Immunoproteasome inhibitor 1 is a highly potent and reversible inhibitor of both immunoproteasome and proteasome activity. It exhibits time-independent inhibitory effects on immunoproteasome subunits β5c, β1i, and β5i, with respective Ki values of 1.18 μM, 0.27 μM, and 1.91 μM. This compound shows promising potential for the treatment of select neoplastic diseases [1].

Immunoproteasome inhibitor 1 (compound 9), used in concentrations ranging from 0 to 25 μM for durations of 0 to 600 seconds in Human 20S immunoproteasome and human 20S proteasome, exhibits a high binding affinity, particularly for the β1i subunit (0.27 μM). Additionally, it demonstrates effective inhibition of both β5i and β5c subunits. Notably, inhibition of the β5i subunit is characterized as reversible and independent of exposure time [1].