GHRP-2 (Pralmorelin)

GHRP-2 (D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH₂, also known as pralmorelin or KP-102) is a synthetic hexapeptide growth hormone secretagogue that acts as a potent agonist at the ghrelin receptor (GHS-R1a). Its structure incorporates two D-amino acids and a 2-naphthylalanine residue — modifications that confer resistance to enzymatic degradation and high receptor-binding affinity while remaining chemically distinct from both natural ghrelin and earlier GHRP family members.

At the pituitary somatotroph level, GHRP-2 activates GHS-R1a via Gαq/11 → phospholipase C → IP3-mediated calcium mobilization, triggering exocytosis of pre-synthesized growth hormone vesicles. Simultaneously, it antagonizes somatostatin tone at the pituitary, reducing the inhibitory brake on GH release — a dual mechanism shared across the GHRP family. The resulting GH pulse is dose-dependent, with peak serum GH occurring approximately 30–45 minutes after subcutaneous administration and returning to baseline within 2–3 hours.

Compared to GHRP-6, GHRP-2 demonstrates approximately 2–3× greater GH-releasing potency on a molar basis with significantly less appetite stimulation — a clinically meaningful difference attributed to its D-2-Nal substitution at position 2, which alters the balance of GHS-R1a signaling versus off-target effects on hypothalamic feeding circuits. However, unlike Ipamorelin (the most selective GHRP), GHRP-2 retains measurable — though modest — effects on cortisol and prolactin at higher doses, making dose-response characterization an important research variable.

GHRP-2 was developed by Kaken Pharmaceutical (Japan) in the 1990s as part of the broader pharmaceutical effort to create orally active growth hormone secretagogues. The development code KP-102 reflects its Kaken Pharmaceutical origin. Early clinical studies in children with growth hormone deficiency demonstrated robust GH release with a favorable safety profile, and the compound advanced through Phase 2 trials in Japan.

Like many GHRPs, pralmorelin was ultimately not commercialized as a therapeutic — a fate shared by most synthetic ghrelin-mimetics as the pharmaceutical industry shifted toward recombinant human growth hormone and, later, GHRH analogs. However, extensive preclinical and clinical characterization left a rich published record, and GHRP-2 has become one of the most widely used research tools for studying pulsatile GH release and GHS-R1a signaling. Its well-characterized pharmacology, broad availability from independent suppliers, and intermediate selectivity profile between GHRP-6 and Ipamorelin make it a useful comparative tool in growth hormone axis research.

Store lyophilized GHRP-2 at -20°C in a light-protected, desiccated container. The D-amino acid and D-2-Nal residues provide significant resistance to standard peptidases; stability exceeds 24 months under optimal conditions. Brief room-temperature handling during reconstitution does not significantly degrade the peptide.

After reconstitution with bacteriostatic water, GHRP-2 should be refrigerated at 2–8°C and used within 21–28 days. The peptide solution should remain clear and colorless; any turbidity or discoloration indicates degradation. GHRP-2 is compatible with CJC-1295 no DAC in the same syringe for combined GHRH/GHRP research protocols — no interaction or aggregation has been reported. Do not freeze reconstituted solutions.