Early trials of a new immunotherapy drug for advanced prostate cancer have shown promising results, with tumours shrinking in some patients. The drug, VIR-5500, is a T-cell engager that activates the body's immune system specifically within tumours, minimising side-effects.
In a phase one clinical trial funded by Vir Biotechnology, 58 men with advanced prostate cancer who had stopped responding to other treatments were given VIR-5500. The majority (88%) experienced only very mild side-effects. Among 17 men given the highest dose, 82% saw their PSA level fall by at least half, 53% by at least 90%, and 29% by at least 99%.
Prof Johann de Bono of the Institute of Cancer Research and the Royal Marsden NHS foundation trust, who led the work, described the results as unprecedented for a disease previously thought to be resistant to immunotherapy. He said: “We believe that such treatments may in the long term lead to cures.”
Of 11 patients given the highest dose with measurable tumours, five showed tumour shrinkage. In one case, a 63-year-old man with cancer spread to his liver had 14 cancerous liver lesions completely resolve after six cycles of treatment. The results were presented at the American Society of Clinical Oncology genitourinary cancers symposium in San Francisco and have not yet been peer-reviewed.
Simon Grieveson, assistant director of research at Prostate Cancer UK, said the early-phase trial was exciting, adding: “With over 12,000 men dying from prostate cancer each year in the UK, we urgently need new and innovative ways to treat the disease.” Further clinical trials are now being planned.
