The FDA has approved Enspryng (satralizumab-mwge) for the treatment of neuromyelitis optica spectrum disorder (NMOSD) in adults with a certain antibody — patients who are anti-aquaporin-4 or AQP4 antibody-positive.
NMOSD is a rare autoimmune disease of the central nervous system that mainly affects the optic nerves and spinal cord. Enspryng, made by Genentech, is the third approved treatment for the disorder.
In patients with NMOSD, the immune system mistakenly attacks healthy cells and proteins, most often those in the optic nerves and spinal cord. This typically results in attacks of optic neuritis, which causes eye pain and vision loss. Approximately 50% of patients with NMOSD have permanent visual impairment and paralysis caused by NMOSD attacks. Estimates vary, but NMOSD is thought to affect approximately 4,000 to 8,000 Americans.
NMOSD may be associated with antibodies that bind to a protein called aquaporin-4 (AQP4). Binding of the anti-AQP4 antibody appears to activate other components of the immune system, causing inflammation and damage to the central nervous system, according to the FDA.
The effectiveness and safety of Enspryng for the treatment of NMOSD was demonstrated in two 96-week clinical studies, the agency added. The first study included 95 adults, 64 of whom had antibodies against AQP4 (anti-AQP4 positive). Treatment with Enspryng reduced the number of NMOSD relapses by 74% in patients who were anti-AQP4 positive compared to treatment with a placebo.
The second study included 76 adults, of whom 52 were anti-AQP4 positive. Treatment with Enspryng during this study reduced the number of relapses in patients who were anti-AQP4 positive by 78% compared to treatment with a placebo. There was no evidence of a benefit in patients who were anti-AQP4 antibody negative in either trial.
“Until last year, there were no FDA-approved treatments for patients with this rare, debilitating and sometimes fatal disease. Now there are three,” said Dr. Billy Dunn, director of the Office of Neuroscience in the FDA’s Center for Drug Evaluation and Research, in a news release. “Today’s approval of Enspryng highlights the FDA’s commitment to rapidly advancing safe and effective therapies for NMOSD and other neurological diseases.”
The FDA approved Alexion Pharmaceuticals’ (NSDQ:ALXN) drug Soliris (eculizumab) for the treatment of NMOSD in AQP4 antibody-positive patients in June 2019. In July 2020, the agency approved Uplizna (inebilizumab-cdon), made by Viela Bio (NSDQ:VIE), for the same indication.
Enspryng received fast track designation, which expedites the development and review of drugs that are intended to treat a serious condition and demonstrate the potential to address an unmet medical need. The drug also received orphan drug designation.