Chlorotoxin is a 36 amino acid peptide that comes from the venom of the deathstalker scorpion (Leiurus quinquestriatus). Chlorotoxin targets cells expressing matrix metalloproteinase-2 isoforms. These isoforms are specifically upregulated in gliomas and other cancers of neuroectodermal origin, but are not normally expressed in the brain. Chlorotoxin is a high-affinity peptide ligand for chloride channels in glioma cells, but does not affect normal glial cells.
Chlorotoxin-SAP is a bonded toxin between biotinylated chlorotoxin and the secondary conjugate Streptavidin-ZAP containing the ribosome-inactivating protein, saporin. It eliminates cells expressing MMP-2 isoforms.