Definition

A bispecific antibody directed against both ectonucleotide pyrophosphatase/phosphodiesterase family member 3 (ENPP3, NPP3, B10, PDNP3 CD203c, or PD-IBETA) and the T-cell surface antigen CD3, with potential immunostimulatory and antineoplastic activities. Upon administration, anti-ENPP3/anti-CD3 bispecific antibody XmAb819 binds bivalently to ENPP3 expressed on tumor cells and monovalently to CD3 expressed on T-cells. The resulting cross-linkage may trigger a potent cytotoxic T-lymphocyte (CTL) response against ENPP3-expressing tumor cells. While normally expressed at low levels on tubules of the kidney cortex and by some cells in gastrointestinal, adrenal, and endometrial tissues, the type II transmembrane glycoprotein ENPP3 is overexpressed in various cancers including most renal neoplasms and some liver cancers. The bivalent binding to ENPP3 and monovalent binding to CD3 by XmAb819 may allow selective targeting of ENPP3-overexpressing tumor cells.