Researchers have reported encouraging early results for a new prostate cancer treatment.
The experimental drug VIR-5500 shrank tumours in some men with advanced disease.
Prostate cancer affects about 1.5 million men worldwide each year.
Immunotherapy has transformed several cancers but rarely benefits prostate tumours.
VIR-5500 uses engineered antibodies to link killer T-cells to cancer cells.
The drug activates mainly inside tumours, which reduces harmful inflammation.
This design may also allow fewer treatment doses.
Scientists tested the therapy in 58 men who no longer responded to standard care.
Most participants experienced only mild side effects.
At the highest dose, PSA levels dropped by at least half in 82% of patients.
More than half recorded reductions of at least 90%.
Nearly one third saw PSA levels fall by 99%.
Five of eleven men with measurable disease showed visible tumour shrinkage.
One patient had multiple liver lesions disappear after six treatment cycles.
Researchers called the findings unprecedented for an immune-resistant cancer.
They plan larger trials to confirm safety and long-term benefit.
Independent experts described the results as highly promising.
They stressed the need for broader studies across diverse patient groups.
New treatments remain urgent, as thousands still die from the disease each year.
