Structure of anti-BCMA bispecific antibodies. Anti-BCMA BsAb can be classified into immunoglobulin G (IgG)-like and non-IgG-like based on their structures. IgG-like BsAb consist of antibody binding fragments (Fab) which recognize target antigens, and a crystallizable fragment (Fc). In addition to having one Fab targeting CD3 (anti-CD3ε), BsAb with monovalent BCMA Fab consists of one Fab targeting BCMA (anti-BCMA). BsAb with bivalent BCMA Fabs are designed with either two anti-BCMA Fabs or two anti-BCMA variable domain of heavy chains (VH). Non-IgG BsAb, AMG420, is synthesized as tandem single chain Fvs and lacks Fc. CH, constant domain of heavy chain; CL, constant domain of light chain; Fv, variable fragment; VL, variable domain of light chain.