The generation of immunotoxins using chimeric anti-CD22 antibodies containing mutations which alter their serum half-life

Murine and chimeric RFB4 (anti-human CD22) monoclonal antibodies (MAbs) with mutations in their Fc portions were conjugated to recombinant ricin toxin A chain to generate immunotoxins. The resulting immunotoxins (ITs) constructed with chimeric RFB4 MAbs were designed to have longer or shorter half-lives but similar binding and cytotoxic properties. These ITs can now be evaluated in vivo for improved therapeutic indices. The characteristics of these ITs are the subject of this report.