The impact of very short transition times on switching from Natalizumab to Fingolimod on imaging and clinical effectiveness outcomes in multiple sclerosis

Background: Due to the recurrence of disease activity in multiple sclerosis (MS) patients, a washout period of < 3 months has been suggested for the transition from natalizumab (NTZ) to fingolimod (FTY). However, very short transition periods of < 1 month may be more beneficial. Methods: Retrospective analysis of patients from the Rocky Mountain MS Center at the University of Colorado who were: a) on NTZ for 6 months prior to switching to FTY; b) had a transition period <= 6 months; and c) initiated FTY treatment prior to November 2013. Transition periods were grouped as follows: < 1 month, 1-2 months, and 3-6 months. Outcomes assessed include clinical and MRI measures within one year of FTY initiation. Results: Thirty-seven, 56 and 24 patients had a transition period < 1 month, 1-2 months and 3-6 months, respectively. Baseline characteristics were well matched: mean age 45-49 years (p = 0.17), disease duration 11-13 years (p = 0.42), and similar to 70% women (p = 1.00). Following the switch (including transition period), clinical relapses were observed in 0% (< 1 month), 12.5% (1-2 months), 37.5% (3-6 month) (p < 0.001) of patients. New gadolinium enhancing lesions occurred in 3.3% (< 1 month), 13% (1-2 months), 21.4% (3-6 months) (p = 0.13) patients. New T2 lesions were observed in 11.1% (< 1 month), 16.3% (1-2 months), 33.3% (3-6 months) (p = 0.28) of patients. There were no unexpected adverse events or PML observed. Conclusions: Minimizing transition times from NTZ to FTY was beneficial and safe.