Plus Therapeutics’ REYOBIQ™ Shows Clinical Benefit and Safety in the ReSPECT-LM Clinical Trial for Patients with Leptomeningeal Metastases (LM)

Multiple long-term LM survivors in those patients receiving multiple doses of REYOBIQ

RNA sequencing data show early tumor apoptosis and activation of innate immune responses

Updated ReSPECT data presented at the 2025 Nuclear Medicine and Neurooncology Conference

HOUSTON, May 14, 2025 (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, announces the presentation of new data on its lead drug REYOBIQ™ (rhenium Re¹⁸⁶ obisbemeda) during both an oral presentation and a poster presented at the Nuclear Medicine and Neurooncology Conference. The meeting was held May 9-10, 2025 in Vienna, Austria.

“This newly presented data shows safety, clinical benefit and data supporting the underlying mechanism of action for REYOBIQ in patients with Leptomeningeal Metastases,” said Marc H. Hedrick, M.D., Plus Therapeutics President and Chief Executive Officer. “Furthermore, multiple doses of REYOBIQ were administered under compassionate use, mirroring how REYOBIQ may one day be used post approval and can contribute to long term survival in LM.”

The study, titled, “Rhenium Obisbemeda (REYOBIQ) in Leptomeningeal Metastases,” highlights additional data from the Company’s now complete Phase 1 ReSPECT-LM dose escalation trial. The presented data added further detail to the previously reported data from the submitted abstract, which demonstrated:

• 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 17 patients as of the data cutoff with five of those (29%) showing a partial response
• An additional eight patients showed stable disease by neuroimaging through day 112 for a Clinical Benefit Rate (complete response + partial response + stable disease) of 76% (13/17 – five partial responses and eight stable disease). Additionally, 87% of subjects demonstrated clinical response based on the physician evaluation (13/15 – 2 response and 11 stable disease)
• 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
• 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.
• In addition, of the seven patients who received a response of better than 80% in reduction of LM tumor cells in the cerebrospinal fluid, five survived at least one year following initial treatment.
• The study reports that three of those five were retreated via compassionate use.

Further details from the poster can be found here.

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).

About Plus Therapeutics
Headquartered in Houston, Texas, 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. Combining image-guided local beta radiation and targeted drug delivery approaches, the Company is advancing a pipeline of product candidates with lead programs in leptomeningeal metastases (LM) and recurrent glioblastoma (GBM). The Company has built a supply chain through strategic partnerships that enable the development, manufacturing, and future potential commercialization of its products. For more information, visit https://plustherapeutics.com/.

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