Inclusion Criteria:
Main Inclusion Criteria:
• Must be at least 20 years of age, inclusive
• Japanese participants
• CD20 positivity at representative tumor biopsy
1. Part 1:
* Diffuse large B-cell lymphoma (de novo or histologically transformed)
* High-grade B-cell lymphoma
* Primary mediastinal large B-cell lymphoma
* Follicular lymphoma
* Marginal zone lymphoma (nodal, extranodal of mucosa-associated lymphoid tissue, or splenic)
* Small lymphocytic lymphoma
2. Part 2 :
Arm 1:
* Diffuse large B-cell lymphoma (de novo or histologically transformed)
* Follicular lymphoma grade 1-3A
* Relapsed or refractory disease and previously treated with at least 2 lines of systemic antineoplastic therapy including at least 1 anti-CD20 monoclonal antibody (mAb)-containing therapy.
* Measurable disease by computed tomography (CT), magnetic resonance imaging (MRI) or positron emission tomography (PET)-CT scan
Arm 2:
• R/R FL grade 1, 2 or 3a, stage II, III, or IV, without evidence of transformation.
* Previously treated with at least 1 prior anti-neoplastic agent, including anti-CD20 antibody
* Must have a need for treatment initiation based on symptoms and/or disease burden (Groupe d'Etude des Lymphomes Folliculaires \[GELF\] criteria)
* Eligible to receive R2 per investigator determination
Arm 3:
* One of following confirmed histologies (de novo or histologically transformed from FL or nodal marginal zone lymphoma) :
o DLBCL, not otherwise specified (NOS)
* "Double-hit" or "triple-hit" DLBCL
* FL Grade 3B.
* T-cell/histiocyte rich large B-cell lymphoma (LBCL)
* International Prognostic Index (IPI) score ≥3
* No prior therapy for DLBCL or FL grade 3B (G3B) other than nodal biopsy, corticosteroids, or palliative radiotherapy.
* Eligible to receive R-CHOP per investigator determination
Arm 4:
* One of following confirmed histologies (de novo or histologically transformed from FL or nodal marginal zone lymphoma) including:
o DLBCL, NOS.
o "Double-hit" or "triple-hit" DLBCL
* FL Grade 3B.
* T-cell/histiocyte rich LBCL
* Relapsed or refractory to at least one prior therapy including at least one prior anti-CD20 antibody.
* Either failed prior autologous hematopoietic stem cell transplantation (ASCT), or ineligible for autologous hematopoietic stem-cell transplantation (HSCT)
* Eligible to receive GemOx per investigator determination
Arm 5:
• History of histologically confirmed CD20+ FL Grade 1-3a without evidence of transformation.
• In CR or PR per Lugano criteria following first-line or second-line treatment with SOC regimen, including anti-CD20 antibody, and last dose of SOC within 6 months prior to enrollment
Main Exclusion Criteria:
• Primary central nervous system (CNS) lymphoma or CNS involvement by lymphoma at screening
• Participants not eligible for high dose therapy with autologous hematopoietic stem cell transplantation due to personal choice, social issues, or similar
• Known clinically significant cardiac disease
• Chronic ongoing infectious diseases requiring treatment (excluding prophylactic treatment)
Exclusion criteria for Part 2, Arms 2 through 5:
Arm 2:
• FL Grade 3b
• Histologic evidence of transformation to an aggressive lymphoma
* Contraindication to rituximab or lenalidomide
* Unwilling or unable to take aspirin prophylaxis or prophylactic anticoagulant as clinically indicated
Arm 3:
• Contraindication to any of the individual drugs of the R-CHOP regimen
Arm 4:
* Contraindication to any of the individual drugs of the GemOx regimen
Arm 5:
* FL Grade 3b
* Histologic evidence of transformation to an aggressive lymphoma
