Elevated serum levels of hepatocyte growth factor (HGF) and high tumor expression of c-Met are both indicators of poor overall survival from ovarian cancer (OVCA). In the present study, we evaluated the role of the HGF signaling pathway in OVCA cell line chemoresistance and OVCA patient overall survival as well as the influence of HGF/c-Met signaling inhibition on the sensitivity of OVCA cells to combinational carboplatin plus paclitaxel therapy. The prevalence of the HGF receptor, c-Met, was determined by immunohistochemistry in primary OVCA samples (n=79) and OVCA cell lines (n=41). The influence of the c-Met-specific inhibitor MK8033 on OVCA cell sensitivity to combinations of carboplatin plus paclitaxel was examined in a subset of OVCA cells (n=8) by CellTiter-Blue cell viability assays. Correlation tests were used to identify genes associated with response to MK8033 and carboplatin plus paclitaxel. Identified genes were evaluated for influence on overall survival from OVCA using principal component analysis (PCA) modeling in an independent clinical OVCA dataset (n=218). Immunohistochemistry analysis indicated that 83% of OVCA cells and 92% of primary OVCA expressed the HGF receptor, c-Met. MK8033 exhibited significant anti-proliferative effects against a panel of human OVCA cell lines. Combination index values determined by the Chou-Talalay isobologram equation indicated synergistic activity in combinations of MK8033 and carboplatin plus paclitaxel. Pearson's correlation identified a 47-gene signature to be associated with MK8033-carboplatin plus paclitaxel response. PCA modeling indicated an association of this 47-gene response signature with overall survival from OVCA (P=0.013). These data indicate that HGF/c-Met pathway signaling may influence OVCA chemosensitivity and overall patient survival. Furthermore, HGF/c-Met inhibition by MK8033 represents a promising new therapeutic avenue to increase OVCA sensitivity to carboplatin plus paclitaxel.

IMPORTANCEPatients with cancer experience high rates of morbidity and mortality after SARS-CoV-2 infection. Immune response to mRNA-1273 vaccination across multiple cancer types and treatments remains to be established. OBJECTIVE To quantitate antibody responses after mRNA-1273 vaccination among patients with solid tumors and hematologic cancer and to assess clinical and treatment factors associated with vaccine response. DESIGN, SETTING, AND PARTICIPANTSThis cohort study included patients with cancer who were aged 18 years or older, spoke English or Spanish, had received their first mRNA-1273 dose between January 12 and 25, 2021, and agreed to blood tests before and after vaccination.EXPOSURES Receipt of 1 and 2 mRNA-1273 SARS-CoV-2 vaccine doses.MAIN OUTCOMES AND MEASURES Seroconversion after each vaccine dose and IgG levels against SARS-CoV-2 spike protein obtained immediately before the first and second vaccine doses and 57 days (plus or minus 14 days) after the first vaccine dose. Cancer diagnoses and treatments were ascertained by medical record review. Serostatus was assessed via enzyme-linked immunosorbent assay. Paired t tests were applied to examine days 1, 29, and 57 SARS-CoV-2 antibody levels. Binding antibody IgG geometric mean titers were calculated based on log 10 -transformed values. RESULTSThe 515 participants were a mean (SD) age of 64.5 (11.4) years; 262 (50.9%) were women; and 32 (6.2%) were Hispanic individuals and 479 (93.0%) White individuals; race and ethnicity data on 4 (0.7%) participants were missing. Seropositivity after vaccine dose 2 was 90.3% (465; 95% CI, 87.4%-92.7%) among patients with cancer, was significantly lower among patients with hematologic cancer (84.7% [255]; 95% CI, 80.1%-88.6%) vs solid tumors (98.1% [210]; 95% CI, 95.3%-99.5%), and was lowest among patients with lymphoid cancer (70.0% [77]; 95% CI, 60.5%-78.4%). Patients receiving a vaccination within 6 months after anti-CD20 monoclonal antibody treatment had a significantly lower seroconversion (6.3% [1]; 95% CI, 0.2%-30.2%) compared with those treated 6 to 24 months earlier (53.3% [8]; 95% CI, 26.6%-78.7%) or those who never received anti-CD20 treatment (94.2% [456]; 95% CI, 91.7%-96.1%). Low antibody levels after vaccination were observed among patients treated with anti-CD20 within 6 months before vaccination (GM, 15.5 AU/mL; 95% CI, 9.8-24.5 AU/mL), patients treated with small molecules (GM, 646.7 AU/mL; 95% CI, 441.9-946.5 AU/mL), and patients with low lymphocyte (GM, 547.4 AU/mL; 95% CI, 375.5-797.7 AU/mL) and IgG (GM, 494.7 AU/mL; 95% CI, 304.9-802.7 AU/mL) levels.CONCLUSIONS AND RELEVANCE This cohort study found that the mRNA-1273 SARS-CoV-2 vaccine induced variable antibody responses that differed by cancer diagnosis and treatment received. These findings suggest that patients with hematologic cancer and those who are receiving immunosuppressive treatments may need additional vaccination doses.

Introduction - Inhibition of Exportin 1 (XPO1) is a novel treatment approach for multiple myeloma (MM). XPO1 mediates the nuclear export of cell-cycle regulators and tumor suppressor proteins leading to their functional inactivation. In addition, XPO1 promotes the export and translation of the mRNA of key oncoproteins (e.g. c-MYC, BCL-2, Cyclin D). XPO1 overexpression occurs in solid and hematological malignancies, including MM and is essential for MM cell survival. Selinexor, the first oral SINE compound, has shown promising anti-MM activity in phase 1 studies but has been associated with gastrointestinal and constitutional toxicities including nausea, anorexia and fatigue. KPT-8602 is a second generation oral SINE compound with similar in vitro potency to selinexor, however, has substantially reduced brain penetration compared with selinexor, and demonstrated markedly improved tolerability with minimal anorexia and weight loss in preclinical toxicology studies. In murine models of MM, KPT-8602 can be dosed daily (QDx5) with minimal anorexia and weight loss. We have therefore initiated a phase 1/2 first-in-human clinical trial. Methods - This phase 1/2 clinical trial was designed to evaluate KPT-8602 as a single agent and in combination with low dose dexamethasone (dex) in patients (pts) with relapsed / refractory MM (RRMM). KPT-8602 is dosed orally (QDx5) for a 28-day cycle with a starting dose of 5 mg. Low dose dex (20 mg, twice weekly) is allowed after cycle 1 if at least a minimal response (MR) is not observed. The primary objective is to evaluate the safety and tolerability including dose-limiting toxicity (DLT), determine the maximum tolerated dose (MTD), the recommended Phase 2 dose (RP2D), and evidence for anti-MM activity for KPT-8602 single agent and in combination with dex. The pharmacokinetic (PK) and pharmacodynamic (PDn; XPO1 mRNA) profile of KPT-8602 will also be determined. PDn predictive biomarker analysis and ex vivo drug response assays are underway using tumor cells from bone marrow aspirates before treatment, during and at relapse. These analyses include cell death pathway assays by flow and nuclear/cytoplasmic localization of XPO1, NF-ƙB, IƙBα, IKKα, NRIF and p53 by imaging flow and IHC. Results - As of 01-Aug-2016, 6 pts 2 M/4 F, (median of 6 prior treatment regimens, median age of 71) with RRMM have been enrolled. Common related grade 1/2 adverse events (AEs) include thrombocytopenia (3 pts), nausea (2 pts) and diarrhea (2 pts). Grade 3 AEs include neutropenia (1 pt) and dehydration (1 pt). No grade 4 or 5 AEs have been reported. No DLTs have been observed and the MTD has not been reached. 5 pts were evaluable for responses (1 pt pending evaluation): 1 partial response, 1 minimal response, and 3 stable disease; no pts have progressed on therapy with the longest on for >5 months. The PK properties following oral administration showed that 5 mg of KPT-8602 was rapidly absorbed (mean tmax= 1 hr, mean Cmax= 30.6 ng/mL). The mean AUCinf was calculated to be 141 ng•hr/mL. After tmax, KPT-8602 declined at an estimated mean t½ of 4 hr. At the same dose level, XPO1 mRNA expression was the highest (~2.5 fold) at 8 hr post dose. Conclusions - Oral KPT-8602 is well tolerated in heavily pretreated pts with RRMM. Gastrointestinal and constitutional toxicities observed with twice weekly selinexor have not been observed with 5x/week KPT-8602, including in pts on study for >4 months. PK was predictable and in line with selinexor. These early results show encouraging disease control with pts remaining on therapy. Enrollment is on-going. Disclosures Rossi: Takeda: Speakers Bureau; Janssen: Speakers Bureau; Onyx: Research Funding, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. Baz:Takeda/Millennium: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Signal Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Merck: Research Funding; Novartis: Research Funding. Hofmeister:Karyopharm Therapeutics: Research Funding; Arno Therapeutics, Inc.: Research Funding; Signal Genetics, Inc.: Membership on an entity's Board of Directors or advisory committees; Janssen: Pharmaceutical Companies of Johnson & Johnson: Research Funding; Incyte, Corp: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Takeda Pharmaceutical Company: Research Funding; Teva: Membership on an entity's Board of Directors or advisory committees. Shustik:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Millenium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Richter:Amgen: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Jannsen: Speakers Bureau. Chen:Janssen: Honoraria, Research Funding; Takeda: Research Funding; Celgene: Honoraria, Research Funding. Vogl:Takeda: Consultancy, Research Funding; Celgene: Consultancy; GSK: Research Funding; Calithera: Research Funding; Teva: Consultancy; Karyopharm: Consultancy; Acetylon: Research Funding; Constellation: Research Funding. Shacham:Karyopharm Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Baloglu:Karyopharm Therapeutics: Employment, Equity Ownership. Senapedis:Karyopharm Therapeutics: Employment, Equity Ownership. Ellis:Karyopharm Therapeutics: Employment, Equity Ownership. Friedlander:Karyopharm Therapeutics: Employment. Choe-Juliak:Karyopharm Therapeutics: Employment. Sullivan:Karyopharm Therapeutics: Research Funding. Kauffman:Karyopharm Therapeutics Inc: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Background: Molecularly-targeted agents failed to improve outcome in gastric cancer. MK-2206 (Merck & Co., Inc.) is an oral potent allosteric Akt inhibitor. In this study we evaluated the synergistic potential of MK-2206 in combination with selected chemotherapeutic agents (Carboplatinum, Paclitaxel) in human gastric cancer cell lines. Materials and Methods: We evaluated effects of MK-2206 on cell growth and cell signaling using a panel of gastric cancer cell lines AGS, SNU-1 and SNY 16. The analysis of drug combinations was conducted by using CellTiter-Blue™ Cell Viability Assay which yielded the combination index (CI). MK-2206 and representative chemotherapy agent were further evaluated regarding their effects on Akt inhibition and downstream targets using western blots propped with the appropriate antibodies. We assessed the combination of MK-2206 and chemotherapy in three different treatment sequences. Results: We demonstrated in vitro synergistic efficacy of MK-2206 when combined with carboplatinum and paclitaxel in the three cell lines examined. Efficacy was dose dependent. We assessed the combination of MK-2206 and carboplatin/paclitaxel in three different treatment sequences; Twenty-four hours of exposure to combination chemotherapy followed by a 48-hour exposure to MK-2206 resulted in the highest synergistic antiproliferative effect in all cell lines. On the other hand, the reverse sequence (MK-2206 followed by chemotherapy) and the concurrent treatment schedule were slightly synergistic or additive as well. The effects of MK-2206 on p-Akt and other downstream targets will be available at the meeting. Conclusions: Our findings suggest that Akt inhibition augments the efficacy of existing gastric cancer therapeutics (carboplatinum and paclitaxel); thus, MK-2206 is a promising agent to treat gastric cancer patients who receive these cytotoxic agents. The altitude of synergy depended on the treatment sequence; a schedule of MK-2206 dosed before or concurrently with chemotherapy was not as effective as being dosed after chemotherapy. Further experiments addressing MK-2206's mechanism of action in combination with chemotherapy are ongoing. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C87.

Introduction. Multiple myeloma (MM) is an incurable plasma cell malignancy with a growing list of anti-MM therapeutics. However, the development of predictive biomarkers has yet to be achieved for nearly all MM therapeutics. Selinexor (SELI), a nuclear export inhibitor targeting exportin 1 (XPO1), has been approved with dexamethasone (DEX) in penta-refractory MM. Clinical studies investigating promising SELI- 3 drug combinations are ongoing. Here, we have investigated potential synergistic combinations of SELI and anti-MM agents in terms of ex vivo sensitivity, as well as paired RNAseq and WES to identify companion biomarkers. Methods. MM cells isolated from fresh bone marrow aspirates were tested for drug sensitivity in an organotypic ex vivo drug sensitivity assay, consisting of co-culture with stroma, collagen matrix and patient-derived serum. Single agents were tested at 5 concentrations, while two-drug combinations were tested at fixed ratio of concentrations. LD50 and area under the curve (AUC) were assessed during 96h-exposure as metrics for drug resistance. Drug synergy was calculated as a modified BLISS model. Matching aliquots of MM cells had RNAseq and WES performed through ORIEN/AVATAR project. Geneset enrichment analysis (GSEA) was conducted using both AUC and LD50 as phenotypes for single agents and combinations. Both curated pathways (KEGG and cancer hallmarks) and unsupervised gene clustering were used as genesets. Student t-tests with multiple test correction were used to identify non-synonymous mutations in protein coding genes associated with single agent or combination AUC. Results. For this analysis, a cohort of specimens from 103 patients (48% female, 4% Hispanic, 11% African American) was tested with SELI and/or DEX. with a median of 2 lines of therapy (0-12). A smaller cohort of 37 have been examined with SELI, pomalidomide (POM), elotuzumab (ELO) and daratumumab (DARA). Within this cohort we observed synergy between SELI and DEX, POM and ELO as shown in Figure 1. The volcano plot illustrates the number of samples, maximum drug concentration, as well as magnitude (x- axis) and significance (y- axis) of synergy. Although the SELI-DARA combination trended toward synergy, statistical significance was not achieved. To identify molecular mechanisms and biomarkers associated with sensitivity to SELI and SELI- combinations, we investigated paired RNAseq and WES with ex vivo sensitivity. Initially, we conducted GSEA on two cohorts of primary MM samples tested with SELI alone at 5µM (n=53) and 10µM (n=50). Cell adhesion (KEGG CAMS), inflammatory cytokines (KEGG ASTHMA), and epithelial mesenchymal transition (HALLMARK EMT) were associated with resistance in both cohorts, while the HALLMARK MYC TARGETS was associated with sensitivity (FWER p<0.05). Mutational analysis identified 46 gene mutations associated with SELI resistance and 100 associated with sensitivity at 5µM, and 87 and 27 mutations associated with SELI resistance and sensitivity, respectively, at 10µM. Two gene mutations were identified in both cohorts: BCL7A, involved in chromatin remodeling, was associated with sensitivity and CEP290, a microtubule binding protein, associated with resistance (p<0.05). Analysis of both gene sequences (NetNES 1.1) identified nuclear export signal (NES) residues suggesting these may be XPO1 cargo. Additionally, translocation t(11;14) was associated with SELI resistance in the 5µM cohort (p=0.037). The completed set of 50 specimens ex vivo, RNAseq and WES analysis will be mature and updated for the potential presentation at ASH. Conclusions. We observed ex vivo synergy between SELI and DEX, POM and ELO. Molecular analysis of matched ex vivo drug sensitivity, transcriptome and mutational profile identified environment-mediated drug resistance pathways positively correlated with SELI single agent resistance, as well as MYC regulated genes associated with ex vivo sensitivity. We also identified a list of mutations associated with SELI drug resistance and sensitivity, with special emphasis on two novel NES-containing genes, CEP290 and BCL7A. The next step of this project is to analyze transcriptional and mutational patterns associated with ex vivo synergy in the combinations here described, as putative biomarkers for future clinical investigation. Disclosures Shain: Amgen: Speakers Bureau; Adaptive: Consultancy, Honoraria; Karyopharm: Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GlaxoSmithKline: Speakers Bureau; Janssen: Honoraria, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi/Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; AbbVie: Research Funding. Kulkarni:M2GEN: Current Employment. Zhang:M2GEN: Current Employment. Hampton:M2GEN: Current Employment. Argueta:Karyopharm: Current Employment. Landesman:Karyopharm Therapeutics Inc: Current Employment, Current equity holder in publicly-traded company. Siqueira Silva:AbbVie: Research Funding; NIH/NCI: Research Funding; Karyopharm: Research Funding.

Combination therapy utilizing 2 novel agents with independent mechanisms of action and non-overlapping toxicities may be useful in the setting of advanced cancers. Tipifarnib (T) is an orally bioavailable farnesyltranferase inhibitor with documented single-agent activity in acute myeloid leukemia (AML). Bortezomib (B) is a broad inhibitor of proteasomal function, approved for treatment in multiple myeloma and mantle cell lymphoma. Preclinical studies indicated synergistic activity between these 2 agents for eliciting apoptosis within leukemia and myeloma cell lines and ex-vivo cells adhered to fibronectin. In this phase I combination trial, we studied the effect of combined effect of T plus B in patients with advanced acute leukemias. Objectives: The primary endpoint was toxicity assessment. Secondary endpoints included effect of combined therapy on signaling intermediates, including p-AKT, Bim, Bax, and NF-kB, as well as effects on farnesyltransferase (FT) and the proteasome activity. Eligibility: Patients with AML, ALL, or CML-BC who had received < 3 cycles of prior therapy were eligible. Methods: Patients received T on days 1–14 and B on days 1, 4, 8, and 11. Cycles were repeated every 21 days. Dose escalation occurred using cohorts of 3–6 patients. The starting dose was T: 300 mg/m2 and B: 1.0 mg/m2 Bone marrow aspirate was obtained at baseline, day 8, and between day 15 and the start of the next cycle. Measurement of signaling intermediates were performed in Ficoll-enriched leukemic marrow blasts using Western Blot (p-AKT, Bax, Bim) and ELISA (NF-kB). FT and proteasomal activity were directly measured within peripheral blood mononuclear cells (PBMC) using previously described methods. Results: To date, 27 patients have been enrolled at 3 centers. Four patients were ineligible after screening, and 23 patients have been treated. Median age was 69 years (range 48–84) Diagnosis: AML=25, ALL=1, MDS=1. Accrual to the 4th and final dosing cohort has occurred, without maximum tolerated dose being reached at the 4th and final planned dosing cohort (T: 600 mg/m2 and B: 1.3 mg/m2). Six patients received ≥ 2 cycles of treatment. Dose-limiting toxicities to date have included: nausea/diarrhea (1 patient), sensory neuropathy (1 patient), and fatigue (1 patient). Common drug-related (> 10%) non dose-limiting toxicities included: infection/febrile neutropenia, diarrhea, nausea, vomiting, sensory neuropathy, and fatigue, most of which were grade 1 or 2. FTase inhibition within peripheral blood mononuclear cells (PBMC) was measured serially in 8 patients to date, with a median of 70% inhibition by day 8, and with 5 out of 6 evaluable patients having sustained inhibition at day 22. Proteasome function within PBMCs was reduced by a median of 44.3% in 7 patient samples pre-infusion and 1 hour post-infusion on day 8. Proteasome activity within PBMCs at day 22 was decreased from baseline in 5 out of 7 patient samples tested. Compared to baseline, NF-kB binding activity within leukemic blasts at day 8 was decreased by a median of 39% at in 10 out of 14 paired samples. No significant change in expression of p-AKT, Bax, or Bim, as measured by Western Blot, was detected at day 8. Two patients achieved clinical response; 1 patient had a complete response and another patient had complete response with incomplete count recovery. Four others had stable disease following cycle 1. Conclusion: combined therapy with T + B was well tolerated and demonstrated inhibition of several relevant target signals within leukemic blasts and PBMCs. In addition, clinical activity was seen in 2 patients to date. Accrual to the trial is ongoing and updated clinical and pharmacodynamic data will be presented.

Purpose Human multiple myeloma (MM) remains an incurable disease despite relatively effective treatments, including proteasome inhibitors, immunomodulator-based therapies, and high-dose chemotherapy with autologous stem cell rescue. New agents are needed to further improve treatment outcomes. In previous studies, we have shown that inhibitors of the nuclear export receptor XPO1, in combination with bortezomib, carfilzomib, doxorubicin, or melphalan, synergistically induced apoptosis in MM cells in vitro, in vivo and ex vivo without affecting non-myeloma cells. In early clinical trials, the oral, brain penetrating XPO1 inhibitor selinexor showed clear anti-myeloma activity however adverse events have been recorded, including nausea and anorexia. Our purpose was to investigate the use of oral KPT-8602, a novel small-molecule inhibitor of XPO1 with minimal brain penetration, which has been shown to have reduced toxicities in rodents and primates while maintaining potent anti-tumor effects. Experimental Procedures To test the efficacy of KPT-8602, we treated human MM cell lines (both parental and drug-resistant) with KPT-8602 ± currently used MM drugs, including bortezomib, carfilzomib, dexamethasone, doxorubicin, lenalidomide, melphalan, topotecan, and VP-16. Human MM cell lines assayed included RPMI-8226 (8226), NCI-H929 (H929), U266, and MM1.S, PI-resistant 8226-B25 and U266-PSR, doxorubicin-resistant 8226-Dox6 and 8226-Dox40, and melphalan-resistant 8226-LR5 and U266-LR6 cell lines. MM cells (2-4x106 cells/mL) were treated for 24 hours with KPT-8602 (300 nM), followed by treatment with one of the listed anti-MM agents for an additional 24 hours. MM cells were then assayed for cell viability (CellTiter-Blue, Promega). In addition, cells were treated with KPT-8602 ± anti-MM agents concurrently for 20 hours and assayed for apoptosis by flow cytometry. In vivo testing was done in NOD/SCID-g mice by intradermal injection of U266 MM cells. Treatment started 2 weeks after tumor challenge with KPT-8602 (10 mg/kg) ± melphalan (1 or 3 mg/kg) 2X/week (Tuesday, Friday) or with KPT-8602 alone 5X weekly (10 mg/kg) (Monday-Friday). A parallel experiment was run using the clinical XPO1 inhibitor KPT-330 (selinexor). Ex vivo testing was performed on MM cells from newly diagnosed/relapsed patient bone marrow aspirates with KPT-8602 ± bortezomib, carfilzomib, dexamethasone, doxorubicin, lenalidomide, melphalan, topotecan, or VP16. CD138+/light-chain+ cells were assayed for apoptosis by flow cytometry. Results Viability assay showed that KPT-8602 had low IC50values (~140 nM) as a single agent and functioned synergistically with bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16. (CI values < 1.0). This synergistic effect was less pronounced in myeloma cells when KPT-8602 was used in combination with dexamethasone or lenalidomide. KPT-8602 ± bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16 combination therapy also induced apoptosis in all MM cell lines tested, including drug-resistant cell lines, as shown by caspase 3 cleavage and flow cytometric analyses. NOD/SCID-gamma mouse tumor growth was reduced and survival increased in KPT-8602/melphalan-treated mice when compared to single-agent controls. In addition, mice treated with KPT-8602 5X weekly had significantly reduced tumor growth and increased survival when compared to 2X weekly drug administration. No toxicity was observed in KPT-8602-treated mice as determined by weight loss in both the 2X and 5X groups. In patient bone marrow biopsies, the combination of KPT-8602 ± bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16 was more effective than single agents at inducing apoptosis in CD138+/LC+ MM cells in both newly diagnosed and relapsed/refractory patient samples. Conclusions We found that the novel XPO1 inhibitor KPT-8602 sensitizes MM cells to bortezomib, carfilzomib, doxorubicin, melphalan, topotecan, and VP16 as shown by apoptosis in parental and drug-resistant cell lines and by cell viability assays. Sensitization was found to be synergistic. In addition, KPT-8602 was effective in treatment of human MM tumors in mice as a single agent or in combination with melphalan and was effective when combined with several MM drugs in MM cell lines and MM patient bone marrow aspirates. KPT-8602 may be a potential candidate for future clinical trials. Disclosures Shacham: Karyopharm: Employment, Equity Ownership. Senapedis:Karyopharm Therapeutics, Inc.: Employment, Patents & Royalties.

Background: Induction chemotherapy for older adults with poor-risk AML has remained largely unchanged over the past 40 years, with complete remission (CR) rates ranging from 20-50%. Five-year overall survival (OS) ranges from 2-15%, illustrating the need for novel treatment strategies. Selinexor is an oral selective inhibitor of nuclear export (SINE) that has shown promising single agent activity in AML (NCT01607892). By inhibiting the primary export protein, XPO1, selinexor localizes tumor suppressor proteins to the nucleus leading to their activation. Furthermore, selinexor inhibits DNA damage repair, rationalizing its use in combination with DNA damaging agents. Preclinical data from our institution suggest Selinexor synergizes with daunorubicin when used in CD34+ AML cells. Here we report early results from a phase I clinical trial with selinexor plus cytarabine and daunorubicin in patients (pts) with newly diagnosed, poor-risk AML. Methods: This is a single institution phase I clinical trial with a 3+3 design and an expansion phase at the maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D). The primary endpoint was to determine the MTD/RP2D of selinexor. Secondary endpoints included rate of CR/CRi, overall survival (OS), relapse free survival (RFS) and toxicity assessment. Eligible pts had a diagnosis of previously untreated AML (non-M3), with poor-risk features based on karyotype, mutational profile, secondary AML (sAML) arising from an antecedent hematologic disorder (AHD) or prior chemotherapy, or age ≥60 years. Prior treatment for an AHD was allowed. Induction included daunorubicin 60 mg/m2/day on days 1-3 and cytarabine 100 mg/m2/day CIVI days 1-7 (7+3) with two dose cohorts of selinexor: 60 mg and 80 mg PO. Selinexor was given on days 1, 3, 8, 10, 15 and 17. Re-induction with 5+2 plus selinexor was allowed if indicated. Once in CR, pts received 1-2 cycles of consolidation with 5+2 plus selinexor followed by maintenance selinexor on days 1 and 8 of a 21 day cycle for up 12 months. Selinexor was given at the same dose for all phases of the study. Pts could proceed to hematopoietic stem cell transplant (HCT) at any time after achieving CR. Results: 21 pts (14 (67%) M / 7 (33%) F) were enrolled from June 2015 to June 2016. Median age was 68 years (range 37-77); 18 (86%) were age ≥60 and 9 (43%) were age ≥70. Nineteen (90%) pts were considered poor-risk (unrelated to age), and two (10%) were eligible due to age ≥60 only. Each cohort enrolled 4 pts, and 13 pts were enrolled in the expansion. One pt in each cohort was replaced before completing the 28-day DLT period; one withdrew consent and the second died on day 23 from acute renal failure related to antibiotics. At data cutoff, 18 pts were included in the safety and efficacy assessment. Three additional patients have not completed induction. The early death rate (≤60 days) was 4.8%. No DLTs occurred in the dose-escalation cohorts. The MTD of selinexor was not reached and the RP2D was 80 mg twice weekly. The most common grade 3/4 non-hematologic, treatment emergent AEs in all pts were febrile neutropenia (56%), diarrhea (22%), hyponatremia (22%) and sepsis (17%). Nine patients (50%) achieved CR/CRi. Of the 14 pts treated at the RP2D (selinexor 80 mg), 6 (43%) achieved CR/CRi. In the entire cohort, the median age of the responders was 69 (61-77) and 4 (44%) were age ≥70. Seven (78%) were considered high-risk. Four (44%) had sAML. Two (22%) required a second induction. The median time to response was 47 days (range 28-77) At a median follow up of 8.7 months in the 9 responding pts, 7 (78%) remain in remission. Overall, 4 pts (44%) underwent HCT, and 1 (11%) relapsed just prior to HCT. Conclusion: Results from this phase I trial suggest that selinexor 80mg PO twice weekly can be safely administered in combination with induction chemotherapy using cytarabine and daunorubicin to pts with poor-risk AML, including older pts. The most prominent AEs were febrile neutropenia, diarrhea and hyponatremia. Response rates are encouraging and many elderly pts proceeded to transplant, suggesting this regimen warrants further investigation in this challenging population. Disclosures Sweet: Karyopharm: Honoraria, Research Funding; Incyte Corporation: Research Funding; Novartis: Consultancy, Speakers Bureau; Ariad: Consultancy, Speakers Bureau; Pfizer: Speakers Bureau. Komrokji:Novartis: Consultancy, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Sullivan:Karyopharm: Research Funding. Shah:Incyte: Research Funding; Rosetta Genomics: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Baxalta: Membership on an entity's Board of Directors or advisory committees; Bayer: Honoraria; Pfizer: Honoraria.