How herpes virus could fight cancer

Scientists have made a number of significant breakthroughs in these treatments " with some immunotherapy drugs shown to be twice as effective as chemotherapy for specific cancers.

Scientists have made a number of significant breakthroughs in these treatments " with some immunotherapy drugs shown to be twice as effective as chemotherapy for specific cancers.

Published May 27, 2015

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London - Scientists have the first proof that an entirely new way of combating cancer, using genetically modified viruses to attack tumour cells, can benefit patients.

The discovery paves the way for a wave of new potential treatments over the next decade.

Specialists at the NHS Royal Marsden Hospital and the Institute of Cancer Research (ICR) confirmed that melanoma skin cancer patients treated with a modified herpes virus had improved survival prospects - a world first.

In some patients, the improvements were striking. Although all had aggressive, inoperable malignant melanoma, those treated with the virus therapy - known as T-VEC - at an earlier stage survived on average 20 months longer than patients given an alternative.

In other patients results were more modest, but the study represents a landmark: it is the first, large, randomised trial of a so-called oncolytic virus - one that targets cancer - to show success. Cancer scientists predict it will be the first of many in the coming years.

The method - known as viral immunotherapy - works by launching a “two-pronged attack” on cancer cells. The virus is genetically modified so that it can't replicate in healthy cells - meaning it homes in on cancer cells. It multiplies inside the cancer cells, bursting them from within. At the same time, other genetic modifications to the virus mean it stimulates the body's own immune response to attack and destroy tumours.

Other forms of immunotherapy - the stimulation of the body's own immune system to fight cancer - using antibodies rather than viruses, have been developed into successful drugs. It is hoped that T-VEC could be used in combination with these.

Findings from trials of T-VEC, which is manufactured by the US pharmaceutical company Amgen, have already been submitted to drugs regulators in Europe and the US.

Viral immunotherapies are also being investigated for use against advanced head and neck cancers, bladder cancers and liver cancers.

Kevin Harrington, UK trial leader and professor of biological cancer therapies at the ICR and an honorary consultant at the Royal Marsden, said he hoped the treatment could be available for routine use within a year in many countries, although it would need to pass the UK's regulatory approval before it could be prescribed here.

“I hope, having worked for two decades in this field, that it really is the start of something really exciting,” said Professor Harrington. “We hope this is the first of a wave of indications for these sorts of [cancer fighting] agents that we will see coming through in the next decade or so.”

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.”

The study, published in the Journal of Clinical Oncology, included 436 patients, all with aggressive, inoperable malignant melanoma. More than 16 percent of patients were responding to treatment after six months, compared with 2.1 percent who were given a control treatment. Some patients were still responding to treatment after three years.

The therapy could avoid the need for gruelling chemotherapy or radiotherapy. Researchers behind the study said its side-effects were milder than other therapies for advanced cancer.

Alan Melcher, professor of clinical oncology and biotherapy at the University of Leeds, and an expert in oncolytic viruses, said the field had accelerated quickly in recent years.

“They were first developed to go in and kill cancer cells but leave other cells unharmed. What's become clear is that these viruses may do that but what is probably more important is that they work by stimulating an immune response against cancer,” he said. “Immunotherapy looks promising and big pharmaceutical companies are now involved.”

Dr Hayley Frend, science information manager at Cancer Research UK, said the potential for viruses in future cancer treatments was “exciting”. “Previous studies have shown T-VEC could benefit some people with advanced skin cancer but this is the first study to prove an increase in survival. The next step will be to understand why only some patients respond to T-VEC, in order to help better identify which patients might benefit from it,” she said.

Melanoma is the fifth-most common cancer in the UK, and is becoming more widespread as a result of increased exposure to the sun in younger generations who have benefited from easier access to sunnier climates on holiday. Survival chances are good if the cancer - indicated by the appearance of a new mole on the skin - is caught early.

However, if left alone, the tumour can become inoperable, and 2 000 people still die from melanoma in the UK every year.

 

Q&A: USING ONCOLYTIC VIRUSES TO FIGHT CANCER

QUESTION: How can a virus fight cancer?

ANSWER: Viruses are good at infecting and killing human cells - that is what makes some of them so dangerous. Gene technology means that scientists can now manipulate viruses to behave in certain ways - in this case, to only infect and attack cancer cells, bursting them from the inside. These are called oncolytic viruses - from the Greek for “tumour” and “loosening”.

 

Q Why was a herpes virus used?

A There is nothing intrinsic about the herpes virus that makes it a good cancer fighter. However, scientists have used the virus in labs for decades and understand a great deal about its structure - making it a good candidate for genetic modification.

 

Q Will oncolytic viruses work against all cancers?

A We only have definitive findings from this ICR/Royal Marsden study in melanoma skin cancer patients. However, the theory should apply to other tumour types, and scientists are confident similar treatments for head and neck, bladder and liver cancers could emerge.

 

 

Q Are cancer-fighting viruses our best chance of beating the disease?

A The most likely scenario is that these treatments will take their place alongside the growing range of drugs and therapies being developed. This is a time of rapid progress in cancer treatment, with our greater understanding of the genetics of cancer fuelling a wave of new discoveries. However, we also know that cancers vary hugely from one to the other, so the idea of one “silver bullet” cure for cancer is no longer considered a realistic prospect.

Q How can I avoid developing melanoma?

A It is not always preventable but you can lower your risk by limiting exposure to UV light - avoid sunbeds, wear sunscreen, and check moles and freckles for any changes.

 

The Independent

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