Anti-Human NaPi2b/SLC34A2 Monoclonal Antibody (Upifitamab)

NaPi2b (also known as SLC34A2) is a sodium-dependent phosphate transporter belonging to the solute carrier family SLC34. Its primary function is to maintain systemic phosphate homeostasis by cotransporting three sodium ions and one divalent phosphate ion into cells, and it plays a key role in absorbing dietary phosphate in intestinal epithelial cells. Structurally, it is a classic multi-spanning transmembrane protein with up to 12 transmembrane domains, with both its N-terminus and C-terminus facing the cytoplasm. It also features a large extracellular loop rich in glycosylation sites and cysteine residues; the specific sequence within this loop forms the well-known MX35 epitope, which serves as the structural basis for its role as a drug target. Dysfunction of this protein is associated with various diseases: mutations in its encoding gene SLC34A2 are the direct cause of the rare genetic disorder pulmonary alveolar microlithiasis, while NaPi2b is also specifically overexpressed in various solid tumors such as ovarian cancer, non-small cell lung cancer, and breast cancer, with limited expression in normal tissues. As a result, it has emerged as a highly promising research hotspot in the field of tumor-targeted therapy, particularly for the development of antibody-drug conjugates (ADCs).