A new immunotherapy drug has delivered encouraging results for men with advanced prostate cancer. Early data show tumour shrinkage in several patients who had exhausted other treatments.
Prostate cancer remains the most common cancer among men in countries such as the US and UK. Around 1.5 million men receive a diagnosis worldwide each year.
Researchers tested an experimental drug called VIR-5500 in a phase one clinical trial. The treatment belongs to a class known as T-cell engagers. These drugs direct the body’s immune T-cells to attack cancer cells.
Professor Johann de Bono from the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust led the study. He explained that VIR-5500 activates only within the tumour environment. This design aims to reduce harmful side-effects and allow the drug to remain longer in the bloodstream.
Fifty-eight men with advanced prostate cancer took part in the trial. All participants had stopped responding to standard therapies. Most patients, 88%, experienced only mild side-effects.
Researchers monitored prostate-specific antigen (PSA) levels in the blood. Falling PSA levels often signal a positive treatment response. Among 17 men who received the highest dose, 82% saw PSA levels drop by at least half. More than half recorded reductions of 90% or greater. Nearly a third experienced drops of at least 99%.
In patients whose tumours could be measured, five out of eleven showed visible shrinkage at the highest dose. One 63-year-old man with cancer spread to his liver saw 14 lesions completely disappear after six treatment cycles.
Scientists described the findings as remarkable for a disease long considered resistant to immunotherapy. The results were presented at the American Society of Clinical Oncology genitourinary cancers symposium and have not yet undergone peer review.
Experts welcomed the development but urged caution. They stressed the need for larger, diverse clinical trials to confirm safety and effectiveness. With more than 12,000 men dying from prostate cancer each year in the UK alone, researchers say innovative treatments remain urgently needed.
