Natalizumab binds to the a4-subunit of a4b1 and a4b7 integrins expressed on the surface of all leukocytes except neutrophils, and inhibits the a4-mediated adhesion of leukocytes to their counter-receptor(s). See package insert for complete information.

TYSABRI is an integrin receptor antagonist indicated for the treatment of: Multiple Sclerosis (MS):
•As monotherapy for the treatment of patients with relapsing forms of multiple sclerosis to delay the accumulation of physical disability and reduce the frequency of clinical exacerbations.

TYSABRI is generally recommended for patients who have had an inadequate response to, or are unable to tolerate, an alternate MS therapy. Crohn’s Disease (CD): 
•Inducing and maintaining clinical response and remission in adult patients with moderately to severely active Crohn’s disease with evidence of inflammation who have had an inadequate response to, or are unable to tolerate, conventional CD therapies and inhibitors of TNF-α.

Important Limitations: 
•In CD, TYSABRI should not be used in combination with immunosuppressants or inhibitors of TNF-α.

•300 mg infused intravenously over approximately one hour, every four weeks. Do not give as an intravenous push or bolus.
•TYSABRI solution must be administered within 8 hours of preparation.
•Observe patients during the infusion and for one hour after the infusion is complete.
•In CD, discontinue in patients that have not experienced therapeutic benefit by 12 weeks of induction therapy, and in patients that cannot discontinue chronic concomitant steroids within six months of starting therapy.

The most common adverse reactions (incidence  10%) in MS were headache, fatigue, arthralgia, urinary tract infection, lower respiratory tract infection, gastroenteritis, vaginitis, depression, pain in extremity, abdominal discomfort, diarrhea NOS, and rash; and in CD were headache, upper respiratory tract infections, nausea, and fatigue.

•Patients who have or have had PML.
•Patients who have had a hypersensitivity reaction to TYSABRI.

•Progressive Multifocal Leukoencephalopathy (PML): Has occurred in patients who received TYSABRI. Patients who have significantly compromised immune system function should not ordinarily be treated with TYSABRI. Obtain an MRI scan in MS patients prior to initiating TYSABRI. Monitor MS and CD patients and withhold TYSABRI at the first sign or symptom suggestive of PML. Treatment duration, prior immunosuppressant use, and presence of anti-JC virus antibodies are associated with increased risk of PML in TYSABRI-treated patients.
•Hypersensitivity reactions: Serious hypersensitivity reactions (e.g., anaphylaxis) have occurred. Permanently discontinue TYSABRI if such a reaction occurs.
•Immunosuppression/Infections: TYSABRI may increase the risk for certain infections. Monitor patients for development of infections due to increased risk with use of TYSABRI. See package insert for complete information.