Previous Biogen analyses of the US TOUCH Registry showed that the risk of developing natalizumab-associated progressive multifocal leukoencephalopathy (PML) among anti-JCV antibody positive natalizumab-treated patients was significantly lower with extended interval dosing (EID) compared with standard interval dosing (SID). However, the efficacy of EID was not evaluated in these analyses. Real-world studies and modelling data suggest that a patient population stable on natalizumab SID who is then switched to EID is more likely to maintain efficacy with EID as compared to a population who initiates natalizumab on EID.
The main objective of the study is to evaluate the effectiveness (measured by the annualized relapse rate - ARR) of natalizumab EID in subjects who have been previously treated with natalizumab SID during the 12-month list, in relation to continuous SID treatment.
Observational, open-label study with retrospective analysis of a prospective cohort of patients with relapsing-remitting multiple sclerosis (RRMS) treated at Hospital Ramón y Cajal (Madrid) with natalizumab for 12 months using SID (Infusion every month). All patients were transferred after a period of initial treatment at standard interval doses to a 6-week EID, according to hospital protocol, eliminating a potential selection bias for assigning less active patients to the EID group Demographic, clinical, radiological and immunological variables were collected.
61 patients were included, 33 (54%) women, with a median (range) age at treatment initiation of 35 (17-55) years. Median (range) treatment duration was 5,2 years (2-11,3), 3,47 years (1,4-7,8) in SID, 1,7 years (0,5-4,1) in EID. There was no difference in ARR, mean [95% confidence interval (CI)], (SID: 0.05 [0,01-0,1]; EID: 0.02 [0,02-0,05]; P=0.558), or EDSS (SID: 2,35 [1,9-2,7], EID: 2,67 [2,2-3,9]; p=0,42).
This study does not demonstrate significant differences in relapse outcomes between SID and EID periods of patients who switched to EID from natalizumab after ≥1 year on SID. These results are consistent with previous analyzes without comparison that concluded that efficacy is maintained after switching to EID. Consistent MRI and EDSS results will be shown in the final poster. An ongoing prospective randomized trial of EID versus SID will provide a more complete understanding of the effectiveness of natalizumab EID.