Clinical-stage pharmaceutical company Plus Therapeutics Inc (Nasdaq:PSTV) announced on Friday that the US 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).

ODD status offers various benefits for rare disease treatments, including development assistance, tax credits, certain fee exemptions, and seven years of post-approval marketing exclusivity.

Rhenium (186Re) obisbemeda is currently under evaluation in the ReSPECT-LM Phase 1/2a clinical trial, with Cohort 4 recently completing enrolment. The FDA had previously granted Fast Track designation for this therapy.

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. It affects 3-5% of breast cancer patients, with limited survival rates. Rhenium (186Re) obisbemeda is an injectable radiotherapy offering targeted high-dose radiation to optimise outcomes for central nervous system (CNS) cancer patients.