GHRP-2

Origin and Structure

GHRP-2, also known as pralmorelin and formerly as KP-102, is a synthetic hexapeptide with the sequence D-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH₂. It was developed by Kaken Pharmaceutical in Japan in the early 1990s as a second-generation successor to GHRP-6, engineered for greater potency at the ghrelin receptor and a cleaner non-GH profile — though, as it turned out, "cleaner" was only partially achieved.

Unlike most GHRPs, pralmorelin has an actual approved use: Kaken received Japanese regulatory approval in 2006 for intravenous pralmorelin as a diagnostic agent for adult GH deficiency. That approval remains in force in Japan but has not been pursued elsewhere, and the subcutaneous research-use product sold globally is not the same regulated product.

Mechanism of Action

GHRP-2 is an agonist at GHSR-1a, the ghrelin receptor, producing pulsatile GH release from pituitary somatotrophs. On a milligram-for-milligram basis it is the most potent of the classical GHRPs for GH release, typically producing higher peak GH than GHRP-6 or hexarelin at equivalent doses and with shorter duration of action.

The distinctive feature of GHRP-2 relative to ipamorelin is the cortisol and prolactin response. At GH-effective doses, pralmorelin produces measurable increases in both hormones — smaller than with GHRP-6 but consistently larger than with ipamorelin. Appetite stimulation is modest, noticeably less than with GHRP-6, because the central ghrelin-receptor activation profile favors somatotroph release over arcuate orexigenic signaling.

Clinical Evidence

The clinical evidence base for GHRP-2 is substantially larger than for most other GHRPs because of the Japanese diagnostic program:

• GH stimulation testing. Multicenter trials in Japan validated IV pralmorelin as a GH stimulation test, with sensitivity and specificity comparable to insulin-tolerance testing and substantially better tolerability.
• Short-stature pediatric trials. Phase 2 work in GH-deficient children demonstrated growth-velocity increases, though the program did not advance to approval in that indication.
• Healthy-volunteer pharmacology. Pharmacodynamic studies have characterized the GH, cortisol, prolactin, and IGF-1 responses in detail — the best-characterized GHRP after ipamorelin.

Outside Japan, no regulator has approved GHRP-2 for any indication. Development interest in the West shifted toward non-peptide oral ghrelin agonists such as macimorelin, which offer the same diagnostic capability with easier administration.

Practical Considerations

Research-use subcutaneous protocols are typically 100-300 mcg per injection, two to three times daily, dosed fasted. The short half-life (roughly 30 minutes) means that plasma levels fall rapidly between doses, which is considered desirable for preserving pulsatile GH release and minimizing receptor desensitization. GHRP-2 is commonly paired with a GHRH analogue such as Modified GRF (1-29) or sermorelin to exploit the GHRH-plus-GHRP synergy.

Safety and Regulatory Status

Commonly reported side effects include transient flushing, mild injection-site reactions, headache, and modest appetite increase. Cortisol elevations are the most clinically relevant concern with chronic dosing — sustained cortisol elevation can blunt the body-composition benefits the peptide is often used to achieve, which is part of the reason many protocols rotate toward cleaner GHRPs like ipamorelin for longer cycles.

GHRP-2 is not FDA-approved. It is on the WADA prohibited list at all times (class S2, Peptide Hormones). Western supply is almost entirely through research-chemical vendors. For a broader comparison across the GHRP class including stacking logic, see our GHRH-plus-GHRP explainer.