As the effects of selinexor on the developing human fetus at the recommended therapeutic dose are unknown, women of childbearing potential should be advised to avoid becoming pregnant and men should be advised to not father a child while receiving treatment with selinexor. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. Women that are pregnant or breastfeeding are excluded from the study because the risks to an unborn fetus or potential risks in nursing infants are unknown.