Chlorotoxin

Overview
Chlorotoxin is a 36-amino acid peptide found in the venom of the deathstalker scorpion (Leiurus quinquestriatus). A synthetically modified version, 131I-chlorotoxin or TM-601, is under investigation for the treatment of gliomas, because it specifically binds to glial tumor cells, but not normal cells.

Researchers at Seattle Children’s Hospital Research Institute and Fred Hutchinson Cancer Research Center have recently used Chlorotoxin in combination with fluorescent material named, Cy5.5 to first ever demarcate cancer cells from surrounding normal cells. Chlorotoxin:Cy5.5 is a fluorescent molecular material emitting photons in the near infrared spectrum and hence, can be visualized in operating room with the aid of infrared glasses. This illumination gives surgeons a better chance of removing all of the cancerous cells during surgery without injuring surrounding healthy tissue. Team has conducted pre-clinical study in mouse models where they showed positive results in brain tumors. To note, approximately 80% of malignant cancers of brain recur at the edges of the surgical site. Current technology (such as MRI with contrast agent) can distinguish tumors from healthy tissue only if more than 1 million cancer cells are present. But Cy5.5 can identify tumors with as few as 2000 cancer cells, making it 500 times more sensitive than MRI. Chlorotoxin:Cy5.5 could be used in operating rooms in as little as 18 months as team is planning to conduct clinical trial in coming months. Original article can be found in July 15, 2007 issue of Cancer Research