Delanzomib is an orally bioavailable inhibitor of chymotrypsin-like proteasome activity (IC50 = 3.8 nM in isolated human erythrocytes) that only marginally inhibits tryptic and peptidyl glutamyl proteasome activity. Delanzomib pre-treatment (20 nM) in vitro inhibits IκBα degradation, NF-κB activation, and the expression of NF-κB-regulated genes, including IκBα, XIAP, TNF-α, IL-1β, ICAM-1, and VEGF. Delanzomib induces apoptosis in multiple myeloma cell lines and inhibits proliferation in a panel of human hematologic and solid tumor cell lines (IC50s = 5.6-34.2 nM). It reduces tumor weight in an RPMI 8226 human multiple myeloma mouse xenograft model when administered intravenously at doses ranging from 1.5-4 mg/kg twice daily and leads to complete tumor regression at a chronic oral dose of 13 mg/kg. Delanzomib reduces the serum level of circulating cytokines, prevents renal tissue damage, and increases lifespan in a mouse model of fatal lupus nephritis.
