A genetically modified cold sore virus could be be made available as a game-changing new treatment for deadly skin cancer within a year, scientists claim.
Extraordinary results from a Phase III trial involving patients with aggressive, inoperable disease have shown that the therapy can eradicate tumours and halt their growth.
The unique treatment combines a direct targeted attack on cancer cells with an immunotherapy approach that primes the body’s own defences to combat the disease.
Of the 26% of patients who responded to the herpes virus treatment, known as T-Vec, one in 10 saw their tumours vanish without trace.
Another 16% of responding patients experienced a “partial remission” that reduced the size of their tumours by more than 50%.
Professor Kevin Harrington, from the Institute of Cancer Research in London, led the international Phase III trial conducted in the UK, US, Canada and South Africa.
He said: “It’s not an exaggeration to say this is a first-in-class agent, an entirely new type of anti-cancer treatment.
“There will have to be discussions about cost effectiveness but we hope to see this agent receive approval in about the next 12 months, making it possible to prescribe it for cancer.”
T-Vec is one of a new generation of virus-based drugs in development and the first to show real potential in a major Phase III trial, the last step before a new medicine is licensed and made available to patients.
It contains the same herpes simplex type-1 virus that causes cold sores, genetically engineered to make it harmless to patients but lethal to cancer.
The virus is unable to multiply in healthy skin cells but finds fertile ground for growth in tumour cells. Eventually the virus proliferates to such an extent that it literally explodes out of the cancer cells, destroying them.
At the same time, the GM virus produces a molecule called GM-CSF which acts as a potent immune system stimulator.
This has the effect of priming the immune system to recognise and attack tumour proteins left in the debris of the obliterated cancer cells. Thereafter the immune system continues to target the same proteins when they are “flagged up” by returning cancer, providing protection against the disease.
How long the immunity lasts is not known, but some patients have remained in remission — either cancer free or experiencing no further tumour growth — for as long as three years.
Prof Harrington said: “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.
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