The results of a recent comparative effectiveness study did not show rituximab to be less effective than ocrelizumab in the risk of disability in the treatment of multiple sclerosis. However, rituximab was linked to a higher risk of relapses than ocrelizumab. 

Ocrelizumab, a humanized monoclonal antibody targeted against CD20+B cells, reduces the frequency of relapses by 46 percent and disability worsening by 40 percent when compared with interferon beta 1a in relapsing MS. Rituximab, a chimeric monoclonal anti-CD20 agent, is often prescribed as an off-label alternative to ocrelizumab. An international team of researchers, led by scientists at the Neuroimmunology Centre, Royal Melbourne Hospital, Melbourne, Victoria, Australia, set out to evaluate whether rituximab is unacceptably less clinically effective when compared with ocrelizumab in relapsing MS. 

The study was conducted between January 2015 and March 2021. Patients were recruited from the MS Base registry and Danish MS Registry. Patients had a history of relapsing MS treated with ocrelizumab or rituximab, a minimum six months of follow-up, and sufficient data to calculate the propensity score. Patients with comparable baseline characteristics were 1:6 matched with propensity score on age, sex, MS duration, disability (Expanded Disability Status Scale), prior relapse rate, prior therapy, disease activity (relapses, disability accumulation, or both), MRI lesion burden (missing values imputed), and country. 

Effectiveness comparison of annualized rate of relapses, with a prespecified effectiveness margin of 1.63 rate ratio. Secondary endpoints were relapse and six-month confirmed disability accumulation in pairwise-censored groups. 

A total of 710 patients treated with ocrelizumab were matched with 186 patients treated with rituximab. Over a pairwise censored mean follow-up of 1.4 years, the ARR ratio was higher in patients treated with rituximab than in those treated with ocrelizumab. The cumulative hazard of relapses was higher among patients treated with rituximab than those treated with ocrelizumab. No difference in the risk of disability accumulation was observed between groups. Results were confirmed insensitivity analyses. 

The efficacy of rituximab and ocrelizumab administered at uniform doses and intervals is being further evaluated in randomized effectiveness clinical trials.

According to MS Focus Senior Medical Advisor Dr. Ben Thrower, “An important class of medications for managing MS is the B-cell therapies. These include ocrelizumab (Ocrevus), ofatumumab ( Kesimpta), rituximab (Rituxan, Truxima Ruxience) and ublituximab (Briumvi). All of these therapies are anti-CD20 monoclonal antibodies. This study took a retrospective look at how people living with MS did on Ocrevus as compared to rituximab. While this is valuable information, this type of retrospective study is not the same as a prospective, controlled trial. With that caveat, this trial found that those treated with Ocrevus had fewer relapses than those treated with rituximab. 

“There was no difference in disability progression between the two groups. Both of these therapies are typically given intravenously every six months. There is a cost difference between the two with rituximab being less expensive. Some health insurance carriers, Kaiser for example, prefer that rituximab be used and typically will not cover Ocrevus. People living with MS should discuss the risks and benefits of any therapy, including B-cell therapies, with their healthcare team.”

The findings were published in the journal JAMA Neurology.