Plus Therapeutics to Present Positive FORESEE Clinical Trial Summary Demonstrating Utility of CNSide™ Cerebrospinal Fluid Assay in Diagnosis and Clinical Management of Patients with Leptomeningeal Metastases

On November 22, 2024 CNSide Diagnostics, LLC, a wholly owned subsidiary of Plus Therapeutics, Inc. (Nasdaq: PSTV) ("Plus" or the "Company"), reported data from the FORESEE trial showcasing the CNSide CSF Assay Platform’s utility in diagnosing and guiding clinical decision making for breast cancer and non-small cell lung cancer patients with LM (Press release, Plus Therapeutics, NOV 22, 2024, View Source [SID1234648586]). The data will be presented at the 2024 Society for Neuro-Oncology (SNO) Annual Meeting November 21-24 in Houston, Texas.

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"Current gold standard CSF cytology lacks the sensitivity needed to reliably diagnose LM in most clinical situations and lacks utility for disease monitoring," said Marc H. Hedrick, M.D., Plus Therapeutics’ President and Chief Executive Officer. "The FORESEE trial shows that CNSide may be a useful tool in accurately identifying all patients with LM, ruling out patients at risk, and enhancing the disease management and monitoring of LM."

Key highlights:

The FORESEE trial achieved its primary endpoint, demonstrating that CNSide influenced treatment decisions in over 90% of cases evaluated, surpassing the predetermined 20% primary endpoint target
CNSide demonstrated enhanced sensitivity in detecting tumor cells (80%) vs. CSF cytology (29%) in patients with LM
CNSide identified actionable mutations in the CSF, such as HER2 amplification, influencing 24% of therapeutic selection decisions
CNSide exhibited high specificity, with no tumor cells detected in patients without LM
CNSide demonstrated improved Negative Predictive Value in ruling out LM (25%) vs. CSF cytology (10%)
CNSide revealed HER2 positivity in LM tumors in 60% of breast cancer patients with HER2-negative primary tumors, informing physician treatment strategies
The data will be presented on Sunday, November 24, at 10:15 a.m. CST in a session titled, "CSF Tumor Cell (CSF-TC) Detection, Quantification and Biomarker assessment Helps in Clinical Management of Breast Cancer and Non-Small Cell Lung Cancer Patients Having Leptomeningeal Disease (FORESEE Study, NCT-5414123)," by Priya Kumthekar, M.D., Associate Professor of Neurology and Hematology/Oncology, and Director of Brain Metastases Program at Northwestern, University, Chicago, Illinois.

About CNSide Test
The CNSide Cerebrospinal Fluid (CSF) Assay Platform consists of four laboratory developed tests (LDTs) used for diagnosis, treatment selection, and treatment monitoring of patients with Leptomeningeal Metastases (LM) from carcinomas or melanoma. The CNSide platform facilitates tumor cell detection / enumeration and biomarker identification using cellular assays (immunocytochemistry (ICC) and fluorescence in situ hybridization (FISH)) and molecular assays (next generation sequencing (NGS)). The CNSide CSF tumor cell enumeration LDT is currently being used in the ReSPECT-LM trial as an exploratory endpoint, and is anticipated to become commercially available in 2025.

About Leptomeningeal Metastases (LM)

LM is a rare complication of cancer in which the primary cancer spreads to the cerebrospinal fluid (CSF) and leptomeninges surrounding the brain and spinal cord. All malignancies originating from solid tumors, primary brain tumors, or hematological malignancies have this LM complication potential with breast cancer as the most common cancer linked to LM, with 3-5% of breast cancer patients developing LM. Additionally, lung cancer, GI cancers and melanoma can also spread to the CSF and result in LM. LM occurs in approximately 5% of people with cancer and is usually terminal with 1-year and 2-year survival of just 7% and 3%, respectively. The incidence of LM is on the rise, partly because cancer patients are living longer and partly because many standard chemotherapies cannot reach sufficient concentrations in the spinal fluid to kill the tumor cells; yet, there are no FDA-approved therapies specifically for LM patients, who often succumb to this complication within weeks to several months, if untreated.

About FORESEE Clinical Trial

The FORESEE Study is a multi-center, prospective clinical trial enrolled patients with Breast or Non-Small Cell Lung Cancer (NSCLC) who have suspicious or confirmed Leptomeningeal Metastases (LM). Standard of Care methods to diagnose or assess the treatment response of LM (Clinical Evaluation, MRI and Cytology) have limited sensitivity and specificity. This creates challenges for physicians to manage LM or determine the best course of treatment. The goal of the FORESEE Study was to evaluate the performance of CNSide in monitoring the LM’s response to treatment and to assess the impact of CNSide on treatment decisions made by physicians.