DIPG-16. ACUTE VERSUS PROLONGED CONVECTION-ENHANCED DELIVERY OF ALISERTIB INTO H3 K27M-MUTANT MODELS OF DIFFUSE MIDLINE GLIOMA

Convection-enhanced delivery (CED) is a potentially promising strategy to administer therapeutics directly into the brainstem of children harboring H3 K27-altered diffuse midline glioma (DMG). While early-phase clinical trials have demonstrated the safety of this technique, efficacy has yet to be achieved. Here, we describe how different variations of CED may be exploited to extend survival in a DMG murine patient-derived orthotopic xenograft model. Either 1-day (8 µL/hr) or 7-day (1 µL/hr) continuous CED infusions were performed to deliver an equivalent volume of the aurora kinase inhibitor alisertib to the mouse brainstem. Bioluminescence and magnetic resonance images were acquired to monitor tumor progression, validate CED catheter positioning, and analyze infusion-related imaging changes. Both infusion regimens significantly prolonged survival versus control (median survival benefit of 6.5 and 8 days, p=0.03 and p=0.01, for 1-day and 7-day CED, respectively). Postmortem examination of brains revealed no signs of tissue necrosis, cavitary lesions, or cellular (inflammatory) infiltrate at the site of infusion. However, the tumor parenchyma surrounding the cannula tract was markedly hypocellular in treated animals. Alisertib induced a robust increase in H3 K27 trimethylation along with decreased H3 K27M and Ki-67. Our findings indicate that CED of alisertib is well tolerated and effective, in both the acute and prolonged setting, underscoring the potential of this approach in the management of DMG.