*March 2025*
The FDA has granted orphan drug designation to the investigational radiotherapeutic rhenium (186Re) obisbemeda as a potential therapeutic option for leptomeningeal metastases in patients with lung cancer.1
Rhenium (186Re) obisbemeda is formulated to deliver highly targeted, high-dose radiation directly to central nervous system (CNS) tumors with the goal of optimizing safety and efficacy via a more potent and localized radiation dose compared with currently available treatments.
“Receiving orphan drug designation for rhenium (186Re) obisbemeda marks a significant milestone in our efforts to develop a much-needed therapy for [patients with] lung cancer with leptomeningeal metastases,” Mike Rosol, PhD,, chief development officer of Plus Therapeutics, stated in a news release. “These patients currently have limited treatment options, and the growing incidence of leptomeningeal metastases in lung cancer underscores the urgency for new therapies. This designation, in combination with our previously granted fast track designation, strengthens our pathway toward delivering an innovative, targeted radiotherapeutic solution for this highly underserved patient population.”
The phase 1 ReSPECT-LM clinical trial (NCT05034497) evaluated rhenium (186Re) obisbemeda in patients with LM and established the recommended phase 2 dose (RP2D). After enrollment was completed for cohort 6, which evaluated that agent at a dose of 75.0 mCi, the cohort 4 dose of 44.1 mCi was determined to be the RP2D; no dose-limiting toxicities were observed at this dose level.2
One patient treated at the cohort 4 dose achieved a complete response, as evidenced by the eradication of tumor cells in the cerebrospinal fluid—a key therapeutic end point.
The company is advancing a phase 2 single-dose expansion trial and a phase 1 multiple-dose trial to further assess the agent’s safety and therapeutic potential.1 Additionally, ongoing discussions with the FDA aim to define the optimal design for a pivotal registration trial.
Rhenium (186Re) obisbemeda is also being evaluated for the treatment of patients with recurrent glioblastoma in the phase 1/2 ReSPECT-GBM trial (NCT01906385). Read more.
