Pevonedistat, a NEDD8-activating enzyme inhibitor, is active in mantle cell lymphoma and enhances rituximab activity in vivo.

Mantle cell lymphoma (MCL) is characterized by an aggressive clinical course and inevitable development of refractory disease, stressing the need to develop alternative therapeutic strategies. To this end, we evaluated pevonedistat (MLN4924), a novel potent and selective NEDD8-activating enzyme inhibitor in a panel of MCL cell lines, primary MCL tumor cells, and 2 distinct murine models of human MCL. Pevonedistat exposure resulted in a dose-, time-, and caspase-dependent cell death in the majority of the MCL cell lines and primary tumor cells tested. Of interest, in the MCL cell lines with lower half-maximal inhibitory concentration (0.1-0.5 µM), pevonedistat induced G1-phase cell cycle arrest, downregulation of Bcl-xL levels, decreased nuclear factor (NF)-κB activity, and apoptosis. In addition, pevonedistat exhibited additive/synergistic effects when combined with cytarabine, bendamustine, or rituximab. In vivo, as a single agent, pevonedistat prolonged the survival of 2 MCL-bearing mouse models when compared with controls. Pevonedistat in combination with rituximab led to improved survival compared with rituximab or pevonedistat monotherapy. Our data suggest that pevonedistat has significant activity in MCL preclinical models, possibly related to effects on NF-κB activity, Bcl-xL downregulation, and G1 cell cycle arrest. Our findings support further investigation of pevonedistat with or without rituximab in the treatment of MCL.

The novel proteasome inhibitor carfilzomib induces cell cycle arrest, apoptosis and potentiates the anti-tumour activity of chemotherapy in rituximab-resistant lymphoma.

Targeting the proteasome system with bortezomib (BTZ) results in anti-tumour activity and potentiates the effects of chemotherapy/biological agents in multiple myeloma and B-cell lymphoma. Carfilzomib (CFZ) is a more selective proteasome inhibitor that is structurally distinct from BTZ. In an attempt to characterize its biological activity, we evaluated CFZ in several lymphoma pre-clinical models. Rituximab-sensitive cell lines (RSCL), rituximab-resistant cell lines (RRCL), and primary tumour cells derived from B-cell lymphoma patients were exposed to CFZ or BTZ. Cell viability and changes in cell cycle were determined. Western blots were performed to detect PARP-cleavage and/or changes in Bcl-2 (BCL2) family members. CFZ was 10 times more active than BTZ and exhibited dose- and time-dependent cytotoxicity. CFZ exposure induced apoptosis by upregulation of Bak (BAK1) and subsequent PARP cleavage in RSCL and RRCL; it was also partially caspase-dependent. CFZ induced G2/M phase cell cycle arrest in RSCL. CFZ demonstrated the ability to overcome resistance to chemotherapy in RRCL and potentiated the anti-tumour activity of chemotherapy agents. Our data suggest that CFZ is able to overcome resistance to chemotherapeutic agents, upregulate pro-apoptotic proteins to promote apoptosis, and induce G2/M cell cycle arrest in lymphoma cells. Our pre-clinical data supports future clinical evaluation of CFZ in B-cell lymphoma.

MLN2238, a proteasome inhibitor, induces caspase-dependent cell death, cell cycle arrest, and potentiates the cytotoxic activity of chemotherapy agents in rituximab-chemotherapy-sensitive or rituximab-chemotherapy-resistant B-cell lymphoma preclinical models.

To further develop therapeutic strategies targeting the proteasome system, we studied the antitumor activity and mechanisms of action of MLN2238, a reversible proteasome inhibitor, in preclinical lymphoma models. Experiments were conducted in rituximab-chemotherapy-sensitive cell lines, rituximab-chemotherapy-resistant cell lines (RRCL), and primary B-cell lymphoma cells. Cells were exposed to MLN2238 or caspase-dependent inhibitors, and differences in cell viability, alterations in apoptotic protein levels, effects on cell cycle, and the possibility of synergy when combined with chemotherapeutic agents were evaluated. MLN2238 showed more potent dose-dependent and time-dependent cytotoxicity and inhibition of cell proliferation in lymphoma cells than bortezomib. Our data suggest that MLN2238 can induce caspase-independent cell death in RRCL. MLN2238 (and to a much lesser degree bortezomib) reduced RRCL S phase and induced cell cycle arrest in the G2/M phase. Exposure of rituximab-chemotherapy-sensitive cell lines and RRCL to MLN2238 potentiated the cytotoxic effects of gemcitabine, doxorubicin, and paclitaxel and overcame resistance to chemotherapy in RRCL. MLN2238 is a potent proteasome inhibitor active in rituximab-chemotherapy-sensitive and rituximab-chemotherapy-resistant cell models and potentiates the antitumor activity of chemotherapy agents and has the potential of becoming an effective therapeutic agent in the treatment of therapy-resistant B-cell lymphoma.