Plus Therapeutics Expands Reimbursement for CNSide® CSF Assay to 75 Million Covered Lives

New agreement with Highmark, a leading Blue Cross Blue Shield-affiliated payer, marks milestone in expanding patient access to the diagnostic test.

Apr. 2, 2026 at 12:03pm

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Plus Therapeutics, Inc. announced a new payer coverage agreement with Highmark, effective April 1, 2026, providing reimbursement for its CNSide® Cerebrospinal Fluid (CSF) Tumor Cell Enumeration (TCE) assay for patients with metastatic central nervous system cancers. The addition of Highmark expands CNSide's total covered lives from approximately 67 million to 75 million, representing continued progress toward the company's 2026 objective of 150 million covered lives and expanding patient access across the U.S.

Why it matters

Securing coverage with Highmark, a major Blue Cross Blue Shield-affiliated payer, is an important milestone in improving access to CNSide, a diagnostic test that enables earlier and more accurate detection of leptomeningeal metastases compared to standard CSF cytology. Expanding reimbursement coverage helps reduce barriers for ordering physicians and accelerates adoption of the test across oncology centers.

The details

The CNSide® CSF Assay Platform has demonstrated superior clinical utility over standard of care in 9 peer-reviewed publications, the FORESEE clinical trial, and real-world practice. Earlier detection enabled by CNSide has been shown to reduce overall leptomeningeal metastases-related healthcare costs by ~40% through earlier diagnosis and treatment optimization. Since its commercial launch in 2020, more than 11,000 CNSide tests have been performed at over 120 U.S. cancer institutions, delivering high sensitivity (92%) and specificity (95%), while influencing treatment decisions in 90% of cases.

  • The new coverage agreement with Highmark is effective as of April 1, 2026.
  • CNSide was commercially launched in 2020.

The players

Plus Therapeutics, Inc.

A clinical-stage pharmaceutical company developing targeted radiotherapeutics for difficult-to-treat cancers of the central nervous system.

CNSide Diagnostics, LLC

A wholly-owned subsidiary of Plus Therapeutics that develops and commercializes the CNSide® CSF Assay Platform.

Highmark

An independent licensee of the Blue Cross Blue Shield Association and one of the largest Blue Cross Blue Shield-affiliated organizations in the country with nearly 8 million members nationwide.

Russ Havranek

Executive Vice President of Corporate and Commercial Strategy at Plus Therapeutics.

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What they’re saying

“Securing coverage with Highmark, a leading Blue Cross Blue Shield-affiliated payer, marks another important milestone in expanding patient access to CNSide and reinforces the growing recognition among payers of its clinical and economic value.”

— Russ Havranek, EVP Corporate and Commercial Strategy

What’s next

Plus Therapeutics is continuing to work towards its goal of achieving 150 million covered lives for the CNSide® CSF Assay by 2026.

The takeaway

The expanded reimbursement coverage for the CNSide® CSF Assay through the Highmark agreement will help improve access to this innovative diagnostic test that can enable earlier detection and treatment of leptomeningeal metastases, potentially reducing overall healthcare costs.