Plus Therapeutics Secures FDA Orphan Drug Designation for REYOBIQ™ in Pediatric Malignant Gliomas

HOUSTON, Texas, April 8, 2026 – Plus Therapeutics, Inc. (Nasdaq: PSTV), a clinical-stage pharmaceutical leader in targeted radiotherapeutics for central nervous system (CNS) cancers, has announced a major regulatory milestone: the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation (ODD) to its lead candidate, REYOBIQ™ (rhenium Re186 obisbemeda), for the treatment of pediatric malignant gliomas, including the broader indication of pediatric ependymoma.

Key Highlights for Investors

• Orphan Drug Designation Secured: The FDA granted ODD for REYOBIQ™ in pediatric malignant gliomas, broadening the scope to include pediatric ependymoma—potentially expanding market opportunity and addressable patient population.
• Significant Unmet Need: Pediatric malignant gliomas are rare, aggressive brain tumors with poor outcomes and limited treatment options. Current therapies, such as surgery and radiation, often fail to prevent recurrence, with 5-year survival rates as low as 22% for high-grade gliomas.
• Regulatory and Clinical Momentum: The new ODD builds on recent progress, including a successful Type B FDA meeting supporting REYOBIQ’s development for leptomeningeal metastases (LM), positive early clinical data from the ReSPECT-LM trial, and ongoing Phase 1 and Phase 2 studies. Plus Therapeutics also received FDA IND clearance to evaluate REYOBIQ in pediatric high-grade glioma and ependymoma.
• Orphan Drug Benefits: The ODD provides Plus Therapeutics with several advantages if REYOBIQ is approved:
  • Seven years of market exclusivity in the U.S.
  • Tax credits for qualified clinical trial expenses
  • Exemptions from certain regulatory fees
• Product Profile: REYOBIQ is a novel, injectable radiotherapy delivering targeted, high-dose radiation to CNS tumors, designed to optimize efficacy while minimizing exposure to healthy brain tissue. It uses rhenium-186, a radioisotope with an optimal profile for CNS applications, allowing both cancer cell destruction and real-time imaging.
• Broader Pipeline and Funding: The REYOBIQ platform is being evaluated in several clinical trials, including ReSPECT-GBM for recurrent glioblastoma (supported by the NIH), ReSPECT-LM for leptomeningeal metastases (funded by a \$17.6 million CPRIT grant), and ReSPECT-PBC for pediatric brain cancer (supported by a \$3 million Department of Defense grant).
• Subsidiary Focus: Plus Therapeutics’ CNSide Diagnostics subsidiary develops proprietary CSF-based assays (CNSide®) for detecting CNS metastases, supporting its position in advanced CNS cancer diagnostics.

Price-Sensitive Information & Shareholder Considerations

• Potential for Share Price Movement: The ODD news is likely to be price sensitive, as it enhances the company’s competitive position, provides regulatory incentives, and broadens its clinical and commercial prospects in a high-need, under-served pediatric cancer market.
• Market Exclusivity: The potential for seven years of U.S. market exclusivity represents a significant commercial advantage, should approval be gained.
• Pipeline De-Risking: The FDA’s willingness to expand the ODD to cover ependymoma signals regulatory support and could positively impact investor sentiment regarding the probability of clinical and commercial success across multiple indications.
• Funding and Grants: The company’s ongoing receipt of substantial non-dilutive funding for its clinical programs demonstrates external validation and reduces immediate financial risk for shareholders.
• Growth in Addressable Market: The expanded scope of the ODD increases the potential patient pool and revenue opportunity for REYOBIQ, positioning Plus Therapeutics for future growth.

About Pediatric Malignant Gliomas and Leptomeningeal Metastases

• Pediatric high-grade gliomas (HGG), including ependymoma, are rare (about 3.3 cases per 100,000) but aggressive, with standard treatments often failing to prevent recurrence. Prognosis is especially poor in recurrent cases.
• Leptomeningeal metastases (LM) are an increasingly recognized and terminal complication of various cancers, with very limited treatment options and no FDA-approved therapies. LM occurs in approximately 5% of people with cancer, with survival rates of only 7% at one year if untreated.

About Plus Therapeutics

Headquartered in Houston, Texas, Plus Therapeutics is developing targeted radiotherapeutics for difficult-to-treat CNS cancers. The company leverages image-guided beta radiation and targeted drug delivery, with a pipeline focused on recurrent glioblastoma, leptomeningeal metastases, and pediatric brain cancers. Strategic partnerships support its manufacturing, development, and commercialization capabilities.

Forward-Looking Statements

This announcement contains forward-looking statements regarding the development, potential, and expected regulatory and commercial milestones for REYOBIQ and other candidates. Risks include uncertainties in clinical development, regulatory approval, and market adoption. Investors are urged to review Plus Therapeutics’ SEC filings for a full discussion of risk factors.

Disclaimer: This article is for informational purposes only and does not constitute investment advice. Investors should perform their own due diligence and consult with their financial advisors before making investment decisions. The information herein is based on company disclosures and is subject to change without notice.

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