Study to Compare the Effectiveness and Safety of Golcadomide Plus R-CHOP vs Placebo Plus R-CHOP in Participants With Previously Untreated High-risk Large B-cell Lymphoma

Inclusion Criteria:

• Histologically confirmed (per local evaluation) diagnosis of de novo, previouslyuntreated large B-cell lymphoma (LBCL) according to 2022 world health organization (WHO) classification including:

i) Diffuse large B-cell lymphoma (DLBCL), not otherwise specified [including germinal center B-cell (GCB) and activated B-cell (ABC) types]

ii) High-grade B-cell lymphoma, with MYC and BCL2 rearrangements (HGBL-MYC/BCL2 double-hit lymphomas)

iii) High-grade B-cell lymphoma, not otherwise specified

iv) T-cell/histiocyte/rich large B-cell lymphoma (THRLBCL)

v) Epstein-Barr virus + DLBCL

• International Prognostic Index (IPI) score 1 or 2 with lactate dehydrogenase (LDH) > 1.3 x upper limit of normal (ULN) and/or bulky disease defined as single lesion of ≥ 7 cm OR IPI ≥ 3.

• Measurable disease defined by at least 1 fluorodeoxyglucose (FDG)-avid lesion forFDG-avid subtype and 1 bi-dimensionally measurable (> 1.5 cm in longest diameter)disease by computed tomography (CT) or magnetic resonance imaging (MRI), as definedby the Lugano classification.

• Must have Ann Arbor Stage II-IV disease.

Exclusion Criteria:

• Any significant medical condition, active infection, laboratory abnormality, orpsychiatric illness that would prevent the participant from participating in thestudy.

• Any other subtype of lymphoma. Cases of primary mediastinal (thymic) large B-celllymphoma (PMBCL), primary cutaneous DLBCL-leg type, Grade 3b FL, indolent lymphomatransformed to large B-cell lymphoma (LBCL), Anaplastic lymphoma kinase (ALK)positive large B-cell lymphoma, primary effusion lymphoma, and Burkitt lymphoma.

• Documented or suspected central nervous system (CNS) involvement by lymphoma.

• Other protocol-defined Inclusion/Exclusion criteria apply.