Oral Rigosertib in Low Risk MDS Patients Refractory to ESAs

This will be a Phase II, single-arm, multicenter study (approximately 15 centers). Approximately 40 transfusion-dependent patients with Low- or Int-1 risk Myelodysplastic Syndrome (MDS) by International Prognostic Scoring System (IPSS) will be enrolled and treated with oral rigosertib administered twice daily for 21 consecutive days of a 21-day cycle (continuous regimen) in order to obtain at least 35 evaluable patients treated for at least 8 weeks. Patients will take 560 mg rigosertib (two 280 mg capsules) in the morning and 280 mg (one 280 mg capsule) in the afternoon, in fasting conditions. All patients on intermittent regimen at the time of Amendment 2 of the Protocol will be switched to the continuous regimen, including patients on reduced doses.