The present invention provides multispecific antigen-binding molecules and methods of making or selecting same. The multispecific antigen-binding molecules comprise a first antigen-binding domain that specifically binds a target molecule, and a second antigen-binding domain that specifically binds an internalizing effector protein. The multispecific antigen-binding molecules of the present invention can, in some embodiments, be bispecific antibodies that are capable of binding both a target molecule and an internalizing effector protein. In certain embodiments of the invention, the simultaneous binding of the target molecule and the internalizing effector protein by the multispecific antigen-binding molecule of the present invention results in the attenuation of the activity of the target molecule to a greater extent than the binding of the target molecule alone. In other embodiments of the invention, the target molecule is a tumor associated antigen, and the simultaneous binding of the tumor associated antigen and the internalizing effector protein by the multispecific antigen-binding molecule of the present invention causes or facilitates the targeted killing of tumor cells.