A new immunotherapy drug has produced striking early results in men with advanced prostate cancer.
Researchers reported tumour shrinkage and major biomarker reductions in a phase one trial.
Prostate cancer remains the most common cancer in men in many countries.
About 1.5 million new cases occur worldwide each year.
The experimental treatment, VIR-5500, is an engineered antibody.
It links killer T-cells directly to tumour cells that try to evade the immune system.
The drug activates mainly inside the tumour, which limits widespread inflammation.
This design may reduce side effects and allow less frequent dosing.
Fifty-eight men with treatment-resistant disease received the therapy.
Most experienced only mild side effects.
Researchers measured prostate-specific antigen levels to assess response.
At the highest dose, 82% of patients saw PSA fall by at least half.
More than half recorded drops of at least 90%.
Nearly one-third showed reductions of 99%.
Tumour scans confirmed physical shrinkage in several patients.
In one case, multiple liver metastases disappeared after six treatment cycles.
Scientists described the findings as unprecedented for an “immune-cold” cancer.
Immunotherapy has previously shown limited success in prostate disease.
The results still require peer review and larger trials.
Researchers plan expanded studies to confirm safety and effectiveness.
Experts say the approach could open a new treatment class.
They also stress the need for diverse patient groups in future research.
With thousands of deaths each year, new therapies remain urgent.
Early data suggest this strategy could extend survival and improve quality of life.
