Release Details

Plus’ CNSide leptomeningeal metastases (LM) FORSEE trial met key primary and secondary endpoints

CNSide more than doubled the diagnostic sensitivity vs. gold standard cerebral spinal fluid (CSF) cytology and influenced clinical management decisions in over 90% of LM cases

AUSTIN, Texas, Aug. 13, 2024 (GLOBE NEWSWIRE) -- Plus Therapeutics, Inc. (Nasdaq: PSTV) (“Plus” or the “Company”), a clinical-stage pharmaceutical company developing targeted radiotherapeutics with advanced platform technologies for central nervous system (CNS) cancers, presented data from the FORESEE study of its CNSide platform for the diagnosis and management of LM. The data were presented in a podium presentation at the 2024 Society for NeuroOncology (SNO)/American Society for Clinical Oncology (ASCO) CNS Metastases Conference August 8-10, 2024 in Denver, Colorado.

The study, titled “A Therapy Treatment Response Trial in Patients with Leptomeningeal Metastases (LM) Using CNSide (FORESEE Study, NCT05414123),” was a prospective, multi-center observational trial enrolling 39 patients with Breast (21 patients) or Non-Small Cell Lung Cancer (18 patients) with a suspected or confirmed diagnosis of LM. The primary endpoint of the study assessed how CNSide test results influenced clinical decision making. Secondary endpoints assessed CNSide vs. the gold standard of LM diagnosis, CSF cytology, and its use for personalization of treatment selection based on tumor molecular phenotype. The study was presented by Priya U. Kumthekar, M.D., Associate Professor of Neurology and Medicine at Northwestern University and FORSEE Trial Principal Investigator.

Key results from the FORESEE trial:

• The trial achieved its primary endpoint, demonstrating that CNSide influenced treatment decisions in over 90% of cases, surpassing the 20% primary endpoint target
• CNSide demonstrated enhanced sensitivity in detecting tumor cells (80%) vs. 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

“The FORESEE trial met its key primary and secondary endpoints, objectively showing that CNSide has very high clinical utility for treating physicians,” said Priya U. Kumthekar, M.D., “CNSide is a more sensitive and definitive test for LM and has the potential to permit earlier diagnosis, manage our patients with more diagnostic precision, and hopefully improve therapeutic outcomes for our patients with LM.”

About CNSide Test
CNSide is a laboratory developed test (LDT) based on proprietary quantitative tumor cell capture and detection method, paired with assays to identify actionable molecular treatment targets. Given the genetic changes that can occur as metastatic cancer spreads to the CNS, the evaluation of cerebrospinal fluid with CNSide provides a unique opportunity to identify biomarkers in patients with metastatic carcinoma or melanoma to help guide physicians in therapy selection. In addition, the quantitative tumor cell count assay is designed to be used in a serial fashion to monitor the response to therapy more effectively than other current methods. CNSide is currently being used in the ReSPECT-LM trial to quantify circulating tumor cells (CTCs) as an exploratory endpoint.

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 Rhenium (¹⁸⁶Re) obisbemeda
Rhenium (¹⁸⁶Re) obisbemeda is a novel injectable radiotherapy specifically formulated to deliver direct targeted high dose radiation in CNS tumors in a safe, effective, and convenient manner to optimize patient outcomes. Rhenium (¹⁸⁶Re) obisbemeda has the potential to reduce off target risks and improve outcomes for CNS cancer patients, versus currently approved therapies, with a more targeted and potent radiation dose. Rhenium-186 is an ideal radioisotope for CNS therapeutic applications due to its short half-life, beta energy for destroying cancerous tissue, and gamma energy for real-time imaging. Rhenium (¹⁸⁶Re) obisbemeda is being evaluated for the treatment of recurrent glioblastoma and leptomeningeal metastases in the ReSPECT-GBM and ReSPECT-LM clinical trials. ReSPECT-GBM is supported by an award from the National Cancer Institute (NCI), part of the U.S. National Institutes of Health (NIH), and ReSPECT-LM is funded by a three-year $17.6M grant by the Cancer Prevention & Research Institute of Texas (CPRIT).

About Plus Therapeutics
Plus Therapeutics, Inc. is a clinical-stage pharmaceutical company developing targeted radiotherapeutics for difficult-to-treat cancers of the central nervous system with the potential to enhance clinical outcomes for patients. Combining image-guided local beta radiation and targeted drug delivery approaches, the Company is advancing a pipeline of product candidates with lead programs in recurrent glioblastoma (GBM) and leptomeningeal metastases (LM). The Company has built a supply chain through strategic partnerships that enable the development, manufacturing, and future potential commercialization of its products. Plus Therapeutics is led by an experienced and dedicated leadership team and has operations in key cancer clinical development hubs including Austin and San Antonio, Texas. For more information, visit https://plustherapeutics.com/.

Cautionary Statement Regarding Forward-Looking Statements
This presentation contains statements that may be deemed “forward-looking statements” within the meaning of U.S. securities laws, including statements regarding clinical trials, expected operations and upcoming developments. All statements in this press release other than statements of historical fact are forward-looking statements. These forward-looking statements may be identified by future verbs, as well as terms such as “potential,” “anticipating,” “planning” and similar expressions or the negatives thereof. Such statements are based upon certain assumptions and assessments made by management in light of their experience and their perception of historical trends, current conditions, expected future developments and other factors they believe to be appropriate. These statements include, without limitation, statements regarding the following: the potential promise of Rhenium (¹⁸⁶Re) Obisbemeda including the ability of Rhenium (¹⁸⁶Re) Obisbemeda to safely and effectively deliver radiation directly to the tumor at high doses; expectations as to the Company’s future performance including the next steps in developing the Company’s current assets; the Company’s clinical trials including statements regarding the timing and characteristics of the ReSPECT-GBM, ReSPECT-LM and ReSPECT-PBC, clinical trials; possible negative effects of Rhenium (¹⁸⁶Re) Obisbemeda; the continued evaluation of Rhenium (¹⁸⁶Re) Obisbemeda including through evaluations in additional patient cohorts; the intended functions of the Company’s platform and expected benefits from such functions; and the development, utility and potential of the CNSide leptomeningeal metastases diagnostic test.

The forward-looking statements included in this press release could differ materially from those expressed or implied by these forward-looking statements because of risks, uncertainties, and other factors that include, but are not limited to, the following: the early stage of the Company’s product candidates and therapies, the results of the Company’s research and development activities, including uncertainties relating to the clinical trials of its product candidates and therapies; the Company’s liquidity and capital resources and its ability to raise additional cash, the outcome of the Company’s partnering/licensing efforts, risks associated with laws or regulatory requirements applicable to it, market conditions, product performance, litigation or potential litigation, and competition within the cancer diagnostics and therapeutics field, ability to develop and protect proprietary intellectual property or obtain licenses to intellectual property developed by others on commercially reasonable and competitive terms, and material security breach or cybersecurity attack affecting the Company’s operations or property. This list of risks, uncertainties, and other factors is not complete. Plus Therapeutics discusses some of these matters more fully, as well as certain risk factors that could affect Plus Therapeutics’ business, financial condition, results of operations, and prospects, in its reports filed with the SEC, including Plus Therapeutics’ annual report on Form 10-K for the fiscal year ended December 31, 2023, quarterly reports on Form 10-Q, and current reports on Form 8-K. These filings are available for review through the SEC’s website at www.sec.gov. Any or all forward-looking statements Plus Therapeutics makes may turn out to be wrong and can be affected by inaccurate assumptions Plus Therapeutics might make or by known or unknown risks, uncertainties, and other factors, including those identified in this press release. Accordingly, you should not place undue reliance on the forward-looking statements made in this press release, which speak only as of its date. The Company assumes no responsibility to update or revise any forward-looking statements to reflect events, trends or circumstances after the date they are made unless the Company has an obligation under U.S. federal securities laws to do so.

Investor Contact
Charles Y. Huang, MBA
Director of Capital Markets and Investor Relations
Office: (202)-209-5751 | Direct (301)-728-7222
chuang@plustherapeutics.com