Ghrelin-receptor research peptide (CHEMBL2163348 / HAYK)
A tiny four-amino-acid lab compound that weakly binds the hunger-hormone receptor; used only as a research tool, not a drug or supplement.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
CHEMBL2163348 is a short four-amino-acid research peptide (sequence HAYK) characterised as a low-affinity ligand of the growth hormone secretagogue receptor GHSR-1a — the same receptor that the natural "hunger hormone" ghrelin and the synthetic growth-hormone-releasing peptide series (GHRP-2, GHRP-6, hexarelin, ipamorelin) act on. It was reported in the ChEMBL bioactivity database with an IC50 of 771 nM against GHSR, which places it in the weak-binder range rather than the drug-like range. It is a medicinal-chemistry tool compound, not a therapeutic, supplement, or compounded peptide.
What it does
In a binding assay against GHSR-1a, CHEMBL2163348 competes with a reference ghrelin-pathway ligand at an IC50 of 771 nM (ChEMBL CHEMBL2163348). That is roughly three orders of magnitude weaker than the high-potency synthetic GHSR agonists in this chemical series, and the compound is best understood as a structure-activity data point in the broader effort to map which short peptide motifs retain GHSR engagement and which lose it.
Evidence
- Human: No human studies. This is a bench-only research compound with a single bioactivity datapoint.
- In vitro: IC50 = 771 nM at GHSR-1a, reported in the ChEMBL database under accession CHEMBL2163348. The surrounding chemistry programme reported azapeptide analogs of GHRP-6 designed to reduce GHSR-1a affinity in favour of the CD36 receptor (Proulx and colleagues, Journal of Medicinal Chemistry, 2012).
- Animal: No animal data.
Related peptides
CHEMBL2163348 sits within the broader GHSR-1a / growth hormone secretagogue receptor pharmacology family. Receptor-system context — the endogenous ligand ghrelin and the synthetic GHRP series (GHRP-2, GHRP-6, hexarelin, ipamorelin, MK-677) — is the relevant frame for interpreting weak GHSR binders of this kind, but no specific platform cards are linked here because no verified cross-references were available in the dossier.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does the tiny HAYK peptide grip the ghrelin receptor through a different part of the receptor than the natural hunger hormone does?
If true, it could point to a simpler class of molecules that dial the hunger signal up or down, without needing the chemically awkward fatty modifications that make ghrelin-based drugs hard to manufacture.
Is it the positively charged lysine at the end of HAYK that is mainly responsible for sticking to the hunger receptor?
If a single amino acid turns out to be the key contact, chemists could use that knowledge to design very small, stable molecules that mimic or block ghrelin signaling, potentially leading to new treatments for appetite disorders or growth hormone deficiencies.
Does HAYK actually bind the fat-scavenging receptor CD36, relevant to heart disease, more than it binds the hunger receptor?
If HAYK turns out to favor CD36, it could serve as a starting point for new drugs targeting atherosclerosis or liver fat disease, conditions that affect hundreds of millions of people with limited treatment options beyond statins and lifestyle changes.
Would swapping the second building block of HAYK for a rigid, enzyme-resistant one make the peptide last longer and bind more tightly?
If this modification works, it could transform an otherwise throwaway research fragment into a real drug candidate, giving researchers a stable, easy-to-synthesize scaffold for developing appetite or cardiovascular medicines.
Does HAYK reduce the steady hum of hunger signaling from the ghrelin receptor even when no ghrelin is present?
If true, HAYK-inspired compounds could lower baseline appetite without flooding the body with a full ghrelin signal, offering a gentler approach to obesity or metabolic disease management for patients who currently have few well-tolerated options.
▸full evidence table1 metrics
| metric | value | tool |
|---|---|---|
| IC50 | 771 nM | GPCRDB/ChEMBL |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.358 | global PDE — lower = better |
| disorder | NaN | fraction disordered |
▸3-letter notation
▸recipeboltz-2 1.0
| parameter | value |
|---|---|
| model | boltz-2 1.0 |
| weights | — |
| hardware | nvidia_nim_api |
| mlx version | — |
| python | — |
| random seed | — |
| msa strategy | none |
| diffusion samples | 1 |
| runtime | — |
| predicted by | mlx@peptide |
| predicted at | 2026-04-24 |
▸citationbibtex
@peptide{pep10342,
sequence = {HAYK},
target = {ghsr},
author = {peptidemodel},
year = {2026},
status = {bioassayed}
}