In vitro activity: The anti-MM activity of Oprozomib is associated with activation of caspase-8, caspase-9, caspase-3, and PARP, as well as inhibition of migration of MM cells and angiogenesis.

Kinase Assay: Samples (lysed cells or tissue homogenates) are treated for 1 h at room temperature with the biotinylated active site probe PR-584 (5-15 μM). Samples are denatured by addition of SDS (0.9% final) and heating to 100 °C for 5 min. The denatured samples are transferred to a 96-well or 384-well filter plat, mixed with streptavidin-sepharose beads (2.5-5 μL packed beads/well), and incubated for 1 h at room temperature on a plate shaker. The beads are washed 5 times with 100-200 μL /well of ELISA buffer (PBS, 1% bovine serum albumin, 0.1% Tween-20) by vacuum filtration. The beads are incubated overnight at 4 °C on a plate shaker with the following antibodies recognizing the six catalytic subunits diluted into ELISA buffer: β5, β1, and β2 diluted 1:3000, LMP7 and LMP2 diluted 1:5000, and MECL-1 diluted 1:1000. The beads are washed 5 times with 100-200 μL /well of ELISA buffer and incubated with HRP-conjugated secondary antibody diluted 1:5000 in ELISA buffer and incubated 2 h at room temperature on a plate shaker. The beads are washed 5 times with 100-200 μL /well of ELISA buffer and developed for chemiluminsecence signal using the supersignal ELISA pico substrate following the manufacturer's instructions. Luminescence is measured on a plate reader and converted to ng of proteasome or μg/ml of lysate by comparison with 20S proteasome or untreated cell lysate standard curves. For proteasome inhibitor studies, active site probe binding values are expressed as the percent of binding relative to DMSO treated cells.

Cell Assay:In trypan blue exclusion assays, ONX 0912 exhibited IC50 values ranging from 58.9 to185.7 nmol/L in 8 different HNSCC cell lines. In the 4 HNSCC cell lines (UMSCC-1, UMSCC-22B, 1483, and UMSCC-1) examined, treatment ONX 0912 resulted in processing of caspase-3 to active subunits and cleavage of the caspase substrate PARP.

J Med Chem. 2009 May 14;52(9):3028-38; Blood. 2010 Dec 2;116(23):4906-15.