Anti-JC Virus (JCV) Antibody Index Differentiates Risk of Progressive Multifocal Leukoencephalopathy (PML) in Natalizumab-Treated Multiple Sclerosis (MS) Patients with No Prior Immunosuppressant (IS) Use: An Updated Analysis (P4.031)

OBJECTIVE: To evaluate associations of anti-JCV antibody index with PML risk in natalizumab-treated MS patients without prior IS use (no-IS patients), using a recent data set. BACKGROUND: PML risk factors include the presence of anti-JCV antibodies, prior IS use, and duration of natalizumab treatment, especially beyond 2 years. In previous analyses of 71 natalizumab-treated PML patients and 2522 non-PML patients, anti-JCV antibody index differentiated PML risk in anti-JCV antibody positive no-IS patients. DESIGN/METHODS: Analyses involved data from clinical studies and postmarketing sources as of March 2014. Predictive probabilities of having an anti-JCV antibody index above/below a range of thresholds were calculated and used to update PML risk estimates for no-IS patients. RESULTS: Data were available for 101 natalizumab-treated PML patients with serum/plasma samples collected 蠅6 months prior to PML diagnosis and 8112 non-PML anti-JCV antibody-positive patients, including 68 and 6745 no-IS patients, respectively. Anti-JCV antibody index was significantly higher in the 68 PML no-IS patients than in the 6745 non-PML no-IS patients ( P 1.5, PML risk was approximately 1.2 per 1000 patients during the first 2 years of natalizumab treatment, 8.8 per 1000 patients from month 25 to 48, and 10.1 per 1000 patients from month 49 to 72. Longitudinal index data will also be presented. CONCLUSIONS: Consistent with previous findings, this updated analysis suggests the anti-JCV antibody index may differentiate PML risk in anti-JCV antibody positive no prior IS patients. Study Supported by: Biogen Idec Disclosure: Dr. Kuesters has received personal compensation for activities with Biogen Idec as an employee. Dr. Plavina has received personal compensation for activities with Biogen Idec as an employee. Dr. Lee has received personal compensation for activities with Biogen Idec as an employee. Dr. Campagnolo has received personal compensation for activities with Biogen Idec as an employee. Dr. Richman has received personal compensation for activities with Biogen Idec as an employee. Dr. Belachew has received personal compensation for activities with Biogen Idec as an employee. Dr. Subramanyam has received personal compensation for activities with Biogen Idec as an employee.