FDA Approves Treatment for Rare Disease Affecting Optic Nerves, Spinal Cord

The U.S. Food and Drug Administration (FDA) has approved Enspryng (satralizumab-mwge) for the treatment of neuromyelitis optica spectrum disorder (NMOSD) in adults with a particular 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 is the third approved treatment for the disorder.

“Until last year, there were no FDA-approved treatments for patients with this rare, debilitating and sometimes fatal disease. Now there are three,” said Billy Dunn, M.D., director of the Office of Neuroscience in the FDA’s Center for Drug Evaluation and Research. “Today’s approval of Enspryng highlights the FDA’s commitment to rapidly advancing safe and effective therapies for NMOSD and other neurological diseases.”

In patients with NMOSD, the body’s immune system mistakenly attacks healthy cells and proteins in the body, most often those in the optic nerves and spinal cord. Individuals with NMOSD typically have 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 impact approximately 4,000 to 8,000 Americans.

NMOSD can 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.

The effectiveness and safety of Enspryng for the treatment of NMOSD was demonstrated in two 96-week clinical studies. The first study included 95 adult patients; 64 of these patients had antibodies against AQP4 (anti-AQP4 positive). During this study, treatment with Enspryng reduced the number of NMOSD relapses by 74% in patients who were anti-AQP4 positive compared to treatment with a placebo (inactive treatment).

The second study included 76 adult patients; 52 of these patients were anti-AQP4 positive. During the second study, treatment with Enspryng 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.

The prescribing information for Enspryng includes a warning for increased risk of infection, including serious and potentially fatal infections – such as potential reactivation of hepatitis B and tuberculosis. Other warnings and precautions for Enspryng include elevated liver enzymes, decreased neutrophil counts and hypersensitivity reactions. The most common side effects observed were the common cold (nasopharyngitis), headache, upper respiratory tract infection, inflammation of the lining of the stomach, rash, joint pain, extremity pain, fatigue and nausea. Vaccination with live-attenuated or live vaccines is not recommended during treatment and should be administered at least four weeks before starting Enspryng.

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, which provides incentives to assist and encourage drug development for rare diseases.

The FDA is granting the approval to Genentech Inc.