Satralizumab, sold under the brand name Enspryng, is a humanized monoclonal antibody medication that is used for the treatment of neuromyelitis optica spectrum disorder (NMOSD), a rare autoimmune disease. The drug is being developed by Chugai Pharmaceutical, a subsidiary of Roche. The most common side effects include the common cold (nasopharyngitis), headache, upper respiratory tract infection, inflammation of the lining of the stomach, rash, joint pain, extremity pain, fatigue and nausea. Satralizumab regulates inflammation by inhibiting the interleukin-6 (IL-6) receptor, a key mediator of the immune response. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication. Medical uses Satralizumab is indicated for the treatment of neuromyelitis optica spectrum disorder (NMOSD) in adults with a particular antibody – people 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. In people 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 people 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. Contraindications Vaccination with live-attenuated or live vaccines is not recommended during treatment and should be administered at least four weeks before starting satralizumab. Side effects 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. The FDA label for satralizumab 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 satralizumab include elevated liver enzymes, decreased neutrophil counts and hypersensitivity reactions. Pharmacology Mechanism of action Satralizumab is a humanized IgG2 monoclonal antibody that binds to soluble and membrane-bound human interleukin-6 (IL-6) receptors and thereby prevents IL-6-mediated signal transmission through these receptors. IL-6 is a pleiotropic cytokine that is produced by a large