Inclusion Criteria:

          -  Participants must have relapsed or refractory cancer.

          -  Participants must have adequate hepatic and kidney function.

          -  Participants less than or equal to 16 years of age must have performance status of
             Lansky greater than or equal to 50% and participants greater than 16 years of age must
             have performance status of Karnofsky greater than or equal to 50%.

          -  Participants with solid tumors (with the exception of neuroblastoma) must have
             adequate bone marrow function in Part 1.

          -  For the fifth cohort during Part 2 Cohort Expansion, participants with solid tumors
             must have evidence of BCL-2 expression (except participants with TCF3-HLF ALL).

        Exclusion Criteria:

          -  Participants with primary brain tumors or disease metastatic to the brain.

          -  Participants who have central nervous system (CNS) disease with cranial involvement
             that requires radiation.

          -  Participants who have received any of the following within the listed time frame,
             prior to the first dose of study drug

               -  Inotuzumab ozogamicin or gemtuzumab ozogamicin within 30 days

               -  Biologic agent (i.e., antibodies) for anti-neoplastic intent within 30 days or 5
                  half-lives whichever is shorter.

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

               -  Anticancer therapy including chemotherapy, radiation therapy, targeted small
                  molecule agents, investigational agents within 14 days or 5 half-lives, whichever
                  is shorter (Exceptions: Ph+ALL participants on Tyrosine Kinase Inhibitor (TKI) at
                  Screening may enroll and remain on TKI therapy to control disease and TCF3-HLF
                  ALL participants are allowed to have received chemotherapy within 14 days or 5
                  half-lives, whichever is shorter).

               -  Steroid therapy for anti-neoplastic intent within 5 days (with the exception of
                  TCF3-HLF ALL participants).

               -  Requires ongoing hydroxyurea (hydroxyurea permitted up to first dose)

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

          -  Participants who are less than 6 weeks post-131 I-metaiodobenzylguanidine (mIBG)
             therapy.

          -  Participants who have received the following within 7 days prior to the first dose of
             study drug:

               -  Strong and moderate Cytochrome P450 3A (CYP3A) inhibitors (Part 1 Dose
                  Determination);

               -  Strong and moderate CYP3A inducers (Part 1 Dose Determination and Part 2 Cohort
                  Expansion).

          -  Participants who have not recovered from clinically significant adverse
             effect(s)/toxicity(s) of the previous therapy (Exception: Chemotherapy induced side
             effects that are expected to return to baseline in TCF3-HLF ALL participants).

          -  Participants who have active, uncontrolled infections.

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

               -  Participants with recent positive test for SARS-CoV-2 (COVID-19) and no follow up
                  test with negative result cannot be enrolled. Participants with contact to
                  persons with COVID-19 and participants with signs and symptoms for COVID-19
                  infection must be tested before enrolling.