The FDA’s go-ahead for Roche Holding AG’s Enspryng (satralizumab-mwge) in anti-aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder had watchers of the space weighing its market odds against two therapies approved earlier: Soliris (eculizumab) from Boston-based Alexion Pharmaceuticals Inc., and the more recently cleared Uplizna (inebilizumab-cdon) from Viela Bio Inc., of Gaithersburg, Md.

Days after going public, Viela Bio Inc. nailed down a deal with Mitsubishi Tanabe Pharma Corp. to develop and commercialize Viela's humanized anti-CD19 monoclonal antibody, inebilizumab, in nine Asia regions for the rare disease called neuromyelitis optica spectrum disorder (NMOSD), as well as other potential future indications.

Approval of Alexion Pharmaceutical Inc.'s Soliris (eculizumab) injection to treat neuromyelitis optica spectrum disorder (NMOSD) in adult patients who are anti-aquaporin-4 (AQP4) antibody positive makes it the first and only FDA-approved treatment. It's also one of the most expensive treatments in the world, making it vulnerable to off-label use and the eventual creep of biosimilars into the market.