Early trials of the immunotherapy drug VIR-5500 have shown remarkable results in treating advanced prostate cancer, with tumours shrinking in some patients. The drug, developed by Vir Biotechnology, is a T-cell engager that activates the immune system to attack cancer cells specifically within the tumour, minimising side effects.
In a phase one clinical trial involving 58 men with advanced prostate cancer who had stopped responding to other treatments, 88% experienced only mild side effects. Among 17 patients given the highest dose, 82% saw their prostate-specific antigen (PSA) levels drop by at least half, with 29% experiencing a fall of at least 99%.
Of 11 patients with measurable tumours, five showed shrinkage. In one case, a 63-year-old man with cancer spread to his liver had 14 cancerous lesions completely resolve after six cycles of treatment. Professor Johann de Bono of the Institute of Cancer Research and the Royal Marsden NHS foundation trust, who led the study, described the results as 'stunning' and 'unprecedented' for a cancer previously considered resistant to immunotherapy.
The findings, presented at the American Society of Clinical Oncology genitourinary cancers symposium, have not yet been peer-reviewed. Further clinical trials are being planned. Experts have called for larger studies and testing across diverse ethnic groups to address disparities in prostate cancer outcomes.
