Plus Therapeutics (Nasdaq: PSTV) announced receipt of orphan drug designation from the FDA for Reyobiq (rhenium Re186 obisbemeda) for pediatric malignant gliomas, with the company adding that the designation was granted broadly enough to include pediatric ependymoma. The designation may provide development incentives including tax credits, user-fee exemptions, and, if ultimately approved for the indication, seven years of US orphan exclusivity.
Reyobiq is an investigational locally delivered nanoliposomal radiotherapeutic being studied in pediatric high-grade glioma/ependymoma, leptomeningeal metastases, and recurrent glioma. The asset is currently being evaluated in the ReSPECT-PBC trial (NCT07061626) in pediatric patients with high-grade glioma and ependymoma, a Phase I/IIa study listed as not yet recruiting. The pediatric program runs alongside two leptomeningeal metastases studies — a single-dose Phase I trial (NCT05034497) that is active but no longer recruiting, and a multiple-dose Phase I trial (NCT07098806) currently recruiting — as well as a Phase I/II study in recurrent glioma (NCT01906385). A 2025 publication in Nature Communications reported Phase I data from the recurrent glioma arm.
In pediatric high-grade glioma, treatment options remain limited, though Jazz Pharmaceuticals won US FDA accelerated approval in August 2025 for dordaviprone (ONC201) in H3 K27M-mutant diffuse midline glioma, marking the first approved systemic therapy for that subset and underscoring a distinct mechanism versus Reyobiq’s locally delivered radiotherapeutic approach. The localized beta-emission approach of rhenium-186, with tissue penetration of approximately 2 mm, is mechanistically distinct from systemic agents and external beam radiotherapy, which remains a standard of care alongside surgical resection.