Lifastuzumab (also known as RG-7599 or DNIB0600A) is an investigational antibody-drug conjugate (ADC) developed by Genentech/Roche. It consists of a humanized monoclonal antibody targeting sodium-dependent phosphate transporter NaPi2b (SLC34A2), linked to a potent cytotoxic payload, monomethyl auristatin E (MMAE), via a protease-cleavable linker. Upon binding to NaPi2b on the surface of tumor cells, the ADC is internalized, and the linker is cleaved within lysosomes to release the microtubule-disrupting MMAE, leading to cell cycle arrest and apoptosis. It has been clinically evaluated primarily for the treatment of NaPi2b-expressing ovarian cancer and non-small cell lung cancer (NSCLC).