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Introduction - Selinexor is a first-in-class Selective Inhibitor of Nuclear Export (SINE) compound that binds and inactivates Exportin 1 (XPO1). Selinexor with low dose dexamethasone (dex) has demonstrated potent anti-cancer activity in patients with heavily pretreated MM. While the development of proteasome inhibitors (PIs) has transformed the treatment of MM, acquired resistance to PIs limit their efficacy. Preclinical studies have shown that selinexor, when combined with bortezomib, can restore sensitivity of bortezomib-resistant MM to this drug, inducing tumor growth inhibition and increasing survival in MM models in mice. In this clinical trial (NCT02343042), we investigated the safety, tolerability and efficacy of the combination of selinexor, bortezomib and low dose dex (SdB) in patients (pts) with refractory MM. Methods - This phase 1b/2 dose escalation study using a standard 3+3 design, was designed to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) for SdB. The study included pts with refractory MM, after ≥ 1 prior therapy. Pts with prior PI relapsed and/or refractory disease were included, provided the patient's MM was not refractory to bortezomib as last therapy. Selinexor was independently dosed escalated in once-weekly (QW, starting at 80 mg; N=7, 100 mg N=6 pts) or twice-weekly (BIW, starting at 60 mg; N=3, 80 mg N=6 pts) regimens. Bortezomib (1.3 mg/m2 sc) was administered either once-weekly or twice-weekly and dex was given orally 40 mg QW or 20 mg BIW. Results - As of July 25th, 2016, enrollment in the dose escalation cohorts has been completed with 22 pts (12 male /10 female). The median age is 65 years (range, 46 - 74), with a median of 4 (range, 1 - 12) prior treatment regimens. One dose limiting toxicity (Grade 4 thrombocytopenia without bleeding) in the 80 mg BIW cohort was observed but the MTD has not been reached. Common related grade 1/2 adverse events (AEs) include: fatigue 41%, nausea 41%, anorexia 36%, and weight loss 18%. Grade 3/4 AEs include: thrombocytopenia 41%, anemia 18%, and neutropenia 18%. One case of grade 1 peripheral neuropathy in the 80 mg BIW cohort was reported. All pts were evaluable for response. The ORR (≥partial response, PR) was 77% with ≥VGPR 27% (1 pt in CR and 5 pts in VGPR) and 11 PRs. There were 3 minor responses (14%), 1 stable disease, 1 progressive disease (5% each). Seven of the 12 pts with PI-refractory MM responded (ORR 58%). A summary of response by PI treatment history is shown in Table 1. Ten patients have remained on study >4 months, including 7 patients still on trial (longest >9 months). Based on tolerability and anti-MM activity, RP2D of SdB is selinexor 100 mg, bortezomib 1.3 mg/m2 and dex 40 mg, all given once weekly. At the RP2D, all six pts achieved ≥PR (ORR 100%). Conclusions - Selinexor in combination with bortezomib and dex is well tolerated and highly active in refractory MM. Toxicities are manageable and similar to selinexor or bortezomib monotherapy. Peripheral neuropathy is uncommon, consistent with the use of weekly bortezomib sc and the lack of neuropathy with selinexor. Overall, the SdB regimens induced an ORR of 77% with ≥VGPR of 27%. In patients with PI-refractory MM, the ORR was 58%, indicating that the addition of selinexor restores sensitivity to bortezomib. These results confirm the preclinical data supporting synergistic effects of selinexor when combined with PIs. This promising, once-weekly treatment regimen may provide deeper and more durable responses in pts with relapsed / refractory MM, including those with PI-refractory disease. Table 1. Best Response by Prior Proteasome Inhibitor (PI) Treatment Status Table 1. Best Response by Prior Proteasome Inhibitor (PI) Treatment Status Disclosures Bahlis: Onyx: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Other: Travel Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Other: Travel Expenses, Research Funding, Speakers Bureau; BMS: Honoraria. Sebag:Janssen: Honoraria; Novartis: Honoraria; Celgene: Honoraria. Sutherland:Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria. White:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Venner:Amgen: Honoraria; J+J: Research Funding; Takeda: Honoraria; Janssen: Honoraria; Celgene: Honoraria, Research Funding. Kouroukis:Amgen: Research Funding; Janssen: Research Funding; Karyopharm: Research Funding. McCurdy:Celgene: Honoraria. Lalancette:BMS: Honoraria; Celgene: Honoraria. Bensinger:Sanofi: Consultancy, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Acetylon: Research Funding; Takeda: Honoraria, Research Funding; Bayer: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Amgen: Consultancy, Honoraria, Research Funding. Lentzsch:BMS: Consultancy; Celgene: Consultancy, Honoraria. 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. Jeha:Karyopharm: Employment. Picklesimer:Karyopharm: Employment. Saint-Martin:Karyopharm: Employment. Choe-Juliak:Karyopharm Therapeutics: Employment. Chen:Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Takeda: Research Funding.

Introduction - The nuclear export protein exportin 1, (XPO1) is overexpressed in a wide variety of cancers including multiple myeloma (MM). Selinexor is a first-in-class Selective Inhibitor of Nuclear Export (SINE) compound that binds and inactivates XPO1. Selinexor forces nuclear retention and reactivation of tumor suppressor proteins (TSPs; NF-kB, p53 and FOXO) and reduction of many proto-oncogenes, including MDM2, MYC and Cyclin D. In murine MM models, the combination of selinexor with IMIDs shows synergistic anti-MM activity with good tolerability. Methods - This phase 1b/2 dose escalation study (NCT02343042) using the standard 3+3 design, is designed to determine the tolerability, maximum tolerated dose (MTD), recommended phase 2 dose (RP2D) and preliminary efficacy of selinexor in combination with pomalidomide and dexamethasone (SdP). Patients (pts) with relapsed/refractory MM who received ≥ 2 prior therapies including lenalidomide and a proteasome inhibitor (PI) were enrolled. Selinexor is dose escalated once-weekly (QW, starting at 80 mg) or twice-weekly (BIW, starting at 60 mg), pomalidomide 4 mg PO daily, days 1 -21 and dexamethasone (dex) 40 mg PO weekly in a 28 day cycle. Results - As of 25-Jul-2016, 11 pts (7 male / 4 female) have been enrolled. The median age is 58 years (range, 43 - 76), with a median of 5 (range, 2 - 9) prior treatment regimens. Eight pts had MM refractory to lenalidomide and 7 pts to bortezomib; including 5 pts with MM refractory to both. For the once-weekly selinexor cohort, the 80 mg dose level has been cleared and the 100 mg dose level is on going. For the twice-weekly cohort, the 60 mg dose level has been cleared and 80 mg dose level is on going. Common related grade 1/2 adverse events (AEs) include: nausea 7pts (64%), altered taste 5pts (45%), anorexia 3pts (27%), and diarrhea 3pts (27%). Grade 3/4 AEs include: neutropenia 8pts (73%), thrombocytopenia 4pts (36%), and leukopenia 3pts (27%). There was no febrile neutropenia or bleeding reported to date. No dose limiting toxicities have been observed and MTD has not been reached. Ten pts were evaluable for response including, 1 complete response (CR), 5 partial responses (PR), 3 minor responses (MR), and 1 stable disease (SD). The overall response rate (ORR) is 60% with a clinical benefit rate of 90% (ORR + MR). Responses are rapid in onset, with at least MR achieved by cycle 2 day 1. In lenalidomide and bortezomib refractory patients the ORR was 50%. One pt was deemed not evaluable due to non-compliance with study procedures. Eight pts are still on study, (range <1 - 7+ months) including 4 pts maintaining their response for > 3 months. Conclusions - The all oral combination of selinexor, pomalidomide and low dose dex (SdP) has significant clinical activity (ORR 60%) in pts with heavily pretreated MM. Responses are rapid in onset even with the lower dose cohorts tested thus far, CR can be achieved. No additive toxicities over monotherapy of either pomalidomide or selinexor have been observed. This novel treatment regimen therefore holds promise in addressing the urgent need to induce meaningful and durable responses in patients with IMiD and PI relapsed/refractory MM. Disclosures Chen: Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Takeda: Research Funding. Sebag:Celgene: Honoraria; Janssen: Honoraria; Novartis: Honoraria. Sutherland:Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. White:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Venner:Takeda: Honoraria; Celgene: Honoraria, Research Funding; J+J: Research Funding; Janssen: Honoraria; Amgen: Honoraria. Kouroukis:Karyopharm: Research Funding; Amgen: Research Funding; Janssen: Research Funding. McCurdy:Celgene: Honoraria. Lalancette:BMS: Honoraria; Celgene: Honoraria. Bensinger:Sanofi: Consultancy, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Acetylon: Research Funding; Bayer: Research Funding; Takeda: Honoraria, Research Funding. Lentzsch:Celgene: Consultancy, Honoraria; BMS: 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. Jeha:Karyopharm: Employment. Picklesimer:Karyopharm: Employment. Saint-Martin:Karyopharm: Employment. Choe-Juliak:Karyopharm Therapeutics: Employment. Bahlis:BMS: Honoraria; Janssen: Consultancy, Honoraria, Other: Travel Expenses, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Other: Travel Expenses, Research Funding, Speakers Bureau; Onyx: Consultancy, Honoraria; Amgen: Consultancy, Honoraria.

Multiple myeloma (MM) is a hematological cancer associated with significant symptomatic burden. Bone disease, renal insufficiency, cytopenias, infection, and peripheral neuropathy, among other disease manifestations and complications, impair patients' quality of life. The Canadian Myeloma Research Group Consensus Guideline Consortium, formerly Myeloma Canada Research Network Consensus Guideline Consortium, proposes national consensus recommendations for the management of MM-related manifestations and complications. To address the needs of Canadian physicians and people living with MM across the country, this document focuses on the improvement and maintenance of patient care by clarifying best-practice approaches for the prevention, detection and management of disease manifestations and complications. The Canadian Myeloma Research Group Consensus Guideline Consortium will periodically review the recommendations herein and update as necessary.

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