Cabazitaxel Versus the Switch to Alternative AR Targeted Therapy Enzalutamide or Abiraterone in Metastatic Castration-Resistant Prostate Cancer (mCRPC) Primary Resistant Patients to Abiraterone or Enzalutamide (PRIMCAB)

Inclusion criteria:

• Diagnosis of histologically or cytologically confirmed prostate adenocarcinoma.
• Metastatic disease.
• Progressive disease (PD) while receiving AR targeted therapy with abiraterone acetate or enzalutamide within 12 months of treatment initiation (≤12 months) by at least one of the following:
• Progression in measurable disease Response Evaluation Criteria in Solid Tumors (RECIST) 1.1.
• Appearance of 2 or more new bone lesions according to Prostate Cancer Working Group 2 (PCWG2).
• Rising PSA defined (PCWG2) as at least two consecutive rises in PSA to be documented over a reference value (measure 1) taken at least one week apart.
• A PSA value of at least 2 nanogram/milliliter (ng/mL) is required at study entry.
• Effective castration (serum testosterone levels ≤0.5 ng/mL).
• Prior AR targeted therapy (abiraterone acetate or enzalutamide) must be stopped at least 2 weeks before study treatment.
• Signed written informed consent.

Exclusion criteria:

• Prior chemotherapy for prostate cancer, except estramustine and except adjuvant/neoadjuvant treatment completed >3 years ago. No further anti-cancer therapy after the previous AR targeted therapy and before inclusion. Prior docetaxel in hormone sensitive setting is allowed if completed >1 year before randomization. Prior immunotherapy is allowed.
• Less than 28 days elapsed from prior treatment with immunotherapy, radiotherapy, or surgery to the time of randomization.
• Adverse events (excluding alopecia and those listed in the specific exclusion criteria) from any prior anticancer therapy of grade >1(National Cancer Institute Common Terminology Criteria for Adverse Events [NCI CTCAE] v4.0) at the time of randomization.
• Eastern Cooperative Oncology Group (ECOG) performance status >1.
• History of brain metastases, uncontrolled spinal cord compression, or carcinomatous meningitis, or new evidence of brain or leptomeningeal disease.
• Prior malignancy. Adequately treated basal cell or squamous cell skin or superficial (pTis, pTa, and pT1) bladder cancer are allowed, as well as any other cancer for which treatment has been completed ≥5 years ago and from which the patient has been disease-free for ≥5 years.
• Participation in another clinical trial and any concurrent treatment with any investigational drug within 30 days prior to randomization.
• Acquired immunodeficiency syndrome (AIDS)-related illnesses or known Human immunodeficiency virus (HIV) disease requiring antiretroviral treatment.
• Any severe acute or chronic medical condition including uncontrolled diabetes mellitus, severe renal impairment, history of cardiovascular disease (uncontrolled hypertension, arterial thrombotic events in the past 6 months, congestive heart failure, severe or unstable angina pectoris, recent myocardial infraction within last 6 months or uncontrolled cardiac arrhythmia), which could impair the ability of the patient to participate to the study or interfere with interpretation of study results, or patient unable to comply with the study procedures.
• Participants with reproductive potential who do not agree to use accepted and effective method of contraception during the study treatment period and up to 6 months after the last administered dose. The definition of "effective method of contraception" will be based on the Investigator's judgment.
• Known allergies, hypersensitivity or intolerance to prednisone or excipients of abiraterone acetate or enzalutamide. History of hypersensitivity to docetaxel or polysorbate 80.
• Known history of mineralocorticoid excess or deficiency (not applicable to participants who have already been treated with abiraterone acetate in first line before inclusion).
• History of seizure, underlying brain injury with loss of consciousness, transient ischemic attack within the past 12 months, cerebral vascular accident, brain arteriovenous malformation or the use of concomitant medications that may lower the seizure threshold (not applicable to participants who have already been treated with enzalutamide in first line before inclusion).
• Unable to swallow a whole tablet or capsule.
• Inadequate organ and bone marrow function as evidenced by:
• Hemoglobin <10.0 g/dL.
• Absolute neutrophil count <1.5 x 10^9/L.
• Platelet count <100 x 10^9/L.
• Aspartate aminotransferase (AST) and/or Alanine aminotransferase (ALT) >1.5 x Upper limit of normal (ULN).
• Total bilirubin >1.0 x ULN.
• Potassium <3.5 mmol/L.
• Serum albumin <3.0 g/dL.
• Child-Pugh Class B and C.
• Contraindications to the use of corticosteroid treatment.
• Symptomatic peripheral neuropathy grade ≥2 NCI CTCAE v4.0.
• Concomitant vaccination with yellow fever vaccine.

The above information was not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.