• biomarker;
  • fingolimod;
  • multiple sclerosis;
  • natalizumab saturation;
  • treatment holiday


More and more patients with multiple sclerosis (MS) switch from natalizumab to fingolimod because of the risk of progressive multifocal leukoencephalopathy. The duration of the treatment holiday is still under debate referring to a possible recurrence of disease activity.

Aim of the study

The aim of this study was to evaluate the prognostic value of natalizumab saturation on T cells for the recurrence of clinical and radiological disease activity.


Cell surface-bound natalizumab saturation (in%) of CD8+ and CD4+ T cells from five patients with MS was determined before initiation of fingolimod by flow cytometry and related to clinical and MRI outcome during a 6-month follow-up.


In two patients with either clinical or radiological disease activity, the natalizumab saturation on CD8+ and CD4+ T cells was <30%. In contrast, the remaining three patients with absence of disease activity had a median natalizumab saturation of 70% (range 59–79%) on CD4+ and 66% (range 52–68%) on CD8+ T cells.


The data of this pilot study indicate that clinical and radiological disease activity is closely linked to natalizumab saturation at the time point of switch. The determination of natalizumab saturation may be an essential tool to monitor cessation of natalizumab treatment.