Plus Therapeutics has achieved a significant regulatory milestone as the U.S. Food and Drug Administration (FDA) granted Orphan Drug Designation (ODD) to Rhenium (186Re) Obisbemeda for treating leptomeningeal metastases (LM) in lung cancer patients. This designation strengthens the company's position in developing targeted radiotherapeutics for central nervous system cancers.
Clinical Development Progress
The ODD announcement follows the successful completion of the ReSPECT-LM Phase 1 single-dose trial, which has determined the recommended Phase 2 dose (RP2D). Plus Therapeutics is currently advancing both a Phase 2 single-dose expansion trial and a Phase 1 multiple-dose trial, while actively engaging with the FDA to establish an optimal pivotal trial strategy.
"Receiving Orphan Drug Designation for Rhenium (186Re) Obisbemeda marks a significant milestone in our efforts to develop a much-needed therapy for lung cancer patients with leptomeningeal metastases," stated Mike Rosol, Ph.D., Plus Therapeutics Chief Development Officer. "These patients currently have limited treatment options, and the growing incidence of LM in lung cancer underscores the urgency for new therapies."
Therapeutic Significance and Market Impact
The ODD status, granted to drugs treating conditions affecting fewer than 200,000 people in the United States, provides Plus Therapeutics with several strategic advantages:
- Seven years of potential market exclusivity
- Tax credits for qualified clinical trials
- Exemption from significant regulatory fees, including the $4.3 million PDUFA charge in 2025
- Waiver of Pediatric Research Equity Act requirements
Understanding Leptomeningeal Metastases
LM represents a severe complication occurring in approximately 5% of cancer patients, where cancer spreads to the cerebrospinal fluid and leptomeninges surrounding the brain and spinal cord. The condition presents particularly poor outcomes, with just 7% survival at one year and 3% at two years. Currently, there are no FDA-approved therapies specifically for LM patients.
Innovation in Treatment Approach
Rhenium (186Re) obisbemeda offers a novel approach to treating CNS tumors through targeted radiotherapy. The treatment leverages rhenium-186's unique properties, including:
- Short half-life optimal for therapeutic application
- Beta energy capability for destroying cancerous tissue
- Gamma energy properties enabling live imaging
The development program has garnered significant support, including funding through a $17.6M grant from the Cancer Prevention & Research Institute of Texas (CPRIT), highlighting the treatment's potential impact on this underserved patient population.
