Genetic and Molecular Mechanisms in Assessing Response in Patients With Prostate Cancer Receiving Enzalutamide Therapy

This phase II trial studies genetic and molecular mechanisms in assessing response in patients with prostate cancer receiving enzalutamide therapy. Androgens can cause the growth of prostate cancer cells. Antihormone therapy, such as enzalutamide, may lessen the amount of androgens made by the body. Studying samples of tissue and blood in the laboratory from patients with prostate cancer may help doctors better understand castration-resistant prostate cancer. It may also help doctors make improvements in prostate cancer treatment.

PRIMARY OBJECTIVE:

I. To assess the correlations between baseline molecular features and pathways and prostate-specific antigen (PSA) change (\</\>= 50% decline) at 12 weeks versus (vs.) baseline.

SECONDARY OBJECTIVES:

I. To measure PSA change at 12 weeks and at each study visit vs. baseline after enzalutamide treatment.

II. To measure objective response after enzalutamide treatment. III. To assess the correlations between the baseline molecular features and pathways and progression-free survival, disease-specific survival, and overall survival.

IV. To assess the correlations between the baseline molecular features and pathways and time to PSA progression.

V. To identify molecular features and cellular pathways present in tumors from men with metastatic castrate-resistant prostate cancer (CRPC) that are progressing despite enzalutamide treatment.

VI. To explore correlation between baseline molecular features and pathways and changes in circulating tumor cells (CTCs) counts.

VII. To explore correlation between baseline molecular features and pathways and objective response.

VIII. To assess the correlations between the baseline molecular features and pathways and degree of PSA decline at 12 weeks and maximal PSA decline observed while on study.

IX. To assess the correlations between the baseline molecular features and time on treatment.

EXPLORATORY OBJECTIVES:

I. To assess correlations between cell-free deoxyribonucleic acid (DNA) (cfDNA) molecular features from blood and molecular features and pathways from the biopsy samples.

II. To assess correlations between cfDNA molecular features and endpoints in the primary and secondary objectives listed above.

III. To assess correlations between cell-free DNA and tumor molecular features and changes in PSA after discontinuing enzalutamide.

IV. To explore correlations with baseline molecular features and tissue histology.

V. To explore correlations with baseline tissue histology and PSA change, time to PSA progression, time on treatment, progression-free survival, and overall survival.

OUTLINE:

Patients receive enzalutamide orally (PO) once daily (QD) in the absence of disease progression or unacceptable toxicity. Patients undergo a tumor biopsy of a metastatic site at study entry (prior to initiation of enzalutamide) and after the time of progression. Patients may continue treatment beyond progression at the investigator's discretion.

After completion of study treatment, patients are followed up at 2-3 or 6 weeks and then every 12 weeks thereafter.

Eligibility Criteria:
Inclusion Criteria:

* Histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma; patients without histologically confirmed adenocarcinoma may be eligible if both the treating physician and the study principal investigator (PI) agree that the patient's history is unambiguously indicative of advanced adenocarcinoma
* Ongoing androgen deprivation therapy with a gonadotropin-releasing hormone (GnRH) analogue or orchiectomy (i.e., surgical or medical castration); patients who have not had an orchiectomy must maintain effective GnRH-analogue therapy for the duration of the trial
* Radiographic evidence of regional or distant metastases with suspected tumor in an area that is safe to biopsy
* Willingness to undergo a tumor biopsy at baseline and at disease progression
* Serum testosterone level \< 50 ng/dL at screening
* Progressive disease by PSA or imaging in the setting of medical or surgical castration; disease progression for study entry is defined as one or more of the following three criteria:

  * PSA evidence for progressive prostate cancer which consists of a PSA level of at least 2 ng/ml which has risen on at least 2 successive occasions, at least 1 week apart; if the confirmatory PSA value is less than the screening value, then an additional PSA value greater than #2 will be required to document progression of \>= 1 week

    * PSA values to be obtained \>= 1 week apart
  * Soft tissue disease progression defined by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1
  * Bone disease progression defined by two or more new lesions on bone scan
* Patient's physician has already recommended enzalutamide for treatment of progression
* Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
* Willing and able to give informed consent
* Estimated life expectancy \>= 6 months
* Subjects who have partners of childbearing potential must be willing to use a method of birth control with adequate barrier protection as determined to be acceptable by the principal investigator and sponsor during the study and for 1 week after last study drug administration
* A minimum of 4 weeks elapsed off of anti-androgen therapy prior to enrollment for flutamide and 6 weeks for bicalutamide and nilutamide without evidence of an anti-androgen withdrawal response; patients who NEVER HAD A PSA decline with the most recent anti-androgen therapy or in whom the response to the most recent anti-androgen was for \< 3 months require only a 2 week washout period prior to first dose of study drug
* A minimum of 4 weeks from prior systemic anti-cancer therapies or 3 weeks for radiation treatment prior to enrollment is required

Exclusion Criteria:

* Severe, concurrent disease, infection, or co-morbidity that, in the judgment of the investigator, would make the patient inappropriate for enrollment
* Previous treatment with docetaxel for metastatic prostate cancer
* Known metastases in the brain or active epidural disease (NOTE: patients with treated epidural disease are allowed)
* Absolute neutrophil count \< 1,000/uL
* Platelet count \< 75,000/uL
* Hemoglobin \< 9 g/dL at the screening visit; (NOTE: subject may not have received any growth factors or blood transfusions within seven days of the hematologic laboratory values obtained at the screening visit)
* Total bilirubin (TBL) \> 2.5 times the upper limit of normal at the screening visit
* Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 2.5 times the upper limit of normal at the screening visit
* Creatinine (Cr) \> 2 mg/dL at the screening visit
* Prothrombin time (PT) or international normalized ratio (INR) and a partial thromboplastin time (PTT) \> 1.5 times the upper limit of normal
* Previous treatment with an agent that blocks adrenal androgen synthesis (e.g. abiraterone acetate, TAK-700, TOK-001, ketoconazole) or second generation androgen receptor (AR) antagonists (e.g., BMS 641988, ARN-509,TOK-001)
* Systemic corticosteroids greater than the equivalent of 10 mg of prednisone per day within 4 weeks of study drug administration are prohibited
* Structurally unstable bone lesions suggesting impending fracture
* Previous treatment with enzalutamide (MDV3100)
* Medical contraindications to stopping aspirin, Coumadin or other anticoagulants prior to image-guided tumor biopsies; follow institutional guidelines when determining drugs to avoid and length of washout
* Plans to initiate treatment with an investigational agent during the study
* History of seizure or condition that may predispose to seizure; also, history of loss of consciousness or transient ischemic attack within 12 months of (day 1 visit)
* Concomitant use of the strong CYP2C8 inhibitors gemfibrozil or trimethoprim (Bactrim)
* History of known malabsorption syndrome or prior surgery(ies) that may lead to malabsorption
* Use of herbal products that may have hormonal anti-prostate cancer activity and/or are known to decrease PSA levels (e.g., saw palmetto) within 4 weeks of study drug administration (day 1)
* Use of the following drugs within 4 weeks of study drug administration: 5 alpha-reductase inhibitors (finasteride, dutasteride), estrogens, Cyproterone acetate, biologic, or other agents with anti-tumor activity against prostate cancer, and androgens (testosterone, dihydroepiandrosterone \[DHEA\], etc.)
* A second active malignancy except adequately treated non-melanoma skin cancer or other non-invasive or in situ neoplasm