Researchers have reported encouraging early results from a trial of a new immunotherapy drug, VIR-5500, for advanced prostate cancer, with some patients experiencing significant tumour shrinkage.
Prostate cancer is the most common cancer among men in many countries, including the United States and the United Kingdom, with about 1.5 million diagnoses worldwide each year.
While immunotherapy has transformed treatment for several cancers, it has had limited success in prostate cancer, which has often been described as resistant to such approaches.
The phase one clinical trial, funded by Vir Biotechnology, involved 58 men whose cancer had stopped responding to other treatments. Led by Professor Johann de Bono of the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, the study tested VIR-5500, an engineered antibody designed to link the body’s killer T cells to tumour cells.
The drug activates within the tumour, reducing side effects and allowing it to remain longer in the bloodstream.
Among 17 men who received the highest dose, 82 percent saw their prostate-specific antigen levels fall by at least half, while 53 percent recorded a drop of at least 90 percent.
Five patients experienced reductions of at least 99 percent.
Of 11 patients with measurable tumours at the highest dose, five showed tumour shrinkage.
In one case, a 63-year-old man with cancer that had spread to his liver saw 14 lesions completely resolve after six treatment cycles.
Most participants experienced only mild side effects.
The findings, presented at the American Society of Clinical Oncology genitourinary cancers symposium in San Francisco, have not yet been peer reviewed. Further trials are planned.