Definition

An immunotoxin (IT) combination composed of two antibody-drug conjugates (ADCs), one containing a monoclonal antibody against CD3 and one against the CD7 antigen on activated T cells and natural killer (NK) cells, and both conjugated to ricin toxin A (RTA), the A-chain form of the potent plant toxin ricin, that can potentially be used to destroy activated T and NK cells. Upon administration of the anti-CD3/CD7-RTA immunotoxin, the anti-CD3 antibody moiety targets and binds to activated T-cells; the anti-CD7 antibody moiety targets and binds to CD7 on activated T cells and NK cells. Upon internalization and cleavage, the RTA moiety irreversibly inhibits protein synthesis and induces apoptosis in the activated T cells. This may eliminate activated T cells and may improve conditions such as graft-versus-host-disease (GvHD). In addition, the binding and blocking of the anti-CD3 antibody to the T-cell receptor/CD3 complex (TCR/CD3) results in activation-induced cell death (AICD) and immunosuppression.