Full-length IgG antibodies that specifically bind to a target molecule with high affinity have been extensively developed as research tools, as well as for diagnostic and therapeutic purposes. However, their targets are primarily the proteins expressed on the cell-surface and some secreted proteins because antibodies normally cannot cross intact cellular or subcellular membranes in living cells due to their large size and hydrophilicity. 

 We have developed the cytosol-penetrating antibody, a so called cytotransmab, which in the intact human IgG1 format can access the cytosol of living cells after receptor-mediated endocytosis. The ability of cytotransmab to directly access cytosolic proteins after physiological endocytosis makes it an ideal candidate for construction of next-generation therapeutic antibodies that directly target cytosolic proteins that are associated with many human diseases, including tumors. Cytotransmab technology has the potential to generate full-length IgG-format antibodies for detection of cytosolic proteins as research and diagnostic agents, as well as inhibition of cytosolic protein-protein interactions as therapeutic agents.