Cold sore virus 'can target skin cancer'
27th May 2015 – Scientists say a genetically modified version of the herpes virus is a potential treatment for malignant melanoma, the most dangerous type of skin cancer.
The viral immunotherapy, called Talimogene Laherparepvec, or T-VEC for short, is a genetically engineered version of the herpes simplex virus that normally causes cold sores.
Two-pronged attack on cancer
In its modified form it is capable of launching a twin-assault against cancer tumours.
Two key genes are removed from the virus so that it cannot replicate inside normal cells. However, it is able to multiply within cancer cells because these cells are genetically damaged and cannot mount an adequate defence against infection.
The result is that the modified herpes virus multiplies inside the cancer cells, bursting them apart. At the same time, it produces a molecule that stimulates the body's immune system to attack and destroy cancer cells.
A research team involving the Institute of Cancer Research in London and The Royal Marsden NHS Foundation Trust say it is the first time that a large, randomised trial of viral immunotherapy has been shown to be a viable treatment for patients with cancer.
The study involved 436 patients with aggressive, inoperable malignant melanoma drawn from 64 centres in the UK, US, Canada and South Africa. The participants were randomly assigned to either have an injection of T-VEC or another type of treatment.
Patients with less advanced melanoma who were treated with T-VEC lived an average of 41 months compared with an average survival of 21.5 months among those who received the alternative treatment.
The scientists say another important discovery is that the best results were seen among patients with less advanced cancers or those who had not yet received other treatments. They say this suggests that viral immunotherapy could be a viable 'first line' treatment for inoperable skin cancer.
The phase III trial was paid for by the manufacturer of T-VEC, Amgen, and is published in the Journal of Clinical Oncology.
In a statement, UK trial leader Professor Kevin Harrington, professor of biological cancer therapies at The Institute of Cancer Research and honorary consultant at The Royal Marsden NHS Foundation Trust, says: "There is increasing excitement over the use of viral treatments like T-VEC for cancer, because they can launch a two-pronged attack on tumours – both killing cancer cells directly and marshalling the immune system against them. And because viral treatment can target cancer cells specifically, it tends to have fewer side-effects than traditional chemotherapy or some of the other new immunotherapies.
Professor Paul Workman, chief executive of The Institute of Cancer Research, says in a statement: "We may normally think of viruses as the enemies of mankind, but it’s their very ability to specifically infect and kill human cells that can make them such promising cancer treatments. In this case we are harnessing the ability of an engineered virus to kill cancer cells and stimulate an immune response.
"It’s exciting to see the potential of viral treatment realised in a phase III trial, and there is hope that therapies like this could be even more effective when combined with targeted cancer drugs to achieve long term control and cure."