Genetically engineered herpes virus capable of halting skin cancer

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Phase III of a viral immunotherapy wherein genetically engineered herpes virus were used against skin cancer has shown promising results with the herpes virus able to halt the progression of skin cancer by killing cancer cells and sparking the immune system into action against tumours.

The trial was led in the UK by researchers at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, and involved 64 research centres worldwide including the University of Oxford. 436 patients with aggressive, inoperable malignant melanoma randomly received either an injection of the viral therapy, called Talimogene Laherparepvec, or a control immunotherapy.

Of all the patients who received Talimogene Laherparepvec — known as T-VEC — 16.3 per cent showed a durable treatment response of more than six months, compared with 2.1 per cent given the control treatment. Some patients had a response extending past three years, a mark oncologists often use as a proxy for cure in immunotherapy.

The findings also underlined potential benefits of T-VEC as the response to treatment were most pronounced in patients with less advanced cancers (stage IIIB, IIIC, IVM1a) and those who had yet to receive any treatment.

Those with stage III and early stage IV melanoma treated with T-VEC — a total of 163 people — lived an average of 41 months. This compared with an average survival of 21.5 months in the 66 earlier-stage patients who received the control immunotherapy.

Talimogene Laherparepvec – T-VEC

Talimogene Laherparepvec aka T-VEC is a modified form of herpes simplex virus type-1, which multiplies inside cancer cells and bursts them from within. Researchers genetically engineered the virus to produce a molecule called GM-CSF, which stimulates the immune system to attack and destroy the tumour. T-VEC is the first of a new wave of virus-based drugs which have shown benefits in major randomised, controlled phase III trial.

Researchers have engineered the virus and removed two key genes, called ICP34.5 and ICP47, so that it can’t replicate within healthy cells. Normal cells detect and destroy T-VEC before it can cause damage — but it replicates easily in cancer cells because their infection defences are compromised by genetic errors.

Owing to their capability to launch two-pronged attack on tumours, viral treatments like T-VEC are increasingly being considered as one of the top candidates as potential for treatment of cancers and other such diseases. Further, as these engineered viruses only target specific cells – in this case cancer cells – they tend to have fewer side-effects than traditional chemotherapy or some of the other new immunotherapies.

“Our study showed that T-VEC can deliver a significant, durable benefit for people with melanoma. It is encouraging that the treatment had such a clear benefit for patients with less advanced cancers – ongoing studies are evaluating if it can become a first-line treatment for more aggressive melanomas and advanced disease”, said UK trial leader Professor Kevin Harrington, Professor of Biological Cancer Therapies at The Institute of Cancer Research, London, and Honorary Consultant at The Royal Marsden NHS Foundation Trust.

Professor Paul Workman, Chief Executive of The Institute of Cancer Research, London, said: “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”.