The "monoclonal" antibody selectively targets both early-stage and advanced tumors.
As well as attacking the disease directly, it also helps the immune system to identify and destroy cancer cells.
In addition, tagging the molecule with a radioactive marker could enable doctors to track spreading prostate cancer, revealing precisely where in the body it is growing.
Tests in mice showed that the antibody, known as F77, wiped out 85% of one type of highly aggressive prostate cancer.
Tumors allowed to grow to a large size were also dramatically reduced in volume.
Each year around 35,000 men in the UK are diagnosed with prostate cancer and 10,000 die from the disease.
Initially, spreading prostate cancer can be kept under control with therapies that prevent tumor growth being fuelled by androgen male hormones.
But eventually most prostate cancers stop being hormone-sensitive. Few treatment options are then possible and progress of the disease is rapid and lethal.
Up to 45% of patients with local prostate cancer relapse after curative treatments such as surgery and radiotherapy, and their disease begins to rapidly spread. The five-year survival rate for patients with metastatic prostate cancer is only 34%.
