Imlygic programs viruses to attack only cancer cells and gives patients more humane options – potentially ‘a complete change in the game’ in treatment

A new cancer treatment strategy is on the horizon that experts say could be a game-changer and spare patients the extreme side effects of existing options such as chemotherapy.

Chemotherapy and other current cancer treatments are brutal, scorched-earth affairs that work because cancer cells are slightly – but not much – more susceptible to the havoc they wreak than the rest of the body. Their side effects are legion, and in many cases horrifying – from hair loss and internal bleeding to chronic nausea and even death.

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But last week the Food and Drug Administration (FDA) for the first time approved a single treatment that can intelligently target cancer cells while leaving healthy ones alone, and simultaneously stimulate the immune system to fight the cancer itself.

The treatment, which is called T-VEC (for talimogene laherparepvec) but will be sold under the brand name Imlygic, uses a modified virus to hunt cancer cells in what experts said was an important and significant step in the battle against the deadly disease.



It works by introducing a specially modified form of the herpes virus by injection directly into a tumour – specifically skin cancer, the indication for which the drug has been cleared for use.

It was developed by the Massachusetts-based biotech company BioVex, which was acquired in 2011 by biotech behemoth Amgen for $1bn. The genetic code of the virus – which was originally taken from the cold sore of a BioVex employee – has been modified so it can kill only cancer cells.



Cancer-hunting viruses have long been thought of as a potential source of a more humane and targeted treatment for cancer. Unlike current oncological treatments like chemotherapy and radiotherapy, which kill cancer cells but also damage the rest of the body, viruses can be programmed to attack only the cancer cells, leaving patients to suffer the equivalent of just a day or two’s flu.



Treatments such as Imlygic have two modes of action: first, the virus directly attacks the cancer cells; and second, it triggers the body’s immune system to attack the rogue cells too once it detects the virus’s presence.



Dr Stephen Russell, a researcher at the Mayo Clinic who specialises in oncolytic virotherapy – as these treatments are known – says that the FDA’s clearance of Imlygic represents “a huge milestone” in cancer treatment development.



Viruses are “nature’s last untapped bioresource”, Russell said. Imlygic itself has an officially fairly modest effect coming out of its clinical studies – an average lifespan increase of less than five months. But underneath that data, Russell said anecdotally that in his Mayo clinic studies in mice, some programmable viruses saw “large tumours completely disappearing”.



The goal, he said, was to get to the point where the clinical trials would see similarly dramatic outcomes, so that chemotherapy and radiotherapy could finally be consigned to medical history.



John Bell, a researcher into viral cancer therapies at the Ottawa Hospital Research Institute in Ottawa, Canada, said that while T-VEC was designed to be directly injected into a tumour – as opposed to being delivered to the whole body as a systemic treatment would be – the results showed systemic effects in some cases.



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What appears to be happening, Bell said, is that the body’s immune system seems to “wake up” to the presence of all tumours in the body, even those that were not injected with the virus. Scientists don’t yet know why, Bell said.



Some of the treatments use a modified version of measles, rather than herpes, as a vehicle. Both Russell and Bell pointed to a trial participant of Russell’s named Stacy Erholtz, whose incurable myeloma – blood cancer – disappeared, largely side effect free, in 36 hours after a treatment using a modified measles virus, an example of the kind of miraculous results that viral oncology researchers hope to replicate.

Of course, individual success stories like Erholtz’s are relatively meaningless without the hard data that come with replicable and repeated clinical trials. There are currently a number of similar treatments at the third stage of clinical testing – still several years of work behind Imlygic in terms of development – but progress is being made.



Russell is hopeful that Imlygic represents “a first step in the direction of a complete change in the game” in how we treat cancer. “We can’t prematurely claim that we’ve achieved our ultimate goal, because we haven’t; this really is a single step along that path,” he said. “But it’s a very important and very significant step.”

