Core Viewpoint - Plus Therapeutics has initiated the ReSPECT-LM dose optimization trial for REYOBIQ™ to determine the optimal dosing schedule for treating leptomeningeal metastases, building on previous trial results and supported by a $17.6 million grant from CPRIT [1][7]. Trial Design and Objectives - The trial aims to optimize treatment dosing for maximum efficacy and safety, focusing on the safety and tolerability of multiple REYOBIQ doses administered via intraventricular catheter [2]. - Primary objectives include identifying the maximum tolerated dose and minimum effective dose for patients with LM from any primary solid tumor cancer [2]. Enrollment and Study Details - The trial will enroll up to 24 patients, evaluating REYOBIQ at a recommended Phase 2 dose of 44.1 mCi across three dosing intervals [4]. - Key cohorts include dosing intervals of 56 days, 28 days, and 14 days, with up to six patients per cohort [4]. Efficacy and Safety Data - Previous trials showed a clinical benefit rate of 76%, with 29% of patients achieving partial responses and 47% maintaining stable disease [5]. - No dose-limiting toxicities were observed in the first four cohorts, although one Grade 4 DLT occurred in each of Cohorts 5 and 6 [5]. Future Plans - The company plans to present data from the completed single-dose escalation trial at the SNO/ASCO CNS Metastases Conference in August 2025 and will request an End of Phase 1 Type B meeting with the FDA [6]. About Leptomeningeal Metastases - Leptomeningeal metastases occur in approximately 5% of patients with metastatic cancer, with median survival typically ranging from 2 to 6 months, highlighting the urgent need for effective treatment options [8]. About REYOBIQ™ - REYOBIQ™ is a novel injectable radiotherapy designed for targeted high-dose radiation in CNS tumors, with potential advantages over currently approved therapies [9]. Company Overview - Plus Therapeutics is a clinical-stage pharmaceutical company focused on developing targeted radiotherapeutics for challenging CNS cancers, with a pipeline that includes treatments for leptomeningeal metastases, recurrent glioblastoma, and pediatric brain cancer [10].

Core Insights - Plus Therapeutics has received FDA clearance for its Investigational New Drug application for REYOBIQ, aimed at treating pediatric patients with high-grade glioma and ependymoma [2][5] - The Phase 1/2a trial, named ReSPECT-PBC, is supported by a $3 million grant from the U.S. Department of Defense and will focus on determining the maximum tolerated dose and safety of REYOBIQ in children aged 6 to 21 [1][4][7] Company Overview - Plus Therapeutics is a clinical-stage pharmaceutical company based in Houston, Texas, specializing in targeted radiotherapeutics for central nervous system cancers [9] - The company is advancing a pipeline that includes treatments for recurrent glioblastoma, leptomeningeal metastases, and pediatric brain cancer [9] Trial Design and Objectives - The ReSPECT-PBC trial is a two-part, single-arm study designed to assess the safety and tolerability of REYOBIQ, with a focus on pediatric patients with rare and aggressive brain tumors [4][7] - The trial will enroll approximately 56 patients, with 24 in Phase 1a for dose escalation and 32 in Phase 2a to assess efficacy [7] Treatment Potential - REYOBIQ is designed to deliver high doses of beta radiation directly to brain tumors while minimizing damage to surrounding healthy tissue, potentially improving outcomes for patients with limited treatment options [5][8] - The targeted delivery method via convection enhanced delivery (CED) aims to bypass the blood-brain barrier, which is a significant challenge in treating CNS tumors [4][5]