Genome-wide studies in multiple myeloma identify XPO1/CRM1 as a critical target validated using the selective nuclear export inhibitor KPT-276

Michael Acceptors as Anti-Cancer Compounds: Coincidence or Causality?

Michael acceptors represent a class of compounds with potential anti-cancer properties. They act by binding to nucleophilic sites in biological molecules, thereby disrupting cancer cell function and inducing cell death. This mode of action, as well as their ability to be modified and targeted, makes them a promising avenue for advancing cancer therapy. We are investigating the molecular mechanisms underlying Michael acceptors and their interactions with cancer cells, in particular their ability to interfere with cellular processes and induce apoptosis. The anti-cancer properties of Michael acceptors are not accidental but are due to their chemical structure and reactivity. The electrophilic nature of these compounds allows them to selectively target nucleophilic residues on disease-associated proteins, resulting in significant therapeutic benefits and minimal toxicity in various diseases. This opens up new perspectives for the development of more effective and precise cancer drugs. Nevertheless, further studies are essential to fully understand the impact of our discoveries and translate them into clinical practice.

Therapeutic progress in relapsed/refractory multiple myeloma

Improvement in the therapeutics for multiple myeloma (MM) has been continuously developed owing to the application of novel drugs and technologies in the last 20 years. The standard first-line therapy for MM consists of a three-drug induction regimen based on immunomodulatory drugs and proteasome inhibitors combined with autologous stem cell transplantation. However, MM remains incurable; therefore, therapies for relapsed/refractory MM (RRMM) are emerging and evolving rapidly. This study aimed to summarize and review the results of RRMM trials over the past 5 years to provide a holistic overview and insights for practitioners in related fields and to provide additional ideas for clinical trialists. This study shows that daratumumab and isatuximab continue to significantly advance as treatment options. Additionally, novel antibody drugs, such as elotuzumab and selinexor, as well as bispecific antibodies, teclistamab and talquetamab, are currently undergoing clinical research with promising outcomes. However, chimeric antigen receptor-T cell therapy targeting B-cell maturation antigen remains the optimal approach for MM treatment.

Beyond oncology: Selinexor's journey into anti-inflammatory treatment and long-term management

Selinexor, a selective inhibitor of nuclear export (SINE), is gaining recognition beyond oncology for its potential in anti-inflammatory therapy. This review elucidates Selinexor's dual action, highlighting its anti-tumor efficacy in various cancers including hematologic malignancies and solid tumors, and its promising anti-inflammatory effects. In cancer treatment, Selinexor has demonstrated benefits as monotherapy and in combination with other therapeutics, particularly in drug-resistant cases. Its role in enhancing the effectiveness of bone marrow transplants has also been noted. Importantly, the drug's impact on key inflammatory pathways provides a new avenue for the management of conditions like sepsis, viral infections including COVID-19, and chronic inflammatory diseases such as Duchenne Muscular Dystrophy and Parkinson's Disease. The review emphasizes the criticality of managing Selinexor's side effects through diligent dose optimization and patient monitoring. Given the complexities of its broader applications, extensive research is called upon to validate Selinexor's long-term safety and effectiveness, with a keen focus on its integration into clinical practice for a diverse spectrum of disorders.

Treatment of multiple myeloma with selinexor: a review

Over the last 20 years, breakthroughs in accessible therapies for the treatment of multiple myeloma (MM) have been made. Nevertheless, patients with MM resistant to immunomodulatory drugs, proteasome inhibitors, and anti-CD38 monoclonal antibodies have a very poor outcome. Therefore, it is necessary to explore new drugs for the treatment of MM. This review summarizes the mechanism of action of selinexor, relevant primary clinical trials, and recent developments in both patients with relapsed/refractory myeloma and patients with newly diagnosed myeloma. Selinexor may be useful for the treatment of refractory MM.

Therapeutic targeting of nuclear export and import receptors in cancer and their potential in combination chemotherapy

Systemic modalities are crucial in the management of disseminated malignancies and liquid tumours. However, patient responses and tolerability to treatment are generally poor and those that enter remission often return with refractory disease. Combination therapies provide a methodology to overcome chemoresistance mechanisms and address dose-limiting toxicities. A deeper understanding of tumorigenic processes at the molecular level has brought a targeted therapy approach to the forefront of cancer research, and novel cancer biomarkers are being identified at a rapid rate, with some showing potential therapeutic benefits. The Karyopherin superfamily of proteins is soluble receptors that mediate nucleocytoplasmic shuttling of proteins and RNAs, and recently, nuclear transport receptors have been recognized as novel anticancer targets. Inhibitors against nuclear export have been approved for clinical use against certain cancer types, whereas inhibitors against nuclear import are in preclinical stages of investigation. Mechanistically, targeting nucleocytoplasmic shuttling has shown to abrogate oncogenic signalling and restore tumour suppressor functions through nuclear sequestration of relevant proteins and mRNAs. Hence, nuclear transport inhibitors display broad spectrum anticancer activity and harbour potential to engage in synergistic interactions with a wide array of cytotoxic agents and other targeted agents. This review is focussed on the most researched nuclear transport receptors in the context of cancer, XPO1 and KPNB1, and highlights how inhibitors targeting these receptors can enhance the therapeutic efficacy of standard of care therapies and novel targeted agents in a combination therapy approach. Furthermore, an updated review on the therapeutic targeting of lesser characterized karyopherin proteins is provided and resistance to clinically approved nuclear export inhibitors is discussed.

A comparison study of pathological features and drug efficacy between Drosophila models of C9orf72 ALS/FTD

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease with a complex genetic basis, presenting both in familial and sporadic forms. The hexanucleotide (G4C2) repeat expansion in the C9orf72 gene, which triggers distinct pathogenic mechanisms, has been identified as a major contributor to familial and sporadic Amyotrophic lateral sclerosis cases. Animal models have proven pivotal in understanding these mechanisms; however, discrepancies between models due to variable transgene sequence, expression levels, and toxicity profiles complicate the translation of findings. Herein, we provide a systematic comparison of 7 publicly available Drosophila transgenes modeling the G4C2 expansion under uniform conditions, evaluating variations in their toxicity profiles. Further, we tested 3 previously characterized disease-modifying drugs in selected lines to uncover discrepancies among the tested strains. Our study not only deepens our understanding of the C9orf72 G4C2 mutations but also presents a framework for comparing constructs with minute structural differences. This work may be used to inform experimental designs to better model disease mechanisms and help guide the development of targeted interventions for neurodegenerative diseases, thus bridging the gap between model-based research and therapeutic application.

Selinexor: Targeting a novel pathway in multiple myeloma

Selinexor is an orally bioavailable selective inhibitor of nuclear export compound that inhibits exportin-1 (XPO1), a novel therapeutic target that is overexpressed in multiple myeloma (MM) and is responsible for the transport of ∼220 nuclear proteins to the cytoplasm, including tumour suppressor proteins. Inhibition of this process has demonstrated substantial antimyeloma activity in preclinical studies, both alone and in combination with established MM therapeutics. Based on a clinical trial programme encompassing multiple combination regimens, selinexor-based therapy has been approved for the treatment of relapsed/refractory MM (RRMM), with selinexor-dexamethasone approved in the later-relapse setting for penta-refractory patients and selinexor-bortezomib-dexamethasone approved for patients who have received ≥1 prior therapy. Here, we provide a comprehensive review of the clinical data on selinexor-based regimens, including recent updates from the 2022 American Society of Hematology annual meeting, and summarise ongoing studies of this novel targeted agent in newly diagnosed MM and RRMM.

A general method for quantitative fractionation of mammalian cells

Subcellular fractionation in combination with mass spectrometry-based proteomics is a powerful tool to study localization of key proteins in health and disease. Here we offered a reliable and rapid method for mammalian cell fractionation, tuned for such proteomic analyses. This method proves readily applicable to different cell lines in which all the cellular contents are accounted for, while maintaining nuclear and nuclear envelope integrity. We demonstrated the method's utility by quantifying the effects of a nuclear export inhibitor on nucleoplasmic and cytoplasmic proteomes.

Inhibition of XPO1 impairs cholangiocarcinoma cell proliferation by triggering p53 intranuclear accumulation

BACKGROUND

XPO1 mediates the nuclear export of several proteins, mainly tumor suppressors. KPT-330 (Selinexor) is a selective inhibitor of XPO1 that has demonstrated good therapeutic effects in hematologic cancers.

METHODS

We used TCGA and GTEx pan-cancer database to evaluate XPO1 mRNA expression in various tumors. Cell proliferation assay and colony formation assay were used to analyze the in vitro antitumor effects of XPO1 inhibitor KPT-330. Western blot was performed to explore the specific mechanisms.

RESULTS

We found that XPO1 was highly expressed across a range of cancers and associated with poor prognosis in hepatobiliary and pancreatic tumors. We revealed that the XPO1 inhibitor KPT-330 triggered the nuclear accumulation of the p53 protein and significantly disrupted the proliferation of cholangiocarcinoma cells. Mechanistically, the XPO1 inhibitor, KPT-330, reduced BIRC6 expression by inhibiting the PI3K/AKT pathway to decrease p53 degradation and improve its stability.

CONCLUSION

Therefore, XPO1 may be a potential therapeutic target in cholangiocarcinoma, mediated by its effects on KPT-330.

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.

Oncogenic RAS commandeers amino acid sensing machinery to aberrantly activate mTORC1 in multiple myeloma

Oncogenic RAS mutations are common in multiple myeloma (MM), an incurable malignancy of plasma cells. However, the mechanisms of pathogenic RAS signaling in this disease remain enigmatic and difficult to inhibit therapeutically. We employ an unbiased proteogenomic approach to dissect RAS signaling in MM. We discover that mutant isoforms of RAS organize a signaling complex with the amino acid transporter, SLC3A2, and MTOR on endolysosomes, which directly activates mTORC1 by co-opting amino acid sensing pathways. MM tumors with high expression of mTORC1-dependent genes are more aggressive and enriched in RAS mutations, and we detect interactions between RAS and MTOR in MM patient tumors harboring mutant RAS isoforms. Inhibition of RAS-dependent mTORC1 activity synergizes with MEK and ERK inhibitors to quench pathogenic RAS signaling in MM cells. This study redefines the RAS pathway in MM and provides a mechanistic and rational basis to target this mode of RAS signaling.

RAS mutations are commonly found in multiple myeloma (MM). Here, the authors show that oncogenic RAS mutations activate mTORC1 signalling in MM and combining mTORC1 and MEK/ERK inhibitors synergize to improve survival in preclinical models.

Multiple Myeloma Therapy: Emerging Trends and Challenges

Multiple myeloma (MM) is a complex hematologic malignancy characterized by the uncontrolled proliferation of clonal plasma cells in the bone marrow that secrete large amounts of immunoglobulins and other non-functional proteins. Despite decades of progress and several landmark therapeutic advancements, MM remains incurable in most cases. Standard of care frontline therapies have limited durable efficacy, with the majority of patients eventually relapsing, either early or later. Induced drug resistance via up-modulations of signaling cascades that circumvent the effect of drugs and the emergence of genetically heterogeneous sub-clones are the major causes of the relapsed-refractory state of MM. Cytopenias from cumulative treatment toxicity and disease refractoriness limit therapeutic options, hence creating an urgent need for innovative approaches effective against highly heterogeneous myeloma cell populations. Here, we present a comprehensive overview of the current and future treatment paradigm of MM, and highlight the gaps in therapeutic translations of recent advances in targeted therapy and immunotherapy. We also discuss the therapeutic potential of emerging preclinical research in multiple myeloma.

Effect of Prior Therapy and Disease Refractoriness on the Efficacy and Safety of Oral Selinexor in Patients with Diffuse Large B-cell Lymphoma (DLBCL): A Post-hoc Analysis of the SADAL Study

BACKGROUND

Despite a number of treatment options, patients with diffuse large B-cell lymphoma (DLBCL) whose disease has become refractory to treatment have a poor prognosis. Selinexor is a novel, oral drug that is approved to treat patients with relapsed/refractory DLBCL. In this post hoc analysis of the SADAL study, a multinational, open-label study, we evaluated subpopulations to determine if response to single agent selinexor is impacted by number of lines of prior treatment, autologous stem cell transplant (ASCT), response to first and most recent therapies, and time to progressive disease.

PATIENTS

Patients (n = 134) with DLBCL after 2-5 prior therapies were enrolled in SADAL and received 60mg selinexor twice weekly.

RESULTS

The median overall survival was 9.0 months and median progression free survival was 2.6 months. Patients who had the best overall response rate (ORR) and disease control rate were those who had prior ASCT (42.5% and 50.0%) or responded to last line of therapy (35.9% and 43.5%). Patients with primary refractory DLBCL also showed responses (ORR 21.8%). Adverse events between subgroups were similar to the overall study population, the most common being thrombocytopenia (29.1%), fatigue (7.5%), and nausea (6.0%).

CONCLUSION

Regardless of prior therapy and disease refractory status, selinexor treatment demonstrated results consistent with its novel mechanism of action and lack of cross-resistance. Thus, single agent oral selinexor can induce deep, durable, and tolerable responses in patients with DLBCL who have recurrent disease after several chemoimmunotherapy combination regimens.

Identification of Novel Covalent XPO1 Inhibitors Based on a Hybrid Virtual Screening Strategy

Nuclear export protein 1 (XPO1), a member of the nuclear export protein-p (Karyopherin-P) superfamily, regulates the transport of “cargo” proteins. To facilitate this important process, which is essential for cellular homeostasis, XPO1 must first recognize and bind the cargo proteins. To inhibit this process, small molecule inhibitors have been designed that inhibit XPO1 activity through covalent binding. However, the scaffolds for these inhibitors are very limited. While virtual screening may be used to expand the diversity of the XPO1 inhibitor skeleton, enormous computational resources would be required to accomplish this using traditional screening methods. In the present study, we report the development of a hybrid virtual screening workflow and its application in XPO1 covalent inhibitor screening. After screening, several promising XPO1 covalent molecules were obtained. Of these, compound 8 performed well in both tumor cell proliferation assays and a nuclear export inhibition assay. In addition, molecular dynamics simulations were performed to provide information on the mode of interaction of compound 8 with XPO1. This research has identified a promising new scaffold for XPO1 inhibitors, and it demonstrates an effective and resource-saving workflow for identifying new covalent inhibitors.

Selinexor plus low-dose dexamethasone in Chinese patients with relapsed/refractory multiple myeloma previously treated with an immunomodulatory agent and a proteasome inhibitor (MARCH): a phase II, single-arm study

BACKGROUND

Selinexor 80 mg combined with low-dose dexamethasone (Sd) demonstrated significant clinical benefit in patients with relapsed/refractory multiple myeloma (RRMM) who had disease refractory to a proteasome inhibitor (PI), an immunomodulator (IMiD), and an anti-CD38 monoclonal antibody based on a global phase II STORM study. The present study, MARCH, addresses China regulatory needs to further validate the data from STORM in Chinese patients with RRMM.

METHODS

The MARCH study was conducted at 17 sites in China, where eligible Chinese RRMM patients who had disease refractory to PI and IMiD were enrolled. Selinexor 80 mg combined with dexamethasone 20 mg was administered orally on day 1 and day 3 of each week in 4-week cycles. The primary endpoint was the overall response rate (ORR) per an independent review committee, with the null hypothesis of ≤15%. Patients who received at least 1 dose of study treatment were included in the safety population. The pharmacokinetic (PK) profile was characterized by parameter and ethnicity sensitivity analyses.

RESULTS

A total of 82 patients with RRMM were enrolled in the study, with a median age of 60 years. Of the 82 patients, 55 patients (67.1%) had high-risk cytogenetic abnormalities, defined as one or more of del 17p13, t(4;14), t(14;16), or 1q amplification identified by fluorescence in situ hybridization (FISH); 18 patients (22.0%) had abnormal renal function. Enrolled patients were heavily pre-treated with a median prior regimen number of 5. All 82 patients (100%) were refractory to both PI and IMiD, including 20 patients (24.4%) categorized as triple-class refractory population (refractory to PI, IMiD, and daratumumab). Ten patients (12.2%) had undergone CAR-T therapy. ORR was 29.3% (95% CI 19.7, 40.4) with a median DOR of 4.7 months. The median PFS and OS were 3.7 and 13.2 months, respectively. ORR was 25.0% (95% CI 8.7, 49.1) in the triple-class refractory population. Efficacy was consistent across various subgroups. The most frequent grade 3/4 adverse events (AEs) included anemia (57.3%), thrombocytopenia (51.2%), lymphopenia (42.7%), neutropenia (40.2%), hyponatremia (29.3%), and lung infection (26.8%). Serious AEs were reported in 54.9% of patients. No significant drug accumulation was shown following multiple administrations. No human PK ethnicity difference was identified between Chinese and western patients.

CONCLUSIONS

With an encouraging ORR, the MARCH study has demonstrated that selinexor combined with low-dose dexamethasone (Sd) delivers meaningful clinical benefit to Chinese patients with RRMM, including triple-class refractory patients. AEs were expected and manageable with supportive care and dose modification.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03944057 (May 09, 2019); Chinadrugtrials.org.cn , CTR20190858 (June 05, 2019).

New and emerging pharmacotherapies for management of multiple myeloma

DISCLAIMER

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

The pharmacology, efficacy, safety, and dosing/administration of new and emerging therapies for the treatment of multiple myeloma are summarized.

SUMMARY

There have been significant advancements in the treatment of multiple myeloma in recent years, with an expansion of available drug therapies. Newer therapies for multiple myeloma include the anti-CD38 monoclonal antibodies daratumumab and isatuximab, the exportin 1 inhibitor selinexor, the anti-B-cell maturation antigen (BCMA) antibody-drug conjugate belantamab mafodotin, and the chimeric antigen receptor (CAR) T-cell therapy idecabtagene vicleucel. These agents have unique toxicity profiles, specific monitoring parameters, and operational considerations that clinicians treating multiple myeloma should be aware of. There is likely to be continued rapid expansion of new agents for patients with multiple myeloma, as there are many novel investigational agents in the drug development pipeline, such as bispecific antibodies and additional CAR T-cell therapies.

CONCLUSION

Several therapeutic agents have been recently approved by the Food and Drug Administration for the treatment of multiple myeloma. There are many novel agents in the pipeline, including bispecific antibodies and CAR T-cell therapies that have the potential to continue to change the treatment landscape of multiple myeloma.

Selective inhibition of nuclear export: a promising approach in the shifting treatment paradigms for hematological neoplasms

Novel targeted therapeutics alone or in rational combinations are likely to dominate the future management of various hematological neoplasms. However, the challenges currently faced are the molecular heterogeneity in driver lesions and genetic plasticity leading to multiple resistance pathways. Thus, progress has overall been gradual. For example, despite the advent of targeted agents against actionable drivers like FLT3 in acute myeloid leukemia (AML), the prognosis remains suboptimal in newly diagnosed and dismal in the relapsed/refractory (R/R) setting, due to other molecular abnormalities contributing to inherent and acquired treatment resistance. Nuclear export inhibitors are of keen interest because they can inhibit several active tumorigenic processes simultaneously and also synergize with other targeted drugs and chemotherapy. XPO1 (or CRM1, chromosome maintenance region 1) is one of the most studied exportins involved in transporting critical cargoes, including tumor suppressor proteins like p27, p53, and RB1. Apart from the TSP cargo transport and its role in drug resistance, XPO1 inhibition results in retention of master transcription factors essential for cell differentiation, cell survival, and autophagy, rendering cells more susceptible to the effects of other antineoplastic agents, including targeted therapies. This review will dissect the role of XPO1 inhibition in hematological neoplasms, focusing on mechanistic insights gleaned mainly from work with SINE compounds. Future potential combinatorial strategies will be discussed.

Selinexor, Bortezomib and Dexamethasone: An Effective Salvage Regimen for Heavily Pretreated Myeloma Patients

Purpose

Patients and Methods

Results

Conclusion

Targeting Nuclear Export Proteins in Multiple Myeloma Therapy

Nuclear export proteins such as exportin-1 (XPO1) transport tumor-suppressor proteins and other growth-regulatory proteins from the nucleus to the cytoplasm. Overexpression of XPO1 has been observed in several cancers and correlates with shorter event-free and overall survival in multiple myeloma. Selinexor was developed as an oral first-in-class selective inhibitor of nuclear export (SINE) that inhibits XPO1. Preclinical studies in tumor cell lines and mouse models have demonstrated the efficacy of selinexor both as a single agent and in various combinations with known active antimyeloma agents. Results from the pivotal phase II STORM trial led to the US FDA approval of selinexor with dexamethasone in penta-refractory myeloma. Because of the feasibility of combining selinexor with other active antimyeloma agents, the multiarm STOMP trial was initiated and is ongoing, with impressive response rates reported in some of the combination arms thus far. The registrational phase III BOSTON trial demonstrated the superiority of selinexor in combination with bortezomib and dexamethasone as compared with bortezomib and dexamethasone in patients with relapsed refractory multiple myeloma (RRMM) who have received one to three prior anti-MM regimens. The toxicity profile of selinexor is well established and predictable and may be significant unless managed aggressively and preemptively. The most common side effects are thrombocytopenia, anemia, neutropenia, fatigue, nausea, anorexia, and weight loss. Hyponatremia and cataracts seem to be class effects. Other SINE compounds are now being studied in efforts to discover agents that will potentially be better tolerated. Eltanexor is an investigational SINE compound that has shown a more positive toxicity profile in preclinical studies, with reduced central nervous system penetration and gastrointestinal side effects, and is now undergoing clinical investigation. These and other trials will further clarify the role of these innovative agents in the therapeutic advancement of RRMM.

The Role of Belantamab Mafodotin, Selinexor, and Melflufen in Multiple Myeloma

PURPOSE OF REVIEW

Multiple myeloma (MM) is a hematologic malignancy of plasma cells that remains incurable with currently available therapies including proteosome inhibitors, immunomodulators, monoclonal antibodies, corticosteroids, and alkylators, in addition to autologous stem cell transplantation in patients who are eligible. Novel therapeutics are therefore required to improve patient outcomes. The goal of this paper is to review the role of three new agents in the MM treatment landscape: belantamab mafodotin, selinexor, and melflufen.

RECENT FINDINGS

All three agents have demonstrated clinical activity in patients with MM. Belamaf is the first FDA-approved anti-BCMA targeted agent, showing single-agent response rates of 60% and higher response rates of 48-100% in combinations. The majority of patients treated with belamaf experience corneal toxicity which remains the main challenge with its use; however, fortunately, the vast majority of patients recover. Selinexor is also FDA approved for the treatment of relapsed MM, with single-agent response rates of 26% and combination rates of 48-65%. Gastrointestinal side effects are common with selinexor use, with roughly 65% of patients experiencing nausea, 50% anorexia, 35% vomiting, and 42% diarrhea, the majority of which are grades 1-2. Both agents have a plethora of ongoing clinical trials with data forthcoming on various combinations with standard backbone agents as well as additional novel treatments. While melflufen showed promising initial data showing single-agent response rates of about 30%, inferior survival outcomes in patients previously treated with ASCT in the phase 3 OCEAN study lead to early termination of the trial and subsequent removal from the US market. Belamaf, selinexor, and melflufen are active agents to treat myeloma. Belamaf and selinexor are current options for the treatment of relapsed multiple myeloma with improved response rates and durability when used in triplet combinations. The optimal timing of use and treatment combinations of both agents in the context of additional immunotherapeutics entering the MM landscape requires further study. Many prospective studies are in development and promise to afford further clarity in the near future.

Targeting XPO1-Dependent Nuclear Export in Cancer

Nucleocytoplasmic transport of macromolecules is tightly regulated in eukaryotic cells. XPO1 is a transport factor responsible for the nuclear export of several hundred protein and RNA substrates. Elevated levels of XPO1 and recurrent mutations have been reported in multiple cancers and linked to advanced disease stage and poor survival. In recent years, several novel small-molecule inhibitors of XPO1 were developed and extensively tested in preclinical cancer models and eventually in clinical trials. In this brief review, we summarize the functions of XPO1, its role in cancer, and the latest results of clinical trials of XPO1 inhibitors.

Verdinexor, a Selective Inhibitor of Nuclear Exportin 1, Inhibits the Proliferation and Migration of Esophageal Cancer via XPO1/c-Myc/FOSL1 Axis

Esophageal carcinoma (EC) ranks sixth among cancers in mortality worldwide and effective drugs to reduce EC incidence and mortality are lacking. To explore potential anti-esophageal cancer drugs, we conducted drug screening and discovered that verdinexor, a selective inhibitor of nuclear exportin 1 (XPO1/CRM1), has anti-esophageal cancer effects both in vivo and in vitro. However, the mechanism and role of verdinexor in esophageal cancer remain unknown. In the present study, we observed that verdinexor inhibited the proliferation and migration of EC cells in vitro and suppressed tumor growth in vivo. Additionally, we found that verdinexor induced cleavage of PARP and downregulated XPO1, c-Myc, and FOSL1 expression. RNA-sequence analysis and protein-protein interaction (PPI) analysis revealed that verdinexor regulated the XPO1/c-Myc/FOSL1 axis. The results of immunoprecipitation and proximity ligation assays confirmed that verdinexor disrupted the interaction between XPO1 and c-Myc. Overexpression of c-Myc rescued the inhibition of cell proliferation and cell migration caused by verdinexor. Overexpressed FOSL1 restored the inhibited migration by verdinexor. Taken together, verdinexor inhibited cell proliferation and migration of esophageal cancer via XPO1/c-Myc/FOSL1 axis. Our findings provide a new option for the development of anti-esophageal cancer drugs.

Safety and Efficacy Analysis of Selinexor-Based Treatment in Multiple Myeloma, a Meta-Analysis Based on Prospective Clinical Trials

Background: Selinexor (SEL) is an orally bioavailable, highly-selective, and slowly-reversible small molecule that inhibits Exportin 1. Preclinical studies showed that SEL had synergistic antimyeloma activity with glucocorticoids, proteasome inhibitors (PIs) and immunomodulators. The combination of selinexor and dexamethasone (DEX) has been approved in the United States for patients with penta-refractory multiple myeloma in July 2019. This meta-analysis aimed to investigate the safety and efficacy of selinexor based treatment in Multiple myeloma. Methods: We systematically searched the Medline (PubMed), Embase, Web of Science, Cochrane Central Register of Controlled Trials Library databases and ClinicalTrials.gov. Outcome measures of efficacy included overall response rate (ORR), clinical benefit rate (CBR), stringent complete response rate (sCR), complete response rate (CR), very good partial response (VGPR), partial response rate (PR), minimal response (MR), rate of stable disease (SDR), rate of progressive disease (PDR) and median progression-free survival (mPFS). Safety was evaluated by the incidences of all grade adverse events and Grade≥3 adverse events. The subgroup analysis was conducted to analyze the difference in different combination treatment regimens (SEL + DEX + PIs vs SEL + DEX). Results: We included six studies with 477 patients. The pooled ORR, CBR, sCR, CR, VGPR, PR, MR, SDR, and PDR were 43% (18-67%), 55% (32-78%), 5% (-2-13%), 7% (4-11%), 14% (5-24%), 23% (15-31%), 11% (8-14%), 26% (14-38%) and 14% (4-23%), respectively. SEL + DEX + PIs treatment had higher ORR (54 vs 24%, p = 0.01), CBR (66 vs 37%, p = 0.01), sCR (10 vs 2%, p = 0.0008), and VGPR (23 vs 5%, p < 0.00001) compared to SEL + DEX treatment, and lower PDR (4 vs 23%, p < 0.00001) and SDR (17 vs 37%, p = 0.0006). The pooled incidences of any grade and grade≥3 were 45 and 30% in hematological AEs, and in non-hematological AEs were 40 and 30%, respectively. The most common all grade (68%) and grade≥3 (54%) hematological AE were both thrombocytopenia. Fatigue was the most common all grade (62%) and grade≥3 (16%) non-hematological AE. Compared to SEL + DEX treatment, SEL + DEX + PIs treatment had lower incidences of hyponatremia (39 vs 12%, p < 0.00001), nausea (72 vs 52%, p < 0.00001), vomiting (41 vs 23%, p < 0.0001), and weight loss (42 vs 17%, p = 0.03) in all grade AEs. Meanwhile, SEL + DEX + PIs treatment had lower incidences of anemia (36 vs 16%, p = 0.02), fatigue (20 vs 13%, p = 0.04), hyponatremia (22 vs 5%, p < 0.0001) than SEL + DEX treatment in grade≥3 AEs. Conclusion: Our meta-analysis revealed that selinexor-based regimens could offer reasonable efficacy and tolerable adverse events in patients with multiple myeloma. SEL + DEX + PIs treatments had higher efficacy and lower toxicities than SEL + DEX.

Therapeutic Targeting of Exportin-1 in Childhood Cancer

Overexpression of Exportin-1 (XPO1), a key regulator of nuclear-to-cytoplasmic transport, is associated with inferior patient outcomes across a range of adult malignancies. Targeting XPO1 with selinexor has demonstrated promising results in clinical trials, leading to FDA approval of its use for multiple relapsed/refractory cancers. However, XPO1 biology and selinexor sensitivity in childhood cancer is only recently being explored. In this review, we will focus on the differential biology of childhood and adult cancers as it relates to XPO1 and key cargo proteins. We will further explore the current state of pre-clinical and clinical development of XPO1 inhibitors in childhood cancers. Finally, we will outline potentially promising future therapeutic strategies for, as well as potential challenges to, integrating XPO1 inhibition to improve outcomes for children with cancer.

Once weekly selinexor, carfilzomib and dexamethasone in carfilzomib non-refractory multiple myeloma patients

Background

Proteasome inhibitors (PIs), including carfilzomib, potentiate the activity of selinexor, a novel, first-in-class, oral selective inhibitor of nuclear export (SINE) compound, in preclinical models of multiple myeloma (MM).

Methods

The safety, efficacy, maximum-tolerated dose (MTD) and recommended phase 2 dose (RP2D) of selinexor (80 or 100 mg) + carfilzomib (56 or 70 mg/m²) + dexamethasone (40 mg) (XKd) once weekly (QW) was evaluated in patients with relapsed refractory MM (RRMM) not refractory to carfilzomib.

Results

Thirty-two patients, median prior therapies 4 (range, 1–8), were enrolled. MM was triple-class refractory in 38% of patients and 53% of patients had high-risk cytogenetics del(17p), t(4;14), t(14;16) and/or gain 1q. Common treatment-related adverse events (all/Grade 3) were thrombocytopenia 72%/47% (G3 and G4), nausea 72%/6%, anaemia 53%/19% and fatigue 53%/9%, all expected and manageable with supportive care and dose modifications. MTD and RP2D were identified as selinexor 80 mg, carfilzomib 56 mg/m², and dexamethasone 40 mg, all QW. The overall response rate was 78% including 14 (44%) ≥ very good partial responses. Median progression-free survival was 15 months.

Conclusions

Weekly XKd is highly effective and well-tolerated. These data support further investigation of XKd in patients with MM.

Chromosome Region Maintenance 1 (XPO1/CRM1) as an Anticancer Target and Discovery of Its Inhibitor

Chromosome region maintenance 1 (CRM1) is a major nuclear export receptor protein and contributes to cell homeostasis by mediating the transport of cargo from the nucleus to the cytoplasm. CRM1 is a therapeutic target comprised of several tumor types, including osteosarcoma, multiple myeloma, gliomas, and pancreatic cancer. In the past decade, dozens of CRM1 inhibitors have been discovered and developed, including KPT-330, which received FDA approval for multiple myeloma (MM) and diffuse large B-cell lymphoma (DLBCL) in 2019 and 2020, respectively. This review summarizes the biological functions of CRM1, the current understanding of the role CRM1 plays in cancer, the discovery of CRM1 small-molecule inhibitors, preclinical and clinical studies on KPT-330, and other recently developed inhibitors. A new CRM1 inhibition mechanism and structural dynamics are discussed. Through this review, we hope to guide the future design and optimization of CRM1 inhibitors.

Proteostasis deregulation as a driver of C9ORF72 pathogenesis

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are two related neurodegenerative disorders that display overlapping features. The hexanucleotide repeat expansion GGGGCC (G₄ C₂ ) in C9ORF72 gene has been causally linked to both ALS and FTD emergence, thus opening a novel potential therapeutic target for disease intervention. The main driver of C9ORF72 pathology is the disruption of distinct cellular processes involved in the function of the proteostasis network. Here we discuss main findings relating to the induction of neurodegeneration by C9ORF72 mutation and proteostasis deregulation, highlighting the role of the endoplasmic reticulum stress, nuclear transport, and autophagy in the disease process. We further discuss possible points of intervention to target proteostasis mediators to treat C9ORF72-linked ALS/FTD.

Novel Non-Immunologic Agents for Relapsed and Refractory Multiple Myeloma: A Review Article

Novel treatments are needed to address the lack of options for patients with relapsed or refractory multiple myeloma. Even though immunotherapy-based treatments have revolutionized the field in recent years, offering new opportunities for patients, there is still no curative therapy. Thus, non-immunologic agents, which have proven effective for decades, are still central to the treatment of multiple myeloma, especially for advanced disease. Building on their efficacy in myeloma, the development of proteasome inhibitors and immunomodulatory drugs has been pursued, and has led to the emergence of a novel generation of agents (e.g., carfilzomib, ixazomib, pomalidomide). The use of alkylating agents is decreasing in most treatment regimens, but melflufen, a peptide-conjugated alkylator with a completely new mechanism of action, offers interesting opportunities. Moreover, with the identification of novel targets, new drug classes have entered the myeloma armamentarium, such as XPO1 inhibitors (selinexor), HDAC inhibitors (panobinostat), and anti-BCL-2 agents (venetoclax). New pathways are still being explored, especially the possibility of a mutation-driven strategy, as biomarkers and targeted treatments are increasing. Though multiple myeloma is still considered incurable, the treatment options are expanding and are progressively becoming more diverse, largely because of the continuous development of non-immunologic agents.

Targeting Nuclear Export Proteins in Multiple Myeloma Therapy

Multiple myeloma (MM) is an incurable malignancy of plasma cells with a clinical course characterized by multiple relapses and treatment refractoriness. While recent treatment advancements have extended overall survival (OS), refractory MM has a poor prognosis, with a median OS of between 4 and 6 months. Nuclear export inhibition, specifically inhibition of CRM1/XPO1, is an emerging novel treatment modality that has shown promise in treatment-refractory MM. Initially discovered in yeast in 1983, early clinical applications were met with significant toxicities that limited their utility. The creation of small molecule inhibitors of nuclear export (SINE) has improved on toxicity limitations and has led to investigation in a number of malignancies at the preclinical and clinical stages. Preclinical studies of SINEs in MM have shown that these molecules are cytotoxic to myeloma cells, play a role in therapy resensitization, and suggest a role in limiting bone disease progression. In July 2019, selinexor became the first nuclear export inhibitor approved for use in relapsed/refractory MM based on the STORM trial. As of May 2020, there were eight ongoing trials combining selinexor with standard treatment regimens in relapsed/refractory MM. Eltanexor, a second-generation SINE, is also under investigation and has shown preliminary signs of efficacy in an early clinical trial while potentially having an improved toxicity profile compared with selinexor. Results in ongoing trials will help further define the role of SINEs in MM.

Impact of XPO1 mutations on survival outcomes in metastatic non-small cell lung cancer (NSCLC)

BACKGROUND

Nuclear protein transport is essential in guiding the traffic of important proteins and RNAs between the nucleus and cytoplasm. Export of proteins from the nucleus is mostly regulated by Exportin 1 (XPO1). In cancer, XPO1 is almost universally hyperactive and can promote the export of important tumor suppressors to the cytoplasm. Currently, there are no studies evaluating XPO1 amplifications and mutations in NSCLC and the impact on outcomes.

METHODS

Tumor samples were analyzed using next-generation sequencing (NGS) (NextSeq, 592 Genes), immunohistochemistry (IHC), and whole transcriptome sequencing (WTS, NovaSeq) (Caris Life Sciences, Phoenix, AZ). Survival was extracted from insurance claims data and calculated from time of tissue collection to last contact using Kaplan-Meier estimate.

RESULTS

Among 18,218 NSCLC tumors sequenced, 26 harbored XPO1 mutations and 24 had amplifications. XPO1 mutant tumors were more likely to have high TMB (79% vs. 52%, p = 0.007) and less likely to have high PD-L1 (32% vs. 68%, p = 0.03). KRAS co-mutations were seen in 19% (n = 5) and EGFR co-mutations were rare (n = 2). Among the 17,449 NSCLC tumors with clinical data, there were 24 XPO1 mutant. Comparison of survival between XPO1 mutant and WT showed a negative association with a hazard ratio (HR) of 1.932 (95% CI: 1.144-3.264 p = 0.012). XPO1 amplification was not associated with survival.

CONCLUSIONS

XPO1 pathogenic mutations were associated with a poor survival in NSCLC. Although XPO1 mutations are rare in NSCLC, further studies to assess its associations with treatment responses are warranted.

Novel Approaches Outside the Setting of Immunotherapy for the Treatment of Multiple Myeloma: The Case of Melflufen, Venetoclax, and Selinexor

Although the survival rate of patients with multiple myeloma has significantly improved in the last years thanks to the introduction of various classes of new drugs, such as proteasome inhibitors, immunomodulatory agents, and monoclonal antibodies, the vast majority of these subjects relapse with a more aggressive disease due to the acquisition of further genetic alterations that may cause resistance to current salvage therapies. The treatment of these often "triple" (or even more) refractory patients remains challenging, and alternative approaches are required to overcome the onset of that resistance. Immunotherapies with novel monoclonal, drug-conjugated, or bi-specific antibodies, as well as the use of chimeric antigen receptor T cells, have been recently developed and are currently investigated. However, other non-immunologic therapeutic regimens based on melfluflen, venetoclax, or selinexor, three molecules with new mechanisms of action, have also shown promising results in the setting of relapsed/refractory myeloma. Here we report the most recent literature data regarding these three drugs, focusing on their efficacy and safety in multiple myeloma.

Selinexor, bortezomib, and dexamethasone versus bortezomib and dexamethasone in previously treated multiple myeloma: Outcomes by cytogenetic risk

In the phase 3 BOSTON study, patients with multiple myeloma (MM) after 1-3 prior regimens were randomized to once-weekly selinexor (an oral inhibitor of exportin 1 [XPO1]) plus bortezomib-dexamethasone (XVd) or twice-weekly bortezomib-dexamethasone (Vd). Compared with Vd, XVd was associated with significant improvements in median progression-free survival (PFS), overall response rate (ORR), and lower rates of peripheral neuropathy, with trends in overall survival (OS) favoring XVd. In BOSTON, 141 (35.1%) patients had MM with high-risk (presence of del[17p], t[4;14], t[14;16], or ≥4 copies of amp1q21) cytogenetics (XVd, n = 70; Vd, n = 71), and 261 (64.9%) exhibited standard-risk cytogenetics (XVd, n = 125; Vd, n = 136). Among patients with high-risk MM, median PFS was 12.91 months for XVd and 8.61 months for Vd (HR, 0.73 [95% CI, (0.4673, 1.1406)], p = 0.082), and ORRs were 78.6% and 57.7%, respectively (OR 2.68; p = 0.004). In the standard-risk subgroup, median PFS was 16.62 months for XVd and 9.46 months for Vd (HR 0.61; p = 0.004), and ORRs were 75.2% and 64.7%, respectively (OR 1.65; p = 0.033). The safety profiles of XVd and Vd in both subgroups were consistent with the overall population. These data suggest that selinexor can confer benefits to patients with MM regardless of cytogenetic risk. ClinicalTrials.gov identifier: NCT03110562.

Selinexor, a selective inhibitor of nuclear export, enhances the anti-tumor activity of olaparib in triple negative breast cancer regardless of BRCA1 mutation status

Triple negative breast cancer (TNBC) is a deadly disease with limited treatment options. Selinexor is a selective inhibitor of nuclear export that binds covalently to exportin 1 thereby reactivating tumor suppressor proteins and downregulating expression of oncogenes and DNA damage repair (DDR) proteins. Olaparib is a poly (ADP-ribose) polymerase (PARP) inhibitor approved for the treatment of patients with breast cancer harboring BRCA mutations. We examined the effects of co-treatment with selinexor and olaparib in TNBC cell lines. BRCA1 wildtype (BRCA1-wt) and BRCA1 mutant (BRCA1-mut) TNBC cell lines were treated with selinexor and/or olaparib and effects on cell viability and cell cycle were evaluated. The effects of treatment were also evaluated in mouse xenograft models generated with BRCA1-wt and BRCA1-mut TNBC cell lines. Treatment with selinexor inhibited cell proliferation and survival of all TNBC cell lines tested in vitro. This effect was enhanced following treatment of the cells with the combination of selinexor and olaparib, which showed synergistic effects on tumor growth inhibition in MDA-MB-468-derived (BRCA1-wt) and MDA-MB-436-derived (BRCA1-mut) xenografts. As co-treatment with selinexor and olaparib exhibits anti-tumor activity regardless of BRCA1 mutation status, the clinical implications of the combination warrant further investigation.

Comparison of the Effectiveness and Safety of the Oral Selective Inhibitor of Nuclear Export, Selinexor, in Diffuse Large B Cell Lymphoma Subtypes

BACKGROUND

The SADAL study evaluated oral selinexor in patients with relapsed and/or refractory diffuse large B-cell lymphoma (DLBCL) after at least 2 prior lines of systemic therapy. In this post-hoc analysis, we analyzed the outcomes of the SADAL study by DLBCL subtype to determine the effects of DLBCL subtypes on efficacy and tolerability of selinexor.

PATIENTS AND METHODS

Data from 134 patients in SADAL were analyzed by DLBCL subtypes for overall response rate (ORR), overall survival (OS), duration of treatment response, progression-free survival, and adverse events rate.

RESULTS

ORR in the entire cohort was 29.1%, and similar in patients with germinal center (GCB) versus non-GCB DLBCL (31.7% vs. 24.2%, P = 0.45); transformed DLBCL showed a trend towards higher ORR than de novo DLBCL: 38.7% vs. 26.2% (P = 0.23). Despite similar prior treatment regimens and baseline characteristics, patients with DLBCL and normal C-MYC/BCL-2 protein expression levels had a significantly higher ORR (46.2% vs.14.8%, P = 0.012) and significantly longer OS (medians 13.7 vs. 5.1 months, hazard ratio 0.43 [95% CI, 0.23-0.77], P = 0.004) as compared with those whose DLBCL had C-MYC and BCL-2 overexpression. Among patients who had normal expression levels of either C-MYC or BCL-2 and baseline hemoglobin levels ≥ 10g/dL, ORR was 51.5% (n = 47), with median OS of 15.5 months and median PFS of 4.6 months. Similar rates of adverse events were noted in all subgroups.

CONCLUSIONS

Overall, single agent oral selinexor showed strong responses in patients with limited treatment alternatives regardless of germinal center B-cell type or disease origin.

Proteomics identify nuclear export as a targetable pathway in neuroblastoma: Comment on "XPO1 inhibition with selinexor synergizes with proteasome inhibition in neuroblastoma by targeting nuclear export of IκB"

Neuroblastoma (NBL) is an embryonal malignancy of childhood with poor outcomes for patient with high-risk disease. Multimodal treatment approaches have improved outcomes but at the cost of significant toxicity, and there is no durable therapeutic approach for relapsed disease. As NBL has no singular oncogenic driver, targeted therapeutic options have been limited. Galinski et al report the results of a proteomic screen of neuroblastomas and identify the nuclear export protein XPO1 as a protein that is preferentially expressed and located in neuroblast nuclei. XPO1 overexpression is associated with nuclear export of IκB and increased NF-κB activity, both of which can be abrogated in NBL cell lines with the XPO1 inhibitor Selinexor with or without the proteasome inhibitor bortezomib. This work highlights new strategies for therapeutic target identification and the novel identification of nuclear export as a targetable oncogenic pathway across malignancies.

Bioanalysis of selinexor in mouse plasma micro-samples utilizing UPLC-MS/MS

Selinexor, a first-in-class inhibitor of the nuclear export protein Exportin-1 (XPO1), was recently approved for the treatment of multiple myeloma in combination with dexamethasone, and as monotherapy for diffuse large B-cell lymphoma. To enable investigations of selinexor in mice, we established and validated an ultrahigh-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) assay in the plasma concentration range of 1-1000 ng/mL using plasma microsamples of 5 µL. Protein depletion with acetonitrile was used for efficient isolation of selinexor which was followed by a dilution step, resulting in a scalable sample processing. Quantification was performed with positive electrospray ionization tandem mass spectrometry in the selected reaction monitoring mode. Due to the high sensitivity of the quantification and the scalable sample processing procedure, the assay can be used for different concentration ranges to either further decrease the achievable lower limit of quantification or to reduce the amount of plasma used. The assay showed interday and intraday accuracy of 89.0-109.0% with a corresponding precision ≤ 14.1%. Suitability for investigations of selinexor in small animal experiments was demonstrated by determination of plasma selinexor in mice after oral administration.

XPO1 inhibition with selinexor synergizes with proteasome inhibition in neuroblastoma by targeting nuclear export of IkB

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XPO1 is overabundant in high-risk neuroblastoma and correlates with poor survival.

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Neuroblastoma cells are sensitive to XPO1 inhibition with selinexor.

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Use of selinexor results in nuclear retention of IkB, diminishing NF-kB activity.

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Selinexor and bortezomib act synergistically through promotion of apoptosis.

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Synergy is mediated in part, through IkB regulation of NF-kB activity.

Across many cancer types in adults, upregulation of the nuclear-to-cytoplasmic transport protein Exportin-1 (XPO1) correlates with poor outcome and responsiveness to selinexor, an FDA-approved XPO1 inhibitor. Similar data are emerging in childhood cancers, for which selinexor is being evaluated in early phase clinical studies. Using proteomic profiling of primary tumor material from patients with high-risk neuroblastoma, as well as gene expression profiling from independent cohorts, we have demonstrated that XPO1 overexpression correlates with poor patient prognosis. Neuroblastoma cell lines are also sensitive to selinexor in the low nanomolar range. Based on these findings and knowledge that bortezomib, a proteasome inhibitor, blocks degradation of XPO1 cargo proteins, we hypothesized that combination treatment with selinexor and bortezomib would synergistically inhibit neuroblastoma cellular proliferation. We observed that selinexor promoted nuclear retention of IkB and that bortezomib augmented the ability of selinexor to induce cell-cycle arrest and cell death by apoptosis. This synergy was abrogated through siRNA knockdown of IkB. The synergistic effect of combining selinexor and bortezomib in vitro provides rationale for further investigation of this combination treatment for patients with high-risk neuroblastoma.

KPT-330 Prevents Aortic Valve Calcification via a Novel C/EBPβ Signaling Pathway

[Figure: see text].

Pharmacokinetics of Selinexor: The First-in-Class Selective Inhibitor of Nuclear Export

The functionality of many tumor suppressor proteins (TSPs) and oncoprotein transcript RNAs largely depend on their location within the cell. The exportin 1 complex (XPO1) transports many of these molecules from the nucleus into the cytoplasm, thereby inactivating TSPs and activating oncoprotein transcript RNAs. Aberrations of these molecules or XPO1 can increase this translocation process, leading to oncogenesis. Selinexor is a selective inhibitor of nuclear export and is an active agent in various malignancies. It is currently approved for relapsed or refractory diffuse large B-cell lymphoma as well as multiple myeloma. Following oral administration, selinexor exhibits linear and time-independent pharmacokinetics (PK) across a wide dose range, with moderately rapid absorption (time to reach maximum concentration [T_max] 2-4 h) and moderate elimination (half-life [t_½] 6-8 h). Selinexor PK observed among patients with various solid tumors and hematologic malignancies is consistent irrespective of disease. Population PK analyses demonstrated the PK of selinexor is well-described by a two-compartment model, with significant relationships for body weight on apparent clearance and apparent central volume of distribution, and sex on apparent clearance, which result in clinically non-relevant changes in exposure. These analyses also suggested selinexor PK are not significantly impacted by various concomitant medications and organ dysfunction (hepatic/renal). The time course of selinexor PK appears similar between pediatric and adult patients, although higher exposures have been observed among pediatric patients relative to adults administered similar milligrams per meter squared (mg/m²) doses of selinexor.

Targeted Therapies for Multiple Myeloma

Multiple myeloma continues to be a challenging disorder to treat despite improved therapies and the widespread use of proteasome inhibitors and immunomodulatory drugs. Although patient outcomes have improved, the disease continues to invariably relapse, and in the majority of cases, a cure remains elusive. In the last decade, there has been an explosion of novel drugs targeting cellular proteins essential for malignant plasma cell proliferation and survival. In this review, we focus on novel druggable targets leading to the development of monoclonal antibodies and cellular therapies against surface antigens (CD38, CD47, CD138, BCMA, SLAMF7, GPRC5D, FcRH5), inhibitors of epigenetic regulators such as histone deacetylase (HDAC), and agents targeting anti-apoptotic (BCL-2), ribosomal (eEF1A2) and nuclear export (XPO1) proteins.

The nuclear export protein XPO1 - from biology to targeted therapy

Exportin 1 (XPO1), also known as chromosome region maintenance protein 1, plays a crucial role in maintaining cellular homeostasis via the regulated export of a range of cargoes, including proteins and several classes of RNAs, from the nucleus to the cytoplasm. Dysregulation of this protein plays a pivotal role in the development of various solid and haematological malignancies. Furthermore, XPO1 is associated with resistance to several standard-of-care therapies, including chemotherapies and targeted therapies, making it an attractive target of novel cancer therapies. Over the years, a number of selective inhibitors of nuclear export have been developed. However, only selinexor has been clinically validated. The novel mechanism of action of XPO1 inhibitors implies a different toxicity profile to that of other agents and has proved challenging in certain settings. Nonetheless, data from clinical trials have led to the approval of the XPO1 inhibitor selinexor (plus dexamethasone) as a fifth-line therapy for patients with multiple myeloma and as a monotherapy for patients with relapsed and/or refractory diffuse large B cell lymphoma. In this Review, we summarize the progress and challenges in the development of nuclear export inhibitors and discuss the potential of emerging combination therapies and biomarkers of response.

Selinexor, selective inhibitor of nuclear export: Unselective bullet for blood cancers

Exportin 1 (XPO1), also known as chromosome maintenance 1 protein (CRM1), is the main transporter for hundreds of proteins like tumor suppressors, growth regulatory factors, oncoprotein mRNAs and others. Its upregulation leads to the inactivation of the tumor suppressor anti-neoplastic function in many cancers and logically is associated with poor prognosis. Selective inhibitors of nuclear export (SINE) are a new generation of XPO1 inhibitors that are being investigated as a promising targeted anti-cancer therapy. Selinexor is the first generation of SINE compounds that is being evaluated in many clinical trials involving solid tumors and hematological malignancies with its two approved indications for relapsed multiple myeloma and relapsed diffuse large B-cell lymphoma. Here, we comprehensively review the current knowledge of selinexor and next generations of the SINE compounds in lymphoid and myeloid malignancies.

Multi-omics tumor profiling technologies to develop precision medicine in multiple myeloma

Multiple myeloma (MM), the second most common hematologic cancer, is caused by accumulation of aberrant plasma cells in the bone marrow. Its molecular causes are not fully understood and its great heterogeneity among patients complicates therapeutic decision-making. In the past decades, development of new therapies and drugs have significantly improved survival of MM patients. However, resistance to drugs and relapse remain the most common causes of mortality and are the major challenges to overcome. The advent of high throughput omics technologies capable of analyzing big amount of clinical and biological data has changed the way to diagnose and treat MM. Integration of omics data (gene mutations, gene expression, epigenetic information, and protein and metabolite levels) with clinical histories of thousands of patients allows to build scores to stratify the risk at diagnosis and predict the response to treatment, helping clinicians to make better educated decisions for each particular case. There is no doubt that the future of MM treatment relies on personalized therapies based on predictive models built from omics studies. This review summarizes the current treatments and the use of omics technologies in MM, and their importance in the implementation of personalized medicine.

Multi-omics tumor profiling technologies to develop precision medicine in multiple myeloma

Multiple myeloma (MM), the second most common hematologic cancer, is caused by accumulation of aberrant plasma cells in the bone marrow. Its molecular causes are not fully understood and its great heterogeneity among patients complicates therapeutic decision-making. In the past decades, development of new therapies and drugs have significantly improved survival of MM patients. However, resistance to drugs and relapse remain the most common causes of mortality and are the major challenges to overcome. The advent of high throughput omics technologies capable of analyzing big amount of clinical and biological data has changed the way to diagnose and treat MM. Integration of omics data (gene mutations, gene expression, epigenetic information, and protein and metabolite levels) with clinical histories of thousands of patients allows to build scores to stratify the risk at diagnosis and predict the response to treatment, helping clinicians to make better educated decisions for each particular case. There is no doubt that the future of MM treatment relies on personalized therapies based on predictive models built from omics studies. This review summarizes the current treatments and the use of omics technologies in MM, and their importance in the implementation of personalized medicine.

Recurrent XPO1 mutations alter pathogenesis of chronic lymphocytic leukemia

BACKGROUND

Exportin 1 (XPO1/CRM1) is a key mediator of nuclear export with relevance to multiple cancers, including chronic lymphocytic leukemia (CLL). Whole exome sequencing has identified hot-spot somatic XPO1 point mutations which we found to disrupt highly conserved biophysical interactions in the NES-binding groove, conferring novel cargo-binding abilities and forcing cellular mis-localization of critical regulators. However, the pathogenic role played by change-in-function XPO1 mutations in CLL is not fully understood.

METHODS

We performed a large, multi-center retrospective analysis of CLL cases (N = 1286) to correlate nonsynonymous mutations in XPO1 (predominantly E571K or E571G; n = 72) with genetic and epigenetic features contributing to the overall outcomes in these patients. We then established a mouse model with over-expression of wildtype (wt) or mutant (E571K or E571G) XPO1 restricted to the B cell compartment (Eµ-XPO1). Eµ-XPO1 mice were then crossed with the Eµ-TCL1 CLL mouse model. Lastly, we determined crystal structures of XPO1 (wt or E571K) bound to several selective inhibitors of nuclear export (SINE) molecules (KPT-185, KPT-330/Selinexor, and KPT-8602/Eltanexor).

RESULTS

We report that nonsynonymous mutations in XPO1 associate with high risk genetic and epigenetic features and accelerated CLL progression. Using the newly-generated Eµ-XPO1 mouse model, we found that constitutive B-cell over-expression of wt or mutant XPO1 could affect development of a CLL-like disease in aged mice. Furthermore, concurrent B-cell expression of XPO1 with E571K or E571G mutations and TCL1 accelerated the rate of leukemogenesis relative to that of Eµ-TCL1 mice. Lastly, crystal structures of E571 or E571K-XPO1 bound to SINEs, including Selinexor, are highly similar, suggesting that the activity of this class of compounds will not be affected by XPO1 mutations at E571 in patients with CLL.

CONCLUSIONS

These findings indicate that mutations in XPO1 at E571 can drive leukemogenesis by priming the pre-neoplastic lymphocytes for acquisition of additional genetic and epigenetic abnormalities that collectively result in neoplastic transformation.

Addressing Non-linear System Dynamics of Single-Strand RNA Virus-Host Interaction

Positive single-strand ribonucleic acid [(+)ssRNA] viruses can cause multiple outbreaks, for which comprehensive tailored therapeutic strategies are still missing. Virus and host cell dynamics are tightly connected, generating a complex dynamics that conveys in virion assembly to ensure virus spread in the body. Starting from the knowledge of relevant processes in (+ss)RNA virus replication, transcription, translation, virions budding and shedding, and their respective energy costs, we built up a systems thinking (ST)-based diagram of the virus-host interaction, comprehensive of stocks, flows, and processes as well-described in literature. In ST approach, stocks and flows are expressed by a proxy of the energy embedded and transmitted, respectively, whereas processes are referred to the energy required for the system functioning. In this perspective, healthiness is just a particular configuration, in which stocks relevant for the system (equivalent but not limited to proteins, RNA, DNA, and all metabolites required for the survival) are constant, and the system behavior is stationary. At time of infection, the presence of additional stocks (e.g., viral protein and RNA and all metabolites required for virion assembly and spread) confers a complex network of feedbacks leading to new configurations, which can evolve to maximize the virions stock, thus changing the system structure, output, and purpose. The dynamic trajectories will evolve to achieve a new stationary status, a phenomenon described in microbiology as integration and symbiosis when the system is resilient enough to the changes, or the system may stop functioning and die. Application of external driving forces, acting on processes, can affect the dynamic trajectories adding a further degree of complexity, which can be captured by ST approach, used to address these new configurations. Investigation of system configurations in response to external driving forces acting is developed by computational analysis based on ST diagrams, with the aim at designing novel therapeutic approaches.

Quantitative expression of Ikaros, IRF4, and PSMD10 proteins predicts survival in VRD-treated patients with multiple myeloma

The search for biomarkers based on the mechanism of drug action has not been thoroughly addressed in the therapeutic approaches to multiple myeloma (MM), mainly because of the difficulty in analyzing proteins obtained from purified plasma cells. Here, we investigated the prognostic impact of the expression of 12 proteins involved in the mechanism of action of bortezomib, lenalidomide, and dexamethasone (VRD), quantified by capillary nanoimmunoassay, in CD138-purified samples from 174 patients with newly diagnosed MM treated according to the PETHEMA/GEM2012 study. A high level of expression of 3 out of 5 proteasome components tested (PSMD1, PSMD4, and PSMD10) negatively influenced survival. The 5 analyzed proteins involved in lenalidomide's mode of action were associated with time to progression (TTP); low levels of cereblon and IRF4 protein and high levels of Ikaros, AGO2, and Aiolos were significantly associated with shorter TTP. Although the glucocorticoid receptor (GCR) level by itself had no significant impact on MM prognosis, a high XPO1 (exportin 1)/GCR ratio was associated with shorter TTP and progression-free survival (PFS). The multivariate Cox model identified high levels of PSMD10 (hazard ratio [HR] TTP, 3.49; P = .036; HR PFS, 5.33; P = .004) and Ikaros (HR TTP, 3.01, P = .014; HR PFS, 2.57; P = .028), and low levels of IRF4 protein expression (HR TTP, 0.33; P = .004; HR PFS, 0.35; P = .004) along with high-risk cytogenetics (HR TTP, 3.13; P < .001; HR PFS, 2.69; P = .002), as independently associated with shorter TTP and PFS. These results highlight the value of assessing proteins related to the mechanism of action of drugs used in MM for predicting treatment outcome.