Study of Selinexor in Combination With Backbone Treatments or Novel Therapies In Participants With Relapsed or Refractory (RR) Diffuse Large B-Cell Lymphoma (DLBCL)

Exclusion Criteria

• •1. DLBCL with mucosa-associated lymphoid tissue (MALT) lymphoma; composite lymphoma (Hodgkin lymphoma + NHL); Gray zone lymphoma; DLBCL transformed from Chronic Lymphocytic Leukemia (Richter Syndrome); Primary mediastinal large B-cell lymphoma (PMBCL); T-cell rich large B-cell lymphoma.
• •2. Previous treatment with selinexor or other XPO1 inhibitors.
• •3. Contraindication to any drug contained in the different treatment arms.
• •4. Use of any standard or experimental anti-DLBCL therapy (including nonpalliative radiation, chemotherapy, immunotherapy, radio-immunotherapy, or any other anticancer therapy) \<21 days prior to Cycle 1 Day 1 (C1D1). Low dose steroids \<30 mg prednisone (or equivalent) and palliative radiotherapy are permitted.
• •5. Received strong cytochrome P450 3A (CYP3A) inhibitors ≤7 days prior to Day 1 dosing or strong CYP3A inducers ≤14 days prior to Day 1 dosing.
• •6. Any AE, by Cycle 1 Day 1 (C1D1), which has not recovered to Grade ≤1 (CTCAE, v. 5.0), or returned to baseline, related to the previous DLBCL therapy, except alopecia.
• •7. Major surgery \<14 days of C1D1.
• •8. Autologous stem cell transplant (SCT) \<100 days or allogeneic SCT \<180 days prior to C1D1 or active graft-versus-host disease after allogeneic SCT (or cannot discontinue graft versus host disease \[GVHD\] treatment or prophylaxis).
• •9. Prior chimeric antigen receptor T cell (CAR-T cell) infusion at any time (Phase 1 only); prior CAR-T cell infusion ≤120 days prior to C1D1 (Phase 2 only).
• •10. Any life-threatening illness, medical condition, or organ system dysfunction which, in the Investigator's opinion, could compromise the participant's safety, or able to comply with the study procedures.
• •11. Uncontrolled (i.e., clinically unstable) infection requiring parenteral antibiotics, antivirals, or antifungals within 7 days prior to first dose of study treatment; however, prophylactic use of these agents is acceptable (including parenteral).
• •12. Inability to swallow tablets, malabsorption syndrome, or any other GI disease or dysfunction that could interfere with absorption of study treatment.
• •13. Breastfeeding women or pregnant women.
• •14. Inability or unwillingness to sign informed consent form.
• •15. In the opinion of the Investigator, participants who are below their ideal body weight and would be unduly impacted by changes in their weight.
• •16. Known allergy to any of the drug planned to be given.
• •17. Arm B (S-PR): Serum total bilirubin \>1.5 \* ULN, Neuropathy Grade ≥2 (CTCAE, v5.0).
• •18. Arm C (S-PBR): Serum total bilirubin \>1.5 \* ULN, Neuropathy Grade ≥2 (CTCAE, v5.0).
• •19. Arm D (S-R-GemOx): Neuropathy Grade 2≥ (CTCAE, v5.0) interstitial lung disease or pulmonary fibrosis.