On June 5, 2017 Onconova Therapeutics, Inc. (NASDAQ:ONTX), a Phase 3 stage biopharmaceutical company focused on discovering and developing novel small molecule drug candidates to treat cancer, with a primary focus on Myelodysplastic Syndromes (MDS), reported the results of a Phase 2 study with rigosertib as a treatment for higher risk (HR-MDS) after failure of hypomethylating agents (HMAs) (Press release, Onconova, JUN 5, 2017, View Source [SID1234519406]). The study sought to evaluate bone marrow blast (BMBL) response to rigosertib as a surrogate for overall survival (OS) in this patient population. The results showed treatment with rigosertib resulted in a reduction in BMBL count, including complete bone marrow responses, confirming findings in earlier studies. Thus, BMBL response to rigosertib is a potential surrogate marker for improvement in overall survival in this patient population.

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"In this new study for HR-MDS patients after failure of HMA therapy, we are excited to confirm a correlation between blast reduction and prolongation of survival in rigosertib treated patients. These results build upon our previous findings in the ONTIME trial showing improvement in overall survival in patients with the highest risk prognostic categories after failure of HMA treatment (ASH 2014 presentation),"said Ramesh Kumar, Ph.D., President and CEO of Onconova.

Rigosertib is currently being tested in a randomized, global, Phase 3 INSPIRE trial for this patient population.

Study Name: Relationship of Bone Marrow Blast response to Overall Survival in a Multicenter Study of Rigosertib in Patients with Myelodysplastic Syndromes with Excess Blasts Progressing on or After Treatment with a Hypomethylating Agent

Summary of Data from the 04-24 Trial

Patient Demographics:

64 patients treated, with a median age of 73, median prior HMA duration of 10.8 months.
Eligible patients had 5%-30% BMBL confirmed within six weeks pre-study and disease. progression as per International Working Group (IWG) 2006 criteria, Cheson et al., Blood 2006) on or after HMAs within two years.
Safety/Tolerability:

Intravenous rigosertib has been well tolerated to date.
More than 1,100 patients have been treated with rigosertib.
Adverse events in study 04-24 were similar to those observed in the preceding Phase 3 ONTIME Study
Objectives:

Primary Efficacy: Evaluate the relationship between BMBL response and OS in MDS patients with excess blasts (5-30%) progressing on or after treatment with azacitidine or decitabine who are administered 72-hr continuous intravenous (IV) infusions of 1800 mg/24 hour rigosertib every 2 weeks for 8 cycles and every 4 weeks thereafter. BMBL response is defined according to the International Working Group (IWG) 2006 criteria; or stable BM response (no progression),
Secondary Efficacy: Evaluate the following parameters: Overall response (CR, partial response/remission [PR], BMCR, and stable disease [SD]) according to 2006 IWG criteria; Population pharmacokinetics.
Safety: safety and tolerability of rigosertib administered as 72-hour continuous IV (5%-30% BMBL) progressing on or after treatment with azacitidine or decitabine.
Trial Design:

Phase 2 open-label, multi-center multi-national study (approximately 30-40 Centers in the US and Europe) of the efficacy and safety of Rigosertib administered as 72-hour continuous intravenous infusions in patients with myelodysplastic syndromes with excess blasts progressing on or after treatment with azacitidine or decitabine.
Treatment will continue until IWG 2006 progression criteria are met (ie, 50% increase of BMBL or worsening of cytopenias) or until death from any cause, whichever comes first.
Following these results, all patients will be followed until death and/or progression, even if they have discontinued treatment for any reason. View the complete study poster HERE.