Chemical. CAS 437742-34-2. Formula C15H20ClNO4. MW 313.8. Isolated from Salinospora tropica. Potent, irreversible inhibitor of all the 3 proteolytic activities of the mammalian 20S proteasome. beta5 subunit chymotrypsin-like EC50 = 3.5nM beta2 subunit trypsin-like EC50 = 28nM beta1 subunit caspase-like or peptidyl-glutamyl peptide-hydrolyzing PGPH EC50 = 430nM Potent anticancer compound. Triggers apoptosis, with distinct proteasome activity and mechanism of action compared to bortezomib Velcade Prod. No. AG-CR1-3602. Most potent suppressor of NF-kappaB activation, compared with bortezomib, MG-132 Prod. No. AG-CP3-0011, N-acetyl-leucyl-leucyl-norleucinal ALLN and lactacystin Prod. No. AG-CN2-0104. Inhibitor of TNF-alpha, IL-1, IL-6, ICAM-1 and VEGF synthesis. Displays a longer inhibition duration than bortezomib. Potent antileukemic activity against bortezomib-resistant leukemia cells.