Natalizumab and drug holiday in clinical practice: An observational study in very active relapsing remitting Multiple Sclerosis patients

Abstract

In order to reduce the risk of progressive multifocal leucoencephalopathy when using natalizumab for more than 12 months, a 6-month drug holiday has been discussed. However, the consequences on short term disease activity have been poorly assessed. The aim of this study was to assess clinical and radiological disease activity within 6 months after stopping natalizumab in very active relapsing remitting Multiple Sclerosis (RRMS) patients. In 8 hospitals from Western France, we retrospectively collected clinical and MRI data from consecutive RRMS patients treated with natalizumab for at least 6 months, and who stopped the drug for various reasons except therapeutic failure. Patients didn't receive any other disease modifying treatment after discontinuing natalizumab. A total of 27 patients with very active RRMS before natalizumab start (mean annualized relapse rate of 2.3, MRI activity in 21 of 27 patients) were studied. Within 6 months after discontinuing natalizumab, 18 patients (67%) experienced clinical relapse and 3 additional patients had radiological activity, without clinical relapse. Four patients (15%) experienced a rebound activity, with severe relapse and 20 or more gadolinium enhancing lesions on MRI. Such observational data didn't support the concept of drug holiday when using natalizumab in very active RRMS.