Magnetic Resonance (MR) Imaging With Hyperpolarized Pyruvate (HP) (13C) in Castration-Resistant Prostate Cancer

Inclusion Criteria: 1. Biopsy-proven prostate cancer. 2. Progressive, castration-resistant disease according to PCWG2 criteria. 3. Planned treatment with an androgen signaling inhibitor (e.g., abiraterone, enzalutamide, apalutamide (ARN-509)). Patients must not be receiving androgen signaling inhibitor at the time of the baseline MR scan. Combination treatment (e.g., androgen signaling inhibitor in conjunction with another systemic treatment) is allowed. 4. Presence of at least one target lesion detected by standard staging scans that, in the judgment of Study Investigators, would be amenable to hyperpolarized C-13 pyruvate/metabolic MR imaging: * Soft tissue/visceral organ target lesions must measure at 1.5 cm in long axis diameter on CT or MRI. * Target lesions in the bone must be visualized by CT or MRI (lesions present only on bone scan do not qualify). * For patients with target lesion in prostate/prostatic bed: i. No contra-indications to endorectal coil insertion (e.g., patients with a prior abdominoperineal resection of the rectum or latex allergy). ii. No prior local treatment to the selected lesion. Patients who have received prior radiation or ablative therapy to the prostate will be required to have biopsy-proven evidence of disease recurrence following completion of local therapy. 5. The subject is able and willing to comply with study procedures and provide signed and dated informed consent. 6. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1. 7. Adequate organ function, including absolute neutrophil count (ANC) ≥ 1500 cells/µL, hemoglobin ≥ 9.0 gm/dL, platelets ≥ 75,000 cells/µL, creatinine \< 1.5 x ULN or estimated creatinine clearance ≥ 50 mL/min (by the Cockcroft Gault equation), bilirubin \<1.5x ULN (unless Gilbert's is suspected in which case total bilirubin \< 3 x ULN), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 1.5x ULN. 8. For patients undergoing optional tumor biopsy: * No history of bleeding diathesis. * Patients on anti-coagulation they must be able to safely stop treatment for purposes of tumor biopsy. 9. For patients with partners of childbearing potential, willing to use adequate contraception for one month after undergoing HP pyruvate infusion. 10. Patients must have prior bilateral orchiectomy or be on continuous luteinizing-hormone releasing hormone (LHRH) analogue therapy for the duration of study. 11. Castrate level of serum testosterone (\< 50 ng/dL) at study entry. Exclusion Criteria: 1. Patients who because of age, general medical or psychiatric condition, or physiologic status cannot give valid informed consent. 2. Patients unwilling or unable to undergo MR imaging, including patients with contra-indications to MRI, such as cardiac pacemakers or non-compatible intracranial vascular clips. 3. Metallic hip implant or any other metallic implant or device that distorts local magnetic field and compromises the quality of MR imaging. 4. Poorly controlled hypertension, defined as systolic blood pressure at study entry greater than 160 mm Hg or diastolic blood pressure greater than 100 mm Hg. The addition of anti-hypertensives to control blood pressure is allowed. 5. Congestive heart failure or New York Heart Association (NYHA) status ≥ 2. 6. A history of clinically significant EKG abnormalities, including QT prolongation (QTcF \> 500 ms), a family history of prolonged QT interval syndrome, or myocardial infarction (MI) within 6 months of study entry. Patients with rate-controlled atrial fibrillation/flutter will be allowed on study. 7. Any condition that, in the opinion of the Principal Investigator, would impair the patient's ability to comply with study procedures.