Clinical Data Results from the Phase 3 Portion of the Phase2/3 SEAL Study

The median PFS in the XPOVIO arm of the Phase 3 portion of the SEAL study was 2.83 months compared to 2.07 months in the placebo arm (hazard ratio (HR)=0.70; p=0.023). These data indicate that treatment with XPOVIO reduced the risk of disease progression or death by approximately 30%, compared to placebo. The estimated 6-month PFS survival probability was 23.9% on the selinexor arm compared to 13.9% on placebo. Additionally, the 12-month PFS survival probability was 8.4% on the selinexor arm compared to 2% on the placebo arm. Finally, 7.5% of patients on the selinexor arm had a 15% or greater reduction in their disease burden as measured by target lesion size while none of the patients on the placebo arm achieved this level of reduction. The trial allowed patients on placebo with objective progression to cross over to the XPOVIO treatment arm. The median overall survival for patients who received XPOVIO was 9.99 months compared to 9.07 months for patients who never crossed over to the XPOVIO treatment arm (HR=0.69; p=0.122).
The most common treatment-related adverse events (AEs) were cytopenias, along with gastrointestinal and constitutional symptoms and were consistent with those previously reported from other selinexor studies. Most AEs were manageable with dose modifications and/or standard supportive care. The most common non-hematologic treatment-related AEs were nausea (81%), decreased appetite (60%), fatigue (51%), and vomiting (49%) and were mostly Grade 1 and 2 events. The most common Grade 3 and 4 treatment-related AEs were anemia (19%), hyponatremia (11%), thrombocytopenia (10%) and asthenia (10%).