Selinexor In Combination Research Articles

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.

Phosphoproteomics of primary AML patient samples reveals rationale for AKT combination therapy and p53 context to overcome selinexor resistance.

SummaryAcute myeloid leukemia (AML) is a heterogeneous disease with variable patient responses to therapy. Selinexor, an inhibitor of nuclear export, has shown promising clinical activity for AML. To identify the molecular context for monotherapy sensitivity as well as rational drug combinations, we profile selinexor signaling responses using phosphoproteomics in primary AML patient samples and cell lines. Functional phosphosite scoring reveals that p53 function is required for selinexor sensitivity consistent with enhanced efficacy of selinexor in combination with the MDM2 inhibitor nutlin-3a. Moreover, combining selinexor with the AKT inhibitor MK-2206 overcomes dysregulated AKT-FOXO3 signaling in resistant cells, resulting in synergistic anti-proliferative effects. Using high-throughput spatial proteomics to profile subcellular compartments, we measure global proteome and phospho-proteome dynamics, providing direct evidence of nuclear translocation of FOXO3 upon combination treatment. Our data demonstrate the potential of phosphoproteomics and functional phosphorylation site scoring to successfully pinpoint key targetable signaling hubs for rational drug combinations.

Abstract 5519: Selinexor synergizes with anti-PD-1 antibody and inhibits tumor growth and metastasis in syngeneic mouse models of KRAS mutant colorectal cancer

Abstract Background: Colorectal cancer (CRC) is the second leading cause of cancer related death. In approximately half of all CRC cases, oncogenic KRAS mutations underlie poor prognosis and drug resistance. A previous multi-genomic analysis of 4,725 biological processes with 106 human non-small-cell lung cancer cells identified nuclear transport machinery as the sole process selectively required for the survival of KRAS mutant cells. Selinexor is a clinically approved oral inhibitor of nuclear export protein Exportin 1 (XPO1/CRM1). In preclinical studies, selinexor demonstrated robust synthetical lethality with native or engineered oncogenic KRAS both in vitro and in vivo. Clinical activity of selinexor monotherapy was observed in CRC patients with various KRAS oncogenic mutations (Razak 2016 JCO). We performed preclinical studies to evaluate the effectiveness of selinexor and the anti-PD-1 antibody RMP1-14 in syngeneic mouse models of KRAS mutant CRC. Methods: Two syngeneic CT-26 KRAS mutant CRC mouse models were tested: 1) metastasis model with intra-hepatically injected CT-26 cells expressing luciferase (8 mice per group); and 2) subcutaneous model with CT-26 injected into the left flank (10 mice per group). Mice were allocated to four groups: vehicle control, selinexor (15 mg/kg, PO, once weekly), RMP1-14 (300 µg/mouse, IP, once weekly), or the combination of selinexor and RMP1-14. Tumor progression and body weight of test mice were monitored throughout the experiment. Tumor samples and plasma were collected at the end of the study for further analysis. Results: Both selinexor and RMP1-14 demonstrated single agent activity against KRAS mutant CRC in the two mouse models relative to controls. In the metastasis model, tumor growth inhibition (TGI) at Day 21 was 63.5% (p=0.0001) for selinexor and 68.9% (p<0.0001) for RMP1-14. The combination of selinexor and RMP1-14 significantly inhibited tumor growth and metastasis with a TGI of 98.9% (p<0.0001). No tumors were detected in two mice from the combination group at the end of the study. A similar trend was observed in the subcutaneous xenograft models, at Day 17, TGIs for selinexor, RMP1-14 and combination treatment were 17.6% (p=0.0921), 26.9% (p=0.0059) and 70.4% (p<0.0001), respectively. Conclusions: Synergistic anti-cancer activity of selinexor and anti-PD-1 antibody in KRAS mutant CRC mouse models warrants further clinical investigation. Citation Format: Hua Chang, Leah Henegar, Christopher J. Walker, Trinayan Kashyap, Marie Maloof, Feng Wang, Kathleen Martyn, Shira Orr, Michael G. Kauffman, Sharon Shacham, Yosef Landesman. Selinexor synergizes with anti-PD-1 antibody and inhibits tumor growth and metastasis in syngeneic mouse models of KRAS mutant colorectal cancer [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 5519.

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 4067: Combination venetoclax and selinexor effective in relapsed refractory multiple myeloma with translocation t(11;14)

Abstract Translocation t(11;14) positive multiple myeloma (MM) is sensitive to venetoclax, yet the drug lacks FDA approval in MM. Selinexor is an inhibitor of nuclear exporter XPO1 and is approved in relapsed refractory MM. We recently analyzed RNA-seq from 859 MM patient samples (MMRF CoMMpass study) and compared them to healthy bone marrow samples (GSE114922). After correcting for batch effects, differential gene expression analysis found apoptosis and cell cycle regulation amongst the top upregulated gene pathways in MM. We therefore hypothesized that MM would be sensitive to the combination of the pro-apoptotic drug, venetoclax, and selinexor, which causes cell cycle arrest. Using a panel of 8 MM cell lines (U266-B1, KMS12BM, SKMM2, RPMI-8226, LP1, OPM2, KMS12PE, and NCIH929), we performed cell viability assays in increasing concentrations of selinexor, venetoclax, and a combination of the two drugs at 72 hours. Overall, the combination showed synergy in MM cell lines but strikingly, cell lines that possessed t(11;14) were more sensitive to the drug combination and showed enhanced synergy compared to the non-t(11;14). Average Bliss model synergy score were 0.5 in non-t(11;14) and 10.2 in t(11;14) MM cells (>10 indicates synergistic effects and <-10 indicates antagonistic drug effects). To better understand molecular mechanisms underlying the observed synergistic effect in t(11;14), we performed western blot analysis in these cell lines treated with selinexor, venetoclax, the combination, or DMSO control for 24 hours. We measured protein levels of Cyclin D1, which is overexpressed in t(11;14) and a cargo of XPO1. We confirmed Cyclin D1 overexpression in t(11;14) cells lines but not in non-t(11;14) cells. Cyclin D1 levels decreased with selinexor, and the reduction was enhanced by adding venetoclax. Additionally, we measured levels of XPO1, p53, MCL-1, and p65, which we have previously shown to be altered by selinexor treatment. While venetoclax monotherapy caused increased MCL-1 expression, this was abrogated by combining with selinexor and the effects were statistically more significant in t(11;14) cell lines. Concurrently, two patients with relapsed, refractory t(11;14) MM and disease progression after multiple lines of therapy were treated with venetoclax; however, after initial response, they developed resistance and progressive disease. Based off our preclinical results, selinexor was added to venetoclax and recaptured responses (VGPR and MR, respectively) suggesting a beneficial effect of the combination over single agent venetoclax. To our knowledge, this is the first report of patients with MM treated with the combination of selinexor and venetoclax. Further clinical evaluation of this combination in t(11;14) MM is planned and samples will be collected to better understand the mechanistic correlation between XPO1, BCL2/MCL-1, and Cyclin D1 levels and response. Citation Format: Sana Chaudhry, Nina Nguyen, Rimpi Khurana, Tulasigeri M. Totiger, Skye Montoya, Jumana Afaghani, Terrence Bradley, Francesco Maura, Dickran Kazandjian, Jennifer Chapman, Stephan Schürer, Ola Landgren, James Hoffman, Justin Taylor. Combination venetoclax and selinexor effective in relapsed refractory multiple myeloma with translocation t(11;14) [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 4067.

Abstract 3594: Exportin 1 inhibition as a therapeutic strategy for small cell lung cancer

Abstract Small cell lung cancer (SCLC) is an aggressive disease characterized by early metastasis and exceptional lethality, comprising 13% of all lung cancer cases. With few treatment options, typically resulting in only transient responses, SCLC is responsible for approximately 250,000 deaths globally per year. The backbone of SCLC treatment over the past several decades has been platinum-based doublet chemotherapy, with the recent addition of immunotherapy to first-line chemotherapy showing limited benefit in a small subset of patients. Major hurdles to improving SCLC treatment include development of rapid chemoresistance and ineffective second line therapies. The identification of more durably effective therapeutic strategies is a major unmet clinical need. Here, we performed an in vitro CRISPR screen in SCLC cell lines from all major SCLC subtypes, including short-term cultured cells from patient-derived xenografts (PDXs), to identify potential therapeutic targets to enhance sensitivity to chemotherapy. Candidate hits were validated genetically and pharmacologically with in vitro synergy assays, in vivo clonal competition assays and pharmacologic assessments in PDX models. Signaling pathways were studied by RNA sequencing and western blot, and toxicity studies were performed in vivo to assess the safety of the agents at pharmacologically effective doses. We performed immunohistochemistry (IHC) to assess expression of candidate targets in tissue microarrays (TMAs). Our CRISPR screen revealed the nuclear exporter exportin 1 (encoded by the XPO1 gene) as a promising target sensitizing to chemotherapy, independently of the SCLC subtype. We found that XPO1 mRNA expression was higher in SCLC than in any other solid tumor or hematological malignancy, and demonstrated consistently high protein expression by IHC in clinical TMAs. A potent and selective exportin 1 inhibitor, selinexor, is approved for use in hematological malignancies. Combination of selinexor with cisplatin or irinotecan demonstrated synergy in vitro and efficacy in vivo in an array of chemonäive and chemoresistant SCLC PDXs, including all major SCLC subtypes. The combinations were well tolerated in mice. The chemo-sensitizing effects of selinexor were associated with suppression of chemotherapy-induced AKT activation. In conclusion, exportin 1 inhibition strongly enhances sensitivity of SCLC tumors to cisplatin and irinotecan, used in first line and second line treatment of SCLC tumors, respectively, and these effects are independent of the SCLC subtype. These results provide preclinical rationale for the combination of selinexor with cisplatin or irinotecan in naïve and relapsed SCLC. The clinical availability of selinexor will allow rapid clinical translation of these results in a disease setting with extremely limited therapeutic options. Citation Format: Alvaro Quintanal-Villalonga, Hirokazu Taniguchi, Yuan Hao, Andrew Chow, Yingqian A. Zhan, Fathema Uddin, Viola Allaj, Parvathy Manoj, Nisargbhai S. Shah, Umesh K. Bhanot, Juan Qiu, Elisa de Stanchina, Richard P. Koche, Triparna Sen, John T. Poirier, Charles M. Rudin. Exportin 1 inhibition as a therapeutic strategy for small cell lung cancer [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 3594.

Abstract 853: The biological role and mechanisms of XPO1 R749Q mutation in colon cancer

Abstract Exportin-1 (XPO1) is known to be overexpressed or mutated in several cancer types. XPO1 is the target of selinexor, which has received approval in hematologic cancers but not in solid tumors. We recently performed a large-scale genomic analysis of 42,793 patients with cancer spanning 322 cancer types (Taylor et. al. Cancer Discovery 2019). We identified a highly statistically significant hotspot mutation in XPO1 R749Q occurring mainly in colorectal cancer patients. We have generated 2 different isogenic colorectal cancer cell lines bearing the XPO1 R749Q mutation (HCT116 and LS174T) using CRISPR-CAS9. We observed that in vitro and in vivo, these cell lines did not reveal a role for XPO1 R749Q on cell growth and proliferation. A chemical compound library screen of >200 FDA-approved cancer therapies revealed a strong therapeutic resistance of XPO1 R749Q cells relative to wildtype (XPO1 WT) cells, specifically to chemotherapies used in the treatment of colon cancer. However, XPO1 R749Q remained sensitive to inhibition with the selective XPO1 inhibitor selinexor. Mass spectrometry analysis of nuclear and cytoplasmic fractionated proteins revealed XPO1 R749Q mutant cells had increased export of proteins from the nucleus compared to XPO1 WT cells. Upon ionizing radiation or chemotherapy, XPO1 R749Q cells had less DNA damage as measured by comet assay and γ-H2Ax immunofluorescence. XPO1 R749Q cells are resistant to chemotherapy but respond to selinexor in vitro. Selinexor effectively blocked nuclear export of canonical cargoes of XPO1 in XPO1 R749Q and XPO1 WT cells. The combination of selinexor and irinotecan showed high levels of synergy in vitro. In vivo observations in mice xenografted with XPO1 R749Q mutant HCT116 cells showed moderate tumor response to selinexor or irinotecan monotherapies but prolonged tumor responses to combination therapy. Single-cell intracellular signaling protein analysis using the Isoplexis platform discovered increased mTOR signaling in the XPO1 R749Q vs. WT cells. Western blot validation confirmed increased mTOR signaling in XPO1 R749Q mutants. In conclusion, our current study sheds novel insights into therapeutic targeting of cancers where XPO1 mutations occur, such as colorectal cancer. Specifically, these mutations confer resistance to DNA-damaging therapies such as chemotherapy and radiation; however, they may predict for sensitivity to targeted agents such as XPO1 inhibition. We have generated unique genetic models for study of XPO1 that are currently lacking. Our study established the biological and mechanistic consequences of XPO1 R749Q mutations in cancer, thereby having a significant positive impact on the treatments of patients with cancer. Further work is ongoing for the identification of cargo proteins transported by mutated XPO1 that connect the effects of XPO1 R749Q mutation on nuclear export to response to DNA damage, mTOR signaling and XPO1 inhibition in tumors in vitro and in vivo. Citation Format: Tulasigeri M. Totiger, Monika Chojnacka, Jumana Afaghani, Sana Chaudhry, Skye Montoya, Maurizio Affer, Justin Taylor. The biological role and mechanisms of XPO1 R749Q mutation in colon cancer [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 853.

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 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.

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.

Phase Ib trial of selinexor (SEL) in combination with nivolumab (NIVO) alone or nivolumab plus ipilimumab (NIVO+IPI) in patients (pts) with advanced malignancies: The renal cell carcinoma (RCC) experience.

4551 Background: SEL is a first-in-class nuclear exportin 1 inhibitor, which blocks the transport of several proteins involved in cancer-cell growth from the nucleus to the cytoplasm. A syngeneic RENCA mouse model showed that SEL combined with checkpoint blockade resulted in increased effector and activated T cells, and NKT cells and reductions in myeloid cells and Tregs. We hypothesized that SEL+NIVO and SEL+NIVO+IPI are well tolerated and improve the overall response rate (ORR) observed with anti-PD1/CTLA-4. Methods: NCT02419495 is an open label, single center phase IB study of SEL with multiple standard chemotherapy or immunotherapy regimens in pts with advanced malignancies using 3 + 3 design in dose escalation. For SEL+NIVO+IPI, SEL was 60 mg (N = 4) or 80 mg (N = 6) given P.O. weekly with NIVO 3 mg/kg x 4 cycles then 480 mg Q4W plus IPI 1 mg/kg Q3W for 4 cycles only. For SEL+NIVO, SEL was 40 mg twice a week (N = 8), or 60 mg twice a week (N = 11) given with NIVO 240 mg Q2W or 480 mg Q4W. Primary objective was to establish the safety and tolerability of SEL+NIVO and SEL+NIVO+IPI. Secondary objectives included ORR and progression free survival (PFS). Results: 29 pts with RCC (25 males) were enrolled (table), including 3 pts with nonclear cell RCC (nccRCC), with a median age of 64 years (IQR 56-69). 21 patients (72%) had prior systemic therapies. Most common SEL or NIVO/IPI treatment-related ≥ grade (G) 3 adverse events (AEs) included endocrine disorders (N = 3), hyponatremia (N = 3), leukopenia (N = 3), transaminitis (N = 3), thromboemobolic events (N = 2), asymptomatic lipase increased (N = 2), anemia (N = 1), pneumonitis (N = 1), nephritis (N = 1), colitis (N = 1), fatigue (N = 1). Two pts discontinued therapy due to AEs (G3 pneumonitis from SEL+NIVO+IPI and G3 transaminitis from SEL+NIVO, respectively). At a median follow up of 17.5 months, 5 (17%) pts achieved a PR, and 17 (59%) achieved a stable disease (SD). The median PFS for the entire cohort was 17.5 months (SEL+NIVO+IPI: 7.2 months, SEL+NIVO: 17.5 months). Among the patients with clear cell RCC who received SEL+NIVO+IPI as first line (1L) therapy (N = 4), all (100%) achieved SD as best overall response. Among the patients with ccRCC who received SEL+NIVO as 1L (N = 2), one patient achieved confirmed PR and the other achieved SD. The median overall survival (OS) was 27.8 months (SEL+NIVO+IPI: unreached, SEL+NIVO: 21.3 months). Conclusions: Treatment with SEL in combination with NIVO or NIVO+IPI is well-tolerated and shows modest clinical activity as compared to historic NIVO or NIVO+IPI activity. Clinical trial information: NCT02419495.

Phase Ib study of selinexor and eribulin combination in advanced solid tumors and triple-negative breast cancer.

3108 Background: Selinexor (KPT-330) is potent inhibitor of Exportin-1. In vitro, Selinexor was found to be synergistic with eribulin in triple negative breast cancer (TNBC) cell lines and enhanced antitumor activity of eribulin in TNBC patient-derived xenografts (PMID 28810913). Methods: We conducted a phase Ib trial in combination of selinexor and eribulin using 3 + 3 design in dose escalation for patients with advanced solid tumors and in TNBC in dose expansion cohort. Eribulin could be discontinued after combination for 6 cycles at physician discretion. Primary objectives: Safety, Recommended Phase 2 Dose (RP2D). Secondary Objectives: Objective Response Rate (ORR), Duration of Response (DOR), Disease Control Rate (DCR), Overall Survival (OS) and Progression Free Survival (PFS). Results: 31 patients, TNBC (n = 19), sarcoma (n = 8), others (n = 4) enrolled in dose escalation (n = 10) and dose expansion phases (n = 21). Median prior therapies:4 (1–6). Study initiated selinexor at 60mg twice weekly and eribulin 1.4mg/m2 on Day1, Day8 every 3 weeks which led to 1 Dose Limiting Toxicity (DLT) and hence, selinexor 80mg once weekly and eribulin 1mg/m2 was elected as RP2D due to efficacy and tolerability. As of 01/15/2022, of 29 patients (94%) who have discontinued treatment, 24 (77%) were due to progressive disease, 3 (10%) withdrew consent and 2 (6%) due to toxicities (G1 pneumonitis; G3 neutropenia) while 2 (6%) remain on trial. All 31 patients had at least one treatment emergent adverse event (TEAE) while most prevalent TEAEs (all grades) were leukopenia (77%), nausea (71%), anemia and neutropenia (68%) and fatigue (48%). The most common G3/4 TEAE were leukopenia (26%) and neutropenia (29%). 2 DLTs occurred; 1 in first dose level (DL); 1 in second DL dosed at selinexor 80 mg once weekly due to G3 neutropenia. ORR for all was 10% while DCR (SD+PR+CR) > 6 months seen in 3 (15%) TNBC and 2 (20%) sarcoma patients. The median OS and PFS for all were 12.3 (7.3, 27.3) months and 2.3 (1.6, 4.1) months. In dose escalation cohort, ORR was 10% where one patient (3%) with vaginal SCC had confirmed PR (-44%) for 2.1 months. Five patients (62.5%) with sarcoma had stable disease (SD). One patient with high grade sarcoma has SD for 68 months and remains on selinexor after 4 months of eribulin and selinexor. In TNBC dose expansion (n = 19), ORR was 10.5% with 2 confirmed PRs and median duration of response (DOR) of 10.8 months. One patient who has remained on treatment for 18 months, and after receiving 8 months of eribulin and selinexor, remains on selinexor with 100% target regression and an indeterminate brain lesion. Conclusions: Selinexor with eribulin is safe with manageable toxicity profile and modest overall clinical efficacy. Durable responses and disease control were observed with metastatic TNBC. Further study is needed to examine the determinants of response to this combination. Clinical trial information: NCT02419495.

Exportin 1 as a therapeutic target against chemoresistance in small cell lung cancer.

e20613 Background: Small cell lung cancer (SCLC) is an extremely aggressive disease comprising around 13% of lung cancer cases and responsible for approximately 250,000 deaths globally per year. A major cause of SCLC poor prognosis is the sparse treatment options available, typically resulting in only transient responses. The backbone of SCLC treatment over the past several decades has been platinum-based doublet chemotherapy, with the recent addition of immunotherapy to first-line chemotherapy showing only limited benefit in a small subset of patients. Major hurdles to improving SCLC treatment include development of rapid chemoresistance and ineffective second line therapies. The identification of more durably effective therapeutic strategies is a major unmet clinical need. Methods: We performed an in vitro CRISPR screen in SCLC cell lines to identify potential therapeutic targets to sensitize to chemotherapy, including short-term cultured cell lines derived from patient-derived xenografts (PDXs). Candidate hits were validated genetically and pharmacologically with in vitro and in vivo. Signaling pathways involved in phenotypes observed were studied by RNA sequencing and western blot, and toxicity studies were performed in vivo to assess the safety of the agents at pharmacologically effective doses. We performed immunohistochemistry (IHC) to assess expression of candidate targets in tissue microarrays (TMAs). Results: Our CRISPR screen revealed the nuclear exporter XPO1 (Exportin 1) as a promising target sensitizing to chemotherapy, independently of the SCLC subtype. Importantly, exportin 1 is a therapeutic target in hematological malignancies, counting with a potent and selective inhibitor, selinexor, approved for clinical use. Combination of selinexor with cisplatin or irinotecan demonstrated high synergy in vitro and exquisite efficacy i n vivo in an array of chemonäive and chemoresistant SCLC PDXs, respectively, including all major SCLC subtypes. These chemotherapy-sensitizing effects were associated with the ability of Exportin 1 to impair chemotherapy-induced AKT overactivation, potentially occurring as a cytoprotective/anti-apoptotic mechanism in response to chemotherapy. The combinations were well tolerated in mice. We found that XPO1 mRNA expression was higher in SCLC than in any other solid tumor type or hematological malignancies, which we were able to confirm at the protein level in clinical TMAs. Conclusions: Exportin 1 inhibition strongly enhances sensitivity of SCLC tumors to cisplatin and irinotecan, used in first line and second line treatment of SCLC tumors, respectively. These results provide preclinical rationale for the combination of selinexor with first line and second line chemotherapy in SCLC. The clinical availability of selinexor will allow immediate clinical translation of these results in a disease setting with extremely limited therapeutic options.

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 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.

Selinexor synergizes with azacitidine to eliminate myelodysplastic syndrome cells through p53 nuclear accumulation.

Myelodysplastic syndromes (MDS) are clonal malignancies of multipotent hematopoietic stem cells, characterized by ineffective hematopoiesis leading to cytopenia. Hypomethylating agents, including azacitidine, have been used for treating MDS with some success; however, the overall survival rate remains poor and, therefore, finding new therapies is necessary. Selinexor, which exerts anticancer effects against some hematologic tumors, is a nuclear export protein inhibitor that blocks cell proliferation and induces apoptosis in various cancer cell lines. We investigated the effects of combined selinexor and azacitidine administration on two MDS cell lines, namely SKM-1 and MUTZ-1. Cells were subjected to a proliferation assay, and the effects of each drug alone, and in combination, were compared. Changes in apoptosis and the cell cycle between groups were also analyzed. Western blotting was conducted to identify the underlying mechanism of action of combined selinexor and azacitidine therapy. The results revealed that the combination of selinexor and azacitidine synergistically inhibited MDS cell proliferation and arrested the cell cycle at the G2/M phase. This combination also promoted MDS cell apoptosis and enhanced p53 accumulation in the nucleus, thereby allowing p53 to be activated and to function as a tumor suppressor. Overall, our results indicate that the combination of selinexor and azacitidine may be a promising approach for treating MDS.

Ex vivo drug sensitivity screening in multiple myeloma identifies drug combinations that act synergistically.

The management of multiple myeloma (MM) is challenging: An assortment of available drug combinations adds complexity to treatment selection, and treatment resistance frequently develops. Given the heterogeneous nature of MM, personalized testing tools are required to identify drug sensitivities. To identify drug sensitivities in MM cells, we established a drug testing pipeline to examine ex vivo drug responses. MM cells from 44 patients were screened against 30 clinically relevant single agents and 44 double‐ and triple‐drug combinations. We observed variability in responses across samples. The presence of gain(1q21) was associated with low sensitivity to venetoclax, and decreased ex vivo responses to dexamethasone reflected the drug resistance observed in patients. Less heterogeneity and higher efficacy was detected with many combinations compared to the corresponding single agents. We identified new synergistic effects of melflufen plus panobinostat using low concentrations (0.1–10 nm and 8 nm, respectively). In agreement with clinical studies, clinically approved combinations, such as triple combination of selinexor plus bortezomib plus dexamethasone, acted synergistically, and synergies required low drug concentrations (0.1 nm bortezomib, 10 nm selinexor and 4 nm dexamethasone). In summary, our drug screening provided results within a clinically actionable 5‐day time frame and identified synergistic drug efficacies in patient‐derived MM cells that may aid future therapy choices.

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.

Selinexor in Combination with Carboplatin and Pemetrexed in Patients with Advanced or Metastatic Solid Tumors: Results of an Open-Label, Single-Center, Multi-Arm Phase 1b Study.

Selinexor in Combination with Carboplatin and Pemetrexed in Patients with Advanced or Metastatic Solid Tumors: Results of an Open-Label, Single-Center, Multi-Arm Phase 1b Study.