Exendin-4 imaging

Ga-68 NODAGA-exendin-4, Ga-68 DOTA-exendin-4, In-111 DTPA-exendin-4, Tc-99m HYNIC-exendin-4, F-18 exendin-4 variants; "exendin PET", "GLP-1R imaging"

Oncology & imaging

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Summary

Class: Synthetic 39-amino-acid peptide (exendin-4, the Gila-monster venom peptide that exenatide is based on) conjugated at the C-terminus (via a lysine-40 extension) to a chelator (NODAGA, DOTA, DTPA or HYNIC) carrying Ga-68, In-111 or Tc-99m
Mechanism: Binds the GLP-1 receptor, which is expressed at extremely high density on insulinomas (and on normal pancreatic beta cells), and is internalised; the isotope lets a PET or SPECT camera find tumours that are often under 1 cm and invisible to CT/MRI
Routes studied: Intravenous only
Half-life: Ga-68 68 min; In-111 2.8 days. Exendin-4 itself has a plasma half-life of ~2–3 h; kidney retention of the labelled peptide is high and prolonged
Storage: Research radiopharmacy only
Regulatory status: Not approved anywhere; investigational, in use at specialist European and Chinese centres under trial or compassionate frameworks †

Doses are as reported in studies or by the community — never recommendations.

1What it is

Exendin-4 is a 39-amino-acid peptide from the saliva of the Gila monster lizard. It is a potent, long-acting of the GLP-1 receptor, and a synthetic copy is the approved diabetes drug exenatide (see exenatide profile in set 2). The GLP-1 receptor is present on normal insulin-producing beta cells and at very high density on insulinomas, the rare tumours that cause dangerous low blood sugar. Insulinomas are tiny and often missed by CT, MRI and endoscopic ultrasound, and since many lack SSTR2 they also escape DOTATATE PET (#201). Researchers in Basel and Nijmegen attached radiometals to exendin-4 so the receptor could be imaged directly. The approach works well enough that it is being used clinically at specialist centres, but no product has been commercially licensed.

2How it's thought to work

Receptor density. insulinomas express GLP-1R at some of the highest receptor densities of any human tumour, giving very high tumour-to-background contrast in the pancreas.

Internalisation. exendin-4 is an and the receptor-ligand complex is taken into the cell, trapping the radiometal.

Kidney retention. the labelled peptide is filtered and reabsorbed in the proximal tubule, so kidneys take up a large dose; this limits the activity that can be given and complicates imaging of lesions near the kidney.

Hypoglycaemia risk. even micrograms of an active GLP-1 agonist can boost insulin release in a patient whose tumour already causes hypoglycaemia, so a glucose drip runs during the scan.

Exendin-4 used as a targeting ligand rather than a drug. Labelled and given in trace amounts, it finds the GLP-1 receptor on insulinomas and on residual beta-cell mass.Schematic — not to scale

3What the research shows

In-111 DTPA-exendin-4 SPECT/CT

A prospective multicentre study in 30 patients with suspected insulinoma (sensitivity 95% vs 47% for CT/MRI) first established the method and showed that it detected tumours missed by every other test (Christ 2013, Lancet Diabetes Endocrinol). Imaging over three days with In-111 was the main drawback. [2]

Ga-68 NODAGA-exendin-4 PET/CT vs standard imaging

A prospective multicentre European study of 69 adults with biochemically proven endogenous hyperinsulinaemic hypoglycaemia (54 with surgical confirmation) found exendin PET/CT accuracy of 94% with sensitivity 94%, versus 65% for Ga-68 DOTA-somatostatin PET, 83% for contrast CT/MRI and 83% for endoscopic ultrasound. In 9–13% of patients it was the only test that gave the correct answer (Boss 2024, J Nucl Med). An earlier prospective comparison in 52 patients showed similar superiority of PET over SPECT and conventional imaging (Antwi 2018, Eur J Nucl Med Mol Imaging). [4][5]

Graded B (small)

Malignant insulinoma

Malignant insulinomas often lose GLP-1R and gain SSTR2, so exendin PET is less sensitive and DOTATATE PET becomes positive; this receptor switch is useful diagnostically (Wild 2011, J Nucl Med). [3]

Graded B/C

Beta-cell mass imaging in type 1 diabetes and after islet transplant

Attempts to quantify beta-cell mass with exendin tracers in healthy people and in type 1 diabetes have produced inconsistent correlations with beta-cell function; the signal appears dominated by non-beta-cell and kinetic factors (Brom 2014; Eriksson 2014 and follow-up work) †. [6]

Graded B (small)

Congenital hyperinsulinism in infants

Pilot studies in children evaluated exendin PET against F-18 DOPA PET for focal lesions; data remain preliminary †.

4Reported side effects and interactions

Literature-reported

the only clinically meaningful event is hypoglycaemia during or after injection in patients with insulinoma, reported in a minority despite glucose infusion; nausea and vomiting from the GLP-1 effect occur in some patients. Kidneys receive the highest radiation dose (effective dose comparable to other Ga-68 peptide scans overall).

Community-reported

Community use. essentially none documented. Unlabelled exendin-4 is the pharmaceutical exenatide, covered elsewhere.

Theoretical. repeated scans in children raise cumulative renal dose considerations.

Interactions. current GLP-1 agonist therapy (exenatide, liraglutide, semaglutide and others) would compete for the receptor and should be stopped before the scan; periods in trials vary †. Diazoxide or octreotide given to control hypoglycaemia do not appear to block uptake but practice is to document them.

Markers researchers commonly monitor

Taken from the trial protocols for the scan itself:

Marker	Why it's watched
Plasma glucose, before, during and for hours after injection	hypoglycaemia is the one real safety issue; glucose infusion is standard.
Fasting insulin, C-peptide and proinsulin during a supervised 72-hour fast	the biochemical diagnosis that must precede imaging; the scan only localises, it does not diagnose.
Creatinine/eGFR	kidneys receive the highest absorbed dose.
Chromogranin A and Ga-68 DOTATATE PET	if malignancy is suspected, because malignant insulinomas switch receptor profile.
Histopathology after surgery	the reference standard against which the scan's accuracy is judged.

Free for everyone. Safety information is never behind a paywall.

5Reconstitution and handling

Not applicable to individuals. The peptide-chelator conjugate is labelled with generator Ga-68 in a research radiopharmacy under GMP-like conditions; investigators note the need to keep the peptide mass low (micrograms) to limit pharmacological effect. No calculator link is provided for this compound.

6Commonly studied alongside

Exenatide (the therapeutic form of the same peptide; set 2); DOTATATE (#201) as the complementary scan in malignant insulinoma; F-18 DOPA PET (the alternative tracer in congenital hyperinsulinism); diazoxide and octreotide (#124) as medical control of hypoglycaemia around surgery.

Informational cross-links. Not stack recommendations.

7Regulatory status by region

Region	Status (checked —)
United States	Not FDA-approved; limited investigational use †
European Union	Not authorised; used under clinical-trial or named-patient/compassionate frameworks at specialist centres (Netherlands, Switzerland, Germany, Finland, Austria among trial sites)
United Kingdom	Not licensed; no routine access †
Australia	Not approved; research use only †
South Africa	Not registered
Sport (WADA)	Not listed as a radiopharmaceutical; GLP-1 agonists are not prohibited as of 2026 †

8Open questions

Will any sponsor take Ga-68 exendin-4 (or an F-18 version) through registration for a disease this rare?
Can kidney uptake be reduced (e.g. with gelofusine, lysine or cleavable linkers) to improve image quality and allow therapy with Lu-177 exendin?
Does exendin imaging have a reliable role in beta-cell mass quantification or in congenital hyperinsulinism?

9References

1Wild D et al. (2008). [Lys40(Ahx-DTPA-111In)NH2]exendin-4, a very promising ligand for glucagon-like peptide-1 (GLP-1) receptor targeting. J Nucl Med. PubMed
2Christ E et al. (2013). Glucagon-like peptide-1 receptor imaging for the localisation of insulinomas: a prospective multicentre imaging study. Lancet Diabetes Endocrinol. PubMed · DOI
3Wild D et al. (2011). Glucagon-like peptide-1 versus somatostatin receptor targeting reveals 2 distinct forms of malignant insulinomas. J Nucl Med. PubMed · DOI
4Antwi K et al. (2018). Comparison of glucagon-like peptide-1 receptor (GLP-1R) PET/CT, SPECT/CT and 3T MRI for the localisation of occult insulinomas: evaluation of diagnostic accuracy in a prospective crossover imaging study. Eur J Nucl Med Mol Imaging. PubMed · DOI
5Boss M et al. (2024). Improved localization of insulinomas using 68Ga-NODAGA-exendin-4 PET/CT. J Nucl Med. PubMed · DOI
6Brom M et al. (2014). Non-invasive quantification of the beta cell mass by SPECT with 111In-labelled exendin. Diabetologia. PubMed · DOI

References are being resolved to PubMed/DOI identifiers; links search PubMed for the citation until then.

† Being confirmed by our reviewers against current sources.

10Community

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11Page history

31 Oct 2026Profile published — awaiting medical review

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