CTNI-78. A PEDIATRIC AND YOUNG ADULT PHASE I DOSE ESCALATION SAFETY STUDY OF BXQ-350 FOR REFRACTORY SOLID AND CENTRAL NERVOUS SYSTEM TUMORS

BACKGROUND BXQ-350 is a novel agent composed of the multifunctional, lysosomal activator protein Saposin C (SapC) and dioleoyl- phosphatidylserine (DOPS) and has demonstrated antitumor effects in both in vitro and in vivo preclinical models. Many tumors, including high-grade glioma and diffuse intrinsic pontine glioma (DIPG), and cells of tumor vasculature have aberrantly-exposed phosphatidylserine (PS)-rich domains on the cell surface. BXQ-350 is an anti-tumor agent in development from Bexion Pharmaceuticals, Inc. that selectively targets tumor cell PS, particularly those translocated to the outer leaflet of the plasma membrane in tumor cells. BXQ-350 activates and participates in various cellular processes, including apoptosis and necrosis, and may also exhibit novel mechanisms leading to cell death that require further investigation. METHODS Nine refractory solid (2) and central nervous system (7) tumor patients (5F:4M, age 4–23 years of age) were enrolled in a 2-site dose escalation Phase I first-in-pediatric trial (NCT03967093) which completed in 2019. All patients received at least one dose of BXQ-350 which was administered as an intravenous infusion. Dosing began at 1.8 mg/kg and escalated to the highest planned dose level of 3.2mg/kg. RESULTS There were no BXQ-350-related serious adverse events, dose limiting toxicities or withdrawals. The highest planned dose of 3.2 mg/kg was achieved safely but a maximum tolerated dose was not established. One osteosarcoma patient had progressive disease prior to completing cycle one of treatment and was removed from trial. Eight patients (DIPG-3, HGG-1, GBM-1, Pineoblasotoma-1, Ependymoma-1, Osteosarcoma-1) completed at least one cycle, with one DIPG patient completing cycle five. CONCLUSION BXQ-350 was well tolerated with no significant dose-limiting toxicities at the highest planed dose level. A pediatric Phase I trial in newly diagnosed patients is planned for 3rd quarter 2020.