Natalizumab (manufactured by Biogen Idec as Tysabri; previously named Antegren) is a humanized monoclonal antibody approved by the U.S. Food and Drug Administration (FDA) as a monotherapy for the treatment relapsing-remitting forms of multiple sclerosis (MS), and of Crohn’s disease. Administered as an intravenous injection, the drug is believed to reduce or inhibit the ability of immune cells to invade the blood-brain barrier, protecting against autoimmune attacks by the body’s innate immune system to slow the worsening of symptoms and number of disease flares.
Tysabri is also approved as a disease-modifying monotherapy in the European Union (since 2006) for relapsing MS patients with high disease activity (two or more lesions in one year) despite treatment with a β-interferon or glatiramer acetate, and for those with rapidly evolving severe RRMS.
History of Tysabri
Natalizumab was approved by the FDA in 2004 for the treatment of relapsing and remitting forms of the disease, but the therapy came under strict scrutiny after cases of progressive multifocal leukoadenopathy (PML, a rare brain infection) were reported in patients prescribed the therapy. This led to its FDA suspension in 2005, followed by its return in 2006, because of its effectiveness, under a strict risk-management program and PML warning label. Those most at risk of developing PML are people with weakened immune systems (through medications of diseases like HIV), those previously infected with JCV (John Cunningham virus), and long-term Tysabri users (typically, two or more years). Tysabri is available only through a restricted distribution plan called the TOUCH Prescribing Program.
How Tysabri Works
The drug’s mode of action involves inhibition of the alpha-4 integrin (α4 Integrin), which is a transmembrane receptor meant for adhesion of cells to the extracellular matrix as well as conduction of signals from cell to cell, aiding in vital functions like growth, division, activation, and proliferation of the same. By virtue of this, Tysabri successfully inhibits attachment of immune cells to the extracellular boundaries and linings of the blood-brain barrier, and reduces inflammation in MS patients.
Common side effects of the drug include headache, urinary tract infection, lung infection, joint pain, pain in your arms and legs, vaginitis, stomach discomfort, tiredness, depression, diarrhea, rash, and nausea. The standard recommended dosage is 300 mg intravenous infusion, administered by a healthcare professional and taking about one hour, every 28 days.
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