Plus Therapeutics Granted U.S. FDA Orphan Drug Designation to Rhenium (186Re) Obisbemeda for the Treatment of Breast Cancer with Leptomeningeal Metastases

On November 3, 2023 Plus Therapeutics, Inc. (Nasdaq: PSTV) (the "Company"), a clinical-stage pharmaceutical company developing targeted radiotherapeutics with advanced platform technologies for central nervous system cancers, reported that the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation (ODD) to rhenium (186Re) obisbemeda for the treatment of breast cancer with leptomeningeal metastases (LM) (Press release, PLUS THERAPEUTICS, NOV 3, 2023, View Source [SID1234636917]).

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ODD status is granted by the FDA to an investigational drug or biological product intended to prevent, diagnose or treat a rare diseases or condition affecting fewer than 200,000 people in the United States. Companies granted ODD are eligible for certain benefits, including assistance in the drug development process, tax credits for clinical costs, exemptions from certain FDA fees and 7 years of post-approval marketing exclusivity.

"Receiving Orphan Drug Designation from the FDA is important validation of our radiotherapeutic candidate for breast cancer patients with LM who currently have no FDA-approved treatment options," said Marc H. Hedrick M.D., President and Chief Executive Officer of Plus Therapeutics. "LM is a rapidly progressing and fatal complication of several cancers, including breast cancer, and incidence continues to rise. ODD status, together with the previously granted Fast Track designation, underscores the significant and urgent need for new treatment options for LM. We believe rhenium (186Re) obisbemeda has the potential to address this unmet need, and we look forward to continued progress of our ReSPECT-LM program."

Rhenium (186Re) obisbemeda is currently being evaluated in the ReSPECT-LM Phase 1/2a dose escalation clinical trial. Cohort 4 of the ReSPECT-LM trial recently completed enrollment, and the Company anticipates moving into Cohort 5 following standard safety review. Updates on the ReSPECT-LM trial will be presented at the Society for Neuro-Oncology Annual Meeting November 15-19, 2023. In addition to ODD, the FDA previously granted rhenium (186Re) obisbemeda Fast Track designation for the treatment of LM.

About Leptomeningeal Metastases (LM)

LM is a rare complication of cancer in which the primary cancer spreads to the cerebrospinal fluid (CSF) 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 (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-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 live imaging. Rhenium (186Re) 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).