A new drug based on a genetically modified herpes virus has been used to successfully treat patients with aggressive cases of skin cancer — and it's hoped it could be used to treat other forms of cancer too.
The new treatment uses a form of the herpes virus which is modified so that it doesn't produce the protein which allows it to attack healthy cells. But cancer cells produce their own version of the same protein, so when the two combine the herpes virus can infect the cancerous cells. From there, the herpes virus multiplies inside the cancer cells — until they eventually burst open, spilling the virus into the surroundings, allowing the effect to bring about a second wave of cancer killing. And so the process continues.
In a phase-three trial — the final stage of testing for drugs on large groups of patients — the technique, known as T-VEC, has been show to work. Working with 400 patients with "aggressive" cases of skin cancer, researchers injected the virus into the site of the skin cancer. They have shown that 25 per cent responded to the treatment and 10 per cent showed no signs of remaining cancer. Across all the participants, those treated with T-VEC lived an average of 41 months; those in a control arm lived just 21.5 months. The results, published in the Journal of Clinical Oncology, are the first time this kind of virus therapy has been shown to help treat cancer in a phase-three trial.
A particularly interesting finding of the study is that once the cancer cells begin to die, the body's immune system appears to be kickstarted too. The researchers have noticed that cancers elsewhere in the body are detected and attacked more effectively by the body's own immune system — and not the drug — once T-VEC has begun to work its magic. It's not yet clear why this happens, but the recent trial certainly shows it to be the case: secondary tumours in some patients were seen to shrink or even disappear.
The drug has already been submitted to the FDA and European Medicines Agency for approval and the researchers hope that it could be available for use in US patients by 2017. Scientists are already investigating how the same drug could be used to treat head and neck cancers. [Journal of Clinical Oncology via Guardian]