A new immunotherapy treatment has produced striking early results in men with advanced prostate cancer.
Researchers reported that the drug VIR-5500 shrank tumours in several patients during a phase one trial.
Prostate cancer remains the most common cancer in men in many countries.
About 1.5 million new cases appear worldwide each year.
VIR-5500 works by linking killer T-cells directly to tumour cells.
This approach helps the immune system recognise and destroy cancer.
The drug activates mainly inside the tumour, which reduces harmful side effects.
Fifty-eight men whose disease no longer responded to standard therapies received the treatment.
Most participants experienced only mild side effects.
Among patients given the highest dose, many showed major biological responses.
PSA levels fell by at least half in most of these men.
Several recorded drops of more than ninety percent.
Doctors also observed measurable tumour shrinkage in some patients.
One man with liver metastases saw multiple cancerous lesions disappear after treatment cycles.
Researchers called the findings unprecedented for a cancer long considered resistant to immunotherapy.
They cautioned that larger and more diverse trials are still required.
Scientists and charities welcomed the results as highly encouraging.
They hope the new therapy will extend survival and improve quality of life for men with advanced disease.
