Plus Therapeutics Announces Positive Interim Data from ReSPECT™ Phase 1 Clinical Trial in Recurrent Glioblastoma

Investigational drug RNL™ delivers up to fifteen times the absorbed dose of radiation compared to standard external beam radiation therapy

RNL was generally well-tolerated with no dose-limiting toxicities observed

Company management and principal investigator of ReSPECT to discuss interim data during webinar scheduled for Thursday, November 19, 2020 at 4:30 – 5:30 p.m. ET

AUSTIN, Texas, Nov. 19, 2020 (GLOBE NEWSWIRE) — Plus Therapeutics, Inc. (Nasdaq: PSTV) (the “Company”), a clinical-stage pharmaceutical company developing novel, targeted and personalized therapies for rare and difficult to treat cancers, today announced positive new interim data from its ongoing ReSPECT™ Phase 1 clinical trial evaluating the Company’s lead investigational asset, Rhenium NanoLiposome (RNL™), in patients with recurrent glioblastoma (GBM). These results were presented in an electronic poster entitled, “Safety and Feasibility of Rhenium-186 Nanoliposomes (RNL™) in Recurrent GBM: the ReSPECT Phase 1 Trial,” at the 2020 Society for Neuro-Oncology (SNO) Annual Meeting, which is taking place virtually November 19-21, 2020.

The interim data set shows that intratumoral RNL can successfully deliver up to fifteen times the absorbed dose of radiation administered by standard external beam radiation therapy (EBRT) without significant toxicity. These data support progression to the ReSPECT trial’s sixth dose escalation cohort.

“The results we have seen thus far from ReSPECT are encouraging and support the continued development of RNL as a potential new option for recurrent GBM patients,” said Andrew J. Brenner, M.D., Ph.D., Associate Professor of Medicine, Neurology, and Neurosurgery at The University of Texas, Health Services Center at San Antonio and principle investigator of the study. “With limited therapeutic options for these patients, we remain committed to advancing this clinical program to further investigate the therapeutic potential of RNL.”

“Treatment for glioblastoma remains a significant challenge as current therapies have exhibited limited efficacy,” stated Marc Hedrick, M.D., President and Chief Executive Officer of Plus Therapeutics. “RNL’s novel design allows the drug to be targeted directly into the tumor using a small catheter and enabling greater control of radiation dosing. These encouraging data reinforce RNL’s potential to deliver targeted high-dose radiation in a safe, effective, and convenient manner.”

Key Results from the Interim Analysis

• All 15 patients in the first five of six planned cohorts have completed treatment.
• RNL treatment volume and radiation dose increased successfully from 0.66 milliliter (mL) to 8.8 mL and 1.0 millicurie (mCi) to 22.3 mCi, respectively.
• Cohort 5 patients received an RNL average absorbed radiation dose of 423 Gray (Gy).
• RNL has been well-tolerated, and no dose-limiting toxicity has been observed despite markedly higher absorbed doses of radiation compared to EBRT.
• Most adverse events (AEs) were considered causally unrelated to RNL except scalp discomfort, which was considered related to the surgical procedure. Neither the incidence nor severity of AEs appeared to increase with increasing doses of RNL.
• Four serious adverse events (SAEs) were reported, none of the SAEs were considered causally related to RNL.
• Median survival duration in patients that previously received bevacizumab (n=7) was 4.8 months, while median and mean survival durations in patients that were bevacizumab-naïve (n=8) are currently 11.0 months (range 3.5 – 33) and 15.4 months (95% CI 7.4 – 23.4), respectively, with four patients still alive.
• Two patients survived greater than 30 months after therapy with RNL.

The sixth dose escalation cohort of the ReSPECT trial is underway and one patient has thus far been treated. The sixth cohort is expected to fully enroll by the end of 2020. In September 2020, the U.S. Food and Drug Administration (FDA) granted both Orphan Drug designation and Fast Track designation to RNL for the treatment of patients with glioblastoma. Additional details about the ReSPECT trial are available at clinicaltrials.gov (NCT01906385).

Webinar details

The Company will host a webinar today, Thursday, November 19, 2020, 4:30 to 5:30 p.m. ET discussing these data. Andrew J. Brenner, M.D., Ph.D., Associate Professor of Medicine, Neurology, and Neurosurgery at The University of Texas, Health Services Center at San Antonio, will provide an update on the ReSPECT trial and provide insight on the trial data. In addition, a patient with recurrent GBM from the ReSPECT trial will provide their treatment experience with RNL.

Marc Hedrick, M.D., President and Chief Executive Officer of Plus Therapeutics, and Gregory D. Stein, M.D., M.B.A., Senior Vice President, Clinical Development of Plus Therapeutics, will discuss the technology behind RNL as well as the current treatment landscape and unmet medical need in treating patients with recurrent GBM.

The live webinar with accompanying slides will be available in the Events page of the ‘Investors’ section of the Plus Therapeutics website or by clicking here. Individuals can participate in an interactive Q&A session by submitting pertinent questions via the webcast platform.

Please log in approximately 10 minutes prior to the scheduled start time. The archived webcast will be available in the Events section of the Company’s website for 90 days.

A live audio conference will be available by dialing (833) 340-0285 (toll-free) or (236) 712-2475 and entering Conference ID 6095968.

Andrew J. Brenner, M.D., Ph.D.

Dr. Brenner is a nationally known expert in the treatment of brain and breast cancers, with a particular research interest in developing new treatments. He has served on multiple committees and panels including for the National Institutes of Health, National Cancer Institute, Department of Defense Breast Cancer Research Program, and others. He has also served on advisory committees for a number of companies to help direct development of new drugs. His laboratory work developing new treatments has been funded by the Food and Drug Administration, National Cancer Institute, and Cancer Prevention and Research Institute of Texas. He has published nearly 50 original research articles in peer reviewed journals. Dr. Brenner is a member of the Plus Therapeutics Scientific Advisory Board.

About Plus Therapeutics, Inc.

Plus Therapeutics (Nasdaq: PSTV) is a clinical-stage pharmaceutical company whose radiotherapeutic portfolio is concentrated on nanoliposome-encapsulated radionuclides for several cancer targets. Central to the Company’s drug development is a unique nanotechnology platform designed to reformulate, deliver and commercialize multiple drugs targeting rare cancers and other diseases. The 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 certain statements that may be deemed “forward-looking statements” within the meaning of U.S. securities laws. All statements, other than statements of historical fact, that address activities, events or developments that we intend, expect, project, believe or anticipate and similar expressions or future conditional verbs such as will, should, would, could or may occur in the future are forward-looking statements. Such statements are based upon certain assumptions and assessments made by our 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 about: the Company’s potential 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; the Company’s potential to develop drug candidates currently in its product pipeline; and the Company’s potential to develop additional drugs outside of its current pipeline. The forward-looking statements included in this press release are subject to a number of additional material risks and uncertainties, including but not limited to: the risk that the Company is not able to successfully develop product candidates that can leverage the U.S. FDA’s accelerated regulatory pathways; and the 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.

Investor Contact
Peter Vozzo
Westwicke/ICR
(443) 377-4767
Peter.Vozzo@westwicke.com

Media Contact
Terri Clevenger
Westwicke/ICR
(203) 856-4326
Terri.Clevenger@westwicke.com

A video accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/5639e2df-2399-4963-8796-f86e100ffa8e