This study is testing new treatments for multiple myeloma, a type of blood cancer. The study uses two medicines, talquetamab and teclistamab, to see if they work better together than alone. It includes different phases: finding the right dose and schedule, checking safety, and testing how well the medicines work. Participants will be in the study for about 5 years.

Multiple myeloma involves harmful proteins called M proteins. The study aims to kill the cancer cells by targeting proteins on their surface. Participants will go through a screening phase (up to 28 days), a treatment phase, and a follow-up phase (up to 16 weeks after the last treatment).

To join, participants must have multiple myeloma that has come back or is not responding to other treatments. They should not have had certain prior therapies or conditions, like recent stem cell transplants or specific other blood cancers.

• The study lasts approximately 5 years, with several phases.
• Participants will receive a combination of two medicines.
• Close monitoring of safety and treatment effects will occur.