Neuromyelitis optica spectrum disorder (NMOSD) is a rare and debilitating 
autoimmune astrocytopathy with a predominantly relapsing disease course. 
Satralizumab, a humanized monoclonal antibody, was designed to treat NMOSD by 
targeting the IL-6 receptor. Satralizumab builds on positive experiences of 
off-label use tocilizumab in recent years. Before 2019, no medications were 
approved for the treatment of NMOSD. In 2020, satralizumab became the third 
compound to enter the US market, adding to the complement inhibitor eculizumab 
and the CD19 inhibitor inebilizumab. Here, we review the two randomized, 
double-blind, Phase III trials that investigated the subcutaneous administration 
of satralizumab as add-on treatment and monotherapy. Both studies revealed 
positive effects concerning the reduction of relapse risk for AQP4 seropositive 
NMOSD patients and generally good tolerability.