Selinexor With Fludarabine and Cytarabine for Treatment of Refractory or Relapsed Leukemia or Myelodysplastic Syndrome

Phase I will characterize the dose-limiting toxicities (DLTs) and determine the maximum tolerated dose (MTD) or recommended phase II dose of selinexor when given in combination with fludarabine and cytarabine. Selinexor will be given twice weekly (on days 1 and 3) and escalated or de-escalated based on tolerability. The rolling-6 design will be used for this study. Only cycle 1 of therapy will be used to evaluate the DLT. Two to six participants can be concurrently enrolled onto a dose level, dependent on 1) the number of participants enrolled at the current dose level, 2) the number of participants who have experienced DLT at the current dose level, and 3) the number of participants entered but with tolerability data pending at the current dose level. Accrual is suspended when a cohort of six has enrolled or when the study endpoints have been met. Once the recommended Phase II dose is determined, additional patients will be enrolled, if necessary, so that at least 6 subjects are treated with the recommended Phase II dose to determine MTD. After the MTD is determined, 12 additional patients will be treated at this dose level for further evaluation of tolerability and response.