Final Phase I/II Results of Rigosertib (ON 01910.Na) Hematological Effects in Patients with Myelodysplastic Syndrome and Correlation with Overall Survival,

Abstract 3822

Rigosertib is a multi-kinase inhibitor that selectively induces mitotic arrest leading to apoptosis in cancer cells and blasts, while being non-toxic to normal cells. We analyzed bone marrow (BM) response and overall survival (OS) in 60 patients (pts) with myelodysplastic syndrome (MDS), including 51 patients with refractory anemia and excess blasts (RAEB) and 9 patients with refractory cytopenia and multilineage dysplasia (RCMD) enrolled in 4 independent phase 1/2 clinical trials. These pts were treated with rigosertib administered as a continuous intravenous infusion (CIV) from 2 to 6 days weekly or every other week with BM response initially assessed per protocol by week 4 or 8 and every 8 weeks thereafter. Overall survival (OS) analyses were performed by the method of Kaplan-Meier. OS was related (p=0.04) to FAB/WHO classification (see Table 1) in all MDS pts. Eight pts had hematological improvements. OS was also related to IPSS scoring (p=0.02; Table 2) and to BM blastic response (Table 3; p=0.008) in the 51 RAEB-1,-2,-t pts and in a subset of 38 RAEB-1,-2,-t pts refractory or relapsing after treatment with hypomethylating agents (azacitidine/decitabine) (Table 4; p=0.001). A 49-week OS was found in 15 patients in this last group treated with 3-day rigosertib infusions (1800 mg/day) every other week. Rigosertib infusions were well tolerated without evidence of bone marrow myelotoxicity. These results and the predictive value of BM response to rigosertib for estimating OS survival have led to the initiation of a randomized Phase III survival trial of rigosertib 3-day CIV infusions vs best supportive care in RAEB -1, -2 and-t pts who failed or progressed after receiving hypomethylating agents.