A new immunotherapy drug has produced striking early results in men with advanced prostate cancer.
Researchers say the treatment, called VIR-5500, shrank tumours in several patients.
Prostate cancer is the most common cancer in men in many countries.
Around 1.5 million men receive the diagnosis worldwide each year.
The drug works by linking killer T-cells directly to tumour cells.
This forces the immune system to attack cancers that usually evade detection.
The therapy activates mainly inside the tumour, which limits side effects.
It also remains in the bloodstream longer, so patients may need fewer doses.
Fifty-eight men joined the phase one trial after other treatments failed.
Eighty-eight percent reported only mild side effects.
Researchers analysed prostate-specific antigen levels to measure response.
Among patients receiving the highest dose, most showed dramatic declines.
PSA levels fell by at least half in eighty-two percent of these men.
More than half recorded a drop of ninety percent or greater.
Some experienced reductions close to complete disappearance.
Tumour scans confirmed physical shrinkage in several cases.
One patient with liver spread saw fourteen lesions vanish after treatment.
Scientists described the results as unprecedented for this disease.
Prostate cancer has long resisted immunotherapy approaches.
The findings still require larger and more diverse trials.
Experts say the therapy could open a new treatment class.
They hope it will extend survival and improve quality of life for patients.
