Phase 1/2 Dose Finding and Safety Study of Ibrutinib in Pediatric Subjects With Chronic Graft Versus Host Disease (cGVHD)

Key Eligibility: Inclusion Criteria: 1. Part A: Subjects with moderate or severe cGVHD after failure of 1 or more lines of systemic therapy 2. Part B: Subjects with moderate or severe cGVHD after failure of 1 or more lines of systemic therapy, or subjects with new onset moderate or severe cGVHD and in need of systemic immunosuppression 3. History of allogeneic stem cell transplantation 4. Age * Part A: ≥1 to \<12 years of age at the time of enrollment * Part B: ≥1 to \<22 years of age at the time of enrollment 5. Karnofsky or Lansky (subjects \<16 years of age) performance status ≥60 Key Eligibility: Exclusion Criteria: 1. Presence of single organ genito-urinary involvement as the only manifestation of cGVHD 2. Received an investigational agent within 28 days before enrollment. 3. Received donor lymphocyte infusion (DLI) within 56 days before enrollment 4. Progressive underlying malignant disease or active post-transplant lymphoproliferative disease 5. Any uncontrolled infection or active infection requiring ongoing systemic treatment 6. Known bleeding disorders 7. Active hepatitis C virus (HCV) or hepatitis B virus (HBV)