The US Food and Drug Administration (FDA) has approved United States-based Alexion Pharmaceuticals' (NASDAQ: ALXN) Soliris intended to treat adults with neuromyelitis optica spectrum disorder (NMOSD), a rare and severe autoimmune disease, who are anti-aquaporin-four antibody positive, it was reported on Friday.

The FDA approval was based on data from the phase three randomised, double-blind and placebo controlled Prevent study. The company has achieved its primary endpoint of prolonging the time to first adjudicated relapse and decreasing the risk of relapse in the Prevent trial. It has treated patients with NMOSD who were anti-AQP4 antibody positive with Soliris or placebo in the study. The effect was noticed through 144 weeks of treatment, with 96% of patients treated with Soliris relapse free, compared to 45% of patients in the placebo arm.

The product is a first-in-class complement inhibitor that works by blocking the C5 protein in the terminal part of the complement cascade, a part of the immune system.