Abiraterone Acetate and Antiandrogen Therapy With or Without Cabazitaxel and Prednisone in Treating Patients With Metastatic, Castration-Resistant Prostate Cancer Previously Treated With Docetaxel

PRIMARY OBJECTIVES:

I. To assess whether the addition of 6 cycles of cabazitaxel to abiraterone acetate in
patients with castration-resistant prostate cancer (CRPC) that have previously received
docetaxel and androgen deprivation therapy (ADT) for hormone-sensitive prostate cancer (HSPC)
can improve progression-free survival (PFS) compared to abiraterone acetate alone.

SECONDARY OBJECTIVES:

I. To assess whether the addition of 6 cycles of cabazitaxel to abiraterone acetate in
patients with CRPC that have previously received docetaxel and ADT for HSPC can increase the
percentage of change in prostate-specific antigen (PSA) from baseline to week 12 of treatment
as well as the maximum decline in PSA that occurs at any point after treatment compared to
abiraterone acetate alone.

II. To assess whether the addition of 6 cycles of cabazitaxel to abiraterone acetate in
patients with CRPC that have previously received docetaxel for HSPC can prolong time to PSA
progression compared to abiraterone acetate alone.

III. To assess whether the addition of 6 cycles of cabazitaxel to abiraterone acetate in
patients with CRPC that have previously received docetaxel for HSPC can improve radiographic
response (per Response Evaluation Criteria in Solid Tumors [RECIST] 1.1) compared to
abiraterone acetate alone.

IV. To assess whether the addition of 6 cycles of cabazitaxel to abiraterone acetate in
patients with CRPC that have previously received docetaxel and ADT for HSPC can prolong the
overall survival (OS) compared to abiraterone acetate alone.

V. To assess safety and tolerability of the combination of 6 cycles of cabazitaxel and
abiraterone acetate.

TERTIARY OBJECTIVES:

I. To examine whether patients with circulating tumor cells (CTCs) positive for AR-V7 at
baseline have a longer radiographic or clinical PFS to the combination of cabazitaxel and
abiraterone acetate vs. abiraterone acetate alone.

II. To examine whether the addition of cabazitaxel to abiraterone acetate can change the
AR-V7 status of patients who are positive at study entry.

III. To examine whether the addition of cabazitaxel to abiraterone acetate has any impact on
future development of AR-V7 positivity at the time of disease progression.

IV. To assess if the changes in total tumor burden from baseline to week 12 as assessed with
sodium fluoride (NaF) positron emission tomography (PET)/computed tomography (CT) will differ
between two arms.

V. To correlate total tumor burden at the baseline as assessed with NaF PET/CT with the PFS.

VI. To correlate heterogeneity of response from baseline to week 12 as assessed with NaF
PET/CT with the PFS.

OUTLINE: Patients are randomized to 1 of 2 arms.

ARM A: Patients receive abiraterone acetate orally (PO) once daily (QD) on days 1-21,
prednisone PO twice daily (BID) on days 1-21. Courses of abiraterone acetate and prednisone
repeat every 21 days in the absence of disease progression or unacceptable toxicity. Patients
receive cabazitaxel intravenously (IV) over 1 hour on day 1, and treatment with cabazitaxel
repeats every 21 days for up to 6 courses in the absence of disease progression or
unacceptable toxicity. Patients also receive standard of care antiandrogen therapy with
either luteinizing hormone-releasing hormone (LHRH) agonist or antagonist, or surgical
castration with bilateral orchiectomy.

ARM B: Patients receive abiraterone acetate and prednisone as in Arm A. Patients also receive
standard of care antiandrogen therapy with either LHRH agonist or antagonist, or surgical
castration with bilateral orchiectomy.

After completion of study treatment, patients are followed up every 3 or 6 months and then
annually for up to 5 years.

Inclusion Criteria:

- Histologically confirmed diagnosis of prostate cancer (adenocarcinoma of the prostate)

- Previous chemotherapy with at least 3 cycles of docetaxel for hormone-sensitive
metastatic prostate cancer

- Metastatic disease as evidenced by the presence of soft tissue and/or bone metastases
on imaging studies (CT/magnetic resonance imaging [MRI] of abdomen/pelvis, bone
scintigraphy or NaF PET/CT)

- Ability to swallow abiraterone acetate tablets as a whole

- All patients must be receiving standard of care androgen deprivation treatment
(surgical castration versus LHRH agonist or antagonist treatment); subjects receiving
LHRH agonist or antagonist must continue treatment throughout the time on this study

- Patients must have castrate serum level of testosterone of < 50 ng/dL (< 1.73 nmol/L)

- Patients must have progressive disease while receiving androgen deprivation therapy
defined by any one of the following as per the Prostate Cancer Clinical Trials Working
Group 3 (PCWG3) criteria for PSA, measurable disease or non-measurable (bone) disease
during treatment with ADT:

- PSA: At least two consecutive rises in serum PSA, obtained at a minimum of 1-week
intervals, with the final value >= 2.0 ng/mL

- Measurable disease (by RECIST 1.1): > 20% increase in the sum of the longest
diameters of all measurable lesions or the development of new measurable lesions;
the short axis of a target lymph node must be more that 15 mm to be assessed for
change in size

- Non-measurable (bone) disease: The appearance of two or more new areas of uptake
on bone scan (or NaF PET/CT) consistent with metastatic disease compared to
previous imaging during castration therapy; the increased uptake of pre-existing
lesions on bone scan will not be taken to constitute progression, and ambiguous
results must be confirmed by other imaging modalities (e.g. X-ray, CT or MRI)

- Patients may or may not have been treated previously with a nonsteroidal antiandrogen,
such as flutamide, bicalutamide or nilutamide; for patients previously treated with an
antiandrogen, they must be off treatment for at least 4 weeks (for flutamide) or 6
weeks (for bicalutamide or nilutamide) prior to registration and must have shown PSA
progression after discontinuing the anti-androgen

- Patients must have an Eastern Cooperative Oncology Group (ECOG) performance status of
0, 1, or 2

- Absolute neutrophil count (ANC) >= 1500/mm^3

- Hemoglobin (HgB) >= 9.0 gr/dL

- Platelets >= 100,000/mm^3

- Creatinine < 2.0 mg/dL

- Patients must be informed of the experimental nature of the study and its potential
risks, and must sign an Institutional Review Board (IRB)-approved written informed
consent form indicating such an understanding

- Patients with resected or irradiated brain metastases or those treated with
stereotactic radiation therapy are eligible to enroll, provided that they do not
require treatment with steroids that exceeds 10 mg of prednisone daily or equivalent

- Sexually active males must use an accepted and effective method of double barrier
contraception or abstain from sexual intercourse for the duration of their
participation in the study and for 26 weeks after the last dose of study drug

- NaF PET/CT OPTIONAL SUB-STUDY ELIGIBILITY CRITERIA

- Ability to lie still for imaging

- Weight =< 300 lbs (pounds)

Exclusion Criteria:

- Any prior chemotherapy or androgen receptor (AR)-directed therapy for CRPC, (e.g.
docetaxel, cabazitaxel, mitoxantrone, abiraterone acetate, ketoconazole, or
enzalutamide); previous treatment with radium-223 or sipuleucel-T is allowed

- Pure small cell or other variant (non-adenocarcinoma) prostate cancer histology for
which treatment with abiraterone would not be considered appropriate

- Patients may not be receiving other therapeutic investigational agents or be receiving
concurrent anticancer therapy other than standard androgen deprivation therapy;
concurrent treatment with agents to prevent skeletal-related events (such as
zoledronic acid or denosumab) will be allowed as long as it was initiated prior to
study entry

- Any medical condition for which prednisone (corticosteroid) is contraindicated

- If total bilirubin is > upper limit of normal (ULN) (NOTE: in subjects with Gilbert?s
syndrome, if total bilirubin is

> ULN, measure direct and indirect bilirubin and if direct bilirubin is within normal
range, subject may be eligible) or

- Alanine (ALT) or aspartate (AST) aminotransferase > 1.5 x ULN

- Active infection requiring treatment with antibiotics

- History of adrenal insufficiency or hypoaldosteronism

- Myocardial infarction or arterial thrombotic event within 6 months, heart failure of
New York Heart Association class II or higher, uncontrolled angina, severe
uncontrolled ventricular arrhythmia

- External beam radiation therapy within 4 weeks of registration

- Prior history of allergic reactions to G-CSF

- Prior history of allergic reactions to docetaxel and/or to medications formulated with
polysorbate 80

- History of active malignancy; patients with a history of cancer that has been
adequately treated and are free of disease recurrence for 3 years or more are allowed
to participate; patients with non-melanoma skin cancers or carcinoma in situ of the
bladder that have been adequately excised are eligible to participate

- Life expectancy of < 12 months at screening

- Grade >= 2 neuropathy