Clinical and radiological effectiveness of natalizumab extended dosage interval in patients with relapsing multiple sclerosis
Introduction. Natalizumab (NTZ) is a very effective treatment approved for highly active multiple sclerosis. The main risk of treatment with NTZ is the possibility of developing progressive multifocal leukoencephalopathy, which is related to JC virus positivity and the number of NTZ infusions. This risk decreases with the extended dosage interval (EDI), which involves 9 or fewer infusions/year. However, it is a matter of controversy as to whether EDI remains effective in reducing recurrences and the presence of new lesions in magnetic resonance imaging (MRI).
Patients and methods. A prospective observational study was conducted from 1 April 2019 to 30 June 2021, following up patients on NTZ treatment who switched to EDI. Patients should have at least one MRI six months after the start of EDI. The presence of attacks or MRI activity (new lesions in T2) during the EDI was recorded.
Results. Twenty-three patients with a mean age of 43.5 ± 9.4 years were included. The median number of NTZ infusions was 68 (minimum, 25; maximum, 127). The median interval between the start of the EDI and the last MRI was 14 months (minimum, 6; maximum, 25), and 23 months from the last medical follow-up visit (minimum, 7; maximum, 28). Two patients (8.7%) presented with attacks and two others (8.7%) showed MRI activity.
Conclusions. EDI with NTZ maintains high clinical and activity effectiveness in MRI.
Key words. Extended dosage interval. JC virus. Multiple sclerosis. Natalizumab. Progressive multifocal leukoencephalopathy. Risk management.