Plus Therapeutics, a company developing targeted radiotherapeutics for central nervous system (CNS) cancers, 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,” says 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, the company says. 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. Rhenium (186Re) obisbemeda is a novel injectable radiotherapy specifically formulated to deliver directly targeted high-dose radiation in CNS tumors in a safe, effective, and convenient manner to optimize patient outcomes.
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“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,” says Marc H. Hedrick, MD, 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 Dec. 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.
