Study of Selinexor in Combination With Backbone Treatments or Novel Therapies In Participants With Relapsed or Refractory (RR) Diffuse Large B-Cell Lymphoma (DLBCL)
Study of Selinexor in Combination With Backbone Treatments or Novel Therapies In Participants With Relapsed or Refractory (RR) Diffuse Large B-Cell Lymphoma (DLBCL)
This is a Phase 1/2, multicenter, open-label study to evaluate the efficacy, and safety of
 various combinations with selinexor in participants with RR DLBCL. The study will be
 conducted in two phases: Phase 1 and 2. The Phase 1 of the study will be a standard 3 + 3
 dose escalation to determine the maximal tolerated dose (MTD), recommended Phase 2 dose
 (RP2D) for each treatment arm, and assess the dose limiting toxicities (DLTs). The Phase 2 of
 the study will be a dose expansion study to assess the efficacy and safety of for RP2D
 selected at the end of Phase 1 of the study for each treatment arm.
Inclusion Criteria:

 1. Participants greater than or equal to (≥) 18 years of age.

 2. Pathologically confirmed de novo DLBCL or DLBCL transformed from previously diagnosed
 indolent lymphoma (e.g., follicular lymphoma).

 3. Prior lines of systemic therapy for the treatment of DLBCL:

 -  For Arms A, B, C, E, F, H: Participants must have received at least 1 but no more
 than 3 prior lines of systemic therapy for the treatment of DLBCL.

 -  For Arm D (S-R-GemOx) participants must have received at least 1 but not more
 than 2 lines of systemic therapy (Documentation to be provided).

 -  For Arm G (S-LT) participants must have received only 1 line of systemic therapy

 4. Positron emission tomography (PET) positive measurable disease per the Lugano
 Classification 2014, having at least 1 node with longest diameter (LDi) greater than
 (>) 1.5 centimetres (cm) or 1 extranodal lesion with LDi >1 cm.

 5. Adequate bone marrow function.

 6. Circulating lymphocytes less than or equal to (≤) 50 * 109/L.

 7. Adequate liver and kidney function.

 8. Eastern Cooperative Oncology Group (ECOG) performance status of ≤2.

 9. An estimated life expectancy of >6 months at Screening.

 10. Participants with primary refractory disease defined as no response or relapse within
 6 months after ending first-line treatment will be allowed on study (up to 20
 percentage [%] of enrolled participants in each Phase).

 11. Male participants and female participants of childbearing potential must agree to use
 highly effective methods of contraception: Male participants must agree not to donate
 sperm.

 12. Participants with active hepatitis B Virus (HBV) are eligible if antiviral therapy for
 hepatitis B has been given for >8 weeks and viral load is <100 international units per
 milliliter (IU/mL); participants with hepatitis C Virus (HCV) are eligible if viral
 load is negative; participants with human immunodeficiency virus (HIV) are eligible if
 cluster of differentiation 4 (CD4+) T-cell counts ≥350 cells per microliter
 (cells/μL), viral load is negative and no history of acquired immunodeficiency
 syndrome (AIDS)-defining opportunistic infections in the last year.

 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. Participants with high grade lymphoma with c-MYC, B-cell lymphoma 2 (BCL-2) and/or
 BCL-6 rearrangements are excluded from the Phase 1 portion of the study only.

 3. Previous treatment with selinexor or other XPO1 inhibitors.

 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) are permitted; and palliative radiotherapy.

 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. Major surgery <14 days of C1D1.

 7. 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).

 8. 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).

 The following are Arm Specific exclusion criteria:

 9. Arm B (S-PR): Serum total bilirubin >1.5 * ULN, Neuropathy Grade ≥2 (CTCAE, v5.0).

 10. Arm C (S-PBR): Serum total bilirubin >1.5 * ULN, Neuropathy Grade ≥2 (CTCAE, v5.0).

 11. Arm D (S-R-GemOx): Neuropathy Grade 2≥ (CTCAE, v5.0) interstitial lung disease or
 pulmonary fibrosis.