Patient description: The patient is a 42 year-old postmenopausal woman who had a screening sonogram which revealed an abnormality in the right breast. She had no palpable masses on breast exam. Core biopsy was done and revealed a 1.8 cm infiltrating ductal breast carcinoma in the left upper outer quadrant. Lumpectomy was done and the surgical margins were clear. The tumor was HER2-positive and ER/PR negative. Axillary sampling revealed 1 positive lymph node out of 12 sampled. CXR was unremarkable. She is using “well women” multivitamins daily and no other medication. She smokes frequently and consumes alcohol occasionally. She is in a relation with only one partner and has a history of 3 pregnancies and live births. She breastfed all three children.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Locally Advanced Unresectable Breast Carcinoma Metastatic Breast Carcinoma Recurrent Breast Carcinoma Stage IIIB Breast Cancer AJCC v7 Stage IIIC Breast Cancer AJCC v7 Stage IV Breast Cancer AJCC v6 and v7 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 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  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