1151 Sonodynamic Therapy (SDT) Using Intravenous 5-aminolevulinic Acid With MR-Guided Focused Ultrasound (MRgFUS) for the Treatment of Diffuse Intrinsic Pontine Gliomas in Pediatrics: Initial Safety and Outcomes of the Multicenter SDT-201 Trial

INTRODUCTION: Diffuse intrinsic pontine glioma (DIPG) is the leading cause of mortality amongst pediatric neuro-oncologic diseases. Sonodynamic therapy with MR-guided focused ultrasound (MRgFUS) is being investigated in multiple clinical trials. METHODS: Twelve patients with DIPG were treated from August 2022-April 2024 as part of a dose-escalation protocol with SDT in a multicenter Phase 1/2 clinical trial (NCT05123534). MRgFUS was combined with the prodrug SONALA-001 (5-ALA iv) to activate its metabolite, protoporphyrin IX, and thereby induce apoptosis within tumor cells. Treatment is delivered every 4 weeks for up to 12 treatments. RESULTS: Patient ages ranged from 3-23 years and 60% were male. Twelve patients underwent a total of 45 SDT treatments (range: 2-9). When enrolled, median tumor volume was 1,337 cm3 (range: 310-2078 cm3) and duration since diagnosis was 5 months. SONALA-001 doses tested were 5 mg/kg and 10 mg/kg. Delivered ultrasonic acoustic energy ranged from 190-444 joules/cm3. After 6 months of median follow-up (range: 2-18), 2 partial responses occurred, and 9 of 12 patients had stable or improved baseline symptoms (Lansky Status), including improved mobility and diplopia. One adverse clinical event included a small non-operative epidural hematoma secondary to a stereotactic frame pin. There have been no grade 3 or worse treatment-related adverse events or dose-limiting toxicities. Ten patients are alive a median of 11 months after diagnosis; 2 have deceased; 4 have discontinued treatment. Maximum percent tumor volume changes throughout treatment ranged from a -68% reduction to over 100% enlargement. CONCLUSIONS: Preliminary analysis of twelve pediatric patients treated with SDT for DIPG demonstrates acceptable safety outcomes and promising clinical results. Additional patient enrollment and longer follow-up times are required to determine efficacy.