US approves modified-virus cancer treatment

The US Food and Drug Administration has approved a drug derived from a genetically modified herpes virus for the treatment of melanoma that cannot be removed by surgery.

Imylgic (chemical name talimogene laherparepvec), manufactured by Amgen, is the first oncolytic viral therapy to receive regulatory approval.

The drug works by invading and replicating within cancer cells, eventually causing them to burst — a natural ability of the herpes virus.

But the modified virus also carries with it a gene fragment encoding a protein called granulocyte-macrophage colony stimulating factor (GM-CSF). When produced by the virus, this stimulates the patient's immune system to recognise and destroy cancer cells.

The modified virus is also able to travel in the patient's bloodstream and infect other tumour cells. It can also enter healthy cells but is unable to replicate within them, thus sparing them.

Imlygic's approval follows the outcome of a multicentre, randomised, phase 3 clinical trial involving 436 patients. Patients in the study were treated over a six-month period with either Imlygic or GM-CSF injected directly into the melanoma lesions.

The study showed a reduction in lymph node lesion size in 16.3 percent of the patients treated with Imlygic compared to 2.1 percent in the GM-CSF arm. The effect of the drug and overall survival was largest in patients with unresectable melanoma that had not spread beyond the skin and lymph nodes.

But the study showed the drug had no benefit for patients with melanoma that had spread to the brain, lungs and other internal organs.

The European Medicines Agency has also recommended the drug for approval, setting the stage for marketing authorisation in Europe.

Melanoma is an aggressive form of skin cancer and a leading cause of death from skin disease. Ultraviolet light and unprotected sun exposure are the main risk factors. When detected early, melanoma can be removed surgically but the prognosis is poor for the more advanced stage of the disease, particularly when cancer cells have metastasized to other parts of the body.

'As an oncolytic viral therapy, Imlygic has a unique approach, and provides another option for treating eligible patients with unresectable disease that has recurred after initial surgery' said Professor Howard Kaufman, from the Rutgers Cancer Institute of New Jersey, principal investigator in the Imlygic trial.

There are at least six biotechs and research groups working on oncolytic viruses and about a dozen clinical trials currently ongoing, meaning Imlygic may be the first of many to emerge.

'The era of the oncolytic virus is probably here,' Dr Stephen Russell, a specialist from the Mayo Clinic in Rochester, Minnesota told Nature News. 'I expect to see a great deal happening over the next few years.'