New Type of Immunotherapy Approved for Melanoma

Earlier this week, the U.S. Food and Drug Administration (FDA) approved a first-of-its kind immunotherapeutic, talimogene laherparepvec or T-Vec for short (Imlygic), for the treatment of melanoma lesions in the skin and lymph nodes that cannot be removed completely by surgery.

Melanoma. Photo courtesy of the National Cancer Institute.
Melanoma. Photo courtesy of the National Cancer Institute.

T-Vec is the first of a class of immunotherapeutics called oncolytic viruses to be approved by the FDA. Oncolytic viruses are viruses, which may or may not be genetically modified in some way, that can infect and kill cancer cells, releasing molecules that can trigger immune cells that have the natural potential to destroy yet more cancer cells. They are injected directly into patients’ tumors, rather than being given orally or by intravenous infusion.

T-Vec itself is a herpes simplex virus (HSV) type 1 that has been genetically modified in a number of ways so that it is less able to cause disease, is more selective for cancer cells, and is better able to promote an anticancer immune response. Specifically, two nonessential viral genes, ICP34.5 and ICP47, have been deleted and one gene that provides the instructions for making an immune system-enhancing factor called GM-CSF has been added.

The FDA approval of T-Vec was based on results from a phase III clinical trial of 436 patients with stage IIIB or IV melanoma that were published earlier this year in the Journal of Clinical Oncology. Specifically, it was based on the observation that 16.3 percent of patients who had T-Vec injected into their skin and lymph node melanoma lesions saw these lesions decrease in size or disappear, for a minimum of six months, compared with 2.1 percent of patients who had GM-CSF injected under their skin.

It is important to note, however, that T-Vec did not have a statistically significant effect on median overall survival, although there was a trend toward an improvement.

With incidence rates of melanoma bucking the trend and rising year after year, T-Vec provides a welcome new treatment option for patients diagnosed with this disease. Moreover, with ongoing clinical trials testing T-Vec in combination with other immunotherapeutics that work in a different way to enhance the antimelanoma immune response, specifically ipilimumab (Yervoy) and pembrolizumab (Keytruda), it is hoped that many more patients with melanoma will benefit from the revolutionary new anticancer therapeutic in the future.

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