LMP7/LMP2-IN-1 (Compound 19) is the orally active inhibitor for immunoproteasome subunits LMP7 and LMP2 with IC 50 of 257 and 10 nM. LMP7/LMP2-IN-1 reduces the generation of antibody, downregulates the cells in spleen germinal center B and in plasma in NP-OVA-immunized mice, and can be used in research about autoimmune diseases.