HGG-51. Intranasal Delivery of Pdgfra-Immunoliposomal Sn-38 for the Treatment of Pediatric High-Grade Gliomas

Abstract INTRODUCTION pHGGs are the most common cause of cancer-related death in children, of which the most malignant and devastating tumors include diffuse midline glioma (DMG). Its anatomical location in the braistem, infiltrative nature, and blood-brain barrier (BBB) limit surgical resection and the distribution of systemically administered drugs. Intranasal delivery (IND) is a noninvasive method that bypasses the BBB, by leveraging the unique anatomic connections of the olfactory and trigeminal nerve pathways with the nasal cavity. We previously demonstrated the efficacy of IND of liposomal (LS) formulation of the active metabolite of the DNA topoisomerase I inhibitor, irinotecan, LS-SN-38, in orthotopic human brainstem xenograft models. The specificity of liposomes can be enhanced by using immunoliposome (iLS) formulation, which are coated with antibodies specific to the tumor cells leading to targeted drug delivery and reduced toxicity to normal cells. Platelet-derived growth factor receptor alpha (PDGFRA) plays a role in DMG oncogenesis and is expressed in as much as 70% of DMG by immunohistochemistry. In this study, we evaluated the specificity of anti-PDGFRA monoclonal antibody conjugated immunoliposome (PDGFRA-iLS) in pHGG cell lines. METHODS PDGFRA signals were assessed in pHGG cells using western blotting. Cells with high and low expression of PDGFRA were treated with rhodamine (Rho) labeled PDGFRA-iLS and imaged with fluorescent microscope. RESULTS DIPG007, SF7761 and KNS42 expressed high levels of PDGFRA, while SF8628 and DIPG36 cells showed low expression. Fluorescence microscopy revealed high PDGFRA-rhodamine (Rho)-iLS expression in DIPG007 cells (PDGFRA high), relative to SF8628 and DIPG36 cells (PDGFRA low). CONCLUSION PDGFRA-Rho-iLS shows increase cellular uptake in DIPG cells. Work is underway to determine the biodistribution, host toxicity, and anti-tumor activity of IND of PDGFRA-iLS-SN- 38 alone and in combination with radiation therapy in pHGG xenograft models.