XPO1 and cancer: This was the first time XPO1 target occupancy was measured in tumors and a dose-dependent effect of selinexor on complex formation was observed with >90% target saturation at 10 mg/kg selinexor in mice (∼50 mg flat dose in humans), a dose active against xenografts, and consistent with doses of selinexor that show anti-cancer activity in patients with heavily pretreated hematologic and solid tumors (10-15 mg/kg in mice is approximately equivalent to 50-70 mg flat dose in humans)[8, 18, 28].