A small-scale clinical, presented by scientists from the University of Leeds at the annual meeting of the American Society for Clinical Oncology, revealed the potential of a virus to treat some advanced cancers. The specifically-engineered virus was able to infiltrate tumour cells, begin to destroy them and also boost the body’s immune system.
The study looked at the effectiveness of the virus in treating eight patients with cancers that had spread: three were suffering from skin cancer or melanoma and five had bowel cancer, which had spread to the liver. In one case the patient’s tumour disappeared – and in another, the tumour reduced in size.
“The results so far are very promising. They show the virus was very effective in being able to switch on the body’s immune system, allowing a patient’s own defence systems to target the cancer,” said Dr Adel Samson from the Leeds Institute of Cancer and Pathology and also one of the investigators. “In addition, there was evidence that the virus itself was also destroying the tumour cells.”
The virus was looked at as a neoadjuvant therapy, meaning it was used to try and shrink a tumour ahead of surgery. Called Pexa-Vec, the virus was derived from the Vaccinia family of viruses and modified to target cancer cells.
Administered intravenously two weeks before the surgery, the analysis of the cancerous tissue showed that the virus had been able to reach the site of the tumours and infiltrate the cancer cells and in some cases the cancer cells even started to die.
“In two of the patients, we saw prior to administration of the virus that they had tumours that were growing. When the tumours were examined following surgery, the pathologist could identify dead cancer cells. Further research is needed to understand why the virus was so effective with these patients. We need to understand whether what we saw was the result of the virus destroying the cancer cells, or was it the result of the virus enabling the immune system to be more effective – or was it a combination of the two,” explained Dr Samson.
The trial was run in partnership with Transgene, a French biotech company, and the effectiveness of Pexa-Vec is currently being tested in a larger phase-three clinical trial that involved patients with liver cancer. During the trial, doctors will try to determine whether the virus is a more effective treatment than giving the conventional drug therapy.