World first as scientists use cold sore virus to
attack cancer cells
Using genetically modified viruses to
attack tumour cells could open a 'wave' of potential new treatments
Wednesday, 27 May
2015
Scientists have the
first proof that a “brand new” way of combating cancer, using genetically
modified viruses to attack tumour cells, can benefit patients, paving 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 (the virus that
causes cold sores) had improved survival – 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 to show success.
Cancer scientists predict it will be the
first of many in the coming years – adding a new weapon to our arsenal of
cancer treatments.
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 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 American pharmaceutical company Amgen, have already been
submitted to drugs regulators in Europe and the USA.
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
own 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, which is published in the
Journal of Clinical Oncology, included 436 patients, all of whom had
aggressive, inoperable malignant melanoma. More than 16 per cent of patients
were responding to treatment after six months, compared to 2.1 per cent who
were given a control treatment.
Some patients were still responding to
treatment after three years.
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.
“The field has moved very quickly
clinically. Immunotherapy looks promising and big pharmaceutical companies are
now involved. Amgem have bought this virus and the reality is, when the big
companies get involved things move a lot more quickly.”
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 benefitted 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.
Cancer Q&A
How can a virus
fight cancer?
Viruses are good at infecting and killing
human cells – that’s what makes some of them so dangerous. Genetic 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’.
Why was a herpes
virus used?
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.
Will oncolytic
viruses work against all cancers?
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 that similar
treatments for head and neck, bladder and liver cancers could emerge in the
coming years.
How soon will the
new treatment be available?
The therapy used here, known as T-VEC
(short for Talimogene Laherparepvec) is already being looked at by regulators
at the US Food and Drug Administration, and the European Medicines Agency
(EMA). Scientists hope that it could be rubber-stamped as a treatment for
advanced melanoma within the next 12 months. If it gets EMA approval, it would
then need to go through NICE approval, or be included on the Cancer Drugs Fund
list, before it could be prescribed in the UK.
Are cancer-fighting
viruses our best chance of beating the disease?
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 very rapid progress in cancer
treatment, with our greater understanding of the genetics of cancer fuelling a
raft of 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.
How can I avoid
developing melanoma?
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.
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