Daratumumab will be administered as SC injection.

Lenalidomide will be administered orally.

Dexamethasone will be administered either orally or intravenously (IV).

Talquetamab will be administered as SC injection.

Sustained MRD-negative CR is defined as participants with CR or better who sustain MRD-negative status, as determined by NGS with sensitivity of 10^-5, for at least 12 months without any examination showing MRD positive status or progressive disease in between.

MRD-negative CR is defined as the percentage of participants who achieve MRD-negative status, as determined by NGS with sensitivity of 10^-5, at any time after randomization and prior to progressive disease or subsequent antimyeloma therapy and who achieve CR or better.

PFS2 is defined as the time interval between the date of randomization and date of event, which is defined as progressive disease as assessed by investigator that starts after the next line of subsequent therapy, or death from any cause, whichever occurs first.

OS is defined as the time from the date of randomization to the date of death due to any cause.

An adverse event is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non-investigational) product. An adverse event does not necessarily have a causal relationship with the treatment. Severity will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0. Severity scale ranges from Grade 1: mild, Grade 2: moderate, Grade 3: severe, Grade 4: life-threatening, and Grade 5: death related to adverse event.

Number of participants with abnormalities in laboratory parameters (serum chemistry and hematology) will be reported.

Number of participants with abnormalities in vital signs (temperature, pulse/heart rate, respiratory rate, blood pressure) will be reported.

Number of participants with abnormalities in physical examination will be reported.

Number of participants with abnormalities in ECG will be reported.

Serum samples will be analyzed to determine concentrations of teclistamab and talquetamab using validated, specific, and sensitive methods.

Number of participants with ADAs to teclistamab and talquetamab will be reported.

The EORTC-QLQ-C30 Version 3 includes 30 items that make up 5 functional scales (physical, role, emotional, cognitive, and social), 1 global health status scale, 3 symptom scales (pain, fatigue, and nausea/vomiting), and 5 single symptom items (dyspnea, insomnia, appetite loss, constipation, and diarrhea) and a single impact item (financial difficulties). The recall period is 7 days ("past week"), and responses are reported using a verbal and numeric rating scales. The item and scale scores are transformed to a 0 to 100 scale. A high scale score represents a higher response level. Thus, a high score for a functional scale represents a high/healthy level of functioning and a high score for the global health status represents high HRQoL, but a high score for a symptom scale/item represents a high level of symptomatology/problems.

The National Cancer Institute's (NCI's) PRO-CTCAE is an item library of common AEs experienced by people with cancer that are appropriate for self-reporting of treatment tolerability. Each symptom selected for inclusion can be rated by up to 3 attributes characterizing the presence/frequency, severity, and/or interference of the AEs. It ranges from 0 to 4 with higher scores indicating higher frequency or greater severity/impact.

The EQ-5D-5L is a 5-item questionnaire that assesses 5 domains including mobility, self-care, usual activities, pain/discomfort, and anxiety/depression plus a visual analog scale rating "health today" with anchors ranging from 0 (worst imaginable health state) to 100 (best imaginable health state).

Time to sustained worsening in symptoms, functioning and HRQoL is defined as the interval from the date of randomization to the start date of meaningful change.