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Viral Immunotherapy for Skin Cancer Shows Patient Benefit in Phase III Trial

Genetically modified herpes virus kills melanoma cells

A genetically engineered herpes virus can halt the progression of skin cancer by killing cancer cells and by sparking the immune system into action against tumors, a landmark clinical study has shown.

It is the first time that a phase III trial of viral immunotherapy has definitively shown a benefit for patients with cancer.

The trial was led by researchers at the Institute of Cancer Research (ICR) in London and involved 64 research centers worldwide. Researchers randomly assigned 436 patients with aggressive, inoperable malignant melanoma to receive either an injection of the viral therapy, talimogene laherparepvec (T-VEC, Amgen), or a control immunotherapy.

Of the patients given T-VEC, 16.3% showed a durable treatment response of more than 6 months compared with 2.1% of those given the control treatment. Some patients had a response extending past 3 years –– a mark oncologists often use as a proxy for cure in immunotherapy.

Importantly, responses to treatment were most pronounced in patients with less-advanced cancers (stages IIIB, IIIC, or IVM1a) and in those who had yet to receive any treatment, suggesting the potential benefit of T-VEC as a first-line therapy for metastatic melanoma that cannot be surgically removed.

A total of 163 patients with stage III and early-stage IV melanoma treated with T-VEC lived an average of 41 months. This was in contrast to an average survival of 21.5 months in the 66 earlier-stage patients who received the control immunotherapy.

The trial was funded by the manufacturer of T-VEC, Amgen, and was published in the Journal of Clinical Oncology.

T-VEC is a modified form of herpes simplex virus type-1 that multiplies inside cancer cells and bursts them from within. It has been genetically engineered to produce granulocyte macrophage colony-stimulating factor (GM-CSF) molecules, which stimulate the immune system to attack and destroy the tumor.

The virus has been modified to remove two key genes, 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 defenses are compromised by genetic errors.

Professor Paul Workman, chief executive of the ICR, 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.

“In this case, we are harnessing the ability of an engineered virus to kill cancer cells and stimulate an immune response. It’s exciting to see the potential of viral treatment realized in a phase III trial, and there is hope that therapies like this could be even more effective when combined with targeted cancer drugs to achieve long term control and cure.”

Source: ICR; May 26, 2015.


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