Inclusion Criteria:

- Women aged ≥ 18 years;

- Histologically confirmed locally advanced or metastatic breast cancer;

- Triple negative breast cancer:

Estrogen receptor (ER)-negative and Progesterone receptor (PR)-negative, as defined by a
< 10 % tumour stained cells by immunohistochemistry (IHC); HER2 negative status (i.e. IHC
score 0 or 1+, or IHC score 2+ and FISH/SISH/CISH negative), confirmed centrally before
inclusion with FFPE tissue from either primary or metastatic breast cancer site*;

- Androgen receptor (AR)-positive, as defined centrally by a ≥ 10% tumour stained cells
by IHC (AR assessment by local pathologist before inclusion is not mandatory);

- Patients could be chemotherapy naïve (provided they are not presenting with
life-threatening metastasis) or have received any number of previous lines of
chemotherapy (providing their life expectancy is ≥ 3 months);

- Pre and post menopausal patients are eligible.

- Measurable or non measurable disease according to RECIST v1.1 criteria;

- PS (ECOG) ≤ 2;

- Normal haematological function: ANC ≥ 1,500/mm3; platelets count ≥ 100,000/mm3;
haemoglobin > 10 g/dl;

- Normal hepatic function: total bilirubin ≤ 1.5 upper normal limit (UNL); ASAT and
ALAT ≤ 2.5 UNL (≤ 5 UNL in the presence of liver metastases);

- Creatinine clearance (MDRD formula) ≥ 50 mL/min OR creatinine ≤ 1.5 times ULN;

- Normal kalemia (serum potassium ≥ 3.5 mM), natremia and magnesemia;

- Systolic blood pressure (BP) < 160 mm Hg and diastolic BP < 95 mm Hg, as documented
on inclusion day (Hypertension at baseline assessment allowed provided it is
currently controlled under anti-hypertensive drugs);

- Cardiac ejection fraction ≥50% measured by MUGA or ECHO done within 4 weeks before
inclusion;

- If receiving a bisphosphonate or denosumab, dose must have been stable for at least 2
doses before inclusion;

- Patient agreeing to use effective contraception during and for ≥ 6 months after
completion of study treatment;

- Patient able to comply with the protocol;

- Patient must have signed a written informed consent form prior to any study specific
procedures;

- Patient must be affiliated to a Social Health Insurance.

Exclusion Criteria:

- Male breast cancer;

- HER2-positive status (positivity defined as IHC3+ and/or FISH amplification >2.2);

- Other concurrent malignancies, except adequately treated cone-biopsied in situ
carcinoma of the cervix or basal cell or squamous cell carcinoma of the skin;
patients who have undergone potentially curative therapy for a prior malignancy are
eligible provided there is no evidence of disease for ≥ 5 years and patient is deemed
to be at low risk for recurrence;

- Active brain metastases or leptomeningeal disease; History of brain metastases
allowed provided lesions are stable for at least 3 months as documented by head CT
scan or MRI of the brain;

- Non-malignant systemic disease, including active infection or concurrent serious
illness that would make the patient a high medical risk;

- Significant cardiovascular disease, including any of the following:

1. NYHA class III-IV congestive heart failure;

2. Unstable angina pectoris or myocardial infarction within the past 6 months;

3. Severe valvular heart disease;

4. Ventricular arrhythmia requiring treatment.

- Patients with rare hereditary problems of galactose intolerance, the Lapp lactase
deficiency or glucose-galactose malabsorption should not be included;

- Patients with known allergies, hypersensitivity or intolerance to abiraterone
acetate, prednisone, or their excipients;

- Persistent toxicities ≥ grade 2 from any cause, except chemotherapy-induced alopecia
and Grade 2 peripheral neuropathy;

- Active or uncontrolled autoimmune disease requiring concurrent corticosteroid
therapy;

- Any gastrointestinal disorder interfering with absorption of the study drug;

- Difficulties with swallowing study capsules;

- Prior anticancer therapy, including radiotherapy, endocrine therapy, immunotherapy,
chemotherapy (CT) within the last 3 weeks (2 weeks for oral or weekly CT ; 6 weeks
for nitrosoureas and mitomycin C), or other investigational agents ; Concurrent
palliative radiotherapy allowed;

- Concurrent enrolment in another clinical trial in which investigational therapies are
administered;

- Pregnant women, women who are likely to become pregnant or are breast-feeding;

- Patients with any psychological, familial, sociological or geographical condition
potentially hampering compliance with the study protocol and follow-up schedule;
those conditions should be discussed with the patient before registration in the
trial;

- Patients with history of non compliance to medical regimens or unwilling or unable to
comply with the protocol;

- Individual deprived of liberty or placed under the authority of a tutor.