Tag: Growth hormone releasing peptide / ghrelin receptor agonist

GHRP-2

Plain-language summaryIntrigue 60 / 100

GHRP-2 is a synthetic peptide that activates the ghrelin receptor and triggers growth hormone release. It is a stronger growth hormone releaser than ipamorelin but also raises cortisol and prolactin slightly. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

39/100

Solid second-generation GHRP with clinical validation but largely outpaced by cleaner, more selective successors

Look, GHRP-2 is a legitimate compound with a real mechanism and honest clinical use. It’s approved in Japan as a GH stimulation test agent, which is more than most peptides in this library can claim. GHS-R1a agonism is well-characterized, the synergy with GHRH analogs is reproducible across labs, and the pharmacokinetics are understood well enough to design clean experiments around it. For basic GH-axis work, it does exactly what it says.

But here’s the thing: GHRP-2 occupies an awkward middle position in its own class. It came after GHRP-6 and before ipamorelin, and that timeline shows. GHRP-6 still has a niche because its off-target ghrelin receptor effects drive appetite stimulation, which some investigators actually want to study. Ipamorelin has the opposite advantage: far cleaner selectivity, minimal cortisol and prolactin bleed, and a sharper tool for anyone trying to isolate GH-axis pharmacology from the noise. GHRP-2 sits between those two, offering stronger GH output than GHRP-6 but less receptor fidelity than ipamorelin. In practice, most researchers who care about clean GH secretagogue biology reach for ipamorelin. Those who want ghrelin receptor pleiotropy study GHRP-6 or ghrelin itself. GHRP-2 doesnt own either lane.

On the evidence side, theres real multi-lab data, replicated GH stimulation studies, and the diagnostic clinical use that most peptides lack. We’re not calling this single-lab-only territory. The problem is that the evidence base is mature in the wrong direction: most of it is decades old, and recent literature on GHRP-2 specifically is thin. When researchers publish GH secretagogue work now, theyre comparing newer molecules, and GHRP-2 mostly appears as a historical comparator or a positive control.

We think bench value is real but unexceptional. GHRP-2 is a serviceable probe for GHS-R1a biology, and it has the advantage of being widely sourced with decent quality consistency. But its not the tool you pick when you want to ask a sharp, specific question about ghrelin receptor pharmacology. Ipamorelin gives you better receptor selectivity for those experiments. GHRP-2 gives you more raw GH output, which matters if GH pulse amplitude is itself the variable of interest rather than a confound.

Honestly, if you’re building a GHRP-focused program from scratch today, GHRP-2 is probably not your first choice. It earns its place in reference panels and in labs that already have it on the shelf, but its not where the interesting new biology in this space is happening. The overall score reflects a compound with genuine historical significance and solid evidence, that is nonetheless unlikely to surprise a serious investigator or open a research question they couldn’t otherwise pursue.

Novelty

28

Mechanism promise

42

In-category differentiation

28

Evidence quality

52

Translational signal

48

Research bench value

48

Rationale GHRP-2 sits in the middle of the GHRP class: more efficacious than GHRP-6 on GH output, less selective than ipamorelin, and carrying 1990s-era origins that put it squarely in the established-mature bracket. Its clinical diagnostic use in Japan gives it real translational standing, but that distinction does little to differentiate it from ipamorelin, which is the GHRP most serious GH-axis investigators now reach for first.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Growth hormone releasing peptide / ghrelin receptor agonist

A second-generation hexapeptide ghrelin receptor agonist for growth hormone release, characterized by stronger GH stimulation than GHRP-6 with reduced cortisol/prolactin elevation.

Abstract

GHRP-2 (Pralmorelin; D-Ala-D-2-Naphthyl-Ala-Ala-Trp-D-Phe-Lys-NH2; CAS 158861-67-7; molecular formula C45H55N9O6; molecular weight 817.97) is a second-generation growth hormone releasing peptide developed in the 1990s as a synthetic ghrelin receptor (GHS-R1a) agonist. The compound stimulates pituitary GH release through a mechanism distinct from GHRH (different receptor; synergistic when combined with GHRH or GHRH analogs). GHRP-2 produces robust GH pulses approximately 2 to 5 times baseline with parenteral administration. Pharmacokinetics: plasma half-life 15 to 60 minutes; subcutaneous and intravenous routes; oral bioavailability poor due to peptidase degradation. The compound is used clinically in Japan as a GH stimulation test. Compared with GHRP-6, GHRP-2 produces stronger GH release with reduced cortisol and prolactin elevation. Compared with ipamorelin, GHRP-2 has higher GH efficacy but less receptor selectivity. Research-grade doses are typically 100 to 300 micrograms subcutaneously per administration, often combined with a GHRH analog.

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The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026
GHRP-6

Plain-language summaryIntrigue 58 / 100

GHRP-6 is the original growth hormone releasing peptide and a strong appetite stimulant (because it activates the ghrelin receptor that controls hunger). It produces robust growth hormone release but with the most pronounced cortisol and prolactin elevation among the GHRPs. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

32/100

First-generation GHRP largely superseded by cleaner alternatives, appetite signal is interesting but not enough

Look, GHRP-6 has a story, but its best chapters were written in the 1990s. It’s a first-generation hexapeptide, one of the original compounds that validated the ghrelin receptor as a viable target for GH secretagogues, and for that it deserves some historical respect. But history isn’t a research rationale.

The mechanism is exactly what you’d expect from something this old: GHSR1a agonism, pulsatile GH release, appetite stimulation through the ghrelin pathway. Solid, well-understood, extensively mapped. The problem is it also drags cortisol and prolactin up in a way that the later-generation GHRPs largely avoid. Ipamorelin came along specifically to solve that problem. Researchers moved on. The cortisol/prolactin elevation isn’t just a safety nuisance in animal models, it complicates any experiment where you’re trying to isolate GH-axis effects. That’s a real methodological liability.

Differentiation is where GHRP-6 genuinely suffers. We think of it mostly as a less clean GHRP-2 or a more side-effect-prone ipamorelin. There’s almost no scenario where it’s the first choice over those two unless you’re specifically studying appetite modulation via ghrelin, which is the one corner where GHRP-6 has a distinctive profile. The appetite stimulation is pronounced and reproducible, and if thats the actual research question, it becomes a relevant tool. Cachexia or sarcopenia models where caloric intake is the outcome variable, for instance. But that is a narrow carve-out, not a broad program.

Evidence quality is moderate. Decades of multi-lab preclinical data exist, and there’s some human work from the 1990s and early 2000s on GH secretion dynamics. But clinical development stalled out, and theres essentially no modern RCT infrastructure behind it. The human translational story is capped by that abandoned trajectory. We’re not looking at a compound with fresh phase 2 data or a revived indication pipeline. What we’re looking at is a reference compound for ghrelin receptor agonism that has been functionally replaced in most experimental designs.

The bench value survives in one specific context: if you’re running a comparative GHRP study and need a first-generation reference point, or if appetite/orexigenic signaling is central to your model, GHRP-6 earns its spot. Outside that, we’d suggest the investigator ask whether ipamorelin or GHRP-2 actually answers their question better before reaching for this one. Most of the time, the answer is yes. That’s the honest position here: not a bad compound, just not the right compound for most research programs that have access to better options.

Novelty

22

Mechanism promise

35

In-category differentiation

22

Evidence quality

45

Translational signal

35

Research bench value

38

Rationale GHRP-6 scores low on novelty and differentiation because it predates and is functionally inferior to later GHRPs on most axes; the cortisol/prolactin liability killed its clinical trajectory and ipamorelin has taken its place as the reference clean GHRP. The appetite/ghrelin angle is genuinely distinctive and gives it marginal bench value, but the evidence base is messy and the compound just isn’t a priority for any serious program in 2025.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Growth hormone releasing peptide / ghrelin receptor agonist

A first-generation hexapeptide ghrelin receptor agonist with prominent appetite stimulation, often used as a research-grade alternative to ipamorelin.

Abstract

GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2; CAS 87616-84-0; molecular formula C46H56N12O6; molecular weight 873.02) is a first-generation hexapeptide ghrelin receptor agonist. The compound stimulates GH release with kinetics similar to GHRP-2 but produces more pronounced cortisol and prolactin elevation, which has limited its clinical development. GHRP-6 also produces marked appetite stimulation through ghrelin pathway activation, an effect that distinguishes it from later GHRPs and that may be either useful (cachexia, sarcopenia adjunct) or unwanted (weight management contexts) depending on the application. Pharmacokinetics: plasma half-life 15 to 60 minutes; parenteral administration only. Research-grade doses are typically 100 to 300 micrograms subcutaneously per administration.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

KDC-MN-077Open in new tab →

Download PDF →

FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

May 9, 2026

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Tag: Growth hormone releasing peptide / ghrelin receptor agonist

GHRP-2

Abstract

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GHRP-6

Abstract

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