Patient description: A 17 year old boy complains of vomiting, non-bloody diarrhea, abdominal pain, fever, chills and loss of appetite for the past 3 days. He ate a salad at a restaurant prior to his diarrhea onset. Physical exam was remarkable for pallor, jaundice, and diffuse abdominal tenderness. Lab results were as follows: Hemoglobin: 9.7 g/dL Platelet: 110,000 /cu.mm Creatinine: 3.6 mg/dL blood urea nitrogen (BUN): 73 mg/dL direct bilirubin: 2.4 mg/dL lactate dehydrogenase (LDH): 881 IU/L (normal: 110-265 IU/L) Peripheral blood smear showed a moderate number of schistocytes and helmet cells. Shiga-like toxin-producing E. coli (STEC) stx1/stx2 were found in stools. He has no other underlying disease and he is not on any medications.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Diffuse Large B Cell Lymphoma Key 1. Histologically confirmed non-germinal center diffuse large B cell lymphoma (DLBCL), by immunohistochemistry using the Hans algorithm, 1. CD10 and BCL6-, 2. CD10-, BCL6+, but MUM1+ 2. Men and women ≥ 18 years of age. 3. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. 4. Measurable disease is defined as at least 1 lymph node >1.5 cm in longest diameter and measurable in 2 perpendicular dimensions. 5. All participants must provide fresh tumor biopsy or recent tumor tissue samples (within 2 years of study entry [informed consent form signed]). 6. Received at least one prior therapy for DLBCL that includes anthracycline based chemotherapy. 7. Participant not eligible for or refuses intensive chemotherapy and hematopoietic stem cell transplant. 8. Documented failure to achieve at least partial response (PR) with, or documented disease progression after response to, the most recent treatment regimen. 9. Neutrophils ≥ 1 x 109/L independent of growth factor support within 7 days of study entry. 10. Platelets ≥ 75 x 109/L, independent of growth factor support or transfusion within 7 days of study entry 11. Creatinine clearance of ≥ 30 mL/min (as estimated by the Cockcroft-Gault equation or estimated glomerular filtration rate [eGFR]. 12. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 x ULN. 13. Bilirubin ≤ 2 x ULN (unless documented Gilbert's syndrome), then up to 5xULN allowed. 14. Independent of erythropoietin (EPO) support or transfusion within 7 days of first dose of study drug. 15. International normalized ratio (INR) ≤ 1.5 and activated partial thromboplastin time (APTT) ≤ 1.5 x ULN. 16. Participants may be enrolled who relapse after autologous stem cell transplant if they are at least 6 months after transplant, participants should have no active infections (ie, fungal or viral). 17. Females of childbearing potential must agree to use highly effective forms of birth control throughout the course of the study and at least up to 90 days after last dose of study drug. Highly effective forms of birth control can be defined as abstinence, hysterectomy, bilateral oophorectomy with no menstrual bleeding for up to 6 months, intrauterine contraception, hormonal methods such as contraceptive injection, oral contraceptive, etc. Males must have undergone sterilization-vasectomy, or utilize a barrier method where the female partner utilizes the effective forms of birth control noted above. 18. Life expectancy of > 3 months. 19. Able to provide written informed consent and can understand and comply with the requirements of the study. Key  Current or history of central nervous system (CNS) lymphoma. 2. Prior exposure to a BTK inhibitor. 3. Prior corticosteroids (at dosages equivalent to prednisone > 20 mg/day) given with anti-neoplastic intent within 7 days, prior chemotherapy, targeted therapy, or radiation therapy within 3 weeks, or antibody based therapies or Chinese anti-cancer herbal therapies within 4 weeks of the start of study drug. 4. Major surgery within 4 weeks of screening. 5. Toxicity of ≥ Grade 2 from prior anti-cancer therapy (except for alopecia, absolute neutrophil count (ANC) and platelets. For ANC and platelets, please follow #9 [neutrophils] and #10 [platelets]). 6. History of other active malignancies within 2 years of study entry, with exception of (1) adequately treated in-situ carcinoma of cervix; (2) localized basal cell or squamous cell carcinoma of skin; (3) previous malignancy confined and treated locally (surgery or other modality) with curative intent. 7. Currently active clinically significant cardiovascular disease such as uncontrolled arrhythmia, congestive heart failure, any Class 3 or 4 cardiac disease as defined by the New York Heart Association (NYHA) Functional Classification, or history of myocardial infarction within 6 months of screening. Left Ventricular Ejection Fraction (LVEF) is lower than 50% measured by echocardiography (ECHO) (AHA,2016). 8. QTcF (Fredericia's correction) > 450 msecs or other significant ECG abnormalities including second degree atrioventricular (AV) block Type II, or third degree AV block. 9. Unable to swallow capsules or disease significantly affecting gastrointestinal function such as malabsorption syndrome, resection of the stomach or small bowel, symptomatic inflammatory bowel disease, or partial or complete bowel obstruction. 10. Uncontrolled systemic infection or infection requiring parenteral anti-microbial therapy. 11. Known human immunodeficiency virus (HIV), or active hepatitis B or hepatitis C infection (detected positive by polymerase chain reaction [PCR]). 12. Pregnant or lactating women. 13. Any life-threatening illness, medical condition or organ system dysfunction which, in the investigator's opinion, could compromise the participant's safety, or put the study at risk. 14. On medications which are strong cytochrome P450, family 3, subfamily A (CYP3A) inhibitors or CYP3A inducers NOTE: Other protocol defined Inclusion/