ALBERT

Description: Patients with relapsed or refractory (R/R) non-Hodgkin lymphoma (NHL) have a poor prognosis and limited treatment options. We evaluated selinexor, an orally bioavailable, first-in-class inhibitor of the nuclear export protein XPO1, in this phase 1 trial to assess safety and determine a recommended phase 2 dose (RP2D). Seventy-nine patients with various NHL histologies, including diffuse large B-cell lymphoma, Richter’s transformation, mantle cell lymphoma, follicular lymphoma, and chronic lymphocytic leukemia, were enrolled. In the dose-escalation phase, patients received 3 to 80 mg/m2 of selinexor in 3- or 4-week cycles and were assessed for toxicities, pharmacokinetics, and antitumor activity. In the dose-expansion phase, patients were treated with selinexor at 35 or 60 mg/m2. The most common grade 3 to 4 drug-related adverse events were thrombocytopenia (47%), neutropenia (32%), anemia (27%), leukopenia (16%), fatigue (11%), and hyponatremia (10%). Tumor biopsies showed decreases in cell-signaling pathways (Bcl-2, Bcl-6, c-Myc), reduced proliferation (Ki67), nuclear localization of XPO1 cargos (p53, PTEN), and increased apoptosis after treatment. Twenty-two (31%) of the 70 evaluable patients had an objective responses, including 4 complete responses and 18 partial responses, which were observed across a spectrum of NHL subtypes. A dose of 35 mg/m2 (60 mg) was identified as the RP2D. These findings suggest that inhibition of XPO1 with oral selinexor at 35 mg/m2 is a safe therapy with encouraging and durable anticancer activity in patients with R/R NHL. The trial was registered at www.clinicaltrials.gov as #NCT01607892.

Description: Introduction: Exportin 1 (XPO1) is a well characterized and essential nucleo-cytoplasmic transport protein in the karyopherin family, and is responsible for the nuclear export of over 200 cargo proteins, including the major tumor suppressor proteins (TSPs) p53, p21, FOXO and the translation regulator elF4E. XPO1 is overexpressed in numerous cancer types including solid and hematological malignancies, often correlating with poor prognosis. Recently, a novel class of Selective Inhibitors of Nuclear Export (SINE) compounds, selinexor (KPT-330) and the second generation KPT-8602, have been developed for the treatment of advanced cancers. We have previously shown that selinexor has marked activity in AML and DLBCL pre-clinical models. The BCL-2 family of anti-apoptotic proteins are deregulated and linked to maintenance and survival in AML and DLBCL. For its translation, the mRNA for BCL-2 is transported from the nucleus to the cytoplasm by forming a complex with XPO1 cargo, elF4E. Other important mRNAs exported from the nucleus via this mechanism include BCL6 and MYC. We hypothesize that SINE compounds inhibit XPO1/elF4E-mediated nuclear-cytoplasmic transport by covalently binding to the XPO1 cargo binding site and that in the absence of protein translation, BCL-2, BCL6 and MYC levels rapidly decline. Venetoclax (VEN; ABT-199) is a potent, selective inhibitor of BCL-2. In vitro, AML cells acquire resistance to VEN over time, often due to up-regulation of another BCL-2 family anti-apoptotic protein, MCL-1. MCL-1 is regulated by the anti-apoptotic transcription factor and XPO1 cargo NF-kB. We have previously shown that SINE compounds significantly decreased MCL-1 levels, presumably via inactivation of NF-kB. The goal of this study was to test whether SINE compounds will synergize with VEN via BCL-2 modulation and whether the combination would diminish MCL-1 mediated resistance to BCL-2 inhibition in DLBCL and AML models, respectively. Methods: BH3 profiling was performed in a sample of cell lines using a cytochrome c release assay to identify anti-apoptotic dependencies. The effects of SINE compounds and VEN as single agents or in combination on cell viability were performed in AML (K-562, MOLM-13, MV-4-11, and U-937) and DLBCL cell lines (SU-DHL-6, DoHH-2 and Toledo). Whole cell protein lysates were extracted 24 hours after treatment for immunoblot analysis. The activity of SINE compounds (5 mg/kg) and VEN (25 mg/kg) as single agents, or in combination were measured in AML (MV-4-11) and DLBCL (DoHH-2 and Toledo) xenografts in NSGS and nude mice, respectively. Tumor growth and survival were measured throughout these animal studies. Tumor tissue was collected at the end of treatment for flow cytometric analysis, western blotting and immunohistochemistry (IHC). Results: By employing BH3 profiling, we identified AML cell lines that were dependent (MV-4-11 and MOLM-13) and not dependent (U-937 and K-562) on MCL-1. Dose response analysis demonstrated that each of the AML cell lines was sensitive to the SINE compounds, while VEN only reduced viability in the MV-4-11 and MOLM-13 cells. Additionally, there was enhanced growth inhibition when the SINE compounds were combined with VEN in the MCL-1 dependent cells. SINE compound treatment synergistically decreased c-MYC protein levels in all 4 AML cell lines with the combination treatment (Figure 1), whereas PARP cleavage was only enhanced with the combination in the MV-4-11 and MOLM-13 cells. Likewise, MCL-1 is reduced in the presence of SINE compound or SINE compound-VEN combinations. In DLBCL xenograft studies (DoHH-2 and Toledo), combination of selinexor with VEN was synergistic for tumor reduction and increased animal survival when compared to either single agent alone. By IHC we observed a concomitant reduction in BCL-2 and BCL-6 and an increase in cleaved caspase 3 in DLBCL tumors after combination treatment. Conclusions: SINE compound-VEN combinations show enhanced antitumor effect, with reduction of oncogenic activity. SINE compounds reduce MCL-1 in VEN-resistant cells. As MCL-1 driven anti-apoptotic machinery is responsible for resistance to inhibition of BCL-2 in DLBCL and AML, SINE compound regulation of MCL-1 may lead to rescue of VEN resistance. SINE compounds and VEN are excellent candidate partners for combination therapies in AML and DLBCL. Disclosures Friedlander: Karyopharm Therapeutics: Employment. Chang:Karyopharm Therapeutics: Employment, Equity Ownership. Kashyap:Karyopharm Therapeutics: Employment, Equity Ownership. Argueta:Karyopharm Therapeutics: Employment, Equity Ownership. Klebanov:Karyopharm Therapeutics: Employment, Equity Ownership. Senapedis:Karyopharm Therapeutics: Employment, Equity Ownership. Baloglu:Karyopharm Therapeutics: Employment, Equity Ownership. Lee:Karyopharm Therapeutics: Employment, Equity Ownership. Shacham:Karyopharm Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Savona:TG Therapeutics: Research Funding; Amgen Inc.: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; Sunesis: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Ariad: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees.

Description: 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.

Description: Background Selinexor (KPT-330), a selective inhibitor of nuclear export (SINE) Exportin 1 (XPO1, CRM1) antagonist, has shown potent activity against solid and hematological malignancies in phase 1 clinical trials. Inactivation of XPO1 by selinexor results in accumulation of tumor suppressor proteins in the nucleus and activation of cell cycle checkpoints. This leads to transient cell cycle arrest in normal cells and irreversible arrest and cell death in cancer cells. Thrombocytopenia is a common side effect of selinexor and we aim to define the mechanism of selinexor-induced thrombocytopenia to potentially help in its clinical management. In this study, we have examined the effects of selinexor on platelet count in humans and mice. Additionally, we investigated the effects of selinexor on differentiation and maturation of megakaryocytes (MKs) in culture as a model system for understanding the effects on platelet levels in humans. Methods Platelet counts were measured in solid tumor patients in a Phase 1 trial of selinexor QoDx2 weekly. For in vivo studies, CD1 mice were treated with high-dose selinexor (20 mg/kg QoDx3) for 3 weeks and platelet number was determined in peripheral blood. In addition, femur bone marrow samples were analyzed histologically. In vitro, MK progenitors were isolated from fetal mouse livers, and MK maturation and platelet production was analyzed by microscopy, flow cytometry and immunofluorescence. In addition, whole protein lysates from selinexor-treated MKs were analyzed to detect changes in XPO1 and its cargo proteins. Results A majority of solid tumor patients treated with selinexor QoDx2 weekly in a Phase 1 trial for at least 1 cycle (4 wks) had 〉40% reduction in platelet count within the first cycle (72%, N=50), with an average maximal reduction of 50% after 20 days. These reductions were independent of pre-dose platelet count, did not typically decrease further after the first cycle, and recovered following dose reduction or cessation of treatment. Also, administration of the thrombopoietin (TPO) receptor agonists romiplostim and eltrombopag were found to reduce selinexor mediated thrombocytopenia. As in the clinical studies, selinexor reduced the platelets in mice by 40-50% within 2-3 weeks. In studies of MKs in cell culture, selinexor inhibited XPO1 mediated nuclear export as shown by nuclear localization of IkBa and FOXO3a proteins, but was not cytotoxic to MKs or platelets in vitro and did not affect platelet activation. However, MK progenitor cell development was significantly blocked in a dose dependent fashion, with 200 nM selinexor inducing a reduction of 81% in the number of progenitor cells that differentiated into MKs. The same dose of selinexor also affected endomitosis, a marker of MK maturation, shifting ploidy from predominantly 16N to 2N. Importantly, these effects were substantially reversible. When selinexor was washed out after 6 hours of treatment, the number of progenitor cells that differentiated into MKs was 65%, accompanied by reversion to 16N ploidy. Interestingly, MK inhibition was decreased when cells were treated later in the differentiation process and treatment of mature MKs did not decrease pro-platelet formation or release, suggesting selinexor affected an earlier stage in MKs development. Conclusions Selinexor induces reductions in platelets in humans and mice. Our results suggest that this adverse effect is likely due to inhibition of the early commitment and differentiation phase of MK maturation from progenitor cells, and not a cytotoxic effect on normal stem cells or MKs. The reversibility of the effect in cell culture is congruent with the observations that selinexor-induced thrombocytopenia is reversible in humans upon dose interruption or reduction and/or the use of TPO receptor agonists by relieving the progenitor cell to MK differentiation block. Based on these results, the recommended Phase 2 dosing regimen of selinexor is twice weekly (days 1 and 3) for 3 weeks, followed by a 10-day dosing holiday and treatment with a TPO agonist if platelet counts are very low. Disclosures Machlus: Karyopharm Therapeutics: Research Funding. Wu:Karyopharm Therapeutics: Research Funding. Carlson:Karyopharm Therapeutics: Employment. Friedlander:Karyopharm Therapeutics: Employment. Kashyap:Karyopharm Therapeutics: Employment. Kalid:Karyopharm Therapeutics: Employment. Shacham:Karyopharm Therapeutics: Employment. Rashal:Karyopharm Therapeutics: Employment. Shacham:Karyopharm Therapeutics: Employment. Italiano:Karyopharm Therapeutics: Research Funding. Landesman:Karyopharm Therapeutics: Employment.

Description: Introduction - With over 12,000 deaths from MM anticipated in 2016, nearly all patients (pts) with multiple myeloma (MM) will become "quad refractory" to IMIDs (lenalidomide and pomalidomide) and proteasome inhibitors (bortezomib and carfilzomib), and eventually "penta refractory" to anti-CD38 Abs (daratumumab and isatuximab), defining high unmet need populations. Selinexor, an oral selective XPO1 inhibitor, induces nuclear accumulation and activation of tumor suppressor proteins, inhibition of NF-kB, and inhibition of translation of several oncoprotein mRNAs such as c-myc and cyclin D. Selinexor showed potent induction of apoptosis of MM cells independent of p53 signaling. In phase 1 clinical studies, selinexor with low dose dexamethasone (Sd) demonstrated potent anti MM activity in pts with MM. Methods - This phase II clinical trial evaluated Sd in pts with MM refractory to bortezomib, carfilzomib, lenalidomide, and pomalidomide ("quad"), with a subset also refractory to an anti-CD38 Ab ("penta"). Inclusion required CrCL≥20 mL/min, ANC≥1000/µL, platelets ≥50K/µL (≥30K if plasma cells were ≥50% of marrow cellularity). Pts were treated twice weekly (BIW) with oral selinexor 80 mg for 6 or 8 doses per 28 day cycle and dexamethasone (dex) 20 mg BIW. All pts received 5-HT3 antagonists. The primary objective was to determine the overall response rate (ORR) per IMWG criteria and duration of response (DOR), both adjudicated by an independent review committee (IRC). Secondary endpoints include progression free survival (PFS) and overall survival (OS). FISH analyses and gene expression profiling were performed on bone marrow aspirates. Results - 79 pts were enrolled: 48 quad (24 M/24 F, median age 62 yrs) and 31 penta (13 M / 18 F, median age 68 yrs). Both groups had a median of 7 prior treatment regimens including multiple dex-containing regimens. Baseline laboratory abnormalities included grade (Gr)≥3 anemia in 13% and Gr≥3 thrombocytopenia in 8%. Most penta pts received 8 doses / cycle (65%); most quad pts received 6 doses / cycle (83%). Common treatment-related adverse events (TRAEs) hematological: thrombocytopenia (72%, Gr 3/4 58%), anemia (48%, Gr 3 25%) and neutropenia (29%, Gr≥3 21%). TRAEs non-hematological: nausea (72%, Gr 3 6%), fatigue (62%, Gr 3 14%) anorexia (49%, Gr 3 3%), vomiting (43%, Gr3 4%), asymptomatic hyponatremia (42%. Gr 3 20%), diarrhea (42%, Gr 3 5%) and weight loss (33%, Gr 3 1%). There was one case of febrile neutropenia (1%) and one case of clinically significant bleeding related to thrombocytopenia (1%). Seventy pts have discontinued therapy: PD (73%), AEs (17%), physician/pt preference (1%) and 6 deaths (one case related to selinexor, intracranial bleed in pt with Gr4 thrombocytopenia). Nine pts remain on study. Efficacy was evaluated in 78 pts (1 pt did not have measurable disease). The IRC-determined ORR (≥PR) for all pts was 21%, including 5% VGPR. ORR was 21% for quad pts and 20% for penta pts. Clinical benefit rates (≥MR) were 32% (all), 29% (quad), and 37% (penta). Median OS was 9.3 months (mo) for all pts, 〉11 mo (median not reached) for responders (≥PR), and 5.7 mo for non-responders. Median DOR in responding pts was 5 mo, and median PFS in all pts was 2.1 mo. Baseline cytogenetics were assessed in 41 pts. The ORR in 18 pts with high-risk FISH abnormalities was 33% (Table 1). Notably, 3 of the 13 pts with a 17p abnormality responded (ORR 23%). Transcriptomic profiling revealed differentially expressed genes (DEGs) between responders and non-responders in both whole blood RNA and CD138+ bone marrow cells. Pathways enriched in responders included IL-6, IL-8 and IGF-1 pathways. Conclusions - Oral Sd is active in heavily pretreated pts with refractory MM, including those with MM refractory to anti-CD38 Ab and those with high-risk cytogenetic abnormalities. Response was associated with longer survival. The main toxicities of Sd are thrombocytopenia, nausea, anorexia, and fatigue. AEs were manageable with supportive care and dose interruptions/reductions. To our knowledge, this is the first report of anti-tumor activity in the penta-refractory MM population. This population of MM pts has exhausted all currently available treatment options and has an extremely poor prognosis and therefore requires new therapies. Expansion of this trial in this high unmet medical need, penta refractory population is planned. Table 1 Activity of Sd in Patients with High Risk MM Cytogenetics Table 1. Activity of Sd in Patients with High Risk MM Cytogenetics Disclosures Vogl: Constellation: Research Funding; Karyopharm: Consultancy; Acetylon: Research Funding; GSK: Research Funding; Calithera: Research Funding; Teva: Consultancy; Celgene: Consultancy; Takeda: Consultancy, Research Funding. Jagannath:Bristol-Myers Squibb: Consultancy; Janssen: Consultancy; Novartis: Consultancy; Merck: Consultancy; Celgene: Consultancy. Baz:Bristol-Myers Squibb: Research Funding; Takeda/Millennium: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Signal Genetics: Research Funding; Novartis: Research Funding; Karyopharm: Research Funding; Merck: Research Funding. Nooka:Spectrum, Novartis, Onyx pharmaceuticals: Consultancy. Richter:Takeda: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Janssen: Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau. Vij:Karyopharm: Honoraria; Amgen: Honoraria, Research Funding; Celgene: Consultancy; Takeda: Honoraria, Research Funding; Novartis: Honoraria; Bristol-Myers Squibb: Honoraria; Janssen: Honoraria. Schiller:Incyte Corporation: Research Funding. Costa:Sanofi: Honoraria, Research Funding. Chari:Array Biopharma: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Pharmacyclics: Research Funding; Janssen: Consultancy, Research Funding; Amgen Inc.: Honoraria, Research Funding; Novartis: Consultancy, Research Funding. Siegel:Takeda: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Amgen: Honoraria, Speakers Bureau; Celgene: Honoraria, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Merck: Honoraria. Fonseca:Janssen: Consultancy; AMGEN: Consultancy; Millennium, a Takeda Company: Consultancy; Bayer: Consultancy; Sanofi: Consultancy; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; AMGEN: Consultancy; Novartis: Consultancy; Millennium, a Takeda Company: Consultancy; Sanofi: Consultancy; AMGEN: Consultancy; Janssen: Consultancy; BMS: Consultancy; Celgene: Consultancy; BMS: Consultancy; Millennium, a Takeda Company: Consultancy; Millennium, a Takeda Company: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Bayer: Consultancy; Novartis: Consultancy; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; AMGEN: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Celgene: Consultancy. Kauffman:Karyopharm Therapeutics Inc: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Shacham:Karyopharm Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Saint-Martin:Karyopharm: Employment. Picklesimer:Karyopharm: Employment. Friedlander:Karyopharm Therapeutics: Employment. Choe-Juliak:Karyopharm Therapeutics: Employment.

Description: Background: XPO1 (Exportin-1/CRM1) is the non-redundant nuclear exporter of over 200 cargos including the major tumor suppressor proteins. Deregulated nuclear export by changes in XPO1 expression is a common characteristic for a broad range of cancers and may aid in the evasion of anti-neoplastic mechanisms. As a result, inhibition of XPO1 has emerged as a promising area of cancer treatment. The Selective Inhibitor of Nuclear Export (SINE) compounds, selinexor, as well as a second generation, KPT-8602, bind to the XPO1 cargo binding pocket and disrupt XPO1-mediated nuclear export, resulting in cancer specific cell death. Although selinexor has been evaluated in 〉1,500 patients and has manageable tolerability, KPT-8602 may have improved tolerability and efficacy based on decreased brain penetration in animal models allowing more frequent dosing. Currently, the safety, tolerability and efficacy of KPT-8602 is being evaluated in a phase 1 trial of patients with relapsed/refractory multiple myeloma (MM; NCT02649790). Since selinexor synergizes with a broad array of anti-MM agents in patients, KPT-8602 is an excellent candidate for combination therapies. In this study, we investigated the use and mechanism of combining KPT-8602 with the pan-histone deacetylase (HDAC) inhibitor, panobinostat, in MM cell lines and in a xenograft mouse model of MM. Methods : MM.1S cells were treated with single agent KPT-8602, panobinostat or a combination of both. The effects of KPT-8602 and/or panobinostat on cell viability were examined using standard viability assays after 72 hours of treatment. Total RNA or protein levels were examined after 24 hours using quantitative PCR or immunoblots, respectively. Immune compromised mice were injected subcutaneously with MM.1S cells. Tumors were allowed to grow to ~150 mm3before treatment. The mice were treated with vehicle, sub-therapeutic doses of KPT-8602 (5 mg/kg PO QDx5) or panobinostat (5 mg/kg IP QDx5) alone or in combination. Tumor growth and animal weights was monitored to determine tumor growth inhibition (TGI), tumor regression, and tolerability to treatment. The tumors were then harvested for immunohistochemical (IHC) analysis. Results : The combination of KPT-8602 and panobinostat was highly effective against MM.1S cell viability. A synergistic anti-cancer effect was observed against MM.1S cells grown in culture and in mice. In cells, the MTT IC50of KPT-8602 was shifted from 50 to 23 nM by the addition of sub cytotoxic concentrations of panobinostat. In mice, single agent treatment with KPT-8602 led to 96.5% tumor growth inhibition whereas panobinostat resulted in 69.4% tumor growth inhibition within 22 days. Remarkably, in the combination of KPT-8602 and panobinostat, 3 out of 8 tumors totally disappeared and the overall tumor regression was 95%, (Figure 1). Both drugs, as single agents and in combination were well tolerated and no significant changes in weight were observed. Gene and protein expression studies revealed that although both compounds target independent proteins (e.g. HDACs or XPO1), the combination significantly enhances markers of cell death (cleavage of PARP-1, caspase-3, etc.). Curiously, KPT-8602 enhances the inhibitory effect panobinostat has on deacetylation as evidenced by histone acetylation. Moreover, DNA damage, as indicated by ϒ-H2AX, significantly increases in the presence of both compounds. Conclusion : KPT-8602 and panobinostat are dissimilar drugs with unique mechanisms of action, and individually affect a broad range of cellular processes. Here we show that the combination of these drugs can dramatically increase the already potent anti-cancer properties of these compounds in MM cell lines. In addition, KPT-8602 enhances the inhibitory effect exerted by panobinostat on histone deacetylation, which coincides with an increase induction of DNA damage. It should be noted that both panobinostat and SINE compounds have been shown to downregulate checkpoint and DNA damage response (DDR) proteins (e.g. RAD51 and Chk1). We hypothesize that the combination of KPT-8602 and panobinostat promotes significant chromatin remodeling in the presence of a compromised DDR pathway, which destabilizes genomic integrity in MM cells and leads to a synergistic effect on cell viability. Together, these data provide rational support for the study of KPT-8602 and panobinostat in clinical trials. Figure 1 Figure 1. Disclosures Argueta: Karyopharm Therapeutics: Employment, Equity Ownership. Chang:Karyopharm Therapeutics: Employment, Equity Ownership. Kashyap:Karyopharm Therapeutics: Employment, Equity Ownership. Elloul:Rubius Therapeutics: Employment. Friedlander:Karyopharm Therapeutics: Employment. Lee:Karyopharm Therapeutics: Employment, Equity Ownership. Kauffman:Karyopharm Therapeutics Inc: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Shacham:Karyopharm Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Senapedis:Karyopharm Therapeutics: Employment, Equity Ownership. Baloglu:Karyopharm Therapeutics: Employment, Equity Ownership.

Description: Background TAK-981 is a first-in-class, small molecule inhibitor of SUMOylation, a reversible post-translational modification that regulates protein function by covalent attachment of small ubiquitin-like modifier (SUMO) proteins to a protein substrate. SUMOylation has a key role in restraining Type I interferon (IFN) responses (Decque, Nature Immunology 2016; Seeler, Nat Rev Cancer 2017). In-vivo preclinical studies have demonstrated that inhibition of SUMOylation by TAK-981 promotes innate and adaptive antitumor immune responses dependent on induction of Type I IFN signaling. This includes modulating the activity of innate effector cells. In macrophages, TAK-981 induced polarization towards the M1 phenotype, upregulated Fcγ receptors, and enhanced phagocytosis and antibody-dependent cellular phagocytosis (ADCP) in an ex-vivo assay. In natural killer (NK) cells, TAK-981 promoted upregulation of the activation marker CD69 and the degranulation marker CD107, increased the number of IFNγ+ NK cells in tumors, and enhanced cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) in an ex-vivo assay. This enhancement of ADCP and ADCC supports the combination of TAK-981 with IgG1 therapeutic monoclonal antibodies. In-vivo studies have demonstrated synergistic antitumor activity with TAK-981 combined with rituximab in severe combined immunodeficient mice (lacking lymphocytes but retaining a functional innate immune system) bearing human diffuse large B-cell lymphoma xenografts. Specifically, in OCI-Ly-10 and TMD8 tumor models, the combination reproducibly resulted in complete regression (CR) of all treated tumors at doses at which no CRs were achieved with either single agent. In the PHTX-166L patient-derived xenograft model, tumor growth delay and 1 CR were achieved at doses that showed only very modest tumor growth delay with single agents. Methods This is an open-label, multicenter, non-randomized, phase 1b/2 study investigating the safety and efficacy of TAK-981 in combination with rituximab in adult patients with CD20-positive r/r NHL. The study comprises Phase 1b (dose escalation) and Phase 2 (2 treatment arms: indolent [iNHL] and aggressive [aNHL] NHL). Eligible patients must have CD20-positive r/r NHL (excluding mantle cell lymphoma in Phase 2) and have failed ≥2 prior lines of therapy; one prior line of therapy must have included a CD20-directed antibody. TAK-981 will be administered intravenously (IV) on Days 1 and 8 in 21-day cycles. The starting dose will be informed by the ongoing first-in-human TAK-981-1002 Phase 1 trial (NCT03648372). Rituximab will be administered IV weekly at 375 mg/m2 x 3 doses followed by 375 mg/m2 on Day 1 of subsequent 21-day cycles. Treatment will continue until disease progression or unacceptable toxicity. Phase 1b will enroll ~34 patients to identify the maximum tolerated dose and/or pharmacologically active dose of the combination. Dose escalation will be guided by an adaptive Bayesian logistic regression model that implements escalation with overdose control. Phase 2 will enroll ~56 patients in 2 parallel arms (iNHL/aNHL). Efficacy of the combination will be assessed by the investigator per Lugano 2014 response criteria. The primary endpoint for Phase 2 is overall response rate (ORR). The design is based on Simon's 2-stage design, in which the null hypothesis for each arm (true ORR is 20%) will be tested against a one-sided alternative. In the first stage, 12 patients will be accrued in each arm. If there are ≤2 responses in the 12 patients in either arm, the arm(s) will be stopped. Otherwise, 13 additional patients will be accrued per arm. The null hypothesis will be rejected for an arm if ≥8 responses are observed in the 25 patients on that arm. This design yields a type I error rate of 0.1 and 80% power when the true ORR is 40%. Tumor biopsies will be collected to determine SUMO pathway inhibition by immunohistochemistry and the induction of innate and/or adaptive immune response by measuring levels of IFN-regulated gene transcripts and the activation state of tumor-infiltrating lymphocytes and myeloid cells, including NK cells and macrophages. Innate and/or adaptive immune response and IFN signalling activation will also be assessed in peripheral blood by immunoprofiling, gene expression analysis, and measurement of cytokine and/or chemokine secretion. Enrollment is planned to open in October 2019. Disclosures Assouline: Pfizer: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria. Mehta:Seattle Genetics: Research Funding, Speakers Bureau; Astex: Research Funding; TG Therapeutics: Research Funding; Incyte: Research Funding; Spectrum: Consultancy, Speakers Bureau; Imbrium therapeutics: Consultancy; Roche-Genentech: Research Funding; miRagen: Research Funding; Kyowa-Kirin: Consultancy, Speakers Bureau; Astra-Zeneca: Speakers Bureau; Sanofi: Consultancy; Affimed: Research Funding; Forty Seven Inc: Research Funding; Juno/Celgene: Research Funding; Kite/Gilead: Research Funding, Speakers Bureau; Takeda: Research Funding; Rhizen: Research Funding; ADC therapeutics: Research Funding; Pharmacyclics: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. Caimi:Fate Therapeutics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; ADC Therapeutics: Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Speakers Bureau; Kite Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Wang:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Patel:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Kim:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Huszar:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment, Other: Shareholder. Berger:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Friedlander:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Gomez-Pinillos:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Proscurshim:Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. OffLabel Disclosure: TAK-981 is a first-in-class, small molecule inhibitor of SUMOylation, a reversible post-translational modification that regulates protein function by covalent attachment of small ubiquitin-like modifier (SUMO) proteins to a protein substrate.

Description: Background Pevonedistat is the first small-molecule inhibitor of neural precursor cell expressed, developmentally downregulated protein 8 (NEDD8)-activating enzyme (NAE). Inhibiting NAE blocks ubiquitination of select proteins upstream of the proteasome. Treatment with pevonedistat disrupts cell cycle progression and cell survival, leading to cell death in cancers, including myeloid malignancies. In a phase 1b study in patients aged ≥60 yrs with untreated AML, pevonedistat in combination with azacitidine (AZA) was tolerable and showed clinical activity (Swords et al. Blood 2018). In a randomized phase 2 study of pevonedistat + AZA vs AZA alone in patients with higher-risk myelodysplastic syndromes/chronic myelomonocytic leukemia and low-blast AML, pevonedistat + AZA improved event-free survival (EFS) and overall survival (OS), had a similar safety profile to AZA alone, did not increase myelosuppression, and maintained AZA dose intensity (Adès et al. ASCO 2020). Venetoclax (VEN) is a small-molecule inhibitor of B-cell lymphoma 2 that is approved in the United States in combination with low-dose cytarabine or hypomethylating agents for the treatment of patients with AML. VEN + AZA has been shown to improve OS vs AZA alone, and the combination is emerging as a standard of care for older patients with newly diagnosed AML who are unfit for standard intensive chemotherapy. Despite recent advances, outcomes for these patients remain poor; novel therapies that increase duration of response (DOR) or reduce relapse rates are needed. Pevonedistat in combination with VEN has shown synergistic cytotoxic effects in AML cell lines and primary clinical AML samples (Knorr et al. Cell Death Differ 2015). This is likely mediated through pevonedistat-induced neutralization of prosurvival proteins including myeloid leukemia cell differentiation protein (MCL-1). Upregulation of MCL-1 is thought to be a primary mode of resistance to VEN. Therefore, treatment with pevonedistat + VEN may help to prevent or overcome resistance to VEN and prolong DOR. The reported clinical benefit of both pevonedistat + AZA and VEN + AZA in AML, and preclinical evidence of synergy between pevonedistat and VEN, suggest that combination treatment with all 3 therapies may result in improved outcomes compared with VEN + AZA in patients with newly diagnosed AML who are unfit for intensive chemotherapy. A phase 1/2 study of the triplet combination of pevonedistat, VEN, and AZA in secondary AML established the recommended phase 2 dose and demonstrated a high response rate in this relatively refractory population (Short et al. EHA 2020). Methods NCT04266795 is a randomized, open-label, controlled, phase 2 study (Figure) that is being conducted across ~85 sites globally. Eligible patients are those aged ≥18 yrs with morphologically confirmed newly diagnosed AML (World Health Organization criteria 2008) and considered unfit for treatment with cytarabine and anthracycline induction due to age and/or comorbidities. Patients are being randomized 1:1 to receive the combination of pevonedistat 20 mg/m2 intravenously (IV) on days 1, 3, and 5, VEN 400 mg by mouth on days 1-28 in cycle 1 (ramp up schedule of 100 mg on day 1, 200 mg on day 2, 400 mg on days 3-28) and then on days 1-28 (days 1-21 if remission is confirmed; can return to 28-day dosing if well tolerated) in cycle 2 onwards, and AZA 75 mg/m2 (IV or subcutaneously) on days 1-7 or 1-5, 8, and 9, or VEN + AZA, in 28-day cycles until unacceptable toxicity, relapse, or progressive disease. Randomization is stratified by age (18-