In Part I of this trial the bioavailability and tolerability of oral ON1910.Na administered as single, oral, escalating doses in a fasting state (defined as no less than 30 minutes before next meal) will be determined in three patients with Low, Intermediate-1, Intermediate-2 or High Risk MDS. All three patients will receive during the first week a 70mg single oral dose and blood samples for pharmacokinetic analyses will be taken after dosing. In the absence of drug-related grade 2 toxicity or higher, single dosing will be escalated in each patient weekly to 140mg (week 2), 280mg (week 3), 560mg (week 4) and 700mg (week 5).