Page data last changed: . Chemistry registry snapshot: . Registry refreshes and identity assessments are separate from scientific content review.
A 36-residue scorpion peptide that homes to glioma cells and lit up the fluorescent 'tumor paint' concept.
Also known as: CTX · ClTx · tozuleristide · TM-601
Part of the Foundational & therapeutic peptides cluster
Overview
Chlorotoxin is a 36-amino-acid peptide from deathstalker scorpion venom, stabilized by four disulfide bonds. It binds targets enriched on glioma and other tumor cells, including matrix metalloproteinase-2 and small-conductance chloride channels, and has been developed into fluorescent conjugates ('tumor paint') to help surgeons see cancer margins. This page is educational and not medical advice.
Source & context
Biological / chemical source: Venom of the deathstalker scorpion (Leiurus quinquestriatus)
Primary research or clinical context: Research and imaging tool; investigational tumor-targeting agent ('tumor paint')
Tumor-homing peptide
Although first described as a chloride-channel blocker, chlorotoxin's practical interest comes from its selective binding to glioma cells over healthy brain tissue, linked to MMP-2 and related surface complexes. Its small, disulfide-locked scaffold is stable and tolerant of chemical conjugation, making it a versatile targeting ligand.
Imaging and research use
Chlorotoxin fused to dyes such as Cy5.5 forms intraoperative imaging agents studied to highlight tumor tissue, while a synthetic version (TM-601) and CAR-T targeting approaches have been explored in oncology research. It is used here as an educational example of venom-derived molecular tools, not as an approved therapy.
Structure & chemistry
Molecular identity & reference confidence
Source-supported reference
Reference values are taken from the cited molecular record or curated profile. A database match is not independent laboratory verification; modifications, counter-ions, and formulations can change the measured mass.
- Molecular form
- Chlorotoxin (source record; form not independently established)
- Species
- Not established by this molecular identity audit
- Termini (N / C)
- Not specified / Not specified
Average reference mass
Reference policy updated: 2026-10-05
- IUPHAR/BPS source snapshot · 2026-10-01
- PubChem molecular record · 2026-10-01
- Molecular formula
- C158H249N53O47S11
- Average reference mass
- ≈ 3,996
- PubChem CID: 86278273
- IUPHAR ligand: 2537
- CAS RN: 163515-35-3
- UNII: 06UV5RFW57
Chemistry values: PubChem, IUPHAR/BPS Guide to Pharmacology · fetched 2026-10-01.
Clinical development snapshot
ClinicalTrials.gov lists 8 registered studies with “Chlorotoxin” as an intervention (snapshot 2026-09-06). A registry footprint is not evidence of efficacy or approval.
| NCT | Title | Phase | Status | Updated |
|---|---|---|---|---|
| NCT04214392 | Chimeric Antigen Receptor (CAR) T Cells With a Chlorotoxin Tumor-Targeting Domain for the Treatment of MMP2+ R | Phase 1 | active not recruiting | 2026-08-24 |
| NCT05627323 | CAR T Cells in Patients With MMP2+ Recurrent or Progressive Glioblastoma | Phase 1 | terminated | 2026-06-29 |
| NCT00683761 | A Study of 131I-TM601 in Adults With Recurrent Malignant Glioma | Phase 2 | unknown | 2009-07-17 |
| NCT00591058 | Safety and Dose-Finding Study of TM-601 in Adults With Recurrent Malignant Glioma | Phase 1 | unknown | 2009-07-17 |
| NCT00733798 | A Safety and Efficacy Study of Intravenous 131I-TM601 in Adult Patients With Malignant Melanoma | Phase 2 | terminated | 2009-05-11 |
| NCT00114309 | 131-I-TM-601 Study in Adults With Recurrent High-Grade Glioma | Phase 2 | unknown | 2009-04-03 |
Chlorotoxin — reconstitution calculator
Enter how much peptide is in the vial and how much diluent (e.g. bacteriostatic water) is added. The tool returns the resulting solution concentration — and, for any amount you type, the volume it corresponds to. This is educational arithmetic, not a dosing recommendation.
Reference form: Chlorotoxin (source record; form not independently established)Average reference mass: 3,996 Da
Enter an amount to see the volume it corresponds to.
Educational concentration mathematics only. This tool does not recommend a dose, amount, or protocol, and nothing here is medical advice. Many peptides are not authorized by Health Canada for human use — see our reconstitution and bacteriostatic-water guides for context.
FAQ about Chlorotoxin
What is Chlorotoxin?+
Chlorotoxin is a 36-amino-acid peptide from deathstalker scorpion venom, stabilized by four disulfide bonds. It binds targets enriched on glioma and other tumor cells, including matrix metalloproteinase-2 and small-conductance chloride channels, and has been developed into fluorescent conjugates ('tumor paint') to help surgeons see cancer margins. This page is educational and not medical advice.
What Canadian product status is recorded for Chlorotoxin?+
Canadian product status for Chlorotoxin has not been verified in this profile. No verified record here does not mean no authorization exists. Status depends on the product, formulation and use; consult Health Canada's product records.
What is the typical length of Chlorotoxin?+
Chlorotoxin is commonly described as approximately 36 amino acids (Scorpion-venom peptide (toxin)).
Related peptides
References & further reading
- 1.McGonigle et al. (2019). Neuropilin-1 drives tumor-specific uptake of chlorotoxin. Cell Commun Signal
- 2.Mamelak et al. (2007). Targeted delivery of antitumoral therapy to glioma and other malignancies with synthetic chlorotoxin (TM-601). Expert Opin Drug Deliv
- 3.Dardevet et al. (2015). Chlorotoxin: a helpful natural scorpion peptide to diagnose glioma and fight tumor invasion. Toxins (Basel)
- 4.Ojeda et al. (2017). Lysine to arginine mutagenesis of chlorotoxin enhances its cellular uptake. Biopolymers
- 5.Cohen-Inbar et al. (2016). Glioblastoma multiforme targeted therapy: The Chlorotoxin story. J Clin Neurosci
- 6.Ojeda et al. (2016). Chlorotoxin: Structure, activity, and potential uses in cancer therapy. Biopolymers
- 7.Kasai et al. (2012). Chlorotoxin Fused to IgG-Fc Inhibits Glioblastoma Cell Motility via Receptor-Mediated Endocytosis. J Drug Deliv
- 8.Kobets et al. (2021). Unexpected Binding of Tozuleristide "Tumor Paint" to Cerebral Vascular Malformations: A Potentially Novel Application of Fluorescence-Guided Surgery. Neurosurgery
- 9.UniProtKB — Chlorotoxin, Leiurus quinquestriatus (P45639)
- 10.Wikipedia — Chlorotoxin