MOD-GRF (1-29)

Modified GRF 1-29 (Mod GRF, also called CJC-1295 without DAC or tetrasubstituted GRF 1-29) is a synthetic analog of the first 29 amino acids of growth hormone-releasing hormone (GHRH) with four amino acid substitutions designed to resist enzymatic degradation. Unlike CJC-1295 DAC, Mod GRF 1-29 lacks the Drug Affinity Complex and has a much shorter half-life (~30 minutes), producing acute GH pulses rather than sustained elevation. The four substitutions (positions 2, 8, 15, 27) replace DPP-4-susceptible residues with resistant analogs, extending the bioactive half-life from 5-7 minutes (native GHRH) to approximately 30 minutes. Mod GRF 1-29 is the most commonly used GHRH analog in combination with GH secretagogues (ipamorelin, GHRP-2, GHRP-6) for synergistic GH pulse stimulation.

Mod GRF 1-29 activates the GHRH receptor on pituitary somatotrophs, stimulating cAMP/PKA-mediated GH synthesis and secretion. Its shorter duration produces distinct GH pulses that mimic physiological secretion patterns. When combined with ghrelin mimetics, the complementary cAMP (GHRH) and IP3/calcium (ghrelin) pathways produce synergistic GH release 3-5 fold greater than either agent alone.

GH Axis Optimization Most commonly used as the GHRH component in combination protocols with ipamorelin or GHRP-2/6 for physiological GH pulse amplification. Body Composition Research shows improved lean mass, reduced fat mass, and enhanced recovery when used in combination secretagogue protocols. Sleep Enhancement Pre-bedtime administration amplifies the natural nocturnal GH pulse. Age-Related GH Decline Addresses somatopause by amplifying endogenous GH pulsatility.

GHRH-R/Gαs/cAMP/PKA/CREB for GH gene transcription and release. Synergy with GHS-R1a/Gq/PLC/calcium pathway when co-administered with secretagogues. GH/JAK2/STAT5/IGF-1 downstream axis.

Facial flushing and warmth (15-30 minutes post-injection). Mild headache. Water retention with sustained use. Injection site reactions. No significant cortisol or prolactin effects. Hypoglycemia rare.

Lyophilized powder stores at -20°C (18-24 months) or 2-8°C (3-6 months). Reconstitute with bacteriostatic water. Use within 21 days at 2-8°C. The four substitutions provide DPP-4 resistance but the short half-life (~30 minutes) necessitates timing injections for specific GH pulse goals.

Not FDA-approved. Research compound. WADA-prohibited under S2 (Growth Hormone Releasing Factors).