New drug combo shows promise in early breast cancer trial

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Phase I: Patients must have histologically confirmed breast cancer (metastatic breast cancer \[MBC\]) that is human epidermal growth factor receptor 2 (HER2/neu) negative (as determined by local pathology or reference laboratory), and have disease that is metastatic (stage IV \[TxNxM1\]) or locally advanced and not amenable to potentially curative surgical resection (eg, clinical stage IIIB-C) * HER2/neu negative disease (performed on primary tumor and/or metastatic lesion using commercially available/approved assay in local institutional or reference laboratory), according to American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines * National Comprehensive Cancer Network (NCCN) guidelines recommend for metastatic breast cancer "…biopsy documentation of first recurrence, if possible, and determination of hormone receptor status (estrogen receptor \[ER\] and progesterone receptor \[PR\]) and HER2 status…."; therefore, histologic and/or cytologic confirmation of metastatic disease is encouraged whenever feasible, but not required; in some circumstances, histologic confirmation may not be feasible (eg, bone metastases not amenable to biopsy and elevated cancer antigen \[CA\]27-29 tumor marker); for patients who have had histologic confirmation of metastatic disease, it is required that the biopsy confirm that the metastatic tumor is ER and/or PR positive, and HER2/neu negative; for patients in whom biopsy confirmation of metastatic disease is not feasible, it is required that the primary tumor be ER and/or PR-positive and HER2/neu negative * Measurable disease (Response Evaluation Criteria in Solid Tumors \[RECIST\] 1.1) or non-measurable disease, with measurement obtained within 4 weeks of registration * Phase I: Patients must have received at least one prior chemotherapy regimen for metastatic disease; patients with deleterious germ line mutations in breast cancer (BRCA)1 or BRCA2 are not required to have received prior chemotherapy for metastatic disease * Patients must have had progressive disease after at least one line of endocrine therapy for metastatic disease (includes relapse while receiving endocrine therapy); there should be at least 1 week interval between the last endocrine treatment for an aromatase inhibitor and at least 2 weeks for tamoxifen or fulvestrant * Eastern Cooperative Oncology Group (ECOG) performance status 0, 1, or 2 (Karnofsky \>= 60%) * Leukocytes \>= 3,000/mcL * Absolute neutrophil count \>= 1,500/mcL * Platelets \>= 100,000/mcL * Hemoglobin \>= 9 g/dl (per manufacturer recommendation) * Total bilirubin within normal institutional limits (unless isolated indirect hyperbilirubinemia due to Gilbert's disease) * Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase \[SGOT\])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase \[SGPT\]) =\< 2.5 × 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 * Patients with a history of brain metastases are eligible if they have been treated with radiation and have stable brain metastases at least 3 months after radiation and must also be off steroids * Patients must be able to swallow whole capsules and tolerate oral medications * Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation; being not of childbearing potential is defined as: (1) prior hysterectomy, or (2) no menstrual period for at least 24 months; should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately * Ability to understand and the willingness to sign a written informed consent document Exclusion Criteria: * Patients who have radiotherapy within 3 weeks prior to entering the study or those who have not recovered from adverse events due to systemic agents administered more than 3 weeks earlier * Patients may not be receiving any other investigational agents * Patients with known brain metastases with active symptoms or requiring anticonvulsive medications, or steroids should be excluded from this clinical trial * History of allergic reactions attributed to compounds of similar chemical or biologic composition to veliparib (ABT-888) or cyclophosphamide used in the study * Evidence of complete or partial bowel obstruction or other unable to take oral medications * Patients with malabsorption syndrome or other condition that would interfere with intestinal absorption * Patients unable to swallow whole capsules * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements * Pregnant (positive pregnancy test) or lactating women will be excluded from the study; also, unwillingness to use effective means of contraception in subjects with child-bearing potential will be excluded from the study; women of child-bearing potential must use two forms of contraception (i.e., barrier contraception and one other method of contraception) at least 4 weeks prior to study entry, for the duration of study participation * Patients with active severe infection; known infection with human immunodeficiency virus (HIV), hepatitis B virus, hepatitis C virus, or severe concurrent illness will be excluded from the study; HIV-positive patients on combination antiretroviral therapy are ineligible * Patients with a history of seizure disorder requiring antiepileptics who have had a seizure episode within the last 6 months * Prior treatment with veliparib (ABT-888) or other PARP inhibitors (e.g., olaparib)