Study to Assess the Safety and Tolerability of REGN5837 in Combination With Odronextamab in Patients With Relapsed or Refractory Aggressive B-cell Non-Hodgkin Lymphoma

The primary objective of the study is:To assess the safety, tolerability, and dose-limiting toxicities (DLTs) and to determine recommended phase 2 dose (RP2D) regimen(s) (defined as either a maximum tolerated dose (MTD) regimen or a lower dose regimen) of REGN5837 in combination with odronextamab in patients with relapsed or refractory aggressive B-cell non-Hodgkin lymphoma (B-NHL)The secondary objectives of the study are:To evaluate the pharmacokinetics (PK) of REGN5837 when given in combination with odronextamabTo evaluate the PK of odronextamab when given in combination with REGN5837To assess the immunogenicity of REGN5837 and odronextamabTo assess the preliminary anti-tumor activity of REGN5837 in combination with odronextamab in patients with relapsed or refractory aggressive B-NHL

Key Inclusion Criteria:Have documented CD20+ aggressive B-NHL, with disease that has progressed after at least 2 lines of systemic therapy containing an anti-CD20 antibody and an alkylating agent.Measurable disease on cross sectional imaging as defined in the protocolEastern Cooperative Oncology Group (ECOG) performance status 0 or 1Adequate bone marrow, renal and hepatic function as defined in the protocolDuring dose expansion phase of the study, participant should be willing to undergo mandatory tumor biopsies, if in the opinion of the investigator, the participants has an accessible lesion that can be biopsied without significant risk to the participant.Key Exclusion Criteria:Prior treatments with allogeneic stem cell transplantation or solid organ transplantation, treatment with anti-CD20 x anti- CD3 bispecific antibody, such as odronextamabDiagnosis of mantle cell lymphoma (MCL)Primary central nervous system (CNS) lymphoma or known involvement by non-primary CNS lymphomaTreatment with any systemic anti-lymphoma therapy within 5 half-lives or within 14 days prior to first administration of study drug, whichever is shorterStandard radiotherapy within 14 days of first administration of study drug.Continuous systemic corticosteroid treatment with more than 10 mg per day of prednisone or corticosteroid equivalent within 72 hours of start of odronextamabCo-morbid conditions, as described in the protocolInfections, as described in the protocolAllergy/hypersensitivity: Known hypersensitivity to both allopurinol and rasburicaseNOTE: Other protocol defined inclusion / exclusion criteria apply