The purpose of this study is to see how teclistamab by itself compares to study treatment combinations that are commonly used to treat multiple myeloma. These study treatment combinations are either pomalidomide, bortezomib and dexamethasone, called PVd, or carfilzomib and dexamethasone, called Kd. The patients will be randomly assigned to on of the study groups. The term randomized means something is done by chance or without any particular pattern, like flipping a coin to decide an outcome. Are you Eligible? (Inclusion Criteria) Are you at least 18 years of age or older? - Do you have a...