From date of randomization to date of progressive disease, discontinuation from study, death, or censoring, whichever occurs first

Progression Free Survival assessed by Blinded Independent Central review per IMWG response criteria

CRS: supraphysiologic response following any immune therapy that results in the activation or engagement of endogenous or infused T-cells and/or other immune effector cells. Symptoms must include fever at the onset, and may include hypotension, hypoxia and end organ dysfunction. As per ASTCT criteria, Grade (G) 1: fever (temperature \>=38 degree Celsius), hypotension and/or hypoxia none; G 2: fever, hypotension not requiring vasopressors, hypoxia requiring low-flow nasal cannula/ facemask or blow-by; G 3: fever, hypotension requiring a vasopressor with or without vasopressin, hypoxia requiring high-flow nasal cannula/ facemask, nonrebreather mask, or Venturi mask; G 4: fever, hypotension requiring multiple vasopressors (excluding vasopressin), hypoxia requiring positive pressure. Organ toxicities associated with CRS graded according to CTCAE v5.0. G 1: Mild, G 2: Moderate, G 3: severe, and G 4: life-threatening consequences; urgent intervention indicated. G 5: death related to AE.

ORR: % of participants with best overall response of confirmed stringent complete response (sCR), CR, very good partial response (VGPR) or PR per IMWG criteria. sCR: CR \& normal serum free light chain (sFLC) ratio \& absence of clonal cells in BMB/BMA by IH, IF, or flow cytometry. CR: negative immunofixation on serum \& urine, disappearance of any soft tissue plasmacytoma \& \<5% plasma cells in BMA, if disease measurable by sFLC only, preceding criteria plus normal sFLC ratio. VGPR: Serum \& urine M-protein detectable by immunofixation but not on electrophoresis; or \>=90% reduction in serum M-protein \& urine M-protein level \<100mg/24h. PR: \>=50% reduction in serum M-protein \& reduction in 24h urinary M-protein by \>=90% or \<200 mg/24h. If serum \& urine M-protein were unmeasurable, VGPR \& PR: \>=90% \& \>=50% decrease in difference respectively between involved \& uninvolved sFLC levels \& if present at baseline, \>=90% \& \>=50% reduction in soft tissue plasmacytomas' size.

Dose limiting toxicity rate based on dose limiting toxicity evaluable participants

Number of participants with AE among participants who take at least 1 dose of study intervention. AEs are categorized by seriousness and relationship to treatment. Relatedness to study drug is assessed by investigator.

Dose limiting toxicity rate based on dose limiting toxicity evaluable participants.

Dose limiting toxicity based on dose limiting toxicity evaluable participants.

Dose limiting toxicity rate based on dose limiting toxicity evaluable participants.

Hematological: Grade 4 neutropenia lasting \>5 days; Febrile neutropenia \<1000/mm\^3 with a single temperature of \>38.3 degree Celsius (C) or a sustained temperature of \>=38 degree C for more than one hour; grade \>=3 neutropenia with infection; grade 4 thrombocytopenia; grade 3 thrombocytopenia with \>= Grade 2 bleeding. Non-hematological: grade 4 adverse events (AEs); Grade 3 AE lasting \>=5 days despite optimal supportive care, with exception of AE attributed to cytokine release syndrome (CRS) event; grade 3 CRS, except those CRS that had a) not been maximally treated or b) improved to \<=grade 1 within 48 hours; grade 4 CRS; confirmed drug-induced liver injury (DILI) meeting Hy's law criteria; grade 4 laboratory abnormalities deemed clinically significant by the investigator reported Grade 4 AE; clinically important or persistent toxicities that were not included in above criteria were also be considered a DLT following review by the investigators and the sponsor.

ORR per IMWG criteria: percentage of participants with best overall response (BOR) of stringent complete response (sCR), complete response (CR), very good partial response (VGPR) or partial response (PR). sCR: complete response plus normal free light chain (FLC) ratio and absence of clonal cells in bone marrow biopsy by immunohistochemistry; CR: negative immunofixation on serum and urine and disappearance of any soft tissue plasmacytomas and \<5% plasma cells in bone marrow aspirates. VGPR: serum and urine M-protein detectable by immunofixation but not on electrophoresis or \>=90% reduction in serum M-protein plus urine M-protein level \<100 mg/24 hr. PR: \>=50% reduction of serum M-protein and reduction in 24 hrs urinary M-protein by \>=90% or to \<200 mg/24 hr. If serum and urine M-protein were unmeasurable, \>=50% decrease in difference between involved and uninvolved FLC levels required in place of the M-protein criteria.

DOR per IMWG criteria:time from first documentation of objective tumor (OT)response to first documentation of OTprogression or to death due to any cause, whichever occurred first.sCR: CR plus normal FLC ratio \& absence of clonal cells in bone marrow biopsy by immunohistochemistry;CR:Negative immunofixation on serum \& urine \& disappearance of any soft tissue plasmacytomas\&\<5% plasma cells in bone marrow aspirates.VGPR: serum \& urine M-protein(Mp) detectable by immunofixation but not on electrophoresis or \>=90% reduction in serum Mp plus urine Mp level \<100 mg/24 hr. PR: \>=50% reduction of serum Mp \& reduction in 24 hrs urinary Mp by \>=90% or to \<200 mg/24 hr.If serum \& urine Mp were unmeasurable, \>=50% decrease in difference between involved \& uninvolved FLC levels required in place of Mp criteria. Progression: appearance of local, regional or distant disease of same type after CR or progression of pre-existing lesions. It did not include second primary malignancies of unrelated types.