Plus Therapeutics Presents Positive Data from Ongoing ReSPECT™ Clinical Trials at the Annual Conference on CNS Clinical Trials and Brain Metastases

AUSTIN, Texas, Aug. 13, 2022 (GLOBE NEWSWIRE) — Plus Therapeutics, Inc. (Nasdaq: PSTV) (the “Company”), a clinical-stage pharmaceutical company developing innovative, targeted radiotherapeutics for rare and difficult-to-treat cancers, yesterday presented positive data from two ongoing clinical trials of its lead investigational drug, Rhenium-186 Nanoliposome (¹⁸⁶RNL), in the treatment of recurrent glioblastoma (GBM) and leptomeningeal metastases (LM) at the 2022 Annual Conference on CNS Clinical Trials and Brain Metastases. The conference is co-sponsored by the Society for Neuro-Oncology (SNO) and the American Society of Clinical Oncology (ASCO) and is being held August 12-13, 2022 in Toronto, Canada.

The oral presentation, titled Safety and Feasibility of Rhenium-186 Nanoliposome (¹⁸⁶RNL) in Leptomeningeal Metastases Phase 1/2a Dose Escalation Trial [LOCL-04], demonstrated that the ¹⁸⁶RNL dose administered through an intraventricular catheter at 6.6 mCi in 5.0 mL achieved absorbed doses of 18.7 to 29.0 Gy to the ventricles and cranial subarachnoid space, which was well tolerated with no treatment-related adverse events of greater than grade 1. Furthermore, all three patients in the cohort were observed to have prompt and complete ¹⁸⁶RNL distribution throughout the cerebrospinal fluid (CSF) subarachnoid space that was durable past one week and very well tolerated. Importantly, all patients showed a decreased CSF cell count by microfluidic chamber assay after treatment, ranging from 65% to 92% which was also durable.

“While we can draw only limited conclusions from the first patient cohort, these findings suggest that the application of locally delivered and highly targeted 186RNL for the treatment of LM has the potential to be an effective and safe treatment for patients,” stated Norman LaFrance, M.D., Chief Medical Officer and SVP at Plus Therapeutics.

“Leptomeningeal metastases are a devastating complication of cancer that often force patients to choose between toxic therapies or a limited life expectancy that builds on top of the already complex burden of their underlying cancer. However, our approach to deliver ¹⁸⁶RNL is precisely targeted to the CNS and minimizes radiation exposure to other parts of the body and importantly has the potential to extend patient survival,” said Andrew J. Brenner, M.D., Ph.D., Professor of Medicine, Neurology, and Neurosurgery at The University of Texas Health Science Center at San Antonio and principal investigator of the ReSPECT-LM clinical trial. “We look forward to continuing the clinical evaluation with additional dose escalations to further assess ¹⁸⁶RNL’s versatility and on behalf of patients in need.”

Dr. Brenner also presented a poster titled, Safety and Feasibility of Rhenium-186 NanoLiposome (¹⁸⁶RNL) in Recurrent Glioma: the ReSPECT™ Phase 1 Trial [LOCL-08], which demonstrated that in 23 subjects with recurrent GBM receiving a single administration of ¹⁸⁶RNL, significant overall survival benefits were observed in those achieving an average absorbed radiation dose greater than 100 Gy to the tumor compared to those with less absorption. These findings suggest a correlation in increasing convected drug volume and radiation dose with improvement in overall survival of patients and to date, 80% of patients in cohorts 5-7 met the threshold of high levels of absorption greater than 100 Gy.

Data show ¹⁸⁶RNL treatment is safe and well-tolerated, with no adverse events (AEs) with outcome of death or discontinuations. At the time of the presentation, four patients remain alive. Cohort 7 of the trial, with an increased dose of ¹⁸⁶RNL (31.2 mCi and infusate volume 12.3 mL), is currently enrolling.

“Taken together, these data from both ReSPECT-LM and ReSPECT-GBM represent Plus’ ongoing dedication to evaluating ¹⁸⁶RNL in clinical settings and the encouraging results showing our product is safe and effective in treating these difficult-to-treat cancers,” said Marc Hedrick, M.D., President and Chief Executive Officer of Plus Therapeutics. “As we look ahead to the rest of 2022, we remain focused on completing key manufacturing, clinical and regulatory milestones that will support the further development and validation of ¹⁸⁶RNL so we can quickly bring our therapy to patients.”

A copy of the poster and presentation will also be available under the Presentations tab of the Investors section of the Company’s website at https://ir.plustherapeutics.com.

About Plus Therapeutics

Plus Therapeutics, Inc. is a clinical-stage pharmaceutical company focused on the development, manufacture, and commercialization of complex and innovative treatments for patients battling cancer and other life-threatening diseases. Our proprietary nanotechnology platform is currently centered around the enhanced delivery of a variety of drugs using novel liposomal encapsulation technology. Liposomal encapsulation has been extensively explored and undergone significant technical and commercial advances since it was first developed. Our platform is designed to facilitate new delivery approaches and/or formulations of safe and effective, injectable drugs, potentially enhancing the safety, efficacy and convenience for patients and healthcare providers. More information may be found at PlusTherapeutics.com and ReSPECT-Trials.com.

Cautionary Statement Regarding Forward-Looking Statements

This press release contains statements that may be deemed “forward-looking statements” within the meaning of U.S. securities laws. 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 “designed to,” “will,” “can,” “potential,” “focus,” “preparing,” “next steps,” “possibly,” 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. These statements include, without limitation, statements regarding the following: the potential promise of ¹⁸⁶RNL including the ability of ¹⁸⁶RNL to safely and effectively deliver radiation directly to the tumor at high doses; expectations as to the Company’s future performance including the next steps in developing the Company’s current assets; the Company’s clinical trials including statements regarding the timing and characteristics of the ReSPECT-GBM and ReSPECT-LM clinical trials; possible negative effects of ¹⁸⁶RNL; the continued evaluation of ¹⁸⁶RNL including through evaluations in additional patient cohorts; and the intended functions of the Company’s platform and expected benefits from such functions.

The forward-looking statements included in this press release are subject to a number of risks and uncertainties that may cause actual results to differ materially from those discussed in such forward-looking statements. These risks and uncertainties include, but are not limited to: the Company’s actual results may differ, including materially, from those anticipated in these forward-looking statements as a result of various factors, including, but not limited to, the following: 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, among others; and additional risks described under the heading “Risk Factors” in the Company’s Securities and Exchange Commission filings, including in the Company’s annual and quarterly reports. There may be events in the future that the Company is unable to predict, or over which it has no control, and its business, financial condition, results of operations and prospects may change in the future. 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.

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