Some of these venoms block nerve signals by binding to the ion channels in nerve cells, preventing the neurons from getting energy and making easy dinner for the insect or, in this case, the scorpion. To find out, Sontheimer tested hundreds of insect venoms against human gliomas growing in lab mice. Eventually he found that chlorotoxin, an agent previously isolated at Harvard University from the venom of the Israeli giant scorpion, indeed binds to the ion channels. Sontheimer says that during more than 1,000 tests on human tissue freshly removed during unrelated surgeries, the agent bound only to glioma cells. Although the venom-derived compound did bind to the human tumors growing in mice, Sontheimer has not tried to kill those cells.
Tumors grow very differently in mice.
Sontheimer is a founder of Transmolecular, Inc., a drug-development company that is working on the ligand. But with the idea of using chlorotoxin as a ferrying agent to carry a lethal cargo to glioma cells, he has already attached a radioactive atom and, separately, a conventional cancer drug, to chlorotoxin. Yet while the ingredients of a successful assault on glioma seem to be in place, it's far too early to declare victory. The mechanism is unproven. Many promising cancer drugs reach this stage but fail in human trials.