ORIGINAL COMMUNICATION MRI outcomes with cladribine tablets for multiple sclerosis in the CLARITY study Giancarlo Comi • Stuart D. Cook • Gavin Giovannoni • Kottil Rammohan • Peter Rieckmann • Per Soelberg Sørensen • Patrick Vermersch • Anthony C. Hamlett • Vissia Viglietta • Steven J. Greenberg Received: 24 July 2012 / Revised: 30 October 2012 / Accepted: 19 November 2012 / Published online: 21 December 2012 Ó Springer-Verlag Berlin Heidelberg 2012 Abstract We herein provide a comprehensive assessment of magnetic resonance imaging (MRI) outcomes from CLARITY, a 96-week, double-blind study demonstrating significant clinical and MRI improvements in patients with relapsing–remitting multiple sclerosis (RRMS) treated with cladribine tablets. Patients with RRMS were randomized 1:1:1 to annual short-course therapy with cladribine tablets cumulative dose 3.5 or 5.25 mg/kg or placebo. MRI end- points included mean number of T1 gadolinium-enhancing (Gd?), active T2 and combined unique (CU) lesions/ patient/scan. MRI-measured disease activity was signifi- cantly reduced in both cladribine tablets groups versus placebo. The proportion of patients with no active lesions at study end was: T1 Gd? lesions: 86.8 and 91.0 versus 48.3 % (p \ 0.001); active T2 lesions: 61.7 and 62.5 ver- sus 28.4 % (p \ 0.001); CU lesions: 59.6 and 60.7 versus 26.1 % (p \ 0.001). Clinically meaningful and significant reductions in active lesion counts and increases in pro- portions of active lesion-free patients were achieved con- sistently in cladribine tablet groups when data were stratified by baseline disease characteristics. For example, the percentage of patients who remained lesion-free over the study was significantly greater in cladribine tablet groups than in the placebo group for all lesion types regardless of relapse category at baseline (p \ 0.001 for all analyses of patients with B1 or 2 relapses; p B 0.022 for analyses of patients with C3 relapses). MRI-measured disease activity was greatly reduced by both doses of cladribine tablets, with consistent effect across clinically relevant patient populations. These findings add to our scientific understanding of the neurological impact of this therapeutic modality in patients with RRMS. On behalf of the CLARITY study group. V. Viglietta and S. J. Greenberg were in Merck Serono S.A., Geneva, Switzerland at the time of manuscript preparation. Electronic supplementary material The online version of this article (doi:10.1007/s00415-012-6775-0) contains supplementary material, which is available to authorized users. G. Comi (&) Department of Neurology and Institute of Experimental Neurology, Scientific Institute H.S. Raffaele, Universita ` Vita-Salute San Raffaele, via Olgettina 60, 20132 Milan, Italy e-mail: comi.giancarlo@hsr.it S. D. Cook New Jersey Medical School, University of Medicine and Dentistry, Newark, NJ, USA G. Giovannoni Blizard Institute of Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, London, UK K. Rammohan Department of Neurology, University of Miami, Miami, FL, USA P. Rieckmann Bamberg Hospital, University of Erlangen, Bamberg, Germany P. S. Sørensen Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark P. Vermersch University of Lille, Nord de France, Lille, France A. C. Hamlett Á V. Viglietta Á S. J. Greenberg Merck Serono S.A., Geneva, Switzerland 123 J Neurol (2013) 260:1136–1146 DOI 10.1007/s00415-012-6775-0