Long-term management of natalizumab discontinuation in a large monocentric cohort of multiple sclerosis patients

Background Pivotal and post-marketing studies demonstrated the impressive efficacy and the good tolerability profile of natalizumab in Multiple Sclerosis patients. On the other hand long-term safety of natalizumab therapy is burdened by the risk of progressive multifocal leukoencephalopathy, especially in anti-JCV seropositive patients treated for more than two years. Some of these patients must stop the drug at the risk of disease reactivation. Objectives To evaluate the effects of natalizumab discontinuation in a monocentric cohort of multiple sclerosis patients followed for a mean time of 22.4 months. Methods One hundred and ten patients, who stopped therapy after at least 12 infusions, were followed with periodic clinical and magnetic resonance imaging evaluations. One hundred patients started either immunomodulant therapy (n=90) or fingolimod (n=10) while 10 remained without any drug. Results "Disease-activity free" patients were 25% at one year after discontinuation and annualized relapse rate significantly increased from 0.06 to 0.84 (p<0.0001). We found that the risk of reactivation peaked despite alternative treatments between the second and the eighth month after suspension, a so-called "high risk period". During this period the majority of patients showed a return to pre-natalizumab disease activity while 10% of patients presented a "rebound activity". A higher pre-natalizumab disease activity was correlated with an increased risk of reactivation (p=0.004). Conclusions Our data suggest that disease reactivation peaked during a "high risk period" between the second and the eighth month since stopping the drug. During this period no alternative treatments seemed to provide an adequate protection from disease reactivation. Though transient, this phase could be potentially dangerous, therefore we need to develop more effective strategies to deal with this challenge.