Plus Therapeutics Highlights Three REYOBIQ™ Clinical Data Presentations at 2025 WFNOS/SNO Annual Meeting

Cohort 1 data from multiple dose ReSPECT- Leptomeningeal Metastases (LM) trial
showed no dosage limiting toxicity

ReSPECT-Glioblastoma (GBM) trial of REYOBIQ as a novel therapeutic for recurrent GBM demonstrated promising safety and efficacy signal, supporting continued Phase 2 enrollment and investigation

MRI combined with SPECT imaging biomarkers effectively evaluate overall survival response with REYOBIQ in recurrent GBM treatment and help guide personalized patient planning

HOUSTON, Dec. 04, 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 three positive clinical data update presentations at the World Federation of Neuro-Oncology Societies/Society for Neuro-Oncology (WFNOS/SNO) Annual Meeting, November 19-23, 2025 in Honolulu, Hawaii. The World Federation of Neuro-Oncology Societies (WFNOS) and Society for Neuro-Oncology (SNO) advance research, education, and clinical care for patients with tumors of the central nervous system.

“Real world clinical experience with REYOBIQ in both primary and metastatic CNS cancers continues to show a promising safety profile and signs of efficacy,” said Marc H. Hedrick, M.D., Plus Therapeutics President and Chief Executive Officer. “This expanding clinical data set around REYOBIQ coupled with substantial progress bringing our CNSide diagnostic portfolio to market provides our team at Plus with growing confidence that we can achieve our goal of materially improving survival rates for patients with CNS cancers.”

KEY HIGHLIGHTS:

Phase 1 Multicenter Study of Multiple Doses of Rhenium (186Re) Obisbemeda (Reyobiq) for Leptomeningeal Metastases: Rationale, Design, and Preliminary Cohort 1 Data

Overview:

• Completed ReSPECT-LM single dose trial showed REYOBIQ was well-tolerated up to a maximum tolerated dose of 66mCi, with a recommended phase 2 dose of 44.1 mCi, and absorbed doses delivered of >300 Gy observed
• ReSPECT-LM open label, multidose Phase 1/2 trial initiated to identify maximum tolerated dose across varying dosing intervals and to characterize efficacy of multiple doses at optimal dose selected by assessing response using CNSide CSF tumor cell enumeration test

Response:

• Enrollment in Cohort 1 has begun with delivery of 13.2 mCi at 3 intervals
• Three patients enrolled as of data cutoff: one patient has received all doses without dose limiting toxicity

Next Steps:

• Phase 1b/2a dose optimization trial is enrolling with the ultimate goal of improving outcomes for LM patients

Phase 1/2 ReSPECT-GBM Trial of Rhenium (186Re) Obisbemeda in Recurrent Glioblastoma: Safety and Efficacy from the Phase 1 and Update on Phase 2

Overview:

• Phase 1 dose-escalation study completed, with patients dosed from 1.0 mCi to 41.5 mCi, achieving a maximum absorbed tumor dose of 739.5 Gy. Dose 22.3 mCi was selected as the recommended Phase 2 dose due to its favorable safety profile
• Ongoing Phase 2 study has enrolled 24 of planned 34 patients as of data cutoff; study continues to evaluate safety and efficacy at the Phase 2 recommended dose

Safety:

• Across all patients treated in both Phase 1 and 2, most treatment-related adverse events were Grade 1 or 2, including lymphopenia (7.9%), cognitive disorder (7.0%), and headache (7.0%), with no treatment-related deaths or study discontinuations due to serious adverse reactions (SARs)

Response:

• Efficacy data from Phase 1 cohorts 1 to 6 showed a median overall survival of 17 months for patients receiving ≥100 Gy, compared to 6 months for those receiving <100 Gy, surpassing historical bevacizumab monotherapy outcomes
• SPECT/CT imaging continues to confirm high tumor-specific radiation retention, with minimal systemic exposure

Next Steps:

• Phase 2 continues to enroll
• REYOBIQ has demonstrated promising safety and efficacy profile, supporting continued investigation as a novel therapeutic for recurrent GBM

Assessment of rhenium-186 obisbemeda (186RNL) therapy for recurrent glioblastoma (rGBM) using MRI and SPECT imaging biomarkers

Overview:

• Phase 1 ReSPECT-GBM showed promising improvements in overall survival
• REYOBIQ efficacy also evaluated using MRI and SPECT imaging biomarkers

Response:

• REYOBIQ dose positively correlates with treatment coverage ratio, time to peak, and progression free survival; negatively correlates with mean transit time and tumor volume
• Based on a Wilcoxon Signed Rank test on 23 patients receiving REYOBIQ, untreated tumor volume was significantly increased relative to treated tumor volume. Overall survival negatively associated with tumor volume

Conclusion:

• MRI combined with SPECT imaging biomarkers effectively evaluate REYOBIQ in recurrent GBM treatment, guiding patient specific planning

Plus Therapeutics and its wholly owned subsidiary, CNSide Diagnostics focused on central nervous system metastases management, each hosted a booth at the WFNOS/SNO Annual Meeting exhibit hall.

About LM
Leptomeningeal metastases (LM) are a rare but severe complication of advanced cancer, affecting the fluid-lined structures of the central nervous system. LM occurs in approximately 5% of patients with metastatic cancer, with breast cancer, lung cancer, and melanoma being the most common sources. Median survival is typically 2-6 months, and effective treatment options are limited, highlighting the urgent need for novel therapies.

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, leptomeningeal metastases, and pediatric brain cancer in the ReSPECT-GBM, ReSPECT-LM, and ReSPECT-PBC 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). The Company’s ReSPECT-PBC clinical trial for pediatric brain cancer is supported by a $3 million grant from the U.S. Department of Defense’s Peer Reviewed Cancer Research Program.

About CNSide Diagnostic, LLC
CNSide Diagnostics, LLC is a wholly owned subsidiary of Plus Therapeutics, Inc. that develops and commercializes proprietary laboratory-developed tests, such as CNSide®, designed to identify tumor cells that have metastasized to the central nervous system in patients with carcinomas and melanomas. The CNSide® CSF Assay Platform enables quantitative analysis of the cerebrospinal fluid that informs and improves the management of patients with leptomeningeal metastases.

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://www.plustherapeutics.com.

Forward-Looking Statements
This press release 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 “expect” “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.

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 Company’s ability to maintain the listing of its common stock on Nasdaq; risks related to a halt in trading or delisting of the Company’s common stock on Nasdaq; Medicare and private payors may not provide coverage and reimbursement or may breach, rescind or modify their contracts or reimbursement policies or delay payments; the risk that our products and services may not perform as expected; 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; challenges associated with radiotherapeutic manufacturing, production and distribution capabilities necessary to support the Company’s clinical trials and any commercial level product demand; 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, 2024, 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
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investor@plustherapeutics.com