Zetomipzomib maleate (KZR-616), a novel immunoproteasome inhibitor, effectively and selectively inhibits the LMP7 subunit (hLMP7/mLMP7 IC50: 39/57 nM) and LMP2 subunit (hLMP7/mLMP7 IC50: 131/179 nM) of the immunoproteasome. This compound shows promising potential for research in various autoimmune diseases.