Purified toxin (ClTx) reproduced the venom activity initially reported by DeBin and Strichartz [143] and blocked CIC with a KD of ~600 nM. ClTx caused progressive, reversible paralysis (recovery depended on venom dose) in crayfish and cockroaches, and accounted for ~4.3% of the venom protein content. Blockade seen only when ClTx was applied to the cytoplasmic surface. A later study reported that ClTx applied extracellularly did not block volume-regulated, CFTR (cAMP-regulated) and glioma-specific Cl− channels [147]. The gene discussed is CFTR; the disease is central nervous system cancer.