Three Dosing Schedules of Oral Rigosertib in MDS Patients

This will be a Phase I, randomized, 3-treatment arm, single-center study in transfusion-dependent Myelodysplastic Syndrome (MDS) patients classified as Low- or Intermediate-1 (Int-1) or Intermediate-2 (Int-2) risk by the International Prognostic Scoring System (IPSS). Initially, 18 patients (6 per treatment arm) will be randomized in a 1:1:1 ratio to 1 of 3 oral rigosertib dosing regimens, each of which is a cycle consisting of 14 consecutive days of dosing followed by 7 days off drug. Treatment with erythropoiesis-stimulating agent (ESA) is prohibited for the first 15 weeks (5 cycles). After 15 weeks of dosing (5 cycles), ESA treatment will be initiated if the patient still needs red blood cell (RBC) transfusions and if the pre-transfusion hemoglobin (Hgb) value is ≤ 9 g/dL, unless the clinical judgment of the Investigator determines ESA administration to a patient with a Hgb level \> 9 g/dL is warranted. All study participants will be allowed, as medically justified, access to RBC and platelet (PLT) transfusions, and to filgrastim. Rigosertib dosing adjustment policies are described. After all 18 patients have completed 3 cycles, a risk/benefit analysis will be completed assessing the distribution of adverse events (AEs) and serious adverse events (SAEs) and the number of transfusions among the 3 treatment arms. This analysis will select 1 of the 3 dosing regimens as having the best risk/benefit profile and an additional 12 to 18 patients will be enrolled at this dosing regimen. Eligibility criteria may be modified by protocol amendments to enroll patients with different characteristics. All patients will be treated for 48 weeks or until 2006 International Working Group (IWG) progression criteria are met, unacceptable toxicity is observed, intercurrent illness or a change in the patient's condition prevents further administration of study drug treatment, or until death from any cause occurs, whichever comes first. Patients who have continued hematologic response at 48 weeks may continue to be treated in the study beyond 48 weeks until 2006 IWG progression criteria are met or until death from any cause, whichever comes first.