Onconova Presents Promising Data from Phase 2 Expansion Study of Oral Rigosertib and Azacitidine Combination in Patients with Myelodysplastic Syndromes at 6th International Bone Marrow Failure Disease Symposium
- First presentation from dose exploration cohorts in an expanded trial addressing urinary safety of the novel combination therapy in higher risk patients with Myelodysplastic Syndromes (MDS)
- Study demonstrates elimination of grade 3 or grade 4 urinary adverse events after implementation of mitigation strategies
Oral rigosertib has been developed as a single agent and in combination with azacitidine. Previous studies have demonstrated that Low-Risk (LR) MDS patients with intermittent oral rigosertib treatment at a dose of 560 mg BID show a transfusion independence rate (TI), as defined by the IWG 2006 criteria, of 44% (Raza, et al, Blood 2017 130:1689). Oral rigosertib in combination with AZA is being studied in patients with Higher-risk (HR) MDS. Initial results of the Phase 2 study with oral rigosertib (840 mg /day 3 out of 4 weeks) in combination with azacitidine in patients with MDS demonstrated an overall response rate of 76%; 62% in patients following hypomethylating agent (HMA) failure; and 85% in HMA naïve patients (Navada et al, EHA, 2017). In both single agent and combination studies, oral rigosertib has been associated with hematuria in a subset of patients which has been shown to be dose and administration scheme dependent (Garcia-Manero G, Blood 2016 128:2011). The results reported here are from a dose exploration study in HR MDS patients with an increased oral rigosertib dose (1120 mg/day 3 out of 4 weeks) and focus on the impact of risk-mitigation strategies in minimizing the incidence of urinary adverse events (UAEs); including hematuria. The mitigation strategies included prescribing the second dose of rigosertib earlier in the day and encouraging bladder emptying at bedtime.
The reported incidence of hematuria of any grade with single agent azacitidine is 6.3%, including 2.3% grade 3 and 4 events (per product insert). In the combination trial of oral rigosertib (total dose of 840 mg/day 3 out of 4 weeks) and azacitidine, the incidence of hematuria was 48%, with grade 3 or grade4 AEs of 12%. In the new study, in 37 patients studied with oral rigosertib (total dose of 1120 mg/day 3 out of 4 weeks) and azacitidine employing prophylactic risk-mitigating strategies to minimize hematuria, a significantly lower incidence of grade 1 & 2 hematuria (11%), and no grade 3 or 4 hematuria have been seen to date.
Dose optimization and risk mitigation strategies undertaken specifically to minimize UAEs associated with oral rigosertib in combination with azacitidine have resulted, to date, in a decrease in frequency of hematuria from 48% to 11% and elimination of any serious grade 3 events. Minimization of AEs permits patients to continue on treatment to optimize the potential benefit. Reduction in incidence of hematuria also enables the continued study of oral rigosertib in LR-MDS, based on the promising TI Rate previously reported.
A copy of the poster is available by visiting the Scientific Presentations section of Onconova’s website.
About
The intravenous form of rigosertib has been employed in Phase 1, 2, and 3 clinical trials involving more than 800 patients, and is currently being evaluated in a randomized Phase 3 international INSPIRE trial for patients with higher-risk MDS, after failure of hypomethylating agent, or HMA, therapy.
The INternational Study of Phase III IV RigosErtib, or INSPIRE, was finalized following guidance received from the
About Oral Rigosertib
The oral form of rigosertib was developed to provide more convenient dosing for use where the duration of treatment may extend to multiple years. This dosage form may also support many combination therapy modalities. To date, 368 patients have been treated with the oral formulation of rigosertib. Initial studies with single-agent oral rigosertib were conducted in hematological malignancies, lower-risk MDS, and solid tumors. Combination therapy of oral rigosertib with azacitidine and chemoradiotherapy has also been explored. Currently, oral rigosertib is being developed as a combination therapy together with azacitidine for patients with higher-risk MDS who require HMA therapy. A Phase 1/2 trial of the combination therapy has been fully enrolled and the preliminary results were presented in 2016. This novel combination is the subject of an issued US patent with earliest expiration in 2028.
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Source: Onconova Therapeutics, Inc.