Roughly eighteen months after the SENTRY trial’s 353-patient enrollment closed, Karyopharm is moving toward an August 2026 sNDA submission for selinexor plus ruxolitinib in myelofibrosis, a timeline that carries real weight because the company is leaning on accelerated approval rather than waiting for a mature overall survival readout. That distinction shapes everything: the FDA has told Karyopharm in writing that SVR35, spleen volume reduction of at least 35% at week 24, qualifies as a reasonably likely surrogate endpoint to predict overall survival, which clears the regulatory logic for the accelerated pathway. The clinical bet, then, is that the spleen response data is strong enough to earn approval now while long-term OS from the ongoing blinded follow-up confirms benefit later.
The SENTRY trial was designed with two co-primary endpoints: SVR35 at week 24 and average change in absolute total symptom score over 24 weeks. The statistically significant SVR35 result, presented at ASCO 2026 and simultaneously published in the Journal of Clinical Oncology, anchors the submission. What the sNDA package will also carry is a preliminary overall survival signal observed at topline, reductions in variant allele frequency suggesting genuine disease modification, and the full safety dataset. The trial has no crossover provision and remains blinded during ongoing follow-up, which preserves the integrity of the OS data Karyopharm will eventually need to satisfy the post-approval verification requirement under accelerated approval rules.
The competitive framing Karyopharm uses, that this combination could become the first approved combination therapy for myelofibrosis incorporating a novel drug class, rests on a meaningful mechanistic point. Approved myelofibrosis therapies have so far come from a single drug class: JAK inhibitors. Selinexor inhibits XPO1, a nuclear export protein, making the combination a genuine class addition rather than a dose-optimization story. Whether that distinction survives FDA label negotiations is an open question, but the biological rationale for pairing XPO1 and JAK inhibition is supported by the VAF reductions SENTRY captured, which hint at something beyond symptom control.
Karyopharm is also requesting Priority Review, which, if granted, compresses the FDA’s target action window to roughly six months after receipt, potentially placing a decision in early-to-mid 2027. The single number worth watching from here is the SVR35 response rate in the selinexor arm versus placebo-plus-ruxolitinib: that margin is what the FDA will stress-test when evaluating whether the surrogate endpoint justifies approval ahead of a final OS read.
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.
