CJC-1295 (no DAC): research overview

Modified GRF (1-29) — also marketed as CJC-1295 without DAC — is a stabilized but short-acting GHRH analog that activates the same GHRH receptor as native GHRH. The pairing rationale with L-arginine is therefore identical to that for GHRH itself: arginine suppresses hypothalamic somatostatin tone (Alba-Roth 1988), and in human trials the GHRH + arginine combination is a more potent and reproducible GH stimulator than either input alone (Ghigo 1990; Ghigo 2001). Because the no-DAC form produces a short, pulse-like GHRH stimulus, the somatostatin-suppression window opened by arginine maps cleanly onto the GH spike — at least in the secretagogue-class trials. No CJC-1295 no DAC × arginine clinical trial has been published.

The no-DAC form is most often discussed in research practice paired with a ghrelin-receptor agonist (commonly ipamorelin) because the two together reproduce the dual-input GH-control system. Hataya et al. documented in healthy men that low-dose ghrelin combined with GHRH drove GH release greater than the sum of individual stimuli. Cunha and Mayo mapped the receptor-level mechanism: GHRH-R and GHS-R co-activation roughly doubles the GHRH-only cAMP response. Fintini et al. extended this to in vivo growth endpoints in GHRH-knockout mice, where a GHRH analog plus a ghrelin-receptor agonist outperformed monotherapy. Modified GRF (1-29)'s short half-life makes it the GHRH-class peptide most often co-administered as a true pulse alongside a ghrelin-arm stimulus.

Short-acting GHRH analogs such as modified GRF (1-29) deliver discrete pulses on top of an endogenous nocturnal pulse architecture that is locked to sleep onset and slow-wave sleep. Van Cauter and Plat identify GHRH as the principal driver of the SWS-coupled GH pulse and document the parallel age-related decline of SWS and 24-h GH secretion. Born et al. showed that delaying sleep onset shifts the GH pulse rather than abolishing it, confirming the timing dependence. Behavioral cofactors that preserve SWS therefore shape the baseline on which any short-acting GHRH-class peptide acts. Pre-sleep dosing windows are reported in the GH-axis literature, though no specific no-DAC sleep-timing RCT is published.

Glycine has been studied as an amino-acid GH stimulus in its own right. Kasai et al. reported that intravenous glycine (4, 8, or 12 g over 15–30 minutes) produced dose-dependent rises in serum GH in healthy adults without altering prolactin. The Arwert randomized trial of an oral glycine–glutamine–niacin mixture reported a roughly 70% rise in serum GH in middle-aged and elderly subjects after three weeks. The mechanism is incompletely mapped but is consistent with hypothalamic somatostatin modulation rather than direct pituitary action — placing glycine on the same arm of the dual-input system that a short-acting GHRH analog like modified GRF (1-29) targets.