A numerical difference of 5.32 months in median progression-free survival was not enough. In the Phase 3 XPORT-EC-042 trial, selinexor delivered a median PFS of 12.75 months against 7.43 months for placebo in 236 patients with TP53 wild-type advanced or recurrent endometrial cancer, yet the trial failed to reach statistical significance on its primary endpoint. That is the uncomfortable reality Karyopharm now faces: a drug that moved the needle clinically but not in the way regulators require.
The design of XPORT-EC-042 (also registered as ENGOT-EN20/GOG-3083) was deliberately narrow. By restricting enrollment to TP53 wild-type tumors, Karyopharm was betting that molecular selection would sharpen the treatment signal for selinexor as a maintenance-only strategy. The logic was coherent. Selinexor, a nuclear export inhibitor that has carried FDA approval since 2019 in relapsed or refractory multiple myeloma, had plausible biological rationale in a solid tumor setting where nuclear export dysregulation plays a documented role. But biomarker enrichment does not guarantee statistical power, and a trial can show the right direction without crossing the threshold that matters.
The endometrial cancer treatment landscape has grown considerably more crowded, with agents like dostarlimab advancing through approvals in combination regimens for first-line advanced disease. Maintenance monotherapy with a small molecule now has to compete against that backdrop, and a subgroup-defined PFS improvement, however directionally interesting, does not anchor a regulatory submission. This failure also arrives alongside a prior Phase 3 miss for selinexor in myelofibrosis, compressing Karyopharm’s near-term path to expanding the drug’s approved footprint.
The one concrete marker worth watching now is overall survival data from XPORT-EC-042. Trials that miss PFS occasionally show a delayed OS signal, particularly when post-progression treatment is unbalanced between arms. If that data matures favorably, it reopens a conversation with regulators. If it does not, the endometrial program ends here and Karyopharm’s oncology story narrows back to hematology.
Source link: https://www.sec.gov/Archives/edgar/data/1503802/000119312526326995/d71318d8k.htm
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
