Genetically Modified Cold Sore Virus Shrinks Melanoma Tumors

A cancer drug based on a tumor-killing virus made tumors disappear or at least shrink by half for at least six months, and has for the first time succeeded in a late-stage clinical trial.

Amgen, which is developing the drug, said late Tuesday that it had met the primary goal of a Phase 3 clinical trial in patients with advanced melanoma, the deadliest type of skin cancer. The company reports that 16 percent of the patients who received TVEC experienced tumor shrinkage that persisted for six months compared with only 2 percent in a control group that received a treatment based on GM-CSF, a protein that stimulates the immune system.

The drug works in two complementary ways by combining a gene snippet meant to stimulate the body's immune system with a modified version of the herpes simplex virus, the kind that causes mouth cold sores. The TVEC is injected directly into tumor tissue, where it divides into copies repeatedly until the membranes, or outer layers, of the cancer cells burst, destroying them. Meanwhile, the gene snippet churns out a protein to stimulate a systemic immune response to kill melanoma cells in the tumor and elsewhere in the body.

"These are the first (late-stage) results of this novel approach to cancer therapy," Dr. Sean E. Harper, head of research and development at Amgen, said in a statement. "A high unmet need exists in melanoma and we believe the innovative mechanism of action of talimogene laherparepvec may offer a promising approach for these patients."

Melanoma is one of the most aggressive skin cancers. It causes 75 percent of all skin cancer deaths, even though the roughly 132,000 new melanoma cases around the world each year amount to less than 5 percent of all skin cancer cases.