Delanzomib

CEP-18770 demonstrates marginal prevention of the tryptic and peptidyl gultamyl activities of the protesome.^[1] CEP-18770 inhibits A2780 ovarian cancer cells, PC3 prostate cancer, H460, LoVo colon cancer, RPMI8226 multiple myeloma cancer and HS-Sultan anaplastic non-Hodgkin lymphoma with IC50 values of 13.7, 22.2, 34.2 11.3, 5.6 and 8.2 nM, respectively.^[1] CEP-18770 blocks the ubiquitin-proteasome pathway in several MM and in the chronic myelogenous leukemia cell line, K562. CEP-18770 causes an accumulation of ubiquitinated proteins over 4 to 8 hours.^[1] IκBα degradation is completely blocked by pretreatment with CEP-18770. CEP-18770 significantly inhibits high levels of NF-κB activity in both RPMI-8226 and U266 cells. The time- and concentration-dependent suppression of NF-kB DNA-binding activity in MM cell lines by CEP-18770 leads to a decrease of expression of several NF-κB-modulated genes mediating the growth and survival of tumor cells including IkBα itself, the X-chromosome-linked inhibitor-of-apoptosis protein (XIAP), the pro-inflammatory cytokines TNF-α and interleukin-1β (IL-1β), the intracellular adhesion molecule (ICAM1), and the pro-angiogeneic factor vascular endothelial growth factor. ^[1] The expression of these NF-κB–mediated genes are associated with more favorable clinical responsiveness to this agent, highlighting their potential prognostic value in response to CEP-18770 exposure. ^[1] The proapoptotic activity of CEP-18770 against MM is not limited solely to tumor-derived MM cell lines, but extends to primary MM explants from relapsed or refractory patients. ^[1] In addition, CEP-18770 in combination produces synergistic inhibition of MM cell viability in vitro.^[2]

HMEC and TEC cells are seeded into 24-well plates at a density of 10⁴ cells/well in DMEM supplemented with 5% FCS. After incubation with proteasome inhibitors (48 hours), cells are washed, air dried, and stained with crystal violet as described. Cell number is determined, in duplicate samples, on the basis of a standard curve obtained with known cell numbers. All experiments are performed in triplicate. In vitro formation of capillary-like structures is studied on cells (4 × 10⁴ cells/well in DMEM supplemented with 5% FCS. After incubation with proteasome inhibitors (48 hours), cells are washed (cells/well in 24-well plates) and seeded onto Matrigel-coated wells in DMEM containing 0.25% BSA. HMEC and TEC cells (5 × 10³ per well), suspended in 200 μL DMEM with 5% FCS (positive control), serum-free medium (negative control), are layered onto the Matrigel surface in the presence or absence of proteasome inhibitor CEP-18770. Cells are observed with a microscope and experimental results are then recorded after a 6-hour incubation at 37 °C. Data is analyzed, as the mean (× 1 SD) of total length of capillary-like structures, by the Micro-Image system and is expressed as mm/field by the computer analysis system in 5 different fields at 100 × magnification in duplicated wells for 4 different experiments.

CEP-18770 reveals sustained dose-related relative tumor weight inhibition. CEP-18770 leads to dose-related complete tumor regressions, which results in a 50% incidence of CR at its maximally tolerated dose (MTD) of 1.2 mg/kg intravenously. ^[1] CEP-18770 reveals dose-related increase in the incidence of tumor-free mice by the completion of these studies (120 days after tumor transplantation). Oral administration of CEP-18770 produces a marked decrease in tumor weight and notable dose-related incidence of complete tumor regression with minimal changes in animal body weight over the course of the 120 day studies. ^[1]_Equiactive doses of CEP-18770 reveal a greater and more sustained dose-related inhibition of tumor proteasome activity, corresponding temporarily with maximum induction of caspase-3 and 7 activity.^[1] The maximum apoptotic signal is 2.5 fold greater for CEP-18770. In contrast, proteasome inhibition profiles of CEP-18870 are comparable in the normal peripheral mouse tissues examined (liver, lungs, whole blood, and brain [no activity]) in both their magnitude and their duration.^[1] No proteasome inhibition is detected in brain tissue at any time point for either CEP-18770 or. ^[1] Single agent CEP-18770 PO also shows marked anti-MM effects in these xenograft models^[1]