Minigastrin I: gut-signaling hormone fragment used in cancer research
A small piece of the gut hormone gastrin, first found in a rare pancreatic tumor; it triggers gallbladder and digestive signals and is used only as a lab research tool, mainly to develop scans that light up certain cancers.
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
Minigastrin I is a 13-amino-acid fragment of the human hormone gastrin, the gut peptide that signals the stomach to make acid. It was first purified in the 1970s from a rare pancreatic tumor (a gastrinoma) and corresponds to residues 5–17 of "little gastrin" (G17). In the body, the native peptide carries a C-terminal amide cap (Phe-NH₂) and exists in two forms — type I with an unmodified tyrosine and type II with a sulfated tyrosine — that occur in tumor tissue at roughly a 2:1 ratio (Gregory and Tracy, Gut, 1974). Today minigastrin is mainly studied as a starting scaffold for radiolabeled tracers that target the cholecystokinin-2 receptor (CCK2R) on certain cancers.
History
The peptide was isolated in 1974 by R. A. Gregory and Hilda Tracy at the University of Liverpool from Zollinger-Ellison gastrinoma tumor tissue, alongside the longer gastrins from the same source (Gregory and Tracy, Gut, 1974). In the same issue of Gut, Debas, Walsh, and Grossman reported its in-vivo profile: pure human 13-residue minigastrin (HG-13-I) cleared from blood with a half-life of 1.8 minutes and was less than half as potent as 17-residue gastrin on a molar basis for stimulating gastric acid secretion in dogs (Debas, Walsh, and Grossman, Gut, 1974). After the discovery of the cholecystokinin-2 (gastrin/CCK-B) receptor and its expression on several human tumors, minigastrin re-emerged in the 2000s as a lead scaffold for receptor-targeted nuclear medicine (Roosenburg and colleagues, Amino Acids, 2011).
What it does
Like full-length gastrin, minigastrin binds and activates the cholecystokinin-2 receptor (CCK2R), a G-protein-coupled receptor expressed on stomach parietal cells, enterochromaffin-like cells, and a subset of brain and pancreatic cells. Receptor activation by gastrin peptides triggers gastric acid release and trophic signaling in gastrointestinal mucosa. The receptor-binding job is done by the conserved C-terminal tetrapeptide Trp-Met-Asp-Phe-NH₂ that all gastrin and cholecystokinin peptides share; the rest of the minigastrin sequence — including the run of five glutamates near the N-terminus — modulates affinity, charge, and pharmacokinetics rather than initial receptor recognition (Roosenburg and colleagues, Amino Acids, 2011).
Mechanism
The stored sequence LEEEEEAYGWMDF is the bare 13-residue backbone; the biologically active peptide is the C-terminally amidated form (LEEEEEAYGWMDF-NH₂), and the "minigastrin II" variant additionally carries a sulfate on the single tyrosine. The amide cap and the C-terminal Trp-Met-Asp-Phe-NH₂ pharmacophore together drive CCK2R engagement (Roosenburg and colleagues, Amino Acids, 2011). Tyrosine sulfation differentiates the two natural variants: minigastrin I (non-sulfated) binds CCK2R selectively, while sulfated forms engage both CCK1 (CCKAR) and CCK2 receptors — a structural distinction exploited in tracer design, where non-sulfated minigastrin analogs are preferred for selective CCK2R imaging. The pentaglutamate stretch (Glu5–Glu9) is a major contributor to the very high anionic charge of the molecule and has been linked to off-target renal retention of radiolabeled minigastrin analogs, motivating engineered variants with reduced Glu content or substituted residues (Roosenburg and colleagues, Amino Acids, 2011).
Evidence
- Human: No therapeutic clinical trials of the native minigastrin I peptide. Clinical work centers on radiolabeled minigastrin analogs (rather than the parent peptide) as imaging agents and targeted radiotherapies for CCK2R-expressing tumors, primarily medullary thyroid carcinoma and small cell lung cancer (Roosenburg and colleagues, Amino Acids, 2011).
- Animal: Pure human 13-residue minigastrin (HG-13-I) was characterized in dogs in 1974, showing a plasma half-life of 1.8 minutes and a potency ratio of ~0.4 (95% CI 0.2–0.6) relative to 17-residue gastrin for acid secretion (Debas, Walsh, and Grossman, Gut, 1974). Preclinical work continues on minigastrin-based tracers: a 2025 study reported that dimeric CCK2R-targeting radiotheranostic tracers, combined with mTOR inhibition, produced enhanced antitumor effects in CCK2R-positive tumor models (Bian and colleagues, Theranostics, 2025).
- In vitro: Minigastrin and its analogs bind CCK2R with nanomolar affinity; the conserved C-terminal Trp-Met-Asp-Phe-NH₂ tetrapeptide is the receptor-binding pharmacophore, and non-sulfated forms are CCK2R-selective whereas sulfated forms also engage CCK1R (Roosenburg and colleagues, Amino Acids, 2011).
Known effects
- Gastric acid secretion — Mechanistic; demonstrated for the native peptide in dogs (Debas, Walsh, and Grossman, Gut, 1974).
- CCK2R-targeted tumor imaging (as radiolabeled analog) — Preclinical and early clinical, with medullary thyroid carcinoma as the principal indication studied; native minigastrin is the scaffold, not the clinical agent (Roosenburg and colleagues, Amino Acids, 2011).
- Radiotheranostic delivery to CCK2R+ tumors (as engineered dimer) — Preclinical (Bian and colleagues, Theranostics, 2025).
Safety signals
Native minigastrin I is not used as a therapeutic in humans, so a clinical safety profile for the parent peptide is not established. For radiolabeled minigastrin analogs, the principal published limitation is off-target accumulation of radioactivity in the kidneys, which constrains the deliverable tumor dose and motivates ongoing analog engineering (Roosenburg and colleagues, Amino Acids, 2011).
Regulatory status
- US: Not an FDA-approved drug. Used as a research reagent.
- EU: No EMA approval as a medicinal product.
- Research use: Available from peptide suppliers as a synthetic standard for CCK2R pharmacology and as a starting point for tracer chemistry.
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.
Has Minigastrin I been assigned to the wrong receptor in the database, given that all published cancer imaging studies use it to target CCK2R?
Correcting this annotation would prevent researchers from drawing false conclusions about CCK1R pharmacology from Minigastrin data, and would ensure that cancer imaging scientists can find this peptide correctly when searching for CCK2R-targeted agents.
Could Minigastrin be adapted to carry a new type of cancer drug called a PROTAC selectively into tumor cells that overexpress its receptor?
If Minigastrin can deliver protein-degrading drugs directly into the right cancer cells, it could enable effective treatment of rare but aggressive neuroendocrine tumors like medullary thyroid cancer and small cell lung cancer, with much less harm to healthy tissues than conventional chemotherapy.
Is the string of five glutamate amino acids in Minigastrin just a generic charge spacer, or does it have a specific chemical role that cannot be replaced?
If the glutamate stretch is replaceable, researchers could design improved versions of Minigastrin-based cancer imaging agents with less accumulation in the kidneys, reducing radiation dose to patients during PET or SPECT imaging of tumors.
Could replacing some of the glutamate amino acids in Minigastrin with a modified version reduce kidney damage while keeping the cancer-targeting ability intact?
Kidney damage currently limits how much of a Minigastrin-based cancer therapy can be given safely. Solving this problem could allow doctors to give higher, more effective doses to patients with medullary thyroid cancer or small cell lung cancer, potentially improving cure rates.
Is the version of Minigastrin without a sulfate chemical modification more specific for cancer cells and less likely to show up in healthy pancreatic tissue during imaging scans?
If the unsulfated form is more tumor-specific, it would reduce false signals from the pancreas during PET scans for medullary thyroid cancer and small cell lung cancer, making the diagnosis clearer and reducing the need for additional confirmatory tests.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8521436452865601 | boltz-2 |
| ranking score | 0.7606279253959656 | boltz-2 |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 1.280 | 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{pep10612,
sequence = {LEEEEEAYGWMDF},
target = {cckar},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}