A trend favoring the selinexor arm was observed in the modified intent to treat (mITT) population (n=236), with a median PFS of 12.75 months in the selinexor arm compared to 7.43 months in the placebo arm (hazard ratio=0.76 [95% CI: 0.51, 1.12]; one-sided p-value=0.0791). The safety and tolerability profile of selinexor was consistent with its established safety profile, with no new safety signals observed. Karyopharm intends to complete a full evaluation of the data from the XPORT-EC-042 trial and plans to present the data at a future medical meeting. The results of the XPORT-EC-042 trial do not affect ongoing trials of selinexor in other potential indications.

"These results are meaningful for a patient population lacking effective maintenance therapies that can delay disease progression," said Professor Ignace Vergote, MD, gynecologic oncologist at the Catholic University Leuven in Belgium, European Network for Gynaecological Oncological Trial groups (ENGOT) and global lead principal investigator. "The trend for a longer progression-free survival observed in the mITT population of the selinexor arm continues to highlight the potential of XPO1 inhibition in patients with TP53 wild-type/pMMR endometrial cancer."

"Delaying the progression of cancer by five months at the median is a meaningful and encouraging outcome," said Dr. Robert Coleman, M.D., FACOG, FACS, of Texas Oncology and the Gynecologic Oncology Group (GOG) and lead principal investigator in the United States. "Although I am disappointed that the PFS improvement was not statistically significant, I look forward to continuing to follow these results over time and presenting the data from this important trial at an upcoming medical meeting. This patient population who have TP53 wild-type/pMMR advanced or recurrent endometrial cancer remains in need of new treatment options."

"While disappointed by these unexpected results, we believe they advance the scientific understanding of XPO1 inhibition for tens of thousands of endometrial cancer patients worldwide. We are deeply committed to further investigating these data," said Reshma Rangwala, MD, PhD, Chief Medical Officer and Head of Research at Karyopharm. "I would like to thank all of the patients, their families and the clinical trial investigators and their staff, as well as ENGOT and GOG, for participating in this trial."

"While the results we are announcing today fell short of our expectations, they do not diminish our confidence in the broader potential of selinexor and benefit of XPO1 inhibition," said Richard Paulson, President and Chief Executive Officer of Karyopharm. "We remain focused on maximizing our opportunity in myelofibrosis and continuing to build on our profitable multiple myeloma business. Looking ahead, we expect several important milestones in our myelofibrosis program over the next year, including the submission of our sNDA, the potential addition of selinexor to relevant compendia guidelines and topline data from the 60 mg cohort of the Phase 2 SENTRY-2 trial, each anticipated in the second half of 2026."