HOUSTON, December 11, 2025 — Plus Therapeutics announced that its subsidiary CNSide Diagnostics, LLC has secured new state laboratory licenses in California, Rhode Island, and Maryland, expanding access to the CNSide® Cerebrospinal Fluid (CSF) Tumor Cell Enumeration (TCE) Assay to 48 U.S. states, covering more than 90% of the U.S. population. This expansion strengthens the availability of a high-precision diagnostic test designed to support earlier detection, treatment guidance, and monitoring of leptomeningeal metastases (LM) and other central nervous system cancers.
Science Significance
Scientifically, the expansion underscores the growing role of CSF-based tumor cell analytics in transforming LM diagnosis and management. The CNSide® assay platform, validated across more than 11,000 clinical tests and 120 cancer institutions, delivers 92% sensitivity and 95% specificity, significantly outperforming conventional cytology. The platform’s ability to influence treatment decisions in 90% of clinical cases demonstrates the scientific strength of its quantitative methodologies, which enable real-time insights into tumor burden, therapeutic response, and central nervous system disease progression. The assay’s integration into clinical workflows supports precision oncology by providing clinicians with actionable, high-resolution diagnostic data for a condition that remains one of the most challenging complications of advanced cancers.
Regulatory Significance
Regulatorily, the acquisition of state licenses—especially in a strict environment like California—signals the assay’s strong alignment with state and federal requirements for Laboratory Developed Tests (LDTs) under CLIA and evolving regulatory expectations. State licensure expands CNSide Diagnostics’ ability to deliver a compliant, nationally accessible testing service, supporting broader uptake in oncology networks. As federal oversight of LDTs continues to tighten, CNSide’s regulatory readiness across nearly all U.S. jurisdictions places the company in a favorable position for future compliance demands. The milestone bolsters the company’s infrastructure for clinical testing while ensuring that high-complexity diagnostics can be delivered with consistency, accuracy, and regulatory reliability.
Business Significance
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Commercially, the expansion strengthens Plus Therapeutics’ market positioning in both CNS oncology diagnostics and its broader targeted radiotherapeutics strategy. New licensure enables the company to increase test volume, expand payor coverage, and support national commercialization efforts, laying groundwork for future reimbursement negotiations. With LM cases rising alongside cancer incidence, demand for clinically validated diagnostic tools is increasing, and CNSide’s expanded footprint positions Plus Therapeutics to capture greater market share. The licensure milestone also enhances the company’s competitive leverage as it advances radiotherapeutic candidates for LM and recurrent glioblastoma, creating an integrated diagnostic-plus-therapeutic ecosystem unique within the neuro-oncology sector.
Patients’ Significance
For patients with leptomeningeal metastases—a rapidly progressive, life-threatening condition—timely access to high-sensitivity diagnostic tools is critical. The CNSide® assay offers earlier detection, more reliable monitoring, and greater precision in treatment selection, addressing many of the gaps associated with traditional diagnostic methods. Expanded state access ensures that more patients can benefit from testing without delays caused by geographic or regulatory limitations. By enabling clinicians to track tumor cell dynamics and adjust treatment strategies accordingly, CNSide® improves the potential for better disease management, reduced diagnostic ambiguity, and a clearer therapeutic pathway for patients living with aggressive CNS cancers.
Policy Significance
At the policy level, CNSide’s nationwide expansion highlights the urgent need to support equitable access to advanced oncology diagnostics across state lines. As cancer mortality is increasingly impacted by diagnostic delays, policymakers are shifting focus toward frameworks that expand availability of validated LDTs, ensure consistent reimbursement, and integrate precision testing into standard oncology care. CNSide’s growth into nearly every U.S. state aligns with national priorities to improve cancer detection infrastructure and strengthens policy momentum toward broader genomic and cytologic testing integration. This milestone also demonstrates how coordinated regulatory and commercial strategies can help overcome barriers that traditionally limit access to critical diagnostic technologies.
The expansion of CNSide® into California, Rhode Island, and Maryland marks a pivotal advancement in national access to high-precision CNS cancer diagnostics. With testing now available to the vast majority of the U.S. population, Plus Therapeutics is strengthening the scientific, regulatory, and clinical foundation required to support earlier LM detection and more informed treatment strategies. As the company advances both diagnostics and radiotherapeutics, CNSide® stands poised to play an increasingly central role in shaping the future of neuro-oncology care.
Source: Plus Therapeutics press release
