Definition

An antibody-drug conjugate (ADC) composed of XMT-1535, a humanized monoclonal antibody against human sodium-dependent phosphate transport protein 2B (SLC34A2; NaPi2b), that is site-specifically bioconjugated to the cytotoxic aurastatin derivative auristatin F-HPA (AF-HPA; auristatin F-hydroxypropylamide), with potential antineoplastic activity. Upon administration of anti-NaPi2b ADC XMT-1592, the antibody moiety targets and binds to NaPi2b expressed on tumor cells. Following internalization of XMT-1592 and release of AF-HPA, the AF-HPA binds to tubulin and inhibits microtubule polymerization, which results in G2/M phase arrest and apoptosis of NaPi2b-expressing tumor cells. NaPi2b, a tumor-associated antigen (TAA), is overexpressed on a variety of cancer cells and plays a key role in the transport of inorganic phosphate (Pi) and the maintenance of phosphate homeostasis.