Safety and Pharmacokinetics Study of SyB L-1101 in Patients With Recurrent/Relapsed or Refractory Myelodysplastic Syndrome (MDS)

"SyB L-1101（rigosertib sodium） will be administered to two cohorts at either 1200 mg/day or 1800 mg/day.~The dose will be administered intravenously for 72 continuous hours (3 days), followed by 11-day observation period. The treatment period of 14 days (3 days of administration + 11 days of observation) constitutes 1 cycle.~The study will involve treatment through the second cycle, but treatment can be continued for 3 or more cycles if conditions for continued administration are satisfied."