SYST-07. PILOT STUDY UTILIZING THE HDAC INHIBITOR BELINOSTAT WITH CHEMORADIATION FOR NEWLY-DIAGNOSED GLIOBLASTOMA

Abstract

Abstract PURPOSE Glioblastomas (GBMs) are highly aggressive brain tumors with poor prognosis. Belinostat is a histone deacetylase inhibitor with blood–brain barrier permeability, anti-GBM activity, and potential to enhance chemoradiation. This clinical trial sought to determine a tolerable dose of concurrent belinostat and assess the clinical efficacy of combining this drug with standard-of-care therapy. METHODS 13 patients each were enrolled in control and belinostat cohorts. The belinostat cohort was given a belinostat regimen (500-750mg/m2 1x/day x 5 days) every 3 weeks (weeks 0, 3, and 6 of RT). All patients received standard temozolomide and radiation therapy (RT). Patient outcomes included progression-free survival, overall survival (OS), and analysis of recurrence pattern of the recurrent gross tumor volume (rGTV). RESULTS Belinostat at 750 mg/m2 produce dose-limiting toxicities (DLTs) in 2 of 3 patients while belinostat at 500 mg/m2 did not result in DLTs. Median OS was 18.5 months for the belinostat cohort and 15.8 months for the control cohort (p=0.53). The rGTVs in the control cohort occurred in areas that received higher radiation doses than that in the belinostat cohort. For those belinostat patients that experienced out-of-field recurrences, tumors were detectable by spectroscopic MRI (sMRI) before RT. In particular, one belinostat patient had an IDH-mutant GBM that had an extraordinary response to therapy with significant shrinkage of enhancing tumor much greater than expected. CONCLUSION Belinostat given concurrently at 500 mg/m2 is well-tolerated. While median OS was not significantly increased for the belinostat cohort, recurrence analysis suggests better in-field control with belinostat, suggesting a radio-sensitizing effect. This study suggests that belinostat can act as a synergistic therapeutic agent for GBMs that may be further enhanced by sMRI-guided RT and may be particularly effective against IDH mutant tumors. A trial is currently in development using belinostat with sMRI-guided RT for IDH-mutant high-grade gliomas.