The recommendation of eculizumab to prevent relapses in AQP4-IgG-positive NMOSD is based on the phase-3 trial called “A Randomized Controlled Trial of Eculizumab in AQP4 Antibody-positive Participants With NMO” (PREVENT),14which enrolled 143 adult. The gene discussed is AQP4; the disease is neuromyelitis optica.