– New Data will Highlight a Post-Hoc Analysis from Phase 1 Portion of SENTRY Trial that Indicates Achievement of SVR35 with Selinexor plus Ruxolitinib May Predict Overall Survival –

– Selected by EHA's Scientific Program Committee as One of the Top Abstracts to be Presented –

NEWTON, Mass., June 2, 2026 /PRNewswire/ -- Karyopharm Therapeutics Inc. (NASDAQ:KPTI), a commercial-stage pharmaceutical company pioneering novel cancer therapies, today announced that its late-breaking abstract was accepted for an oral presentation at the 2026 European Hematology Association (EHA) Congress, taking place June 11 to 14 in Stockholm, Sweden. The SENTRY presentation was selected by EHA's Scientific Program Committee as one of the six best abstracts to be presented during the Late-Breaking Oral Session on Sunday, June 14th. The oral presentation will feature results from the Phase 3 SENTRY trial, a randomized, double-blind, placebo-controlled trial of 60 mg selinexor in combination with ruxolitinib in myelofibrosis.

This abstract highlights the combination of selinexor plus ruxolitinib's ability to enable rapid, deep and sustained spleen volume reductions; similar symptom improvement; a promising signal of overall survival; more patients achieving ≥20% reductions in variant allele frequency (VAF) as early as week 24; and a manageable safety profile. In addition, new data will highlight a post-hoc analysis of 24 patients from the Phase 1 portion of the SENTRY trial which indicates that achieving a spleen volume reduction of 35% or more (SVR35) may predict overall survival, consistent with a similar analysis from the Phase 3 SENTRY trial.

"The SENTRY results are an important development for patients with myelofibrosis, with the combination of selinexor plus ruxolitinib showing a promising overall survival signal supported by rapid, deep and sustained spleen volume reduction and the potential for disease modification with lower levels of VAF," said Dr. Claire Harrison, Professor of Myeloproliferative Neoplasms at Guy's and St. Thomas' NHS Foundation Trust in the United Kingdom. "JAK inhibitors have transformed the treatment landscape over the past 15 years, but there remains a significant need for novel therapies that can build upon their foundation and target additional biological pathways driving disease progression. XPO1 inhibition represents a differentiated mechanism with the potential to extend the benefits of therapy beyond JAK inhibition alone, including the potential to extend overall survival which remains the ultimate objective for patients living with myelofibrosis."

"The results from the Phase 1 portion of our SENTRY trial being presented at EHA provide further support for the promising overall survival signal we saw in our Phase 3 SENTRY results," said Reshma Rangwala, MD, PhD, Chief Medical Officer and Head of Research of Karyopharm. "Collectively, this new analysis, when combined with our existing landmark analysis, provides evidence that supports our belief that SVR35 can be used to predict overall survival. This is incredibly exciting in light of the rapid, deep and sustained reduction in spleen volume observed with selinexor plus ruxolitinib, with the combination approximately doubling the proportion of patients achieving SVR35 as early as week 12 and sustained through week 36. We believe this is driven by selinexor's differentiated mechanism of action which offers a complementary and potentially synergistic approach to JAK inhibition."

Presentation Details

Title: Selinexor plus ruxolitinib in Janus kinase inhibitor–naïve myelofibrosis: Phase 3 SENTRY trial
Abstract Code: LB5002
Session Title: Late-Breaking Oral Session
Presentation Time: Sunday, June 14, 2026, 9:15 a.m. to 10:45 a.m. Central European Summer Time
Presenter: Dr. Claire Harrison, Professor of Myeloproliferative Neoplasms, Clinical Director at Guy's and St. Thomas' NHS Foundation Trust

A copy of the SENTRY presentation to be presented at EHA will be available on the Company's investor relations website under "Publications and Presentations" on June 14, 2026. The peer-reviewed publication discussing the results from the Phase 3 SENTRY trial was published this morning in the Journal of Clinical Oncology and is available on JCO's website.

About the Phase 3 SENTRY Trial

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.

About Myelofibrosis

Myelofibrosis is a rare blood cancer that affects approximately 20,000 patients in the United States and 17,000 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)

About XPOVIO® (selinexor)

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, including in myelofibrosis and endometrial cancer.

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).

SELECT IMPORTANT SAFETY INFORMATION

Warnings and Precautions

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.

Adverse Reactions

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%.

Use In Specific Populations

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.

About Karyopharm Therapeutics

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 and solid tumor cancers, including in myelofibrosis and TP53 wild-type endometrial cancer. The Company is also exploring opportunities to evaluate XPO1 inhibition across myeloproliferative neoplasms and TP53 wild-type driven solid tumors using next-generation compounds, including eltanexor. Headquartered in Newton, Massachusetts, Karyopharm has an established, efficient and scalable commercial 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.

Forward-Looking Statements

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 beliefs about the market opportunity and annual peak revenue opportunities for selinexor; expectations with respect to commercialization efforts; expectations regarding the timing of reporting topline data, publications or compendia listing related to ongoing clinical trials; the ability of selinexor and eltanexor to treat patients with multiple myeloma, endometrial cancer, myelofibrosis, and other diseases; expectations with respect to the clinical development plans and potential regulatory submissions of selinexor; and the potential inclusion of the combination of selinexor plus ruxolitinib in relevant compendia. 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. Further, there can be no guarantee that any positive developments in the development or commercialization of Karyopharm's drug candidate portfolio will result in stock price appreciation. 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 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; substantial doubt exists regarding Karyopharm's ability to continue as a going concern; development or regulatory approval of drug candidates by Karyopharm's competitors for products or product candidates in which Karyopharm is currently commercializing or developing; and Karyopharm's ability to obtain, maintain and enforce patent and other intellectual property protection for any of its products or product candidates. These and other risks are described under the caption "Risk Factors" in Karyopharm's Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, which was filed with the Securities and Exchange Commission (SEC) on May 14, 2026, and in other filings that Karyopharm may make with the SEC in the future. 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.

XPOVIO^® and NEXPOVIO^® are registered trademarks of Karyopharm Therapeutics Inc.

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SOURCE Karyopharm Therapeutics Inc.

Karyopharm's Phase 3 SENTRY Trial of Selinexor Plus Ruxolitinib in Myelofibrosis Selected for Late-Breaking Oral Presentation at EHA 2026