Inclusion Criteria:

          1. ≥ 18 years old at the time of informed consent

          2. Ability to provide written informed consent and HIPAA authorization

          3. Locally recurrent (not amenable to local therapy with curative intent) or metastatic
             breast cancer

               1. Patients with triple negative breast cancer must have received at least one prior
                  chemotherapy regimen for metastatic disease.

               2. Patients with hormone-positive, HER2-negative disease must have received
                  treatment with and progressed on at least one prior endocrine therapy including a
                  CDK4/6 inhibitor in the metastatic setting.

          4. Measurable or evaluable disease based on RECIST 1.1 criteria.

          5. Only subjects who have disease amenable to biopsy will be asked to consent to serial
             tumor biopsies. Consent for biopsy is not required for participation.

             a. NOTE: If no amendable disease is present at the time of biopsy, subjects may
             continue participation in the study and further study specific biopsies will not be
             required.

          6. Eastern Cooperative Oncology Group Performance Status 0 or 1

          7. Patients with treated, asymptomatic central nervous system (CNS) disease may
             participate if the patient is > 4 weeks from completion of CNS therapy (radiation
             and/or surgery), is clinically stable at the time of study entry, and is receiving a
             stable or decreasing dose of corticosteroid therapy. Brain MRI or head CT is required
             at screening for patients with known brain metastases.

          8. Adequate organ function as indicated by:

               1. Total bilirubin </= ULN (upper limit of normal) (except in patients with
                  documented Gilbert's disease, who must have a total bilirubin </= 3.0 mg/dL)

               2. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) </= 3.0 x ULN
                  (</= 1.5-3.0 x baseline if baseline is abnormal)

               3. Calculated creatinine clearance of >/= 60 mL/min using the Cockcroft-Gault
                  formula

               4. Absolute neutrophil count (ANC) >/= 1.5 K/mm3

               5. Platelets >/= 100 K/mm3

               6. Hemoglobin (Hgb) >/= 9.0 g/dL

          9. Women of childbearing potential must have a negative pregnancy test within 14 days of
             protocol registration. Women are considered to have childbearing potential (regardless
             of sexual orientation, having undergone a tubal ligation, or remaining celibate by
             choice) unless they meet one of the following criteria:

               1. Has undergone a hysterectomy or bilateral oophorectomy; or

               2. Has been naturally amenorrheic for at least 24 consecutive months.

         10. Women of childbearing potential and men must agree to use effective contraception
             throughout the study and for 7 months after the last study treatment. Note: Acceptable
             methods of birth control include abstinence, partner with previous vasectomy,
             placement of an intrauterine device (IUD), condom with spermicidal
             foam/gel/film/cream/suppository, diaphragm or cervical vault cap, or hormonal birth
             control (pills or injections).

        Exclusion Criteria:

          1. Prior treatment with decitabine, guadecitabine or other known DNA Methyltransferase
             inhibitors (DNMTis)

          2. Prior treatment with talazoparib or other known PARPi (poly(ADP-ribose polymeras
             inhibitor)

          3. Known deleterious breast cancer susceptibility gene (BRCA) mutation. Patients with
             BRCA variants of unknown significance (VUS) or who have not had germline genetic
             testing may participate.

          4. Active or symptomatic CNS disease

          5. Patients with HER2+ disease

               -  HER2 will be considered positive if scored 3+ by immunohistochemistry (IHC) or 2+
                  by IHC associated with a fluorescence in situ hybridization (FISH) ratio of > 2.0
                  or > 6 total HER2 gene copies per cell.

          6. Patients with active malignancy other than breast cancer. Patients with prior
             malignancies without recurrence after standard treatment will not be excluded

          7. Chemotherapy within 3 weeks of registration

          8. Radiation therapy within 2 weeks of registration

          9. Hormone therapy within 2 weeks of registration

         10. Patients requiring ongoing therapy with strong P-gp inhibitors