anti-FcRH5 antibody-drug conjugate DFRF4539A

An antibody-drug conjugate (ADC) composed of a humanized immunoglobulin G1 (IgG1) monoclonal antibody directed against the tumor-associated antigen (TAA) Fc receptor-like protein 5 (FcRH5; CD307; FCRL5; IRTA2; BXMAS1) and conjugated to monomethyl auristatin E (MMAE), an auristatin derivative and a potent microtubule inhibitor, via the protease-labile linker maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl (MC-VC-PABC), with potential antineoplastic activity. Upon administration, the monoclonal antibody moiety of anti-FcRH5 ADC DFRF4539A selectively binds to FcRH5 expressed on the surface of myeloma cells. Upon internalization and proteolytic cleavage, MMAE binds to tubulin and inhibits its polymerization, which results in G2/M phase arrest and tumor cell apoptosis. FcRH5, an immune receptor translocation-associated protein/Fc receptor homolog (IRTA/FCRH) family member and a B-cell lineage marker, is overexpressed on myeloma cells.