The safety and efficacy of ocrelizumab in primary progressive multiple sclerosis were shown in the phase 3 ORATORIO trial. In this study, we assessed the effects of maintaining or switching to ocrelizumab therapy on measures of disease progression and safety in the open-label extension phase of ORATORIO.

ORATORIO was an international, multicentre, double-blind, randomised, placebo-controlled, phase 3 trial done at 182 study locations including academic centres, hospitals, and community speciality centres within 29 countries across the Americas, Australia, Europe, Israel, New Zealand, and Russia. Patients with primary progressive multiple sclerosis aged 18–55 years who had an Expanded Disability Status Scale (EDSS) score of 3·0–6·5 were eligible for enrolment. Those who had previous treatment with B-cell-targeted therapies or other immunosuppressive medications were excluded. Eligible participants were randomly assigned (2:1) to receive either intravenous infusion of 600 mg of ocrelizumab (two 300 mg infusions 14 days apart) or placebo every 24 weeks for at least 120 weeks until a prespecified number (n=253) of disability events occurred. After the double-blind phase, patients entered an extended controlled period of variable duration, during which they and investigators became aware of treatment allocation. Following this period, patients could enter an optional open-label extension, during which they continued ocrelizumab or switched from placebo to ocrelizumab. Time to onset of disability progression was confirmed at 24 weeks with four measures (ie, increase in EDSS score, ≥20% increase in time to complete the 9-Hole Peg Test [9HPT], ≥20% increase in time to perform the Timed 25-Foot Walk [T25FW], and composite progression defined as the first confirmed occurrence of any of these three individual measures), as was time to requiring a wheelchair (EDSS ≥7). Conventional MRI measures were also analysed. The intention-to-treat population was used for the safety and efficacy analyses; all analyses, and their timings, were done post hoc. ORATORIO is registered with ClinicalTrials.gov, NCT01194570, and is ongoing.

From March 3, 2011, to Dec 27, 2012, 488 patients were randomly assigned to the ocrelizumab group and 244 to the placebo group. The extended controlled period started on July 24, 2015, and ended on April 27, 2016, when the last patient entered the open-label extension. Overall, 544 (74%) of 732 participants completed the double-blind period to week 144; 527 (97%) of 544 entered the open-label extension phase, of whom 451 (86%) are ongoing in the open-label extension. After at least 6·5 study years (48 weeks per study year) of follow-up, the proportion of patients with progression on disability measures was lower in those who initiated ocrelizumab early than in those initially receiving placebo for most of the measures of 24-week confirmed disability progression: EDSS, 51·7% vs 64·8% (difference 13·1% [95% CI 4·9–21·3]; p=0·0018); 9HPT, 30·6% vs 43·1% (12·5% [4·1–20·9]); p=0·0035); T25FW, 63·2% vs 70·7% (7·5% [–0·3 to 15·2]; p=0·058); composite progression, 73·2% vs 83·3% (10·1% [3·6–16·6]; p=0·0023); and confirmed time to requiring a wheelchair, 11·5% vs 18·9% (7·4% [0·8–13·9]; p=0·0274). At study end, the percentage change from baseline was lower in those who initiated ocrelizumab early than in those initially receiving placebo for T2 lesion volume (0·45% vs 13·00%, p<0·0001) and T1 hypointense lesion volume (36·68% vs 60·93%, p<0·0001). Over the entire period, in the ORATORIO all ocrelizumab exposure population, the rate of adverse events was 238·09 (95% CI 232·71–243·57) per 100 patient-years and serious adverse events was 12·63 (95% CI 11·41–13·94) per 100 patient-years; the most common serious adverse events were infections at 4·13 (95% CI 3·45–4·91) per 100 patient-years. No new safety signals emerged compared with the double-blind phase of ORATORIO.

Compared with patients switching from placebo, earlier and continuous ocrelizumab treatment provided sustained benefits on measures of disease progression over the 6·5 study years of follow-up. Although this study shows the benefit of earlier intervention with ocrelizumab in primary progressive disease, progression remains an important unmet need in multiple sclerosis. Further research should focus on how the potential benefits described in this study might be improved upon, particularly over longer time periods.

F Hoffmann-La Roche.