Inclusion Criteria:  Written informed consent obtained prior to any study-related procedure being performed Male patients at least 18 years of age or older at time of consent Pathologically confirmed adenocarcinoma of the prostate Ongoing therapy with a gonadotropin releasing hormone (GnRH) agonist or antagonist (unless patient has already had a bilateral orchiectomy) AND serum testosterone level <50 ng/dL at screening Have either metastatic CSPC or metastatic CRPC (per protocol definitions).  The following prior treatments and/or surgery for prostate cancer are allowed:  CSPC:  Up to 90 days of androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) agonists/antagonists or orchiectomy with or without concurrent anti-androgens prior to patients' randomization is permitted Patients may have one course of palliative radiation or surgical therapy to treat symptoms resulting from metastatic disease (e.g., impending cord compression or obstructive symptoms) if administered prior to randomization Radiation or surgical therapy that was not initiated 4 weeks after the start of ADT or orchiectomy  CRPC:  Previous chemotherapy with docetaxel for metastatic disease with treatment completed at least 1 year prior to enrolment Discontinuation of flutamide or nilutamide, and other anti-androgens prior to the start of study medication; discontinuation of bicalutamide prior to start of study medication Discontinuation of strong CYP3A4 inducers at prior to start of study medication Discontinuation of radiotherapy prior to start of study medication Discontinuation of herbal supplements at least 4 weeks prior to the first dose of study medication and for the duration of the trial. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 at screening  Normal organ function with acceptable initial laboratory values within the screening period:  ANC: ≥ 1,500/μl Albumin: ≥ 3.0g/dL Hemoglobin: ≥ 9g/dL Platelet count: ≥ 100,000/μl Serum Creatinine: ≤ 3.0 x the institutional upper limit of normal (ULN) Potassium: ≥ 3.5 mmol/L (within institutional normal range) Bilirubin: ≤ 1.5 ULN (unless documented Gilbert's disease) SGOT (AST): ≤ 2.5 x ULN SGPT (ALT): ≤ 2.5 x ULN Life expectancy of at least 6 months at screening Patients engaged in sex with women of child-bearing potential agree to use a condom plus another effective contraception method. Patients agree to use a condom when engaged in any sexual activity, including sex with a pregnant woman. These restrictions will apply from the time informed consent is provided until 3 weeks after the last dose of study medication is taken. Patient is willing and able to comply with all protocol requirements  Exclusion Criteria:  For mCSPC patients: any prior pharmacotherapy, radiation therapy, or surgery for metastatic prostate cancer not specified as allowable treatment in Inclusion Criterion 6. For example, prior therapy with apalutamide or enzalutamide is prohibited as well as therapy with an investigational agent as described in Exclusion Criterion 16.  For mCRPC patients:  Prior treatment with abiraterone or enzalutamide is prohibited Previous chemotherapy is prohibited with exception of docetaxel treatment as specified in the inclusion criteria 6. Initiation of bisphosphonate or denosumab therapy within 4 weeks prior to the start of study drug/reference product. Patients who are on a stable dose of these medications for at least 4 weeks at the time of starting study drug/reference product will be eligible. Therapy with estrogen within 4 weeks prior to the start of study drug Use of systemic glucocorticoids equivalent to >10 mg prednisone daily. Patients who have discontinued or reduced dosing to the equivalent of ≤ 10 mg prednisone daily within 14 days prior to the start of study drug are eligible Known, symptomatic metastases to the brain or central nervous system involvement (patients with asymptomatic and neurologically stable disease for the past 4 weeks will be permitted) History of adrenal gland dysfunction defined as requiring treatment for adrenal insufficiency History of other malignancy within the previous 2 years (no longer being actively treated), with the exceptions of basal cell carcinoma, nonmuscle invasive bladder cancer that has been treated and is under surveillance, or other in-situ cancers with a low likelihood of recurrence Major surgery within 4 weeks prior to the start of study drug Known gastrointestinal disease or condition that could impair absorption inclusive of gastrocolic fistula, gastroenterostomy, biliary obstruction, cirrhosis, chronic pancreatitis or pancreatic cancer, cystic fibrosis, lactate deficiency, amyloidosis, celiac disease, Crohn's disease, radiation enteritis, intestinal resection, and history of bariatric surgery Known history of human immunodeficiency virus or seropositive test for hepatitis C virus (HCV) or hepatitis B surface antigen (HBsAg) (note: HCV patients with undetectable viral load will be eligible) Poorly controlled diabetes, defined as HbA1c > 8% within the past 12 months Uncontrolled hypertension at screening History of New York Heart Association class III or IV heart failure Serious concurrent illness, including psychiatric illness, that could interfere with study participation Receipt of another investigational agent within 4 weeks or 5 x the treatment half-life, whichever is longer, of treatment start. Known hypersensitivity or allergy to abiraterone acetate, prednisone or any excipients in the study drugs In the opinion of the investigator, participation in the trial would prevent the patient from receiving local standard-of-care treatment for metastatic prostate cancer, if clinically indicated, after completion of the trial Other condition which, in the opinion of the Investigator, would preclude participation in this trial.