Purpose: The purpose of this study was to prepare chimeric antihuman CD22 tetravalent monoclonal antibodies (MAbs) with high functional affinity, long persistence in the circulation, increased antitumor activity, and conserved effector function in vitro.
Experimental design: We investigated the association/dissociation rates of these tetravalent antibodies using CD22(+) Daudi lymphoma cells. We then tested their ability to interact with Fc receptors on a human cell line (U937), to mediate antibody-dependent cellular cytotoxicity with human natural killer cells, to bind human C1q, to inhibit the in vitro growth of CD22 Daudi cells, and to persist in the circulation.
Results: The rate of dissociation of the tetravalent MAbs versus the divalent antibody was considerably slower. These tetravalent MAbs inhibited the in vitro proliferation of CD22 Daudi cells at a concentration that was at least 100-fold lower than that of the divalent murine antibody. The tetravalent MAbs containing both the CH2 and CH3 domains and a chimeric recombinant divalent antibody bound similarly to Fc receptor, C1q, and mediate antibody-dependent cellular cytotoxicity equally well with human natural killer cells. The persistence in the circulation of chimeric tetravalent MAbs was considerably longer than that of chemical homodimers.
Conclusions: The tetravalent anti-CD22 MAbs with intact Fc regions should make effective therapeutic agents for B-cell tumors.