FDA Grants Orphan Drug Status to Plus Therapeutics' Rhenium (186Re) for Lung Cancer Leptomeningeal Metastases

HOUSTON, March 06, 2025 — Plus Therapeutics, Inc., a pharmaceutical company focused on developing radiotherapeutics for central nervous system cancers, has announced that the FDA has granted Orphan Drug Designation (ODD) to Rhenium (186Re) Obisbemeda for treating leptomeningeal metastases (LM) in patients with lung cancer. This designation is a significant step in advancing treatments for a particularly challenging condition.

Leptomeningeal metastases occur when a primary cancer spreads to the cerebrospinal fluid and the membranes surrounding the brain and spinal cord. It is a rare but serious complication, with lung cancer, breast cancer, gastrointestinal cancers, and melanoma being among the types of cancer that can lead to LM. While breast cancer sees the highest incidence of LM, lung cancer patients also face a notable risk. LM affects approximately 5% of cancer patients and is generally considered terminal with dismally low survival rates. With no FDA-approved therapies currently available, the condition exacerbates the urgency for new treatment options.

Rhenium (186Re) Obisbemeda, an injectable radiotherapy developed by Plus Therapeutics, offers a promising solution by delivering highly targeted radiation to tumors in the central nervous system. This technology is designed to be safe and effective, potentially surpassing the outcomes of existing treatments by focusing on precision and potency. The radioisotope Rhenium-186 has a short half-life and emits beta energy capable of destroying cancerous tissue, alongside gamma energy useful for imaging. Plus Therapeutics is evaluating Rhenium (186Re) Obisbemeda in clinical trials for recurrent glioblastoma and LM.

The FDA's ODD is awarded to drugs or biologics for treating rare diseases affecting fewer than 200,000 people in the U.S. This designation provides Plus Therapeutics with several benefits, including potential market exclusivity for seven years, tax incentives for clinical trials, and exemptions from specific regulatory fees, including the significant Prescription Drug User Fee Act charge. Mike Rosol, Ph.D., Chief Development Officer of Plus Therapeutics, emphasized the importance of the ODD in paving the way for new treatments to address this under-served patient population.

This development follows the conclusion of the ReSPECT-LM Phase 1 single-dose trial, which established the recommended Phase 2 dose for further study. Plus Therapeutics is now advancing a Phase 2 single-dose expansion trial and a Phase 1 multiple-dose trial. The company is actively working with the FDA to determine the best strategy for pivotal trials, crucial for bringing this new treatment to market.

Plus Therapeutics is committed to advancing its pipeline of targeted radiotherapeutics with the potential to improve outcomes for patients with central nervous system cancers. The company leverages image-guided local beta radiation and targeted drug delivery, focusing on conditions like recurrent glioblastoma and LM. Through strategic partnerships, Plus Therapeutics has established a robust supply chain for the development, manufacturing, and potential commercialization of its products.

In conclusion, the FDA's Orphan Drug Designation for Rhenium (186Re) Obisbemeda marks a pivotal advancement in the treatment of leptomeningeal metastases. It highlights the need for innovative solutions in managing complex cancer cases, offering hope for lung cancer patients facing this challenging complication. As Plus Therapeutics continues to navigate the clinical trial landscape, the potential impact of their work represents a significant milestone in the fight against rare and difficult-to-treat cancers.