10 patients will be enrolled in the initial cohort and will receive two infusions of unlabeled huJ591 on days 1 and 14. 89Zr-J591 will be administered on day 21 (+ 1 day) and a positron emission tomography-computed tomography (PET/CT) will be performed week later on day 28 + 1 (visit 4). Approximately 2 to 3 weeks after the 2nd dose of J591, the patient will undergo radical prostatectomy with or without lymph node dissection (day 31 + 4 days). The final visit for the study will include a postoperative visit two weeks following surgery.

This is an open-label, single center pilot study to evaluate the efficacy of huJ591 to trigger antibody-dependent cellular cytotoxicity (ADCC) response manifested by a peri-tumoral inflammatory response with or without apoptosis of prostate cancer cells in patients diagnosed with either high or intermediate-risk prostate cancer. To participate the patients will be required to meet all eligibility criteria. Patients may not participate in other clinical trials while undergoing therapeutic treatment.

The initial screening period (up to 28 days prior to start of treatment under this clinical trial) consists of visit to confirm eligibility, discuss the risks / benefits of participating in the trial and radical prostatectomy (with or without lymph node dissection), and obtain patient prostate biopsy samples for anti-prostate specific membrane antigen (PSMA) expression review. An enrolled subject's participation in the study entails approximately 6 to 7 weeks of therapy along with the additional 2 weeks time involved in recovery from a radical prostatectomy. Adverse events will be collected throughout the entirety of the study. The total duration of the patient being in the study can be around 9 to 11 weeks. Medical information/Survival information will be collected from the routine followup visits (standard of care) for up to 3 years after the surgery.

Inclusion Criteria:

1. Adult male > 18 years of age

2. Histologically confirmed diagnosis of prostate cancer

3. Intermediate or high risk prostate cancer defined by:

   • High risk (any one of the following):

     1. Gleason grade > 8
     2. Gleason grade 4+3 with more than 3 cores involved with > 20% of volume involved
     3. Any Gleason with PSA above 20 ng/mL
     4. Gleasone > 4+3 and tumor stage clinical T3 or above

   • Intermediate risk prostate cancer defined as:

     1. Gleason grade = 7
     2. Any Gleason with PSA between 10 and 20 ng/mL

4. Eastern Cooperative Oncology Group (ECOG) Performance status of 0-1

5. Ability to understand and willingness to sign a written informed consent document

6. Prostate biopsy with + PSMA expression in tumor cells by immunohistochemistry

Exclusion Criteria:

1. Serum creatinine > 3x upper limit of normal (ULN)
2. Bilirubin (total) > 1.5 x ULN; subjects with Gilbert's syndrome will be allowed if direct bilirubin is within institutional normal limits
3. Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT or SGOT) > 2.5x ULN
4. Other severe acute or chronic medical condition or laboratory abnormality that may increase the risk associated with study participation
5. On any other new anticancer therapy between screening and prostatectomy
6. Frank metastasis identified during clinical staging
7. Patient ineligible for radical prostatectomy for any other reason