Abstract

Abstract Iopofosine I 131, a radioconjugate therapy targeting tumor lipid rafts, is being assessed in CLOVER-2 [NCT05610891]–an ongoing dose-finding study evaluating iopofosine in children, adolescents, and young adults with relapsed, refractory, recurrent high-grade gliomas (HGGs) and ependymoma. Major inclusion criteria include patients aged 10-25 years, previously confirmed HGGs or ependymoma, ≥1 measurable intracranial lesion (≥10 mm in longest diameter), and performance status ≥60. Patients are assigned 1:1 to 2 treatment arms which will be assessed in parallel. Arm 1 has 2 cycles, each composed of 2 doses of 20 mCi/m2 given 14 days apart (± 1 day). Cycle 2 is given 8 weeks (± 4 days) post-initial infusion. Arm 2 patients receive 3 cycles of 10 mCi/m2 per dose. Patients in either arm are eligible for 1 additional cycle at the physician’s discretion. If after the first 10 patients, Arm 1 is not tolerated, dosing is reduced to 15 mCi/m2 per infusion. If after the first 10 patients in Arm 2 are deemed to be ineffective and Arm 1 is deemed to be tolerated, dosing is increased to 15 mCi/m2 per infusion. Final visits occur 57 days following the last cycle initiation, with quarterly follow-ups in year 1 and annually in years 2 and 3. Primary endpoints include safety, tolerability, and progression-free survival (PFS). Secondary endpoints are dosimetry, recommended phase 2 dosing determination, overall survival, antitumor and therapeutic activity, and duration of response and clinical benefit. Safety analysis uses the Wilson score method and nonparametric Wilcoxon signed-rank test. Efficacy analyses use the Response Assessment in Pediatric Neuro-Oncology criteria and the Kaplan-Meier method to detect a median PFS of 5 months compared to a historical control of 2 months. For 90% power by a 1-sided, 1-sample log-rank test: ≥10 evaluable patients must be enrolled (≤90) across ≤15 sites.