Patients with myelofibrosis, a rare blood cancer marked by bone marrow scarring and an enlarged spleen, may soon have a new treatment option that combines two distinct drug classes for the first time. Karyopharm Therapeutics announced it will submit a supplemental new drug application to the U.S. Food and Drug Administration in August 2026, seeking accelerated approval for selinexor in combination with ruxolitinib for frontline treatment of the disease.
The decision follows constructive discussions with the FDA, which agreed that a 35% or greater reduction in spleen volume, known as SVR35, appears to be a reasonably likely surrogate endpoint for predicting overall survival. That agreement opens the door for accelerated approval based on data from the Phase 3 SENTRY trial, which compared the two-drug combination against ruxolitinib plus placebo in 353 patients who had not previously received JAK inhibitor therapy.
Trial results, presented at the 2026 American Society of Clinical Oncology annual meeting and published in the Journal of Clinical Oncology, showed statistically significant improvements in spleen response at week 24. The responses were described as rapid, deep, and sustained across broad patient subgroups, with a promising preliminary overall survival signal and reductions in variant allele frequency, a marker of disease burden. The combination also demonstrated a tolerable safety profile, according to the company.
If approved, this would mark the first combination therapy for myelofibrosis, adding a novel mechanism of action to the current standard of care. Selinexor is an oral exportin 1 (XPO1) inhibitor, a class of drugs that blocks a protein involved in shuttling tumor suppressor proteins out of cancer cells. Ruxolitinib is a JAK inhibitor, the only approved drug class for myelofibrosis to date. The two work through complementary pathways, which researchers believe explains the enhanced effect seen in the trial.
Myelofibrosis affects roughly 20,000 people in the United States and 17,000 in the European Union. Symptoms include fatigue, abdominal pain, night sweats, bone pain, and an enlarged spleen, and many patients eventually require blood transfusions. The disease remains difficult to treat, and progression to acute leukemia is a serious risk.
The company plans to request priority review at the time of submission, which, if granted, could lead to an FDA decision within about six months of filing. To verify the clinical benefit seen in the SENTRY trial, Karyopharm will use long-term overall survival data from the ongoing study, where overall survival is a pre-specified secondary endpoint. The trial remains blinded, and no patient crossover is permitted, which strengthens the integrity of the survival analysis.
For patients and clinicians, the prospect of a new frontline option is significant. The current treatment landscape has remained largely unchanged for years, and the combination approach offers hope for deeper and more durable responses. With the submission planned for August 2026, a decision could come as early as 2027, potentially ushering in a new era for myelofibrosis care.