Karyopharm Therapeutics' shares plunged 69% in after-hours trading Thursday after its drug selinexor failed a late-stage endometrial cancer trial. The study tested selinexor as maintenance treatment against placebo in patients with advanced or recurrent endometrial cancer but did not show statistically significant delay in disease progression. One patient subgroup showed a trend toward longer progression-free survival—roughly 13 months versus 7.5 months on placebo—but this fell short of required thresholds. The company will reduce spending on its endometrial cancer programme whilst completing data review. Chief Executive Richard Paulson said the company remains focused on its myelofibrosis programme. Karyopharm plans to submit a US FDA application in August seeking accelerated approval for selinexor combined with ruxolitinib for myelofibrosis treatment.

Menarini Group reports data from the Phase 3 SENTRY trial of selinexor plus ruxolitinib in myelofibrosis at The European Hematology Association (EHA) 2026 Congress. * The combination of selinexor plus ruxolitinib met the first co-primary endpoint demonstrating a statistically significant improvement of spleen volume reduction (SVR35) of 49.8% for the combination arm vs 28% for the control arm at week 24. * Post-hoc analysis from the phase 3 SENTRY trial suggests SVR35 may predict overall survival (OS); new data from the phase 1 SENTRY trial demonstrates a similar finding. * Data selected by EHA's Scientific Program Committee for late-breaking oral presentation. * Data stems from the pivotal study conducted in collaboration with Karyopharm Therapeutics, Inc. FLORENCE, Italy and NEW YORK, June 14, 2026 - The Menarini Group ("Menarini"), a leading international pharmaceutical and diagnostics company, and Stemline Therapeutics, Inc. ("Stemline"), a wholly-owned subsidiary of the Menarini Group focused on bringing transformational oncology treatments to cancer patients, announced that new data related to the pivotal Phase 3 SENTRY trial will be presented as a late-breaking oral[1] at The European Hematology Association (EHA) 2026 Congress. SENTRY (NCT04562389), a pivotal Phase 3 trial, is a randomized, double-blind, placebo-controlled trial of 60 mg selinexor in combination with ruxolitinib in frontline myelofibrosis (MF) (n=353), versus ruxolitinib monotherapy. Conducted by Karyopharm Therapeutics, Inc., in collaboration with the Menarini Group, SENTRY was designed to evaluate two co-primary endpoints: spleen volume reduction of 35% or more (SVR35) and absolute total symptom score (Abs-TSS). The trial met the first co-primary endpoint, demonstrating that patients who were treated with the combination of selinexor plus ruxolitinib achieved a clear and statistically significant improvement in SVR35, compared to patients who received ruxolitinib alone. These results highlight that the combination arm enabled rapid, deep and sustained spleen volume reductions. | / | selinexor plus ruxolitinib (n=235) | placebo + ruxolitinib (n=118) | | SVR35 at week 12 | 49.4% (n=116) | 20.3% (n=24) | | SVR35 at week 24 | 49.8% (n=117) | 28.0% (n=33) | | SVR35 at week 36* | 46.9% (n=97) | 23.0% (n=23) | *Analysis conducted in those patients who completed a spleen assessment or discontinued the study prior to week 36 "Achievement of spleen reduction is the essential goal of myelofibrosis treatment. Importantly, the spleen reduction results seen in SENTRY were rapid, deep and durable, and associated with potential overall survival benefit for the patients receiving the combination," said Dr. Claire Harrison, Professor of Myeloproliferative Neoplasms and Deputy Chief Medical Officer at Guy's and St. Thomas' NHS Foundation Trust. "We are encouraged that these results represent a potential new therapeutic advance for our patients who are in dire need of better options." Other key highlights include: * Absolute Total Symptom Score (Abs-TSS): The combination arm demonstrated a comparable benefit to ruxolitinib alone, with a 9.9 point improvement in Abs-TSS at week 24, in patients who received the combination, compared to a 10.9 point improvement in patients who received ruxolitinib alone. The difference across the two arms was not statistically significant, and the combination arm did not meet this second co-primary endpoint. * Overall Survival (OS): While these data were immature at the time of analysis, a promising early OS signal, a pre-specified secondary endpoint, was observed with the selinexor combination compared to ruxolitinib alone. The study showed a greater than 50% reduction in the risk of death for patients receiving the selinexor combination (HR 0.43). * Spleen Volume Reduction: Consistent SVR35 benefit was observed across prespecified subgroups. Notably, at week 24, superior spleen volume reduction was achieved by the selinexor combination, regardless of the ruxolitinib dose, including by patients receiving less than 15 mg of ruxolitinib per day. * Variant Allele Frequency (VAF) Reduction: This pre-specified exploratory endpoint, which is associated with SVR35, was observed in 32% of patients in the selinexor plus ruxolitinib arm at week 24 versus 23.9% of patients treated with ruxolitinib alone, indicating the combination's potential for disease modification. * Safety and Tolerability: The combination demonstrated a manageable safety and tolerability profile consistent with the known profile of selinexor and ruxolitinib individually. No new safety signals were observed. "The strength of the spleen response and the encouraging early overall survival data observed in the SENTRY study creates hope for a potential new treatment option for patients suffering from this devastating disease with dismal outcomes," said Elcin Barker Ergun, CEO of the Menarini Group. "Our dedication and commitment to bring transformational treatments to patients facing cancer is stronger than ever." About Myelofibrosis (MF) Myelofibrosis (MF) is a type of blood cancer that belongs to a group of diseases called Myeloproliferative Neoplasms (MPNs). These diseases are caused by the overgrowth of abnormal blood-forming cells in the bone marrow, which leads to the formation of scar tissue. This scarring makes it difficult for the body to produce healthy blood cells. The incidence of MF is rare, with only about one or two people diagnosed each year for every 100,000 individuals, and the median survival after diagnosis is six years. Additionally, for people living with MF, their quality of life can be compromised by symptoms including fatigue, an enlarged spleen, and low blood counts, all of which are caused by the disease. 1,[2],[3] To report SUSPECTED ADVERSE REACTIONS, contact Stemline Therapeutics, Inc. at [email protected]. All of the relevant information can be found at https://stemline.com/contact/ Please see Summary of Product Characteristics (SmPC) and European Public Assessment Report at www.ec.europa.eu. Please refer to local prescribing information where selinexor is approved for full information. Menarini Group holds licensing rights for selinexor and currently markets it in numerous European countries and global territories. In the U.S., Karyopharm Therapeutics markets selinexor and the full prescribing information is available here. About The Menarini Group The Menarini Group is a leading international pharmaceutical and diagnostics company, with a turnover of $5.5 billion and over 17,000 employees. Menarini is focused on therapeutic areas with high unmet needs with products for cardiology, oncology, pneumology, gastroenterology, infectious diseases, diabetology, inflammation, and analgesia. With 18 production sites and 9 Research and Development centers, Menarini's products are available in 140 countries worldwide. For further information, please visit www.menarini.com. About Stemline Therapeutics Inc. Stemline Therapeutics, Inc. ("Stemline"), a wholly-owned subsidiary of the Menarini Group, is a commercial-stage biopharmaceutical company focused on bringing transformational oncology treatments to patients. Stemline commercializes elacestrant, an oral endocrine therapy indicated for the treatment of postmenopausal women or adult men with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative, ESR1-mutated advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy, in the U.S., Europe, and other global regions. Stemline also commercializes tagraxofusp-erzs, a novel targeted therapy directed to CD123, for patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive hematologic cancer, in the United States, Europe, and other global regions. In addition, Stemline commercializes selinexor, an XPO1 inhibitor for multiple myeloma, in Europe. The company is also conducting multiple label-expansion studies with elacestrant and tagraxofusp in breast and hematologic cancer indications, respectively, and has an extensive clinical pipeline of additional drug candidates in various stages of development for a host of solid and hematologic cancers. Media Contacts The Menarini Group Valeria Speroni Cardi Email: [email protected] [1] The safety and efficacy of the investigational combinations and unapproved indications discussed in this press release have not been established by the FDA, EMA, or any other regulatory authority.

Karyopharm's XPO1 plus JAK inhibitor regimen both hits and misses in Phase III myelofibrosis trial. June 3, 2026 Newton, Massachusetts-based Karyopharm Therapeutics (Nasdaq: KPTI) reported that selinexor (Xpovio) combined with ruxolitinib nearly doubled the spleen volume response rate versus ruxolitinib alone in JAK inhibitor-naïve myelofibrosis, with Phase III data simultaneously published in the Journal of Clinical Oncology at ASCO 2026. The trial achieved onme of its co-primary endpoints in relation to spleen volume reduction, but fell short in the second co-primary endpoint average change in total symptom score. The SENTRY trial (NCT04562389) is a randomized, placebo-controlled Phase III study enrolling 353 JAKi-naïve myelofibrosis patients with platelet counts above 100 x 10[9]/L, randomized 2:1 to selinexor 60 mg once weekly plus ruxolitinib or placebo plus ruxolitinib. On the co-primary endpoint of spleen volume reduction >= 35% (SVR35) at week 24, 49.8% of patients in the combination arm responded versus 28.0% in the control arm (odds ratio 2.58; 95% CI 1.60-4.17; p \< 0.05). The second co-primary endpoint - average change in absolute total symptom score over 24 weeks - did not reach statistical significance; the adjusted mean difference was 0.97 points (95% CI −1.07 to 3.02; p\=0.825), with similar symptom improvement observed across both arms. A pre-specified secondary analysis of overall survival showed a hazard ratio of 0.43 (95% CI 0.19-1.00; nominal one-sided p\=0.022), with Kaplan-Meier curve separation emerging around month 9 and 95.3% of combination-arm patients alive at the February 2026 data cut versus 89.8% in the control arm. Grade 3+ treatment-emergent adverse events occurred in 70% of the combination arm versus 50% of controls, driven primarily by hematologic toxicity; thrombocytopenia (59% vs 43%) and nausea (57% vs 17%) were the most differentiated all-grade events. Selinexor inhibits exportin 1 (XPO1), a nuclear export protein, retaining tumor suppressor proteins in the nucleus - a mechanism distinct from JAK inhibition and theoretically complementary to ruxolitinib's pathway. The myelofibrosis combination landscape also includes Syndax's axatilimab and Bristol Myers Squibb's Reblozyl (luspatercept) in related settings, though cross-trial comparisons are limited by differing populations and endpoints. The trial's mixed outcome leaves Karyopharm in an unusual position. While the combination delivered one of the strongest spleen response improvements seen in a randomized frontline MF study, the failure to improve symptom burden could complicate regulatory discussions. The emerging survival signal may ultimately prove more important than either co-primary endpoint if it strengthens with longer follow-up, although the current analysis remains immature. This article was generated with AI assistance and reviewed and edited by the AllSci editorial team Explore more at AllSci News: https://allsci.com/news/