An antibody-drug conjugate (ADC) composed of a monoclonal antibody directed against B-cell antigen receptor complex-associated protein beta chain (CD79B) conjugated, via a protease-cleavable peptide linker, to monomethyl auristatin E (MMAE), an auristatin derivative and a potent microtubule inhibitor, with potential antineoplastic activity. Upon administration, polatuzumab vedotin selectively binds to CD79B, a protein which is abundantly expressed on the surface of B-cells. Upon internalization and proteolytic cleavage, MMAE binds to tubulin and inhibits its polymerization, resulting in G2/M phase arrest and tumor cell apoptosis. CD79B, a component of the B-cell receptor (BCR), plays a key role in B-cell receptor signaling and is expressed on the surface of almost all types of malignant B-cells.