The following criteria is provided for health care professionals.

Key Inclusion Criteria:

• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1
• Confirmed diagnosis of active Multiple Myeloma (MM) by International Myeloma Working Group (IMWG) diagnostic criteria
• Patients must have symptomatic myeloma at the time of study entry with myeloma-related organ damage or tissue dysfunction
• Patients must have myeloma that is measurable by either serum or urine evaluation of the monoclonal component or by assay of serum free light chain (FLC)
• A patient with non-secretory MM may be considered for enrollment after discussion with the sponsor that includes the feasibility of the plan for response assessment according to IMWG guidelines
• Disease progression based on IMWG criteria
• Patients with MM who have exhausted all therapeutic options that are expected to provide meaningful clinical benefit, either through disease relapse, treatment refractory disease or intolerance or refusal of the therapy and including either:
• Progression on or after at least 3 lines of therapy, or intolerance of therapy, including a proteasome inhibitor, an Immunomodulatory agent (IMiD), and an anti-CD38 antibody, OR
• Progression on or after an anti-CD38 antibody and have disease that is "double refractory" to a proteasome inhibitor and an IMiD, or intolerance of therapy. The anti-CD38 antibody may have been administered alone or in combination with another agent such as a proteasome inhibitor. Refractory disease is defined as lack of response or relapse within 60 days of last treatment.
• Adequate hematologic and hepatic function
• Serum creatinine clearance by Cockcroft-Gault >30 mL/min

Key Exclusion Criteria:

• Presence of plasma cell leukemia, Waldenström macroglobulinemia (lymphoplasmacytic lymphoma), or POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes)
• Patients with known MM brain lesions or meningeal involvement with MM
• History of neurodegenerative condition or central nervous system (CNS) movement disorder
• Continuous systemic corticosteroid treatment with more than 10 mg of prednisone or anti-inflammatory equivalent within 72 hours of start of study drug
• Treatment with any systemic standard or investigational anti-myeloma therapy within 5 half-lives or within 28 days prior to first administration of study drug, whichever is shorter.
• Prior treatment with any anti-BCMA antibody (including antibody drug conjugate or bispecific antibody) or BCMA-directed CAR T therapy
• Uncontrolled infection with human immunodeficiency virus (HIV), hepatitis B virus (HBV) or hepatitis C virus (HCV) infection; or other uncontrolled infection
• A severe allergic reaction is defined for this purpose as that which has met criteria for common terminology criteria for adverse events (CTCAE) v5.0 grade 3 or grade 4 severity (ie, characterized by bronchospasm; or life-threatening consequences; or requiring intravenous (IV) intervention, other urgent intervention, or hospitalization for clinical sequelae) or that has required an emergency room visit.
• History of allogeneic stem cell transplantation at any time, or autologous stem cell transplantation within 12 weeks of the start of study treatment
• Known hypersensitivity to both allopurinol and rasburicase
• Pregnant or breastfeeding women
• Women of childbearing potential and men who are unwilling to practice highly effective contraception prior to the initial dose/start of the first treatment, during the study, and for at least 6 months after the last dose.

Note: Other protocol defined inclusion / exclusion criteria apply