Understanding TYSABRI (Natalizumab): A Comprehensive Patient Guide

Table of Contents

• What is TYSABRI and What Does It Treat?
• Key Risks and Safety Information
• Dosage and Administration
• Medication Preparation and Infusion Process
• Common Side Effects
• Required Monitoring and Safety Program
• Considerations for Special Populations
• Source Information

What is TYSABRI and What Does It Treat?

TYSABRI (natalizumab) is a prescription medication approved for treating specific autoimmune conditions in adults. It belongs to a class of drugs called integrin receptor antagonists, which work by preventing certain immune cells from entering the brain and spinal cord or the digestive tract, depending on the condition being treated.

The medication is approved for two main conditions. For multiple sclerosis (MS), it treats relapsing forms including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease. For Crohn's disease, it helps induce and maintain clinical response and remission in patients with moderately to severely active disease who haven't responded adequately to conventional therapies or TNF-α inhibitors.

It's crucial to understand that TYSABRI carries significant risks, particularly a rare brain infection called progressive multifocal leukoencephalopathy (PML). Doctors must carefully weigh whether the potential benefits outweigh these risks for each individual patient before starting treatment.

Key Risks and Safety Information

TYSABRI includes a boxed warning, the strongest safety alert from the FDA, regarding progressive multifocal leukoencephalopathy (PML). PML is a rare but serious viral infection of the brain that typically only occurs in people with weakened immune systems and usually leads to death or severe disability.

Three main factors increase PML risk in TYSABRI patients. The presence of anti-JC virus antibodies increases risk significantly, with antibody-positive patients having much higher risk. Longer treatment duration, especially beyond 2 years, increases risk. Prior treatment with immunosuppressants like mitoxantrone, azathioprine, methotrexate, cyclophosphamide, or mycophenolate mofetil also elevates risk.

The estimated incidence of PML varies based on these risk factors. For anti-JCV antibody negative patients, risk remains below 1/10,000 regardless of treatment duration. For antibody-positive patients without prior immunosuppressant use, risk increases from 1/1,000 in the first 24 months to 4/1,000 at 49-72 months. For antibody-positive patients with prior immunosuppressant use, risk ranges from 1/1,000 in the first 24 months to 7/1,000 at 49-72 months.

Other serious risks include herpes infections (encephalitis, meningitis, and acute retinal necrosis), significant liver injury including liver failure requiring transplant, serious hypersensitivity reactions, increased susceptibility to infections, and hematological abnormalities including thrombocytopenia (low platelet count).

Dosage and Administration

TYSABRI is administered as a 300 mg intravenous infusion over one hour every four weeks. The medication must never be given as an intravenous push or bolus injection. This consistent dosing schedule maintains therapeutic levels in the body.

For Crohn's disease patients, specific rules apply regarding treatment duration. If no therapeutic benefit occurs by 12 weeks of induction therapy, TYSABRI should be discontinued. Patients starting while on chronic oral corticosteroids must begin tapering steroids as soon as benefit occurs and must be completely off steroids within six months, otherwise TYSABRI must be stopped.

The infusion process requires careful monitoring. Patients must be observed during all infusions. For the first 12 infusions, patients are observed for one hour after completion. After 12 uneventful infusions, observation time for subsequent infusions is based on clinical judgment.

Medication Preparation and Infusion Process

TYSABRI requires specific preparation procedures to ensure safety and effectiveness. Each vial contains 300 mg/15 mL (20 mg/mL) of medication. Healthcare providers use sterile technique to withdraw 15 mL from the vial and inject it into 100 mL of 0.9% Sodium Chloride Injection.

The diluted solution must be gently inverted to mix completely—never shaken. The final concentration becomes 2.6 mg/mL. The prepared solution must be used immediately or refrigerated at 2°C to 8°C and used within 48 hours. Frozen medication must never be used.

During administration, the solution is infused over approximately one hour at a rate of about 5 mg per minute. After completion, the IV line is flushed with 0.9% Sodium Chloride Injection. Other medications should never be injected into the infusion set or mixed with TYSABRI.

Common Side Effects

Clinical trials revealed side effects that affected at least 10% of patients. For multiple sclerosis patients, the most common adverse reactions included:

• Headache
• Fatigue
• Joint pain (arthralgia)
• Urinary tract infections
• Lower respiratory tract infections
• Gastroenteritis
• Vaginitis
• Depression
• Pain in extremities
• Abdominal discomfort
• Diarrhea
• Rash

For Crohn's disease patients, the most common reactions were headache, upper respiratory tract infections, nausea, and fatigue. These side effects varied in frequency and severity among patients.

Required Monitoring and Safety Program

Because of the PML risk, TYSABRI is only available through the restricted TOUCH® Prescribing Program. This program requires specific commitments from prescribers, patients, and healthcare facilities to ensure safe use.

Prescribers must complete specialized certification and comply with ongoing monitoring requirements. They must evaluate patients at three months after the first infusion, six months after the first infusion, and every six months thereafter. They must also monitor patients for at least six months after discontinuing TYSABRI.

Patients must enroll in the program, read the Medication Guide, understand the risks, and complete enrollment forms. Regular anti-JCV antibody testing is recommended, particularly since seroconversion (changing from negative to positive) occurs in 3-8% of MS patients annually.

MRI monitoring is essential. MS patients should have an MRI scan before starting therapy to help differentiate future MS symptoms from PML. For PML diagnosis, evaluations include gadolinium-enhanced MRI brain scans and cerebrospinal fluid analysis for JC viral DNA when indicated.

Considerations for Special Populations

Pregnancy requires special consideration with TYSABRI. The medication can cause fetal harm based on its mechanism of action and animal data. Women of childbearing potential should use effective contraception during treatment and discuss pregnancy planning with their healthcare provider.

For neonates exposed to TYSABRI in utero, healthcare providers should obtain complete blood counts to check for possible thrombocytopenia and anemia. These blood abnormalities have been reported in some exposed newborns.

Elderly patients may be at increased risk for infections due to age-related immune system changes. Pediatric use has not been established, and the medication is not approved for children. Breastfeeding decisions should be made carefully after discussing risks and benefits with healthcare providers.

Source Information

Original Article Title: TYSABRI- natalizumab injection
Manufacturer: Biogen Inc.
Initial U.S. Approval: 2004
Latest Revision: March 2025

This patient-friendly article is based on peer-reviewed research and the official prescribing information for TYSABRI. Always consult with your healthcare provider for personal medical advice regarding your specific condition and treatment options.