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

"SyB C-1101（rigosertib sodium） will be administered to two cohorts at either 280 mg/day or 560 mg/day.~The dose will be administered orally twice daily for 14 consecutive days, followed by 7-day observation period. The treatment period of 21 days (14 days of administration + 7 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. However, treatment will be limited to a maximum of 6 cycles including the first cycle."