EPCT-12. PNOC015: PHASE 1 STUDY OF MTX110 (AQUEOUS PANOBINOSTAT) DELIVERED BY CONVECTION ENHANCED DELIVERY (CED) IN CHILDREN WITH NEWLY DIAGNOSED DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG) PREVIOUSLY TREATED WITH RADIATION THERAPY

OBJECTIVE: To determine safety and distribution of MTX110 delivered by CED in newly diagnosed DIPG patients. METHODS: DIPG patients (3–21 years) were enrolled after radiation. CED of MTX110 combined with gadoteridol was completed based on dose levels (DL) (30–90 µM with volumes ranging from 3 cc (single dose) to 2 consecutive doses of 6 cc; total number of DL=7). Catheter position was chosen to maximize tumor coverage. Distribution of infusate was monitored with real-time MR imaging. Repeat CED was performed every 4–8 weeks if tolerated. Quality of life (QOL) assessments using PedsQL Generic Core and Brain Tumor modules were obtained at baseline (n=5), 3-months (n=3), and end of therapy (n=2). Single-cell RNA sequencing and analysis of histone modifications was performed to assess pharmacodynamic effects on DIPG cells. RESULTS: Between May 2018-Dec 2019, 6 patients were enrolled (median age 8 years, range 5–21). Dose limiting toxicities included: grade 3 gait disturbance (DL7; cycle 1); grade 3 muscle weakness/vagus nerve disorder (DL5; cycle 4) and grade 2 intolerable dysphagia (DL7; cycle 4). Twelve CED procedures were completed at DL7 and repeated cycles ranged from 2 to 7. Infusion to distribution volume ratio was approximately 1:3.5. There were no significant changes in self-reported QOL. Parent ratings of patients’ worry (p = 0.04) and overall QOL (p = 0.03) significantly decreased at 3-months. CONCLUSION: Repeat CED of MTX110 at the highest dose is tolerable. Tissue concentrations are likely to be substantially higher compared to oral dosing. Pharmacodynamic effects will be presented.