Synergistic anti-myeloma activity of the proteasome inhibitor marizomib and the IMiD immunomodulatory drug pomalidomide

LY103, a pomalidomide derivative, alleviates taxol resistance in NSCLC via energy metabolism crosstalk and tumor microenvironment intervention

In this study, we identified HIF 1α as a potential target for reversing taxol resistance in lung cancer by combining bioinformatics analysis with pharmacological analysis. Furthermore, pomalidomide derivative LY103 was also be synthesized by introducing an isatin analogue into the amino terminal ofpomalidomide, and it has a broad antitumor spectrum and showed excellent activity against A549/Taxol cells (IC50 = 6.33 ± 0.51 μM). The results of molecular docking showed that not only LY103 was inclined to bind to HIF 1α stably, it could also form multiple hydrogen bonds with VAL376, ASP256, ILE454, and GLU455 of HIF 1α even was reduced to LY103-NH2 by nitroreductase, which was further stabilized the complex formed by them, thereby inhibiting the activity of HIF 1α. LY103 was able to significantly induce DNA damage and inhibit angiogenesis. Concurrently, LY103 activated the immune response, reduced the expression of cytokines TNF-α, IL-6, and IL-1β, thus might be inhibit the proliferation and metastasis of tumor cells. Pharmacological analysis proved that LY103 led to cell apoptosis through the mitochondrial pathway, and its combination with taxol significantly promoted this process. In general, the consumption of glutathione, the crosstalk of energy metabolism, and the improvement of the tumor microenvironment caused by LY103 eventually led to the decrease of ABCC1 protein expression and the drug resistance was reversed. The rational design of LY103 provided a basis for the application of nitro compounds in the treatment of hypoxic tumors and the reversal of taxol resistance.

Evidence-based mechanisms of synergy with IMiD agent-based combinations in multiple myeloma

Treatment of multiple myeloma (MM) has seen great advances in recent years, and a key contributor to this change has been the effective use of combination therapies, which have improved both the depth and duration of patient responses. IMiD agents (lenalidomide and pomalidomide) have both tumoricidal and immunostimulatory functions, and due to their multiple mechanisms of action have become the backbone of numerous combination treatments in the newly diagnosed and relapsed/refractory settings. Although IMiD agent-based combination regimens provide improved clinical outcomes for patients with MM, the mechanisms underpinning these combinations are not well understood. In this review we describe the potential mechanisms of synergy leading to the enhanced activity observed when IMiD agents and other drug classes are used in combination through interrogation of the current knowledge surrounding their mechanism of actions.

Recent Advances in the Applications of Small Molecules in the Treatment of Multiple Myeloma

Therapy for multiple myeloma (MM), a hematologic neoplasm of plasma cells, has undergone remarkable changes over the past 25 years. Small molecules (molecular weight of less than one kDa), together with newer immunotherapies that include monoclonal antibodies, antibody-drug conjugates, and most recently, chimeric antigen receptor (CAR) T-cells, have combined to double the disease's five-year survival rate to over 50% during the past few decades. Despite these advances, the disease is still considered incurable, and its treatment continues to pose substantial challenges, since therapeutic refractoriness and patient relapse are exceedingly common. This review focuses on the current pipeline, along with the contemporary roles and future prospects for small molecules in MM therapy. While small molecules offer prospective benefits in terms of oral bioavailability, cellular penetration, simplicity of preparation, and improved cost-benefit considerations, they also pose problems of toxicity due to off-target effects. Highlighted in the discussion are recent developments in the applications of alkylating agents, immunomodulators, proteasome inhibitors, apoptosis inducers, kinesin spindle protein inhibitors, blockers of nuclear transport, and drugs that affect various kinases involved in intracellular signaling pathways. Molecular and cellular targets are described for each class of agents in relation to their roles as drivers of MM.

Design, synthesis, and biological evaluation of a novel series of 2-(2,6-dioxopiperidin-3-yl)isoquinoline-1,3(2H,4H)-dione derivatives as cereblon modulators

In the current study, we designed and synthesised a novel series of 2-(2,6-dioxopiperidin-3-yl)isoquinoline-1,3(2H,4H)-dione derivatives as cereblon (CRBN) modulators. The results of the CCK8 assay revealed potent antiproliferative activity for the selected compound 10a against NCI-H929 (IC₅₀=2.25 µM) and U239 (IC₅₀=5.86 µM) cell lines. Compound 10a also can inhibit the TNF-α level (IC₅₀=0.76 µM) in LPS stimulated PMBC and showed nearly no toxicity to this normal human cell line. The TR-FRET assay showed compound 10a having potent inhibitory activity against CRBN (IC₅₀=4.83 µM), and the docking study confirmed a nice fitting of 10a into the active sites of CRBN. Further biology studies revealed compound 10a can increase the apoptotic events, arrest the NCI-H929 cells at G0/G1 cell cycle, and induce the ubiquitination degradation of IKZF1 and IKZF3 proteins by CRL4^CRBN. These preliminary results suggested that compound 10a could serve as a potential antitumor drug and worthy of further investigation.

Single-Cell Proteomics and Tumor RNAseq Identify Novel Pathways Associated With Clofazimine Sensitivity in PI- and IMiD- Resistant Myeloma, and Putative Stem-Like Cells

Multiple myeloma (MM) is an incurable plasma cell malignancy with dose-limiting toxicities and inter-individual variation in response/resistance to the standard-of-care/primary drugs, proteasome inhibitors (PIs), and immunomodulatory derivatives (IMiDs). Although newer therapeutic options are potentially highly efficacious, their costs outweigh the effectiveness. Previously, we have established that clofazimine (CLF) activates peroxisome proliferator-activated receptor-γ, synergizes with primary therapies, and targets cancer stem-like cells (CSCs) in drug-resistant chronic myeloid leukemia (CML) patients. In this study, we used a panel of human myeloma cell lines as in vitro model systems representing drug-sensitive, innate/refractory, and clonally-derived acquired/relapsed PI- and cereblon (CRBN)-negative IMiD-resistant myeloma and bone marrow-derived CD138+ primary myeloma cells obtained from patients as ex vivo models to demonstrate that CLF shows significant cytotoxicity against drug-resistant myeloma as single-agent and in combination with PIs and IMiDs. Next, using genome-wide transcriptome analysis (RNA-sequencing), single-cell proteomics (CyTOF; Cytometry by time-of-flight), and ingenuity pathway analysis (IPA), we identified novel pathways associated with CLF efficacy, including induction of ER stress, autophagy, mitochondrial dysfunction, oxidative phosphorylation, enhancement of downstream cascade of p65-NFkB-IRF4-Myc downregulation, and ROS-dependent apoptotic cell death in myeloma. Further, we also showed that CLF is effective in killing rare refractory subclones like side populations that have been referred to as myeloma stem-like cells. Since CLF is an FDA-approved drug and also on WHO's list of safe and effective essential medicines, it has strong potential to be rapidly re-purposed as a safe and cost-effective anti-myeloma drug.

Carfilzomib-induced thrombotic microangiopathy is underestimated in clinical practice: A report of five patients and literature review

Carfilzomib (Cfz) is widely used to treat multiple myeloma. However, real-world data of the incidence of thrombotic microangiopathy (TMA) caused by Cfz is inconsistent (<1-5%). We evaluated 96 consecutive patients who received Cfz to evaluate the incidence of TMA in clinical practice. TMA developed in five patients (5.2%) who were mainly receiving high-dose Cfz (≥56 mg/m²). Based on a literature review, precaution should be taken for Cfz-induced TMA in male patients receiving high-dose Cfz irrespective of the combination therapy, Cfz administration period, and complement level. In conclusion, Cfz-induced TMA might be underestimated in clinical practice, and early intervention should be considered.

Caspase-8: Friend or Foe in Bortezomib/Lenalidomide-Based Therapy for Myeloma

Antiproliferation and proapoptosis are two major molecular mechanisms of action of drugs used for the treatment of multiple myeloma. Proteasome inhibitors, such as bortezomib (PS-341), and immunomodulatory drugs (IMiDs), such as lenalidomide, are the two drug types approved for the treatment of myeloma. Bortezomib and lenalidomide activate caspase-8 and promote the apoptosis of myeloma cells. However, caspase-8 inhibition potentiated the antiproliferative effect of lenalidomide and bortezomib in myeloma cells, suggesting that caspase-8 could regulate proliferation and apoptosis in the opposite pathway. In this mini-review, I summarized recent advances in determining the molecular mechanisms of caspase-8 in bortezomib–lenalidomide-based therapy for myeloma and explored the possible functions of caspase-8 in the proliferation and apoptosis of myeloma cells. Furthermore, future directions of caspase-8-based therapy for myeloma have been discussed.

Emerging and current treatment combinations for transplant-ineligible multiple myeloma patients

INTRODUCTION

Availability of new classes of novel agents has led to a radical switch in treatment paradigms for newly diagnosed transplant-ineligible multiple myeloma (NDTIMM) patients, providing an opportunity to significantly enhance the depth of response and extend survival outcomes.

AREAS COVERED

Treatment regimens including proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs) and/or monoclonal antibodies (mAbs), have achieved recent regulatory approval for NDTIMM, while novel combinations and newer agents are currently being explored. This review discusses the current landscape and possible treatment development of NDTIMM.

EXPERT OPINION

Bortezomib-lenalidomide-dexamethasone (VRd), daratumumab-bortezomib-melphalan-prednisone (DaraVMP) and daratumumab-lenalidomide-dexamethasone (DaraRd) represent new standard of care (SOC) treatments for NDTIMM patients, based on phase III trials showing their superior efficacy as compared with previous SOCs. The possibility of improving results by incorporating second generation PIs or using quadruple regimens has also been explored and different trials are still ongoing. Newer agents and innovative immunotherapies targeting B-cell maturation antigen have the potential to change the therapeutic landscape in coming years. Personalized approaches based on frailty-adapted, risk-based and minimal residual disease driven paradigms are under investigation.

Pomalidomide, bortezomib, and dexamethasone at first relapse in lenalidomide-pretreated myeloma: A subanalysis of OPTIMISMM by clinical characteristics

Objective

We evaluated the efficacy and safety of pomalidomide, bortezomib, and dexamethasone (PVd) vs bortezomib and dexamethasone (Vd) by age, renal function, and high‐risk cytogenetic abnormalities in lenalidomide‐pretreated patients with multiple myeloma at first relapse.

Methods

OPTIMISMM was a phase 3, multicenter, open‐label, randomized study (NCT01734928; N = 559). The primary endpoint was progression‐free survival (PFS).

Results

Overall, 226 patients had received one prior line of therapy. PVd significantly prolonged PFS vs Vd in patients aged ≤65 years (median, 22.0 vs 13.1 months; P = .0258) and >65 years (median, 17.6 vs 9.9 months; P = .0369). Median PFS in patients with renal impairment (RI; creatinine clearance <60 mL/min) was 15.1 months with PVd vs 9.5 months with Vd (hazard ratio [HR], 0.67 [95% CI, 0.34‐1.34]). In patients without RI, median PFS was 22.0 vs 13.1 months (HR, 0.45 [95% CI, 0.27‐0.76]). In patients with high‐risk cytogenetics, median PFS was 14.7 vs 9.9 months (HR, 0.39 [95% CI, 0.13‐1.17]). PVd significantly improved overall response rate vs Vd in all subgroups. The safety profile of PVd was consistent with previous reports.

Conclusions

These findings confirmed the benefits of PVd at first relapse, including in patients with poor prognostic factors.

Marine Power on Cancer: Drugs, Lead Compounds, and Mechanisms

Worldwide, 19.3 million new cancer cases and almost 10.0 million cancer deaths occur each year. Recently, much attention has been paid to the ocean, the largest biosphere of the earth that harbors a great many different organisms and natural products, to identify novel drugs and drug candidates to fight against malignant neoplasms. The marine compounds show potent anticancer activity in vitro and in vivo, and relatively few drugs have been approved by the U.S. Food and Drug Administration for the treatment of metastatic malignant lymphoma, breast cancer, or Hodgkin's disease. This review provides a summary of the anticancer effects and mechanisms of action of selected marine compounds, including cytarabine, eribulin, marizomib, plitidepsin, trabectedin, zalypsis, adcetris, and OKI-179. The future development of anticancer marine drugs requires innovative biochemical biology approaches and introduction of novel therapeutic targets, as well as efficient isolation and synthesis of marine-derived natural compounds and derivatives.

Treatment and outcome of newly diagnosed multiple myeloma patients > 75 years old: a retrospective analysis

This is a retrospective study of patients with multiple myeloma (MM) who were >75 years old. We identified 394 patients and for non-trial patients (n = 350), immunomodulatory drug (IMiD)+dex (32%) was the most commonly used regimen followed by alkylator with steroids or other therapy (21%), alkylator + proteasome inhibitor (PI)+steroid (18%), and IMiD + PI + dex (13%). Overall, achieving ≥ very good partial response was more in patients receiving a triplet compared to other therapies (46% vs. 21%, p < 0.0001). Also, the median overall survival (OS) was significantly longer in patients who were treated with a triplet (median OS: 50.2 vs. 32.8 months, p = 0.0006). In a multivariate for OS, receiving a triplet (HR: 0.65, p = 0.02), not having an R-ISS stage 3 (HR: 0.36, p = 0.0003), and bone marrow plasma cell percentage <60% (HR: 0.69, p = 0.03) were predictive. In conclusion, being able to receive triplet therapy was associated with better survival in our MM patients >75 years old.

Cancer therapies based on targeted protein degradation - lessons learned with lenalidomide

For decades, anticancer targeted therapies have been designed to inhibit kinases or other enzyme classes and have profoundly benefited many patients. However, novel approaches are required to target transcription factors, scaffolding proteins and other proteins central to cancer biology that typically lack catalytic activity and have remained mostly recalcitrant to drug development. The selective degradation of target proteins is an attractive approach to expand the druggable proteome, and the selective oestrogen receptor degrader fulvestrant served as an early example of this concept. Following a long and tragic history in the clinic, the immunomodulatory imide drug (IMiD) thalidomide was discovered to exert its therapeutic activity via a novel and unexpected mechanism of action: targeting proteins to an E3 ubiquitin ligase for subsequent proteasomal degradation. This discovery has paralleled and directly catalysed myriad breakthroughs in drug development, leading to the rapid maturation of generalizable chemical platforms for the targeted degradation of previously undruggable proteins. Decades of clinical experience have established front-line roles for thalidomide analogues, including lenalidomide and pomalidomide, in the treatment of haematological malignancies. With a new generation of 'degrader' drugs currently in development, this experience provides crucial insights into class-wide features of degraders, including a unique pharmacology, mechanisms of resistance and emerging therapeutic opportunities. Herein, we review these past experiences and discuss their application in the clinical development of novel degrader therapies.

Development of Marine-Derived Compounds for Cancer Therapy

Cancer has always been a threat to human health with its high morbidity and mortality rates. Traditional therapy, including surgery, chemotherapy and radiotherapy, plays a key role in cancer treatment. However, it is not able to prevent tumor recurrence, drug resistance and treatment side effects, which makes it a very attractive challenge to search for new effective and specific anticancer drugs. Nature is a valuable source of multiple pharmaceuticals, and most of the anticancer drugs are natural products or derived from them. Marine-derived compounds, such as nucleotides, proteins, peptides and amides, have also shed light on cancer therapy, and they are receiving a fast-growing interest due to their bioactive properties. Their mechanisms contain anti-angiogenic, anti-proliferative and anti-metastasis activities; cell cycle arrest; and induction of apoptosis. This review provides an overview on the development of marine-derived compounds with anticancer properties, both their applications and mechanisms, and discovered technologies.

Facts and Hopes in Multiple Myeloma Immunotherapy

Among the hallmarks of cancer is the ability of neoplastic cells to evade and suppress immune surveillance to allow their growth and evolution. Nowhere is this as apparent as in multiple myeloma, a cancer of antibody-producing plasma cells, where a complex interplay between neoplastic cells and the immune microenvironment is required for the development and progression of disease. Decades of research has led to the discovery of a number of therapeutic agents, from cytotoxic drugs to genetically engineered cells that mediate their antimyeloma effects at least partially through altering these immune interactions. In this review, we discuss the history of immunotherapy and current practices in multiple myeloma, as well as the advances that promise to one day offer a cure for this deadly disease.

New regimens and directions in the management of newly diagnosed multiple myeloma

The introduction of novel agents over the last decade has rapidly expanded the therapeutic landscape of multiple myeloma (MM) for both transplant-eligible and transplant-ineligible patients. The assessment of minimal residual disease (MRD) by next-generation flow cytometry or next-generation sequencing is established as a powerful predictor of long-term outcomes. The use of MRD in response-adapted clinical trials may provide opportunities to identify candidates for treatment escalation and de-escalation. Agents with proven activity in the relapsed and refractory setting are being studied in the management of high-risk newly diagnosed MM (NDMM). Here, we summarize the most recent clinical trials that have led to the current paradigms in the management of NDMM. We also discuss how novel agents could be incorporated in the newly diagnosed setting and potential clinical trial designs that could leverage MRD information with the goal of treatment optimization.

Caspase-8 Inhibition Prevents the Cleavage and Degradation of E3 Ligase Substrate Receptor Cereblon and Potentiates Its Biological Function

Cereblon (CRBN), a substrate receptor of cullin 4-RING E3 ligase (CRL4), mediates the ubiquitination and degradation of constitutive substrates and immunomodulatory drug-induced neo-substrates including MEIS2, c-Jun, CLC1, IKZF1/3, CK1α, and SALL4. It has been reported that CRBN itself could be degraded through the ubiquitin-proteasome system by its associated or other cullin-RING E3 ligases, thus influencing its biological functions. However, it is unknown whether the CRBN stability and its biological function could be modulated by caspases. In this study, using model cell lines, we found that activation of the death receptor using tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) leads to the decreased CRBN protein level. Through pharmacological inhibition and activation of caspase-8 (CASP-8), we disclosed that CASP-8 regulates CRBN cleavage in cell lines. Site mapping experiments revealed that CRBN is cleaved after Asp9 upon CASP-8 activation, resulting in the reduced stability. Using myeloma as a model system, we further revealed that either inhibition or genetic depletion of CASP-8 enhances the anti-myeloma activity of lenalidomide (Len) by impairing CRBN cleavage, leading to the attenuated IKZF1 and IKZF3 protein levels and the reduced viability of myeloma cell lines and primary myeloma cells from patients. The present study discovered that the stability of the substrate receptor of an E3 ligase can be modulated by CASP-8 and suggested that administration of CASP-8 inhibitors enhances the overall effectiveness of Len-based combination therapy in myeloma.

Pomalidomide, bortezomib, and dexamethasone for multiple myeloma previously treated with lenalidomide (OPTIMISMM): outcomes by prior treatment at first relapse

In the phase 3 OPTIMISMM trial, pomalidomide, bortezomib, and dexamethasone (PVd) demonstrated superior efficacy vs bortezomib and dexamethasone (Vd) in patients with relapsed or refractory multiple myeloma previously treated with lenalidomide, including those refractory to lenalidomide. This analysis evaluated outcomes in patients at first relapse (N = 226) by lenalidomide-refractory status, prior bortezomib exposure, and prior stem cell transplant (SCT). Second-line PVd significantly improved PFS vs Vd in lenalidomide-refractory (17.8 vs 9.5 months; P = 0.0276) and lenalidomide-nonrefractory patients (22.0 vs 12.0 months; P = 0.0491), patients with prior bortezomib (17.8 vs 12.0 months; P = 0.0068), and patients with (22.0 vs 13.8 months; P = 0.0241) or without (16.5 vs 9.5 months; P = 0.0454) prior SCT. In patients without prior bortezomib, median PFS was 20.7 vs 9.5 months (P = 0.1055). Significant improvement in overall response rate was also observed with PVd vs Vd in lenalidomide-refractory (85.9% vs 50.8%; P < 0.001) and lenalidomide-nonrefractory (95.7% vs 60.0%; P < 0.001) patients, with similar results regardless of prior bortezomib or SCT. No new safety signals were observed. These data demonstrate the benefit of PVd at first relapse, including immediately after upfront lenalidomide treatment failure and other common first-line treatments.

The proteasome as a druggable target with multiple therapeutic potentialities: Cutting and non-cutting edges

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.

Carfilzomib with immunomodulatory drugs for the treatment of newly diagnosed multiple myeloma

Carfilzomib, a selective proteasome inhibitor (PI), is approved for the treatment of patients with relapsed or refractory multiple myeloma (MM). Combination regimens incorporating a PI and immunomodulatory drug (IMiD) have been associated with deep responses and extended survival in patients with newly diagnosed MM (NDMM). Carfilzomib-based combinations with immunomodulators are being extensively studied in the frontline setting. The objective of this review was to describe efficacy and safety data for carfilzomib-based, PI/immunomodulatory combinations in NDMM. Information sources were articles indexed in PubMed and abstracts from key hematology/oncology congresses published between January 2012 and December 2018. PubMed and congresses were searched for prospective clinical studies assessing the combination of carfilzomib with an IMiD for NDMM treatment. Retrospective and preclinical reports, case reports/series, reviews, and clinical studies not evaluating carfilzomib-immunomodulator combinations in NDMM were excluded based on review of titles and abstracts. A total of nine articles and 72 abstracts were deemed relevant and included in the review. A total of six distinct carfilzomib-based, PI/immunomodulator combination regimens have been evaluated in 12 clinical trials. Overall, treatment with these regimens has resulted in deep responses, including high rates of negativity for minimal residual disease. These deep responses have translated to long progression-free survival and overall survival rates. Efficacy results for these regimens have generally been consistent across subgroups defined by age, transplant eligibility, and cytogenetic risk. The safety profile of carfilzomib in NDMM is consistent with that observed in the relapsed-refractory MM setting. Clinical studies have found that carfilzomib-based combinations with immunomodulators are highly active with a favorable safety profile in NDMM. The carfilzomib, lenalidomide, and dexamethasone (KRd) drug backbone is a promising foundation for treatment strategies aimed at achieving long-term, deep responses (functional cures) in the frontline setting. Several ongoing studies are evaluating KRd, with or without anti-CD38 monoclonal antibodies.

New proteasome inhibitors in the treatment of multiple myeloma

The treatment of patients with relapsed and/or refractory multiple myeloma has improved considerably in the last 15 years, after the introduction of proteasome inhibitors and immunomodulatory drugs. The first clinical trials with new proteasome inhibitors have produced exciting results, particularly those comparing triplet regimens with standard doublet regimens, with a gain in progression-free survival accompanied by an acceptable safety profile and either similar or better health-related quality of life. New proteasome inhibitors hold the potential to fill unmet needs in multiple myeloma management regarding improvement of clinical outcomes, including delayed progression of disease in high-risk patients. This review summarizes the main pharmacological properties and clinical outcomes of these agents, and discusses their potential to change the whole multiple myeloma therapeutic landscape.

The power of proteasome inhibition in multiple myeloma

INTRODUCTION

Proteasome inhibitors (PIs) are therapeutic backbones of multiple myeloma treatment, with PI-based therapies being standards of care throughout the treatment algorithm. Proteasome inhibition affects multiple critical signaling pathways in myeloma cells and interacts synergistically with mechanisms of action of other conventional and novel agents, resulting in substantial anti-myeloma activity and at least additive effects. Areas covered: This review summarizes the biologic effects of proteasome inhibition in myeloma and provides an overview of the importance of proteasome inhibition to the current treatment algorithm. It reviews key clinical data on three PIs, specifically bortezomib, carfilzomib, and ixazomib; assesses ongoing phase 3 trials with these agents; and looks ahead to the increasingly broad role of both approved PIs and PIs under investigation in the frontline and relapsed settings. Expert commentary: Progress to date with PIs in multiple myeloma has been impressive, but there remain unmet needs and challenges, as well as increasing opportunities to optimize the use of these agents. Understanding discrepancies between PIs in terms of efficacy and safety profile is a key goal of ongoing research, along with proteomics-based efforts to identify potential biomarkers of sensitivity and resistance, thereby enabling increasingly personalized treatment approaches in the future.

Dose and Schedule Selection of the Oral Proteasome Inhibitor Ixazomib in Relapsed/Refractory Multiple Myeloma: Clinical and Model-Based Analyses

Background

The oral proteasome inhibitor ixazomib has been approved by regulatory authorities around the world, including in the United States and the European Union, for the treatment of patients with multiple myeloma (MM) who have received at least one prior therapy, based on the pivotal phase III TOURMALINE-MM1 study.

Objective

The objective of this study was to quantitatively characterize the benefit–risk profile of ixazomib in relapsed/refractory MM in support of the approved dose and schedule.

Methods

We report early-phase study data and exposure–response analyses of TOURMALINE-MM1 data that support the selection of the recommended ixazomib dose and schedule.

Results

Single-agent ixazomib studies showed a favorable efficacy/safety profile with weekly versus twice-weekly dosing; a phase I/II study of ixazomib in combination with lenalidomide and dexamethasone (IRd) identified a weekly ixazomib dose that offered an acceptable efficacy/safety profile. In IRd exposure–response analyses from TOURMALINE-MM1, ixazomib systemic exposure was not a significant predictor of progression-free survival or probability of response. Significant associations were observed between ixazomib exposure and the probability of grade ≥3 anemia and thrombocytopenia, and grade ≥2 diarrhea, fatigue, nausea, peripheral neuropathy, and rash. Additionally, higher ixazomib exposure was associated with lower lenalidomide relative dose intensity.

Conclusions

These analyses support a favorable benefit–risk profile for weekly ixazomib 4.0 mg on days 1, 8, and 15 of 28-day cycles, which was selected for the phase III TOURMALINE registration program.

Trial Registration Numbers

ClinicalTrials.gov NCT00932698, NCT00963820, NCT01217957, NCT01564537

Electronic supplementary material

The online version of this article (doi:10.1007/s11523-017-0524-3) contains supplementary material, which is available to authorized users.

Emerging small molecule approaches to enhance the antimyeloma benefit of proteasome inhibitors

Multiple myeloma (MM) is a clonal plasma cell malignancy which, despite recent treatment advances, remains incurable in the vast majority of the over 118,000 patients in the USA afflicted with this disease. Treatment of MM has dramatically improved in the past decade with the introduction of new drugs into therapeutic strategies in both the frontline and relapse settings that has led to a significant improvement in the median overall survival (OS). These drugs have been incorporated into clinical guidelines and transformed the treatment approach to MM. Numerous classes of antimyeloma agents, i.e., alkylators, steroids, proteasome inhibitors, immunomodulatory agents, deactylase inhibitors, and monoclonal antibodies, are now FDA-approved and can be combined in doublet or triplet regimens. Moreover, many patients do not respond to therapy and those that do eventually relapse. Emerging therapies that may overcome drug resistance and improve MM treatment include that inhibit regulatory and Ub-processing components of the proteasome, a specialized variant of the proteasome known as the immunoproteasome, proteolysis-targeting chimeric molecules (PROTACS and Degronomids). Emerging strategies also include accessory plasmacytoid dendritic cells (pDCs), vaccines, checkpoint inhibitors, and chimeric antigen receptor-engineered T (CAR-T) cells. Advances in understanding proteasome and plasma cell biology may allow for earlier treatment of MM patients using rationally informed combination therapies with curative potential.

The proteasome and proteasome inhibitors in multiple myeloma

Proteasome inhibitors are one of the most important classes of agents to have emerged for the treatment of multiple myeloma in the past two decades, and now form one of the backbones of treatment. Three agents in this class have been approved by the United States Food and Drug Administration-the first-in-class compound bortezomib, the second-generation agent carfilzomib, and the first oral proteasome inhibitor, ixazomib. The success of this class of agents is due to the exquisite sensitivity of myeloma cells to the inhibition of the 26S proteasome, which plays a critical role in the pathogenesis and proliferation of the disease. Proteasome inhibition results in multiple downstream effects, including the inhibition of NF-κB signaling, the accumulation of misfolded and unfolded proteins, resulting in endoplasmic reticulum stress and leading to the unfolded protein response, the downregulation of growth factor receptors, suppression of adhesion molecule expression, and inhibition of angiogenesis; resistance to proteasome inhibition may arise through cellular responses mediating these downstream effects. These multiple biologic consequences of proteasome inhibition result in synergistic or additive activity with other chemotherapeutic and targeted agents for myeloma, and proteasome inhibitor-based combination regimens have become established as a cornerstone of therapy throughout the myeloma treatment algorithm, incorporating agents from the other key classes of antimyeloma agents, including the immunomodulatory drugs, monoclonal antibodies, and histone deacetylase inhibitors. This review gives an overview of the critical role of the proteasome in myeloma and the characteristics of the different proteasome inhibitors and provides a comprehensive summary of key clinical efficacy and safety data with the currently approved proteasome inhibitors.

Pomalidomide enhanced gemcitabine and nab-paclitaxel on pancreatic cancer both in vitro and in vivo

Background

Chemotherapy with gemcitabine and nab-paclitaxel (gemcitabine/nab-paclitaxel) is recommended for unresectable pancreatic cancer. However, the therapeutic efficacy is attenuated by the antitumor agent-induced activation of nuclear factor-κB (NF-κB). Thalidomide inhibits NF-κB activation, therefore, we hypothesized that pomalidomide, a third-generation IMiD, would also inhibit NF-κB activation and enhance the antitumor effects of gemcitabine/nab-paclitaxel.

Methods

In vitro, we assessed NF-κB activity and apoptosis in response to pomalidomide alone, gemcitabine/nab-paclitaxel, or combination of pomalidomide and gemcitabine/nab-paclitaxel in human pancreatic cancer cell lines (PANC-1 and MIA PaCa-2). In vivo, we established orthotopic model and the animals were treated with oral pomalidomide and injection of gemcitabine/nab-paclitaxel.

Results

In pomalidomide and gemcitabine/nab-paclitaxel group, gemcitabine/nab-paclitaxel-induced NF-κB activation was inhibited and apoptosis was enhanced in comparison with those in the other groups both in vitro and in vivo. Especially, this study revealed for the first time that pomalidomide enhances p53 on pancreatic cancer cells. The tumor growth in the pomalidomide and gemcitabine/nab-paclitaxel group was significantly slower than that in the gemcitabine/nab-paclitaxel group. Moreover, pomalidomide induced G0/G1 cell cycle arrest and suppressed angiogenesis.

Conclusions

Pomalidomide enhanced the antitumor effect of gemcitabine/nab-paclitaxel by inhibition of NF-κB activation. This combination regimen would be a novel strategy for treating pancreatic cancer.

A phase 1 clinical trial evaluating marizomib, pomalidomide and low-dose dexamethasone in relapsed and refractory multiple myeloma (NPI-0052-107): final study results

Marizomib (MRZ) is an irreversible, pan-subunit proteasome inhibitor (PI) in clinical development for relapsed/refractory multiple myeloma (RRMM) and glioma. This study analysed MRZ, pomalidomide (POM) and low-dose dexamethasone (Lo-DEX) [PMD] in RRMM to evaluate safety and determine the maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D). Intravenous MRZ (0·3-0·5 mg/m² ) was administered over 2 h on days 1, 4, 8, 11; POM (3-4 mg) on days 1-21; and Lo-DEX (5 or 10 mg) on days 1, 2, 4, 5, 8, 9, 11, 12, 15, 16, 22 and 23 of every 28-day cycle. Thirty-eight patients were enrolled that had received a median of 4 (range 1-10) prior lines of therapy; all patients received prior lenalidomide and bortezomib. No dose-limiting toxicities (DLTs) were observed and 0·5 mg/m² MRZ was determined to be the RP2D. The most common treatment-related ≥Grade 3 adverse events were: neutropenia (11/38 patients: 29%), pneumonia (4/38 patients 11%), anaemia (4/38 patients; 11%) and thrombocytopenia (4/38 patients; 11%). The overall response rate and clinical benefit rate was 53% (19/36) and 64% (23/36), respectively. In conclusion, PMD was well tolerated and demonstrated promising activity in heavily pre-treated, high-risk RRMM patients.

Experimental African trypanosome infection suppresses the development of multiple myeloma in mice by inducing intrinsic apoptosis of malignant plasma cells

Multiple myeloma (MM) is characterized by the accumulation of malignant plasma cells in the bone marrow (BM). Recently, several studies have highlighted the role of pathogens in either promoting or dampening malignancies of unrelated origin. Trypanosoma brucei is an extracellular protozoan parasite which causes sleeping sickness. Our group has previously demonstrated that trypanosome infection affects effector plasma B cells. Therefore, we hypothesized that T. brucei infection could have an impact on MM development. Using the immunocompetent 5T33MM model, we demonstrated a significant reduction in BM-plasmacytosis and M-protein levels in mice infected with T. brucei, resulting in an increased survival of these mice. Blocking IFNγ could only partially abrogate these effects, suggesting that other mechanisms are involved in the destruction of malignant plasma cells. We found that T. brucei induces intrinsic apoptosis of 5T33MM cells in vivo, and that this was associated with reduced endogenous unfolded protein response (UPR) activation. Interestingly, pharmacological inhibition of IRE1α and PERK was sufficient to induce apoptosis in these cells. Together, these results demonstrate that trypanosome infections can interfere with MM development by suppressing endogenous UPR activation and promoting intrinsic apoptosis.

Blockade of Deubiquitylating Enzyme USP1 Inhibits DNA Repair and Triggers Apoptosis in Multiple Myeloma Cells

Purpose: The ubiquitin proteasome pathway is a validated therapeutic target in multiple myeloma. Deubiquitylating enzyme USP1 participates in DNA damage response and cellular differentiation pathways. To date, the role of USP1 in multiple myeloma biology is not defined. In the present study, we investigated the functional significance of USP1 in multiple myeloma using genetic and biochemical approaches.Experimental Design: To investigate the role of USP1 in myeloma, we utilized USP1 inhibitor SJB3-019A (SJB) for studies in myeloma cell lines and patient multiple myeloma cells.Results: USP1-siRNA knockdown decreases multiple myeloma cell viability. USP1 inhibitor SJB selectively blocks USP1 enzymatic activity without blocking other DUBs. SJB also decreases the viability of multiple myeloma cell lines and patient tumor cells, inhibits bone marrow plasmacytoid dendritic cell-induced multiple myeloma cell growth, and overcomes bortezomib resistance. SJB triggers apoptosis in multiple myeloma cells via activation of caspase-3, caspase-8, and caspase-9. Moreover, SJB degrades USP1 and downstream inhibitor of DNA-binding proteins as well as inhibits DNA repair via blockade of Fanconi anemia pathway and homologous recombination. SJB also downregulates multiple myeloma stem cell renewal/survival-associated proteins Notch-1, Notch-2, SOX-4, and SOX-2. Moreover, SJB induced generation of more mature and differentiated plasma cells. Combination of SJB and HDACi ACY-1215, bortezomib, lenalidomide, or pomalidomide triggers synergistic cytotoxicity.Conclusions: Our preclinical studies provide the framework for clinical evaluation of USP1 inhibitors, alone or in combination, as a potential novel multiple myeloma therapy. Clin Cancer Res; 23(15); 4280-9. ©2017 AACR.

Sequencing of nontransplant treatments in multiple myeloma patients with active disease

The approval of several different classes of drugs in recent years has resulted in a dramatic expansion of treatment options for multiple myeloma patients, improving both survival and quality of life. Lenalidomide and bortezomib are now core components of treatment both at time of diagnosis and at relapse. Next-generation immunomodulatory drugs, like pomalidomide, and newer proteasome inhibitors like carfilzomib and ixazomib are available for use at relapse. Drugs with novel mechanisms of action such as the histone deacetylase inhibitor panobinostat and the monoclonal antibodies targeting SLAMF7 (elotuzumab) and CD38 (daratumumab) are significant steps forward. Recent clinical trials describing novel combinations of these drugs have demonstrated unprecedented improvements in efficacy while maintaining tolerability. All of these options provide not only a challenge for choice of therapy, but also the opportunity to aim for increasing depth of response. This chapter will describe an approach on how to sequence and incorporate these therapies, focusing on patients where high-dose melphalan and autologous stem cell transplant are deferred or not applicable.

Salvage therapies in relapsed and/or refractory myeloma: what is current and what is the future?

The treatment landscape for multiple myeloma (MM) is evolving with our understanding of its pathophysiology. However, given the inevitable cohort heterogeneity in salvage therapy, response to treatment and overall prognoses tend to vary widely, making meaningful conclusions about treatment efficacy difficult to derive. Despite the hurdles in current research, progress is underway toward more targeted therapeutic approaches. Several new drugs with novel mechanism of action and less toxic profile have been developed in the past decade, with the potential for use as single agents or in synergy with other treatment modalities in MM therapy. As our discovery of these emerging therapies progresses, so too does our need to reshape our knowledge on knowing how to apply them. This review highlights some of the recent landmark changes in MM management with specific emphasis on salvage drugs available for relapsed and refractory MM and also discusses some of the upcoming cutting-edge therapies that are currently in various stages of clinical development.

Targeting proteasome ubiquitin receptor Rpn13 in multiple myeloma

Proteasome inhibitor bortezomib is an effective therapy for relapsed and newly diagnosed multiple myeloma (MM); however, dose-limiting toxicities and the development of resistance can limit its long-term utility. Recent research has focused on targeting ubiquitin receptors upstream of 20S proteasome, with the aim of generating less toxic therapies. Here we show that 19S proteasome-associated ubiquitin receptor Rpn13 is more highly expressed in MM cells than in normal plasma cells. Rpn13-siRNA (small interfering RNA) decreases MM cell viability. A novel agent RA190 targets Rpn13 and inhibits proteasome function, without blocking the proteasome activity or the 19S deubiquitylating activity. CRISPR/Cas9 Rpn13-knockout demonstrates that RA190-induced activity is dependent on Rpn13. RA190 decreases viability in MM cell lines and patient MM cells, inhibits proliferation of MM cells even in the presence of bone marrow stroma and overcomes bortezomib resistance. Anti-MM activity of RA190 is associated with induction of caspase-dependent apoptosis and unfolded protein response-related apoptosis. MM xenograft model studies show that RA190 is well tolerated, inhibits tumor growth and prolongs survival. Combining RA190 with bortezomib, lenalidomide or pomalidomide induces synergistic anti-MM activity. Our preclinical data validates targeting Rpn13 to overcome bortezomib resistance, and provides the framework for clinical evaluation of Rpn13 inhibitors, alone or in combination, to improve patient outcome in MM.

A novel hypoxia-selective epigenetic agent RRx-001 triggers apoptosis and overcomes drug resistance in multiple myeloma cells

The hypoxic bone-marrow (BM) microenvironment confers growth/survival and drug-resistance in multiple myeloma (MM) cells. Novel therapies targeting the MM cell in its hypoxic-BM milieu may overcome drug resistance. Recent studies led to the development of a novel molecule RRx-001 with hypoxia-selective epigenetic and Nitric Oxide-donating properties. Here we demonstrate that RRx-001 decreases the viability of MM cell lines and primary patient cells, as well as overcomes drug-resistance. RRx-001 inhibits MM cell growth in the presence of BM stromal cells. RRx-001 induced apoptosis is associated with: 1) activation of caspases; 2) release of ROS and nitrogen-species; 3) induction of DNA damage via ATM/γ-H2AX; and 4) decrease in DNA methytransferase (DNMT) and global methylation. RNA interference study shows a predominant role of DNMT1 in MM cell survival versus DNMT3a or DNMT3b. Deubiquitylating enzyme USP7 stimulates DNMT1 activity; and conversely, USP7-siRNA reduced DNMT1 activity and decreased MM cell viability. RRx-001 plus USP7 inhibitor P5091 triggered synergistic anti-MM activity. MM xenograft studies show that RRx-001 is well tolerated, inhibits tumor growth, and enhances survival. Combining RRx-001 with pomalidomide, bortezomib or SAHA induces synergistic anti-MM activity. Our results provide the rationale for translation of RRx-001, either alone or in combination, to clinical evaluation in MM.

Treatment of Relapsed/Refractory Multiple Myeloma

Survival outcomes of patients with Multiple Myeloma (MM) have improved over the last decade due to the introduction of novel agents such as the immunomodulatory drugs thalidomide, lenalidomide (Len) and pomalidomide, and the proteasome inhibitors bortezomib (BTZ) and carfilzomib [1, 2]. However, despite these major advances, MM remains largely incurable and almost all patients relapse and require additional therapy [3]. The successful introduction of next generation novel agents including oral proteasome inhibitors, deacetylase inhibitors, and especially monoclonal antibodies as part of immunotherapy promises to further improve outcome.