.

Alba and colleagues (2006) used the GHRH knockout (GHRH-KO) mouse model to evaluate whether CJC-1295 DAC could functionally substitute for endogenous GHRH and restore normal somatic growth — a stringent test of GHRH-receptor agonism in vivo.

Study Design:

• Subjects: GHRH-KO mice (homozygous null for the GHRH gene), which exhibit severe pituitary somatotroph hypoplasia and dwarfism
• Intervention: once-daily subcutaneous CJC-1295 DAC vs. saline vehicle from weaning through adulthood
• Outcome measures: body weight, body length, organ weights, pituitary GH content, serum IGF-1

Key Results:

• Body weight in CJC-1295 DAC-treated GHRH-KO mice was restored to levels not significantly different from wild-type littermates
• Body length normalized after sustained dosing
• Pituitary GH content and somatotroph population recovered toward wild-type levels, demonstrating trophic action on somatotroph proliferation
• Serum IGF-1 normalized to wild-type range
• Once-daily dosing was sufficient — consistent with the multi-day pharmacokinetic profile

This study is mechanistically significant because it confirms that CJC-1295 DAC engages the pituitary GHRH receptor (GHRHR) with sufficient potency and duration to fully replicate endogenous GHRH function — including the trophic effects on somatotroph mass that distinguish GHRH-axis agonists from direct GH replacement. The model also validates CJC-1295 DAC as a research tool for investigating GHRH-axis development, somatotroph biology, and long-term IGF-1-mediated tissue effects in genetically defined backgrounds. Together with the human PK/PD data, these preclinical findings inform the broader use of CJC-1295 DAC in laboratory studies of growth hormone insufficiency models, aging-related somatopause, and tissue regeneration paradigms.