Additional Study Information: The purpose of this study is to see how safe and effective is the study drug, ABBV-383. ABBV-383 works by binding to a specific protein called B-cell maturation antigen, which is found on the surface of cells affected by amyloidosis. By engaging T-cells, a type of white blood cell, ABBV-383 helps activate the immune response to target and remove the abnormal proteins that cause amyloidosis. The study drug ABBV-383, is not approved by the U.S Food and Drug Administration (FDA).