Inclusion Criteria:

          -  Adult women and men at least 18 years of age and willing and able to provide informed
             consent.

          -  Has advanced TNBC:

          -  TNBC is defined as staining by immunohistochemistry (IHC) < 1% or Allred score < 2 for
             estrogen receptor (ER) and progesterone receptor (PgR), and 0 or 1+ by IHC for human
             epidermal growth factor receptor 2 (HER2) or negative for gene amplification (average
             HER2 copy number < 4 signals/cell; HER2:CEP17 ratio < 2.0).

          -  Advanced disease is defined as locally advanced or metastatic disease not amenable to
             curative intent surgery or radiotherapy.

          -  Has diagnostic-positive status as determined by a central diagnostic testing
             laboratory.

          -  Received 0 or 1 prior line of systemic therapy in the advanced disease setting.

          -  Patients who received 1 prior line of therapy for locally advanced or metastatic TNBC
             must have objective disease progression as assessed by the investigator.

          -  Has measurable and/or disease that is not measurable but is evaluable using RECIST 1.1
             (eg, bone metastases, pathologic lymph nodes, or skin lesions).

          -  Patients with nonmeasurable and nonevaluable TNBC (eg, malignant effusions or bone
             marrow as the only manifestations of disease) are not eligible for enrollment.

          -  Patients with metastatic disease limited to the bone must have disease adequately
             visualized by computed tomography (CT) with bone windows, magnetic resonance imaging
             (MRI), or x-ray.

          -  Has an Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1 at
             screening and a life expectancy of at least 3 months from randomization.

        Exclusion Criteria:

          -  Received a taxane regimen ≥ 28 days in duration in the advanced disease setting.

          -  Prior taxane therapy for neoadjuvant and/or adjuvant disease is permitted.

          -  A single dose of a taxane given as part of an every-3-weeks regimen is permitted.

          -  Two doses of a taxane given as part of a once-weekly regimen is permitted.

          -  Had a disease-free interval of ≤ 12 months from the last dose of taxane when used as
             part of adjuvant therapy for patients who did not receive prior therapy for locally
             advanced or metastatic breast cancer.

          -  Has history of or known central nervous system (CNS) metastasis or active
             leptomeningeal disease; brain imaging is required for all patients during screening.

          -  Received any anticancer agent (commercially available or investigational) within 14
             days before randomization.

          -  Received treatment with any of the following medications within 14 days before
             randomization:

          -  Estrogens, including hormone replacement therapy

          -  Androgens (eg, testosterone, dehydroepiandrosterone)

          -  Systemic radionuclides (eg, samarium, strontium)

          -  Had major surgery within 4 weeks before randomization.

          -  Has a history of another invasive cancer within 3 years before randomization, with the
             exception of fully treated cancers with a remote probability of recurrence.

          -  Has a history of a seizure condition or any condition that may predispose to seizure
             (eg, prior cortical stroke or significant brain trauma).

          -  Has known hypersensitivity to any of the enzalutamide/placebo capsule components.

          -  Had a hypersensitivity reaction to Cremophor EL (polyoxyethylated castor oil) or a
             drug formulated in Cremophor EL, such as paclitaxel, unless successfully treated and
             rechallenged with appropriate premedications.