Researchers have reported striking early results for a new prostate cancer treatment.
The experimental immunotherapy VIR-5500 shrank tumours in several patients with advanced disease.
Prostate cancer affects about 1.5 million men each year worldwide.
Many advanced cases eventually stop responding to standard therapies.
VIR-5500 works by linking killer T-cells directly to tumour cells.
The engineered antibody activates mainly inside the tumour.
This design reduces harmful inflammation and may allow fewer doses.
Fifty-eight men with treatment-resistant cancer joined the phase one trial.
Most experienced only mild side effects.
At the highest dose, prostate-specific antigen levels fell sharply in many patients.
Fourteen of seventeen men saw their PSA drop by at least half.
Nine recorded reductions of ninety percent or more.
Five achieved falls of at least ninety-nine percent.
Tumour scans also showed encouraging responses.
Five of eleven men with measurable disease had tumour shrinkage.
One patient saw multiple liver metastases disappear completely after treatment.
Researchers described the findings as unprecedented for a cancer long considered resistant to immunotherapy.
Larger trials will now test safety and long-term effectiveness.
Independent experts called the results highly promising but urged studies in more diverse patient groups.
They said the new approach could open an important treatment class and extend survival for men with advanced prostate cancer.
