KPT-9274 spares normal hematopoietic cells from toxicity, suggesting selective toxicity. (A) Annexin V/propidium iodide (PI) analysis of 5 normal donor peripheral blood mononuclear cells (PMBCs) treated with KPT-9274 after 72 hours. (B) Treatment with 250 nM of KPT-9274 revealed no significant decrease in colony formation of normal donor CD34⁺ stem cells (n = 4). (C) Whole-blood samples from normal donors (n = 5) were treated with or without 1 µM of KPT-9274 and accessed for viability of normal lymphocytes after 48 hours of treatment using flow cytometric analysis.