Author: Peptides.GG Research Team

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Ipamorelin vs GHRP-2 vs GHRP-6: Ghrelin-Mimetic Selectivity Compared

Ipamorelin, GHRP-2, and GHRP-6 are all synthetic peptides that belong to the same pharmacological family: the growth hormone secretagogues that act as agonists at the ghrelin receptor, formally the growth hormone secretagogue receptor type 1a (GHS-R1a). Because they share a receptor, they are often treated as interchangeable. The published research tells a more interesting story — they differ markedly in selectivity, meaning how cleanly each one acts on the growth-hormone axis versus the extent to which it also moves other pituitary and adrenal hormones in study subjects. This comparison walks through what each compound is at the molecular level and what cited studies actually measured.

The shared mechanism: GHS-R1a agonism

The starting point for all three is the same receptor. A foundational study cloned a G–protein-coupled receptor in the pituitary and hypothalamus and showed it to be the molecular target of the synthetic growth hormone secretagogues, including GHRP-6 (Howard et al., Science, 1996). That receptor — GHS-R1a — was later shown to be the receptor for the stomach hormone ghrelin, which is why these compounds are described as ghrelin mimetics: they activate the same receptor ghrelin does, despite sharing no sequence similarity with it.

What separates the members of the family is not the receptor they bind but the breadth of the hormonal response that binding produces. GHS-R1a is expressed in tissues beyond the GH-releasing cells of the pituitary, and the less selective members engage that broader distribution. The selectivity question is therefore the central one when these compounds are compared:

  • Does the compound stimulate growth hormone (GH) more or less in isolation?
  • Or does it also raise cortisol and ACTH (the adrenal axis) and prolactin?
  • Does it activate the appetite-regulating circuitry that ghrelin itself drives?

Ipamorelin: the selective end of the family

Ipamorelin is a synthetic pentapeptide — five amino acids — and it is the compound that defined the selective end of this class. The landmark characterization study described it as “the first selective growth hormone secretagogue” and tested its specificity directly (Raun et al., European Journal of Endocrinology, 1998). In that work, ipamorelin released GH in the research models studied, but, very notably, it did not raise ACTH or cortisol to levels significantly different from those seen with GHRH alone, and it showed no significant effect on prolactin — a separation that the authors reported remained intact across a wide range of exposures, far beyond the level needed to release GH.

That measured profile — GH-axis activity without a parallel rise in the adrenal-axis and prolactin hormones — is what “selective” means here, and it is the property that distinguishes ipamorelin from the older hexapeptides below. The comparison is purely about the hormonal fingerprint observed in research subjects; it is not a statement about any outcome in any individual.

GHRP-2 and GHRP-6: potent, but less selective

GHRP-2 (also known as pralmorelin) and GHRP-6 are both synthetic hexapeptides — six amino acids — and both are potent GH secretagogues at GHS-R1a. Where they diverge from ipamorelin is in the off-target hormonal activity that accompanies the GH response. A human comparison study measured GHRP-2 alongside hexarelin against GHRH, TRH, and human CRH, and reported that both peptides produced potent GH release while also raising ACTH and cortisol to a degree comparable to CRH, along with a measurable prolactin response (Arvat et al., Peptides, 1997). In other words, the published data placed GHRP-2 firmly in the less-selective group: strong on GH, but not isolated to it.

GHRP-6 was the earliest clinically studied member of the family and carries an additional dimension that distinguishes it within the group: a pronounced link to appetite circuitry. Because GHS-R1a is the ghrelin receptor, and ghrelin is an appetite-stimulating signal, the secretagogues can in principle engage feeding pathways — and GHRP-6 is the member where this was most clearly demonstrated. A study in rats found that central administration of GHRP-6 significantly stimulated food intake and activated brain appetite centers, including the hypothalamus and orexin-producing neurons (Lawrence et al., Endocrinology, 2002). That finding describes what the compound did in a research model; it is reported here as a selectivity characteristic, not as a benefit.

Where Hexarelin fits, and how to read the spectrum

Hexarelin (also called examorelin) is another synthetic hexapeptide in the same family, derived structurally from GHRP-6, and it is one of the most potent GH secretagogues of the group. In the same human comparison that examined GHRP-2, hexarelin was measured side by side and showed a similar pattern: potent GH release accompanied by ACTH, cortisol, and prolactin activity (Arvat et al., Peptides, 1997). It therefore sits with GHRP-2 and GHRP-6 on the potent-but-broad side of the spectrum rather than the selective side.

Laid out together, the family forms a clear gradient defined by selectivity rather than by raw GH potency:

  • Ipamorelin — pentapeptide; reported in study models to stimulate GH with minimal measured effect on cortisol, ACTH, and prolactin.
  • GHRP-2 — hexapeptide; potent GH secretagogue that also raised ACTH, cortisol, and prolactin in the cited human study.
  • GHRP-6 — hexapeptide; potent GH secretagogue additionally associated with appetite-center activation in a research model.
  • Hexarelin — hexapeptide; among the most potent of the group, with a measured off-target hormonal profile resembling GHRP-2’s.

Read across that list, the variable that separates these compounds is consistent: every one is a GHS-R1a agonist, but ipamorelin’s published profile shows the cleanest separation between GH-axis activity and the cortisol, prolactin, and appetite responses the hexapeptides carry.

Frequently asked questions

Are ipamorelin, GHRP-2, and GHRP-6 the same type of compound?

Yes, in the broad sense: all three are synthetic peptides that act as agonists at the ghrelin receptor, GHS-R1a, and are classed as growth hormone secretagogues. They differ in length — ipamorelin is a pentapeptide, GHRP-2 and GHRP-6 are hexapeptides — and, more importantly, in their measured selectivity.

What makes ipamorelin “selective” compared with GHRP-2 and GHRP-6?

In its characterization study, ipamorelin stimulated GH in the research models tested but did not significantly raise ACTH, cortisol, or prolactin relative to GHRH alone (Raun et al., 1998). GHRP-2 and GHRP-6, by contrast, were reported to raise the adrenal-axis hormones and prolactin alongside GH, which is what places them in the less-selective group.

What is the main difference between GHRP-2 and GHRP-6?

Both are potent hexapeptide secretagogues at the same receptor. In the published literature, GHRP-2 is generally described as the more potent GH releaser, while GHRP-6 is the member most clearly associated with appetite-center activation — central GHRP-6 stimulated food intake in a rat model (Lawrence et al., 2002).

Why are these called ghrelin mimetics?

GHS-R1a, the receptor all of these peptides bind, is the same receptor activated by the natural hormone ghrelin (Howard et al., 1996). The synthetic peptides reproduce ghrelin’s receptor activation despite having no sequence resemblance to ghrelin, which is why they are described as ghrelin mimetics.

Where does hexarelin sit relative to the others?

Hexarelin is a hexapeptide derived from GHRP-6 and is one of the most potent members of the family. In the same human study that measured GHRP-2, hexarelin showed a comparable off-target profile, with ACTH, cortisol, and prolactin activity accompanying GH release (Arvat et al., 1997), placing it on the potent-but-less-selective side of the spectrum.

Do all four bind the same receptor?

Yes. Ipamorelin, GHRP-2, GHRP-6, and hexarelin are all agonists at GHS-R1a, the growth hormone secretagogue receptor. The differences between them lie in the breadth of the hormonal response that receptor activation produced in the cited studies, not in the identity of the receptor itself.

References

  1. Howard AD, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996. PMID: 8688086.
  2. Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998. PMID: 9849822.
  3. Arvat E, et al. Effects of GHRP-2 and hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH and cortisol levels in man. Comparison with the effects of GHRH, TRH and hCRH. Peptides. 1997. PMID: 9285939.
  4. Lawrence CB, et al. Acute central ghrelin and GH secretagogues induce feeding and activate brain appetite centers. Endocrinology. 2002. PMID: 11751604.

For research use only. The products and materials discussed are intended for laboratory research purposes and are not for human or veterinary use, diagnosis, or treatment. This article describes the chemical structure and published pharmacological research of a compound and does not constitute a claim of any effect in any individual.

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SLU-PP-332: the Exercise-Mimetic ERR Agonist — Research Overview

One of the first questions people ask about SLU-PP-332 is whether it is a peptide — it is grouped on research-chemical price lists alongside peptides, so the assumption is reasonable. The answer is no. SLU-PP-332 is a small molecule, not a peptide: it has no amino acids and no peptide bonds. It is a synthetic agonist of the estrogen-related receptors (ERRα, ERRβ, and ERRγ), a family of nuclear receptors, and it is the compound most often referred to in the research literature as an “exercise mimetic.” This overview covers what SLU-PP-332 actually is at the molecular level, how its mechanism works, and what published studies have measured in laboratory models.

Is SLU-PP-332 a peptide? No — here is what it is

Peptides are short chains of amino acids linked by peptide bonds; that is the defining feature of the class. SLU-PP-332 has neither. It is a small organic molecule built around a naphthalene ring system linked to a benzamide-type group, with a molar mass on the order of a few hundred grams per mole — roughly an order of magnitude smaller than even a short peptide. In chemical databases it is catalogued as a discrete small-molecule entity, not as a sequence of residues.

The reason it travels in peptide company is functional, not structural. Like many research peptides, SLU-PP-332 is studied for its effects on metabolic signaling pathways, so vendors shelve it next to them. But mechanistically it belongs to a different category: it is a receptor agonist — a drug-like molecule that binds and switches on a nuclear receptor — rather than a peptide hormone or analog. The distinction matters, because the chemistry, the targets, and the published research are all different from those of the peptides it sits beside.

What “ERR agonist” means

The three estrogen-related receptors — ERRα, ERRβ, and ERRγ — are members of the nuclear receptor superfamily. Despite the name, they are not activated by estrogen; they are “orphan” receptors that share structural similarity with the classical estrogen receptor but operate on their own program. Their job, broadly, is transcriptional control of oxidative and mitochondrial metabolism: they sit at the hub of the gene network that governs how cells generate energy.

ERRα in particular has been characterized as a master regulator of mitochondrial function, working in partnership with the coactivator PGC-1α to drive expression of genes for mitochondrial biogenesis, oxidative phosphorylation, and fatty acid handling, as reviewed in the receptor-biology literature (Ranhotra, J Recept Signal Transduct Res, 2015). SLU-PP-332 is described as a pan-ERR agonist because it activates all three receptors, with its strongest activity reported at ERRα. In plain terms: it is a chemical key designed to fit the lock that endurance metabolism normally opens.

Why it is called an “exercise mimetic”

The phrase “exercise mimetic” is a research label, not a marketing promise, and it has a specific origin. Endurance exercise activates the same PGC-1α/ERR signaling axis that SLU-PP-332 targets pharmacologically. Investigators therefore asked whether switching that axis on with a small molecule would reproduce the molecular signature of endurance training in laboratory models — and that is exactly what the founding study set out to test.

In the compound’s primary characterization, researchers reported that SLU-PP-332 produced an ERRα-dependent acute aerobic-exercise transcriptional response and, in mice, increased type IIa oxidative skeletal-muscle fibers and measured changes in exercise capacity (Billon et al., ACS Chem Biol, 2023). It is important to read that precisely: these are outcomes measured in mouse and cell models, describing what the molecule did in those experiments — not effects established in humans, and not an outcome predicted for any individual.

What published research has measured

The literature on SLU-PP-332 is preclinical — conducted in animal and cell-based systems. The findings below are reported strictly as what each cited study measured in its research model:

  • Exercise-response signaling and muscle fiber type. The originating study measured an ERRα-dependent acute aerobic-exercise gene response and a shift toward oxidative muscle fibers, alongside changes in running performance, in mice (Billon et al., ACS Chem Biol, 2023).
  • Metabolic-syndrome model. A follow-up study in mouse models of metabolic syndrome measured increased energy expenditure and changes in insulin sensitivity and body composition after administration of the ERR agonist (Billon et al., J Pharmacol Exp Ther, 2024).
  • Cardiac metabolism. In a pressure-overload heart-failure model, pan-ERR agonists including SLU-PP-332 were measured to enhance cardiac fatty-acid metabolism and mitochondrial function and to improve cardiac measures in the treated animals (Xu et al., Circulation, 2024).
  • Underlying receptor biology. The transcriptional machinery these effects run through — ERRα’s control of mitochondrial and oxidative-metabolism genes — is documented in the broader receptor-biology literature (Ranhotra, J Recept Signal Transduct Res, 2015).

Across all of this work, the common thread is the oxidative-metabolism gene program: SLU-PP-332 engages ERR, and ERR turns on the mitochondrial and fatty-acid-metabolism transcripts. What the molecule does downstream of that has been characterized only in non-human research systems to date.

How it relates to the BAM-SLU blend

SLU-PP-332 also appears as a named component of the BAM-SLU Melt blend that contains it, where it is combined with other research compounds in one preparation. As with any blend, the SLU-PP-332 portion is the same small-molecule ERR agonist described here — the blend simply co-locates it with separate molecules that each carry their own chemistry and literature. For understanding what SLU-PP-332 itself is, the single-compound profile on this page is the relevant reference.

Frequently asked questions

Is SLU-PP-332 a peptide?

No. SLU-PP-332 is a small organic molecule — a synthetic agonist of the estrogen-related receptors (ERRα/β/γ). It contains no amino acids and no peptide bonds, so it is not a peptide despite often being listed alongside research peptides.

What does SLU-PP-332 do at the molecular level?

It binds and activates the estrogen-related receptors (ERRα, ERRβ, and ERRγ), with its strongest reported activity at ERRα. Those receptors are transcription factors that regulate genes for mitochondrial function and oxidative metabolism, which is why the compound is studied as a metabolic-pathway tool.

Why is SLU-PP-332 called an “exercise mimetic”?

Because it activates the same PGC-1α/ERR signaling axis that endurance exercise activates. In the originating mouse study it reproduced an acute aerobic-exercise transcriptional response and shifted muscle toward oxidative fibers (Billon et al., 2023). The term describes a molecular resemblance measured in research models, not a guaranteed effect in any individual.

Are SLU-PP-332 and the ERR receptors related to estrogen?

Only by name and structural similarity. The estrogen-related receptors are “orphan” nuclear receptors that resemble the classical estrogen receptor but are not activated by estrogen and instead govern energy-metabolism gene programs.

Has SLU-PP-332 been studied in humans?

The published research on SLU-PP-332 is preclinical — carried out in animal and cell-based models. The exercise-response, metabolic-syndrome, and cardiac-metabolism findings cited here were all measured in those research systems, not in human subjects.

What is SLU-PP-332 derived from?

It is a synthetic ERR agonist developed through medicinal-chemistry optimization of earlier ERR-active scaffolds. The result is a small-molecule pan-ERR agonist used as a research tool to probe estrogen-related-receptor signaling.

References

  1. Billon C, et al. Synthetic ERRα/β/γ Agonist Induces an ERRα-Dependent Acute Aerobic Exercise Response and Enhances Exercise Capacity. ACS Chemical Biology. 2023. PMID: 36988910.
  2. Billon C, et al. A Synthetic ERR Agonist Alleviates Metabolic Syndrome. Journal of Pharmacology and Experimental Therapeutics. 2024. PMID: 37739806.
  3. Xu W, et al. Novel Pan-ERR Agonists Ameliorate Heart Failure Through Enhancing Cardiac Fatty Acid Metabolism and Mitochondrial Function. Circulation. 2024. PMID: 37961903.
  4. Ranhotra HS. Estrogen-related receptor alpha and mitochondria: tale of the titans. Journal of Receptor and Signal Transduction Research. 2015. PMID: 25222219.

For research use only. The products and materials discussed are intended for laboratory research purposes and are not for human or veterinary use, diagnosis, or treatment. This article describes the chemical structure and published pharmacological research of a compound and does not constitute a claim of any effect in any individual.

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CJC-1295 With DAC vs Without DAC: What “DAC” Actually Means

If you’ve looked at CJC-1295 you’ve seen it listed two ways — “with DAC” and “without DAC” (or “no DAC”) — usually at noticeably different prices. The two are the same base peptide; the difference is a single chemical modification with the abbreviation DAC, and it changes one property dramatically: how long the molecule persists in circulation. This explainer covers what CJC-1295 is, what DAC actually is at the molecular level, and what the published research shows the modification does.

What CJC-1295 is

CJC-1295 is a synthetic analog of growth hormone–releasing hormone (GHRH). Specifically, it’s built on the first 29 amino acids of GHRH — the fragment known as GRF(1-29), which is the shortest segment that retains the parent hormone’s activity. Native GRF(1-29) is fragile: enzymes in plasma, principally dipeptidyl peptidase-IV (DPP-IV), cleave it within minutes.

CJC-1295 addresses that fragility with four amino acid substitutions in the GRF(1-29) backbone, each chosen to blunt a route of enzymatic breakdown. The result is a GHRH analog that resists degradation far better than the unmodified fragment. This stabilized backbone is common to both versions of CJC-1295 — the “with DAC” and “without DAC” forms share it. The DAC modification is something added on top.

What DAC is

DAC stands for Drug Affinity Complex. It is a small chemical group — a lysine linker carrying a maleimido (maleimide) function — attached to the peptide. The maleimide group is the active part: it reacts selectively with a free thiol (–SH), and the most abundant available thiol in the bloodstream is Cys34 of serum albumin, the body’s most plentiful circulating protein.

When the peptide encounters albumin, the maleimide forms a covalent bond to that cysteine, effectively tethering the small peptide to a large, long-lived carrier protein. That is the entire mechanism: DAC is a molecular hook that latches the peptide onto albumin.

What the tether changes: half-life

Albumin circulates for a long time and is too large to be filtered out by the kidneys quickly. By binding to it, the peptide inherits that longevity — it is shielded from the rapid renal clearance and enzymatic degradation that would otherwise remove a small peptide within minutes.

The published pharmacology quantifies the difference. In a clinical pharmacology study in healthy adults, a single administration of CJC-1295 with DAC produced elevations in circulating growth hormone and insulin-like growth factor I (IGF-I) that persisted for several days, with an estimated half-life on the order of about a week (Teichman et al., 2006). A companion study reported that the secretion remained pulsatile rather than flattening into a continuous release (Ionescu et al., 2006), and later work in an animal model characterized the same GH/IGF-1 axis activation (Sackmann-Sala et al., 2009).

The “without DAC” form lacks the maleimide group entirely, so it never binds albumin. It retains the stabilized GRF(1-29) backbone but clears on a much shorter timescale — minutes rather than days. This version is the one often labeled “Mod GRF 1-29” in the research literature; functionally, “CJC-1295 without DAC” and “Mod GRF 1-29” refer to the same modified fragment.

Where it sits in the GHRH-analog family

CJC-1295 is one of several research compounds built on the GHRH template, and the comparison clarifies what DAC contributes:

  • Sermorelin is GRF(1-29) itself — the unmodified 29-amino-acid fragment, short-acting.
  • CJC-1295 without DAC adds the four stabilizing substitutions to that fragment.
  • CJC-1295 with DAC adds, on top of those substitutions, the albumin-binding hook.
  • Tesamorelin is a separate stabilized GHRH analog with a different modification strategy.

Read down that list and DAC’s role is isolated cleanly: it is the one feature responsible for the multi-day persistence, layered onto an already-stabilized backbone.

Frequently asked questions

What does DAC stand for in peptides?

DAC stands for Drug Affinity Complex — a chemical group (a lysine linker with a maleimide function) added to a peptide so that it binds covalently to serum albumin in the bloodstream, which extends how long the peptide persists.

What is the difference between CJC-1295 with DAC and without DAC?

Both share the same stabilized GRF(1-29) backbone. The “with DAC” form carries an additional maleimide group that bonds to albumin, giving it a half-life measured in days; the “without DAC” form lacks that group and clears within minutes.

Is CJC-1295 without DAC the same as Mod GRF 1-29?

Yes. “CJC-1295 without DAC” and “Mod GRF 1-29” are two names for the same modified GRF(1-29) fragment.

How long does CJC-1295 with DAC last?

Published research in healthy adults estimated a half-life on the order of about a week, with measurable effects on GH and IGF-I persisting for several days after a single administration (Teichman et al., 2006).

How does CJC-1295 relate to sermorelin?

Sermorelin is the unmodified GRF(1-29) fragment. CJC-1295 is the same fragment with stabilizing substitutions, and — in the DAC version — an added albumin-binding group.

References

  1. Teichman SL, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology & Metabolism. 2006. PMID: 16352683.
  2. Ionescu M, et al. Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. Journal of Clinical Endocrinology & Metabolism. 2006. PMID: 17018654.
  3. Sackmann-Sala L, et al. Activation of the GH/IGF-1 axis by CJC-1295, a long-acting GHRH analog. Growth Hormone & IGF Research. 2009. PMID: 19386527.

For research use only. The products and materials discussed are intended for laboratory research purposes and are not for human or veterinary use, diagnosis, or treatment. This article describes the chemical structure and published pharmacological research of a compound and does not constitute a claim of any effect in any individual.