The Nedd8-activating enzyme inhibitor MLN4924 thwarts microenvironment-driven NF-κB activation and induces apoptosis in chronic lymphocytic leukemia B cells

Phase I Study of the Novel Investigational NEDD8-Activating Enzyme Inhibitor Pevonedistat (MLN4924) in Patients with Relapsed/Refractory Multiple Myeloma or Lymphoma

PURPOSE

Evaluate the safety, pharmacokinetic profile, pharmacodynamic effects, and antitumor activity of the first-in-class investigational NEDD8-activating enzyme (NAE) inhibitor pevonedistat (TAK-924/MLN4924) in patients with relapsed/refractory lymphoma or multiple myeloma.

EXPERIMENTAL DESIGN

Patients with relapsed/refractory myeloma (n = 17) or lymphoma (n = 27) received intravenous pevonedistat 25 to 147 mg/m(2) on days 1, 2, 8, 9 (schedule A; n = 27) or 100 to 261 mg/m(2) on days 1, 4, 8, 11 (schedule B; n = 17) of 21-day cycles.

RESULTS

Maximum tolerated doses were 110 mg/m(2) (schedule A) and 196 mg/m(2) (schedule B). Dose-limiting toxicities included febrile neutropenia, transaminase elevations, muscle cramps (schedule A), and thrombocytopenia (schedule B). Common adverse events included fatigue and nausea. Common grade ≥3 events were anemia (19%; schedule A), and neutropenia and pneumonia (12%; schedule B). Clinically significant myelosuppression was uncommon. There were no treatment-related deaths. Pevonedistat pharmacokinetics exhibited a biphasic disposition phase and approximate dose-proportional increases in systemic exposure. Consistent with the short mean elimination half-life of approximately 8.5 hours, little-to-no drug accumulation in plasma was seen after multiple dosing. Pharmacodynamic evidence of NAE inhibition included increased skin levels of CDT-1 and NRF-2 (substrates of NAE-dependent ubiquitin ligases), and increased NRF-2-regulated gene transcript levels in whole blood. Pevonedistat-NEDD8 adduct was detected in bone marrow aspirates, indicating pevonedistat target engagement in the bone marrow compartment. Three lymphoma patients had partial responses; 30 patients achieved stable disease.

CONCLUSIONS

Pevonedistat demonstrated anticipated pharmacodynamic effects in the clinical setting, a tolerable safety profile, and some preliminary evidence that may be suggestive of the potential for activity in relapsed/refractory lymphoma.

The NAE inhibitor pevonedistat (MLN4924) synergizes with TNF-α to activate apoptosis

Predicting and understanding the mechanism of drug-induced toxicity is one of the primary goals of drug development. It has been hypothesized that inflammation may have a synergistic role in this process. Cell-based models provide an easily manipulated system to investigate this type of drug toxicity. Several groups have attempted to reproduce in vivo toxicity with combination treatment of pharmacological agents and inflammatory cytokines. Through this approach, synergistic cytotoxicity between the investigational agent pevonedistat (MLN4924) and TNF-α was identified. Pevonedistat is an inhibitor of the NEDD8-activating enzyme (NAE). Inhibition of NAE prevents activation of cullin-RING ligases, which are critical for proteasome-mediated protein degradation. TNF-α is a cytokine that is involved in inflammatory responses and cell death, among other biological functions. Treatment of cultured cells with the combination of pevonedistat and TNF-α, but not as single agents, resulted in rapid cell death. This cell death was determined to be mediated by caspase-8. Interestingly, the combination treatment of pevonedistat and TNF-α also caused an accumulation of the p10 protease subunit of caspase-8 that was not observed with cytotoxic doses of TNF-α. Under conditions where apoptosis was blocked, the mechanism of death switched to necroptosis. Trimerized MLKL was verified as a biomarker of necroptotic cell death. The synergistic toxicity of pevonedistat and elevated TNF-α was also demonstrated by in vivo rat studies. Only the combination treatment resulted in elevated serum markers of liver damage and single-cell hepatocyte necrosis. Taken together, the results of this work have characterized a novel synergistic toxicity driven by pevonedistat and TNF-α.

Neddylation controls basal MKK7 kinase activity in breast cancer cells

The c-Jun NH2-terminal protein kinase (JNK) pathway has been implicated in mammary tumor development. However, the molecular mechanisms regulating JNK activity in breast cancer cells remain unclear. Here, we report that the inhibition of ubiquitination-like post-translational modification neddylation through different strategies results in enhanced basal JNK phosphorylation in human breast cancer cells. The upregulation of basal JNK phosphorylation upon neddylation inhibition is independent of the deneddylation of Cullins, the well-characterized neddylation substrates. Since augmented basal JNK phosphorylation via ectopic MKK7 expression impedes proliferation and the epithelial-to-mesenchymal transition (EMT) phenotype, the neddylation system might contribute to mammary tumor development partially through limiting basal JNK phosphorylation. Further exploration reveals that MKK7, a JNK-specific MAP2K, undergoes neddylation in human breast cancer cells. MKK7 co-precipitates with a fragment of Ran-binding protein 2 (RanBP2), a large multimodular and pleiotropic protein that has been recognized as a SUMO E3 ligase. Knockdown of RanBP2 attenuates MKK7 neddylation and augments basal JNK phosphorylation without affecting the neddylation of Cullins, whereas ectopic expression of a RanBP2 fragment possessing SUMO E3 activity (RanBP2ΔFG) manifests the opposite effects. In vitro neddylation assays confirm that RanBP2ΔFG works as the neddylation E3 ligase for MKK7. The basal kinase activity of endogenous MKK7 increases upon RanBP2 knockdown but decreases upon the ectopic expression of RanBP2ΔFG. Furthermore, purified MKK7 shows reduced basal kinase activity after in vitro neddylation by RanBP2ΔFG. Consistently, RanBP2 knockdown leads to reduced proliferation and impaired EMT phenotype in human breast cancer cells and the effects of RanBP2 knockdown are reversed by simultaneous MKK7 knockdown. Taken together, our data suggest that MKK7 undergoes neddylation in human breast cancer cells, which limits its basal kinase activity.

Vincristine activates c-Jun N-terminal kinase in chronic lymphocytic leukaemia in vivo

AIMS

The authors' aim was to conduct a proof-of-principle study to test whether c-Jun N-terminal kinase (JNK) phosphorylation and Noxa induction occur in peripheral blood chronic lymphocytic leukaemia (CLL) cells in patients receiving a vincristine infusion.

METHODS

Patients with CLL received 2 mg vincristine by a 5-min intravenous infusion. Blood samples were collected at baseline and up to 6 h after the vincristine infusion, and assayed for JNK activation, Noxa induction and vincristine plasma concentrations.

RESULTS

Ex vivo treated peripheral CLL cells activated JNK in response to 10-100 nM vincristine in 6 h. Noxa protein expression, while variable, was also observed over this time frame. In CLL patients, vincristine infusion led to rapid (<1 h) JNK phosphorylation in peripheral blood CLL cells which was sustained for at least 4-6 h after the vincristine infusion. Noxa protein expression was not observed in response to vincristine infusion.

CONCLUSIONS

This study confirmed that vincristine can activate JNK but not induce Noxa in CLL cells in vivo. The results suggest that novel JNK-dependent drug combinations with vincristine warrant further investigation.

The novel protective role of P27 in MLN4924-treated gastric cancer cells

The tumor-suppressor gene cyclin-dependent kinase inhibitor 1B (P27) is downregulated in gastric cancer cells mainly through proteolytic degradation mediated by the SKP-Cullin1-F-Box (SCF) complex. But the correlation between its downregulation and gastric cancer prognosis still remains indefinite. MLN4924, an anti-tumor agent, which suppresses the SCF complex by inhibiting Cullin1 neddylation, emerges as a promising tool to elucidate its functions in gastric cancer cells. In this study, MLN4924 induced significant growth inhibition of gastric cancer cells in a dose-dependent manner, along with the simultaneous accumulation of P27 and cell cycle abnormalities such as G2/M arrest. Importantly, we found that P27 silencing in MLN4924-treated cells resulted in an enhancement of growth inhibition both in vitro and in vivo. Mechanism analysis revealed the antagonism effects of antioxidants to this excess apoptosis, suggesting reactive oxygen species (ROS) overproduction especially in the mitochondria was the principal cause of the augmentation. Moreover, the robust ROS attacked the mitochondria to initiate collapse of the mitochondrial membrane permeability and the exportation of apoptosis-inducing factor (AIF), IAP-binding mitochondrial protein (SMAC/DIABLO) and cytochrome c. Finally, we also found that P27 knockdown affected the expression profile of several critical BH3 family members to amplify the mitochondrial dysfunction and apoptosis. In summary, our findings unveiled a protective role of P27 by maintaining mitochondrial membrane permeability in MLN4924-treated gastric cancer cells, and therefore highlighted the potential combination of MLN4924 with P27 inhibition to improve its therapeutic efficacy.

Targeting chronic lymphocytic leukemia cells in the tumor microenviroment: A review of the in vitro and clinical trials to date

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the western world. Despite significant advances in therapy over the last decade CLL remains incurable. Current front-line therapy often consists of chemoimmunotherapy-based regimens, most commonly the fludarabine, cyclophosphamide plus rituximab combination, but rates of relapse and refractory disease are high among these patients. Several key signaling pathways are now known to mediate the survival and proliferation of CLL cells in vivo, the most notable of which are the pathways mediated by the B-cell receptor (BCR) and cytokine receptors. A better understanding of the pathogenesis of the disease, the underlying biology of the CLL-cell and the roles of the tumour microenvironment has provided the rationale for trials of a range of novel, more targeted therapeutic agents. In particular, clinical trials of ibrutinib and idelalisib, which target the Brutons tyrosine kinase and the delta isoform of phosphoinositol-3 kinase components of the BCR signaling pathway respectively, have shown extremely promising results. Here we review the current literature on the key signaling pathways and interactions of CLL cells that mediate the survival and proliferation of the leukemic cells. For each we describe the results of the recent clinical trials and in vitro studies of novel therapeutic agents.

Targeting neddylation induces DNA damage and checkpoint activation and sensitizes chronic lymphocytic leukemia B cells to alkylating agents

Microenvironment-mediated upregulation of the B-cell receptor (BCR) and nuclear factor-κB (NF-κB) signaling in CLL cells resident in the lymph node and bone marrow promotes apoptosis evasion and clonal expansion. We recently reported that MLN4924 (pevonedistat), an investigational agent that inhibits the NEDD8-activating enzyme (NAE), abrogates stromal-mediated NF-κB pathway activity and CLL cell survival. However, the NAE pathway also assists degradation of multiple other substrates. MLN4924 has been shown to induce DNA damage and cell cycle arrest, but the importance of this mechanism in primary neoplastic B cells has not been studied. Here we mimicked the lymph node microenvironment using CD40 ligand (CD40L)-expressing stroma and interleukin-21 (IL-21) to find that inducing proliferation of the primary CLL cells conferred enhanced sensitivity to NAE inhibition. Treatment of the CD40-stimulated CLL cells with MLN4924 resulted in deregulation of Cdt1, a DNA replication licensing factor, and cell cycle inhibitors p21 and p27. This led to DNA damage, checkpoint activation and G2 arrest. Alkylating agents bendamustine and chlorambucil enhanced MLN4924-mediated DNA damage and apoptosis. These events were more prominent in cells stimulated with IL-21 compared with CD40L alone, indicating that, following NAE inhibition, the culture conditions were able to direct CLL cell fate from an NF-κB inhibition to a Cdt1 induction program. Our data provide insight into the biological consequences of targeting NAE in CLL and serves as further rationale for studying the clinical activity of MLN4924 in CLL, particularly in combination with alkylating agents.

MLN4924 sensitizes monocytes and maturing dendritic cells for TNF-dependent and -independent necroptosis

BACKGROUND AND PURPOSE

MLN4924 prevents the formation of active cullin-RING ubiquitin ligase complexes and thus inhibits NF-κB signalling. Here, we evaluated the effects of this compound on monocytes and dendritic cells (DCs).

EXPERIMENTAL APPROACH

Monocytes and DCs were challenged with TNF or LPS in the presence and absence of MLN4924. The effects of MLN4924 on cellular viability, pro-inflammatory gene induction and DC maturation were investigated using the MTT assay, elisa and FACS analysis. Mechanisms of cell death induction were evaluated by using inhibitors of caspases, RIPK1 and MLKL.

KEY RESULTS

MLN4924 inhibited NF-κB activation and sensitized monocytes and immature DCs (iDCs) for TNFR1-induced cell death. Neither the caspase inhibitor zVAD-fmk, the RIPK1 inhibitor necrostatin-1 (nec-1) nor the MLKL inhibitor necrosulfonamide (NSA) alone prevented TNF-induced cell death. A combination of zVAD-fmk and nec-1 or NSA, however, rescued monocytes and iDCs from MLN4924/TNF-induced cell death indicating that MLN4924 affects anti-apoptotic and anti-necrotic activities in TNFR1 signalling. MLN4924 also converted the response of iDCs to LPS from maturation to cell death. LPS-induced cell death in MLN4924-treated iDCs was again only effectively blocked by cotreatment with zVAD-fmk and nec-1 or NSA. Noteworthy, MLN4924/LPS-induced cell death was almost completely independent of endogenous TNF. MLN4924 also strongly inhibited maturation and activation of iDCs that were rescued from cell death by zVAD-fmk and nec-1.

CONCLUSIONS AND IMPLICATIONS

Our data reveal a strong dual suppressive effect of MLN4924 on DC activity. The targeting of NAE by MLN4924 could be a new way to treat inflammatory diseases.

A new hope: novel therapeutic approaches to treatment of chronic lymphocytic leukaemia with defects in TP53

Chronic lymphocytic leukaemia (CLL) is an indolent B-cell malignancy with heterogeneous outcomes. Chromosomal abnormalities in CLL are predictive of the natural disease course; del(11q) and del(17p) are recognized as high risk genetic lesions. Del(17p) is associated with an impaired function of TP53, a key tumour suppressor, and is particularly problematic. Such patients respond poorly to chemo-immunotherapy and have significantly shorter survival compared to patients with standard and low-risk cytogenetics. While TP53 pathway defects are rare at initial diagnosis, their frequency increases in relapsed CLL. Until very recently, this group of patients represented an unmet clinical need with few therapeutic options. However, the advent of targeted therapies has expanded the drug armamentarium and introduced new hope for these highly refractory patients. Agents that target B-cell receptor signalling, BH3-mimetics and others induce apoptosis of the neoplastic B-cells in a TP53-independent manner. Their use in the clinic is associated with remarkable activity in patients with del(17p). In this review we discuss the frequency and clinical significance of del(17p) and genetic mutations leading to disrupted TP53, the putative role of other TP53 homologues, and the results of key clinical trials involving both conventional chemotherapy and novel agents.