A Targeted Strike Against a Hidden Cancer Foe

HOUSTON, TX – December 01, 2025 – In the relentless war against cancer, some battlefields are more treacherous than others. One of the most formidable is the central nervous system, where a devastating complication known as leptomeningeal metastases (LM) has long been considered a virtual death sentence. Now, a Houston-based clinical-stage company, Plus Therapeutics, is preparing to present data on a novel weapon that could change the calculus of this fight, offering a glimmer of hope against one of oncology’s most desperate challenges.

This month, at the prestigious San Antonio Breast Cancer Symposium, the company will unveil Phase 1 results for its investigational radiotherapeutic, REYOBIQ™. The presentation focuses on the drug's potential to treat LM, a condition where cancer cells invade the delicate membranes and cerebrospinal fluid (CSF) surrounding the brain and spinal cord. While the announcement of early-stage clinical data is a routine event in the biotech world, this one carries exceptional weight, addressing a dire unmet need with a highly innovative approach that goes far beyond a simple new drug.

The Unseen Enemy in the Central Nervous System

For the approximately 110,000 patients diagnosed with leptomeningeal metastases in the U.S. each year, the outlook is grim. Occurring in about 5% of patients with advanced solid tumors—most commonly from breast cancer, lung cancer, and melanoma—LM represents a catastrophic progression of the disease. The cancer cells, having broken away from their primary site, create a diffuse, sheet-like coating within the central nervous system, leading to a cascade of debilitating neurological symptoms.

The prognosis is heartbreakingly short. Median survival is typically measured in months, often just two to six, even with treatment. The primary challenge is the body's own defense: the blood-brain barrier, an elegant biological gatekeeper that protects the brain from toxins but also blocks most systemic chemotherapies from reaching the cancerous cells in the CSF.

Current treatments, such as whole-brain radiation or chemotherapy delivered directly into the spinal fluid via an implanted port, are often of limited efficacy and can carry significant toxicities. "It's an incredibly difficult disease to treat," noted one neuro-oncology researcher not affiliated with the company. "You're fighting a moving, widespread target in the most sensitive real estate in the human body. We desperately need smarter, more targeted therapies."

A Precision Radiotherapy 'Nanoliposome'

This is the void Plus Therapeutics aims to fill with REYOBIQ™. The therapy is not a conventional drug but a targeted radiopharmaceutical. It consists of a nanoliposome—a microscopic fat bubble—that encapsulates a powerful radioisotope, Rhenium-186. This formulation is designed to be injected directly into the cerebrospinal fluid, bypassing the blood-brain barrier entirely.

Once in the CSF, the nanoliposomes are absorbed by the cancer cells, delivering a highly localized, potent dose of beta-particle radiation. The properties of Rhenium-186 are key to this strategy: its beta radiation is powerful enough to destroy cancer cells over a short distance, minimizing damage to surrounding healthy brain and spinal tissue. Crucially, it also emits a low level of gamma radiation, which allows clinicians to use standard SPECT imaging to see exactly where the drug is distributed in real-time, confirming it has reached its target.

The potential of this approach has already been demonstrated in another difficult-to-treat brain cancer. In a Phase 1 trial for recurrent glioblastoma, REYOBIQ™ more than doubled the median overall survival compared to the standard of care, with no dose-limiting toxicities observed. This prior success provides a strong foundation of evidence for its application in LM, a disease that shares the same challenging anatomical location.

A Strategic Play Fueled by Validation

For a clinical-stage company like Plus Therapeutics, navigating the high-risk, high-reward world of biotech requires more than just promising science; it demands a sound strategy. The advancement of the ReSPECT-LM trial is a cornerstone of the company’s focus on dominating a niche but critical area of oncology. While the company's stock has faced the volatility typical of the sector, including a recent Nasdaq compliance warning over its minimum bid price, its scientific strategy has garnered significant external validation.

The ReSPECT-LM trial itself is funded by a substantial $17.6 million grant from the Cancer Prevention & Research Institute of Texas (CPRIT). This is not an isolated vote of confidence. The company’s glioblastoma program is supported by the National Cancer Institute (NCI), and its upcoming trial in pediatric brain cancer has received a $3 million grant from the Department of Defense. This non-dilutive funding from prestigious, peer-reviewed institutions provides a critical financial runway and, more importantly, serves as a powerful endorsement of the underlying technology.

This strategic funding allows the company to pursue these high-need, high-impact indications without solely relying on the often-fickle equity markets, building a robust pipeline centered on CNS cancers where its platform has a distinct mechanistic advantage.

The Power of Synergy: Seeing the Target to Treat the Target

Perhaps the most forward-looking aspect of Plus Therapeutics' strategy is its integration of diagnostics and therapeutics. Through its wholly-owned subsidiary, CNSide Diagnostics, the company has developed a highly sensitive assay platform that can detect and quantify cancer cells in the cerebrospinal fluid with unprecedented accuracy.

The CNSide® test goes beyond a simple "yes" or "no." It can characterize the captured cells, identifying genetic markers that could guide personalized treatment. For clinicians managing LM, this is a game-changer. It offers a way to confirm a diagnosis, monitor a patient's response to therapy with a simple CSF sample, and make informed decisions about the next steps.

The diagnostic's clinical utility was recently validated commercially through a major coverage agreement with UnitedHealthcare, giving over 51 million people access to the test. This creates a powerful synergy: as CNSide becomes the standard for diagnosing and monitoring LM, it simultaneously builds the very ecosystem in which a targeted therapeutic like REYOBIQ™ can be most effectively deployed. By being able to precisely identify and track the disease, the company can better demonstrate the value and efficacy of its treatment.

As the oncology community gathers in San Antonio, the data presented by Dr. Andrew Brenner will be scrutinized for signs of safety and efficacy. But beyond the numbers, the story of REYOBIQ™ is a compelling case study in modern therapeutic development. It is an attack on a disease long considered untouchable, powered by elegant science and underpinned by a shrewd strategy that combines diagnostics, therapeutics, and a laser focus on solving one of medicine’s most intractable problems.