On April 15, 2025 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, reported the online availability of new data on its lead compound REYOBIQ (rhenium Re186 obisbemeda) in an abstract for both an oral presentation and a poster to be presented at the Nuclear Medicine and Neurooncology conference to be held May 9-10, 2025 in Vienna, Austria (Press release, Plus Therapeutics, APR 15, 2025, View Source [SID1234651962]).
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The abstract, titled, "Rhenium Obisbemeda (REYOBIQ) in Leptomeningeal Metastases," highlights additional data from the Company’s completed Phase 1 ReSPECT-LM dose escalation trial demonstrating a dose dependent increase in the average absorbed dose to the cranial and spinal subarachnoid space reaching 253Gy in Cohort 5. Neuroimaging response data was available for 16 patients as of the data cutoff with five of those (31%) showing a partial response. An additional seven patients showed stable disease by neuroimaging through day 112 for a Clinical Benefit Rate (complete response + partial response + stable disease) of 75%. Additionally, a clinical response based on the physician evaluation showed a decrease in disease findings in two of 14 evaluable patients (14%) and 10 patients showed stable findings through day 112 for an 86% Clinical Benefit Rate. Furthermore, there was no dose limiting toxicity (DLT) observed in the first four cohorts, with a grade 4 DLT (thrombocytopenia), one in each of Cohorts 5 and 6.
Finally, RNA sequencing of LM cells showed early induction of apoptosis, with an innate immune response followed by an increase in T cells and an adaptive immune response by Day 28. Further details can be found here; the Company will provide additional data and explanation following the meeting.
"This newly-presented ReSPECT-LM data further reinforces our confidence in the potential utility of REYOBIQ in these critically ill patients with the devastating diagnosis of Leptomeningeal Metastases," said Marc H. Hedrick, M.D., Plus Therapeutics President and Chief Executive Officer. "Reyobiq can be delivered at very high doses of radiation to the cancer at the recommended phase 2 dose and shows promising response data across multiple parameters while simultaneously being well tolerated by normal organs and tissues."
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 REYOBIQ (rhenium Re186 obisbemeda)
REYOBIQ (rhenium Re186 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. REYOBIQ 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. REYOBIQ 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).