Inclusion Criteria:

- Have a histologic or cytologic diagnosis of prostate cancer

- Have progressive metastatic castration-resistant prostate cancer, on
androgen-deprivation therapy, based on at least one of the following criteria:

- Prostate-specific antigen (PSA) progression defined as 25% increase over
baseline value with an increase in the absolute value of at least 2 ng/mL that
is confirmed by another PSA level with a minimum of a 1-week interval with a
minimum PSA of 2 ng/mL

- Progression of bidimensionally measurable soft tissue (nodal metastasis)
assessed within one month prior to registration by a computed tomography (CT)
scan or magnetic resonance imaging (MRI) of the abdomen and pelvis

- Progression of bone disease (evaluable disease) (new bone lesion[s]) by bone
scan

- Agree to undergo a biopsy of >= 1 metastatic site for gene-fusion status

- Adequate archival metastatic tissue can be used if available in lieu of a
biopsy; patients will only be eligible for protocol therapy if the biopsy has
tumor and the tissue is evaluable for ETS fusion status

- Have testosterone < 50 ng/dL; patients must continue primary androgen-deprivation
with a luteinizing hormone-releasing hormone (LHRH) analogue if they have not
undergone orchiectomy

- Patients with known brain metastases should be excluded from this clinical trial

- Eastern Cooperative Oncology Group (ECOG) performance status of 0-2

- White blood cells >= 3,000/uL

- Absolute neutrophil count >= 1,500/uL

- Platelet count >= 100,000/uL

- Creatinine within the institutional limits of normal

- Potassium >= 3.5 mmol/L

- Bilirubin within the institutional limits of normal

- Serum glutamic oxaloacetic transaminase (SGOT) (aspartate aminotransferase [AST]) =<
2 times upper limit of normal

- Serum glutamic pyruvate transaminase (SGPT) (alanine aminotransferase [ALT]) =< 2
times upper limit of normal

- Must agree to use effective contraception during treatment and for at least 1 week
after the last administration of therapy

- Patients must be able to take oral medication without crushing, dissolving, or
chewing tablets

- Ability to understand and the willingness to sign a written informed-consent document
that is approved by the local institutional review board

- Patients with history of active seizures are not eligible

- Patients with a history of pituitary or adrenal dysfunction, active or symptomatic
viral hepatitis, or chronic liver disease are not eligible

- No history of allergic reactions attributed to compounds of similar chemical or
biologic composition to ABT-888 or abiraterone

- No uncontrolled intercurrent illness including, but not limited to, ongoing or active
infection, symptomatic congestive heart failure (New York Heart Association class III
and IV heart failure), unstable angina pectoris, cardiac arrhythmia, or psychiatric
illness/social situations that would limit compliance with study requirements or
concurrent medications that alter cardiac conduction

- Patients with a "currently active" second malignancy other than non-melanoma skin
cancers are not eligible; patients are not considered to have a "currently active"
malignancy if they have completed all therapy and are now considered without evidence
of disease for 1 year

- Human immunodeficiency virus (HIV)-positive patients on combination antiretroviral
therapy are ineligible

- Patients must discontinue antiandrogen therapy for at least 4 weeks (e.g., flutamide,
bicalutamide, nilutamide) prior to registration with no evidence of a falling PSA
after washout; patients on steroids are eligible as long as they will be switched to
prednisone

- Have no prior exposure to cytochrome P450, family 17, subfamily A, polypeptide 1
(CYP-17) or poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors

- Patients with up to 2 prior chemotherapy regimens are eligible

- Patients may have received prior radiation therapy or surgery; however, at least 21
days must have elapsed since completion of radiation therapy or surgery and patient
must have recovered from all side effects at the time of registration

- Patients may not be receiving any other investigational agents; any prior
investigational products must be stopped at least 14 days (2-week washout) prior to
registration

- No patients who have had chemotherapy or antifungal agents (itraconazole,
fluconazole) within 3 weeks prior to entering the study or those who have not
recovered (e.g., back to baseline or grade 1) from adverse events due to agents
administered more than 3 weeks earlier

- Patients may continue on a daily multivitamin, calcium, and vitamin D, but all other
herbal, alternative, and food supplements (i.e., PC-SPES, saw palmetto, St. John
wort, etc.) must be discontinued before registration

- Patients must not be planning to receive any concurrent cytotoxic chemotherapy,
surgery, or radiation therapy during protocol treatment

- Hormonal-acting agents (including diethylstilbestrol [DES], aldosterone, and
spironolactone) are forbidden during the trial and must be stopped prior to
registration; no washout period will be required for any of these agents

- Patients on stable doses of bisphosphonates or denosumab which have been started
prior to registration may continue on this medication, patients who are not on
bisphosphonates or denosumab are eligible as long as they initiate therapy prior to
registration