A Study of the Safety and Pharmacokinetics of Venetoclax in Pediatric and Young Adult Patients With Relapsed or Refractory Malignancies

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.