Dose Schedule Study of BCMA Bispecific Antibody, Elranatamab, for Newly Diagnosed Immunoglobulin Light Chain (AL) Amyloidosis

This research study is for people who have newly diagnosed with AL (light chain) amyloidosis and have not yet received any treatment for this condition. The purpose of this study is to evaluate whether elranatamab, a type of immunotherapy drug, can produce deep remissions and organ recovery in people with newly diagnosed AL amyloidosis, and to compare two different dosing schedules. Elranatamab (brand name ELREXFIO™) is an investigational (experimental) drug in the setting of AL amyloidosis. It works by connecting immune cells (T-cells) directly to the abnormal plasma cells that are causing amyloidosis, triggering the immune system to destroy those cells. It is not approved by the Food and Drug Administration (FDA) for use in AL amyloidosis. Participants in this study will receive elranatamab as a series of injections under the skin (subcutaneously) over 6 treatment cycles (approximately 6 months). Treatment begins with inpatient "step-up" doses designed to reduce side effects, followed by two different dosing schedules based on which study arm participants are randomly assigned to. Participants will have regular blood tests, physical exams, bone marrow biopsies, and heart assessments throughout the study, and follow-up visits for up to 2 years after treatment ends. This study is randomized, meaning that participants will be assigned by chance (similar to a coin flip) to one of two treatment arms. Participants cannot choose their arm. Participation in this research will last approximately 6 months of active treatment, followed by follow-up visits for up to 2 years (with an option to extend to 5 years).