Inclusion Criteria

Inclusion criteria :

- Diagnosis of prostate adenocarcinoma proven histologically or cytologically,
resistant to hormone therapy and previously treated with a docetaxel-containing
regimen. In Phase 2 part, patients should have been treated with abiraterone acetate
for at least 3 months and should continue treatment with abiraterone acetate before
study entry

- Presence of metastatic prostate cancer.

- Patient must have progressive disease documented by rising PSA defined as 2
sequential increases above a previous lowest reference value (each PSA value must be
obtained at least 1 week apart. A PSA value of at least 6 ng/mL is required at study
entry). In Phase 1 part, in addition to rising PSA, progressive disease must be
documented by:

1. Increase in non-measureable or measurable disease, and/or

2. Appearance of new lesions, including those on bone scan (≥2 new lesions on 2
consecutive bone scans if progressive disease diagnosed on bone scan only)
consistent with progressive prostate cancer

- Effective castration (serum testosterone levels ≤0.50 ng/mL) by orchiectomy and/or
luteinizing hormone-releasing hormone agonists /antagonist.

1. If the patient has been treated with luteinizing hormone-releasing hormone
agonists/antagonist (i.e., without orchiectomy), then this therapy must have
been initiated at least 4 weeks prior to cycle 1 day 1 and should be continued
throughout the study.

2. Prior anti-androgen therapy should be stopped before enrollment

- Eastern Cooperative Oncology Group performance status: 0 - 1.

Exclusion criteria:

Previous treatment with mitoxantrone or cabazitaxel.

- Prior bone-seeking radio-isotope therapy (patients treated with Radium223 are not
excluded from the study). Radiotherapy to ≥30% of bone marrow.

- Adverse events from any prior anticancer therapy of grade >1 at the time of
enrollment.

Prior surgery, radiation, chemotherapy, or other anti-cancer therapy within 4 weeks prior
to enrollment in the study (except luteinizing hormone-releasing hormoneagonist
/antagonist and abiraterone acetate in the Phase 2 part of the study); small field single
fraction palliative radiation within 1 week.

- Prior malignancy. Curatively 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 chemotherapy has been completed ≥ 3 years ago and from which the patient has
been disease-free for ≥ 3 years.

- Participation in another clinical trial and any concurrent treatment with any
investigational drug within 30 days prior to enrollment.

- Known brain or leptomeningeal metastases.

- Any severe acute or chronic medical condition which could impair the ability of the
patient to participate to the study or to comply with the study procedures or
interfere with interpretation of study results.

- Other concurrent serious illness or medical conditions

- Absence of signed and dated patient informed consent form prior to enrollment into
the study.

- History of hypersensitivity to docetaxel, polysorbate 80

- Known allergies, hypersensitivity or intolerance to prednisone or excipients of
abiraterone acetate

- Known history of mineralocorticoid excess or deficiency

- Inadequate organ and bone marrow function Contraindications to the use of
corticosteroid treatment.

- Symptomatic peripheral neuropathy grade > 1

- Concurrent treatment with strong inducers or strong inhibitors of CYP450 3A4

- Concurrent treatment with medications metabolized by CYP2D6, particularly for those
with a small therapeutic window

- History of cardiac arrhythmias requiring medical therapy such as atrial fibrillation
requiring anticoagulation or digoxin/digitalis; uncontrolled angina pectoris. History
of congestive heart failure or myocardial infarction within last 6 months is also not
allowed.

- Uncontrolled hypertension (systolic BP ≥160 mmHg or diastolic BP ≥ 95 mmHg). Patients
with a history of hypertension are allowed, provided that blood pressure is
controlled to within these limits by anti-hypertensive treatment

- Clinically significant heart disease as evidenced by myocardial infarction, or
arterial thrombotic events in the past 12 months, severe or unstable angina, or New
York Heart Association Class III or IV heart disease or cardiac left ventricular
ejection fraction measurement of <50% at baseline

- Patients with reproductive potential who do not agree to use accepted and effective
method of contraception in conjunction with their partner(s) during the study
treatment period.

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