Selinexor in Treating Patients With Abiraterone Acetate and/or Enzalutamide Refractory Metastatic Castration-Resistant Prostate Cancer

PRIMARY OBJECTIVES:

I. To describe radiographic progression free survival (rPFS) associated with selinexor in
patients with abiraterone (abiraterone acetate) refractory metastatic castration-resistant
prostate cancer (mCRPC).

SECONDARY OBJECTIVES:

I. To measure prostate-specific antigen (PSA) changes at 12 weeks post-selinexor initiation.

II. To assess time to PSA progression. III. To measure time to development of >= 2 new bone
lesions. IV. To compare the relationship of abiraterone-resistance status (primary vs
acquired) and treatment outcome.

V. To determine the effect of selinexor on persistent pain associated with bone metastasis
using the brief pain inventory (BPI) short form.

VI. To describe the safety profile of selinexor in patients with metastatic
castration-resistant prostate cancer.

VII. To determine the effect of selinexor on circulating leukocyte exportin 1 (XPO-1)
expression, leukocyte gene expression profile and macrophage inhibitory cytokine-1 (MIC-1)
messenger ribonucleic acid (mRNA) expression.

VIII. To assess serum selinexor trough levels as a function of dose and time since last dose.

TERTIARY OBJECTIVES:

I. To describe the relationship of XPO-1 expression to PSA decline. II. To describe the
expression profile of metastatic tumor and outcome. III. To describe the type of progression
(e.g. pain, bone etc). IV. To define XPO-1 expression in patients for whom pre- and
post-treatment biopsy is obtained.

OUTLINE:

Patients receive selinexor orally (PO) on days 1 and 3 of weeks 1-3. Courses repeat every 28
days in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed up for 30 days and then every 6
months thereafter.

Inclusion Criteria:

- Histologically confirmed adenocarcinoma of the prostate

- Patients must have castrate levels of testosterone (< 50 ng/dL) on
gonadotropin-releasing hormone (GnRH) analogues or have had prior orchiectomy; GnRH
analogues must be continued while on study

- Tumor tissue submitted for molecular and genetic analysis through the companion
Stand-up 2 Cancer (SU2C) radiologically guided biopsy of abiraterone and/or
enzalutamide refractory mCRPC protocol

- Patients who consent to participate in the companion biopsy protocol and are
subsequently determined to be ineligible for biopsy are eligible to participate
in the current protocol

- Progressive disease as demonstrated by a rising PSA (at least two determinations)
prior to study entry, and/or radiographic evidence of tumor progression in soft tissue
according to modified Response Evaluation Criteria In Solid Tumors (RECIST) criteria
or identification of new lesions by bone scan (i.e., >= 2 new lesions)

- Primary resistance or acquired resistance (i.e., acquired resistance will be defined
as disease progression following a period of response defined as >= 50% decline in PSA
within 12 weeks of starting therapy and not otherwise meeting criteria for primary
resistance) to any of the following agents/combinations of therapy:

- Abiraterone acetate; primary resistance to abiraterone will be defined as:

- No PSA decline

- PSA decline less than 50% after 12 weeks of abiraterone therapy

- PSA progression within 12 weeks of abiraterone acetate (AA) treatment (by
Prostate Cancer Working Group-2 [PCWG2] criteria), after initial response to
therapy

- Objective progression, by RECIST criteria for soft tissue lesions and by modified
PCWG2 criteria for bone lesions within 12 weeks of starting abiraterone treatment

- Unequivocal clinical progression (per the treating provider's discretion) within
12 weeks of starting abiraterone treatment

- Enzalutamide; primary resistance to enzalutamide will be defined as:

- No PSA decline

- PSA decline less than 50% after 12 weeks of enzalutamide therapy

- PSA progression within 12 weeks of enzalutamide treatment (by PCWG2 criteria),
after initial response to therapy

- Objective progression, by RECIST criteria for soft tissue lesions and by modified
PCWG2 criteria for bone lesions within 12 weeks of starting enzalutamide
treatment

- Unequivocal clinical progression (per the treating provider's discretion) within
12 weeks of starting enzalutamide treatment

- Other second-generation investigational anti-androgen/androgen-receptor targeted
therapies, including apalutamide (ARN-509); primary resistance will be defined as:

- No PSA decline

- PSA decline less than 50% after 12 weeks of enzalutamide therapy

- PSA progression within 12 weeks of enzalutamide treatment (by PCWG2 criteria),
after initial response to therapy

- Objective progression, by RECIST criteria for soft tissue lesions and by modified
PCWG2 criteria for bone lesions within 12 weeks of starting enzalutamide
treatment

- Unequivocal clinical progression (per the treating provider's discretion) within
12 weeks of starting enzalutamide treatment

- Combination therapy with abiraterone, enzalutamide and/or other second- generation
investigational anti-androgen/androgen-receptor targeted therapies, including ARN-509;
primary resistance to combination therapy will be defined as:

- No PSA decline

- PSA decline less than 50% after 12 weeks of abiraterone and enzalutamide therapy

- PSA progression within 12 weeks of abiraterone and enzalutamide treatment (by
PCWG2 criteria), after initial response to therapy

- Objective progression, by RECIST criteria for soft tissue lesions and by modified
PCWG2 criteria for bone lesions within 12 weeks of starting abiraterone and
enzalutamide treatment

- Unequivocal clinical progression (per the treating provider?s discretion) within
12 weeks of starting abiraterone and enzalutamide treatment

- Sequenced therapy, including any of the following:

- Abiraterone acetate followed by enzalutamide

- Primary resistance will be defined per criteria for abiraterone monotherapy
primary resistance

- Enzalutamide followed by abiraterone acetate

- Primary resistance will be defined per criteria for enzalutamide monotherapy
primary resistance

- Other second-generation investigational anti-androgen/androgen- receptor targeted
therapies, including ARN-509

- Primary resistance will be defined per criteria for other investigational
anti-androgen monotherapy primary resistance

- Presence of 1 or more bone metastasis

- Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1

- Prior and ongoing zoledronic acid or denosumab therapy is allowed

- Prior therapy with radium-223 is allowed

- Discontinuation of prior therapy for mCRPC: a washout period of 28 days for the
following therapies is required: abiraterone, enzalutamide, fluconazole, itraconazole,
flutamide, bicalutamide, nilutamide, and other experimental hormonal agents (ARN509,
orteronel [TAK-700], etc.), sipuleucel-T (Provenge), other experimental vaccines
(PROSTVAC-V/F, etc.), strontium-89, samarium, and radium-223 chloride

- Leukocytes > 3,000/mcL

- Absolute neutrophil count > 1,500/mcL

- Platelets > 125,000/mcL

- Hemoglobin >= 5.59 mmol/L or 9 g/dL; up to 5% deviation is tolerated; transfusions and
growth factors are allowed

- Total bilirubin within normal institutional limits

- Aspartate aminotransferase (AST)(serum glutamic oxaloacetic transaminase [SGOT]) < 3 X
institutional upper limit of normal

- Alanine aminotransferase (ALT)(serum glutamate pyruvate transaminase [SGPT]) < 3 X
institutional upper limit of normal

- Creatinine within normal institutional limits OR creatinine clearance > 60 mL/min/1.73
m^2 for patients with creatinine levels above institutional normal

- Ability to understand a written informed consent document, and the willingness to sign
it

- Life expectancy of at least 12 weeks

- Able to swallow and retain oral medication

Exclusion Criteria:

- Untreated brain metastases; brain metastases =< 1 cm and not associated with any focal
neurologic deficits are allowed

- Prior docetaxel or other chemotherapy for mCRPC; patients who have received docetaxel
for metastatic hormone-sensitive prostate cancer are eligible

- Active or symptomatic viral hepatitis or chronic liver disease

- Clinically significant heart disease as evidenced by myocardial infarction, or
arterial thrombotic events in the past 6 months, severe or unstable angina, or New
York Heart Association (NYHA) class II-IV heart disease or known cardiac ejection
fraction measurement of < 50 % at baseline

- Patients with significantly diseased or obstructed gastrointestinal tract or
uncontrolled vomiting or diarrhea or other gastrointestinal disorders (medical
disorders or extensive surgery) that may interfere with the absorption of the study
agents

- Pure small cell carcinoma of the prostate or any mixed histology cancer of the
prostate (eg: neuroendocrine) that contains < 50% adenocarcinoma, as observed on
biopsy obtained at the time of diagnosis or on any subsequent biopsies

- Any ?currently active? second malignancy, other than non-melanoma skin cancer;
patients are not considered to have a "currently active? malignancy, if they have
completed therapy and are considered by their physician to be at least less than 30%
risk of relapse over next year

- Any condition, which in the opinion of the investigator, would preclude participation
in this trial

- Active psychiatric illnesses/social situations that would limit compliance with
protocol requirements

- Patients in whom urgent treatment with docetaxel is indicated, per clinician
discretion; this includes, but is not limited to patients with symptomatic visceral
metastatic disease

- Uncontrolled infection or concomitant medical illness that is not adequately
controlled with current medical management, as determined per clinician discretion

- Active bleeding disorders or evidence of evidence of chronic or acute disseminated
intravascular coagulation (DIC)

- Severely compromised immunological state, including known human immunodeficiency virus
(HIV)

- Any acute toxicities due to prior anti-cancer treatments and/or radiotherapy that have
not resolved to a National Cancer Institute (NCI) Common Terminology Criteria for
Adverse Events (CTCAE) grade of =< 1 (except alopecia)

- Prior radiation therapy completed < 3 weeks or single fraction of palliative
radiotherapy < 14 days prior to first dose of KPT-330 (selinexor)

- Initiation of bisphosphonate therapy < 4 weeks prior to first dose of KPT-330;
patients receiving bisphosphonate or denosumab therapy must be on stable doses for at
least 4 weeks prior to first dose of KPT-330

- Men unable or unwilling to employ 2 forms of highly effective contraception throughout
the study and for 8 weeks after the end of study treatment