Bombesin
Also known as: BBS, BB, Bn, GRP analog, gastrin-releasing peptide analog, neuromedin B-related peptide, bombesin-like peptide
Tetradecapeptide neuropeptide; amphibian bombesin-family peptide; GRPR/BB2 agonist; research radiopharmaceutical scaffold
What it is
Bombesin is a small signaling peptide that researchers study mainly because certain cancers — including breast, prostate, and lung tumors — display far more bombesin receptors than healthy tissue. Scientists are attaching radioactive isotopes to bombesin analogs to create targeted cancer imaging agents and experimental radiotherapies. It is not approved as a drug for human use.
The scientific side
Bombesin is described as a 14-amino acid neuropeptide originally isolated from the skin of Bombina bombina (European fire-bellied toad), with two principal mammalian homologs: gastrin-releasing peptide (GRP) and neuromedin B (NMB). These peptides act through three G-protein-coupled receptor subtypes: BB1 (NMB-preferring), BB2 (GRP-preferring, also called GRPR), and BB3 (bombesin receptor subtype-3, BRS-3, an orphan receptor). Peripherally, bombesin and GRP regulate gastrointestinal function, stimulating release of gastrin, cholecystokinin, and other gut hormones, increasing gastric mucosal blood flow and bicarbonate secretion, and exerting gastroprotective effects through capsaicin-sensitive afferent neurons and nitric oxide synthase activation (PMID 15650631). Bombesin acting centrally — particularly within the paraventricular nucleus, preoptic area, anterior hypothalamus, and dorsal vagal complex — potently inhibits gastric acid secretion when introduced into cerebrospinal fluid, and regulates satiety signaling through hypothalamic circuits (PMID 11090915). BB2/GRPR activation by GRP-29 in the celiac arterial vascular bed reduces meal size and prolongs the inter-meal interval, contributing to postprandial satiety (PMID 27381650). BRS-3 (BB3) is an orphan receptor implicated in energy homeostasis, glucose regulation, and lung development; knockout mouse studies show that BRS-3 loss leads to obesity, impaired glucose tolerance, and altered tumor growth (PMID 31911345). Neuromedin B acting on BB1 receptors in the central lateral amygdala excites neurons by inhibiting potassium channels via phospholipase C and protein kinase C, reducing cardiovascular output and attenuating fear-potentiated startle responses (PMID 37186390). The oncological relevance of bombesin receptors derives from their marked overexpression on breast, prostate, small cell lung carcinoma, and certain CNS tumor cells relative to surrounding normal tissue. GRPR signaling cross-talks with the Sonic hedgehog pathway in small-cell lung carcinoma (PMID 25517020). This receptor overexpression is exploited in targeted radiopharmaceutical development: bombesin analogs are conjugated to chelators loaded with diagnostic isotopes (e.g., 68Ga, 111In, 44Sc) or therapeutic isotopes (e.g., 177Lu, 47Sc) to deliver imaging signal or cytotoxic radiation selectively to tumor cells. Novel strategies include homodimeric RM2-based radioligands for enhanced breast cancer uptake (PMID 42479469), PSMA/GRPR heterodimer conjugates for dual-target prostate imaging (PMID 42447187, 42235186), and knottin-scaffold modifications that increase radiochemical stability of bombesin precursors (PMID 39539754).
Class: Tetradecapeptide neuropeptide; amphibian bombesin-family peptide; GRPR/BB2 agonist; research radiopharmaceutical scaffold
Administration & storage
- Administration
- Intravenous injection (systemic biodistribution studies and clinical radionuclide therapy trials)Intracerebroventricular infusion (central mechanism studies in rodents — not applicable to humans)Intra-arterial celiac administration (GRP receptor satiety studies — experimental model only)Subcutaneous injection (some preclinical pharmacological studies)
- Storage
- Research-grade lyophilized bombesin: store at -20°C or below, desiccated. Reconstituted solutions: use immediately or aliquot and store at -80°C; avoid repeated freeze-thaw cycles. Radiolabeled analogs: handled per nuclear medicine regulatory requirements with appropriate decay-in-storage procedures.
- Cautions
- Bombesin is not approved for human administration outside of clinical trials — no safe consumer dosing protocol has been established.,Radiolabeled bombesin analogs (e.g., [177Lu]Lu-NeoB) carry ionizing radiation risks requiring medical supervision, dosimetry monitoring, and administration only in licensed nuclear medicine facilities.,Dose-limiting toxicities with [177Lu]Lu-NeoB were observed at 11.1 GBq in Phase 1 (four DLTs recorded), indicating a narrow therapeutic window for therapeutic radionuclide applications (PMID 41344852).,Bombesin can stimulate gastrin release and gastric acid secretion at peripheral doses; potential to provoke or exacerbate peptic ulcer disease or acid-related gastrointestinal disorders.,BRS-3 modulation affects glucose homeostasis and energy balance; systemic bombesin receptor agonism could theoretically affect insulin secretion and metabolic parameters (PMID 31911345, 25517020).,Central administration of bombesin-family peptides in animal models affects cardiovascular output and fear responses (PMID 37186390) — CNS safety profile in humans is unknown.
Legal & regulatory status
Bombesin itself is not FDA-approved as a drug or diagnostic agent. Its mammalian homologs (gastrin-releasing peptide, neuromedin B) and radiolabeled synthetic analogs (e.g., [177Lu]Lu-NeoB, RM2-based conjugates) are…
Bombesin is not listed on the current WADA Prohibited List. It has no established performance-enhancing application in sport. Its primary research application is in cancer imaging and targeted radiotherapy, not athletic…
Bombesin and its analogs are not approved by Health Canada as therapeutic or diagnostic agents. Radiolabeled bombesin analogs targeting GRPR are in preclinical and early clinical investigation internationally; no Health…
What it's studied for
- Targeted cancer imaging (PET/SPECT) via radiolabeled bombesin/GRPR analogs Phase I Clinical Trial / Preclinical
- Targeted radiotherapy (radionuclide therapy) for GRPR-overexpressing cancers Phase I Clinical Trial / Preclinical
- Satiety and appetite regulation — gut-brain axis signaling Preclinical (Animal) / Human mechanistic studies
- Gastroprotection and gastric acid regulation Preclinical (Animal) / Human mechanistic studies
- CNS effects — fear, cognition, and cardiovascular regulation via neuromedin B Preclinical (Animal)
- Fetal lung development — neuroendocrine signaling Preclinical (Animal)
Safety signals
- Dose-limiting toxicity with therapeutic radiolabeled analogs ([177Lu]Lu-NeoB)
- Gastric acid stimulation and potential gastrointestinal effects
- Metabolic and endocrine disruption via BRS-3 modulation
- Cardiovascular and CNS effects via central bombesin receptor activation
- Ionizing radiation exposure from radiolabeled analogs
Contraindications
About these dose ranges
Dose ranges below reflect commonly reported community protocols. Where published research cites a specific dose, the PMID is linked. Doses without citations are not clinical recommendations — they reflect what practitioners and researchers commonly report using.
Community-reported dosing
| Route | Dose | Frequency / Duration | Population / context | Source tier |
|---|---|---|---|---|
| Unspecified | [177Lu]Lu-NeoB: escalating doses from ~3.7 GBq to 11.1 GBq per cycle | — | Advanced solid tumor patients — GRPR-targeted radionuclide therapy (Phase 1) | Research |
| Unspecified | Nanomole-scale tracer quantities (pmol–nmol range) for imaging; higher specific activity preparations for therapy | — | Preclinical cancer models — radiolabeled analog biodistribution studies | Research |
| Unspecified | Intracerebroventricular: nanomole to picomole quantities; intravenous/intraperitoneal: microgram/kg range | — | Rodent models — central and peripheral administration (mechanistic studies) | Research |
| Not applicable for consumer use | No consumer dosing established — bombesin is used only in controlled research settings | Not applicable | No established consumer population; strictly a research and investigational radiopharmaceutical compound |