Plus Therapeutics Secures $5.7 Million Financing to Support Leptomeningeal Metastases Program

$3.7 Million Private Placement Financing from Existing Investors

$2.0 Million Funding Advance from the Cancer Prevention and Research Institute of Texas (CPRIT)

AUSTIN, Texas, Feb. 18, 2025 (GLOBE NEWSWIRE) -- Plus Therapeutics, Inc. (Nasdaq: PSTV) (the "Company," or "Plus Therapeutics"), a clinical-stage pharmaceutical company developing targeted radiotherapeutics with advanced platform technologies for central nervous system $(CNS)$ cancers, announced today that it has closed a private placement with aggregate initial upfront proceeds of approximately $3.7 million and received a $2.0 million advance payment from CPRIT as part of its existing $17.6 million grant award. The funding from the private placement and the CPRIT advance will support the Company's clinical development of Rhenium ((186) Re) Obisbemeda for leptomeningeal metastases (LM), as well as further development of the Company's CNSide LM diagnostic test as a pivotal trial endpoint.

"We are grateful for the enthusiasm and ongoing support from both existing investors and key funding agencies, including CPRIT, the National Institutes of Health, and the U.S. Department of Defense," said Marc H. Hedrick, M.D., Plus Therapeutics' President and Chief Executive Officer. "This capital, along with expected grant allocations later in 2025, is expected to fully support the completion of two planned LM trials, strategically positioning the company for a pivotal trial in 2026."

Private Placement Financing

The private placement comprised the issuance and sale of secured convertible promissory notes, or Funding Notes, in the aggregate amount of $3,362,251 and common stock purchase warrants to purchase up to an aggregate of 3,002,009 shares of the Company common stock at an exercise price of $1.12 per share. The notes have a maturity date of one year from the closing of the financing and are convertible in future financings of the Company or into common stock at the election of the investors. The financing includes participation from AIGH Capital Management LLC with additional participation from existing healthcare-focused institutional investors.

The accompanying Warrants will be exercisable until the five-year anniversary of the closing of the financing.

The Notes are convertible, under certain circumstances, to shares of common stock of the Company at an exercise price of $1.12 per share. The Notes are senior, secured obligations of the Company. The Notes bear interest at the rate of ten percent (10%) per annum, payable on the last business day of each quarter, except as provided therein.

The gross proceeds to the Company from the private placement were approximately $3.7 million, before deducting offering expenses payable by the Company. The Company currently intends to use the net proceeds from the private placement for general corporate and working capital purposes.

The securities offered in the private placement and described above were offered in transactions not involving a public offering under Section 4(a)(2) of the Securities Act of 1933, as amended (the "Securities Act") and/or Rule 506(b) of Regulation D promulgated thereunder and have not been registered under the Securities Act or applicable state securities laws. Accordingly, the securities in the private placement may not be reoffered or resold in the United States except pursuant to an effective registration statement with the SEC or an applicable exemption from the registration requirements of the Securities Act and such applicable state securities laws.

This press release does not constitute an offer to sell or the solicitation of an offer to buy the securities, nor shall there be any sale of the securities in any state in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of such state. Any offering of the securities under the resale registration statement will only be made by means of a prospectus.

CPRIT Funding Advance

In addition to the $3.7 million private placement financing from existing investors, the Company announced a $2.0 million advance payment from CPRIT as part of its existing $17.6 million grant award. The funding will support and accelerate the Company's clinical development of Rhenium ((186) Re) Obisbemeda for the ReSPECT-LM P2a single-dose expansion trial and further develop the Company's CNSide LM diagnostic test as a key pivotal trial endpoint.

To date, the Company has received multiple disbursements under its CPRIT grant. Following this $2.0 million advance payment, approximately $5.2 million remains from the original $17.6 million grant award.

Exchange and Financing Waiver

On February 13, 2025, the Company also issued secured convertible promissory notes, or Exchange Notes, in the aggregate amount of $3,188,922 in exchange for existing investors agreeing to cancel 3,543,247 Series A common stock purchase warrants issued by the Company in May 2024 and waive certain existing restrictions on the Company's ability to raise capital. The terms of the Exchange Notes are substantially similar to the terms of the Funding Notes.

Additional information on the terms of the Funding Notes, Warrants, Exchange Notes and related matters can be found in the Company's Current Report on Form 8-K that is being filed by the Company on February 18, 2025.

About Leptomeningeal Metastases (LM)

LM is a rare complication of cancer in which the primary cancer spreads to the cerebrospinal fluid $(CSF.AU)$ 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 Rhenium ((186) Re) obisbemeda

Rhenium ((186) Re) 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. Rhenium ((186) Re) obisbemeda 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. Rhenium ((186) Re) obisbemeda 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 the Cancer Prevention & Research Institute of Texas (CPRIT)

CPRIT was created by the Texas Legislature and approved by a statewide vote in 2007 to lead the Lone Star State's fight against cancer. In 2019, Texas voters again voted overwhelmingly to continue CPRIT with an additional $3 billion for a total $6 billion investment in cancer research and prevention.

To date, CPRIT has awarded over $3 billion in grants to Texas research institutions and organizations through its academic research, prevention and product development research programs. CPRIT has recruited 281 distinguished researchers, supported the establishment, expansion or relocation of 52 companies to Texas and generated over $7.66 billion in additional public and private investment. CPRIT funding has advanced scientific and clinical knowledge and provided 8.2 million life-saving cancer prevention and early detection services reaching Texans from all 254 counties. Learn more at https://cprit.texas.gov/about-us

About CNSide Diagnostic, LLC

CNSide Diagnostics, LLC is a wholly owned subsidiary of Plus Therapeutics, Inc. that develops and commercializes proprietary clinical diagnostic laboratory assays, such as CNSide, designed to identify tumor cells that have metastasized to the central nervous system in patients with carcinomas and melanomas. The CNSide$(TM)$ Assay Platform enables quantitative analysis and molecular characterization of tumor cells and circulating tumor DNA in the cerebrospinal fluid that inform and improve the clinical management of patients with leptomeningeal metastases. The Company is planning to commercialize CNSide in the U.S. in 2025.

About CNSide Test

The CNSide Cerebrospinal Fluid $(CSF)$ Assay Platform consists of four laboratory developed tests (LDTs) used for diagnosis, treatment selection, and treatment monitoring of patients with Leptomeningeal Metastases (LM) from carcinomas or melanoma. The CNSide platform facilitates tumor cell detection / enumeration and biomarker identification using cellular assays (immunocytochemistry (ICC) and fluorescence in situ hybridization (FISH)) and molecular assays (next generation sequencing $(NGS)$). The CNSide CSF tumor cell enumeration LDT is currently being used in the ReSPECT-LM trial as an exploratory endpoint and will be commercially available in 2025.

About Plus Therapeutics

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