Approach to JCV testing with natalizumab biosimilar: a UK consensus statement.

Area of Science:

• Neurology
• Immunology
• Pharmacology

Background:

• Biosimilars offer potential cost savings and improved access to treatments like natalizumab for multiple sclerosis.
• JC virus (JCV) serostatus testing is crucial for stratifying progressive multifocal leukoencephalopathy (PML) risk in patients on natalizumab.
• Current risk stratification relies on the Stratify assay, but the Immunowell assay is used with the biosimilar natalizumab, Tyruko.

Purpose of the Study:

• To evaluate the concordance of JCV serostatus results between the Immunowell and Stratify assays.
• To assess the implications of discordant results on PML risk classification and patient management.
• To provide guidance for managing patients with differing JCV test results.

Main Methods:

• Comparison of JCV serostatus results obtained from the Immunowell and Stratify assays.
• Analysis of discordant results, particularly around PML risk thresholds.
• Evaluation of the clinical implications for patient monitoring and treatment decisions.

Main Results:

• The Immunowell assay appears more likely to yield a positive JCV index compared to the Stratify test.
• Negative results show high agreement between Immunowell and Stratify, supporting a rational safety strategy.
• Discordant results pose a risk of misclassifying patients regarding PML risk.

Conclusions:

• Inconsistent JCV testing results can lead to inappropriate PML risk assessment, potentially denying effective natalizumab therapy or causing unnecessary monitoring.
• Guidance is needed to manage discordant results, balancing safety with patient access to treatment and minimizing healthcare burdens.
• Harmonizing JCV testing or establishing clear protocols for discordant results is essential for optimal patient care in multiple sclerosis treatment.