Switching from natalizumab to antiCD20 monoclonal antibodies: Short transition interval is associated with improved outcome.

Objective: To investigate the impact of transition interval length when switching from natalizumab (NTZ) to anti-CD20 monoclonal antibodies (antiCD20) on recurrent disease activity and safety in relapsing multiple sclerosis (RMS).

Methods: Aggregating data from 8 MS centres in Austria, Switzerland, and Germany, we included RMS patients who (i) continuously received NTZ for ≥3 months, (ii) were switched to antiCD20, and (iii) had ≥12 months follow-up after switch. The primary endpoint was occurrence of relapse after switch, secondary endpoints included severe infections (CTCAE grade ≥3).

Results: Overall, 139 RMS patients were included (70.5% females, mean age at switch 38.8 years [SD 9.7], mean disease duration at switch 11.3 years [SD 6.2], median duration on NTZ 4.4 years [range: 0.3-16.4], median transition interval 58 days [0-180]). Relapse occurred in 18 patients (12.9%) after NTZ discontinuation. Of those, 11 (61.1%) patients relapsed during the transition interval. No patient with a transition interval below 30 days experienced a relapse, compared to 11.1% and 16.1% with transition intervals of 30-44 days and ≥ 45 days, respectively. In multivariable Cox regression, a transition interval ≥ 45 days predicted a 4.73-fold increased risk of relapse. Over approximately 4 years of follow-up, six severe infections were reported without any noticeable effect of transition interval length. No PML occurred.

Conclusions: Switching from NTZ to antiCD20 is generally both effective and safe. Keeping the transition interval below 30 days provides the optimal balance between preventing recurrent disease activity and ensuring safety.