CD55 and neoplasm: To confirm that the anti-CD55 antibody (4-1H) could be effectively incorporated into our asymmetric bispecific antibody (SBU) for simultaneous targeting of both CD55 and a tumor-associated antigen (e.g. CD20, HER2, or EGFR), the expression plasmid for CD55-scFv-FcKnob was co-transfected into Expi293F cells with a plasmid encoding single-chain Fabs (CD20-scFab-FcHole, HER2-scFab-FcHole, or EGFR-scFab-FcHole derived from the variable regions of rituximab, trastuzumab, or cetuximab, respectively) (Fig. 3a,b).