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The science behind this clinical trial sounds more like a video game—researchers hijack the virus that causes cold sores and change its genome so it attacks only melanoma cells. Once inside the body, the virus replicates, blows up the melanoma cells, and releases a factor that trains the patient’s immune system to chase down and deactivate melanoma-related proteins wherever they may be.
It’s called oncolytic immunotherapy—treatment that uses the patient’s own immune system to burst cancer cells open. And in this case, it can also search out and destroy melanoma cells that may have spread to the lymph nodes, lung, liver, or brain.
“The body’s immune system develops a memory of the melanoma proteins,” said Robert Andtbacka, MD, CM, associate professor in the Division of Surgical Oncology, a surgeon and investigator with Huntsman Cancer Institute, and principal investigator for the clinical trial. “It becomes educated to recognize and fight these melanoma-specific proteins wherever they appear through the body.”
The name of the transformed virus is talimogene laherparepvec, or T-VEC. In the clinical trial, melanoma tumors in patients were directly injected with T-VEC that was genetically encoded to produce a growth factor called granulocyte-macrophage colony-stimulating factor, or GM-CSF, once inside the tumor. This growth factor is a support medication commonly used to stimulate a patient’s white blood cell recovery after chemotherapy or stem-cell transplant. Other patients in the study received injections of GM-CSF alone just under the skin.
Data from the Phase III clinical trial are still being analyzed, but the initial results show the patients who received T-VEC had a more robust response. Their tumors—both injected and non-injected—shrank, and the response lasted longer compared to patients who received GM-CSF just under the skin. In more than half the patients who had tumor shrinkage with T-VEC, the response lasted for more than 12 months. The length of time a response holds, called the “durable response,” is important because often the therapies used for melanoma appear promising at first but resistance sets in, allowing the disease to progress. In addition, an interim analysis shows a trend toward longer patient survival times for T-VEC/GM-CSF patients. The initial results of the trial were presented at the 2013 American Society of Clinical Oncology (ASCO) annual meeting.
“Fifteen years ago, we had very few treatments that improved survival in patients with melanoma,” said Andtbacka. “In the past 10 years or so, the focus changed to immunotherapy and survival improved. With this study it continues to improve.” Although FDA approval of T-VEC could still be years from now, the results of this study show what’s possible—to help melanoma patients fight the disease and live longer.