Natalizumab: What It Is, How It Works, and Alternatives You Should Know

When you’re living with natalizumab, a monoclonal antibody used to treat relapsing forms of multiple sclerosis by blocking immune cells from entering the brain and spinal cord. It’s known by the brand name Tysabri and is one of the most effective drugs for stopping MS flare-ups. But it’s not without serious risks—especially a rare but deadly brain infection called PML. This isn’t just another medication. Natalizumab works by targeting a specific protein on immune cells, stopping them from crossing the blood-brain barrier. That’s why it cuts relapses by up to 70% in some patients. But that same mechanism leaves the brain vulnerable to viruses that normally stay under control.

That’s why doctors only prescribe it when other treatments have failed—or when someone has aggressive MS. It’s not a first-line drug. And it’s not for everyone. People who’ve had the JC virus, taken other immunosuppressants, or used natalizumab for more than two years face higher PML risk. That’s why blood tests and MRI scans are required every few months. You can’t just take it and forget it. You need to stay on top of monitoring. And if you’ve been on it for a while and aren’t getting better, you might need to switch. Alternatives like fingolimod, an oral medication that traps immune cells in lymph nodes, reducing their ability to attack the nervous system, or ocrelizumab, a newer infusion therapy that targets B-cells and has shown strong long-term results in MS, are often considered. Some patients even move to teriflunomide, a daily pill with fewer infection risks but also lower effectiveness if their disease is milder.

What you’ll find in the posts below isn’t just a list of drug names. It’s real talk about what happens when treatments stop working, how insurance handles these expensive drugs, and why some people switch to alternatives even when they’re working. You’ll see how people manage side effects, what doctors look for when deciding to stop natalizumab, and how cost plays into decisions in places like Mexico where prices are lower. There’s no sugarcoating here—just facts, risks, and practical choices people are actually making.