Going 'viral' against cancer

November 4, 2015. A genetically-modified herpes virus can now be deployed at an advanced stage of melanoma, a serious form of skin cancer. The approval of this new type of cancer treatment is paving the way for an innovative form of therapy.

Innovative cancer treatment

The virus, called talimogene laherparepvec (T-VEC), primarily uses the patient's own immune system to combat cancer cells. The treatment was approved at the end of October by the European Medicines Agency and the US Food and Drug Administration (FDA). In light of this, it is the first cancer treatment with oncolytic (or cancer-fighting) viruses which may be used in Europe and the United States. 

Virus vs tumour cells

Viruses naturally tend to fight tumour cells whilst leaving most healthy cells unharmed. Mutations that develop due to the quick division of tumour cells can increase patients' susceptibility to infections. Such activity can reduce cells' antiviral reaction, for example. 
This principle has been known for centuries: examples of cancer patients who go into remission after becoming infected with a virus date back as far as the nineteenth century. In the mid-twentieth century, doctors experimented with many types of natural viruses in order to achieve a similar effect. However, some of these experiments had deadly consequences. 

Designed to cure

Having learnt from earlier developments, viruses nowadays are developed and composed with the utmost precision. This is the case for T-VEC, the ability of which to cause herpes has been drastically reduced. It cannot multiply in healthy cells. Alongside this, researchers incorporated a gene that makes the virus produce the protein GM-CSF, which stimulates the immune system. Once inside a tumour cell, the virus kills it and releases the GM-CSF and antigens. These substances activate the immune system, so that it attacks nearby tumour cells as well as others around the entire body.

Intensive research is now being carried out in order to improve the virus. Research from 2014 demonstrated that the application of the virus has more effect in combination with immunotherapy than immunotherapy alone. However, it is still necessary to inject the virus directly into the tumour. Scientists are now conducting research on how this can be applied systematically, so that it can have an effect in hard-to-reach places.

New era

Researchers hope that the approval of T-VEC will provide the much-needed financial support. Research into other viruses that are effective against other types of cancer are in full swing. 'We may have entered the era of the oncolytic virus,' says Stephen Russell, cancer researcher and haematologist at the Mayo Clinic in Rochester, Minnesota. 'I expect a lot of activity in the coming years.