The use of such “virotherapy” led to the first successful stage III trial results, opening up the possibility for a whole new raft of cancer treatments in the future.
Remarkably, the intervention was successfully used in patients who were considered to have hitherto exhausted all other treatment options.
Professor Kevin Harrington, who led the work at the Institute of Cancer Research London, said “They had disease that ranged from dozens to hundreds of deposits of melanoma on a limb all the way to patients where cancer had spread to the lungs and liver.”
Of the 400 patients who participated in the trial, 10% were considered to be in “complete remission” after coping with a herpes diagnosis. This is deemed a cure if five years after initial diagnosis the sufferer is still cancer free.
The trial involved exposing patients to a “neutered” version of the herpes virus, which was altered to prevent a protein required to infect healthy tissues from being produced. The cancerous cells then metabolized their own analogue of the blocked protein, which enabled the modified virus to flourish and reproduce within the diseased tissue.
Once cancer cells are infected with the multiplied viral agents they burst, causing further pathogens to infect the localized tissue, and triggering an immune cascade at the site of the tumor. This secondary immune response appears to enhance the body’s ability to attack the cancer, although scientists are not as yet sure why.
Malignant melanoma is diagnosed in more than 13,000 people in the UK each year, and the five-year survival rate is about 88%. However, for patients with aggressive forms of skin cancer the rate is much worse.
Timothy Turnham, executive director of the Melanoma Research Foundation, cautions that the results of T-VEC alone were “interesting but not amazing,” but when used with immune checkpoint inhibitors “the numbers you get are much, stronger.”
He suggests that a combined treatment may prove to be the best option for treating advanced melanoma treatment, especially considering the relatively mild side effects.