Immunotherapy is used a lot right now due to its approach of tapping into the power of the body’s own immune system to fight cancer. Many of these treatments are being trialed on their own or are being used with standard treatments like chemotherapy, to improve the survival of patients.
“Immunotherapy is a very big and active area right now, especially with checkpoint inhibitors,” said Professor Alan Melcher, a Cancer Research UK-funded expert in virus cancer therapies at The Institute of Cancer Research, London.
It is now being tested whether viruses could lend a hand in the effort to destroy cancer. Oncolytic viruses are capable of infiltrating and destroying cancer cells, and one called, T-VEC is a modified version of the herpes virus. It has already been approved for use melanoma.
Viruses are very good at provoking an immune response within the body so researchers want to manipulate this ability for patients with ‘cold’ tumours. Not everyone that receives immunotherapy reacts in the same way. Patients that have ‘hot’ tumours react the best, as they already have some immune response, whilst ‘cold’ tumours have very little response.
The study by scientists from Johnson Comprehensive Cancer Centre in Los Angeles and published in Cell, involved 21 patients with advanced melanoma. They received an injection of T-VEC straight into the tumour site which was followed by treatment with the immunotherapy drug pembrolizumab (Keytruda).
Pembrolizumab uses monoclonal antibodies that block the PD-1/PDL-1 interaction between immune cells and tumours. With this blocked, the tumour cells can no longer evade detection from the immune system.
Tumours in 13 patients responded to the combined treatment, more than would be expected with either treatment individually. 7 patients were deemed to have a complete response, meaning their disease was undetectable 4 weeks after treatment.
Melcher said “They also see that there’s an increase in the ‘heat’ of the tumour when the virus is used – in line with the idea that the virus makes the tumour more susceptible to the immunotherapy,”
Lead author Dr Antoni Ribas said: “We had a hypothesis about how these treatments would work together, and when we did biopsies of patients’ tumors we found that they were cooperating in just the way we thought they would.”
After the virus infiltrates the cancer cell, it multiplies till it erupts, releasing antigens that will attract immune cells. With the PD-1/PDL-1 interaction blocked by Pembrolizumab, the immune system can release havoc on the tumour. An amazing duo in action.
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