This clinical trial is for men with advanced prostate cancer that may have spread to other parts of the body.

Currently, once prostate cancer cells have spread from the prostate to other organs it becomes an incurable condition. The purpose of this study is to treat patients with an experimental antibody  (i.e. that has not been FDA approved) called J591 that attaches itself to a special protein on cancer cells called PSMA to try to eliminate these cancer cells (called circulating tumor cells) from the circulation.

In the initial phase of the study, 6 participants will receive the experimental J591 treatment.  Routine blood tests, research blood tests, physical exam will be performed at each visit.  Participants will also be asked to complete a questionnaire about how they are feeling.  Participants will have a radiographic scan every 3 months to check the status of their disease.

Participants who tolerate the treatment well may be re-treated at the same level every 3 months, and may continue on treatment as long as they are responding to therapy and not experiencing unacceptable side effects.