Karyopharm Therapeutics Inc. announced dosing of the first patient in the Phase 2 expansion of an ongoing open-label Phase 1/2 study investigating eltanexor, a novel oral, Selective Inhibitor of Nuclear Export (SINE) compound, as a single-agent or in combination with approved and investigational agents in patients with several types of hematologic and solid tumor cancers (KCP-8602-801; NCT02649790). The Phase 2 expansion is designed to evaluate eltanexor monotherapy in patients with hypomethylating agents (HMA) refractory, intermediate or high-risk myelodysplastic syndrome (MDS). The primary endpoint for this Phase 2 expansion is overall response rate (ORR) with the secondary endpoints of determining progression-free and overall survival. Initiation of the Phase 2 expansion follows encouraging results from the Phase 1 portion of the study where single-agent eltanexor showed activity in patients with high-risk, relapsed MDS that was refractory to HMAs. In that study (Sangmin, et al. EHA 2021), eltanexor demonstrated a 53% ORR and a median overall survival of 9.9 months, comparing favorably to historical controls. At the recommended Phase 2 dose of 10 mg, eltanexor monotherapy was well tolerated with low incidence and grade of gastrointestinal events. Exacerbation of cytopenias occurred in 20-40% of patients. Based on these promising signals, the study has been expanded to include an additional 83 patients with the first patient recently dosed.