Chlorotoxin

Chlorotoxin is a 36 amino-acid peptide from the venom of the Israeli scorpion Leiurus quinquestriatus with anticancer activity. Chlorotoxin is a chloride channel blocker. IC50 & Target: Target: Chloride Channel^[1] In Vitro: Chlorotoxin (Chlorotoxin) preferentially binds to tumor cells and has been harnessed to develop an imaging agent to help visualize tumors during surgical resection. In addition, chlorotoxin has potential as a vehicle to deliver anti-cancer drugs specifically to cancer cells. Chlorotoxin is shown to bind glioma cells, but is unable to bind normal rat astrocytes and Te671, a human rhabdomyosarcoma cell line. Chlorotoxin inhibits the migration of U251MG (glioma) cells, with an IC₅₀ of 600 nM^[2]. Chlorotoxin binds to glioma cells is specific and involves high affinity (K_d=4.2 nM) and low affinity (K_d=660 nM) binding sites^[3].Small conductance chloride channels are shown to be potently blocked by Chlorotoxin. Chlorotoxin has been used as a general pharmacological tool to investigate the function of chloride channels^[4]. In Vivo: Chlorotoxin shows insecticidal activity on insects and other invertebrates. After the administration of I-Chlorotoxin to tumor-bearing mice, the peptides accumulated within the tumor^[2].Chlorotoxin selectively accumulates in the brain of tumor-bearing mice with calculated brain: muscle ratios of 36.4% of injected dose/g (ID/g), as compared to 12.4%ID/g in control animals^[3].