Phase III study of Estybon fails to meet primary endpoint in higher-risk myelodysplastic syndromes.- Onconova Therapeutics

Onconova Therapeutics announced that INSPIRE, the company’s pivotal Phase III study assessing the efficacy and safety of Estybon (IV rigosertib) in higher-risk myelodysplastic syndromes (HR-MDS) patients, did not meet its primary endpoint of improved survival. The primary endpoint of the trial was overall survival, comparing IV rigosertib plus best supportive care to physician's choice (PC) plus best supportive care in patients who had progressed on, failed to respond to, or relapsed after previous treatment with a hypomethylating agent (HMA) within nine cycles over the course of one year after initiation of HMA treatment. A pre-specified analysis in the very high risk (VHR-MDS) patient subgroup was also conducted. Results of INSPIRE demonstrated that in the intent-to-treat analysis patients randomized to IV rigosertib achieved overall survival of 6.4 months, versus 6.3 months for PC (p=0.33) in the overall HR-MDS population. Overall survival in the pre-specified VHR-MDS subgroup of patients was also not significantly different between the two study arms. There was an increase in overall survival in the PC arm post-interim analysis that was unexpected. The Company is conducting additional analyses. Safety analysis indicates that IV rigosertib was generally well tolerated, with reported adverse events similar to those observed in previous clinical studies with IV rigosertib in MDS. Serious adverse events (SAEs) were uncommon, with a similar profile of SAEs in both study arms.