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The key nuclear export protein CRM1 (chromosomal region maintenance 1, Exportin 1, XPO1) may directly contribute to the pathophysiology of human multiple myeloma (MM). Here, we characterized the role of CRM1 in MM biology and defined the efficacy and molecular mechanisms of novel oral, irreversible, selective inhibitors of nuclear export (SINEs) targeting CRM1 against MM. CRM1 is significantly elevated in patient MM vs. normal plasma cells at transcript and protein levels. CRM1 downregulation by shCRM1 lentiviruses inhibited cell growth and survival of MM cells (p< 0.01). Importantly, SINEs (KPT-185, KPT-251, KPT-276, and KPT-330) blocked proliferation and decreased survival of MM cell lines and patient MM cells (LD50 2-log differences). SINEs potently enhanced nuclear accumulation of multiple CRM1 cargo tumor suppressor proteins, including rapid induction of p53 and IκB (as early as 2h after drug treatment) followed by FOXO1A, FOXO3A, p27, and PP2A in MM cells. Transcripts of p53 and its downstream targets (p21, PUMA, BAX) were induced by KPT-185, thereby inducing strong growth arrest and apoptosis. KPT-185 decreased MM oncogenes (c-myc, c-maf), anti-apoptosis molecules Mcl-1 and Bcl-xL; increased pro-apoptotic protein BAX; as well as inhibited pIκBα. Inhibition of pIκBα further correlated with KPT-185-blocked NFκB p65 DNA-binding activity in MM cells with or without A Proliferation-Inducing Ligand (APRIL) stimulation. KPT-185 further downregulated CRM1 protein, which was blocked by bortezomib; concurrently, KPT-185 (or KPT-330) upregulated CRM1 mRNA in MM cells. Cleavage of caspase 3 and PARP was markedly increased in MM1R cells treated with KPT-185 and bortezomib vs. either drug alone, confirming enhanced cytotoxicity by combination of these agents. Combined dex with KPT-185 (or KPT-276) induced synergistic cytotoxicity against MM cells (combination indices < 1). Moreover, KPT-185 and KPT-330 impaired osteoclastogenesis and bone resorption via blockade of RANKL-induced NFκB activation and NFATc1 in OC precursor cells, without impacting osteoblasts and BMSCs. Finally, SINEs (KPT-251 and KPT-276) suppressed MM cell growth (p< 0.01), diminished MM cell-induced osteolysis, and prolonged survival of SCID mice with diffuse human MM bone lesions. Together, these results identify CRM1 as a promising novel target in MM, strongly supporting clinical development of SINE CRM1 inhibitors to inhibit both MM cell growth and related bone disease. The oral SINE KPT-330 is ongoing in MM and other hematological malignancies. Citation Format: Yu-Tzu Tai, Yosef Landesman, Chirag Acharya, Yolanda Calle, Mike Zhong, Michele Cea, Daniel Tannenbaum, Antonia Cagnetta, Michaela Reagan, Aditya Munshi, William Senapedis, Jean-Richard Saint-Martin, Trinayan Kashyap, Sharon Shacham, Michael Kauffman, Yumei Gu, Lizi Wu, Steve Schey, Irene Ghobrial, Andrew Kung, Nikhil Munshi, Paul Richardson, Kenneth Anderson, Haoqiang Ying. The nuclear export protein CRM1 (XPO1) regulates multiple myeloma cell growth, osteoclastogenesis, and myeloma-induced osteolysis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2142. doi:10.1158/1538-7445.AM2013-2142

Radiation therapy is an established therapeutic option for lung cancer, but its use is limited due to side effects. Combining radiosensitizers with RT is a way to augment the efficacy of RT. Chromosome Region Maintenance Protein 1/Exportin 1 (CRM1/XPO1) is a key nuclear export protein, the cargoes of which are Tumor Suppressor Proteins (TSPs) such as p53, FOXO, PTEN, pRB and I-κB. Small molecule SINE block CRM1-dependent nuclear export and force the nuclear retention of TSPs, potentially sensitizing cells to RT. Suggested mechanisms include: 1) Induction of “genome fidelity review” by forced nuclear retention of TSPs; 2) Prevention of single stranded DNA break repair, and thereby reduction of resistance of cancer cells to RT. Methods: IC50 of KPT-SINE e.g. KPT-185 and clinical compound KPT-330, were determined in MTT assays using human NSCLC p53 wild type (wt) cancer cell lines H1299 and A549. Clonogenic assays in the SINE sensitive H1299 (IC50 100nM) and SINE-resistant A549 (IC50 1.7μM) lines were conducted in the presence or absence of escalating doses of radiation. An in vivo tumor xenograft model using the A-549 cell line in SCID mice was also conducted with KPT-330. Results: KPT-185 demonstrated inhibitory effects on the clonogenicity of two NSCLC cell lines in a dose dependent fashion. We showed that, while RT alone treatment caused coloines growing curve reduced to less than 75% tumor volume reduction when compared to vehicle, and a >65% reduction when compared to Cisplatin. In this model, KPT-330 was fairly well-tolerated, with minimal body weight loss by animals over the course of the study. Conclusions: These studies showed that KPT-SINE significantly inhibited the growth of two p53 wt NSCLC lines by MTT assay. Similar inhibition was observed in clonogenic assays with cells (A549) resistant to SINE. We described the additive effects of SINE and RT on NSCLC cell lines, suggesting that SINEs can act as radiosensitizers. We further demonstrated that SINEs are efficacious in vivo in the A549 xenograft model, and display superior efficacy when compared to Cisplatin. SINE compounds represent a promising novel therapy against NSCLC both as stand-alone agents and in combination with RT. These data support further development of SINE-based therapies for NSCLC. Further work on in vivo studies of KPT-SINE in combination with RT will be reported. Citation Format: Tami Rashal, Dilara McCauley, Maya Ilouze, Nir Raphael, Inessa Solomonik, Yaccov Lawrence, Ronen Shavit, Sharon Shacham, Michael Kauffman, Nir Peled. Combination tTerapy KPT-SINE (selective inhibitors of nuclear export) with radiotherapy have additive effects in non-small cell lung cancer (NSCLC) cells in vitro and in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2075. doi:10.1158/1538-7445.AM2013-2075

Purpose. Despite improved treatments using proteosome inhibitor- and immunomodulator-based (thalidomide) therapies human multiple myeloma (MM) still remains an incurable disease. New therapeutic targets or unique drug-combinations are needed to further improve treatment outcomes. Our purpose was to investigate the use of small-molecule inhibitors of the nuclear export (SINE) in combination with proteosome inhibitors (PI), bortezomib (BTZ) and carfilzomib (CFZ) as a potential treatment for MM both in vitro and ex vivo. Methods. Previously, we reported that blocking nuclear export of topo IIα with SINE sensitized MM cells to topo II poisons. In this study, we used SINE inhibitors developed by Karyopharm Therapeutics, KPT-185, -249 and a new clinical compound KPT-330. In addition we investigated the use of KOS-2464 (BMS), an effective and relatively non-toxic analog of the known CRM1 inhibitor LMB. To test the efficacy of these inhibitors, we treated human MM cell lines, RPMI-8226, U266B1 and NCI-H929 with SINE +/- PI. MM cell lines or MM patient bone marrow aspirates were placed at high-density conditions and treated for 20 hours with KPT-drugs (300 nM) or KOS-2464 (10 nM), either concurrently or sequentially with 10-40 nM BTZ or CFZ. Cells were then assayed for cell viability by an automated CellTiter-Blue (Promega) analysis. Additional experiments were performed to investigate time-course of drug action and dose-dependence. In addition, treated cell lines or CD138+/light chain+ patient MM cells were assayed for induction of apoptosis by cleaved caspase 3 staining and flow cytometry. To determine if the SINE blocked CRM1-mediated export, treated cells were separated into nuclear and cytoplasmic fractions and assayed for export of p53 and topo IIα. Immunofluorescent microscopy was used to confirm fractionation results. In addition, CRM1 expression levels were measured in all treated cell lines by both Western blot and quantitative PCR. Results. SINE used in combination with PI were highly effective against both MM cell lines and patient MM cells. We found that SINE blocked nuclear export of both p53 and topo IIα as shown by nuclear/cytoplasmic fractionation and also by immunocytochemical staining. Using the CellTiter-Blue assay, we found that all SINE tested had low IC50 values (nanomolar) as single agents and functioned synergistically with BTZ and CFZ (CI Citation Format: Joel G. Turner, Jana L. Dawson, Christopher L. Cubitt, Michael Kauffman, Sharon Shacham, Daniel M. Sullivan. Combination therapy of human multiple myeloma using proteosome and CRM1 inhibitors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2066. doi:10.1158/1538-7445.AM2013-2066

Background: CRM1 is a nuclear export protein which increases cell viability through nuclear export signal-dependent protein exclusion of tumor suppressor proteins. Selective Inhibitor of Nuclear Exprot (SINE) is a novel class of drugs that selectively inhibit CRM1. Here, we tested the biological effects of targeting CRM1. Methods and results: To explore the efficacy of SINE CRM1 anatgonists in ovarian cancer, we tested the selective small molecule KPT-185(in vitro) against human ovarian cancer cell lines. KPT-185 reduced cell viability in multiple (A2780, A2780CP20, IGROV-1 and SKOV3) human ovarian cancer cell lines with IC50 levels ranging from 0.2 - 0.75μM. Nuclear localization and significantly increased expression of tumor suppressor proteins (e.g., p53, p21 and Fox03a) was noted in response to KPT-185 treatment. Moreover, synergistic reduction in cell viability was noted with topotecan, cisplatin and liposomal doxorubicin (interaction index was 0.45, 0.78 and 0.59, respectively). Using the A2780 in vivo orthotopic ovarian cancer model, oral administration of KPT-330 (in vivo) monotherapy at 20mg/kg twice a week resulted in 90% tumor reduction (p Conclusion: CRM1 inhibitor is a potent inhibitor of ovarian cancer growth and merits additional development. Citation Format: Takahito M. Miyake, Sunila Pradeep, Behrouz Zand, Heather J. Dalton, Yunfei Wen, Guillermo N. Armaitz Pena, Michael Kauffman, Dilara McCauley, Sharon Shacham, John E. Wiktorowicz, Anil K. Sood. Therapeutic targeting of CRM1 in ovarian cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5541. doi:10.1158/1538-7445.AM2013-5541

Introduction: KPT-330 is an oral Selective Inhibitor of Nuclear Export (SINE) that binds covalently to XPO1 at Cys528 resulting in its irreversible inactivation. The nuclear export of over 200 proteins with specific nuclear export sequences (NES) is mediated via XPO1. Amongst the client proteins are many tumor suppressor and growth regulatory proteins (e.g., FOXO, IκB, pRb, p53, p73, p21, and p27). Methods: KPT-330 was tested against the PPTP's in vitro cell line panel at concentrations ranging from 1.0 nM to 10.0 μM using the PPTP's standard 96 hour exposure period. It was tested against the PPTP solid tumor xenografts using a dose of 10 mg/kg administered by the oral route thrice weekly (M-W-F) for 4 weeks with a total treatment/observation period of 6 weeks. Results: The median relative IC50 (rIC50) value for the PPTP cell lines was 125 nM, with a range from 13 nM to greater than 10 μM. There were no significant differences in rIC50 values by histotype, although there was a trend for greater sensitivity for the Ewing sarcoma cell lines (median rIC50 = 57 nM) and lesser sensitvity for the neuroblastoma cell lines (median rIC50 = 235 nM). Most cell lines showed Relative I/O% values between -75% and -100%, consistent with a prominent cytotoxic effect for KPT-330. KPT-330 was well tolerated in vivo. It induced significant differences in EFS distribution compared to control in 29 of 37 (78%) solid tumor xenografts and in 5 of 8 (63%) ALL xenografts. For those xenografts with a significant difference in EFS distribution between treated and control groups, an EFS T/C value of greater than 2.0 indicates a substantial agent effect in slowing tumor growth. KPT-330 induced this level of effect in 11 of 32 (34%) solid tumor xenografts, most frequently for the Wilms tumor (2 of 3) and the Ewing sarcoma (4 of 5) panels. Objective responses were observed in 3 of 38 (4%) solid tumor xenografts, including a maintained complete response (MCR) for a Wilms tumor xenograft, a CR for a medulloblastoma xenograft, and a CR for a slow-growing ependymoma xenograft. For the ALL panel, 2 of 8 (25%) xenografts achieved either CR (ALL-8, T-cell ALL) or MCR (ALL-19, B-precursor ALL). Conclusions: KPT-330 shows potent in vitro activity against many PPTP cell lines, consistent with the activation of multiple tumor suppressor proteins across diverse tumor genotypes. KPT-330 shows tumor regressing activity against selected PPTP solid tumor and ALL xenografts, and shows tumor growth inhibition for a larger number of models. Defining the relationship between KPT-330 systemic exposure in mice and humans will be important in assessing the clinical relevance of the PPTP in vivo results. Planned PD testing may identify biomarkers associated with response of pediatric preclinical models to KPT-330. KPT-330 is in phase 1 clinical trials in adults with advanced solid or hematological malignancies (NCT01607905 and NCT01607892). (Supported by NCI NO1-CM-42216) Citation Format: Peter Houghton, Min Kang, Patrick Reynolds, Richard Gorlick, Anders Kolb, John Maris, Stephen Keir, Hernan Carol, Richard Lock, Catherine Billups, Raushan Kurmasheva, Yosef Landesman, Sharon Shacham, Michael Kauffman, Malcolm A. Smith. Pediatric Preclinical Testing Program (PPTP) stage 1 evaluation of the XPO1/CRM1 inhibitor KPT-330. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-354. doi:10.1158/1538-7445.AM2013-LB-354

Background: CRM1 (XPO1) is the exclusive exportin mediating transport of most tumor suppressor proteins (TSPs) including p53, pRb, FOXO, APC and p21 out of the nucleus, abrogating their function. Methods: We tested the effects of the potent, selective, clinical stage oral SINE compound KPT-330 in prostate cancer (PrCa) models. Male SCID mice orthotopically (intraprostatic) inoculated with the DU145 PrCa, known to produce highly metastatic tumors with visceral metastases. In parallel, male CD1-nu/nu mice were inoculated with intracardiac and intratibial injections of the aggressive/bone-derived PrCa PC3, known to produce prominent osteolytic bone lesions. The effects of SINEs KPT-330 and KPT-251 on metastatic spreading were determined. Results: We previously demonstrated that SINE CRM1 antagonists KPT330 and KPT251 have potent antitumor effects on PrCa both in vitro and in vivo. Here, we demonstrate that KPT-330 reduces intraprostatic DU145 tumor burden as well as the incidence of macroscopic metastases to lymph nodes, liver and lung, in a dose-dependent manner. The DU145 tumor burden was reduced by 41% with KPT-330 (4 mg/kg qd/5 days) and 61% (10 mg/kg q 3-4 d x 7) when compared to controls. The incidence of PC3-derived bone metastases were significantly reduced with KPT-330 at 10 mg/kg (q 2d x 3 weeks). At 50 days after cell injection, 80% (8/10) of controls and 0% (0/10) of the KPT-330-treated animals developed X-Ray evidence of bone lesions (p Conclusions: These data show that selective blockade of CRM1-dependent nuclear export has direct antitumor, anti-metastatic and anti-osteolytic activities in PrCa and thus represents a novel approach for the treatment of advanced/ metastatic PrCa. KPT-330 is now in Phase 1 clinical trials in patients with advanced solid tumors (clinicaltrailas.gov: NCT01607905). Citation Format: Giovanni Luca Gravina, Monica Tortoreto, Andrea Mancini, Paola Muzi, Luca Ventura, Sandra D'ascenzo, Alessandro Addis, Yosef Landesman, Dilara McCauley, Vincenza Dolo, Michael Kauffman, Sharon Shacham, Nadia Zaffaroni, Claudio Festuccia. CRM1-Selective Inhibitors of Nuclear Export (SINE) reduce the incidence of tumor spreading and improve overall survival in preclinical models of prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3440. doi:10.1158/1538-7445.AM2013-3440

Background: Neuroblastoma is a childhood malignancy of the peripheral nervous system, and most patients with high-risk disease are not cured. New therapies are needed, but recurrent somatic mutations indicative of a tractable therapeutic target are rare. Translocation of p53, FOXO, IκB and other critical tumor suppressor proteins (TSPs) from the nucleus to the cytosol is mediated by exportin 1 (CRM1, XPO1), suggesting that inhibition of CRM1 is a rational anti-cancer strategy. KPT-330 is a Selective Inhibitor of Nuclear Export (SINE) that irreversibly binds CRM1 and is currently in Phase 1 clinical trials. SINE inhibits CRM1-mediated nuclear export across multiple tumor types leading to activation of TSPs and cancer cell death. Methods: A panel of 14 well-characterized neuroblastoma cell lines was treated with KPT-330 across a 5-log range. Growth inhibition was measured using CellTiter-Glo (Promega) viability assays and a real time growth monitoring system (xCELLigence, Roche). NOD/SCID mice with neuroblastoma xenografts were treated orally with KPT-330 and tumor size was monitored. Results: KPT-330 showed cytotoxicity against 14 neuroblastoma cell lines with a median IC50 of 289±47.5 nM. Sensitivity to KPT-330 was independent of MYCN amplification status. Combination of KPT-330 with commonly used cytotoxic agents (irinotecan, topotecan, cisplatin, doxorubicin) showed additive effects. In xenograft models using the neuroblastoma cell lines IMR-32 and SH-SY5Y, oral administration of KPT-330 (10 or 20 mg/kg, twice or thrice weekly) was well tolerated and showed significant tumor growth inhibition (p Conclusions: Neuroblastomas show sensitivity to CRM1 inhibition both in vitro and in vivo. Ongoing work is focused on discovering the cellular and genomic factors responsible for increased sensitivity to nuclear export inhibition. With the expected completion of the first in human phase I trials by mid 2013, treatment with KPT-330 has the potential to be rapidly translated into a clinical trial for children with neuroblastoma. Citation Format: Edward F. Attiyeh, Aaron McKeon-Fish, Yosef Landesman, William Senapedis, Dilara McCauley, Trinayan Kashyap, Sharon Shacham, Michael Kauffman, John M. Maris. Targeted inhibition of Chromosomal Maintenance Region Protein (CRM1) potently suppresses growth of human neuroblastoma cell line models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2756. doi:10.1158/1538-7445.AM2013-2756

Ovarian cancer (OvCa) is the most lethal female reproductive tract malignancy worldwide with >190,000 new cases diagnosed yearly. Overall, ∼60% of patients will relapse after primary therapy and for the majority of women with advanced disease, their platinum-resistant cancers are currently incurable. During OvCa progression, multiple tumor suppressor proteins (TSPs), most notably p53 (>95% of late-stage cases), are inactivated. Chromosomal region maintenance 1 (CRM1) is solely responsible for the nuclear export of the major TSPs, and increased CRM1 expression has been linked to advanced OvCa stage and poor overall survival. To address the therapeutic role of CRM1 inhibition in OvCa, we tested two novel SINEs in vitro and in vivo. For in vitro studies, we used KPT-185 as a single agent and in combination with cisplatinum in the isogenic cell lines A2780 and CP70. KPT-185 cytotoxicity was highly specific for tumor cell lines. The IC50 for the normal ovarian surface epithelial cell line IOSE527 (4000nM) was 40-90 times higher than A2780 (46.5nM) and CP70 (111.7nM) lines. Combination treatment demonstrated an additive effect on cell death, overcoming cisplatinum resistance. A2780 displayed G1/G2 arrest whereas CP70, only G2 arrest. p53 nuclear accumulation, and downstream activation of targets, was demonstrated following SINEs treatment. Two complementary in vivo models were used. First, the orally bioavailable SINE KPT-330, currently in Phase 1 clinical studies, was given as a single agent in a Rag1 KO mouse model with 4 unrelated patient-derived chemonaive cell lines. Oral KPT-330 inhibited subcutaneous tumor growth and markedly increased survival: all chronically treated mice continued to survive longer (>78d) than controls (all died at 23d). Cross-over of control mice to KPT-330 resulted in tumor growth arrest. In the second model, highly aggressive, luciferase positive, cisplatin resistant CP70 cells were injected i.p into nu/nu mice (n=34) and tumor growth followed in real-time using WBLI. SINE treatment led to marked reductions in tumor burden as well as survival improvements: control mice were all dead by 25 days whereas cisplatin (2.5mg/kg, 2x wk; 31d), KPT-330 (15mg/kg, twice weekly; 41d) and KPT-330+cisplatin (same as single treatments, respectively; 48d) treated mice have significantly improved survival outcomes (p Together, these studies demonstrate the first successful use of highly selective, potent and irreversible CRM1 inhibitors in overcoming cisplatin resistance and prolonging survival in OvCa models. Restoration of p53 nuclear localization and functional activity and RNASeq identified pathways at serially increasing doses will be discussed. First-in-man trials have begun and trials in ovarian cancer are planned for 2013. Citation Format: Ying Chen, Eva Kalir, Catalina Camacho-Vanegas, Fei Huang, Elena Pereira, Yosef Landesman, Dilara McCauley, Mansoor Raza Mirza, Michael Kauffman, Sharon Shacham, Peter R. Dottino, John A. Martignetti. Increased overall survival in platinum-resistant ovarian cancer: paradigmatic use of novel SINE (selective inhibitor of nuclear export), which restores p53 nuclear localization and activation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2163. doi:10.1158/1538-7445.AM2013-2163

Abstract SINE are novel small molecules in human phase I clinical trials for advanced cancers. SINEs inhibit nuclear export through covalent binding to Exportin 1 (XPO1/CRM1) leading to forced nuclear retention of major tumor suppressor proteins (TSPs) such as p53, FOXO, PTEN, pRB and IKB, leading to selective death of cancer cells. Resistant cells were created by treating the sensitive fibrosarcoma cell line HT1080 with increasing concentrations of SINE over 12 months. Gene chip analysis of parental-sensitive and drug-resistant cells that were treated with SINE resulted in activation of distinct pathways that mediate mechanisms of response and drug resistance. Methods Resistant cells were generated by selection in increasing concentrations of SINE. Cell viability was assayed by MTT. Immunofluorescence was used to compare nuclear export of TSPs. FACS, qPCR and immunoblots were used to measure effects on cell cycle, gene expression and cell death. RNA from naïve and drug treated sensitive/resistant cells was analyzed by Affymetrix microarrays. Results Treatment of SINE-sensitive fibrosarcoma cell line HT1080 (IC50 = 13.6nM) with gradually increasing concentrations of SINE for ∼1 year resulted with > 100 fold decrease in sensitivity to SINE cytotoxicity (IC50 = 1.7μM). Resistant cells displayed prolonged cell cycle (∼72 vs 24hrs) compared to parental cells. Resistant cells did not show increased PgP activity, suggesting that resistance to SINE was not the result of the induction of the multidrug resistance mechanism. Sequencing of CRM1 from the SINE resistant cells revealed no mutations in the SINE / cargo binding pocket including the reactive Cys528. Upon exposure to SINE, resistant cells had reduced nuclear accumulation of p53, p21, FOXO1A, IKB and p27 compared with SINE-sensitive cells. Interestingly, in SINE-sensitive cells, but not in resistant cells, SINE treatment resulted in potent pRB dephosphorylation (growth suppressive form of pRB), nuclear localization and the activation of p53 as measured by the induction of p53-downstream targets p21 and MIC1 (GDF15). In addition, SINE reduced levels of the anti-apoptotic protein Mcl-1, and induced the apoptotic markers Caspase 3 and PARP cleavage in sensitive but not in SINE resistant cells. Genes involved in cell adhesion, cytoskeleton formation, tight junctions, vesicle transport, cell cycle, and apoptosis were identified as key pathways correlating with drug response and resistance. Conclusions This study identified key pathways and genes that are likely mediating response and resistance to SINE antagonists. The extensive selection time (∼1 year) needed to achieve drug resistance suggests that generation of resistance may be difficult and that drug response may be prolonged. Citation Format: Yosef Landesman, Sharon Shechter, Jean-Richard Saint-Martin, Trinayan Kashyap, Marsha Crochiere, William Senapedis, Paul Ippolitti, Boris Klebanov, Sharon Tamir, Diego del Alamo, Mwanasha Hamuza, Gali Golan, Ori Kalid, Erkan Baloglu, Dilara McCauley, Michael Kauffman, Sharon Shacham. Deciphering mechanisms of drug sensitivity and resistance to Selective Inhibitors of Nuclear Export (SINE). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 875. doi:10.1158/1538-7445.AM2013-875

Inhibition of nuclear export can promote re-activation of tumor suppressor proteins (TSPs) by restoring them to the nucleus. CRM1 (chromosome region maintenance 1, XPO1) is the exclusive exporter of many TSPs. We hypothesized that CRM1 inhibition can be used as a therapeutic target in melanoma. The growth inhibitory and pro-apoptotic effects of KPT-185, KPT-276 and KPT-330, potent, small molecule, selective inhibitors of nuclear export (SINEs) were evaluated in a panel of human metastatic melanoma cell lines using an MTS assay and Annexin V/PI staining, respectively. The weak CRM1 inhibitor, KPT-185 trans-isomer, and DMSO vehicle were controls in all assays. CRM1 protein was expressed in melanoma cell lines regardless of molecular profile (BRAF, NRAS, TP53) as determined by immunoblot. SINEs inhibited cell growth in a concentration-dependent manner and induced apoptosis at nanomolar concentrations (range=139.7nM - 2.41μM). Both BRAF wild type (WT) and BRAF V600E mutant lines were sensitive to apoptosis by SINE, but BRAF V600E lines had an 8.8-fold lower IC50s as compared to BRAF (WT) lines (p=0.018). The cytostatic and pro-apoptotic effects of CRM1 inhibition were associated with nuclear accumulation of p53, and p21 induction in A375 and CHL-1 melanoma cell lines with functional p53 at time points prior to apoptosis, while pERK accumulated in melanoma cells regardless of p53 status. In pharmacokinetic studies in mice, KPT-276 and KPT-330 showed >50% oral bioavailability with Cmax >5μM. Mice bearing either A375 (BRAF V600E) or CHL-1 (BRAF WT) melanoma xenografts were given KPT-276 or KPT-330 SINE by oral gavage. A375 xenografts (p Citation Format: Jennifer Yang, Matthew A. Bill, Gregory S. Young, Yosef Landesman, Sharon Shacham, Michael Kauffman, William Senapedis, Trinayan Kashyap, Jean-Richard Saint-Martin, Gregory Lesinski. Novel small molecule CRM1 inhibitors induce nuclear accumulation of p53, phosphorylated ERK and apoptosis in human melanoma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3443. doi:10.1158/1538-7445.AM2013-3443

KPT-330 is a small molecule Selective Inhibitor of Nuclear Export (SINE) that irreversibly block the major nuclear export protein CRM1 (exportin 1, XPO1). The Chromosome Region Maintenance 1 (CRM1) protein is responsible for the nuclear export of snRNAs and of proteins bearing a leucine-rich nuclear export signal (NES). This class of drugs is expected to induce forced nuclear accumulation of tumor suppressor proteins (TSPs) and is believed to initiate a ‘genome survey’ leading to the death of cancer cells with normal cells undergoing transient, reversible cell cycle arrest. Our effort was to investigate the effects of KPT-330 in sarcomas and the mechanism by which it exerts the effect of tumor suppression. Our data clearly shows KPT-330 as active against a broad panel of human bone and soft tissue sarcoma cell lines at low nanomolar concentrations. The effect was mainly due to the induction of apoptosis. Target specificity of the drug was confirmed by the decrease in CRM1 protein level. An induction of p53 and p21 protein levels was observed. However, the effect of apoptosis or inhibition in proliferation seems to be independent of p53 status of the cell line. The effect of KPT-330 was further tested in xenograft models using malignant peripheral nerve sheath (MPNST) and de-differentiated liposarcoma (LS141) cell lines. Tumor suppression was observed in both the sarcoma models and its target specificity was confirmed in the xenografts. KPT-330 may represent a new drug for the treatment of bone and soft tissue sarcoma. Citation Format: Jayasree S. Nair, William Tap, Shyamprasad Deraje Vasudeva, Jason K. Sicklick, Michael Kauffman, Sharon Shacham, Gary K. Schwartz. KPT-330, a selective small molecule inhibitor of nuclear export, is active in bone and soft tissue sarcoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5210. doi:10.1158/1538-7445.AM2013-5210

Survivin is a member of the inhibitor of apoptosis protein (IAP) family based on its N-terminal baculovirus IAP repeat (BIR) domain. The protein is largely undetectable in differentiated tissues, but is highly expressed in most human tumors. Its cytoplasmic expression in these tumors correlates with reduced tumor cell death, increased resistance to cancer therapy, and decreased patient survival. Survivin is actively exported into the cytoplasm exclusively by the chromosomal region maintenance 1 (CRM1/Exportin1) protein, one of seven known nuclear export proteins. CRM1 binds to the canonical nuclear export signal (NES) domain within the survivin protein. Inhibition of CRM1-mediated nuclear export has been suggested as a novel cancer therapeutic strategy that restores the tumor suppressor function of multiple nuclear proteins. Here, we investigated the anti-tumor mechanisms of two novel, drug-like CRM1 inhibitors, KPT-185 and KPT-276, in estrogen-receptor positive and triple negative breast cancer cell lines. Tumor and control cells were treated with varying doses of the KPT compounds over time. Cell proliferation and apoptosis were measured using standard assays. Survivin localization and expression in the presence and absence of the KPT drugs was assessed by immunofluorescence microscopy and cell fractionation. Breast cancer cell lines were engineered to express higher or lower levels of Survivin to determine the contribution of Survivin inhibition to the anti-tumor effects of the CRM1 inhibitors. Results showed that the KPT compounds have potent anti-proliferative properties and that they induce time- and dose-dependent apoptosis. KPT-185 and KPT-276 initially enhanced nuclear Survivin expression but produced a decrease in total cellular Survivin levels at later time points. Survivin protein degraded at a faster rate following KPT treatment, which was blocked by treatment with proteasome inhibitors. Knockdown of Survivin increased KPT-mediated cell apoptosis while exogenous expression of Survivin rescued cells from KPT-mediated apoptosis. In summary, our data demonstrate that inhibition of nuclear export by CRM1 inhibition suppresses breast tumor cell growth and enhances tumor cell death, in part through specific targeting of the Survivin-CRM1 complex. Citation Format: Yan Cheng, Michael Holloway, Kevin Nguyen, Michael Kauffman, Sharon Shacham, Rachel A. Altura. Inhibition of the nuclear transport protein CRM1 induces human breast cancer cell death by regulating survivin degradation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 853. doi:10.1158/1538-7445.AM2013-853

Background: Chromosome Region Maintenance 1 (CRM1, XPO1) is a nuclear export receptor which transports certain proteins from the nucleus to the cytoplasm, including tumor suppressor proteins (TSPs) and other modulators of proliferative responses.Overexpression of CRM1 correlates with cancer progression in several human cancers, suggesting that CRM1 could serve as a novel target for the treatment of cancers. NSCLC is an aggressive carcinoma which is not yet curable. The aim of our study was to explore the therapeutic efficiency of novel drug-like CRM1 inhibitors in NSCLC in vitro and in vivo, and to investigate the cytotoxic mechanisms of CRM1 inhibitors in NSCLC cell lines. Methods: KPT-185 and KPT-276 are selective inhibitors of nuclear export (SINE) that block CRM1. Cell viability, apoptosis and cell cycle were evaluated in 6 NSCLC cell lines (1975,H1650,A431,A549,H2228,HCC827) which were treated with KPT-185; TSPs were detected by western blot to explore the possible mechanisms of KPT-185 inducing NSCLC cells growth inhibition and apoptosis. BALB/c nude mice bearing H1975 tumors were treated orally with KPT-276 (similar structure to KPT-185, but improved animal pharmacokinetics) to examine the efficacy and side-effects of KPT-276. Results: In 6 NSCLC cell lines, growth inhibition showed in a dose-dependent way when inhibiting CRM1 by KPT185, with IC50 values range between 50nM to 1500nM. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor(TKI) resistant cell line H1975 was significantly more sensitive to KPT-185 than the EGFR-TKI sensitive cell line H1650. Cell apoptosis analysis showed that KPT-185 induced NSCLC cells apoptosis in both time- and dose-dependent manners. KPT-185 induced cell cycle arrest at the G1/S checkpoint in KPT-185 sensitive cell lines by cell cycle analysis. CRM1 protein expression in both the cytoplasm and nuclei of 6 NSCLC cell lines was down regulated when treated with KPT-185 for 48h. CRM1 inhibition by KPT-185 up-regulated the protein expression of p53 in some cell lines, and down-regulated the expression of EGFR and caspase8. In the xenograft H1975 model, tumor growth was significantly inhibited in KPT-276 oral treatment group compared with vehicle control group (P Conclusions: We investigated the anti-NSCLC activity of SINE (KPT-185 and -276) in vitro and in vivo. SINE CRM1 inhibitors inhibited growth of NSCLC both in vitro and in vivo. SINE inhibited and reduced CRM1 protein, retained TSPs and apoptosis-related proteins in the nucleus, inhibited cell growth and induced apoptosis. Novel SINE CRM1 antagonists may be effective oral therapies for NSCLC. Citation Format: Xiaohong Han, Shuai Wang, Yuankai Shi, Michael Wang, Liang Zhang, Bingliang Fang, Dilara McCauley, Michael Kauffman, Sharon Shacham. Novel SINE CRM1 antagonists for non-small cell lung cancer (NSCLC) in vitro and in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3444. doi:10.1158/1538-7445.AM2013-3444 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Nuclear protein transport is an evolutionary conserved mechanism that controls aberrant cell proliferation through balanced nuclear expression of tumor suppressor proteins (TSPs). In cancers, overexpression of exportin protein chromosome region maintenance 1 (CRM-1) disrupts this balance leading to nuclear exclusion of TSPs leading to the low efficacy of traditional anti-cancer drugs. Our recent screening of pancreatic, colon, triple negative breast cancer (TNBC) and non-Hodgkin's lymphoma (NHL) patient samples showed over-expression of CRM-1. These important finding suggests that therapeutic targeting of CRM-1 leading to restoration of TSPs in the nucleus is an attractive strategy against cancer. Earlier attempts to develop CRM-1 inhibitor were not successful as exemplified by the failure of the Leptomycin B in a single clinical trial due to severe off-target toxicity. Since then the field has not witnessed any serious attempts to develop newer classes of CRM-1 inhibitors that could be used clinically. We have developed specific inhibitors of nuclear export (SINE) that are highly specific, orally active drugs with excellent pharmacokinetic parameters. We tested SINEs as targeted inhibitors of CRM-1, in a panel of pancreatic, colon, prostate, breast, NHL cell lines. SINE showed cancer selectivity (IC50s in low nano molar range in cancer cells and >20 micro Molar in normal lymphocytes, fibroblasts and NIH-3T3 cells). SINE induces global re-alignment of important tumor suppressors such as IKB, FOXO, p53, p73 and p27. SINEs were ineffective in killing cancer cells that were transduced with cys528 mut-CRM-1 proteins (a binding site for SINE) confirming the drugs selectivity. In in vivo studies, the clinical grade SINE induced significant tumor growth inhibition in subcutaneous and orthotopic solid and disseminated NHL xenografts. Our new class of SINEs has excellent pharmacokinetic parameters and has passed advanced toxicity profiling. Based on our strong preclinical data, SINE has entered clinical trials for both solid tumors and hematological malignancies. Citation Format: Asfar S. Azmi, Bin Bao, Michael Kauffman, Sharon Shacham, Ramzi M. Mohammad. Specific inhibitors of nuclear export (SINE) for cancer therapy: from bench to bedside. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3445. doi:10.1158/1538-7445.AM2013-3445

Abstract Chromosomal Maintenance Protein 1/Exportin 1 (CRM1/XPO1) is a key nuclear export protein whose inhibition leads to the nuclear accumulation of Tumor Suppressor Proteins (TSPs) such as p53, FOXO, PTEN, pRB and I-κB. SINE are a novel class of compounds currently in clinical development for a variety of cancers. SINE irreversibly block CRM1-dependent nuclear export and force the nuclear retention of TSPs, inducing apoptosis in cancer cells. Here we report in vitro activity of SINE on a broad range of cancer cell lines and in vivo efficacy results in NCI-N87 gastric and HCT-116 colorectal carcinoma murine tumor xenograft models. Methods MTT cytotoxicity assays were used to determine IC50s of KPT-SINE on various cell lines. The effects of SINE on the cell cycle and gene expression were investigated by FACS and quantitative RT/PCR respectively. Inhibition of CRM1 nuclear export was determined by immunofluorescence of CRM1 cargos. The effects of SINE treatment on tumor growth in vivo were assessed by measuring tumor volumes and by imaging with FluoroThymidine Positron Emission Tomography (FLT-PET). In tumors, gene expression was analyzed and immunohistochemistry performed to detect TSP, proliferation and apoptosis markers. Results SINE showed potent cytotoxicity on the majority of the cell lines tested with IC50 values 80%. Treated tumor samples showed very low levels of Ki67 and increased TUNEL staining consistent with induction of cell cycle arrest and apoptosis in SINE-treated groups. Also, marked upregulation of the TSPs p53 and p21 was observed, indicating that SINE induced nuclear localization of these proteins in situ. In the NCI-N87 gastric carcinoma xenograft model, oral SINE treatment inhibited tumor growth >75% compared with vehicle- treated animals. Immunofluorescence analysis with biomarkers of proliferation, along with FLT-PET results, indicated significant inhibition of proliferation in tumors. Histological analysis of the tumors confirmed in vitro observations of cytotoxic effects on tumors, induction of apoptosis and the replacement of cancer cells with fibrotic tissue. Conclusions These studies demonstrate potent in vitro and in vivo efficacy of single agent SINE CRM1 inhibitors against NCI-N87 and HCT-116 xenografts. These data further support the development of SINE-based therapies for gastric and colorectal cancers. Citation Format: Dilara McCauley, Trinayan Kashyap, Mwanasha Hamuza, Yosef Landesman, Paul Ippolitti, Sharon Shechter, Jean Richard Saint-Martin, Marsha Crochiere, William Senapedis, Boris Klebanov, Sharon Tamir, Diego Del Alamo, Erkan Baloglu, Giulio Draetta, Michael Kauffman, Sharon Shacham. Selective inhibitors of nuclear export (SINE) display single agent efficacy against gastric (NCI-N87) and colon (HCT-116) xenografts. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4336. doi:10.1158/1538-7445.AM2013-4336

411 Background: The currently available targeted therapies for RCC have had limited success, so it is imperative to discover new therapeutic approaches for metastatic RCC. In a search for new such targets, we have identified inhibitors of CRM1 (XPO1, exportin1), the major karyopherin that mediates the export of most tumor suppressor proteins from the nucleus. To expand our initial work on the first generation of CRM1 inhibitors, we now evaluate KPT-330, an orally available Selective Inhibitor of Nuclear Export (SINE), the best tolerated among a series of CRM1 inhibitors that is currently in phase I clinical trials. Methods: The RCC cell lines (Caki-1 and 786-O) and a primary normal human kidney (NHK) cell line were treated with KPT-330, and MTT assays were performed. The cells were subjected to immunofluorescence and immunoblotting for appropriate proteins. Caki-1 xenograft mice were treated with KPT-330 for 15 days, and tumor volume was assessed. Results: KPT-330 selectively attenuated CRM1 levels and caused dose-dependent toxicity (EC50 < 1 µM) through apoptosis in all RCC cells. In untreated RCC cells, p21 was localized in the nucleus, where it likely functions as a cell cycle arrest protein, and in the cytosol, where it functions as an anti-apoptotic protein. However, in NHK cells, p21 was confined to the nucleus. KPT-330 increased p53 and p21 and confined them to the nucleus in both NHK and RCC cells. KPT-330 given orally inhibited RCC growth in xenograft mice (85.3 % inhibition, p < 0.001). Moreover, KPT-330 showed synergism with a Bcl-2 inhibitor ABT-737 in vitro, indicating the potential for combination therapy with a CRM1 inhibitor and Bcl-2 inhibitor. In vivo studies to test the combination of KPT-330 with Bcl-2 inhibitors are ongoing. Conclusions: We introduce a new therapeutic approach for RCC treatment based on the inhibition of the nuclear export of key tumor suppressors. Inhibition of CRM1 causes forced nuclear retention, and thereby activation, of several key p53-pathway proteins, leading to apoptosis in RCC cell lines in vitro and tumor growth inhibition in vivo.

Overexpression of the cellular nuclear exportin 1, more commonly called chromosomal region maintenance 1 (CRM1), has been associated with malignant progression and mortality. Therefore, activation of nuclear export can play a significant etiologic role in some forms of human neoplasia and serve as a novel target for the treatment of these cancers. Mantle cell lymphoma (MCL) is an aggressive histotype of B-cell non-Hodgkin lymphoma that remains incurable. The objective of this study was to investigate the functional significance of CRM1 in MCL by evaluating the therapeutic efficacy of CRM1 inhibition in MCL in vitro and in vivo. Our results showed that CRM1 is highly expressed in MCL cells and is involved in regulating growth and survival mechanisms through the critical nuclear factor-κB survival pathway, which is independent of p53 status. Inhibition of CRM1 by two novel selective inhibitors of nuclear export (SINE), KPT-185 and KPT-276, in MCL cells resulted in significant growth inhibition and apoptosis induction. KPT-185 also induced CRM1 accumulation in the nucleus, resulting in CRM1 degradation by the proteasome. Oral administration of KPT-276 significantly suppressed tumor growth in an MCL-bearing severe combined immunodeficient mouse model, without severe toxicity. Our data suggest that SINE CRM1 antagonists are a potential novel therapy for patients with MCL, particular in relapsed/refractory disease.

1. The decapeptide neurohormone gonadotropin releasing hormone (GnRH) is the first key hormone of the reproductive system. Produced in the hypothalamus, GnRH is released in a pulsatile manner into the hypophysial portal system to reach the anterior pituitary and stimulates the release and synthesis of the gonadotropin hormones LH and FSH. GnRH, a Ca2+ mobilizing ligand, binds to its respective binding protein, which is a member of the seven transmembrane domain receptor family and activates a G-protein (Gq). 2. The alpha subunit of Gq triggers enhanced phosphoinositide turnover and the elevation of multiple second messengers required for gonadotropin release and biosynthesis. 3. The messenger molecules IP3, diacylglycerol, Ca2+, protein kinase C, arachidonic acid and leukotriene C4 cross-talk in a complex networks of signaling, culminating in gonadotropin release and gene expression.

Abstract 326 The key nuclear export protein CRM1 (chromosome region maintenance 1, Exportin 1, XPO1) may directly contribute to the pathophysiology of human multiple myeloma (MM). Here, we characterized the role of CRM1 in MM biology and defined molecular mechanisms whereby novel oral, irreversible, selective inhibitors of nuclear export (SINE) targeting CRM1 mediate anti-MM activity. CRM1 gene expression is increased with disease progression, since it is significantly elevated in active MM and plasma cell leukemia (PCL) vs. normal/MGUS/SMM patients (p< 0.02). CRM1 downregulation by shCRM1 lentiviruses significantly decreases MM cell viability regardless of drug sensitivity and p53 status. Importantly, SINE (KPT-185, KPT-251, KPT-276, and KPT-330) specifically blocked proliferation and decreased survival of MM cell lines (n=14) and patient MM cells (n=17) (LD50 < 200 nM), cultured alone and with bone marrow stromal cells (BMSCs) or osteoclasts. Caspases 3, 8, and 9 were not induced by any SINE in BMSCs derived from MM patients, cultured either alone or with MM cells, under conditions inducing marked apoptosis of MM cells (>2-log differences). These agents potently enhanced nuclear accumulation of multiple CRM1 cargo tumor suppressor proteins p53, IκB, FOXO1A, FOXO3A, p27, and PP2A in MM cells. Transcripts of p53 and its downstream targets p21, PUMA, BAX were also induced by KPT-185, thereby inducing strong growth arrest and apoptosis. KPT-185 decreased MM oncogenes (c-myc, c-maf), anti-apoptosis molecules Mcl-1 and BCL-xL; increased pro-apoptotic protein BAX; as well as inhibited HSP70 and pIkBa. KPT-185 further blocked baseline and APRIL-induced NFkB p65 DNA-binding activity in MM cells. It triggered proteasome-dependent reduction of CRM1 protein; concurrently, KPT-185 and KPT-330 upregulated CRM1 mRNA. Furthermore, KPT-185 induced a number of tumor suppressing, regulatory, apoptotic and anti-inflammatory genes, i.e., p53, p21, PUMA, BAX, CHOP, C10orf10, MIC1, IκBα in MM1S cells in a dose-dependent manner, regardless of the presence of BMSCs. Cleavage of caspase 3 and PARP was markedly increased in MM1R cells treated with KPT-185 and bortezomib vs. either drug alone, validating that the combination of these agents triggered stronger cytotoxicity against MM cells. Combined treatment with dex and KPT-185 (or KPT-276) induced synergistic cytotoxicity against MM cells. Moreover, KPT-185 and KPT-330 impaired osteoclastogenesis and bone resorption via blockade of RANKL-induced NFκB activation in osteoclast precursor cells, without impacting osteoblasts and BMSCs (Abstract#48190). Importantly, SINEs (KPT-251 and KPT-276) suppressed MM cell growth (p< 0.01), diminished MM cell-induced osteolysis, and prolonged survival of SCID mice with diffuse human MM bone lesions (p=0.0004). Together, these results identify CRM1 as a promising novel target in MM, strongly supporting clinical development of SINE CRM1 antagonists to inhibit both MM cell growth and related bone disease. Disclosures: Landesman: Karyopharm Therapeutics Inc: Employment. Senapedis:Karyopharm Therapeutics Inc: Employment. Saint-Martin:Karyopharm Therapeutics Inc: Employment. Kashyap:Karyopharm Therapeutics Inc: Employment. Ying:Karyopharm Therapeutics Inc: Employment. McCauley:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. Munshi:Celgene: Consultancy; Millenium: Consultancy; Merck: Consultancy; Onyx: Consultancy. Richardson:Millenium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene, Millennium, BMS, Onyx: Membership on an entity's Board of Directors or advisory committees; Acetylon, Oncopep: Scientific Founder, Scientific Founder Other.

Abstract 2452 CRM1 (chromosomal regional maintenance 1) or XPO1 (exportin 1) is the major protein that mediates nuclear export. XPO1 has been shown to be over-expressed in cancer cells leading to ineffective cytoplasmic localization of multiple tumor suppressor genes such us p53, FOX03a, and Iκ-β. Chronic Lymphocytic Leukemia (CLL) is characterized by disrupted apoptosis caused both by microenviromental stimuli and aberrant activation of survival pathways including PI3K/Akt, NF-kB, and p53. We previously showed that first generations Selective Inhibitor of Nuclear Export (SINE), KPT-185 and KPT-251, specifically bind to and block XPO1 function resulting in re-activation of tumor suppressor pathways and apoptosis in CLL. Furthermore, we showed that KPT-251 at 75mg/Kg, 3 times per week (QODX3) slowed disease progression, and improved overall survival in the Eμ-TCL1-SCID mouse model of CLL (median OS = 130 and 72 days for KPT-330 and vehicle respectively; p=0.01) with minimal weight loss or other toxicities. The goal of this study was to determine the efficacy of KPT-330, a new generation SINE currently in Phase 1 human studies, with improved pharmacokinetic and oral bioavailability, in the Eμ-TCL1-SCID mouse model of CLL. We first compared the in-vitro activity of KPT-330 to KPT-251. KPT-330 induced improved levels of cytotoxicity on CLL cells compared to KPT-251 with retained selective cytotoxicity against tumor cells when compared to peripheral blood mononuclear cells and isolated B, and T cells. Similar to KPT-251, KPT-330 showed enhanced cytotoxic potency on CLL cells under coculture conditions with stromal cells compared to CLL alone (p10 mg/kg QODX3 but was fully reversed by the end of the study and did not appear to adversely affect the animals. Moreover, KPT-330 at doses of >10 mg/kg BIW and QODX3 significantly prevented an increase in circulating CLL cells compared to vehicle. To further validate KPT-330 in mice with leukemic phase (ie, very high tumor burdens), 20 additional mice were engrafted with CD19+ TCL1 leukemia cells and treatment with vehicle or 15 mg/kg KPT-330 (QoDx3/wk) was initiated 70 days post engraftment. Mice treated with KPT-330 had a significant survival advantage (p=0.0008, median OS = undefined; 99 days, for KPT-330 and vehicle respectively). KPT-330 was strikingly active in prolonging survival of TCL1-SCID mice. Using CLL as a disease model we validate the clinical effectiveness of targeting XPO1 with use of SINE, with favorable therapeutic index in-vivo. These data strongly support the ongoing Phase 1 clinical studies of KPT-330 in patients with advanced hematologic malignancies including CLL. Disclosures: Sandanayaka: Karyopharm Therapeutics: Employment. Shechter:Karyopharm Therapeutics: Employment. McCauley:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment.

Abstract 573 Using high throughput RNA interference screening on 6,722 druggable genes we previously identified XPO1/CRM1 as one of the 50 most vulnerable targets in Multiple Myeloma (MM)1. XPO1 knockdown proved lethal in MM cell lines, but had no effect on human embryonic kidney (293) cells or lung cancer (A549) cells, showing that XPO1 is a specific myeloma vulnerability, and that myeloma cell survival is dependent upon XPO1 expression. XPO1 encodes the protein exportin 1, a nuclear transport protein that exports tumor suppressor proteins from the nucleus, where they are active, to the cytoplasm, where they become inactive. We next analyzed XPO1 in MM via gene expression profiling (GEP). XPO1 expression is up-regulated as the disease progresses: patients with active MM have a higher level of XPO1 compared to normal plasma cells (p Selective inhibitors of nuclear export (SINE) compounds have recently been developed that irreversibly inhibit XPO1/CRM1 and its nuclear export function. One such inhibitor, KPT-276, decreased the viability of all 12 MM cell lines tested in vitro, as shown by MTT assay. After 72 hours of drug treatment, a median IC50 value of approximately 175 nM (range 30–1000 nM) was observed. No synergy with other commonly used anti-MM therapeutics was observed in vitro. In contrast, the drug had little effect in 8 solid tumor cell lines with the exception of the B cell lymphoma line Ramos. KPT-276 was also consistently active in inducing apoptosis against MM primary patient samples. Using an IC80 dose of KPT-276, drug-treated samples had a reduced population of cells in S phase (8%) compared to cells treated with DMSO (21%). Using the vkappa*myc transgenic MM model, KPT-276 reduced monoclonal spikes (by a mean of 56%) in all mice treated orally with 150 mg/kg dose three times per week for 4 weeks. Furthermore, KPT-276 significantly reduced tumor growth in a xenograft MM1.S mouse model. GEP was performed in the presence or absence of drug in two different MM cell lines. Two genes of probable relevance, cell division cycle 25 homolog A (CDC25A) and Bromodomain-containing protein 4 (BRD4), were dysregulated by SINE treatment. Both are involved in cell cycle control and have been linked to MYC. RT-PCR and western blotting confirm that MYC, CDC25A and BRD4 are down-regulated, as soon as six hours, after treatment with KPT-276. KPT-276 has shown marked anticancer activities against B cell malignancies in vitro and is active and tolerated in Phase I canine studies. KPT-330, a close analog of KPT-276, is currently in Phase 1 studies in human with advanced hematological and solid tumors. Disclosures: Schmidt: Karyopharm: Research Funding. McCauley:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. Stewart:Millenium: Consultancy, Honoraria, Research Funding; Onyx: Consultancy; Celgene: Consultancy.

Abstract 1835 Blocking CRM1 by novel selective inhibitors of nuclear export (SINE: KPT-185, KPT-251, KPT-276, and KPT-330) induced potent MM cell apoptosis in vitro and in vivo (Abstract #46829). In addition, these compounds inhibited NFkB p65 DNA-binding activity in MM cells. Here, we investigated whether SINEs have effects on bone and whether this is mediated only through anti-MM activity, or additional effects directly on osteoclasts (OC) are in play. We asked whether SINEs could prevent RANKL/M-CSF-induced osteoclastogenesis via blockade of NFkB activation. Mature OC (TRAP+ multinucleated cell) were derived from the CD138-negative cell fraction from MM patient samples (n=4) stimulated with RANKL/M-CSF for 3 weeks, in the presence or absence of KPT-185. KPT-185 significantly blocked formation of TRAP+ multinucleated OC in a dose-dependent manner, further confirmed by reduction of the selective osteoclastic marker TRAP5b in cell culture supernatant. NFkB p65 activity was induced in nuclear extracts of CD14+ OC precursor cells following RANKL stimulation for 30 min. Importantly, KPT-185 and KPT-330 blocked such induction in a dose-dependent manner. When KPT-185 was added 2 weeks following OC differentiation by RANKL/M-CSF, the effects of KPT-185 on osteoclast culture were not as prominent as when drug was added from the onset. Immunofluorescence staining to examine the actin cytoskeleton in OC cultures performed on glass cover slips further confirmed that actin belt formation in mature OCs is required for bone resorption activity. In the presence of KPT-185 or KPT-330, such critical structure was significantly decreased, consistent with diminished mature OC number and reduced TRAP5b. Pit formation assays on dentine slices clearly showed that KPT-185 and KPT-330, as low as 10 nM, inhibited % erosion area when compared with control group (p Disclosures: Ghobrial: Millennium pharmaceuticals Inc.: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Landesman:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. Anderson:Celgene, Millennium, BMS, Onyx: Membership on an entity's Board of Directors or advisory committees; Acetylon, Oncopep: Scientific Founder, Scientific Founder Other.

Abstract 2438 CRM1, a member of the importin b super family of nuclear transport receptors, functions as a major nuclear export factor by shuttling transcription factors including p53, p21, I-kB, and FOXO3a from nucleus to cytoplasm, thereby preventing their activity. CRM1 is also involved in the transport of rRNA and a certain subset of mRNAs including Cyclin D1. Upregulated CRM1 expression has been reported to correlate with poor prognosis in various hematopoietic malignancies. MCL is a subtype of B-cell lymphoma which is frequently resistant to standard chemotherapy. The t(11,14)(q13;32) translocation of MCL juxtaposes the cyclin D1 gene, and constitutively overexpressed cyclin D1 is believed to be associated with oncogenesis. Additional genetic events such as mutation/overexpression of TP53 have been reported as adverse prognostic indicators. TP53 mutations are rare in typical MCL, although about 30% of aggressive blastoid MCL have mt-TP53. Because of the multiple signaling pathways that are dysregulated in MCL, a novel strategy aimed at restoring multiple anti-oncogenetic pathways, especially targeting p53-independent signaling pathways, is of considerable interest. In this study, we investigated the antitumor effects and molecular mechanisms of the SINE CRM1 antagonist KPT-185 (Karyopharm Therapeutics) in 4 MCL cells with known TP53 mutation status (wt-TP53: JVM2, Z138; mt-TP53: MINO, Jeko-1). Treatment with KPT-185 resulted in reduction of cell proliferation in a concentration-dependent manner without significant differences between wt- and mt-TP53 cells (IC50 at 72hrs by trypan blue exclusion method; 35nM for Z138, 92 nM for JVM2, 96 nM for MINO, 103 nM for Jeko-1). KPT-185 exhibited limited pro- apoptotic activity in the tested MCL cells except Z138 (ED50 at 48hrs by Annexin V positivity; 62 nM for Z138, 910 nM for JVM2, 665 nM for MINO, 618 nM for Jeko-1). We then investigated KPT-185-induced TP53 target gene expression changes (24 genes) by TaqMan low density arrays (TLDA) (Applied Biosystems). In wt-TP53 JVM2 and Z138 cells, KPT-185 (100nM for Z138, MINO, and 500nM for JVM2, Jeko-1) upregulated classical p53 targets such as p21 and MDM2 mRNA (>2.0 fold), while there was no increase in mt-TP53 MINO and Jeko-1 cells. Of note, in both wt- and mt-TP53 cells, KPT-185 upregulated gene expression of PUMA which is a target of FOXO3a, p73 and p53 (3.3 fold for JVM2, 2.5 fold for Z138, 3.3 fold for MINO, 4.8 fold for Jeko-1). Recently, CRM1 has been reported to positively modulate the nuclear export of Cyclin D1 mRNA in a eIF4E-dependent manner. We therefore examined Cyclin D1 protein levels by western blot analysis, and observed significantly high baseline expression of Cyclin D1 in Z-138 cells which are highly sensitive to KPT-185, as compared to less sensitive MCL cells. KPT-185 treatment decreased Cyclin D1 expression in a dose-dependent manner (50nM and 100nM) after 12hrs of treatment accompanied by p21 induction and decreased p-Rb. These findings demonstrate that KPT-185 successfully inhibits CRM1 activity in MCL resulting in inhibition of Cyclin D1 and cell proliferation, and in the p-53-independent upregulation of pro-apoptotic PUMA. In conclusion, CRM1 inhibition by KPT-185 results in cell growth inhibition and in moderate cell death in a TP-53 independent manner. Results also suggest that the sensitivity to KPT-185 in MCL may be dependent on Cyclin D1 expression. Therefore, KPT-185may be an effective agent for the treatment of MCL. Disclosures: Shacham: Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment.

Abstract 35 As tyrosine kinase inhibitors (TKIs) do not induce long-term response in blast crisis chronic myeloid leukemia (CML-BC) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL), and are unable to kill quiescent Ph+ hematopoietic stem cells, alternative therapies targeting dysregulated pathways in BCR-ABL1+ acute leukemias are needed. CRM1, a karyopherin aberrantly overexpressed in several cancers, controls the nuclear export of proteins (e.g. ABL1, SET, p53, p21, FOXO and RB) that regulate normal and malignant hematopoietic cell survival, self-renewal and proliferation. Here we show that enhanced CRM1 expression also occurs in Ph+ leukemias and the clinical stage small molecule inhibitor of CRM1, KPT-330, has a detrimental effect on malignant but not normal hematopoietic progenitors. Specifically, a substantial upregulation (≥ 65% increase) in the expression levels of CRM1 was detected by immunoblot in CD34+ progenitors from bone marrow (BM) of leukemic primary samples (n=3), when compared to CD34+ progenitors from healthy (n=3) donors. Interestingly, CRM1 protein levels in CML CD34+ cells were markedly but not totally reduced by treatment with the ABL1 kinase inhibitor Imatinib (1μM, 72h), suggesting that BCR-ABL1-driven pathways are not the only factor contributing to CRM1 upregulation. Additionally, treatment of primary CML cells with KPT-330 (1μM, 72h) resulted in a 75% reduction in BCR-ABL1 kinase activity, consistent with an interrelationship between BCR-ABL1 and CRM1 activities. Finally, the ability of BCR-ABL1 to induce CRM1 expression was demonstrated upon ectopic BCR-ABL1 expression in myeloid 32Dcl3 precursor cells in which CRM1 protein levels became ∼10-fold higher. To determine the therapeutic relevance of CRM1 inhibition, cell survival was assessed in MACS-purified CD34+ progenitors. Treatment with KPT-330 resulted in ≥80% induction of apoptosis in Ph+ (n=5) CML (2μM, 72hr) and B-ALL (500nM, 72h) CD34+ cells. Conversely, KPT-330 exerted only a minimal effect on the survival of CD34+ progenitors from healthy donor BM (15–30% Annexin V positive, KPT-330 0.5–2μM, 72h). Consistent with the existence of BCR-ABL1-independent signaling leading to increased CRM1 expression, marked apoptosis was also observed in KPT-330-treated CD34+ progenitors isolated from a Ph-negative B-ALL patient. Thus, CRM1 inhibitor-based therapies might also benefit BCR-ABL1-negative leukemias. To formally determine the effects of KPT-330 on leukemic cell survival, methylcellulose-based clonogenic assays were performed. KPT-330 treatment (1μM) resulted in almost total suppression (97% reduction) of the clonogenic potential of leukemic but not normal (30% reduction) CD34+ progenitors. Because of evidence that CRM1 directly interacts with the protein phosphatase 2A (PP2A) inhibitor SET, and that CRM1 inhibition alters trafficking of hnRNP A1, a direct regulator of the SET-PP2A interplay in Ph+ leukemias, it is conceivable that the anti-leukemic activity of KPT-330 is, at least in part, mediated by PP2A activation. Indeed, KPT-330 treatment (1μM, 48hr) of BCR-ABL1+ cell lines resulted in full restoration of PP2A activity, comparable to levels observed in BCR-ABL1-negative cells. Accordingly, KPT-330 treatment (1μM, 12h) of 32Dcl3BCR-ABL1 cells caused a nuclear accumulation (4-fold increase) and cytoplasmic decrease (95% lower) of SET protein levels, as indicated by both confocal microscopy and immunoblots of subcellular fractions. Moreover, KPT-330-treated cells showed altered hnRNP A1 cellular distribution and overall downregulation. However, unexpectedly, hnRNP A1 protein levels were proportionally higher in the cytoplasm and lower in the nucleus, suggesting that the deleterious effect of CRM1 inhibition on hnRNP A1 might not depend on direct inhibition of hnRNP-A1 nuclear export. Because KPT-330 displays favorable ADME properties and has been shown to alleviate leukemic burden using in vivo models of different cancers, we are currently testing the anti-leukemic activity of this compound in a mouse model of CML-BC. We do expect a profound inhibition of leukemogenesis, and all treated mice are currently alive with no signs of toxicity. Thus, CRM1 inhibition by KPT-330 represents a potential new therapeutic avenue which could easily be exploited in malignancies like CML-BC and Ph+ ALL that show a dismal outcome to current available therapies. Disclosures: Walker: Karyopharm Therapeutics Inc: Research Funding. Landesman:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. Perrotti:Karyopharm Therapeutics Inc: Research Funding.

Abstract 870 p53 is a transcription factor that prevents abnormal cell growth. Cellular levels of p53 are critically regulated by MDM2, which is frequently over-expressed in AML. Nutlin-3a disrupts MDM2-p53 interaction, increases cellular levels of p53 in both nucleus and cytoplasm, and activates p53 signaling in cells. p53 status is the major determinant of response to MDM2 inhibitors. p53 is shuttled between the nucleus and the cytoplasm, and CRM1 mediates its nuclear export. Karyopharm Therapeutics has developed novel, potent and irreversible small molecule selective inhibitors of CRM1. We hypothesized that CRM1 inhibition would enhance the nuclear activity of p53, thereby enhancing p53-mediated transcription-dependent apoptotic signaling in AML. We measured CRM1 expression in primary AML samples and investigated if blockade of nuclear export of p53 by CRM1 inhibition would enhance MDM2 inhibitor-induced apoptosis in AML. CRM1 expression was investigated in 511 patient AML samples using a validated robust reverse-phase protein array. Higher levels of CRM1 were associated with higher marrow and peripheral blast percentages (P < 0.00001). Expression was lower in those with favorable cytogenetics compared to those with intermediate or unfavorable cytogenetics (P = 0.029). CRM1 levels were higher in patients with FLT3 mutations (P = 0.003). In 3-way correlation (using distance weighted least squares), there was a clear interaction with p53 levels being highest when CRM1 was high and MDM2 levels were low. Overall survival progressively worsened as CRM1 levels increased, with median survival of 66 weeks for those with CRM1 expression in the lowest third, 47 weeks for middle third and 37 weeks in the highest third (P = 0.007). CRM1 levels did not affect remission duration (P = 0.33). The CRM1 inhibitor KPT-185 exhibited dose-dependent anti-proliferative and cytotoxic activity in AML cell lines, as evidenced by low IC50 values and high Annexin V positivity (= low ED50 values). IC50 values for wild-type p53 cells ranged from 27 to 38 nM, and for mutant p53 cells from 48 to 112 nM, suggesting that KPT-185 potently inhibits AML cell growth largely independent of p53. In contrast, apoptosis induction by KPT-185 was much more prominent in p53 wild-type than in p53-defective cells: ED50 values for Annexin V induction were 150, 90 and 85 nM in p53 wild-type and > 1000 nM in 5 of 6 p53 mutant cell lines. Stable p53 knockdown (> 90% efficiency) rendered AML cells resistant to KPT-induced apoptosis. KPT-185 induced p53 target genes TP53I3, GDF15, MDM2 and ZMAT3 partially in a p53-dependent manner. Hence, p53 was identified as major determinant of CRM1 inhibition-induced apoptosis in AML. MDM2-inhibitor Nutlin-3a induced p53 in both nucleus and cytoplasm, while CRM1 inhibition accumulated p53 in the nucleus. Treatment with KPT-185 or Nutlin-3a caused time-dependent increase in cellular p53 levels. The KPT-185/Nutlin-3a combination induced p53 more efficiently than the individual agents by accumulating p53 exclusively in the nucleus, and synergistically induced apoptosis and cell death. p53 knockdown abrogated these synergistic effects. In primary AML cells, both KPT-185 (24.7 – 36.7% Annexin V) and Nutlin-3a (13.6 – 59.8%) induced apoptosis in a dose-dependent manner. Importantly, both KPT-185 and Nutlin-3a induced apoptosis in CD34+CD38- progenitor cell populations as effectively as they did in bulk AML cells, suggesting high sensitivity of CD34+CD38- cells to CRM1 inhibition and MDM2 inhibition. KPT-185 and Nutlin-3a synergized in the induction of apoptosis in both bulk and CD34+CD38- AML progenitor cells: combination index (CI) values were 0.26 (bulk) and 0.30 (CD34+CD38-) for ED50 and 0.93 (bulk) and 0.46 (CD34+CD38-) for ED75, indicating highly synergistic (CI < 1) efficacy in apoptosis induction. The relation between p53 status and sensitivity to Nutlin-induced apoptosis has been well established. Nutlin-resistant samples were much less sensitive to KPT-185 than Nutlin-sensitive cases (12.2 ± 0.06 % versus 30.9 ± 0.04 % Annexin V, P < 0.05). Synergistic induction of apoptosis was not observed in normal cord blood CD34+CD38- cells. Collectively, CRM1 inhibition offers a novel therapeutic strategy for AML that mostly retains wild-type p53. We propose to develop novel combinatorial approaches for the therapy of AML, aimed at maximal activation of p53 and apoptosis signaling by concomitant MDM2 and CRM1 inhibition. Disclosures: Shacham: Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics: Employment. Andreeff:Hoffmann-La Roche: Research Funding; Karyopharm Therapeutics: Unrestricted gift, Unrestricted gift Other.

e13586 Background: CRM1 is the major nuclear exporter that mediates transport of a variety of molecules, including proteins involved in tumor suppressor and cellular proliferation pathways. The crystal structure of CRM1, in complex with its export cargo, Snurportin 1, has been recently resolved. The molecular understanding of the CRM1-cargo binding interface has led to the development of novel small molecule inhibitors of CRM1-cargo interaction, termed KPT-Selective Inhibitors of Nuclear Export (SINE). KPT-SINE are potent, drug-like CRM1 inhibitors that irreversibly inactivate the CRM1-directed protein export by covalent modification of the essential CRM1-cargo binding residue Cys528. The inhibition of the CRM1 nuclear export has been shown to lead to selective apoptosis in cancer cells when compared to normal cells. Here, we assess the efficacy of the KPT-SINE in human AML, T-ALL, and normal hematopoietic cells. Methods: The viability of a panel of human AML and T-ALL cell lines upon treatment by the KPT-SINE was assessed. Dose-response measurements were done using serial dilutions of KPT-SINE from 1 µM to 0.3 nM and luminescent cell viability assay. Apoptosis was measured using Annexin V staining and TUNEL assays. Results: KPT-SINE induces rapid apoptosis in 10 of 14 AML and 12 of 15 T-ALL cell lines with IC50s of 15-100 nM. In the KPT-SINE-sensitive cell lines, BCL2 overexpression suppresses KPT-SINE-induced apoptosis, indicating its intrinsic pathway mediation. Importantly, KPT-SINE compounds, either KPT-251 at 75 mg/kg or KPT-330 at 15 or 25 mg/kg, induced remarkable growth suppression in MV4-11 human AML cells engrafted into immunodeficient NSG mice with minimal toxicity to normal mouse hematopoietic cells after 35 days of treatment. Bone marrow biopsies of KPT-treated mice were remarkable in that they showed normal hematopoietic cell morphology and cellularity after 35 days of treatment. Xenograft studies to address the potency of the KPT-251 and KPT-330 on MOLT-4 human T-ALL cells in vivo are ongoing. Conclusions: These studies emphasize the clinical promise of the KPT-SINE as a novel and selective drug candidate for the treatment of AML and T-ALL.

e15200 Background: CRM1 (XPO1) is the sole exportin mediating transport of multiple tumor suppressor proteins (TSP) including p53, pRB, FOXO, APC and NPM1 out of the nucleus, abrograting their function. Many tumor types show overexpression of CRM1, thus extinguishing TSP function. CRM1 inhibition forces nuclear accumulation of TSPs inducing apoptosis in cancer cells. Methods: MSKCC PrCa gene database was used for mRNA analyses. Inhibition of CRM1 mediated NE was determined by IHC. MTT assays were used to determine cytotoxicity across divergent PrCa lines: LAPC-4 (p53wt, AR+, low Akt/mTOR); LnCaP (p53wt, AR+, high Akt/mTOR); LnCaP-C81 and LnCaP-C4-2B (p53wt, AR+, androgen independent, high Akt/mTOR); 22rv1 (p53wt, AR+, androgen independent, low Akt/mTOR); PC3 (p53-del, AR–, high Akt/mTOR), DU145 (p53mut, AR–, low Akt/mTOR). BPH1 and prostatic epithelial line EPN were used as non-neoplastic controls. 22rv1 xenografts were initiated in the flanks of SCID mice and treatment begun when tumors reached ~150mm3. Results: Analyses of nuclear pore complex (NPC)-related mRNA levels shows coordinate regulation of transcripts and allow PrCa to be segregated into high and low NPC expression. Low NPC expressing tumors tended to have reduced AR expression; APC, NPM1, and RB1 mRNA levels were also low (p5-20µM). SINE cytotoxic effects are independent all tested genetic alterations. In the aggressive, androgen independent 22rv1 xenograft, oral SINE KPT-251 showed dose-dependent inhibition of tumor growth and synergy with cisplatin. Conclusions: These data show that PrCa shows coordinate NPC regulation, and that selective blockade of CRM1 dependent NE represents a completely novel, neoplasia-selective and well-tolerated target for use as single agent or in combination with chemotherapy for PrCa.

e13549 Background: Inhibition of nuclear export can promote re-activation of tumor suppressor pathways. CRM1 (chromosomal regional maintenance 1) or XPO1 (exportin 1) is the major protein that mediates nuclear export. We hypothesized that CRM1 mediated nuclear export represents a novel therapeutic target that can be manipulated to inhibit melanoma cell survival. Methods: The growth inhibitory and pro-apoptotic effects of KPT-185, KPT-276 and KPT-330, small molecules selective inhibitor of nuclear export (SINE) were evaluated in human melanoma cell lines using an MTT assay and Annexin V/PI staining, respectively. Fluorescence microscopy and immunoblots were used to assess nuclear accumulation of tumor suppressor proteins. The trans-isomer of KPT-185 and DMSO (vehicle) were used as a negative controls in all assays. The pharmacokinetic (PK) profile of all compounds was evaluated in mice. Results: CRM1 protein was highly expressed in human melanoma cell lines with diverse molecular profiles (i.e., B-Raf, NRAS, p53). KPT-SINE inhibited melanoma cell growth in a concentration-dependent manner and induced apoptosis at nanomolar concentrations. Importantly, there was no evidence that B-Raf V600 mutational status influenced melanoma cell response to these agents. Nuclear accumulation and/or induction of p53, p21, FOXO3a, STAT1 and BAD, and reduction of MCL-1 occurred in melanoma cells at time points prior to apoptosis as shown by increase in cleaved PARP and caspase 3 levels. PK studies were conducted in mice following oral administration of 10 mg/kg, to guide drug selection for our ongoing efficacy studies in murine melanoma models. KPT-185 showed limited bioavailability and systemic exposure, while KPT-276 and KPT-330 showed >50% bioavailability reaching Cmax >5µM. Conclusions: This study represents the first report of CRM1 inhibition in melanoma. These data indicate that the novel SINE compounds can effectively inhibit CRM1-mediated nuclear export and induce apoptosis in melanoma cells. KPT-330 is currently under development as orally bioavailable, small molecule inhibitors for a human clinical trial.

4634 Background: For the ~30% of patients who present with RCC at the metastatic stage, multi-kinase inhibitors have been used with moderate success: progression-free survival remains at only one to two years, and thus it is imperative to discover novel therapeutic approaches for metastatic disease. We asked whether (1) SINE inhibitors of chromosome region maintenance protein 1 (CRM1) attenuate key cell cycle regulatory and apoptotic molecules and whether these compounds exert salutary effects in a human RCC xenograft mouse model. Methods: Four RCC cell lines (ACHN, Caki-1, 786-O, and A498) with distinct genotypes, and primary normal human kidney (NHK) cell lines, were used in this study. The cells were treated with the chemically related SINE CRM1 inhibitors KPT-185 or 251 and MTT assays were performed. In addition, cell cycle analyses, immunofluorescence for p53 and p21, and immunoblotting for CRM1, p53, p21, p27, and p-MDM2 were performed for all cell lines. RCC mice with Caki-1 xenografts were treated with vehicle, the orally-available CRM1 inhibitor KPT-251, or sorafenib for 26 days. Tumor volume was measured over several days. Results: Both KPT185 and 251 specifically reduced CRM1 protein levels in RCC cells. KPT-185 caused dose-dependent cytotoxicity in RCC cells, which was greater than sorafenib in RCC cell lines but less in NHK cells, suggesting a possible clinical advantage of KPT-185 over sorafenib. By FACS analysis, we showed that KPT-185 arrests the cell cycle in both G2/M and G1, and increased the sub-G0 cell population. KPT-185 and 251 both increased p53 and p21 in RCC cells, and KPT-185 confined these proteins to the nucleus. In vivo, KPT-251 inhibited Caki-1 xenografts in mice compared to both vehicle and sorafenib without obvious systemic adverse effects. Conclusions: We introduce a completely novel therapeutic approach to the treatment of RCC based on inhibition of the nuclear export of key cell cycle regulatory proteins. Inhibition of CRM1 leads to forced nuclear retention, and thereby activation, of several key p53-pathway proteins, leading to cell cycle arrest and apoptosis in RCC cell lines in vitro and tumor growth inhibition in vivo.

Chromosomal Maintenance Protein 1/Exportin 1 (CRM1/XPO1) is a key nuclear export protein whose inhibition leads to the nuclear accumulation of Tumor Suppressor Proteins (TSPs) such as p53, FOXO, PTEN, pRB and I-κB. Small molecule, KPT-SINE that block CRM1-dependent nuclear export can force the nuclear retention of TSPs, thus render cancer cells more susceptible to apoptosis and more responsive to other chemotherapies. KPT-SINE display significant in vitro and in vivo activity over a broad range of tumor cell lines and xenografts. To optimize the design of future clinical trials, we developed a pharmacodynamics assay and tested it in cell lines, leukocytes in vitro and leukocytes from animal models. Methods: We used quantitative PCR and immunoblotting to study patterns of gene expression of CRM1, Macrophage Inhibitory Cytokine 1 (MIC1), p53 and p21 in human, mouse, rat and monkey leukocytes. The selection and the validation of the four PD markers included 1. In vitro studies where expression of PD markers was determined in tumor cell lines. 2. In vitro studies where expression of PD markers was determined in purified leukocytes. 3. In vivo studies where expression of PD markers was determined in leukocytes isolated from mice, rats and monkeys that were treated with KPT-SINE in pharmacokinetic studies. Drug levels were determined in the plasma of all animals. Results: KPT-SINE treatment at 75 mg/kg QDX5 each week for 4 weeks inhibited tumor growth by more than 80% in Molt-4, Z-138, Hep3b and U87 xenograft models. In separate PK and TK studies, expression levels of the four PD markers were investigated and were found to correlate well with KPT-SINE exposure and duration. In addition, we found that the full induction of those markers was p53-dependent. However, we also observed partial p53-independent induction of CRM1 and MIC1. PK analysis in treated rats and monkeys indicated that KPT-SINE plasma concentrations above 250 nM were sufficient to induce significant changes in the mRNA expression levels of the PD markers. Those concentrations were higher than the individual cytotoxicity indexes (EC50), of each of the above cancer cell lines, that we measured in vitro by cell proliferation assay. Conclusions: The results from our studies suggest that KPT-SINE display potent in vivo efficacy in various xenograft models. We were able to identify PD markers that correlated well with in vitro and in vivo levels of KPT-SINE. Further studies investigating CRM1, p53, p21 and MIC1 as biomarkers of target inhibition and response to KPT-SINE treatment are on-going. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3775. doi:1538-7445.AM2012-3775

Recent evidence demonstrates that Non Hodgkin's Lymphoma (NHL) tumors have elevated expression of the XPO1 gene. XPO1 codes for the nuclear exporter protein CRM-1 that controls localization of critical tumor suppressors including p53 family members. For apoptosis and cell cycle regulation, p53/p73 nuclear localization and DNA binding are highly critical making CRM-1 an attractive therapeutic target for NHL; a disease that carries >90% wild type/functional p53 and only rare mutations in p73. Earlier strategies to develop CRM-1 targeted agents such as Leptomycin B failed in the clinic due to off target toxicity. As a significant advancement to the field, we have identified novel small molecule inhibitors of CRM-1 (KPTs) that bind irreversibly and lock tumor suppressors (including p53 and p73) in cancer cell nucleus leading to apoptosis selectively in tumor cells. The KPTs show minimal toxicity to normal tissues, and possess clinically acceptable pharmacokinetic parameters. Here we demonstrate for the first time that KPTs can induce apoptosis in resistant NHL cell lines and corresponding xenograft models. The most potent CRM-1 inhibitor (KPT-185 and not its inactive analog KPT-Tran) induced growth inhibition, cell cycle arrest and apoptosis in a panel of NHL cell lines with a median IC50 ∼25 nM. The drug does not have growth inhibitory or apoptotic effects against normal peripheral lymphocytes (IC50 ∼20 µM). Fluorescent microscopy, western blot ad co-immunoprecipitation analyses demonstrated that KPT-185 treatment resulted in nuclear localization as well as dissociation of CRM-1-p53 in wt-p53 and CRM-1-p73 in mut-p53 cell lines. Additionally, we observed KPT-185 mediated activation of p21 and Bax that are known downstream executioners of p53/p73 mediated cell cycle control and apoptosis, respectively. Most significantly, knockdown of p53 in wt-p53 WSU-FSCCL and p73 in mut-p53 WSU-DLCL2 abrogated the apoptotic potential of KPT-185, confirming that these were indeed p53/p73 dependent apoptotic events. KPT-185 showed a substantial enhancement in apoptosis when combined with genotoxic p53/p73 re-activating regimen CHOP. Using WSU-DLCL2 SCID models, we further show that oral administration of related CRM-1 inhibitor KPT-276 (75 and 150 mg/Kg p.o) resulted in 65 and 70% tumor reduction, respectively and subcutaneous injections of KPT-251 (25 and 75 mg/Kg) resulted in 70 and 74% suppression of tumor growth with no observed toxicity to the host. Remnant tumor tissue analysis (histology and protein markers) fell in line with our in vitro results with clear activation of p73 pathway. Additionally, Co-immunoprecipitation studies showed dissociation of CRM-1-p73 interaction in KPT treated animal tumors. Our study verifies CRM-1 as a potential therapeutic target in NHL irrespective of the functional status of p53. These results build a strong case for the clinical use of our novel CRM-1 inhibitors either as single agent or in combination with CHOP. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1825. doi:1538-7445.AM2012-1825

CRM1 (Xpo1) is a key nuclear export protein which controls the nuclear export of multiple tumor suppressor proteins (TSP) and cell proliferation pathways including p53, p21, FOXO, PI3K/AKT, Wnt/ß-catenin and NF-κB. Mislocalization of TSP can abrogate their functions as well as render chemotherapies ineffective. Induction of nuclear expression of TSP and chemotherapy targets, by CRM1 inhibition can restore their tumor suppressor functions and increase drug sensitivity. We have developed orally active, small molecule SINE that irreversibly and potently inhibit CRM1 mediated nuclear export of multiple TSP and other cargoes (IC50 < 100 nM). Here, we describe in vitro results using SINE compounds, KPT-185 in vitro and KPT-251 in vitro and in vivo on seven prostate cancer (PrCa) cell lines representing distinct differentiation/progression states of disease and genotypes: LAPC-4 (Androgen receptor [AR] positive, androgen dependent with low Akt/mTOR activities, p53 wt); LnCaP (AR positive, androgen dependent with high Akt/mTOR activities, p53 wt); LnCaP-C81 and LnCaP-C4-2B (AR positive, androgen independent with high Akt/mTOR activities, p53 wt); 22rv1 (AR positive, androgen independent with low Akt/mTOR activities, p53 wt); PC3 (AR negative, with high Akt/mTOR activites and no p53 function (p53 del) and DU145 (AR negative, with low Akt/mTOR activites and mutant p53). Benign prostatic hyperplasia line (BPH1) and Prostatic epithelial line (EPN) were used as non-neoplastic controls. We show that SINE block CRM1 mediated nuclear export of FOXO and p53 with a IC50 values 5-20 μM). SINE cytotoxic effects are independent of p53 status, and induce caspase-3 activation. SINE display synergistic effects in combination with cisplatin and docetaxel in vitro with combination indices between 0.3 and 0.8. In vivo results indicate that KPT-251 show a dose-dependent inhibition of tumor growth. KPT251 was also synergistic when administered at 30mg/kg/5 days/week per os with docetaxel and cisplatin by using the aggressive p53 wt 22rv1 xenografts. Taken together, CRM1 inhibition represents a completely novel, neoplasia-selective and well- tolerated target for use as single agent or in combination with chemotherapy for PrCa. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1841. doi:1538-7445.AM2012-1841

INTRODUCTION: BRAF and NRAS oncogenic mutations occur in over half of all human melanomas. BRAF-mutant tumors are highly sensitive to small molecule inhibitors directed against the oncogenic BRAF protein. However, in tumors that lack the specific mutation, patients have few effective therapeutic options. To address the need for new therapies for patients with BRAF-wild-type (wt) melanoma, we hypothesized that the inhibition of the major nuclear export receptor CRM1 would result in nuclear accumulation of nuclear proteins, increase apoptosis and induce cell cycle arrest independent of BRAF mutational status. To test our hypothesis, we examined the effects of a novel CRM1 inhibitor on melanoma cell lines with various BRAF and NRAS mutational backgrounds. METHODS: We used human malignant melanoma cell lines with BRAF mutation (Sk-Mel-28, A375, Mel-624, UACC903, MalMe-3M), BRAF-wt (MeWo) and BRAF-wt and NRAS mutation (Hs940T) to assess the effects of CRM1 inhibition, BRAF inhibition (PLX4032) or MEK inhibition (U0126) using both mono- or combination therapy. MTT assays were used to evaluate the effects of treatment on cell proliferation. FACS analysis with annexin/PI staining was performed to assess effects on cell cycle and cell death. The Chou-Talalay method was used to assess synergistic drug combination effects. Treatment effects on cleaved caspase-3, PARP cleavage, P53, and FOXO3 were analyzed by western blot analysis. RESULTS: As mono therapy, CRM1 inhibition led to a significant decrease in cell proliferation, cell cycle arrest and an increase in apoptosis in both BRAF wt and mutant cell lines. The degree of inhibition and cell death achieved by CRM1 inhibition across all melanoma cell lines is comparable to the results achieved by BRAF inhibitor PLX4032 in BRAF mutant cell lines. Furthermore, the combination of CRM1 inhibition and BRAF inhibition results in a strongly synergistic combination against BRAF mutant cell lines with a statistically significant decrease in cell proliferation and increased apoptotic cell death. CONCLUSION: We found that relative to other cancer cell types, both BRAF-mutant and BRAF-wt melanoma cells are exquisitely sensitive to CRM1 inhibition. In addition, CRM1 inhibition significantly enhanced the effect of PLX4032 in BRAF-mutant cell lines, suggesting that the combination of these two drugs may address the emergence of acquired resistance to BRAF monotherapy. Based on these results, CRM1 inhibition warrants further investigation to determine its potential benefit in treating melanoma patients independent of BRAF mutation status. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1914. doi:1538-7445.AM2012-1914

CRM-1 exportin protein encoded by the XPO-1 gene maintains cancer cells through nuclear export signal (NES)-dependent protein exclusion of tumor suppressor proteins (TSPs). High CRM-1 expression has been correlated with poor prognosis in pancreatic cancer making it an attractive therapeutic target. Numerous attempts have been made in the past to develop specific CRM-1 inhibitors; however, earlier inhibitors such as Leptomycin B failed in the clinic due to acute off target toxicity. Using structure based drug design; we have identified new class of selective inhibitors of nuclear export (SINE) that irreversibly inhibits CRM1 and lock TSPs in cancer cell nucleus leading to cancer cell selective apoptosis. The inhibitors have excellent pharmacokinetic parameters and minimal toxicity to normal tissue. Here, we tested SINEs against pancreatic cancer, a disease that urgently needs novel and effective therapies. CRM-1 inhibitors [(KPT-185 (most potent analog), KPT-127, KPT-205, KPT-227 as well as Leptomycin B (as positive control) and not its inactive analog KPT-Tran (as negative control)] induced growth inhibition (MTT) and apoptosis (Annexin V and Histone DNA ELISA) in five cell lines (IC50 ∼150 nM). KPT-SINEs did not have any effect on normal HPDE cells (IC50>5 µM). Mechanistically, KPT-185 mediated apoptosis was found to be through activation, phosphorylation and nuclear localization of a TSP prostate apoptosis response 4 (PAR-4). PAR-4 has earlier been established by our laboratory as a therapeutic target in pancreatic cancer. Co-immunoprecipitation studies demonstrated that KPT-185 dissociated CRM-1-PAR-4 and CRM-1-p-PAR-4 interaction. Further, PAR-4 siRNA knockdown abrogated KPT-SINEs ability to induce growth inhibition or apoptosis. In normal cells PAR-4 localization or phosphorylation was not observed and this was associated with low basal expression of PAR-4 and its phosphorylation inducer protein kinase A protein. Role of other TSPs such as p53 and p27 was also explored, however, our investigations directly point to a PAR-4 specific mechanism. KPT-251 (structurally very similar to KPT-185 with improved pharmacokinetics properties) was well tolerated in SCID mice upto 150 mg/kg, p.o. Oral administration of analog KPT-251 at 25 and 150 mg/kg daily for two weeks reduced pancreatic tumors significantly (p Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1815. doi:1538-7445.AM2012-1815

Introduction: KPT-276 and KPT-335 are irreversible inhibitors of CRM1/XPO1, the major nuclear export protein in cells, forcing nuclear retention of key tumor suppressor and growth regulatory proteins ultimately resulting in tumor cell death. KPT-276 and KPT-335 demonstrate potent anti-tumor activity against tumor cells in vitro at nanomolar concentrations (IC50 < 500 nM) and in multiple mouse xenograft models at doses 5-25 mg/kg with minimal effects on normal cells in vitro (IC50 > 5 μM). In normal laboratory dogs, both KPT-276 and KPT-335 are well tolerated with mild reversible transaminase and bilirubin elevations and mild to moderate anorexia. The purpose of this Phase I study was to evaluate the clinical toxicities, establish the maximum tolerated dose and dosing regimen, and provide a preliminary assessment of biologic activity in dogs with spontaneous cancers that receive KPT-276 and KPT-335 Methods: Dogs with Non-Hodgkins lymphoma (NHL), metastatic osteosarcoma (OSA), melanoma (MEL) and mast cell tumor (MCT) were eligible for enrollment. Drug was administered at a starting dose of 30 mg/kg orally on a Monday/Wednesday/Thursday schedule for KPT-276 and at 3 mg/kg orally on a Monday/Thursday schedule for KPT-335. Complete blood count, serum chemistries, clotting times, drug peak plasma level and response to therapy were assessed at each visit. Results: The first four of dogs entered (MCT n=3 and NHL n=1) received KPT-276; the 3 dogs with MCT experienced progressive disease (PD, n=2) and stable disease (SD, n=1). The dog with NHL experienced a cytologic complete response (CR) of approximately 3 months duration despite having failed chemotherapy induction and prednisone treatment. Adverse events included vomiting, diarrhea, and anorexia (all grade 1-2) and elevations in liver function tests (LFTs, grade 1-3) and bilirubin (grade 1-2), as well as neutrophilic leukocytosis. Pharmacokinetic (PK) analysis indicated wide variation in oral bioavailability among dogs so the closely related analog, KPT-335, that is more potent and has better canine bioavailability was subsequently used. To date, 7 dogs have received KPT-335 (NHL, n=6, OSA, n=1) with responses consisting of PR (NHL n=2), SD (NHL n=2), and PD (NLH n=2 and OSA n=1). Adverse events included anorexia and weight loss (grade 1-3) and LFT elevations (grade 1-3) necessitating dpse reductions to 1-1.5 mg/kg on the M/Th schedule. PK analysis indicated more consistent drug absorption among dogs receiving KPT-335. Conclusions: The novel oral SINE CRM1 inhibitors KPT-276 and KPT-335 exhibit biologic activity in a relevant spontaneous large animal model of cancer. Adverse events associated with drug administration are tolerable and reversible with drug holiday. Enrollment in this clinical trial is ongoing. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-232. doi:1538-7445.AM2012-LB-232

Tyrosine kinase inhibitor (TKI)-based therapies do not induce long-term response in myeloid or lymphoid blast crisis (BC) chronic myelogenous leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). Increased expression/activity of nucleocytoplasmic-shuttling heterogeneous nuclear ribonucleoproteins (hnRNPs) A1, E2 and K, are critical for the expression of factors (e.g. SET/PP2A, C/EBPβ/miR-328, and c-Myc) regulating proliferation and survival of Ph+ progenitors. Because the karyopherin CRM1 controls nuclear export of hnRNPs, we assessed the therapeutic potential of CRM1 inhibitors in CML-BC and Ph+ ALL models. Thus, myeloid 32D-p210BCR-ABL1 and lymphoid Baf3-p190BCR-ABL1 progenitors were exposed to the CRM1 selective & potent inhibitors of nuclear export (SINE) KPT-185 and KPT-207. MTT viability assays revealed that KPT-185 and KPT-207 decreased cell viability by ∼80% at concentrations ranging from 150-350 nM. The KPT-SINE not only induced killing, but also affected cytokine-independent growth of BCR-ABL1+ cells: proliferation was inhibited 89% and 81% by KPT-185 and KPT-207, respectively. Notably, growth and survival of non-transformed 32Dcl3 and BaF3 cells was not affected (70-100% viable cells) by KPT-SINE. As expected, treatment (1 μM; 48h) with these inhibitors altered the nuclear/cytoplasmic ratio of hnRNPs important for BCR-ABL1 leukemogenesis. As a result, treatment of BCR-ABL1+ cells with KPT-185 and KPT-207 (1 μM; 48h) resulted in 75% and 50% suppression of BCR-ABL1 expression and kinase activity, respectively. Furthermore, KPT-207 also reduced Myc expression in 32D-p210BCR-ABL1 cells; this is consistent with the potential interference of KPT-207 with the proliferation/survival signals triggered by the BCR-ABL1/MAPK/hnRNP K/Myc pathway in CML-BC progenitors. Because both KPT-185 and KPT-207 significantly alter hnRNP A1 localization, which is important for regulation of the PP2A inhibitor SET and, therefore, for BCR-ABL1 leukemogenesis, we assessed whether KPT-207 and KPT-185 negatively regulate PP2A activity. Indeed, treatment with KPT-207 and KPT-185 (250 nM; 48h) restored PP2A activity in 32D-p210BCR-ABL1 cells to levels similar to those detected in non-transformed 32Dcl3 cells. Although further investigation of KPT-207 and KPT-185 mechanism of action and assessment of their biologic/therapeutic effects in CML-BC and Ph+ ALL mouse models and primary leukemic and normal progenitors is currently ongoing, it is safe to conclude that selective nuclear export (SINE CRM1) inhibitors represent potentially powerful therapeutic tools that, if used alone or in combination with TKIs, might lead to sustained complete molecular remission in CML-BC and Ph+ ALL patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3839. doi:1538-7445.AM2012-3839

609 Background: Resistance to conventional chemotherapy remains a major challenge in Stage IV colon cancer. CRM1 inhibition leads to nuclear sequestration of proteins such as tumor suppressor p53, growth regulatory proteins, and chemotherapy targets such as topoisomerase I/II. We examined the effects of combination use of KPT185 (a novel CRM1 inhibitor) with SN38 (active metabolite of irinotecan) and the effect of drug administration sequence in human colon cancer cell lines to determine if CRM1 inhibition enhances the cytotoxic effect of chemotherapy. Methods: We evaluated the combination effect of KPT185 with SN-38 on both Lovo (KPT-sensitive, IC50 = ∼ 500nM) and HT29 cells (KPT-resistant, IC50 = 1000 ∼ 3000nM) by the Chou-Talalay method, an MTT-based assay that interrogates response across a spectrum of drug dosages: KPT185 (0, 1, 10, 100, 1000, 10000 nM) and SN38 (0, 100, 500, 1000 nM). Cell cycle analysis by FACS with propidium iodide (PI) staining was performed. Effects on apoptosis were determined by FACS (Annexin V/PI staining) and Cell Death Detection ELISA assay. Results: The Chou-Talalay method determined that there is a synergistic effect when KPT185 is combined with SN38 in both Lovo and HT29 cells (combination index > 1). FACS analysis demonstrated combination use of KPT185 and SN38 induced an increase in the apoptotic sub-G1 fraction and a shift toward G2/M arrest. Combination treatment also significantly increased the Annexin V/PI-positive fraction compared with SN38 alone case (P < 0.05). Treatment sequence studies demonstrated that pretreatment of SN38 followed by KPT185 (KPT-post) produced the maximum synergistic effect compared with pretreatment of KPT185 followed by SN38 (KPT-pre) or concurrent use (KPT-con); Cell Death Detection ELISA assay showed KPT-post increased apoptosis most (4.3-fold) compared with KPT-pre (4.2-fold), KPT-con (3.8-fold) and SN38 alone (1-fold). Conclusions: Our results show KPT185, a novel CRM1 inhibitor, sensitizes the response to SN38 in KPT-sensitive as well as KPT-resistant colon cancer cells. This method of sensitizing colon cancer cells warrants further evaluation in preclinical models of colon cancer.

245 Background: Pancreatic (PC) and Colon (CC) cancer remain deadly diseases despite the advent of novel targeted and cytotoxic therapies. Therefore, identification of new targets and development of novel agents against these targets are urgently needed. CRM-1 is a nuclear export protein encoded by the XPO1 (exportin 1) gene that mediates leucine-rich nuclear export signal ( NES )-dependent protein export. Elevated CRM-1 expression has been correlated with poor prognosis in PC and CC making it an attractive therapeutic target. Methods: Using structure based drug design, we have identified novel, irreversible small molecule inhibitors of CRM-1 that lock target proteins, including TSP, in the nucleus. Normal cells undergo cell cycle arrest, but most cancer cells initiate apoptosis. Thus, the drugs selectively kill cancer cells with minimal toxicity to normal tissue and possess clinically acceptable pharmacokinetic parameters. In this report, using multiple molecular biological techniques, we have evaluated the role of CRM-1 inhibition on nuclear localization and apoptosis by PAR-4. Results: The most potent small molecule CRM-1 inhibitor (KPT-185) induced growth inhibition and apoptosis in a panel of PC and CC cell lines with IC50’s Conclusions: This is the first report demonstrating CRM-1 as a potential therapeutic target in both PC and CC, perhaps by enhancing PAR-4 function. The drugs KPT-185 and related CRM1-inhibitors warrant further clinical investigations for this deadly malignancy.

Abstract 3758 Despite the remarkable response in chronic phase CML, tyrosine kinase inhibitor (TKI)-based therapies do not induce long-term response in myeloid or lymphoid blast crisis CML (CML-BC) and Ph+ ALL, and are unable to kill quiescent Ph+ hematopoietic stem cells. We reported that CML disease progression is characterized by a BCR-ABL1 dose- and kinase-dependent increase in the expression/activity of nucleocytoplasmic-shuttling of heterogeneous nuclear ribonucleoproteins (hnRNPs) A1, E2 and K, which are essential post-transcriptional and translational modulators of critical regulators of cell proliferation, survival and differentiation of CD34+ CML-BC and/or CD34+/CD19+ Ph+ ALL progenitors including SET/PP2A, E2F3, Bcl-xL, C/EBPa, miR-328, and c-Myc. The karyopherin (a class of proteins involved in regulating nuclear import/export) chromosome region maintenance 1 (CRM1) controls the nuclear export of several hnRNPs, and because growth/survival of CML-BC and Ph+ ALL progenitors requires the aberrant cytoplasmic activity of hnRNPs A1, E2 and/or K, we have explored the therapeutic potential of CRM1 inhibitors in p210 and p190 BCR-ABL1+ cell line models of CML-BC and Ph+ ALL, respectively. Thus, the cytokine-dependent myeloid 32Dcl3 and lymphoid BaF3, and the derived cytokine-independent 32D-p210BCR-ABL1 and Baf3-p190BCR-ABL1 mouse progenitors were exposed for 48 hr to different concentrations (0–10 μM) of the CRM1 selective & potent inhibitors of nuclear export (SINE) KPT-185 and KPT-207. MTT viability assays (n=3) revealed that KPT-185 and KPT-207 decreased viability ∼80% in 32D-p210BCR-ABL1 cells (KPT-185≥207) at concentrations ranging from 150–350 nM. Similar results were obtained in Baf3-p190BCR-ABL1 cells as the EC50 was 300nM for KPT-185 and KPT-207. The KPT-SINE not only induced killing, but also affected cytokine-independent growth of BCR-ABL1+ cells: proliferation was inhibited 89% and 81% by KPT-185 and KPT-207, respectively. Notably, growth and survival of non-transformed 32Dcl3 and BaF3 cells was not affected (70–100% viable cells) at concentrations (150–350 nM) of KPT-185 and KPT-207 that impair survival of BCR-ABL1+ cells. Mechanistically, we found that KPT-SINE CRM1 inhibitors altered the nuclear/cytoplasmic ratio of hnRNPs important for BCR-ABL1 leukemogenesis. Indeed, in KPT-207-treated (1 μM; 48h) BCR-ABL1+ cells hnRNP A1, E2 and K accumulated in the cytoplasm. Likewise, KPT-185 treatment (1 μM; 48h) resulted in hnRNP A1 being sequestered in the nucleus whereas hnRNP E2 distribution was not altered and, unexpectedly, levels of hnRNP K expression were markedly decreased in both subcellular compartments. Interestingly, treatment of BCR-ABL1+ cells with KPT-185 and KPT-207 (1 μM; 48h) resulted in 75% and 50% suppression of BCR-ABL1 expression and kinase activity, respectively. Furthermore, KPT-207 also reduced Myc expression in 32D-p210BCR-ABL1 cells; this is consistent with the potential interference of KPT-207 with the proliferation/survival signals triggered by the BCR-ABL1/MAPK/hnRNP K/Myc pathway in CML-BC progenitors. Because both KPT-185 and KPT-207 significantly alter hnRNP A1 localization in addition to impairing BCR-ABL1 expression/activity, and suppression of PP2A tumor suppressor activity is essential for both p210 and p190 BCR-ABL1-driven leukemogenesis, it is highly plausible that KPT-207 and KPT-185 negatively regulate the BCR-ABL1-dependent and hnRNP A1-mediated induction of the PP2A inhibitor SET thereby rescuing PP2A phosphatase activity, which in turn decreases BCR-ABL1 expression and kinase activity, and triggers in vitro and in vivo apoptosis of primary CML-BC and Ph+ ALL progenitors. Indeed, treatment with KPT-207 and KPT-185 (250 nM; 48h) restored PP2A activity in 32D-p210BCR-ABL1 cells to levels similar to those detected in non-transformed 32Dcl3 cells. Although further investigation of KPT-207 and KPT-185 mechanism of action and assessment of their biologic/therapeutic effects in CML-BC and Ph+ ALL mouse models and primary leukemic and normal progenitors is currently ongoing, it is safe to conclude that selective nuclear export (SINE CRM1) inhibitors represent potentially powerful therapeutic tools that, if used alone or in combination with TKIs, might lead to sustained complete molecular remission in CML-BC and Ph+ ALL patients. Disclosures: Shacham: Karyopharm: Equity Ownership. Kauffman:Karyopharm: Equity Ownership.

Abstract 2913 CRM1 (chromosomal region maintenance 1, XPO1) is the major export protein regulating degradation of key tumor suppressors by transporting them from nucleus to cytoplasm, thus abrogating their function. Highly expressed CRM1 is associated with poor prognosis in several solid tumors, and inhibition of CRM1 restores function of tumor suppressors such as p53, p21 and FOXO and IκB (cellular antagonist of NF-κB). Furthermore, CRM1 knockdown enhances sensitivity of human multiple myeloma (MM) cell lines to topoisomerase II inhibitor (Cancer Res 2009 :69, 17). In this study, we investigated a novel selective CRM1 inhibitor, KPT-185, in human MM cells. Gene expression profiling analysis using GEO database showed that CRM1 expression is significantly increased in CD138+ cells from MM patients versus monoclonal gammopathy of undetermined significance (MGUS) patients or normal donors (p Disclosures: Landesman: Karyopharm Therapeutics: Employment. Senapedis:Karyopharm Therapeutics: Employment. Shacham:Karyopharm Therapeutics Inc.: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. McCauley:Karyopharm Therapeutic Inc.: Employment. Saint-Martin:Karyopharm Therapeutics Inc: Employment. Munshi:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees. Richardson:Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Acetylon: Membership on an entity's Board of Directors or advisory committees.

Abstract 1852 Background: CRM1 (XPO1, exportin) is a nuclear export protein which controls the nuclear-cytoplasmic localization of multiple tumor suppressor proteins and cell proliferation pathways including p53, p21, PI3K/AKT/FOXO, Wnt/ß-catenin/APC, topoisomerase II, and NF-κB/I-κB. Transport of nuclear proteins to the cytoplasm can render them ineffective as tumor suppressors or as targets for chemotherapy. Small molecule, selective inhibitors of nuclear export (SINE) that block CRM1-dependent nuclear export can force the nuclear retention of tumor suppressor proteins, thus rendering cancer cells more susceptible to apoptosis and responsive to other chemotherapy. In this study we evaluated CRM1 as a potential target in MM and the effect of SINE on the activity of established anti-myeloma agents currently in use in treatment of MM. KPT-276 is the lead CRM1 inhibitor being investigated which will be submitted for IND in 2012. Methods: To evaluate expression of CRM1, bone marrow aspirates from MM patients and tonsil tissue from normal patients were enriched for plasma cells (PC) and proteins from cell lysates were separated by SDS-PAGE followed by immunoblotting with CRM1 antibodies. In functional experiments, isolated fresh MM PCs from patients, and NCI-H929, MM1.S, MM1.R and RPMI-8226 cell lines were cultured in RPMI-1640 with 10–15% serum. Cells were treated for 24–72 hrs with CRM1 inhibitors KPT-SINE compounds with or without bortezomib and dexamethasone and were analyzed for cytotoxicity by MTT assay. Drug concentrations for combination experiments were chosen to be at or below IC50 for each individual drug. Apoptosis induction in primary MM cells and cell lines was studied by Annexin V labeling and flow cytometry. Cell lysates from primary MM PCs and cell lines were prepared after treatment with KPT-SINE and were used to determine the expression of p53 and CRM1. Results: Primary MM plasma cells derived from naïve, previously untreated patients show 4–20 fold higher CRM1 protein expression, compared to normal peripheral blood mononuclear cells (PBMCs) and normal tonsilar PCs. Dose response analysis of KPT-SINE compounds in myeloma cell lines showed potent activity with IC50s in the range of 10–100nM. The lead compound KPT-276 had an IC50 of Conclusions: MM plasma cells express CRM1 that is functionally active and therefore is a valid target in the treatment of myeloma. Moreover, higher expression of CRM1 in malignant plasma cells compared to normal PBMCs and normal PCs suggests possibility of therapeutic index. Early mechanistic studies indicate that CRM1 inhibition can lead to an increased expression of p53 (and other tumor suppressors) and its nuclear localization in myeloma cells and therefore might serve as a mechanism for the activity of CRM1 inhibitors in MM. Potentiation of cytotoxicity of bortezomib and dexamethasone by KPT-SINE suggests that these drugs might be useful in treating MM refractory to currently used agents and provide rationale for combining inhibitors of nuclear transport with other drugs. Disclosures: Off Label Use: KPT-SINE family of drugs are not approved for the treatment of multiple myeloma. These drugs have a novel mechanism and are in pre-clinical development for the treatment of several malignancies. McCauley:Karyopharm Therapeutic Inc.: Employment. Shacham:Karyopharm Therapeutics Inc.: Employment. Kauffman:Karyopharm Therapeutics Inc.: Employment. Jakubowiak:Exelixis: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium Pharmaceuticals, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Ortho Biotech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Abstract 598 Recent evidence demonstrates that Non Hodgkin's Lymphoma (NHL) tumors have elevated expression of the XPO1 gene that codes for the nuclear exporter protein CRM-1 controlling the localization of critical tumor suppressors including p53 family members. For effective apoptosis and cell cycle regulation, p53/p73 nuclear localization and DNA binding are highly critical making CRM-1 an attractive therapeutic target for NHL that carries >90% wild type/functional p53 and only rare mutations in p73. We have identified novel small molecule inhibitors of CRM-1 (KPTs) that bind irreversibly and lock target proteins (including p53 and p73) in the nucleus leading to apoptosis of tumor cells. We demonstrate for the first time that KPTs can induce apoptosis in resistant NHL cell lines and corresponding xenograft models. The most potent CRM-1 inhibitor (KPT-185) induced growth inhibition and apoptosis in a panel of NHL cell lines with a median IC50 ∼25 nM. Western blot and confocal microscopy analyses demonstrated that KPT-185 treatment resulted in nuclear localization of p53 in wt-p53 and p73 in mut-p53 cell lines. Additionally, we observed KPT-185 mediated activation of p21 and Bax, known downstream executioners of p53/p73 cell cycle control and apoptosis, respectively. Most significantly, siRNA knockdown of p53 in WSU-FSCCL and p73 in WSU-DLCL2 abrogated the apoptotic potential of KPT-185, confirming that these were indeed p53/p73 dependent apoptotic events. KPT-185 showed a substantial enhancement in apoptosis when combined with genotoxic p53/p73 re-activating regimen CHOP. The KPTs selectively kill cancer cells with minimal toxicity to normal tissues, and possess clinically acceptable pharmacokinetic parameters. Using WSU-DLCL2 SCID models, we further show that oral administration of related CRM-1 inhibitor KPT-276 (75 and 150 mg/Kg p.o) resulted in 65 and 70% tumor reduction, respectively and subcutaneous injections of KPT-251 (25 and 75 mg/Kg) resulted in 70 and 74% suppression of tumor growth with no observed toxicity to the host. Remnant tumor tissue analysis (histology and protein markers) fell in line with our in vitro results with clear activation of p73 pathway. Our study verifies CRM-1 as a potential therapeutic target in NHL irrespective of the functional status of p53. These results build a strong case for the clinical use of our novel CRM-1 inhibitors either as single agents or in combination with CHOP. Disclosures: Kauffman: Karyopharm: Equity Ownership. McCauley:Karyopharm: Employment. Shacham:Karyopharm: Equity Ownership.

Abstract 2734 Chromosomal Region Maintenance 1 (CRM1) overexpression has been associated with cancer progression and mortality in several human cancers, suggesting that activation of nuclear export may play a role in human neoplasia and may serve as a novel target for the treatment of cancers. This overexpression of CRM1 may be related to the export of most tumor suppressor and growth regulatory proteins out of the nucleus, thereby functionally inactivating them. Mantle cell lymphoma (MCL) is an aggressive histotype of B-cell non-Hodgkin lymphoma that is not yet curable. The objective of our study was to investigate the status of CRM1 in MCL, both in MCL cell lines and primary MCL cells, in comparison to normal B cells, and to evaluate the therapeutic efficiency of CRM1 inhibition in MCL in vitro and in vivo, and to elucidate the mechanism of CRM1 inhibitor-mediated MCL cell apoptosis. We used 8 established MCL cell lines and primary cells from 4 patients with relapsed/refractory MCL. KPT185 and KPT276 are novel, highly selective, drug-like small molecular CRM1 inhibitors. Western Blot analysis showed that CRM1 was expressed in both the cytoplasm and nuclei of 8 MCL cell lines. CRM1 was mainly detected in nuclei of normal resting B cells; In contrast, CRM1 was primarily detected in the cytoplasm of freshly isolated primary MCL cells from patients with relapsed/refractory MCL. In 3H-thymidine incorporation assays, inhibition of CRM1 by KPT185 resulted in a significant dose-dependent growth inhibition of 8 MCL cells, with IC50 values range between 10 nM to 120 nM. The blastoid-variant MCL cell lines (Z-138 and Rec-1) were significantly more sensitive to KPT185 than the non-blastoid variant MCL cell lines. Flow cytometry analysis with fluorescence-labeled Annexin V and propidium iodide showed that KPT185 induced MCL cells apoptosis in both time- and dose-dependent manners, but had no effect on cell cycle arrest. MCL cells treated with KPT185 for 12 hours showed caspase 3 activation and PARP cleavage. As shown in Western blot and confocal microscopy, blocking CRM1 activity by KPT185 in MCL cells up-regulated the protein expression of p53, a known CRM1-mediated export protein, and also induced CRM1 translocation to the nucleus and decreased CRM1 expression. In severe combined immunodeficient (SCID) mice bearing palpable Z-138 tumors, treatment with KPT-276 (similar structure to KPT-185 but improved animal pharmacokinetics), 50mg/kg or 150 mg/kg PO QDx5 each week, or cyclophosphamide 100 mg/kg on days 1–3, was initiated. Tumor growth was significantly inhibited (>75%) in all of treatment groups compared with vehicle control. Neutropenia and other cytotoxic-agent specific effects have not been observed in treated animals. In conclusion, CRM1 inhibitors inhibited growth of MCL cells in vitro and in vivo, and induced apoptosis of MCL cells via inhibition of CRM1 expression and blockage of its translocation with functional nuclear proteins. Our data suggest that novel CRM1 inhibitors provide a potential therapy for patients with relapsed/refractory MCL. Disclosures: No relevant conflicts of interest to declare.

Abstract 2622 Background: CRM1 (XPO1) is the major nuclear exporter that mediates transport of a variety of cargos, including proteins involved in tumor suppressor and cellular proliferation pathways (e.g. p53, PI3K/AKT, and NF-kB). CRM1 is upregulated in a range of solid and hematologic malignancies and its overexpression is correlated with poor prognosis, and with resistance to chemotherapy. Recently, the crystal structure of CRM1, in complex with its export cargo, Snurportin 1, has been resolved. The structure elucidates the key contact residues required for the formation of the CRM1-cargo export complex. The molecular understanding of the CRM1-cargo binding interface has led to the development of novel small molecule inhibitors of CRM1-cargo interaction, termed KPT-Selective Inhibitors of Nuclear Export (SINE). KPT-SINE are potent, drug-like CRM1 inhibitors that irreversibly inactivate the CRM1-directed protein export by covalent modification of the essential CRM1-cargo binding residue Cys528. The inhibition of the CRM1 nuclear export has been shown to lead to selective apoptosis in cancer cells when compared to normal cells. Here, we assess the efficacy of the KPT-SINE in human T-ALL, AML, and normal hematopoietic cells. Methods: The viability of a panel of human T-ALL and AML cell lines and normal CD34+ progenitor cells upon treatment by the KPT-SINE was assessed. Dose-response measurements were done using serial dilutions of KPT-SINE from 1 μM to 0.3 nM and luminescent cell viability assay. Apoptosis was measured using Annexin V staining and TUNEL assays. Results: KPT-SINE induces rapid apoptosis in 12 of 15 T-ALL and 10 of 14 AML cell lines with 50% inhibitory concentrations (IC50s) of 15–100 nM. In the KPT-SINE-sensitive cell lines, BCL2 overexpression suppresses KPT-SINE-induced apoptosis, indicating its intrinsic pathway mediation. Importantly, KPT-SINE exhibits selective cytotoxicity against tumor cells when compared to peripheral blood mononuclear cells (PBMCs) and CD34+ progenitor cells in vitro. KPT-SINE at 57 and 150 mg/kg induced 100% inhibition of tumor growth in vivo in a MOLT-4 T-ALL xenograft study. Other xenograft studies to address the potency of the KPT-SINE on selected AML lines in vivo are ongoing. These studies emphasize the clinical promise of the KPT-SINE as a novel and selective drug candidate for the treatment of T-ALL and AML. Disclosures: McCauley: Karyopharm Therapeutics: Employment. Kauffman:Karyopharm: Equity Ownership. Shacham:Karyopharm: Equity Ownership.

e14091 Background: In order to maintain their malignant phenotype, neoplastic cells must neutralize most of their tumor suppressor (TSP) and growth regulatory (GRP) proteins. CRM1, also called expo...

Transport of macromolecules across nuclear membrane is fundamental to the proper functioning of living cells. Nuclear localization of intact tumor suppressor proteins (TSPs) and other growth regulatory proteins (GRPs) such as p53, FOXO, pRB, p21, p27 and IκB are critical for their “policing” function. Conversely, mislocalization of a nuclear protein to the cytoplasm can render it ineffective as a TSP/GRP. Cancer cells appear to acquire intracellular mechanisms to export tumor-supressing nuclear proteins as they evolve and spread. In many cases, nuclear export is followed by proteasome dependent degradation. Most known TSP/GRP utilize the nuclear export protein CRM1 (chromosomal region maintenance 1; also called exportin 1 [XPO1]), to exit the nucleus, and overexpression of CRM1 has been reported as a poor prognostic factor in a variety of neoplasms. Therefore, inhibition of CRM1 can force the nuclear localization of key TSPs/GRPs, activating their pathways. This leads to cell cycle arrest followed by induction of cell death in cancer cells. Our SINE are novel, potent and selective, drug-like nuclear export inhibitors (IC50 ∼40-100nM) that derive their activity through direct covalent modification and inhibition of CRM1. SINE exert selective and prolonged inhibition of CRM1-mediated forkhead (FOXO), p53, p21 and IκB nuclear export in a variety of normal and transformed cell lines. Cell cycle analysis following incubation with the SINE compound KPT-0127 revealed that it blocks at both the G1/S and G2/M phases, consistent with arrest at multiple cell cycle checkpoints. SINE-induced apoptosis is observed in many cancer cell lines (e.g. A375, Jurkat, BL-40, HCT-116), but not in normal proliferating cells (e.g. 3T3, mouse embryo fibroblasts). In cytotoxicity assays, SINE compounds showed highly potent cytotoxicity in both hematologic and solid tumor cell lines (IC50s 2000nM). SINE show no significant effect on 37 proteins including several cysteine proteases, minimal CYP inhibition (> 10 μM for all major CYPs) and no hERG inhibition. In single dose mouse toxicology studies, KPT-0127 was generally well tolerated (p.o. or s.c.) up to 560 mg/kg, and no deaths were observed. The pharmacokinetics of KPT-0127 is adequate for s.c. and i.v. dosing in vivo. Tumor xenograft studies have been undertaken in colon cancer HCT-116 and myeloma MM.1S tumor bearing mice. SINE induce potent, dose dependent anticancer activity against both small (∼140mm3) and large (∼1400mm3) tumors. Together, these data demonstrate that SINE represent a novel mechanism of action with robust anti-tumor activity both in vitro and in vivo and promising applications as single agent and for combination therapies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2580. doi:10.1158/1538-7445.AM2011-2580

430 Background: CRM1 (XPO1) is a key nuclear export protein which controls the location of multiple tumor suppressor (TSP) and growth regulatory (GRP) proteins including p53, PI3K/AKT, Wnt/ß-catenin and NF-kB. Forced nuclear expression of TSP and GRP by CRM1 inhibition can lead to apoptosis in cancer cells while sparing normal cells. Methods: Novel small-moleculeCRM1 inhibitors were synthesized and nuclear distribution studies were performed in cells transfected with HIV-rev GFP proteins. Cell proliferation studies were performed in 16 CRC cell lines: LS-123, SW-626, Colo-201, Colo-205, Colo-320DM, Colo-320HSR, Lovo, DLD-1, HCT-15, WiDi, LS-174T, LS-180, SW-620, C2BBe1, HCT-8, HCT-116, and in human peripheral leukocytes (PBMC). Cellular distribution and apoptosis assays were performed on HCT-116. Antitumor activity is assessed in human HCT-116 xenografts in scid-mice. Results: The lead CRM1 inhibitor, KPT-0127, blocks CRM1 mediated nuclear export of HIV-Rev-GFP, FOXO, and p53 with an IC50 of ∼300 nM. KPT-0127 is cytotoxic to various CRC cell lines with EC50s of 0.07-1.1 μM; in 9 CRC lines EC50s were < 0.3 mM. In contrast, normal cell lines and PBMCs had EC50 > 5-20 μM. In HCT- 116 cells, KPT-0127 induces cell cycle arrest at both G1/S and G2/M checkpoints and dose dependently increases nuclear p53, followed by an increase in caspase 3. KTP-0127 10μM shows no significant effect on 37 proteins including several cysteine proteases. In mice, KPT-0127 given by SC injection of 30-100 mg/kg leads to serum levels exceeding the effective CRM1 inhibitory concentration for at least 4 hours and is well tolerated. KPT-0127 given SC to mice bearing HCT-116 colon xenografts results in dose-dependent antitumor activity. Conclusions: The novel small- molecule CRM1 inhibitor KTP-0127 kills CRC lines with multiple TSP, GRP, and oncogenic abnormalities, including p53 mutations/deletions and PTEN deficiency/AKT activation, while sparing normal cells. This likely reflects the ability of CRM1 inhibition to affect multiple critical and non-redundant regulatory pathways. These results support the development of CRM1 inhibitors for the treatment of CRC. IND-enabling CMC and toxicology work are in preparation. [Table: see text]

Abstract 3012 Background: CRM1 (XPO1) is a key nuclear export protein which controls multiple tumor suppressor proteins (TSP) and cell proliferation pathways including p53, PI3K/AKT, Wnt/ß-catenin and NF-kB. Further, mislocalization of proteins can abrogate TSP functions and render chemotherapies ineffective. For example, multiple myeloma (MM) cells that are grown at high densities (to mimic the in vivo situation) become resistant to topoisomerase 2 (topo2) inhibitors (e.g., doxorubicin) simply because topo2α is exported from the nucleus. Forcing the nuclear expression of chemotherapy targets, TSP and growth regulatory proteins by CRM1 inhibition can restore drug sensitivity and restore checkpoint control/genome surveying functions. These events lead to apoptosis or autophagy in cancer cells while sparing normal cells. Methods: CRM1 inhibitors were synthesized and nuclear distribution studies were performed in U2OS cells transfected with HIV-rev GFP proteins. Cell proliferation studies were performed in multiple myeloma (MM), leukemia and lymphoma cell lines and in human peripheral blood mononuclear cells (PBMCs). Toxicology studies were performed in several mouse strains. Antitumor activity is assessed in a xenograft model of human MM.1 cells growing in scid-mice. Results: The lead CRM1 inhibitor, KPT-0127, blocks CRM1 mediated nuclear export of HIV-Rev-GFP, FOXO, and p53 with an IC50 of ~300 nM. KPT-0127 is selectively cytotoxic to various hematological cell lines with EC50s in the 0.02–1.0 μM range, and shows limited cytotoxicity in similar studies in normal cell lines (NIH-3T3, MRC5, HUVECs) and PBMCs (EC50 >5-20 μM). KPT-0127 increases the nuclear localization of IkB in HUT-78 leukemia cells and human PBMCs, and inhibits TNF-α secretion in LPS stimulated U937 macrophage derived cells, likely through inhibition of NF-kB signaling. In MM cells grown at high densities which actively export topo2 to the cytoplasm via CRM1, blocking CRM1-dependent transport strongly enhanced topo2 nuclear localization and augmented the apoptotic effects of doxorubicin in Conclusions: The sensitivity of tumors with multiple TSP and oncogenic abnormalities, including p53 mutations/deletions and PTEN deficiency/AKT activation, to killing with KPT-0127 likely reflects the ability to affect multiple critical and non-redundant regulatory pathways. CRM1 inhibition also forces topo 2 to remain in the nucleus, and increases levels of nuclear IkB antagonizing NF-kB function, thereby reducing the likelihood of resistance development. These results support the development of small molecule, drug-like CRM1 inhibitors for the treatment of MM and other hematological cancers. IND-enabling CMC and toxicology work are expected to begin in early 2011. Disclosures: Shacham: Karyopharm: Employment, Equity Ownership, Patents & Royalties. Nir:Karyopharm: Consultancy. Draetta:Karyopharm: Consultancy. Sandanayaka:Karyopharm: Employment. Shechter:Karyopharm: Employment. Kauffman:Karyopharm: Consultancy, Equity Ownership, Patents & Royalties.

CRM1 (Xpo1) is the major export factor for proteins from the nucleus to the cytoplasm, including tumor suppressors (TSPs) and other modulators of proliferative responses such as p53, FOXO, c-Abl, pRB and IκB. Leptomycin B (LMB), a non-drug like natural product is a potent inhibitor of CRM1-mediated nucleocytoplasmic transport. LMB and related analogs trap TSPs and other proteins in the nucleus, forcing neoplastic cells into apoptosis while normal cells undergo reversible cell cycle arrest. However, LMB has limited efficacy in vivo due to its severe gastrointestinal toxicity. Here, we describe our lead compound KPT-0127 a novel small molecule, water soluble, drug-like, selective, irreversible CRM1 antagonist. Like LMB, KPT-0127 forms a covalent bond with Cys528 in the CRM1 cargo-binding pocket, abrogating most, but not all, export functions of CRM1. KPT-0127 exerts a potent (EC50 300-400nM) and prolonged inhibition of CRM1- mediated HIV-1 Rev, forkhead (FOXO), and p53 nuclear export in a variety of normal and transformed cell lines. In cytotoxicity assays, KPT-0127 showed high potency in most hematologic cancer cell lines (EC50 5-10µM). Studies in the HCT-116 colon cancer cell line suggested that KPT-0127 dose dependently increases the nuclear levels of p53 and appears to induce cell cycle arrest at both the G1/S and G2/M checkpoints, prior to inducing apoptosis. In normal peripheral blood mononuclear cells (PBMCs) and in Hut78 leukemia cells, KPT-0127 potently increased the nuclear levels of IκB. However, KPT-0127 induced cell death of Hut78 cells with no effect on normal PBMCs. In drug combination studies, KPT-0127 showed additive or synergistic cytotoxicity activity with either 5-FU, carboplatin, or doxorubicin. Mechanism of action studies demonstrated that the Cys528 residue in the cargo-binding pocket of CRM1 is essential for the inhibitory effect of KPT-0127. Mutagenesis of Cys528 to a Ser completely abrogated KPT-0127 inhibition. KPT-0128, the transisomer of KPT-0127, shows little effect on both HIV-Rev nuclear export and in cytotoxicity assays (EC50s > 10μM), supporting the specificity of KPT-0127 for CRM1. Moreover, the selectivity of KTP-0127 was demonstrated across a panel of 37 proteins including several cysteine proteases. In single dose mouse toxicology studies, KPT-0127 was generally well tolerated (oral or SC) up to 560 mg/kg, and no deaths were observed. SC dosing daily for 5 days up to 100mg/kg (the highest dose tested) showed no behavioral, clinical chemistry, or hematogical effects in mice; Pharmacokinetics of KPT-0127 is adequate and in vivo efficacy studies are currently being performed; results will be presented. All together, these data demonstrate that KPT-0127 represents a novel, tumor selective, and well-tolerated irreversible Crm1 inhibitor which may be suitable for clinical development both as a single agent and in combination with standard therapies. Citation Information: Clin Cancer Res 2010;16(14 Suppl):A19.