Karyopharm to Present Selinexor Data in Patients with Myelofibrosis and Multiple Myeloma at the 68th American Society of Hematology Annual Meeting and Exposition (ASH)

– Week 48 Data from the Phase 3 SENTRY Trial Selected for Oral Presentation –

– Data from the Phase 2 SENTRY-2 Trial Selected for Oral Presentation –

NEWTON, Mass., Nov. 4, 2026 /PRNewswire/ -- Karyopharm Therapeutics Inc. (Nasdaq: KPTI) ("Karyopharm" or the "Company"), a commercial-stage pharmaceutical company pioneering novel cancer therapies, today announced that abstracts from two of its clinical trials evaluating selinexor in patients with myelofibrosis were selected for oral presentations at ASH 2026. In addition, an abstract from a clinical trial evaluating selinexor in combination with other backbone therapies in multiple myeloma was selected for a poster presentation.

"New data from SENTRY continues to highlight the promising clinical activity achieved with the combination of selinexor plus ruxolitinib in patients with myelofibrosis, with ongoing benefit observed through week 48," said Reshma Rangwala, M.D., Ph.D., Chief Medical Officer and Head of Research of Karyopharm. "I am also encouraged by early data from the Phase 2 SENTRY-2 trial where selinexor is being evaluated as a monotherapy, with an optional add-on of a JAK inhibitor. Data from the 60 mg cohort of SENTRY-2 support monotherapy selinexor activity in JAKi-naïve myelofibrosis."

• Title: Updated results from the Phase 3 SENTRY trial investigating selinexor plus ruxolitinib in JAK inhibitor–naïve myelofibrosis

• Publication Number: 526

• Session Title: 634. Myeloproliferative Syndromes: Clinical and Epidemiological: Combining Forces Against Myelofibrosis

• Presentation Time: December 13, 2026 from 10:15 a.m. CT to 10:30 a.m. CT

• Title: Phase 2 study evaluating selinexor monotherapy in patients with JAKi-naïve myelofibrosis

• Publication Number: 244

• Session Title: 634. Myeloproliferative Syndromes: Clinical and Epidemiological: Emerging Therapies and Approaches in MPN

• Presentation Time: December 12, 2026 from 2:45 p.m. CT to 3:00 p.m. CT

• Title: Selinexor, mezigdomide, and dexamethasone (SMd) in patients with relapsed/refractory multiple myeloma (RRMM) who relapsed or are ineligible for T-cell–redirecting therapy: updated results from STOMP Arm 12

• Publication Number: 2242

• Session Title: 654. Multiple Myeloma: Pharmacologic Therapies: Poster I

• Presentation Time: December 12, 2026 from 5:30 p.m. CT to 7:30 p.m. CT

SENTRY (XPORT-MF-034; NCT04562389) is a Phase 3 clinical trial evaluating a once-weekly dose of 60 mg of selinexor in combination with ruxolitinib compared to placebo plus ruxolitinib in JAKi-naïve myelofibrosis patients with platelet counts >100 x 109/L (N=353). Patients were randomized 2-to-1 to the selinexor arm. The co-primary endpoints for this trial are spleen volume reduction ≥ 35% (SVR35) at week 24 and the average change in absolute total symptom score (Abs-TSS) over 24 weeks relative to baseline. The results from the Phase 3 SENTRY trial were presented at the 2026 American Society of Clinical Oncology Annual Meeting and were simultaneously published in the peer-reviewed Journal of Clinical Oncology. In addition, the results were presented at the 2026 European Hematology Association Congress, where the presentation was recognized as one of the six best abstracts at the meeting.

SENTRY-2 (XPORT-MF-044; NCT05980806) is a multicenter, open-label, Phase 2 study evaluating the efficacy of selinexor monotherapy (cohort 1: 60 mg once-weekly; n=29 per arm) in patients with JAKi-naïve myelofibrosis and thrombocytopenia (platelet count ≥50x109/L). Optional ruxolitinib, pacritinib, or momelotinib treatment (based on platelet count) could be added for patients whose SVR from baseline is <10% at Week 12 or <35% at Week 24. The primary endpoint is spleen volume reduction ≥35% (SVR35) at Week 24. Key secondary endpoints are safety and absolute total symptom score (Abs-TSS) at Week 24. Exploratory endpoints include changes in variant allele frequency (VAF) and bone marrow fibrosis.

Myelofibrosis is a rare blood cancer that affects approximately 20,000 patients in the United States and 19,000 patients in the European Union1. The disease causes bone marrow fibrosis (scarring in the bone marrow), which makes it difficult for the bone marrow to make healthy blood cells, splenomegaly (enlarged spleen), progressive anemia which often leads to symptoms like fatigue and weakness, and other disease associated symptoms including abdominal discomfort, pain under the left ribs, early satiety, night sweats and bone pain. The only approved class of therapies to treat myelofibrosis are JAK inhibitors, including ruxolitinib.

1. Clarivate/DRG (2023)

Selinexor and Backbone Treatments of Multiple Myeloma Patients (STOMP; NCT02343042) Arm 12 is evaluating the all-oral combination of selinexor, mezigdomide, and dexamethasone (SMd) in adults with triple-class exposed relapsed/refractory multiple myeloma with ≥2 prior lines of therapy and who had progressed after or were deemed ineligible for T-cell-redirecting therapy (TCRT). Phase 1 had 3 cohorts with the selinexor dose escalated from 40 mg once weekly to 60 mg on days 1, 8, and 15 of a 28-day cycle; mezigdomide is administered at 0.6 or 1.0 mg daily on days 1–21, and dexamethasone 40 mg is administered weekly. Responses are assessed by investigator using International Myeloma Working Group criteria, and safety is assessed per Common Terminology Criteria for Adverse Events (CTCAE) V5.0. Phase 1 objectives are to determine maximum tolerated dose and recommended Phase 2 dose (RP2D) of SMd; Phase 2 primary objectives are to determine objective response rate (ORR) and further characterize safety as per CTCAE V5.0 at the RP2D.

XPOVIO is a first-in-class, oral exportin 1 (XPO1) inhibitor compound for the treatment of cancer. XPOVIO functions by selectively binding to and inhibiting the nuclear export protein XPO1. XPOVIO is approved and marketed by Karyopharm in the U.S. in multiple oncology indications, including: (i) in combination with VELCADE® (bortezomib) and dexamethasone (XVd) in adult patients with multiple myeloma after at least one prior therapy; and (ii) in combination with dexamethasone in adult patients with heavily pre-treated multiple myeloma. XPOVIO® (also known as NEXPOVIO® in certain countries) has received regulatory approvals in various indications in a growing number of ex-U.S. territories and countries, including but not limited to the European Union, the United Kingdom, Mainland China, Taiwan, Hong Kong, Australia, South Korea, Singapore, Israel, and Canada. XPOVIO®/NEXPOVIO® is marketed in these respective ex-U.S. territories by Karyopharm's partners: Antengene, Menarini, Neopharm, and FORUS. Selinexor is also being investigated in several other mid- and late-stage clinical trials across multiple high-unmet need cancer indications.

For more information about Karyopharm's products or clinical trials, please contact the Medical Information department at: Tel: +1 (888) 209-9326; Email: medicalinformation@karyopharm.com

XPOVIO® (selinexor) is a prescription medicine approved:

• In combination with bortezomib and dexamethasone for the treatment of adult patients with multiple myeloma who have received at least one prior therapy (XVd).

• In combination with dexamethasone for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti‐CD38 monoclonal antibody (Xd).

Thrombocytopenia: Monitor platelet counts throughout treatment. Manage with dose interruption and/or reduction and supportive care.

Neutropenia: Monitor neutrophil counts throughout treatment. Manage with dose interruption and/or reduction and granulocyte colony‐stimulating factors.

Gastrointestinal Toxicity: Nausea, vomiting, diarrhea, anorexia, and weight loss may occur. Provide antiemetic prophylaxis. Manage with dose interruption and/or reduction, antiemetics, and supportive care.

Hyponatremia: Monitor serum sodium levels throughout treatment. Correct for concurrent hyperglycemia and high serum paraprotein levels. Manage with dose interruption, reduction, or discontinuation, and supportive care.

Serious Infection: Monitor for infection and treat promptly.

Neurological Toxicity: Advise patients to refrain from driving and engaging in hazardous occupations or activities until neurological toxicity resolves. Optimize hydration status and concomitant medications to avoid dizziness or mental status changes.

Embryo‐Fetal Toxicity: Can cause fetal harm. Advise females of reproductive potential and males with a female partner of reproductive potential, of the potential risk to a fetus and use of effective contraception.

Cataract: Cataracts may develop or progress. Treatment of cataracts usually requires surgical removal of the cataract.

• The most common adverse reactions (≥20%) in patients with multiple myeloma who receive XVd are fatigue, nausea, decreased appetite, diarrhea, peripheral neuropathy, upper respiratory tract infection, decreased weight, cataract and vomiting. Grade 3‐4 laboratory abnormalities (≥10%) are thrombocytopenia, lymphopenia, hypophosphatemia, anemia, hyponatremia, and neutropenia. In the BOSTON trial, fatal adverse reactions occurred in 6% of patients within 30 days of last treatment. Serious adverse reactions occurred in 52% of patients. Treatment discontinuation rate due to adverse reactions was 19%.

• The most common adverse reactions (≥20%) in patients with multiple myeloma who receive Xd are thrombocytopenia, fatigue, nausea, anemia, decreased appetite, decreased weight, diarrhea, vomiting, hyponatremia, neutropenia, leukopenia, constipation, dyspnea, and upper respiratory tract infection. In the STORM trial, fatal adverse reactions occurred in 9% of patients. Serious adverse reactions occurred in 58% of patients. Treatment discontinuation rate due to adverse reactions was 27%.

Lactation: Advise not to breastfeed.

For additional product information, including full prescribing information, please visit www.XPOVIO.com.

To report SUSPECTED ADVERSE REACTIONS, contact Karyopharm Therapeutics Inc. at 1‐888‐209‐9326 or FDA at 1‐800‐FDA‐1088 or www.fda.gov/medwatch.

Karyopharm Therapeutics is a commercial-stage pharmaceutical company pioneering the science of nuclear export inhibition to develop differentiated therapies for patients with cancer. The Company's lead therapy, XPOVIO® (selinexor), is a first-in-class inhibitor of exportin 1 (XPO1). XPOVIO is marketed by the Company in the U.S. for adults with relapsed or refractory multiple myeloma and is approved as XPOVIO or NEXPOVIO® in more than 50 ex-U.S. countries and territories. Building on its leadership in XPO1 biology, Karyopharm is advancing selinexor's potential in hematologic cancers, including in myelofibrosis. The Company is also exploring opportunities to evaluate XPO1 inhibition across myeloproliferative neoplasms using next-generation compounds, including eltanexor. Headquartered in Newton, Massachusetts, Karyopharm has an established, efficient and scalable commercialization infrastructure to bring novel therapeutic options to patients with cancer. For more information, visit www.karyopharm.com and follow Karyopharm on LinkedIn and on X at @Karyopharm.

The Company's securityholders are cautioned that trading in the Company's securities during the pendency of the Company's voluntary petitions under Chapter 11 (the "Cases") is highly speculative and poses substantial risks. Trading prices for the Company's securities may bear little or no relationship to the actual recovery, if any, by the Company's securityholders in the Cases. The Chapter 11 plan provides that holders of the Company's common stock and preferred stock will not receive any payment or other distribution on account of such securities. Accordingly, the Company urges extreme caution with respect to existing and future investments in its securities. In particular, the Company expects that its existing equity securities will have no value and that holders of such securities will experience a complete loss on their investment.

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward-looking statements include those regarding Karyopharm's expectations with respect to whether long-term overall survival data from the SENTRY trial will verify clinical benefit; expectations with respect to commercialization efforts; and the ability of selinexor and eltanexor to treat patients with multiple myeloma, myelofibrosis, and other diseases. Such statements are subject to numerous important factors, risks and uncertainties, many of which are beyond Karyopharm's control, that may cause actual events or results to differ materially from Karyopharm's current expectations. For example, there can be no guarantee that Karyopharm will successfully commercialize XPOVIO or that any of Karyopharm's drug candidates, including selinexor, will successfully complete necessary clinical development phases or that development of any of Karyopharm's drug candidates will continue. Management's expectations and, therefore, any forward-looking statements in this press release could also be affected by risks and uncertainties relating to a number of other factors, including the following: the effects of Cases on the Company and on the interests of various constituents, including holders of the Company's common stock; risks related to the consummation of the transactions contemplated by the Restructuring Support Agreement with Ayrmid Ltd.; the Company's ability to maintain relationships with suppliers, vendors, collaboration and license partners, employees and other third parties and regulatory authorities as a result of the Cases; the length of time that the Company will operate under Chapter 11 protection and the continued availability of operating capital during the pendency of the Cases; the expected delisting of the Company's common stock from the Nasdaq Global Select Market; the outcome of the Cases generally; the adoption of XPOVIO in the commercial marketplace, the timing and costs involved in commercializing XPOVIO or any of Karyopharm's drug candidates that receive regulatory approval; the ability to obtain and retain regulatory approval of XPOVIO or any of Karyopharm's drug candidates that receive regulatory approval; Karyopharm's results of clinical trials and preclinical trials, including subsequent analysis of existing data and new data received from ongoing and future trials; the content and timing of decisions made by the U.S. Food and Drug Administration and other regulatory authorities, investigational review boards at clinical trial sites and publication review bodies, including with respect to the need for additional clinical trials; the ability of Karyopharm or its third party collaborators or successors in interest to fully perform their respective obligations under the applicable agreement and the potential future financial implications of such agreement; Karyopharm's ability to enroll patients in its clinical trials; unplanned cash requirements and expenditures; development or regulatory approval of drug candidates by Karyopharm's competitors for products or product candidates in which Karyopharm is currently commercializing or developing; Karyopharm's ability to obtain, maintain and enforce patent and other intellectual property protection for any of its products or product candidates; and any other risks or uncertainties, including those described in the section entitled "Risk Factors" in the Company's most recent annual or quarterly report filed with the Securities and Exchange Commission ("SEC") and in other filings the Company makes with the SEC from time to time. Any forward-looking statements contained in this press release speak only as of the date hereof, and, except as required by law, Karyopharm expressly disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.