Safety and efficacy of natalizumab in Belgian multiple sclerosis patients: subgroup analysis of the natalizumab observational program

Vincent van Pesch, Emmanuel Bartholomé, Véronique Bissay, Olivier Bouquiaux, Michel Bureau, Jo Caekebeke, Jan Debruyne, Inge Declercq, Dany Decoo, Pierre Denayer, Eric De Smet, Marie D'hooghe, Bénédicte Dubois, Michel Dupuis, Souraya El Sankari, Karine Geens, Daniel Guillaume, William van Landegem, Andreas Lysandropoulos, Alain Maertens de NoordhoutRobert Medaer, Annick Melin, Katelijne Peeters, Rémy Phan Ba, Cécile Retif, Pierrette Seeldrayers, Anoek Symons, Etienne Urbain, Patrick Vanderdonckt, Erwin Van Ingelghem, Ludo Vanopdenbosch, Erwin Vanroose, Bart Van Wijmeersch, Barbara Willekens, Christiana Willems, Christian Sindic

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Natalizumab (Tysabri(®)) is highly efficacious in controlling disease activity in relapsing multiple sclerosis (MS) patients. As it is one of the more recent therapies for MS, there remains a need for long-term safety and efficacy data of natalizumab in a clinical practice setting. The Tysabri observational program (TOP) is an open-label, multicenter, multinational, prospective observational study, aiming to recruit up to 6,000 patients with relapsing-remitting MS from Europe, Canada and Australia. The objectives of this study are to collect long-term safety and efficacy data on disease activity and disability progression. We report here the interim results of the 563 patients included in TOP between December 2007 and 2012 from Belgium. This patient cohort was older at baseline, had longer disease duration, higher neurological impairment, and a higher baseline annualized relapse rate, when compared to patients included in the pivotal phase III AFFIRM trial. Nevertheless, the efficacy of natalizumab was comparable. The annualized relapse rate on treatment was reduced by 90.70 % (p < 0.0001) with a cumulative probability of relapse of 26.87 % at 24 months. The cumulative probabilities of sustained disability improvement and progression at 24 months were 25.68 and 9.01 %, respectively. There were no new safety concerns over the follow-up period. Two cases of progressive multifocal leukoencephalopathy were diagnosed. Our results are consistent with other observational studies in the post-marketing setting.

Original languageEnglish
Pages (from-to)167-178
Number of pages12
JournalActa Neurologica Belgica
Issue number3
Publication statusPublished - Sep 2014


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