Plus' CSF-01 cancer cell enumeration test is a sensitive and specific diagnostic test for the presence of adenocarcinoma and melanoma cancer cells in the leptomeninges

CSF-01 testing is used as an exploratory endpoint in the ReSPECT-LM trials

Controlled clinical trial data evaluating the utility of CSF-01 in clinical decision-making is anticipated to be released in Q2/Q3 2024

AUSTIN, Texas, March 25, 2024 (GLOBE NEWSWIRE) -- Plus Therapeutics, Inc. (Nasdaq: PSTV) (the "Company"), a clinical-stage pharmaceutical company developing targeted radiotherapeutics with advanced platform technologies for central nervous system (CNS) cancers, today announced it has successfully completed key validation testing and implementation of its tumor cell enumeration assay, known as CSF-01, to be used initially as an exploratory endpoint in its ReSPECT-LM clinical trials.

"Plus' CSF-01 tumor cell enumeration assay is a highly specific and sensitive diagnostic test that is promising for both establishing the diagnosis of leptomeningeal metastases (LM) and following the disease course over time," said Dr. Priya Kumthekar, Associate Professor, Feinberg School of Medicine, Northwestern University. "Current diagnostic methods lack the sensitivity and specificity to reliably inform clinical decision making, and the field is excited about the use of CSF-01 in the ReSPECT-LM trials as an exploratory endpoint and hopefully soon, for use in all patients in which LM is in the differential diagnosis."

Plus' CSF-01 cancer cell enumeration test is an exploratory endpoint in the ReSPECT-LM Phase 1 trial that has shown promise in the trial's early cohorts. In Phase 1/Part A of the ReSPECT-LM trial presented at the 2023 SNO/ASCO Meeting in San Francisco, Plus showed an average 53% reduction in CSF tumor cells 28 days after a single intrathecal administration of rhenium (186Re) obisbemeda in patients with LM.

"In mid-2023, the Company licensed CSF-01, as well as a broader CSF diagnostic testing portfolio due to high conviction that routine implementation will substantially improve diagnosis and clinical management of LM," said Marc H. Hedrick, M.D., President & CEO of Plus Therapeutics. "Our initial objective was to make the test available for our ReSPECT-LM trial patients, which is now complete. Now, we are evaluating the FORSEE clinical trial data, which we anticipate reporting in the second or third quarter of 2024."

On December 12, 2023, Plus announced its partnership with K2bio (Houston, Texas) to implement Plus' CSF-01 diagnostic for LM cancers in the ReSPECT-LM trials. While validated for use in Plus' clinical development programs, full Clinical Laboratory Improvement Amendments (CLIA) certification is not anticipated until 2025. The ReSPECT-LM trial, including support for CSF-01 testing, is currently receiving grant funding from the Cancer Prevention and Research Institute of Texas (CPRIT).

The FORSEE trial was performed by the original developer and licensor of CSF-01 and is a multi-center, prospective clinical trial enrolling patients with breast or non-small cell lung cancer (NSCLC) who have suspicious or confirmed LM. If the FORSEE data is positive, we intend to work toward increasing commercial reimbursement for the CLIA-certified test and explore partnerships to maximize diagnostic utilization for the broader CNS cancer space.