Incidence of natalizumab-associated progressive multifocal leucoencephalopathy and its relationship with the pattern of natalizumab exposure over time

Abstract

Introduction Since the 2012 identification of 3 risk factors for natalizumab-associated progressive multifocal leucoencephalopathy (PML) changes in the PML incidence rate have been of interest. Objectives Determine the natalizumab-associated PML incidence in the global postmarketing setting since introduction of the anti-JCV antibody assay and evaluate the relationship of PML incidence with natalizumab exposure. Patients and methods The incidence of confirmed PML cases in Biogen's global safety database from 2009 to 2017 was evaluated retrospectively. Overall incidence in all exposed patients was determined by the estimated total number of patients ever exposed to natalizumab and the number of confirmed PML cases. Changes in natalizumab exposure patterns over time were evaluated by 12-infusion epochs. Results As of 30 November 2017, 180,656 patients worldwide had received ≥ 1 natalizumab dose (total exposure: 625,451 patient-years); overall natalizumab-associated PML incidence was 4.19/1000 patients. The increase in overall monthly incidence reported from 2012 onward appears to level off in mid-2016; overall incidence remained between 4.18–4.24/1000 over the last 21 months. Discussion NA. Conclusion Overall PML incidence has been stable since mid-2016. This stabilisation coincides with the introduction and publication of the new PML risk algorithm.