CJC-1295 DAC

CJC-1295 DAC is a synthetic analog of growth hormone-releasing hormone (GHRH) consisting of the first 29 amino acids of native GHRH with four amino acid substitutions (Ala2, Gln8, Ala15, Leu27 replaced with D-Ala2, Gln8Asn, Ala15Leu, Met27Leu) to confer resistance to dipeptidyl peptidase IV (DPP-IV) cleavage, plus a Drug Affinity Complex (DAC) covalently attached via a maleimidopropionic acid-lysine linker. The total molecular weight of the DAC-conjugated peptide is approximately 3,647 Da. The DAC technology, developed by ConjuChem Biotechnologies, enables the peptide to form a stable covalent bond with serum albumin in vivo after injection.

The mechanism of action begins with the GHRH(1-29) core binding to GHRH receptors on anterior pituitary somatotrophs, activating the Gs/adenylyl cyclase/cAMP/PKA cascade to stimulate GH synthesis and secretion. What distinguishes CJC-1295 DAC from other GHRH analogs is the albumin-binding DAC moiety. Upon subcutaneous injection, the reactive maleimide group on the DAC linker forms a thioether bond with Cys34 on circulating serum albumin. Because human serum albumin has a half-life of approximately 19 days, the CJC-1295 DAC-albumin conjugate achieves a functional half-life of 6-8 days, dramatically extending the duration of GHRH receptor stimulation.

The pivotal pharmacokinetic and pharmacodynamic data come from a Phase 2 clinical trial published by Teichman et al. in the Journal of Clinical Endocrinology and Metabolism (2006, DOI: 10.1210/jc.2005-2664). In this study of 56 healthy adults aged 21-61, a single subcutaneous dose of CJC-1295 DAC (30, 60, or 125 mcg/kg) increased mean GH levels by 2-10 fold for 6 or more days. IGF-1 levels rose 1.5-3 fold and remained elevated for 9-11 days following a single injection. With repeated weekly dosing, IGF-1 levels achieved a sustained plateau without the peaks and troughs characteristic of shorter-acting secretagogues.

The sustained GH elevation pattern of CJC-1295 DAC differs fundamentally from the pulsatile pattern produced by non-DAC CJC-1295 (also called Mod GRF 1-29) or GHRP compounds. CJC-1295 DAC produces a continuous, elevated baseline of GH secretion rather than discrete pulses. This has practical implications: sustained elevation is more convenient (once-weekly dosing) and produces consistent IGF-1 levels, but it does not replicate the natural ultradian GH pulsatility that some researchers believe is important for optimal receptor sensitivity and downstream signaling.

Albumin binding was confirmed analytically using size-exclusion chromatography HPLC (SEC-HPLC), which showed the CJC-1295 DAC-albumin conjugate eluting at the expected molecular weight of approximately 70 kDa. The bioconjugation efficiency was greater than 90% within 15 minutes of incubation with human serum, confirming rapid and near-complete albumin binding in physiological conditions.

For reconstitution, lyophilized CJC-1295 DAC should be reconstituted with bacteriostatic water. The reconstituted solution should be stored at 2-8 degrees C and used within 21 days. Lyophilized powder should be stored at -20 degrees C for long-term stability. It is important to avoid vigorous shaking during reconstitution, as this can cause aggregation. The maleimide group on the DAC linker is sensitive to hydrolysis, so lyophilized storage is preferred over prolonged time in solution.

Safety data from the Phase 2 trial showed CJC-1295 DAC was generally well tolerated. The most common adverse events were injection site reactions (erythema, induration), transient facial flushing, and headache. No serious adverse events were attributed to the study drug. Dose-proportional increases in GH and IGF-1 were observed without signs of receptor desensitization over the study period. Glucose and insulin levels were monitored and showed no significant changes.

CJC-1295 DAC remains one of the most pharmacologically innovative GH secretagogues due to its albumin-binding approach. The DAC platform has been validated as a general strategy for extending peptide half-life, and CJC-1295 DAC represents the most clinically advanced application of this technology in the GH axis.