Characteristics of BsAbs. IgG-like BsAbs include an Fc region, while non–IgG-like BsAbs consist of only Fab (fragment antigen-binding) variable regions and linkers. Since the Fc portion provides stability and longevity to the molecule in circulation, most non–IgG-like BsAbs require more frequent dosing to maintain therapeutic plasma levels; they also lack the Fc-mediated effector functions such as antibody-dependent T-cellular cytotoxicity and complement-dependent cytotoxicity. Several BsAbs, both IgG-like and non–IgG-like, are under development for the treatment of MM. BiAb, bispecific antibodies.