Herpes virus genetically engineered to destroy skin cancer cells
A new study has pointed to a chink in the armor of skin cancer cells, suggesting that they can be overpowered by the body's own system with help from a pioneering approach known as viral therapy. A clinical trial has demonstrated that a genetically engineered herpes virus can not only plant itself in the cancer cells and kill them off, but activate the body's own immune system to stave off harmful tumors.
The clinical trial was conducted across 64 research centers around the world and led by The Institute of Cancer Research in London. It saw 436 patients suffering from inoperable skin cancers treated with a modified form of herpes virus called Talimogene Laherparepvec (T-VEC).
Scientists arrived the design for T-VEC by removing two key genes from the herpes virus. This step was all-important as it prevents the drug from replicating with normal healthy cells and allows them to detect and destroy it before it causes harm. Meanwhile, it replicates with ease in cancer cells whose genetic errors give rise to weaker defences against infections.
The result is a genetically engineered virus with the ability to grow in cancer cells and blow them up from the inside. What's more, T-VEC is also designed to produce a molecule known as GM-CSF that moves the body's immune system to destroy tumors, forming something of a two-pronged attack.
Some of the 436 patients where treated with injections of T-VEC, while others were given a control immunotherapy. Around 16 percent of those given T-VEC demonstrated durable responses of more than six months, compared to just over two percent of those given the control drug. Some subjects had a response that went beyond three years.
The researchers found the drug to be most effective when used in the less advanced stages of the cancer, suggesting that T-VEC could prove a valuable early treatment option for skin cancers that are unable to be removed by a surgeon. Patients with stage III and early stage IV melanoma, a condition that was shown to carry an average survival of 21.5 months when treated with just immunotherapy, survived an average of 41 months when treated with T-VEC.
The scientists say that T-VEC is the first of such viral therapies to be proven beneficial in treating melanoma in a phase III clinical trial. The drug has been submitted to both the US Federal Drug and Food Administration and the European Medicines Agency for consideration, with the scientists hopeful of winning approval later this year.
The findings were published in the Journal of Clinical Oncology.
You can hear from the one of the study's lead researchers, Professor Kevin Harrington, in the video below.
Source: The Institute of Cancer Research