Satralizumab: an interleukin-6 (IL-6) receptor antagonist for the treatment of neuromyelitis optica spectrum disorders.

Neuromyelitis optica spectrum disorders (NMOSD) consist of a rare autoimmune disorder in which patients suffer from relapses that affect the optic nerve, spinal cord or brainstem. Few have a full recovery. NMOSD is more common in women, the age of onset being around 30-40 years of age depending on race. The prevalence of the condition varies from 0.5-4.4 per 100,000 population. About 80% of patients have antibodies directed against the aquaporin-4 (AQP4) protein that form membrane-bound water transporters in the central nervous system (CNS). This protein is highly expressed in those areas of the CNS often targeted in NMOSD relapses. Satralizumab is a humanized monoclonal antibody that binds to the interleukin-6 (IL-6) receptor and thus inhibits IL-6 signaling. Two recent phase III studies have demonstrated that satralizumab significantly reduced the relapse rate in NMOSD by 76-79%. This beneficial effect was apparently confined to patients who have anti-AQP4 antibodies and satralizumab did not reduce the rate of pain or fatigue in NMOSD patients.