A Study of Venetoclax in Combination With Navitoclax and Chemotherapy in Subjects With Relapsed/Refractory Acute Lymphoblastic Leukemia or Relapsed/Refractory Lymphoblastic Lymphoma

Inclusion Criteria:

   - Must have relapsed or refractory acute lymphoblastic leukemia (ALL) or relapsed or
   refractory lymphoblastic lymphoma (LL). Refractory is defined as persistent disease
   after at least 2 courses of chemotherapy.

      - Participants with ALL with Philadelphia chromosome or with an ABL class
      targetable fusion are eligible.

      - Participants with LL must have radiographic evidence of disease

   - Participants <= 18 years of age who do not have a standard of care treatment option
   available.

   - Must weigh greater than or equal to 20 kg.

   - Must be able to swallow pills.

   - Must have adequate hepatic and kidney function.

   - Must have adequate performance status:

      - Participants less than or equal to 16 years of age: Lansky greater than or equal
      to 50

      - Participants greater than 16 years of age: Karnofsky greater than or equal to 50
      or Eastern Cooperative Oncology Group (ECOG) less than 3.

Exclusion Criteria:

   - Participant has central nervous system (CNS) disease with cranial involvement that
   requires radiation.

   - Participants who are less than 100 days post-transplant, or greater than 100 days
   post-transplant with active graft versus host disease (GVHD), or are still continuing
   post-transplant immunosuppressant therapy within 7 days prior to the first dose of
   study drug.

   - Participants who have received any of the following prior to the first dose of study
   drug:

      - Inotuzumab within 30 days (if participant received inotuzumab > 30 days prior to
      Day 1, must have ALT, AST and bilirubin < ULN).

      - A biologic agent (i.e., monoclonal antibodies) for anti-neoplastic intent within
      30 days

      - CAR-T infusion or other cellular therapy within 30 days

      - Any anti-cancer therapy including blinatumomab, chemotherapy, radiation therapy
      targeted small molecule agents or investigational agents within 14 days, or 5
      half-lives, whichever is shorter

         - Exception: Philadelphia Chromosome (Ph)+ ALL subjects on TKIs at Screening
         may enroll and remain on Tyrosine Kinase Inhibitor (TKI) therapy to control
         disease. Participants on venetoclax at screening may enroll and remain on
         venetoclax.

      - Steroid therapy for anti-neoplastic intent within 5 days

      - Hydroxyurea that is ongoing (hydroxyurea is permitted up to the first dose)

      - A strong or moderate CYP3A inhibitor or inducer within 7 days

      - Aspirin within 7 days, or 5 half-lives, whichever is longer

      - An excluded antiplatelet/anticoagulant drug or a herbal supplement that affects
      platelet function within 7 days, or 5 half-lives, whichever is longer

   - Participants with malabsorption syndrome or any other condition that precludes enteral
   administration.