Selective Inhibitor Of Nuclear Export Research Articles

Novel Combination of Clinical Menin Inhibitor Ziftomenib and the Nuclear Export Inhibitor Selinexor Synergistically Inhibit MLL-r AML

PURPOSE: Menin is a scaffold protein that tethers histone-lysine-N-methyltransferase MLL1 (KMT2A) to chromatin by binding to the menin binding domain (MBD) of KMT2A. The N-terminus of the KMT2A gene recombines with a range of genes to form more than 80 fusion proteins (FP) in MLL-rearranged (MLL-r) AML. In myeloid stem progenitor cells, the menin-KMT2A complex modulates the expression of the leukemogenic homeobox A9 (HOXA9) gene, as well as its co-factor, MEIS1. Menin inhibitors evict menin from the chromatin and reduce KMT2A and KMT2A-FP binding to their targets in MLL-r leukemia, breaking the differentiation block and inducing tumor regression. Aberrant nuclear export is common in cancer, resulting in anomalous localization of various proteins, including tumor suppressor proteins (TSPs). Blocking XPO1/CRM1 using a selective inhibitor of nuclear export (SINE) compound selinexor has been shown to have robust anti-leukemia activity. In the present study, we hypothesized that inhibition of menin and nuclear export would synergistically suppress AML cell proliferation and survival. We have used the clinical-stage menin inhibitor ziftomenib and selinexor to simultaneously target menin-KMT2A protein-protein interactions and nuclear export. METHODS: To assess growth inhibition, an ATP-based cell proliferation assay was used. Combination synergy was determined using CalcuSyn Version 2.0 synergy software. Stem-like progenitor cells were isolated using the StemSpan CD34+ expansion kit (StemCell Tech). Colony formation efficiency was determined using a Methocult assay (StemCell Tech). Gene and protein expression and cell death were detected using quantitative real-time PCR, western blotting, and annexin-V/PI fluorescence-activated cell sorting, respectively. RESULTS: The clinical candidate ziftomenib, in combination with selinexor, synergistically inhibited the growth of MLL-r AML cell lines (MV4;11, MOLM13, and SEM) (CI<1) [Fig.1A]. The combination of menin and XPO1 inhibitors significantly suppressed colony formation of CD34+ MLL-r progenitor cells derived from primary patient samples but was not toxic to normal CD34+ human hematopoietic progenitor stem cells (HPSCs). Menin inhibitor treatment caused the downregulation of menin protein along with its downstream targets HOXA9, MEIS1, and FLT3 in western blot analysis. Interestingly, the nuclear export inhibitor selinexor also reduced menin, HOXA9, and MEIS1 protein levels. The combination of menin and XPO1 inhibitors enhanced menin down expression, suggesting a molecular basis for the synergy between the two compounds [Fig 1.B]. Ziftomenib suppressed the expression of menin in a time-dependent manner, which is evident as early as six hours of treatment. This combination significantly enhanced both early and late apoptotic cell death in MLL-rearranged AML cells compared to either compound alone. We have performed total RNA sequencing and observed differential expression of certain mRNAs and micro RNAs (miRs). The TMEM191B, SH3TC1, and SULT1C2 mRNAs were upregulated by KO539 and Selinexor, which are enhanced further by combination treatment. On the contrary, CENPK, CKS2, KIF18A, and H2BC4 mRNAs were downregulated by a single agent or combination. Among miRs, hsa-miR-34a-5p, hsa-miR-142-3p, hsa-miR-26b-5p were upregulated and hsa-miR-33b-3p, hsa-miR-4454, hsa-miR-210-3p and hsa-miR-130b-3p [reported to be an essential lineage-specific codriver of MLL-AF4 leukemia] were downregulated by single agent or combination. Such mRNAs and miRs panels could serve as biomarkers for treatment response. CONCLUSION: These preclinical findings demonstrate that simultaneous inhibition of the menin-KMT2A interaction and nuclear export could be a viable strategy for the treatment of MLL-r AML. Ongoing experiments with CDX and PDX using MLL-r models and functional analysis using total transcriptome sequencing and proteomics will be presented at the ASH meeting. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Selinexor in Combination with R-GDP for Patients with Relapsed/Refractory B-Cell Lymphoma: Final Results of 18 Patients Treated at RP2D of Selinexor in the Selinda Phase Ib Lysa Study

Background: Salvage chemotherapy followed by high-dose therapy (HDT) and autologous stem-cell transplantation (ASCT) is an option to treat young patients (pts) with relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL). A complete remission before ASCT is the most important prognosis factor for a better outcome. Selinexor is a first-in-class, oral selective inhibitor of nuclear export which, through XPO1 blockade, causes nuclear accumulation and activation of tumor suppressor proteins, reduction in oncoproteins and cancer cell apoptosis. Selinexor has been approved by the US Food and Drug Administration for the treatment of R/R DLBCL, including de novo or transformed from follicular lymphoma (FL) pts after ≥2 therapies. The phase Ib SELINDA (EUDRACT 2015-005612-15) study assessed safety and efficacy of selinexor, in combination with R-GDP for pts with R/R B-cell lymphoma. Patients & methods: Eligible pts <70 years with R/R B-cell lymphoma after first or second treatment failure received every 21 days (d) 3 cycles of rituximab 375 mg/m² on D1, dexamethasone 40 mg on D1 to 4, cisplatin 75 mg/m² D1 and gemcitabine 1000 mg/m² on D1 and 8 (R-GDP) in combination with escalating doses of selinexor. Two dose levels of selinexor, 40mg and 60mg, were evaluated via 3+3 design. Initial dosing of selinexor for dose level 1 (DL1) was 40 mg on D1, 3, 8, 10. The dosing was modified to 40mg and 60mg on D1, 8, 15 for DL1 and DL2, respectively. The primary endpoint of SELINDA was the determination of the recommended phase 2 dose (RP2D) of selinexor in combination with R-GDP. Secondary and exploratory endpoints were safety, efficacy, and feasibility of ASCT after selinexor-R-GDP. Results: The R2PD for selinexor in combination with R-GDP was established as 40mg on days 1, 8, and 15 (Maerevoet, IMCL 2021#176). Between January 2017 and January 2021, 32 pts received selinexor-R-GDP. We focused on the 18 pts who received the R2PD: 15 had DLBCL, 2 FL, 1 marginal zone lymphoma. In this cohort, median age was 61 years (range 44-69); 14 pts (78%) had stage III/IV, 6 had disease refractory to last treatment, 12 had relapsed. Thirteen pts received 1 previous line of treatment before inclusion, 5 pts received 2 previous lines. Four pts prematurely discontinued treatment: 2 for thrombocytopenia, 1 for COVID, 1 for disease progression. Major adverse events (AEs) in >10% of pts were reversible neutropenia (55 %), thrombocytopenia (44 %), and nausea (22%). No fatal AEs were observed. One patient is not evaluated, 7 pts (39%) achieved a complete metabolic response (CMR), 5 pts (28%) partial metabolic response (PMR) and 5 pts (28%) stable disease or progressive disease. According to Lugano criteria's, overall response rate (ORR) assessed at the end of treatment was 67%. Nine of the 15 pts (60 %) with DLBCL had metabolic response (CMR: 4, PMR: 5). Per protocol, peripheral stem cell collection and ASCT were optional, 4 pts of this RP2D cohort proceeded to high dose therapy with BEAM conditioning and ASCT. For this RP2D cohort, the 1-year overall survival is 72.2% and the 1 Year-PFS is 45%. The median duration of response was not reached (95%CI: 0.4-NA) (figure 1) Conclusion: This study established the safety profile of weekly 40mg of selinexor in combination with R-GDP for R/R B cell lymphoma with an ORR of 67%, the median DOR is not reached. Reversible AEs were as expected for a platinum combination regimen. An ongoing randomized phase 2 study comparing R-GDP with or without selinexor in pts with R/R DLBCL will further evaluate the safety and efficacy of the combination. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Selinexor in Combination with R-GDP/R-ICE Regimen for Refractory Aggressive Large B-Cell Lymphoma Patients with TP53 Alterations

BackgroundTP53 has been identified as one of the most frequently altered gene in large B-cell lymphoma (LBCL). The prognosis of LBCL patients (pts) with TP53 mutations is poor in R-CHOP era, even treated with autologous stem-cell transplantation (ASCT) or anti-CD19 chimeric antigen receptor T-cell (CAR-T) therapy. Furthermore, TP53 mutation rate was much higher in LBCL pts who acquired relapsed or refractory (R/R) disease and associated with therapeutic resistance. Selinexor is a selective inhibitor of nuclear export with promising anti-cancer properties. Several clinical studies have proved selinexor in combination with R-GDP/R-ICE was effective in relapsed/refractory LBCL and preclinical studies reported that selinexor could suppress tumor cells with TP53 mutations. Method Relapsed/refractory LBCL pts with TP53 alterations (including TP53 mutation and/or deletion) were enrolled to be treated with selinexor plus R-GDP/R-ICE since November 2021 in our center. Selinexor was administered orally (40 mg day 1, 8, 15) plus R-GDP (R 375mg/m2 d0, gemcitabine 1g/m2×d1, cisplatin 25mg/m2 d1-d3, dexamethasone 40mg d1-d4) or R-ICE (R 375mg/m2 d0, ifosfamide 1.5g/m2×3d, carboplatin (AUC 5) and etoposide 100mg/m2×3d) every 3 weeks as per physician's choice. Objective response rate (ORR) was evaluated every 3 cycles based on Lugano 2014 criteria and Adverse events (AE) were rated according to the NCI CTCAE 5.0. Results In total, eleven patients treated with at least 3 cycles of selinexor plus R-GDP/R-ICE and were eligible for initial efficacy evaluation. The median age of the 11 pts was 63 years (range 18 to 77), 7 pts (63.6%) were male, 5 pts (45.5%) had stage III-IV disease, 63.6% of patients with IPI intermediate to high risk. The median number of prior regimen was 2 (range, 1-4), with 2 patients (3 L) and 1 patient (4L). 9 pts were refractory to the last regimen. The mutational profile was presented in Figure 1 (7 patients with TP53 mutation, 3 patients with TP53 mutation and deletion, 1 patient with TP53 deletion). Pts received a median of four cycles (range, 3-6) of selinexor 40mg once a week combined with R-GDP/R-ICE (9 patients received selinexor plus R-GDP and 2 received selinexor plus R-ICE) (Table 1). The most common treatment-related adverse events were grade 1 or 2, including nausea (81.8%), fatigue (81.8%), and anorexia (27.3%) and the most common grade 3 or 4 adverse events were hematological toxicities including neutropenia (63.6%), thrombocytopenia (45.5%)，anemia (9.0%). 2 pts after interim evaluation with PR stopped treatment for one month due to gastrointestinal toxicities and had disease progression. Both of them continued to receive their prior regimen (selinexor-RGDP and selinexor-RICE regimen, respectively). Of the ten evaluable patients, the overall and complete response rates at interim evaluation were 100% and 20%, respectively (the left patient will have interim evaluation at the mid of August). ConclusionsTP53 alterations are an established poor outcome marker in LBCL. To our knowledge, this is the first report on TP53-altered relapsed/refractory aggressive B-cell lymphomas treated upon the combination of selinexor and chemotherapy. The new exploration showed promising response rates in patients with relapsed/refractory TP53-altered LBCL and was well tolerated. In addition, clinicians should be cautious to its GI toxicities with more proactive prevention and management measures. Selinexor (40mg qw) with R-GDP/R-ICE is worthy of further study based on the preliminary efficacy results. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

MUKtwelve protocol: a phase II randomised, controlled, open, parallel group, multicentre trial of selinexor, cyclophosphamide and prednisolone (SCP) versus cyclophosphamide and prednisolone (CP) in patients with relapsed or refractory multiple myeloma

IntroductionMultiple myeloma is a malignancy of plasma cells with around 6000 new cases per year in the UK. Cyclophosphamide plus prednisolone is considered a standard of care for disease and...

EP08.01-059 Safety, Tolerability and Clinical Activity of Selinexor in Combination with Pembrolizumab in Metastatic Non-small Cell Lung Cancer

Immune checkpoint therapies have revolutionized the therapy of metastatic Non-Small Cell Lung Cancer (mNSCLC), leading to durable therapeutic responses not typically seen with traditional cytotoxic anti-cancer agents. However, primary and acquired resistance to anti-PD-(L)1 therapy impacts the majority of the patients, and new strategies are investigated to prevent or reverse resistance to therapy. Here we present clinical safety and early efficacy data of the combination of Pembrolizumab with a first in class, oral selective inhibitor of nuclear export, Selinexor in mNSCLC.

Anti-Osteoclast Effect of Exportin-1 Inhibitor Eltanexor on Osteoporosis Depends on Nuclear Accumulation of IκBα-NF-κB p65 Complex.

Osteoporosis affects around 200 million people globally, with menopausal women accounting for the bulk of cases. In the occurrence and development of osteoporosis, a key role is played by osteoclasts. Excessive osteoclast-mediated bone resorption activity reduces bone mass and increases bone fragility, resulting in osteoporosis. Thus, considerable demand exists for designing effective osteoporosis treatments based on targeting osteoclasts. Eltanexor (Elt; KPT-8602) is a selective nuclear-export inhibitor that covalently binds to and blocks the function of the nuclear-export protein exportin-1 (XPO1), which controls the nucleus-to-cytoplasm transfer of certain critical proteins related to growth regulation and tumor suppression, such as p53, IκBα [nuclear factor-κB (NF-κB) inhibitor α] and FOXO1; among these proteins, IκBα, a critical component of the NF-κB signaling pathway that primarily governs NF-κB activation and transcription. How Elt treatment affects osteoclasts remains poorly elucidated. Elt inhibited the growth and activity of RANKL-induced osteoclasts in vitro in a dose-dependent manner, and Elt exerted no cell-killing effect within the effective inhibitory concentration. Mechanistically, Elt was found to trap IκBα in the nucleus and thus protect IκBα from proteasome degradation, which resulted in the blocking of the translocation of IκBα and NF-κB p65 and the consequent inhibition of NF-κB activity. The suppression of NF-κB activity, in turn, inhibited the activity of two transcription factors (NFATc1 and c-Fos) essential for osteoclast formation and led to the downregulation of genes and proteins related to bone resorption. Our study thus provides a newly identified mechanism for targeting in the treatment of osteoporosis.

Selinexor inhibits growth of patient derived chordomas in vivo as a single agent and in combination with abemaciclib through diverse mechanisms.

Chordoma is a rare cancer that grows in the base of the skull and along the mobile spine from remnants of embryonic notochord tissue. The cornerstone of current treatments is surgical excision with adjuvant radiation therapy, although complete surgical removal is not always possible. Chordomas have high rates of metastasis and recurrence, with no approved targeted agents. Selinexor and eltanexor are selective inhibitors of nuclear export (SINE) that prevent the karyopherin protein exportin-1 (XPO1) from shuttling its cargo proteins through nuclear pore complexes out of the nucleus and into the cytoplasm. As cancer cells overexpress XPO1, and many of its cargos include tumor suppressor proteins and complexes bound to oncogene mRNAs, XPO1 inhibition can suppress oncogene translation and restore tumor suppressor protein activity in different cancer types. SINE compounds have exhibited anti-cancer activity in a wide range of hematological and solid tumor malignancies. Here we demonstrate the preclinical effectiveness of SINE compounds used as single agents or in combination with either the proteasome inhibitor, bortezomib, or the CDK4/6 inhibitor, abemaciclib, against various patient- derived xenograft (PDX) mouse models of chordoma, which included clival and sacral chordomas from adult or pediatric patients with either primary or metastatic disease, with either differentiated or poorly differentiated subtypes. SINE treatment significantly impaired tumor growth in all five tested chordoma models, with the selinexor and abemaciclib combination showing the strongest activity (tumor growth inhibition of 78-92%). Immunohistochemistry analysis of excised tumors revealed that selinexor treatment resulted in marked induction of apoptosis and reduced cell proliferation, as well as nuclear accumulation of SMAD4, and reduction of Brachyury and YAP1. RNA sequencing showed selinexor treatment resulted in differences in activated and repressed signaling pathways between the PDX models, including changes in WNT signaling, E2F pathways and glucocorticoid receptor signaling. This is consistent with SINE-compound mediated XPO1 inhibition exhibiting anti-cancer activity through a broad range of different mechanisms in different molecular chordoma subsets. Our findings validate the need for further investigation into selinexor as a targeted therapeutic for chordoma, especially in combination with abemaciclib.

Small Molecule Inhibitors of Nuclear Export and the Amelioration of Lupus by Modulation of Plasma Cell Generation and Survival.

To investigate the hypothesis that selective inhibitors of nuclear export (SINE compounds), recently approved for treatment of refractory plasma cell (PC) malignancy, may have potential in the treatment of lupus. Female NZB/NZW mice were treated with the SINE compound KPT-350 or vehicle control. Tissue specimens were harvested and analyzed by flow cytometry, using standard markers. Nephritis was monitored by determining the proteinuria score and by histologic analysis of kidney specimens. Serum anti-double-stranded DNA (anti-dsDNA) levels were measured by enzyme-linked immunosorbent assay, and total numbers of IgG-secreting and dsDNA-specific antibody-secreting cells were assessed by enzyme-linked immunospot assay. KPT-350 abrogated murine lupus nephritis at both early and late stages of the disease and rapidly impaired generation of autoreactive PCs in germinal centers (GCs). SINE compounds inhibited the production of NF-κB-driven homeostatic chemokines by stromal cells, altering splenic B and T cell strategic positioning and significantly reducing follicular helper T cell, GC B cell, and autoreactive PC counts. KPT-350 also decreased levels of cytokines and chemokines involved in PC survival and recruitment in the kidney of lupus-prone mice. Exportin 1, the target of SINE compounds, was detected in GCs of human tonsils, splenic B cells of lupus patients, and multiple B cell subsets in the kidneys of patients with lupus nephritis. Collectively, our results provide support for the therapeutic potential of SINE compounds, via their targeting of several molecular and cellular pathways critical in lupus pathogenesis, including autoantibody production by plasma cells.

Abstract 5314: Selinexor, a selective inhibitor of nuclear export (SINE) compound, enhances the anti-tumor activity of Eribulin in leiomyosarcoma

Abstract Leiomyosarcoma (LMS) is a rare soft tissue sarcoma (STS) that begins in smooth muscle tissue and most often initiates in the abdomen or uterus. Compared with other uterine cancers, uterine LMS is an aggressive tumor associated with poor prognosis and has a high risk of recurrence and death, regardless of stage at presentation. Selinexor is a first-in-class selective inhibitor of nuclear export (SINE) compound that binds covalently to exportin 1, thereby reactivating tumor suppressor proteins and downregulating the expression of oncogenes and DNA damage repair (DDR) proteins. Selinexor has demonstrated preclinical activity in various cancer types, including STS, and is currently in Phase I and II clinical trials for advanced cancers (Marretta et al. 2021). In this study, we evaluated the effects of Selinexor in combination with Dacarbazine, Gemcitabine, Doxorubicin, Pazopanib, Eribulin, and Trabectedin in LMS cell lines. The effects on cell viability were evaluated by treating the LMS cell lines SK-UT1 (p53-mut) and SK-UT1-B (p53 WT) with Selinexor and different chemotherapy combinations. Treatment with these drugs significantly decreased the cell proliferation and survival of SK-UT1 and SK-UT1-B cell lines tested in vitro. However, this effect was enhanced in SK-UT1 cells following treatment in the combination of Selinexor with Eribulin and Doxorubicin. The effects of treatment were also evaluated in mouse xenograft models generated with SK-UT1 cell lines. Treatment with Selinexor combined with Eribulin showed synergistic effects on tumor growth inhibition in SK-UT1 derived xenografts which warrant further investigation of these combinations at the clinical level. Citation Format: Sonam Mittal, Ishaque Pulikkal, Hua Chang, Yosef Landesman, John Charlson, Sunila Pradeep. Selinexor, a selective inhibitor of nuclear export (SINE) compound, enhances the anti-tumor activity of Eribulin in leiomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5314.

Abstract 4195: Evaluation of the anti-myeloma effects of high and metronomic selinexor alone and in combination with duvelisib in vitro and in vivo

Abstract Introduction: Selinexor (Karyopharm Therapeutics) is an FDA-approved oral selective inhibitor of nuclear export (SINE) compound. It specifically blocks XPO1 enforcing the nuclear retention of tumor suppressor proteins restoring their anti-cancer functions. It also attenuates the phosphoinositide-3 kinase (PI3K)-AKT pathway by activating PTEN. Although activation of PI3K signaling is often detected in hematological malignancies, there are no data regarding the combination of selinexor with the PI3K inhibitor duvelisib for MM treatment. Thus, we evaluated the anti-myeloma effects of selinexor in combination with duvelisib in vitro and also studied alternative schedules of selinexor with dexamethasone in vivo using our MM xenograft models LAGκ-2. Methods: The human MM cell line U266 was obtained from ATCC. Primary MM tumor cells were isolated from MM patients’ bone marrow (BM) aspirates. Cell viability was quantified using the MTS cell proliferation assay. For the in vivo studies, the human myeloma xenograft LAGκ-2 was surgically implanted into SCID mice. Selinexor was administered via oral gavage at 2.5 mg/kg 5x per week, 5 mg/kg 4x per week on consecutive days, or 10 mg/kg 2x per week with one day between treatments. Dexamethasone was administered via intraperitoneal injection at 4 mg/kg 2x per week except the vehicle control. Results and Discussion: MTS assays showed selinexor induced concentration dependent inhibition of cell viability/proliferation in the MM cell line MM1s at 0.1, 0.4 and 1.6 μM. Selinexor alone at 0.2 μM reduced cell proliferation of primary MM tumor cells obtained from BM mononuclear cells (MCs) from a patient with progressive disease. We next examined cell viability in the presence of selinexor and duvelisib. MM1s or fresh BM mononuclear cells were incubated with a fixed concentration of selinexor (0.1μM) with increasing concentrations of duvelisib (1.5 μM -25 μM) for 48 h. The results showed that duvelisib enhanced the cytotoxic effects of selinexor in a concentration dependent manner. We also evaluated dosing and scheduling of selinexor and dexamethasone in vivo using SCID mice bearing LAGκ-2 MM xenografts. When selinexor was combined with dexamethasone, lower more frequent dosing showed greater inhibition of tumor growth than mid-range and higher less frequent dosing of this SINE. This study illustrates that the combination of selinexor and duvelisib showed enhanced cytotoxic effects in vitro compared with single agent treatment, and we will further evaluate the anti-MM effects of selinexor in combination with duvelisib in vivo using our human MM xenograft models. These studies suggest that the combination of a SINE and PI3K inhibitor may be effective for MM treatment. Citation Format: Haiming Chen, Stacy Behare, Mingjie Li, Marissa Goldwater, Ava Hekmati, Jasmin Cao, Rocky Levin, Ning Xu, James Berenson. Evaluation of the anti-myeloma effects of high and metronomic selinexor alone and in combination with duvelisib in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4195.

Abstract 5330: Nuclear protein export inhibitor selinexor chemotherapy combination for pancreatic cancer therapy

Abstract Background: The majority of pancreatic ductal adenocarcinoma (PDAC) patients experience disease progression after Gemcitabine-nab-Paclitaxel (GemPac) treatment indicating the need for more effective combination therapies for this highly recalcitrant disease. Earlier we showed that nuclear exporter protein exportin 1 (XPO1) is a valid therapeutic target in PDAC and selective inhibitor of nuclear export (SINE) selinexor (Sel), synergistically enhances the efficacy of GemPac in pancreatic cancer cells, spheroids, patient derived tumors and showed evaluable response in PDAC patients in a Phase I study. Here we investigated the mechanisms of this synergy utilizing PDAC cellular models in vitro and LSL-Kras G12D/+; Trp53 fl/+; Pdx1-Cre (KPC) mouse model. Methods: We used single-nuclei RNA sequencing in KPC tumors, and poly A RNA sequencing in PDAC cells post sel-Gem-Pac treatment. Prioritized sn-seq and RNA-seq identified molecules were validated in in vitro or in the PDAC patient samples through siRNA mediated silencing, quantitative gene expression, cytotoxicity and related assays. Results: In KPC model, selinexor-GemPac caused statistically significant enhancement in survival compared to controls (p less than 0.05). Molecular analysis of residual KPC tumors showed re-organization of tumor stromal architecture, suppression of proliferation and nuclear retention of tumor suppressors. Histopathological analysis for Ki67 suggests comparatively lower rate of proliferation and enhanced nuclear accumulation of FOXO3a in the treated mice. Loosening of stroma and lowering of collagen fiber is also evident in treated mice from Picrosirius and Masson’s trichrome staining. Additionally, the KPC derived primary tumor cells showed reduced colony formation upon combination treatment. Sn-seq showed reduction in tumor cell heterogeneity (less cell clusters based on gene expression), CDK8, CD44 and Camk1d stem cell and EMT related genes alongside significant alterations in mitochondrial signaling after combination treatment. In cellular models, GO and GSEA analyses of RNA-seq data predicted DNA templated regulation of transcription and DNA replication associated genes in Sel or Sel-GemPac mediated growth inhibition. The top downregulated genes including drug resistant related gene PFN1 and HSP90 identified in Sel or Sel-GemPac treated PDAC cells from RNA-seq data were validated using RNAi and confirmed their role in synergy. Conclusions: Taken together Selinexor in combination with Gemcitabine-nab-Paclitaxel enhanced the survival of KPC mice through inhibition of well-connected tumor promoting molecules resulting in broad penetration in PDAC supporting signaling. A phase II study involving selinexor-gemcitabine combination in patients with metastatic PDAC is ongoing. Citation Format: Md. Hafiz Uddin, Sahar Bannoura, Yiwei Li, Husain Y. Khan, Amro Aboukameel, Mohammed N. Al-Hallak, Rafic Beydoun, Steve Kim, Yosef Landesman, Ramzi M. Mohammad, Anthony Shields, Asfar S. Azmi. Nuclear protein export inhibitor selinexor chemotherapy combination for pancreatic cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5330.

Abstract 5536: Selinexor inhibits lymphoma-leukemia tumor progression directly and through activation of anti-cancer immune response

Abstract Background: Selinexor is a Selective Inhibitor of Nuclear Export (SINE) compound that binds covalently to Exportin 1 (XPO1) and inhibits its nuclear export function, resulting in nuclear accumulation of tumor suppressor proteins (TSPs) including p53, pRB, and IκB-α. Selinexor was evaluated for improved survival in tumor-bearing mice with hematological malignancies using EL-4 (T cell lymphoma/leukemia) and C1498 (Acute myeloid leukemia) models. We hypothesized that selinexor increases survival by directly inducing tumor cell apoptosis and blocks immunosuppressive effects of myeloid derived suppressor cells (MDSCs). Methods: Mice were injected with 2×106 EL-4 or 1×106 C1498 cells intravenously followed by oral treatment with saline, vehicle, or different selinexor dosing schedules (5 mg/kg weekly (5), twice weekly on Wed and Fri (5 d1/3) or Mon and Fri (5 d1/5) or 10 mg/kg weekly (10). Selinexor was given by gavage. To examine the effect of selinexor on immune cells during tumor growth, Tumor bearing mice treated with vehicle or selinexor were euthanized at day 14 after tumor injection. Spleens were removed, single cell suspensions were isolated and the percentage of immune cells including MDSCs, regulatory T cells (Tregs) and the production of interferon gamma (IFN-γ) were analyzed by flow cytometry. Tumor bearing mice were monitored for survival in separate experiments. Results: Selinexor at the weekly 5 d1/3 and the 10 dosing significantly increased survival in mice injected with either tumor line. Whereas weekly 5 or 5 d1/5 dosing did not significant affect survival. Selinexor at weekly 10 dosing significantly reduced the population of polymorphonuclear MDSCs (PMN-MDSCs). Selinexor at 10, 5 d1/3 and 5/1/5 weekly dosing significantly increased IFN-γ production by CD8+ and CD4+ T cells when compared to vehicle. There were no differences in Tregs populations. Conclusions: These data demonstrate that different selinexor dosing and schedules have differential efficacy on survival in murine models of leukemia/lymphoma. Selinexor effects are dose and schedule dependent. We found that in contrast to the split dosing, the single weekly high dose of selinexor reduced splenic PMN-MDSC accumulation. While both dosing schedules increased the percentage of IFN-γ positive T cells in tumor bearing mice suggesting that selinexor’s anti-cancer activity is not limited only to direct cytotoxic or cytostatic tumor cells. These data support the concept that once weekly selinexor, at a higher dose (10 mg/kg (approximately 30 mg/m2) which is comparable to the clinical dose schedule (50-60 mg weekly) can modulate the immune system to target cancer cells and could be used alone or in combination with other immunotherapies to enhance the immune system. Citation Format: Hemn Mohammadpour, Yosef Landesman, Philip McCarthy. Selinexor inhibits lymphoma-leukemia tumor progression directly and through activation of anti-cancer immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5536.

Enhancement of MDM2 inhibitory effects through blocking nuclear export mechanisms in ovarian cancer cells

Over 90% of ovarian cancer cells exhibit p53 mutations or inactivation. In addition, p53 is exported outside of the nucleus by exportin-1 (XPO1), a protein that mediates the nuclear export of several cancer suppressor proteins. Overexpression of XPO1 is associated with resistance to chemotherapy, leading to poor prognosis in various cancers. The MDM2 inhibitor, RG-7388, is a known reactivator of p53 and has been tested with high interest as a therapeutic agent for cancer treatment. In addition, Selinexor, which is a second-generation selective inhibitor of nuclear export (SINE), is known to cause an accumulation of p53 in the nucleus and is also being explored as a therapy potentiating agent in combination treatments. This study was conducted to assess the efficacy of RG-7388 in combination with Selinexor for treating ovarian cancer. A combination of Selinexor and RG-7388 treatments was able to reduce the cell viability compared to individual treatments. In addition, the combination treatment revealed significant up-regulation of several cancer suppressor proteins in the whole lysate, cytoplasm, and nucleus. Finally, our results confirm that the combination of Selinexor with RG-7388 can induce a caspase-mediated apoptotic mechanism via up-regulation of p53 and p21.

A phase 1, open-label, dose-escalation study of selinexor plus ruxolitinib in patients with treatment-naïve myelofibrosis.

7060 Background: Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by unregulated, clonal proliferation of a hematopoietic stem cells in the bone marrow and is commonly associated with gene mutations in JAK2, CALR, or MPL. Front-line therapy may include the JAK1/2 inhibitor ruxolitinib (RUX), resulting in spleen volume reductions and improvement in MF-related symptoms. Despite the therapeutic effect of RUX, most patients (pts) eventually progress and thus novel combinations are required to increase responses and delay progression. Selinexor (SEL) is an oral selective inhibitor of nuclear export (SINE) compound, specifically inhibiting exportin-1 (XPO1), and currently approved for treatment of multiple myeloma and diffuse large B-cell lymphoma. Significant activity of SEL in combination with RUX has been shown in preclinical studies, and SEL monotherapy in MF refractory to JAK inhibitors demonstrated robust clinical activity and a tolerable safety profile (NCT03627403). Here, we present the initial results of a phase 1 dose escalation study of the combination SEL and RUX in treatment-naïve MF. Methods: The ongoing multicenter, open-label, Phase 1/2 study (NCT04562389) is evaluating the efficacy and safety of SEL plus RUX in JAKi-naïve MF pts. Two dose levels of SEL were evaluated, 40mg and 60mg once-weekly (QW) plus RUX twice daily (BID) as per label in 28-day cycles, using a 3+3 design. All pts received 5-HT3 antagonist for nausea prophylaxis. Primary objectives include safety, maximum tolerated dose (MTD), recommended Phase 2 dose (RP2D), and preliminary efficacy. Secondary objectives include spleen, symptom, and anemia response, and OS. Results: As of 31 Jan 2022, 10 pts have been dosed in 2 dose levels (40mg (n = 3), and 60mg (n = 7) SEL QW plus RUX). RUX starting dose was 20 mg in 8 pts, 15 mg in one patient and 10 mg in one patient. The median age was 64 (range 45-76). Seven pts had primary MF and 3 had post-ET MF. DIPSS risk category was int-1 (n = 4), int-2 (n = 4) and high risk (n = 2). No dose limiting toxicities have been reported at either dose levels of SEL. One patient required dose interruption due to dizziness and later discontinued treatment due to new onset of atrial fibrillation and pulmonary hypertension (unrelated to SEL and RUX) after 5 months of therapy. All other pts remain on study. There was no grade 3 neutropenia or thrombocytopenia observed. Hemoglobin level was maintained without any significant worsening. The most common treatment-emergent adverse event was low grade nausea (30%). All pts experienced improvement in their white blood cell count. Four of the first 5 evaluable pts demonstrated ≥35% spleen volume reduction at week 12. Conclusions: The combination of SEL and RUX has been well-tolerated and with a manageable side effect profile. No dose limiting toxicities were observed in pts with treatment-naïve MF in cohort 1 of once weekly oral SEL 40 and 60 mg with RUX. Clinical trial information: NCT04562389.

Digital monitoring and assessments in patients with glioblastoma.

2045 Background: Glioblastoma (GBM) is an aggressive primary tumor with poor prognosis and survival. Patients (pts) experience debilitating symptoms that have a negative effect on quality of life (QoL). A multidisciplinary approach is necessary to facilitate the reduction of morbidity, preserve QoL, and maximize benefits of treatment. Selinexor (SEL) is a first-in class, oral, selective inhibitor of nuclear export that blocks exportin 1 approved for use in multiple myeloma and diffuse large B-cell lymphoma and has shown activity in GBM. Digital measurements in the KING study through wearable sensors and other devices capture actionable daily data at home for improved care, symptom management, and QoL, are reported here. Methods: XPORT-GBM-029 (NCT04421378) is an ongoing phase 1 dose finding study followed by an open-label randomized phase 2, 5-arm trial to evaluate SEL in combination with standard therapies for newly diagnosed and recurrent GBM (n = 350): radiation+SEL /radiation and temozolomide; radiation and temozolomide±SEL; lomustine±SEL; bevacizumab±SEL; tumor treating field±SEL. The study is conducted at 18 sites in the US and Canada. GBM progression is assessed by standard clinical and imaging as well as QoL measurements by novel digital tools. Four parameters to determine the impact on QoL (cognitive function, lateralization, fatigue, sleep) are measured remotely by smartwatch and smartphone to continuously measure activity and sleep, and to complete a cognitive battery at baseline and before each MRI. Results: To date, pts wearing the smartwatch had higher compliance during the day for activity and gait measures compared to night for sleep measures. Younger pts had better compliance. Over the course of SEL treatment, changes were observed in balance (characterized by double support % and walking asymmetry) and activity level (characterized by step count and walking distance). Of the pts who participated in the cognitive battery (CANTAB) tests, 2 pts had a minor change in cognition measures including psychomotor and processing speed, episodic and spatial working memory, and executive function after 2 SEL treatment cycles. Overall, the CANTAB measures are stable, which align with the mRANO (MRI) results. The correlation between the CANTAB cognition measures and MRI data will be evaluated once more clinical data become available. Ongoing analyses will apply machine learning and statistical tools to determine potential correlations between digital and clinical data, such as physical examinations, AEs, Karnofsky scores, mRANO, NANO, KPS, and PRO QoL questionnaires. Conclusions: This is the first demonstration of digital measurement feasibility in a longitudinal study of pts with GBM. Digital measurements for pts with GBM could provide information on the impact of SEL-based treatment and functional outcomes in clinical trials and increase communication between clinicians and pts, thereby improving QoL and care management. Clinical trial information: NCT04421378.

A Three-Gene Signature Predicts Response to Selinexor in Multiple Myeloma.

Selinexor is the first selective inhibitor of nuclear export to be approved for the treatment of relapsed or refractory multiple myeloma (MM). Currently, there are no known genomic biomarkers or assays to help select MM patients at higher likelihood of response to selinexor. Here, we aimed to characterize the transcriptomic correlates of response to selinexor-based therapy. We performed RNA sequencing on CD138+ cells from the bone marrow of 100 patients with MM who participated in the BOSTON study, followed by differential gene expression and pathway analysis. Using the differentially expressed genes, we used cox proportional hazard models to identify a gene signature predictive of response to selinexor, followed by validation in external cohorts. The three-gene signature predicts response to selinexor-based therapy in patients with MM in the BOSTON cohort. Then, we validated this gene signature in 64 patients from the STORM cohort of triple-class refractory MM and additionally in an external cohort of 35 patients treated in a real-world setting outside of clinical trials. We found that the signature tracks with both depth and duration of response, and it also validates in a different tumor type using a cohort of pretreatment tumors from patients with recurrent glioblastoma. Furthermore, the genes involved in the signature, WNT10A, DUSP1, and ETV7, reveal a potential mechanism through upregulated interferon-mediated apoptotic signaling that may prime tumors to respond to selinexor-based therapy. In this study, we present a present a novel, three-gene expression signature that predicts selinexor response in MM. This signature has important clinical relevance as it could identify patients with cancer who are most likely to benefit from treatment with selinexor-based therapy.

Prognostic and therapeutic significance of XPO1 in T-cell lymphoma

T-cell lymphoma (TCL) is a highly heterogeneous group of invasive non-Hodgkin lymphoma with adverse prognosis and limited treatment options. The relationship between TCL and Exportin-1 (XPO1), a major nuclear export receptor, has not been established yet. We here investigated the prognostic role and therapeutic implication of XPO1 in TCL. We analyzed XPO1 expression in a cohort of 69 TCL tumors and found that XPO1 was over-expressed in 76.8% of TCL and correlated with decreased progression-free survival (PFS) and overall survival (OS). In vitro treatment of TCL cell lines with KPT-8602, the second-generation selective inhibitor of nuclear export (SINE), inhibited XPO1 expression and showed significant anti-proliferative, cell-cycle arrest and pro-apoptotic efficacy. In mechanism, KPT-8602 restored the localization of cytoplasmic FOXO3A, p27, p21, IκBα and PP2A into the nucleus, leading to AKT and NF-κB deactivation. Our data demonstrate for the first time that XPO1 could be an unfavorable prognostic factor for TCL, and provide a rationale for further investigation of the efficacy of KPT-8602 in TCL patients.

Selinexor and COVID-19: The Neglected Warden.

A novel severe acute respiratory distress syndrome coronavirus type 2 (SARS-CoV-2) has been confirmed as the cause of the global pandemic coronavirus disease 2019 (COVID-19). Different repurposed drugs have been trialed and used in the management of COVID-19. One of these agents was the anti-cancer Selinexor (SXR). SXR is an anti-cancer drug that acts by inhibition of nuclear exportin-1 (XPO1), which inhibits transport of nuclear proteins from the nucleus to the cytoplasm, leading to the induction of cell-cycle arrest and apoptosis. XPO1 inhibitors had antiviral effects, mainly against respiratory syncytial virus (RSV) and influenza virus. SXR inhibits transport of SARS-CoV-2 nuclear proteins to the cytoplasm with further inhibition of SARS-CoV-2 proliferation. SXR has the ability to prevent the development of a cytokine storm in COVID-19 by inhibiting the release of pro-inflammatory cytokines with the augmentation release of anti-inflammatory cytokines. In conclusion, SARS-CoV-2 infection is linked with activation of XPO1, leading to the triggering of inflammatory reactions and oxidative stress. Inhibition of XPO1 by Selinexor (SXR), a selective inhibitor of nuclear export (SINE), can reduce the proliferation of SARS-CoV-2 and associated inflammatory disorders. Preclinical and clinical studies are warranted in this regard.

KPT330 improves Cas9 precision genome- and base-editing by selectively regulating mRNA nuclear export

CRISPR-based genome engineering tools are associated with off-target effects that constitutively active Cas9 protein may instigate. Previous studies have revealed the feasibility of modulating Cas9-based genome- and base-editing tools using protein or small-molecule CRISPR inhibitors. Here we screened a set of small molecule compounds with irreversible warhead, aiming to identifying small-molecule modulators of CRISPR-Cas9. It was found that selective inhibitors of nuclear export (SINEs) could efficiently inhibit the cellular activity of Cas9 in the form of genome-, base- and prime-editing tools. Interestingly, SINEs did not function as direct inhibitors to Cas9, but modulated Cas9 activities by interfering with the nuclear export process of Cas9 mRNA. Thus, to the best of our knowledge, SINEs represent the first reported indirect, irreversible inhibitors of CRISPR-Cas9. Most importantly, an FDA-approved anticancer drug KPT330, along with other examined SINEs, could improve the specificities of CRISPR-Cas9-based genome- and base editing tools in human cells. Our study expands the toolbox of CRISPR modulating elements and provides a feasible approach to improving the specificity of CRISPR-Cas9-based genome engineering tools.

Guidance for Use and dosing of Selinexor in Multiple Myeloma in 2021: Consensus From International Myeloma Foundation Expert Roundtable

Selinexor is a first in class selective inhibitor of nuclear export (SINE), blocks exportin 1 (XPO1), a protein transporter, that among other actions, shuttles cargo proteins such as tumor suppressor proteins (TSPs), the glucocorticoid receptor (GR), and oncoprotein messenger RNAs (mRNAs) across the nuclear membrane to cytoplasm. By blocking XPO1, selinexor facilitates nuclear preservation and activation of TSPs, and prevents mRNA translation of the oncoproteins leading to induction of apoptosis. The therapeutic value of selinexor in combination with dexamethasone has been successfully demonstrated in treating relapsed and/or refractory myeloma (RRMM), leading to the Food and Drug Administration (FDA) approval of selinexor in combination with dexamethasone in 2019 for the treatment of adult patients with RRMM who received at least 4 prior therapies and whose disease is refractory to at least 2 proteasome inhibitors, at least 2 immunomodulatory agents, and an anti-CD38 monoclonal antibody (mAb) – a pentarefractory myeloma. More recently, selinexor in combination with bortezomib and dexamethasone was approved by the FDA in December 2020, based on the BOSTON study among RRMM patients who had received at least one prior line of therapy. With more available safety and efficacy data supporting the increased interval between dosing of selinexor (and lesser cumulative weekly dosing) and schedule, contrary to the originally approved dose of 160 mg per week, the supportive care guidelines needed to be revisited. The current manuscript summarizes the supportive care solutions with weekly dosing of selinexor and identifies the ideal potential patient for selinexor treatment.