Fostamatinib for the Treatment of Lower-risk Myelodysplastic Syndromes or Chronic Myelomonocytic Leukemia Who Have Failed Therapy With Hypomethylating Agents

PRIMARY OBJECTIVE: I. To assess the safety and tolerability of different doses of fostamatinib in patients with myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) as the measure of adverse events (AEs), serious AEs (SAEs), and laboratory abnormalities on fostamatinib treatment and frequency of discontinuation or interruptions of fostamatinib due to fostamatinib related AEs. SECONDARY OBJECTIVES: I. To assess overall survival (OS), duration of response, relapse-free survival (RFS). II. To assess overall response (OR) rate to different dose schedules of fostamatinib in patients with MDS and CMML following International Working Group (IWG) 2006 response criteria. III. Hematological response at the end of 2 cycles for each dose level. IV. Frequency of dose escalation of fostamatinib to a dose greater than 100 mg twice daily (BID). V. Frequency of platelet transfusion independence. VI. Frequency of red blood cell (RBC) transfusion independence for \> 8 weeks. VII. Endpoints related to correlative studies. OUTLINE: This is a dose-escalation study. Patients receive fostamatinib orally (PO) BID on days 1-28. Treatment repeats every 28 days for up to 6 cycles (week 24) in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 30 days, then every 6 months thereafter.