A new drug that is based on the herpes virus has been shown to be effective in treatment of aggressive skin cancer.

The tests are in phase 3 trials for cancer virotherapy.  The idea of the therapy is to use one disease to attack a different disease.

The drug, T-VEC, could become more widely available for cancer patients next year.

The drug is a modified form of the herpes simplex virus type-1 with two genes removed that keeps the virus from replicating in healthy cells.  The virus can infect cancer cells where it multiplies and then explodes the cells.  It also creates a molecule that will allow immune systems to attack and destroy tumors.

Over one in four patients in the trial showed response to the treatment including 1 in 10 of those patients having their tumors completely disappear.  Another 16% had partial remission that lowered tumor size by half.

“There is increasing excitement over the use of viral treatments like T-VEC for cancer, because they can launch a two-pronged attack on tumors — both killing cancer cells directly and marshaling the immune system against them,” said Kevin Harrington, U.K. trial leader and professor of biological cancer therapies at the Institute of Cancer Research in London.

“It’s like an unmasking of the cancer,” said Harrington. “The patient’s immune system wakes up and attacks the cancer cells wherever they are in the body.”

The treatment has a major upside in that the side-effects are much less severe than chemotherapy.