Inclusion Criteria:

          -  Patients with previously untreated acute lymphoblastic leukemia (B-cell or T-cell)

          -  Bone marrow involvement with ≥20% lymphoblasts

          -  Age ≥ 60 Years

        OR

          -  Patients with relapsed or refractory acute lymphoblastic leukemia (B-cell or T-cell)
             defined as receiving one or more cytotoxic containing regimens

          -  Bone marrow involvement with ≥5% lymphoblasts

          -  Age ≥ 18 Years

          -  Eastern Cooperative Oncology Group (ECOG) performance status ≤2 (Refer to Appendix D)

          -  Adequate organ function

               -  Serum total bilirubin ≤1.5 x upper limit of normal (ULN) or ≤3 x ULN for patients
                  with Gilbert's disease

               -  Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤3.0 x ULN,
                  unless clearly due to disease involvement

               -  Creatinine clearance >50 mL/min (calculated according to institutional standards
                  or using Cockcroft-Gault or Modification of Diet in Renal Disease (MDRD) formula)

          -  Women of childbearing potential must have a negative serum or urine beta human
             chorionic gonadotropin (β-hCG) pregnancy test result within 14 days prior to the first
             dose of study drugs and must agree to use an effective contraception method during the
             study and for 30 days following the last dose of study drug. Women of non-
             childbearing potential are those who are postmenopausal greater than 1 year or who
             have had a bilateral tubal ligation or hysterectomy. Men who have partners of
             childbearing potential must agree to use an effective contraceptive method during the
             study and for 30 days following the last dose of study drug

          -  Patients or their legally authorized representative must provide written informed
             consent

        Exclusion Criteria:

          -  Ph-positive ALL, Burkitt's leukemia/lymphoma, or lymphoblastic lymphoma

          -  Patient is pregnant or breastfeeding

          -  Patients with uncontrolled infection

          -  Hepatitis B or C infection, or known seropositivity for human immunodeficiency virus
             (HIV)

          -  Major surgery or radiation therapy within 4 weeks prior to the first study dose

          -  Systemic chemotherapy/radiotherapy/investigational therapy within 14 days (with the
             exception of hydroxyurea and/or dexamethasone, or one dose of cytarabine) prior to
             starting therapy

          -  Symptomatic or untreated leptomeningeal disease or spinal cord compression

          -  Patients with active heart disease (New York Heart Association (NYHA) class 3-4 as
             assessed by history and physical examination, unstable angina/stroke/myocardial
             infarction within the last 6 months)

          -  Patients with a cardiac ejection fraction (as measured by either Multi Gated
             Acquisition (MUGA) or echocardiogram (EKG)) <40%

          -  History of another primary invasive malignancy that has not been definitively treated
             or in remission for at least 2 years. Patients with non-melanoma skin cancers or with
             carcinomas in situ are eligible regardless of the time from diagnosis (including
             concomitant diagnoses)

          -  Concurrent use of warfarin

          -  Received Cytochrome P450 3A (CYP3A) inhibitors (such as fluconazole, ketoconazole,
             voriconazole, and clarithromycin) within 3 days of starting venetoclax; received
             strong CYP3A inducers (such as rifampin, rifabutin, phenytoin, carbamazepine, and St.
             John's Wort) within 3 days of starting venetoclax

          -  Consumed grapefruit, grapefruit products, Seville oranges, or star fruit within 3 days
             prior to starting venetoclax

          -  Prior treatment with venetoclax

          -  Malabsorption syndrome or other conditions that preclude enteral route of
             administration

          -  Other severe acute or chronic medical or psychiatric condition or laboratory
             abnormality that in the opinion of the investigator may increase the risk associated
             with study participation or investigational product administration or may interfere
             with the interpretation of study results and/or would make the patient inappropriate
             for enrollment into this study