Plus Therapeutics Completes Enrollment of the Original Three Patients Required for Cohort 8 of ReSPECT-GBM Phase 1/2a Trial

Presentation of data from ReSPECT-GBM Phase 1/2a and Phase 2b trials expected second half of 2023

AUSTIN, Texas, April 19, 2023 (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 cancers, today announced the completion of enrollment of the original three patients required in Cohort 8 of the ReSPECT-GBM Phase 1/2a dose escalation clinical trial of rhenium (¹⁸⁶Re) obisbemeda for the treatment of recurrent glioblastoma (GBM). Within the dose escalation phase of the trial, the Company has treated 27 patients to date.

In Cohort 8 of the Phase 1/2a trial, patients with large-sized tumors were administered a 41.5 mCi dose of rhenium (¹⁸⁶Re) obisbemeda within an infused volume of 16.34 mL. In parallel, the Company is advancing a Phase 2b clinical trial evaluating rhenium (¹⁸⁶Re) obisbemeda in recurrent GBM with small- to medium-sized tumors and also has a retreatment option for qualifying patients who have already received rhenium (¹⁸⁶Re) obisbemeda.

“Alongside our site partners, Plus has successfully recruited and dosed a total of seven patients this year alone, and we plan to continue this momentum in order to uncover new insights about the potential of rhenium (¹⁸⁶Re) obisbemeda,” said Norman LaFrance, M.D., Chief Medical Officer of Plus Therapeutics. “Across both clinical trials in recurrent glioblastoma, we have seen an absorbed dose of rhenium (¹⁸⁶Re) obisbemeda of up to 740 Gray, indicating a powerful and targeted attack on the tumor. We look forward to continuing to generate additional safety and efficacy data that we intend to share later this year with the U.S. Food and Drug Administration (FDA) and present at upcoming medical meetings.”

The U.S. FDA granted both Orphan Drug designation and Fast Track designation to rhenium (¹⁸⁶Re) obisbemeda for the treatment of GBM. More information about the ReSPECT-GBM trial may be found at ReSPECT-Trials.com and ClinicalTrials.gov (NCT01906385).

About Rhenium (¹⁸⁶Re) obisbemeda

Rhenium (¹⁸⁶Re) obisbemeda is a novel injectable radiotherapy specifically formulated to deliver highly targeted high dose radiation in CNS tumors in a safe, effective and convenient manner to optimize patient outcomes. Rhenium (¹⁸⁶Re) obisbemeda has the potential to reduce risks and improve outcomes for CNS cancer patients, versus currently approved therapies, with a more targeted and potent radiation dose. Rhenium is an ideal radioisotope for CNS therapeutic applications due to its short half-life, beta energy for destroying cancerous tissue and gamma energy for live imaging.

About Plus Therapeutics

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 for patients. Combining image-guided local beta radiation and targeted drug delivery approaches, the Company is advancing a pipeline of product candidates with lead programs in recurrent glioblastoma (GBM) and leptomeningeal metastases (LM). The Company has built a robust supply chain through strategic partnerships that enable the development, manufacturing and future potential commercialization of its products. Plus Therapeutics is led by an experienced and dedicated leadership team and has operations in key cancer clinical development hubs including Austin and San Antonio, Texas. For more information, visit https://plustherapeutics.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 ¹⁸⁶Re including the ability of ¹⁸⁶Re 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 ¹⁸⁶Re; the continued evaluation of ¹⁸⁶Re 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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