• Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1

• Age ≥18 years

• Diagnosis of metastatic adenocarcinoma of the prostate

• Must have a soft tissue metastasis amenable to biopsy

• Prostate-specific antigen (PSA) is not currently declining, as determined by most recent 2 measurements taken at least 1 week apart in previous 2 months.

• BMI between 20 and 35 kg/m2

• Prior treatment with any prostate cancer therapy is permitted if \>2 weeks from last dose. Patients are not required to have received prior treatment for prostate cancer.

• Prior treatment with steroids is permitted if \>2 weeks from last dose. Patients who cannot be weaned off steroids are not eligible.

• Acceptable liver function:

∙ Bilirubin \< 2.5 times institutional upper limit of normal (ULN)

‣ Aspartate transaminase (AST) (SGOT) and Alanine transaminase (ALT) (SGPT) \< 2.5 times ULN

⁃ Acceptable renal function: glomerular filtration rate (GFR) of 50 mL/min/1.73 m2 or higher. GFR will be estimated by the 2021 chronic kidney disease epidemiology (CKD-EPI) creatinine equation1 using the online calculator found on UpToDate.com

⁃ Acceptable hematologic status:

• Absolute neutrophil count (ANC) ≥ 1500 cells/mm3 (1.5 ×109/L)

∙ Platelet count ≥ 100,000 platelet/mm3 (100 ×109/L)

∙ Hemoglobin ≥ 8 g/dL.

⁃ Acceptable electrolyte and acid/base status:

• Sodium 135-148 millimoles (mM) per litre

∙ Potassium 3.5-5.1mM

∙ Carbon Dioxide 21-31mM

∙ Phosphorus 2.7-4.5mM

∙ Magnesium ≥1.6mM

∙ Lactate ≤2mM

⁃ Ability to understand and willingness to sign a written informed consent document