Plus Therapeutics Partners With Genomic Testing Cooperative To Integrate GTC's Next-Generation Sequencing Technology Into The CNSide Cerebrospinal Fluid Assay Platform

The collaboration is expected to enable comprehensive DNA and RNA profiling across hundreds of clinically relevant biomarkers from a single CSF specimen, extending CNSide from guideline-recognized CTC enumeration into the guideline-recognized DNA and tumor-derived DNA analytic layer within one integrated platform. The collaboration advances Plus’ three-pillar CNS oncology strategy: targeted radiotherapeutics led by REYOBIQ™ (rhenium Re186 obisbemeda); precision diagnostics anchored by the CNSide CSF platform; and AI-enabled data analytics through the Company’s strategic partnership with Ephemeral Technologies.

Leptomeningeal metastases (LM) occur in an estimated 5% to 10% of patients with metastatic solid tumors, representing a U.S. addressable population of more than 100,000 patients per year. The CNSide CSF Tumor Cell Enumeration test received dedicated AMA PLA code 0640U, effective July 1, 2026, and the CNSide CLIA laboratory is enrolled with Medicare. Commercial payer agreements covered approximately 126 million U.S. lives as of the Company’s most recent quarterly update. A recently presented health-economic analysis associated CNSide-enabled earlier diagnosis and management of LM with an approximately 40% reduction in overall LM-related healthcare costs.

Strategic Rationale

• NCCN alignment. The updated NCCN CNS Cancers Guidelines (Version 2.2026) recognize CSF CTCs alongside tumor-derived DNA and broaden LM terminology from "CSF cytology" to "CSF analysis." CNSide already delivers guideline-recognized CTC enumeration; the GTC collaboration adds the guideline-recognized DNA and RNA layer within one CLIA-accredited testing platform
• Foundational data layer. Hundreds of DNA and RNA biomarkers per CSF specimen, combined with CNSide tumor cell and biomarker quantification, create a uniquely deep longitudinal molecular data set, materially enhancing the inputs to Plus’ AI platform with Ephemeral Technologies
• Expanded market and clinical utility. Positions CNSide as a comprehensive CSF-based precision oncology platform across LM and other metastatic CNS cancers, supporting broader adoption, higher per-test value, and potentially deeper biopharma engagement
• Reimbursement leverage. Builds on PLA code 0640U and Medicare enrollment, with future billing pathways for the expanded menu pursued under applicable payer requirements
• Operating leverage. Uses GTC’s sequencing and informatics as a technical service input to the CNSide CLIA laboratory, accelerating menu expansion while managing capital