Onset of clinical and MRI efficacy of ocrelizumab in relapsing multiple sclerosis

Abstract

ObjectiveTo assess the onset of ocrelizumab efficacy on brain MRI measures of disease activity in the phase II study in relapsing-remitting multiple sclerosis (RRMS), and relapse rate in the pooled phase III studies in relapsing multiple sclerosis (RMS).MethodsBrain MRI activity was determined in the phase II trial at monthly intervals in patients with RRMS receiving placebo, ocrelizumab (600 mg), or intramuscular interferon (IFN) β-1a (30 μg). Annualized relapse rate (ARR; over various epochs) and time to first relapse were analyzed in the pooled population of the phase III OPERA (A Study of Ocrelizumab in Comparison With Interferon Beta-1a [Rebif] in Participants With Relapsing Multiple Sclerosis) I and OPERA II trials in patients with RMS receiving ocrelizumab (600 mg) or subcutaneous IFN-β-1a (44 μg).ResultsIn patients with RRMS, ocrelizumab reduced the number of new T1 gadolinium-enhancing lesions by week 4 vs placebo (p = 0.042) and by week 8 vs intramuscular IFN-β-1a (p < 0.001). Ocrelizumab also reduced the number of new or enlarging T2 lesions appearing between weeks 4 and 8 vs both placebo and IFN-β-1a (both p < 0.001). In patients with RMS, ocrelizumab significantly reduced ARR (p = 0.005) and the probability of time to first protocol-defined relapse (p = 0.014) vs subcutaneous IFN-β-1a within the first 8 weeks.ConclusionEpoch analysis of MRI-measured lesion activity in the phase II study and relapse rate in the phase III studies consistently revealed a rapid suppression of acute MRI and clinical disease activity following treatment initiation with ocrelizumab in patients with RRMS and RMS, respectively.Classification of evidenceThis study provides Class II evidence that for patients with RRMS and RMS, ocrelizumab suppressed MRI activity within 4 weeks and clinical disease activity within 8 weeks.