A new method of delivering a dose of radioactive iodine - using a man-made version of scorpion venom as a carrier - targets deadly brain tumors called gliomas without affecting neighboring tissue or body organs.
After a Phase I clinical trial conducted in 18 patients showed the approach to be safe, a larger Phase II trial is underway to assess the effectiveness of multiple doses.
Adam N. Mamelak, M.D., a neurosurgeon at Cedars-Sinai Medical Center's Maxine Dunitz Neurosurgical Institute, led the Phase I trial and is first author of an article in the August of the Journal of Clinical Oncology.
The key ingredient is TM-601, a synthetic version of a peptide, or protein particle, that naturally occurs in the venom of the Giant Yellow Israeli scorpion. TM-601 binds to glioma cells and has an unusual ability to pass through the blood-brain barrier that blocks most substances from reaching brain tissue from the bloodstream.
"We're using the TM-601 primarily as a carrier to transport radioactive iodine to glioma cells, although there are data to suggest that it may also slow down the growth of tumor cells. If studies continue to confirm this, we may be able to use it in conjunction with other treatments, such as chemotherapy, because there may be a synergistic effect. In other words, TM-601's ability to impede cancer growth could allow us to reduce the dose of chemotherapy to achieve a therapeutic effect," said Mamelak, who serves as co-director of the Pituitary Center at Cedars-Sinai.
About 17,000 Americans are diagnosed with gliomas each year. The tumors are extremely aggressive and deadly, with only eight percent of patients surviving two years and three percent surviving five years from time of diagnosis. Even when surgery is performed to remove a glioma, some cancer cells invariably remain behind and proliferate.
"Despite advances in surgical technology, radiation therapy and cancer-killing drugs, length of survival has remained virtually unchanged for patients with gliomas," said Keith L. Black, M.D., director of the Maxine Dunitz Neurosurgical Institute and interim chair of Cedars-Sinai's Department of Neurosurgery. "Only in the recent past have we begun to discover some of the molecular, genetic and immunologic mechanisms that enable these deadly cancer cells to evade or defy our treatments, and we are developing innovative approaches, such as this one, that capitalize on these revelations."
Patients who consented to participate in the Phase I study first underwent tumor-removal surgery. Fourteen to 28 days later, a single, low dose of radioactive iodine (131I) attached to TM-601 was injected through a small tube into the cavity from which the tumor had been removed.