Even though the market for relapsing MS drugs is now quite crowded—with products that have differing immunosuppressive mechanisms and varying risk–benefit profiles—Ocrevus has attracted multi-billion-dollar forecasts on the strength of its efficacy and its apparently favorable safety profile. As with any new MS therapy, it will take several years of follow-up study in a large patient population before a fuller understanding of its safety profile will emerge. But for now, Ocrevus is the only approved drug to treat MS by targeting CD20, a mechanism long used for treating other autoimmune conditions, such as rheumatoid arthritis, and B-cell malignancies.
In MS, the new era has been a long time coming. More than a decade ago, a group led by Stephen Hauser at the University of California, San Francisco, found that Genentech's Rituxan (rituximab), a chimeric anti-CD20 antibody first approved in 1997 for treating non-Hodgkin's lymphoma and approved in 2006 for treating rheumatoid arthritis, also had dramatic effects in a phase 2 trial in MS. Shortly afterwards, Basel, Switzerland–based Roche became the outright owner of Genentech and terminated the program in favor of a newer, humanized successor with a longer patent life (Mult. Scler. 21, 8–21, 2015). Off-label use of Rituxan in MS treatment has continued, particularly in Sweden, where the drug has delivered on its initial promise, even if the supporting evidence base (Neurology 87, 2074–2081, 2016) is at this point much thinner than that underpinning Ocrevus, which has completed a comprehensive development program.
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