New investigational drugs with single-agent activity in multiple myeloma

CD46 and CD59 inhibitors enhance complement-dependent cytotoxicity of anti-CD38 monoclonal antibodies daratumumab and isatuximab in multiple myeloma and other B-cell malignancy cells

Multiple myeloma (MM) is an incurable malignancy of the B-cell lineage. Remarkable progress has been made in the treatment of MM with anti-CD38 monoclonal antibodies such as daratumumab and isatuximab, which can kill MM cells by inducing complement-dependent cytotoxicity (CDC). We showed that the CDC efficacy of daratumumab and isatuximab is limited by membrane complement inhibitors, including CD46 and CD59, which are upregulated in MM cells. We recently developed a small recombinant protein, Ad35K++, which is capable of transiently removing CD46 from the cell surface. We also produced a peptide inhibitor of CD59 (rILYd4). In this study, we tested Ad35K++ and rILYd4 in combination with daratumumab and isatuximab in MM cells as well as in cells from two other B-cell malignancies. We showed that Ad35K++ and rILYd4 increased CDC triggered by daratumumab and isatuximab. The combination of both inhibitors had an additive effect in vitro in primary MM cells as well as in vivo in a mouse xenograft model of MM. Daratumumab and isatuximab treatment of MM lines (without Ad35K++ or rILYd4) resulted in the upregulation of CD46/CD59 and/or survival of CD46high/CD59high MM cells that escaped the second round of daratumumab and isatuximab treatment. The escape in the second treatment cycle was prevented by the pretreatment of cells with Ad35K++. Overall, our data demonstrate that Ad35K++ and rILYd4 are efficient co-therapeutics of daratumumab and isatuximab, specifically in multi-cycle treatment regimens, and could be used to improve treatment of multiple myeloma.

UM171 suppresses breast cancer progression by inducing KLF2

PURPOSE

Breast cancer is the most frequent cancer in women with significant death rate. Morbidity is associated with drug resistance and metastasis. Development of novel drugs is unmet need. The aim of this study is to show potent anti-neoplastic activity of the UM171 compound on breast cancer cells and its mechanism of action.

METHODS

The inhibitory effect of UM171 on several breast cancer (BC) cell lines was examined using MTT and colony-forming assays. Cell cycle and apoptosis assays were utilized to determine the effect of UM171 on BC cell proliferation and survival. Wound healing scratch and transwell migration assays were used to examine the migration of BC cell lines in culture. Xenograft of mouse model with 4T1 cells was used to determine inhibitory effect of UM171 in vivo. Q-RT-PCR and western blotting were used to determine the expression level of genes effected by UM171. Lentivirus-mediated shRNAs were used to knockdown the expression of KLF2 in BC cells.

RESULTS

UM171 was previously identified as a potent agonist of human hematopoietic stem cell renewal and inhibitor of leukemia. In this study, UM171 was shown to inhibit the growth of multiple breast cancer cell lines in culture. UM171-mediated growth inhibition was associated with the induction of apoptosis, G2/M cell cycle arrest, lower colony-forming capacity, and reduced motility. In a xenotransplantation model of mouse triple-negative breast cancer 4T1 cells injected into syngeneic BALB/c mice, UM171 strongly inhibited tumor growth at a level comparable to control paclitaxel. UM171 increased the expression of the three PIM genes (PIM1-3) in breast cancer cells. Moreover, UM171 strongly induced the expression of the tumor suppressor gene KLF2 and cell cycle inhibitor P21CIP1. Accordingly, knockdown of KLF2 using lentivirus-mediated shRNA significantly attenuated the growth suppressor activity of UM171. As PIM1-3 act as oncogenes and are involved in breast cancer progression, induction of these kinases likely impedes the inhibitory effect of KLF2 induction by UM171. Accordingly, combination of UM171 with a PAN-PIM inhibitor LGH447 significantly reduced tumor growth in culture.

CONCLUSION

These results suggested that UM171 inhibited breast cancer progression in part through activation of KLF2 and P21. Combination of UM171 with a PAN-PIM inhibitor offer a novel therapy for aggressive forms of breast cancer.

Dinaciclib synergizes with BH3 mimetics targeting BCL-2 and BCL-XL in multiple myeloma cell lines partially dependent on MCL-1 and in plasma cells from patients

A better understanding of multiple myeloma (MM) biology has led to the development of novel therapies. However, MM is still an incurable disease and new pharmacological strategies are needed. Dinaciclib, a multiple cyclin-dependent kinase (CDK) inhibitor, which inhibits CDK1, 2, 5 and 9, displays significant antimyeloma activity as found in phase II clinical trials. In this study, we have explored the mechanism of dinaciclib-induced death and evaluated its enhancement by different BH3 mimetics in MM cell lines as well as in plasma cells from MM patients. Our results indicate a synergistic effect of dinaciclib-based combinations with B-cell lymphoma 2 or B-cell lymphoma extra-large inhibitors, especially in MM cell lines with partial dependence on myeloid cell leukemia sequence 1 (MCL-1). Simultaneous treatment with dinaciclib and BH3 mimetics ABT-199 or A-1155463 additionally showed a synergistic effect in plasma cells from MM patients, ex vivo. Altered MM cytogenetics did not affect dinaciclib response ex vivo, alone or in combined treatment, suggesting that these combinations could be a suitable therapeutic option for patients bearing cytogenetic alterations and poor prognosis. This work also opens the possibility to explore cyclin-dependent kinase 9 inhibition as a targeted therapy in MM patients overexpressing or with high dependence on MCL-1.

Pulmonary Delivery of Extracellular Vesicle-Encapsulated Dinaciclib as an Effective Lung Cancer Therapy

Simple Summary

The clinical outcomes of lung cancer remain poor. The targeted delivery of treatment and the implementation of a method to overcome drug resistance are essential for the improvement of cancer therapy. The aim of our study was to assess the treatment effectiveness of engineered extracellular vesicles (EV) carrying both dinaciclib, a potent CDK inhibitor, and the proapoptotic factor TRAIL for a combinatorial lung cancer therapy. We showed that the engineered complexed EV agent, EV-T-Dina, was stable both in vitro and in vivo. Importantly, EV-T-Dina can overcome the drug-resistance of lung cancer cells, and when nebulized and administered by the pulmonary route, it demonstrated high efficacy and satisfactory safety for the treatment of lung cancers. The underlying mechanism for the synergistic killing of cancer cells by dinaciclib and TRAIL was associated with the concomitant downregulation of the anti-apoptotic factors cFLIP, MCL-1, and Survivin. Thus, the aerosolized EV-T-Dina potentially constitutes a novel and effective therapy for lung cancers.

Abstract

The clinical outcomes of lung cancer remain poor, mainly due to the chemoresistance and low bioavailability of systemically delivered drugs. Therefore, novel therapeutic strategies are urgently needed. The TNF-related apoptosis-inducing ligand (TRAIL)-armed extracellular vesicle (EV-T) has proven to be highly synergistic for the killing of cancer cells with the potent cyclin-dependent kinase (CDK) inhibitor Dinaciclib (Dina). However, both optimal drug formulations and delivery strategies are yet to be established to facilitate the clinical application of the combination of EV-T and Dina. We hypothesize that Dina can be encapsulated into EV-T to produce a complexed formulation, designated EV-T-Dina, which can be nebulized for pulmonary delivery to treat lung cancer with potentially improved efficacy and safety. The prepared EV-T-Dina shows good stability both in vitro and in vivo and is very efficient at killing two highly TRAIL-resistant cancer lines. The ability to overcome TRAIL resistance is associated with the concomitant downregulation of the expression of cFLIP, MCL-1, and Survivin by Dina. The EV-T-Dina solution is nebulized for inhalation, showing unique deposition in animal lungs and importantly it demonstrates a significant suppression of the growth of orthotopic A549 tumors without any detectable adverse side events. In conclusion, the aerosolized EV-T-Dina constitutes a novel therapy, which is highly effective and safe for the treatment of lung cancers.

Overexpression of immunoproteasome low-molecular-mass polypeptide 7 and inhibiting role of next-generation proteasome inhibitor ONX 0912 on cell growth in glioma

OBJECTIVES

The aim of this study was to determine the expression level of immunoproteasome and its clinical significance in glioma preliminarily. Furthermore, we studied the function and molecular mechanism of proteasome inhibitor ONX 0912 on glioma cell.

MATERIALS AND METHODS

The expression of immunoproteasome in glioma and tumor-adjacent brain tissues was detected by western blot. Immunohistochemical technique was used to detect the expression of low-molecular-mass polypeptide 7 in 55 cases of glioma tissues and 6 cases of tumor-adjacent brain tissues. Chi-square test was used to analyze the relationship between the expression level of low-molecular-mass polypeptide 7 and clinical characteristics. Kaplan-Meier method and Cox regression analysis were applied to analyze the correlation between low-molecular-mass polypeptide 7 expression and prognosis of patients. 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2Htetrazolium) (MTS) proliferation assay was introduced to detect the impact of ONX 0912 on proliferation of glioma cells. Western blot was used to detect the apoptosis- and autophagy-related protein in glioma cell treated with ONX 0912.

RESULTS

Our results showed that only low-molecular-mass polypeptide 7 expression was notably upregulated in gliomas in comparison with tumor-adjacent brain tissues and further increased in malignant gliomas compared with benign gliomas (P < 0.01). In the multivariate Cox proportional regression analyses, it was evident that low-molecular-mass polypeptide 7 was an independent unfavorable prognostic factor (P < 0.05). The results of MTS assay showed that ONX 0912 could inhibit the proliferation of glioma cell. Besides, we found that ONX 0912 could prompt apoptosis and autophagosome accumulation, which may be responsible for inhibiting glioma cell proliferation.

CONCLUSION

In conclusion, our results indicated that low-molecular-mass polypeptide 7 might be a candidate prognostic biomarker, and proteasome inhibitor ONX 0912 might act as a potential treatment agent for glioma.

Therapeutic targeting of PIM KINASE signaling in cancer therapy: Structural and clinical prospects

BACKGROUND

PIM kinases are well-studied drug targets for cancer, belonging to Serine/Threonine kinases family. They are the downstream target of various signaling pathways, and their up/down-regulation affects various physiological processes. PIM family comprises three isoforms, namely, PIM-1, PIM-2, and PIM-3, on alternative initiation of translation and they have different levels of expression in different types of cancers. Its structure shows a unique ATP-binding site in the hinge region which makes it unique among other kinases.

SCOPE OF REVIEW

PIM kinases are widely reported in hematological malignancies along with prostate and breast cancers. Currently, many drugs are used as inhibitors of PIM kinases. In this review, we highlighted the physiological significance of PIM kinases in the context of disease progression and therapeutic targeting. We comprehensively reviewed the PIM kinases in terms of their expression and regulation of different physiological roles. We further predicted functional partners of PIM kinases to elucidate their role in the cellular physiology of different cancer and mapped their interaction network.

MAJOR CONCLUSIONS

A deeper mechanistic insight into the PIM signaling involved in regulating different cellular processes, including transcription, apoptosis, cell cycle regulation, cell proliferation, cell migration and senescence, is provided. Furthermore, structural features of PIM have been dissected to understand the mechanism of inhibition and subsequent implication of designed inhibitors towards therapeutic management of prostate, breast and other cancers.

GENERAL SIGNIFICANCE

Being a potential drug target for cancer therapy, available drugs and PIM inhibitors at different stages of clinical trials are discussed in detail.

Targeting the Ubiquitin-Proteasome System for Cancer Therapeutics by Small-Molecule Inhibitors

The ubiquitin-proteasome system (UPS) is a critical regulator of cellular protein levels and activity. It is, therefore, not surprising that its dysregulation is implicated in numerous human diseases, including many types of cancer. Moreover, since cancer cells exhibit increased rates of protein turnover, their heightened dependence on the UPS makes it an attractive target for inhibition via targeted therapeutics. Indeed, the clinical application of proteasome inhibitors in treatment of multiple myeloma has been very successful, stimulating the development of small-molecule inhibitors targeting other UPS components. On the other hand, while the discovery of potent and selective chemical compounds can be both challenging and time consuming, the area of targeted protein degradation through utilization of the UPS machinery has seen promising developments in recent years. The repertoire of proteolysis-targeting chimeras (PROTACs), which employ E3 ligases for the degradation of cancer-related proteins via the proteasome, continues to grow. In this review, we will provide a thorough overview of small-molecule UPS inhibitors and highlight advancements in the development of targeted protein degradation strategies for cancer therapeutics.

Comparison of CD38-Targeted α- Versus β-Radionuclide Therapy of Disseminated Multiple Myeloma in an Animal Model

Targeted therapies for multiple myeloma (MM) include the anti-CD38 antibody daratumumab, which, in addition to its inherent cytotoxicity, can be radiolabeled with tracers for imaging and with β- and α-emitter radionuclides for radioimmunotherapy. Methods: We have compared the potential therapeutic efficacy of β- versus α-emitter radioimmunotherapy using radiolabeled DOTA-daratumumab in a preclinical model of disseminated multiple myeloma. Multiple dose levels were investigated to find the dose with the highest efficacy and lowest toxicity. Results: In a dose–response study with the β-emitter 177Lu-DOTA-daratumumab, the lowest tested dose, 1.85 MBq, extended survival from 37 to 47 d but did not delay tumor growth. Doses of 3.7 and 7.4 MBq extended survival to 55 and 58 d, respectively, causing a small equivalent delay in tumor growth, followed by regrowth. The higher dose, 11.1 MBq, eradicated the tumor but had no effect on survival compared with untreated controls, because of whole-body toxicity. In contrast, the α-emitter 225Ac-DOTA-daratumumab had a dose-dependent effect, in which 0.925, 1.85, and 3.7 kBq increased survival, compared with untreated controls (35 d), to 47, 52, and 73 d, respectively, with a significant delay in tumor growth for all 3 doses. Higher doses of 11.1 and 22.2 kBq resulted in equivalent survival to 82 d but with significant whole-body toxicity. Parallel studies with untargeted 225Ac-DOTA-trastuzumab conferred no improvement over untreated controls and resulted in whole-body toxicity. Conclusion: We conclude, and mathematic modeling confirms, that maximal biologic doses were achieved by targeted α-therapy and demonstrated 225Ac to be superior to 177Lu in delaying tumor growth and decreasing whole-body toxicity.

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.

Small Molecule NF-κB Pathway Inhibitors in Clinic

Nuclear factor kappa B (NF-κB) signaling is implicated in all major human chronic diseases, with its role in transcription of hundreds of gene well established in the literature. This has propelled research into targeting the NF-κB pathways for modulating expression of those genes and the diseases mediated by them. In-spite of the critical, but often promiscuous role played by this pathway and the inhibition causing adverse drug reaction, currently many biologics, macromolecules, and small molecules that modulate this pathway are in the market or in clinical trials. Furthermore, many marketed drugs that were later found to also have NF-κB targeting activity were repurposed for new therapeutic interventions. Despite the rising importance of biologics in drug discovery, small molecules got around 76% of US-FDA (Food and Drug Administration-US) approval in the last decade. This encouraged us to review information regarding clinically relevant small molecule inhibitors of the NF-κB pathway from cell surface receptor stimulation to nuclear signaling. We have also highlighted the underexplored targets in this pathway that have potential to succeed in clinic.

"Direct to Drug" screening as a precision medicine tool in multiple myeloma

Seventy-six FDA-approved oncology drugs and emerging therapeutics were evaluated in 25 multiple myeloma (MM) and 15 non-Hodgkin’s lymphoma cell lines and in 113 primary MM samples. Ex vivo drug sensitivities were mined for associations with clinical phenotype, cytogenetic, genetic mutation, and transcriptional profiles. In primary MM samples, proteasome inhibitors, dinaciclib, selinexor, venetoclax, auranofin, and histone deacetylating agents had the broadest cytotoxicity. Of interest, newly diagnosed patient samples were globally less sensitive especially to bromodomain inhibitors, inhibitors of receptor tyrosine kinases or non-receptor kinases, and DNA synthesis inhibitors. Clustering demonstrated six broad groupings of drug sensitivity linked with genomic biomarkers and clinical outcomes. For example, our findings mimic clinical observations of increased venetoclax responsiveness in t(11;14) patients but also identify an increased sensitivity profile in untreated patients, standard genetic risk, low plasma cell S-Phase, and in the absence of Gain(1q) and t(4;14). In contrast, increased ex vivo responsiveness to selinexor was associated with biomarkers of poor prognosis and later relapse patients. This “direct to drug” screening resource, paired with functional genomics, has the potential to successfully direct appropriate individualized therapeutic approaches in MM and to enrich clinical trials for likely responders.

PAI1 is a Marker of Bad Prognosis in Rectal Cancer but Predicts a Better Response to Treatment with PIM Inhibitor AZD1208

Colorectal cancer (CRC) is the third most common cancer worldwide. The standard treatment in locally advanced rectal cancer is preoperative radiation alone or in combination with chemotherapy, followed by adjuvant chemotherapy. Rectal cancer is highly lethal, with only 20% of patients showing a complete remission (by RECIST) after standard treatment, although they commonly show local or systemic relapse likely due to its late detection and high chemotherapy resistance, among other reasons. Here, we explored the role of PAI1 (Serpin E1) in rectal cancer through the analyses of public patient databases, our own cohort of locally advanced rectal cancer patients and a panel of CRC cell lines. We showed that PAI1 expression is upregulated in rectal tumors, which is associated with decreased overall survival and increased metastasis and invasion in advanced rectal tumors. Accordingly, PAI1 expression is correlated with the expression of (Epithelial-to-Mesenchymal Transition) EMT-associated genes and genes encoding drug targets, including the tyrosine kinases PDGFRb, PDGFRa and FYN, the serine/threonine kinase PIM1 and BRAF. In addition, we demonstrate that cells expressing PAI1 protein are more sensitive to the PIM inhibitor AZD1208, suggesting that PAI1 could be used to predict response to treatment with PIM inhibitors and to complement radiotherapy in rectal tumors.

Daratumumab induces mechanisms of immune activation through CD38+ NK cell targeting

Daratumumab (Dara), a multiple myeloma (MM) therapy, is an antibody against the surface receptor CD38, which is expressed not only on plasma cells but also on NK cells and monocytes. Correlative data have highlighted the immune-modulatory role of Dara, despite the paradoxical observation that Dara regimens decrease the frequency of total NK cells. Here we show that, despite this reduction, NK cells play a pivotal role in Dara anti-MM activity. CD38 on NK cells is essential for Dara-induced immune modulation, and its expression is restricted to NK cells with effector function. We also show that Dara induces rapid CD38 protein degradation associated with NK cell activation, leaving an activated CD38-negative NK cell population. CD38+ NK cell targeting by Dara also promotes monocyte activation, inducing an increase in T cell costimulatory molecules (CD86/80) and enhancing anti-MM phagocytosis activity ex-vivo and in vivo. In support of Dara’s immunomodulating role, we show that MM patients that discontinued Dara therapy because of progression maintain targetable unmutated surface CD38 expression on their MM cells, but retain effector cells with impaired cellular immune function. In summary, we report that CD38+ NK cells may be an unexplored therapeutic target for priming the immune system of MM patients.

Drug Development Targeting the Ubiquitin-Proteasome System (UPS) for the Treatment of Human Cancers

Cancer cells are characterized by a higher rate of protein turnover and greater demand for protein homeostasis compared to normal cells. In this scenario, the ubiquitin-proteasome system (UPS), which is responsible for the degradation of over 80% of cellular proteins within mammalian cells, becomes vital to cancer cells, making the UPS a critical target for the discovery of novel cancer therapeutics. This review systematically categorizes all current reported small molecule inhibitors of the various essential components of the UPS, including ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), ubiquitin ligases (E3s), the 20S proteasome catalytic core particle (20S CP) and the 19S proteasome regulatory particles (19S RP), as well as their mechanism/s of action and limitations. We also discuss the immunoproteasome which is considered as a prospective therapeutic target of the next generation of proteasome inhibitors in cancer therapies.

DCZ0814 induces apoptosis and G0/G1 phase cell cycle arrest in myeloma by dual inhibition of mTORC1/2

Purpose: The present study investigates the effect of DCZ0814 in multiple myeloma (MM) cells, and determines the molecular mechanism of its antitumor activity against MM.

Methods: The effects of DCZ0814 were evaluated in vitro using human MM cell lines (ARP1 and OCI-MY5) and in vivo in a murine xenograft MM model. Cell viability was measured with the CCK-8 assay and mitochondrial membrane potential (MMP) was assessed with the JC-1 dye. Apoptosis and cell cycle distribution were examined by flow cytometry. Inhibition of mTORC1 and mTORC2 was assessed by western blot analysis, and the synergistic effect of DCZ0814 and known MM drugs was assessed by calculating the combination index value, using the CalcuSyn software.

Results: DCZ0814 effectively inhibited proliferation in MM cells, an effect that was associated with the induction of apoptosis, G0/G1 cell cycle arrest, MMP reduction and reactive oxygen species (ROS) generation. Meanwhile, DCZ0814 repressed the mTOR signaling via dual mTORC1/C2 inhibition and overcame the protective effect of the bone marrow (BM) microenvironment in myeloma cells. In addition, co-treatment with DCZ0814 and other anti-MM agents induced synergistic effects. Finally, the efficacy of the DCZ0814 treatment was confirmed in an MM xenograft mouse model.

Conclusion: DCZ0814 exhibits potent anti-MM activity and abrogates the activation of the mTOR/Akt signaling pathway mediated by the BM stroma-derived cytokines. Our results provide a theoretical basis for the development of novel therapeutic strategies in MM using DCZ0814 as a natural product combination compound.

Clinical efficacy of daratumumab, pomalidomide, and dexamethasone in patients with relapsed or refractory myeloma: Utility of re-treatment with daratumumab among refractory patients

BACKGROUND

The efficacy of daratumumab (DARA) both as a monotherapy and in combination with standard-of-care regimens in multiple myeloma (MM) has been established in clinical trials. This article presents a retrospective analysis of the safety and efficacy of DARA in combination with pomalidomide (POM) and dexamethasone (ie, daratumumab, pomalidomide, and dexamethasone [DARA-POM-D]) and, more importantly, the long-term follow-up of a cohort that was naive to DARA and POM as well as a cohort in which the utility of re-treatment was evaluated among patients who were DARA- and/or POM-refractory.

METHODS

Thirty-four consecutive patients with relapsed and/or refractory MM treated with DARA-POM-D at the Winship Cancer Institute of Emory University from January 2015 through July 2016 were included in the analysis. The study was approved by Emory University's institutional review board. All received prior proteasome inhibitors and immunomodulatory drugs (IMiDs) and were refractory to their last line of therapy.

RESULTS

All patients were lenalidomide-refractory, and 91% were bortezomib-refractory. Two cohorts were identified on the basis of prior exposure to DARA and/or POM. Cohort 1 (12 patients) was DARA- and POM-naive, and cohort 2 (22 patients) was DARA- and/or POM-refractory. A subgroup of 12 patients in cohort 2 (cohort 3) was DARA- and POM-refractory. The combination's tolerability was consistent with the results of the published phase 1b study (EQUULES) that evaluated the combination and no new safety signals were observed. The overall response rates (ORRs) were 91.7%, 40.9%, and 33.3% in cohorts 1, 2, and 3, respectively. Deep responses, including 4 stringent complete responses, were observed in cohort 1. In cohort 2, the ORR comprised 8 partial responses (PRs) and 1 very good PR. The median progression-free survival (PFS) was not reached in cohort 1 at a median follow-up of 41 months, and it was 3.2 months in cohort 2. DARA-POM-D not only was effective in DARA- and POM-naive patients but also produced clinical responses in a third of patients re-treated with these drugs.

CONCLUSIONS

A better than quadrupled PFS benefit observed in cohort 1 in comparison with the previously reported benefit in the EQUULEUS trial (which led to US Food and Drug Administration approval of the DARA-POM-D combination) highlights the fact that the introduction of monoclonal antibody combination strategies and IMiDs as earlier lines of therapeutic options potentially could deliver better clinical outcomes. One-third of patients refractory to separate lines of DARA and/or POM responded when they were re-treated with a combination, and this resulted in survival benefits equivalent to those of other antimyeloma agents/combinations available for DARA-refractory patients.

Development of Novel Epoxyketone-Based Proteasome Inhibitors as a Strategy To Overcome Cancer Resistance to Carfilzomib and Bortezomib

Over the past 15 years, proteasome inhibitors (PIs), namely bortezomib, carfilzomib (Cfz) and ixazomib, have significantly improved the overall survival and quality-of-life for multiple myeloma (MM) patients. However, a significant portion of MM patients do not respond to PI therapies. Drug resistance is present either de novo or acquired after prolonged therapy through mechanisms that remain poorly defined. The lack of a clear understanding of clinical PI resistance has hampered the development of next-generation PI drugs to treat MM patients who no longer respond to currently available therapies. Here, we designed and synthesized novel epoxyketone-based PIs by structural modifications at the P1' site. We show that a Cfz analog, 9, harboring a hydroxyl substituent at its P1' position was highly cytotoxic against cancer cell lines displaying de novo or acquired resistance to Cfz. These results suggest that peptide epoxyketones incorporating P1'-targeting moieties may have the potential to bypass resistance mechanisms associated with Cfz and to provide additional clinical options for patients resistant to Cfz.

Survival rate of multiple myeloma patients in Indonesia: A retrospective study in multiple myeloma at a single institution

Introduction

To evaluate the response and the correlation between survival and prognostic factors in 32 patients with multiple myeloma.

Method

We recruited 32 patients (18 men and 14 women) with mean age 59 years old who were diagnosed with multiple myeloma that were treated with surgery (n = 21) and without surgery (n = 11). 9 patients underwent hemiarthroplasty, 14 patients underwent open reduction and internal fixation and 4 patients underwent spinal decompression and posterior pedicular instrumentation from January 2012 to December 2017. In this group, there were 6 patients who underwent more than one surgeries. Patients were classified using the International Staging System (ISS) for multiple myeloma by evaluated albumin and β₂-microglobulin level.

Results

The mean follow up period for 32 patients was 30.2 months (range, 3–65 months) with 7 patients in ISS stage I, 22 patients in ISS stage II and 3 patients in ISS stage III. The median survival duration was 28 months (95% CI). We documented the median survival for ISS stage II disease was 29 months, stage III disease 6 months and stage I disease 16 months with the median age of ISS stage I, II, and III disease was 65, 59, 60 years respectively. Survival correlation with ISS stage (p = 0.009), the hemoglobin level (p = 0.772), and the calcium level (p = 0.926).

Conclusions

The survival rate was lower in patients with higher ISS stage for this disease. Survival rate seems to be better among younger patients than in older ones even with lower ISS stage of this disease.

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Multiple myeloma remains an incurable disease that the survival rate was lower in patients with higher ISS stage.

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Regarding the prognostic impact of age, survival seems to be better among patients younger than in older patients.

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In this study, calcium and hemoglobin level is not correlated with the prognosis of patients with multiple myeloma.

High adherence of patients with multiple myeloma who receive treatment with immunomodulatory drugs (IMIDS) in hematology/oncology group practices in Germany

PURPOSE

Immunomodulatory drugs (IMIDS) have changed the treatment and outcome of patients suffering from multiple myeloma. However, with the oral administration adherence becomes an issue. Since there is no "gold standard" in measuring adherence, we assessed the adherence of myeloma patients with the help of different data sources.

METHODS

All patients who have been receiving IMIDS for at least 3 months were eligible. Computer assisted personal interviews of patients and, if possible, their caregivers were carried out. Attending oncologists evaluated the patient's adherence with the help of a standardized questionnaire. In addition, a retrospective analysis of prescription data was conducted. All data were analyzed statistically using SPSS.

RESULTS

One hundred myeloma patients, 35% female, 65% male, with a median age of 70 years (37-86) were interviewed. Prescription data could be evaluated in terms of adherence in 78 patients (78%), 56 caregivers could be questioned (56%). Ninety-seven percent of patients rated themselves as adherent in taking IMIDS. Data from treating oncologists, caregivers and prescriptions supported this result. IMID therapies were rated as very effective and significant, toxicities were acceptable and dosing regimens simple/uncomplicated.

CONCLUSIONS

Myeloma patients seem to be highly adherent to IMID treatments.

Proteasome Inhibition in Multiple Myeloma: Head-to-Head Comparison of Currently Available Proteasome Inhibitors

Proteasome inhibitors (PIs) are a backbone of multiple myeloma (MM) therapy. The proteasome harbors six proteolytically active subunits (β1, β2, β5), while β5 was identified as rate-limiting and is a primary target of clinically available PIs. The most effective pattern of subunit inhibition provided by these PIs for cytotoxic activity in MM is unknown. A head-to-head comparison of clinically available PIs shows that in the clinically relevant setting only the co-inhibition of β1 or β2 with β5 activity achieves meaningful functional proteasome inhibition and cytotoxicity, while the selective β2/β5 inhibition of both constitutive and immunoproteasome is the most cytotoxic. In the long-term setting, selective inhibition of β5 subunit is sufficient to induce cytotoxicity in PI-sensitive, but not in PI-resistant MM, and the β5/β2 co-inhibition is the most cytotoxic in PI-resistant MM. These results give a rational basis for selecting individual PIs for the treatment of MM.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

Overall survival of transplant eligible patients with newly diagnosed multiple myeloma: comparative effectiveness analysis of modern induction regimens on outcome

Overall survival (OS) of multiple myeloma has improved remarkably over time, with the recent Intergroupe Francophone du Myelome (IFM) 2009 randomized trial reporting a 4-year OS rate of approximately 82% in patients receiving modern therapy. However, survival estimates from clinical trials may overestimate outcomes seen in clinical practice even with the adjustment for age and other key characteristics. The purpose of this study was to determine the OS of myeloma patients seen in routine clinical practice who resembled the cohort studied in the IFM 2009 trial. A second goal was to conduct a brief comparative effectiveness analysis of bortezomib, lenalidomide, dexamethasone, and other major induction regimens used during the study period. We studied all patients with myeloma 65 years of age and younger, seen at the Mayo Clinic between January 1, 2010 and August 31, 2015, who had a stem cell harvest performed within 12 months of initial diagnosis. Patients with baseline serum creatinine >2 mg/dL were excluded. Five hundred and eighteen patients were studied. The 4-year OS rate was 82.3%, comparable to results achieved in the contemporaneous IFM randomized trial. The 4-year OS rates for standard and high-risk myeloma were 86.3% and 68.2%, respectively.

The Epigenome in Multiple Myeloma: Impact on Tumor Cell Plasticity and Drug Response

Multiple myeloma (MM) is a clonal plasma cell malignancy that develops primarily in the bone marrow (BM), where reciprocal interactions with the BM niche foster MM cell survival, growth, and drug resistance. MM cells furthermore reshape the BM to their own needs by affecting the different BM stromal cell types resulting in angiogenesis, bone destruction, and immune suppression. Despite recent advances in treatment modalities, MM remains most often incurable due to the development of drug resistance to all standard of care agents. This underscores the unmet need for these heavily treated relapsed/refractory patients. Disruptions in epigenetic regulation are a well-known hallmark of cancer cells, contributing to both cancer onset and progression. In MM, sequencing and gene expression profiling studies have also identified numerous epigenetic defects, including locus-specific DNA hypermethylation of cancer-related and B cell specific genes, genome-wide DNA hypomethylation and genetic defects, copy number variations and/or abnormal expression patterns of various chromatin modifying enzymes. Importantly, these so-called epimutations contribute to genomic instability, disease progression, and a worse outcome. Moreover, the frequency of mutations observed in genes encoding for histone methyltransferases and DNA methylation modifiers increases following treatment, indicating a role in the emergence of drug resistance. In support of this, accumulating evidence also suggest a role for the epigenetic machinery in MM cell plasticity, driving the differentiation of the malignant cells to a less mature and drug resistant state. This review discusses the current state of knowledge on the role of epigenetics in MM, with a focus on deregulated histone methylation modifiers and the impact on MM cell plasticity and drug resistance. We also provide insight into the potential of epigenetic modulating agents to enhance clinical drug responses and avoid disease relapse.

CD38-Specific Biparatopic Heavy Chain Antibodies Display Potent Complement-Dependent Cytotoxicity Against Multiple Myeloma Cells

CD38 is overexpressed by multiple myeloma cells and has emerged as a target for therapeutic antibodies. Nanobodies are soluble single domain antibody fragments derived from the VHH variable domain of heavy chain antibodies naturally occurring in camelids. We previously identified distinct llama nanobodies that recognize three non-overlapping epitopes of the extracellular domain of CD38. Here, we fused these VHH domains to the hinge, CH2, and CH3 domains of human IgG1, yielding highly soluble chimeric llama/human heavy chain antibodies (hcAbs). We analyzed the capacity of these hcAbs to mediate complement-dependent cytotoxicity (CDC) to CD38-expressing human multiple myeloma and Burkitt lymphoma cell lines. Combinations of two hcAbs that recognize distinct, non-overlapping epitopes of CD38 mediated potent CDC, in contrast to the hcAb monotherapy with only weak CDC capacity. Similarly, combining daratumumab with a hcAb that recognizes a non-overlapping epitope resulted in dramatically enhanced CDC. Further, introducing the E345R HexaBody mutation into the CH3 domain strongly enhanced the CDC potency of hcAbs to CD38-expressing cells. Exploiting their high solubility, we genetically fused two distinct nanobodies into heteromeric dimers via a flexible peptide linker and then fused these nanobody dimers to the hinge, CH2 and CH3 domains of human IgG1, yielding highly soluble, biparatopic hcAbs. These biparatopic hcAbs elicited CDC toward CD38-expressing myeloma cells more effectively than daratumumab. Our results underscore the advantage of nanobodies vs. pairs of VH and VL domains for constructing bispecific antibodies. Moreover, the CD38-specific biparatopic heavy chain antibodies described here represent potential new powerful therapeutics for treatment of multiple myeloma.

Perspectives for the Development of CD38-Specific Heavy Chain Antibodies as Therapeutics for Multiple Myeloma

The NAD⁺-metabolizing ectoenzyme CD38 is an established therapeutic target in multiple myeloma. The CD38-specific monoclonal antibodies daratumumab and isatuximab show promising results in the clinic. Nanobodies correspond to the single variable domains (VHH) derived from heavy chain antibodies that naturally occur in camelids. VHHs display high solubility and excellent tissue penetration in vivo. We recently generated a panel of CD38-specific nanobodies, some of which block or enhance the enzymatic activity of CD38. Fusion of such a nanobody to the hinge, CH2, and CH3 domains of human IgG1 generates a chimeric llama/human hcAb of about half the size of a conventional moAb (75 vs. 150 kDa). Similarly, a fully human CD38-specific hcAb can be generated using a CD38-specific human VH3 instead of a CD38-specific camelid nanobody. Here we discuss the advantages and disadvantages of CD38-specific hcAbs vs. conventional moAbs and provide an outlook for the potential use of CD38-specific hcAbs as novel therapeutics for multiple myeloma.

Value and Cost of Myeloma Therapy

Major advances have occurred in the treatment of multiple myeloma, including several new drugs that typically cost more than $100,000 per year. Although the gains in myeloma therapy improve overall survival considerably, they are available to only a fraction of the population of patients with myeloma in the world because of regulatory barriers and cost. Myeloma is an example of what is happening in cancer on a much larger scale. Many of the problems discussed call for a wider discussion across all cancers, but they are amplified in myeloma because of the need for multidrug regimens that combine three or more expensive new drugs for prolonged periods of time. In this article, the reasons for the high cost of cancer drugs and possible solutions are examined. The lack of correlation of value and price, the remarkable rise in prices of existing old medications over time, and the lack of access to lifesaving drugs across various countries are also discussed.

Future in the Past: Azorella glabra Wedd. as a Source of New Natural Compounds with Antiproliferative and Cytotoxic Activity on Multiple Myeloma Cells

Multiple myeloma (MM) is the second most common hematologic malignancy and, although the development of novel agents has improved survival of patients, to date, it remains incurable. Thus, newer and more effective therapeutic strategies against this malignancy are necessary. Plant extracts play an important role in anti-tumor drug discovery. For this reason, in the investigation of novel natural anti-MM agents, we evaluated the phytochemical profiles, in vitro antioxidant activity, and effects on MM cells of Azorella glabra (AG) Wedd. Total polyphenols (TPC), flavonoids (TFC), and terpenoids (TTeC) contents were different among samples and the richest fractions in polyphenols demonstrated a higher antioxidant activity in in vitro assays. Some fractions showed a dose and time dependent anti-proliferative activity on MM cells. The chloroform fraction (CHCl₃) showed major effects in terms of reduction of cell viability, induction of apoptosis, and cell cycle arrest on MM cells. The apoptosis induction was also confirmed by the activation of caspase-3. Importantly, the CHCl₃ fraction exhibited a negligible effect on the viability of healthy cells. These results encourage further investigations on AG extracts to identify specific bioactive compounds and to define their potential applications in MM.

Next-generation proteasome inhibitors for cancer therapy

Over 2 decades ago, the proteasome was considered a risky or even untenable therapeutic target. Today, proteasome inhibitors are a mainstay in the treatment of multiple myeloma (MM) and have sales in excess of 3 billion US dollars annually. More importantly, the availability of proteasome inhibitors has greatly improved the survival and quality of life for patients with MM. Despite the remarkable success of proteasome inhibitor therapies to date, the potential for improvement remains, and the development and optimal use of proteasome inhibitors as anticancer agents continues to be an active area of research. In this review, we briefly discuss the features and limitations of the 3 proteasome inhibitor drugs currently used in the clinic and provide an update on current efforts to develop next-generation proteasome inhibitors with the potential to overcome the limitations of existing proteasome inhibitor drugs.

Daratumumab induces CD38 internalization and impairs myeloma cell adhesion

Daratumumab (Dara), a human immunoglobulin G1 kappa (IgG1κ) monoclonal anti-CD38 antibody, has been approved by the U.S. Food and Drug Administration for the treatment of relapsed multiple myeloma (MM) as a single agent as well as in combination with immunomodulatory drugs (IMiDs) and proteasome inhibitors (PI). Although the scientific rationale behind the use of Dara in combination with IMiDs has been extensively explored, the molecular mechanisms underlying Dara-PI regimens have not yet been investigated. Here, we demonstrate that CD38 on the surface of MM cells is rapidly internalized after Dara treatment; we also show that Dara treatment impairs MM cell adhesion, an effect that can be rescued by using the endocytosis inhibitor Dynasore. Finally, we show that Dara potentiates bortezomib (BTZ) killing of MM cells in vitro and in vivo, independent of its function as an immune activator. In conclusion, our data show that Dara impairs MM cell adhesion, which results in an increased sensitivity of MM to proteasome inhibition.

PDK1 inhibitor GSK2334470 exerts antitumor activity in multiple myeloma and forms a novel multitargeted combination with dual mTORC1/C2 inhibitor PP242

A deeper understanding of the complex pathogenesis of multiple myeloma (MM) continues to lead to novel therapeutic approaches. Prior studies suggest that 3-phosphoinositide-dependent kinase 1 (PDK1) is expressed and active, acting as a crucial regulator of molecules that are essential for myelomagenesis. In the present study, we show that GSK2334470 (GSK-470), a novel and highly specific inhibitor of PDK1, induces potent cytotoxicity in MM cell lines including Dexamethasone-resistant cell line, but not in human normal cells. Insulin-like growth factor-1 could not rescue GSK-470-induced cell death. Moreover, GSK-470 down-modulates phosphor-PDK1, thereby inhibiting downstream phosphor-AKT at Thr308 and mTOR complex 1 (mTORC1) activity. However, GSK-470 could not affect mTORC2 activity and phosphor-AKT at Ser473. RPMI 8226 and OPM-2 cells with low expression of PTEN show relative resistant to GSK-470. Knockout of PTEN by shRNA resulted in a partial reversion of GSK-470-mediated growth inhibition, whereas overexpression of PTEN enhanced myeloma cell sensitivity to GSK-470, suggesting that the sensitivity to GSK-470 is correlated with PTEN expression statue in MM cells. Combining PP242, a dual mTORC1/C2 inhibitor, with GSK-470, had greater antimyeloma activity than either one alone in vitro and in MM xenograft model established in immunodeficient mice. In particular, this combination was able to result in a complete inhibition of mTORC1/C2 and full activity of AKT. Together, these findings raise the possibility that combining PDK1 antagonist GSK-470 with mTORC1/C2 inhibitors may represent a novel strategy against MM including drug-resistant myeloma, regardless of PTEN expression status.

The evolution of stem-cell transplantation in multiple myeloma

Autologous stem-cell transplantation (ASCT) remains an integral part of treatment for previously untreated, and may have value in the treatment of relapsed patients with, multiple myeloma (MM). The addition of novel agents like immunomodulators and proteasome inhibitors as induction therapy before and as consolidation/maintenance therapy after ASCT has led to an improvement in complete response (CR) rates, progression-free survival (PFS) and overall survival (OS). With advances in supportive care, older patients and patients with renal insufficiency are now able to safely undergo the procedure. The data concerning the timing of ASCT (early in the disease course or at first relapse), single versus tandem (double) ASCT and the role and duration of consolidation and maintenance therapy post ASCT remain conflicting. This review aims to discuss the evolution of stem-cell transplant over the past 3 decades and its current role in the context of newer, safer and more effective therapeutic agents.

Emerging alternatives to tyrosine kinase inhibitors for treating chronic myeloid leukemia

INTRODUCTION

BCR-ABL-directed tyrosine kinase inhibitors (TKIs) have revolutionised therapy for chronic myeloid leukemia. However, despite the availability and efficacy of this class of agents, lifelong treatment is still required in a significant proportion of patients Areas covered: We give an overview of the currently available BCR-ABL-directed TKIs and other conventional therapies for CML. We proceed to review the current market and some of the scientific rationale for new drug development before outlining a number of novel therapies, considered broadly as immunotherapies and targeted agents. Published English-language literature was reviewed regarding currently available TKIs; clinical trials repositories were reviewed to identify novel agents recently investigated or under active study. Expert opinion: We recommend discussion with patients and enrolment on an appropriate clinical trial where feasible. In situations where no trials are available, or if patients decline enrolment, we recommend use of an appropriate BCR-ABL directed TKI, selected on the basis of an evaluation of patient risk factors and side effect profile. Allogeneic stem cell transplant continues to have a role though this is generally limited to cases with advanced phases of disease or in cases with resistance-conferring mutations.

Copper 64-labeled daratumumab as a PET/CT imaging tracer for multiple myeloma

As a growing number of patients with multiple myeloma (MM) respond to upfront therapies while eventually relapsing in a time frame that is often unpredictable, attention has increasingly focused on developing novel diagnostic criteria to also account for disease dissemination. Positron emission tomography/computed tomography (PET/CT) is often used as a noninvasive monitoring strategy to assess cancer cell dissemination, but because the uptake of the currently used radiotracer 18fluorodeoxyglucose (¹⁸F-FDG) is a function of the metabolic activity of both malignant and nonmalignant cells, the results frequently lack sufficient specificity. Radiolabeled antibodies targeting MM tissue may detect disease irrespective of cell metabolism. Hence, we conjugated the clinically significant CD38-directed human antibody daratumumab (Darzalex [Dara]) to the DOTA chelator and labeled it with the positron-emitting radionuclide copper 64 (⁶⁴Cu; ⁶⁴Cu-DOTA-Dara). Here, we show that ⁶⁴Cu-DOTA-Dara can efficiently bind CD38 on the surface of MM cells and was mainly detected in the bones associated with tumor in a MM murine model. We also show that PET/CT based on ⁶⁴Cu-DOTA-Dara displays a higher resolution and specificity to detect MM cell dissemination than does ¹⁸F-FDG PET/CT and was even more sensitive than were bioluminescence signals. We therefore have supporting evidence for using ⁶⁴Cu-DOTA-Dara as a novel imaging agent for MM.

How I treat myeloma with new agents

At present, multiple classes of agents with distinct mechanisms of action are available for the treatment of patients with multiple myeloma (MM), including alkylators, steroids, immunomodulatory agents (IMiDs), proteasome inhibitors (PIs), histone deacetylase inhibitors (DACIs), and monoclonal antibodies (mAbs). Over the last 5 years, several new agents, such as the third-generation IMiD pomalidomide, the second-generation PIs carfilzomib and ixazomib, the DACI panobinostat, and 2 mAbs, elotuzumab and daratumumab, have been approved, incorporated into clinical guidelines, and have transformed our approach to the treatment of patients. These agents may be part of doublet or triplet combinations, or incorporated into intensive strategies with autologous stem cell transplantation. In this review, I discuss the different treatment options available today for the treatment of MM in frontline and relapse settings.

Pomalidomide in the treatment of multiple myeloma: design, development and place in therapy

Multiple myeloma is a very heterogeneous disease with variable survival. Despite recent progress and the widespread use of new agents, patients with relapsed and refractory disease have a poor outcome. Immunomodulatory drugs play a key role in both the front-line and the relapsed/refractory setting. The combination of pomalidomide (POM) and dexamethasone is safe and effective in relapsed and refractory patients, even in those with high-risk cytogenetic features. Furthermore, it can be used in most patients without the need to adjust according to the degree of renal failure. In order to further improve the results, POM-based triplet therapies are currently used. This article highlights the most relevant issues of POM and POM-based combinations in the relapsed/refractory multiple myeloma setting, from a pharmacological and clinical point of view.

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.

Positive transcription elongation factor b (P-TEFb) is a therapeutic target in human multiple myeloma

The role of the positive RNA Pol II regulator, P-TEFb (positive transcription elongation factor b), in maintenance of the anti-apoptotic protein Mcl-1 and bortezomib (btz) resistance was investigated in human multiple myeloma (MM) cells. Mcl-1 was up-regulated in all MM lines tested, including bortezomib-resistant lines, human MM xenograft mouse models, and primary CD138⁺ MM cells. Mcl-1 over-expression significantly reduced bortezomib lethality, indicating a functional role for Mcl-1 in bortezomib resistance. MM cell lines, primary MM specimens, and murine xenografts exhibited constitutive P-TEFb activation, manifested by high CTD (carboxy-terminal domain) S2 phosphorylation, associated with a) P-TEFb subunit up-regulation i.e., CDK9 (42 and 55 kDa isoforms) and cyclin T1; and b) marked CDK9 (42 kDa) T186 phosphorylation. In marked contrast, normal hematopoietic cells failed to exhibit up-regulation of p-CTD, CDK9, cyclin T1, or Mcl-1. CDK9 or cyclin T1 shRNA knock-down dramatically inhibited CTD S2 phosphorylation and down-regulated Mcl-1. Moreover, CRISPR-Cas CDK9 knock-out triggered apoptosis in MM cells and dramatically diminished cell growth. Pan-CDK e.g., dinaciclib or alvocidib and selective CDK9 inhibitors (CDK9i) recapitulated the effects of genetic P-TEFb disruption. CDK9 shRNA or CDK9 inhibitors significantly potentiated the susceptibility of MM cells, including bortezomib-resistant cells, to proteasome inhibitors. Analogously, CDK9 or cyclin T1 knock-down or CDK9 inhibitors markedly increased BH3-mimetic lethality in bortezomib-resistant cells. Finally, pan-CDK inhibition reduced human drug-naïve or bortezomib-resistant CD138⁺ cells and restored bone marrow architecture in vivo. Collectively, these findings implicate constitutive P-TEFb activation in high Mcl-1 maintenance in MM, and validate targeting the P-TEFb complex to circumvent bortezomib-resistance.

In Vitro Metabolism of Oprozomib, an Oral Proteasome Inhibitor: Role of Epoxide Hydrolases and Cytochrome P450s

Oprozomib is an oral proteasome inhibitor currently under investigation in patients with hematologic malignancies or solid tumors. Oprozomib elicits potent pharmacological actions by forming a covalent bond with the active site N-terminal threonine of the 20S proteasome. Oprozomib has a short half-life across preclinical species and in patients due to systemic clearance via metabolism. Potential for drug-drug interactions (DDIs) could alter the exposure of this potent therapeutic; therefore, a thorough investigation of pathways responsible for metabolism is required. In the present study, the major drug-metabolizing enzyme responsible for oprozomib metabolism was identified in vitro. A diol of oprozomib was found to be the predominant metabolite in human hepatocytes, which formed via direct epoxide hydrolysis. Using recombinant epoxide hydrolases (EHs) and selective EH inhibitors in liver microsomes, microsomal EH (mEH) but not soluble EH (sEH) was found to be responsible for oprozomib diol formation. Coincubation with 2-nonylsulfanyl-propionamide, a selective mEH inhibitor, resulted in a significant decrease in oprozomib disappearance (>80%) with concurrent complete blockage of diol formation in human hepatocytes. On the contrary, a selective sEH inhibitor did not affect oprozomib metabolism. Pretreatment of hepatocytes with the pan-cytochrome P450 (P450) inhibitor 1-aminobenzotriazole resulted in a modest reduction (∼20%) of oprozomib metabolism. These findings indicated that mEH plays a predominant role in oprozomib metabolism. Further studies may be warranted to determine whether drugs that are mEH inhibitors cause clinically significant DDIs with oprozomib. On the other hand, pharmacokinetics of oprozomib is unlikely to be affected by coadministered P450 and sEH inhibitors and/or inducers.

The therapeutic potential of cell cycle targeting in multiple myeloma

Proper cell cycle progression through the interphase and mitosis is regulated by coordinated activation of important cell cycle proteins (including cyclin-dependent kinases and mitotic kinases) and several checkpoint pathways. Aberrant activity of these cell cycle proteins and checkpoint pathways results in deregulation of cell cycle progression, which is one of the key hallmarks of cancer. Consequently, intensive research on targeting these cell cycle regulatory proteins identified several candidate small molecule inhibitors that are able to induce cell cycle arrest and even apoptosis in cancer cells. Importantly, several of these cell cycle regulatory proteins have also been proposed as therapeutic targets in the plasma cell malignancy multiple myeloma (MM). Despite the enormous progress in the treatment of MM the past 5 years, MM still remains most often incurable due to the development of drug resistance. Deregulated expression of the cyclins D is observed in virtually all myeloma patients, emphasizing the potential therapeutic interest of cyclin-dependent kinase inhibitors in MM. Furthermore, other targets have also been identified in MM, such as microtubules, kinesin motor proteins, aurora kinases, polo-like kinases and the anaphase promoting complex/cyclosome. This review will provide an overview of the cell cycle proteins and checkpoint pathways deregulated in MM and discuss the therapeutic potential of targeting proteins or protein complexes involved in cell cycle control in MM.

High-dose gemcitabine, busulfan, and melphalan for autologous stem-cell transplant in patients with relapsed or refractory myeloma: a phase 2 trial and matched-pair comparison with melphalan

BACKGROUND

High-dose melphalan is of limited benefit as autologous stem-cell transplantation (ASCT) regimen for relapsed/refractory myeloma. Its poor results in this setting prompted us to study a new high-dose combination of infusional gemcitabine/busulfan/melphalan (Gem/Bu/Mel).

METHODS

We conducted a phase 2 trial of Gem/Bu/Mel in patients with primary refractory or relapsed disease after bortezomib and/or an immunomodulatory drug (IMiD), or receiving a salvage ASCT. Gemcitabine (1,875 mg/m² over 3 hours × 2 days) was followed by busulfan (target AUC 4,000/day × 4 days) and melphalan (60 mg/m²/day × 2 days). The primary endpoint of this trial was to determine the stringent complete remission (sCR) rate of Gem/Bu/Mel in this population. We then retrospectively compared the study patients with all other concurrent patients eligible for this trial who, instead, received melphalan at 200 mg/m² IV at our center. For survival outcomes, we used a statistical algorithm to select a subset from the control cohort that matched with the Gem/Bu/Mel patients by gender, age, disease status, double refractoriness to proteasome inhibitors/IMIDs, duration from diagnosis to transplant and cytogenetic risk, in a 1–2:1 ratio. All analyses are per protocol. This is the final analysis of the clinical trial. Trial registered at NCI.gov (NCT01237951).

FINDINGS

We enrolled 74 patients on the Gem/Bu/Mel trial, median age 58 (interquartile range [IQR], 11), median 2 prior therapy lines (IQR, 3), 38 high-risk cytogenetics, 17 unresponsive to all prior treatments, and 33 receiving a salvage ASCT. Toxicities of Gem/Bu/Mel included grade 3 mucositis (N=12), grade 3 dermatitis (N=5), grade 3 transaminase elevation (N=7), grade 3 diarrhea (N=2), grade 5 sudden death (N=1) and grade 5 sepsis (N=2). The study patients and the 184 concurrent controls received similar post-ASCT maintenance. Gem/Bu/Mel resulted in more sCR (24.6% v 12.6%, P=0.040), similar overall responses (73.8% v 74.1%, P=0.77) and similar transplant-related mortality (4.0% v 3.8%, P=0.90). The median follow-up times for the Gem/Bu/Mel patients and the matched subset (N=111) were 36 months (IQR, 15.2) and 34 months (IQR, 27), respectively. Gem/Bu/Mel resulted in improved progression-free survival (median 15.1 v 9.3 months, P=0.0030; hazard ratio=0.60; P=0.021) and overall survival (median 37.5 v 23 months, P=0.0092; hazard ratio=0.65, P=0.0087).

INTERPRETATION

Gem/Bu/Mel is a safe and active ASCT regimen for refractory/relapsed myeloma, with better outcomes than a concurrent matched cohort receiving melphalan.

Funding

Supported by a grant from Otsuka Pharmaceutical Development & Commercialization Inc. and NCI Grant P30 CA016672.

Identification of precision treatment strategies for relapsed/refractory multiple myeloma by functional drug sensitivity testing

Novel agents have increased survival of multiple myeloma (MM) patients, however high-risk and relapsed/refractory patients remain challenging to treat and their outcome is poor. To identify novel therapies and aid treatment selection for MM, we assessed the ex vivo sensitivity of 50 MM patient samples to 308 approved and investigational drugs. With the results we i) classified patients based on their ex vivo drug response profile; ii) identified and matched potential drug candidates to recurrent cytogenetic alterations; and iii) correlated ex vivo drug sensitivity to patient outcome. Based on their drug sensitivity profiles, MM patients were stratified into four distinct subgroups with varied survival outcomes. Patients with progressive disease and poor survival clustered in a drug response group exhibiting high sensitivity to signal transduction inhibitors. Del(17p) positive samples were resistant to most drugs tested with the exception of histone deacetylase and BCL2 inhibitors. Samples positive for t(4;14) were highly sensitive to immunomodulatory drugs, proteasome inhibitors and several targeted drugs. Three patients treated based on the ex vivo results showed good response to the selected treatments. Our results demonstrate that ex vivo drug testing may potentially be applied to optimize treatment selection and achieve therapeutic benefit for relapsed/refractory MM.

An Ex Vivo Platform for the Prediction of Clinical Response in Multiple Myeloma

Multiple myeloma remains treatable but incurable. Despite a growing armamentarium of effective agents, choice of therapy, especially in relapse, still relies almost exclusively on clinical acumen. We have developed a system, Ex vivo Mathematical Myeloma Advisor (EMMA), consisting of patient-specific mathematical models parameterized by an ex vivo assay that reverse engineers the intensity and heterogeneity of chemosensitivity of primary cells from multiple myeloma patients, allowing us to predict clinical response to up to 31 drugs within 5 days after bone marrow biopsy. From a cohort of 52 multiple myeloma patients, EMMA correctly classified 96% as responders/nonresponders and correctly classified 79% according to International Myeloma Working Group stratification of level of response. We also observed a significant correlation between predicted and actual tumor burden measurements (Pearson r = 0.5658, P < 0.0001). Preliminary estimates indicate that, among the patients enrolled in this study, 60% were treated with at least one ineffective agent from their therapy combination regimen, whereas 30% would have responded better if treated with another available drug or combination. Two in silico clinical trials with experimental agents ricolinostat and venetoclax, in a cohort of 19 multiple myeloma patient samples, yielded consistent results with recent phase I/II trials, suggesting that EMMA is a feasible platform for estimating clinical efficacy of drugs and inclusion criteria screening. This unique platform, specifically designed to predict therapeutic response in multiple myeloma patients within a clinically actionable time frame, has shown high predictive accuracy in patients treated with combinations of different classes of drugs. The accuracy, reproducibility, short turnaround time, and high-throughput potential of this platform demonstrate EMMA's promise as a decision support system for therapeutic management of multiple myeloma. Cancer Res; 77(12); 3336-51. ©2017 AACR.

Novel Proteasome Inhibitors and Histone Deacetylase Inhibitors: Progress in Myeloma Therapeutics

The unfolded protein response is responsible for the detection of misfolded proteins and the coordination of their disposal and is necessary to maintain the cellular homoeostasis. Multiple myeloma cells secrete large amounts of immunoglobulins, proteins that need to be correctly folded by the chaperone system. If this process fails, the misfolded proteins have to be eliminated by the two main garbage-disposal systems of the cell: proteasome and aggresome. The blockade of either of these systems will result in accumulation of immunoglobulins and other toxic proteins in the cytoplasm and cell death. The simultaneous inhibition of the proteasome, by proteasome inhibitors (PIs) and the aggresome, by histone deacetylase inhibitors (HDACi) results in a synergistic increase in cytotoxicity in myeloma cell lines. This review provides an overview of mechanisms of action of second-generation PIs and HDACi in multiple myeloma (MM), the clinical results currently observed with these agents and assesses the potential therapeutic impact of the different agents in the two classes. The second-generation PIs offer benefits in terms of increased efficacy, reduced neurotoxicity as off-target effect and may overcome resistance to bortezomib because of their different chemical structure, mechanism of action and biological properties. HDACi with anti-myeloma activity in clinical development discussed in this review include vorinostat, panobinostat and selective HDAC6 inhibitor, ricolinostat.