Used primarily as a potent proteasome inhibitor, this compound plays a key role in the treatment of multiple myeloma and other hematologic cancers. It functions by reversibly inhibiting the chymotrypsin-like activity of the 20S proteasome, disrupting protein degradation in cells and leading to apoptosis, particularly in cancer cells with high protein turnover. Due to its stereospecific structure, it exhibits enhanced selectivity and potency compared to earlier boronic acid-based inhibitors. It is administered intravenously and has shown efficacy in patients who are refractory to other therapies. Its application is mainly in clinical oncology, often as part of combination regimens involving dexamethasone or immunomodulatory drugs.